Как устроена беспроводная зарядка для телефона

Как устроена беспроводная зарядка

В основе работы любого беспроводного зарядного устройства лежит такое явление, как электромагнитная индукция.

Электрический ток, протекая по проводнику, создает вокруг него электромагнитное поле. Если поместить в это поле другой проводник, то в нем также возникает электрический ток.

Эту зависимость между электричеством и магнетизмом ученые открыли еще в 19 веке, и с тех пор различные устройства, основанные на этом явлении, существенно упростили жизнь для всего человечества.

Беспроводная зарядка по принципу работы схожа с простейшим трансформатором и представляет собой индукционную катушку-передатчик на плате, помещенную в пластиковый корпус. Вторая такая катушка-приемник находится внутри смартфона. На катушку-передатчик подается переменный ток, благодаря чему возникает магнитное поле, которое воздействует на катушку-приемник. Она трансформирует (выпрямляет) переменный ток в постоянный, который впоследствии и восполняет заряд аккумулятора.

Кроме наведения электрического тока, при передаче энергии между смартфоном и зарядным устройством также происходит и обмен данными. Беспроводная зарядка способна принимать и передавать до 2 КБ таких данных в секунду. Немного, но этого достаточно, чтобы устройства обменивались информацией о заряде аккумулятора, уровне мощности, совместимости и правильном расположении смартфона на площадке.

Например, если вы положите на зарядное устройство мощностью 15 Вт смартфон, не поддерживающий быструю зарядку, то устройство определит несоответствие и снизит мощность до минимальных 5 вт.

Что такое стандарт QI

На сегодняшний день большинство беспроводных зарядных устройств объединены в единый стандарт QI. Так как технически возможно производить зарядные устройства с разными характеристиками, производители решили договориться о едином решении, которое бы стало универсальным и позволяло использовать зарядные устройства одного стандарта для всех смартфонов, поддерживающих данную технологию.

В качестве еще одного яркого примера стремления производителей к подобной универсальности можно привести стандарты microUSB и USB Type-C.

Преимущества

Одним их главных преимуществ беспроводных зарядных устройств является несомненное удобство установки смартфона на зарядку. Можно забыть о мучительных попытках попасть коннектором в разъем при плохом освещении. Беспроводной зарядкой легко пользоваться даже в темноте. Достаточно просто положить телефон на специальную площадку, и процесс зарядки начнется автоматически.

То же самое касается и вождения автомобиля. Чтобы поставить смартфон на зарядку, больше не нужно отвлекаться от дороги и путаться в проводах.

Многим пожилым людям, а также людям с ослабленным зрением это преимущество существенно облегчает жизнь.

Кроме этого, сопряжение смартфона с беспроводной зарядкой не требует такого бережливого обращения, как в случае с любыми другими разъемами, большинство из которых рассчитано примерно на 1500 циклов «подключения-отключения».

Недостатки

Конечно, и эта инновационная технология не свободна от недостатков. Из наиболее существенных стоит выделить:

В случае кабельного подключения с этим особых трудностей не возникает, кроме «привязки» к розетке. Вы ставите смартфон на зарядку и продолжаете пользоваться девайсом. С беспроводным устройством это может стать для вас проблемой, ведь во время зарядки телефон должен лежать на платформе неподвижно.

Выйти из этого положения лучше других, пожалуй, пока что удалось только компании Apple.

Беспроводная зарядка Magsafe имеет магнитную поверхность (в корпусе iPhone установлено специальное металлическое кольцо) и провод, который вращается на 360°, что позволяет заряжать ваш смартфон даже во время звонков.

Теперь вы знаете, как работает беспроводная зарядка для телефона, и эта информация обязательно вам пригодится. Ведь вполне вероятно, что в скором времени беспроводные технологии ворвутся и в другие сферы нашей жизни, постепенно освобождая человечество от «кабельной зависимости».

Это тоже интересно:

Если вы пользовались беспроводным зарядным устройством, вы знаете: 

Но если отложить все неудобства — конечно, выглядит волшебно. Разберёмся, как это устроено с точки зрения физики.  

Физика и магнитное поле

Если сильно упростить, то любая беспроводная зарядка основана на эффекте, который мы знаем из уроков физики:

когда по проводу идёт ток, вокруг провода образуется магнитное поле. 

Выглядит это примерно так:

Но у магнитного поля есть и обратное свойство: если его точно так же пустить вдоль другого провода, то в этом проводе появится ток:

Получается, что если мы сформируем такое же магнитное поле вокруг провода, то сможем подключить этот провод к батарее, чтобы она заряжалась. Это можно сделать, например, так:

Чем ближе провода друг к другу — тем лучше.

Но чтобы в новом проводе тока хватало для заряда батареи, у нас должно быть достаточно сильное магнитное поле. Самый простой способ получить поле посильнее — скрутить много витков провода по спирали.

Скручиваем провод

Если мы возьмём длинный провод и скрутим его по спирали, то у нас получится катушка,  магнитное поле будет сильнее и будет распределяться так:

Если мы пустим по этой спирали ток, а сверху положим такую же спираль, то в ней появится такой же ток, только на 20–25% слабее. Потери связаны с преобразованием магнитного поля в электричество, поэтому обычно на спираль подают ток побольше, чтобы на выходе получить нужные значения.

Для беспроводной зарядки одну такую спираль подключают через преобразователь к розетке, а другую встраивают в телефон. Когда мы положим такой телефон на площадку, под которой будет катушка под напряжением, то спираль телефона уловит это магнитное поле, преобразует его в электричество и будет заряжать батарею.

Но не всё так просто

Чтобы беспроводная зарядка работала эффективно, катушки зарядки и телефона должны быть как можно ближе друг к другу. Идеально, если их центры совпадут — тогда потери будут минимальные. Но мы часто видим, как телефоны просто кладут на любое место площадки, а зарядка всё равно идёт как нужно. 

Чтобы это было возможно, производители делают несколько катушек на площадке. Например, можно расположить несколько катушек рядом друг с другом, а сверху в промежутки положить ещё несколько. Тогда телефон почти всегда будет лежать над одной из катушек и будет заряжаться.

Чтобы зарядка понимала, какую катушку нужно использовать, она по очереди даёт ток на каждую и таким образом определяет, к какой катушке телефон лежит ближе всего.

Ещё зарядки отличаются по мощности — например, есть зарядки на 5, 10 и 20 ватт. Чтобы зарядка понимала, на какую мощность рассчитан ваш телефон и вообще подходил ли эта зарядка к телефону, она с помощью того же магнитного поля обменивается с телефоном данными. Если всё в порядке — заряд идёт, если нет — то всё отключается или зарядка идёт на минимальной мощности.

Стандарты беспроводных зарядок

Qi. Самый популярный стандарт, который поддерживают почти все телефоны. Его минус — нужно очень точно расположить телефон над катушкой, чтобы всё работало как нужно. Именно для этого делают несколько катушек в зарядке. Максимальное расстояние для заряда — 4 сантиметра, а максимальная мощность — 120 ватт.

PMA. Использует тот же принцип, что и Qi, но работает на другой частоте тока в катушке. Его поддерживают меньше телефонов, но есть и такие модели, которые работают с обоими стандартами. Ещё PMA-зарядки встраивает Старбакс в столы у себя в кофейнях.

Есть и другие стандарты для беспроводной зарядки устройств, но в телефонах они не применяются и рассчитаны на промышленные устройства, электромобили и остальную технику.

Паранойя

Вызывают ли беспроводные катушки рак, импотенцию, слабоумие? Не более, чем любая проводка в вашем доме. Беспроводная зарядка — это просто два мотка проволоки под напряжением.

Можно ли через беспроводную зарядку считать данные телефона? Нет, но можно — через беспроводную технологию NFC, если ваш телефон готов этими данными поделиться. 

Можно ли с помощью беспроводной зарядки размагнитить банковскую карту? Если карта с магнитной полосой и вы положите ее между зарядной станцией и телефоном надолго, то магнитная полоса может повредиться. Карта с чипом — нет. 

Можно ли приготовить или разогреть на беспроводной зарядке еду? Можно, если ваша еда — свёрнутая в спираль медная проволока, а у зарядной станции будет мощность в 100—200 раз выше, чем у современных. Проволока нагреется, её можно будет съесть. (Это шутка, не ешьте медную проволоку).

Сейчас все чаще и чаще слышу про беспроводную зарядку. Четыре месяца назад, когда искал себе новую машину, видел Киа «Спортедж» со встроенной такой зарядкой. Еще подумал, вот на кого это рассчитано, на единиц? Казалось, что для этого надо иметь какую то крутую модель телефона или какое то дорогое оборудование. Но оказывается и мой телефон средней стоимости поддерживает эту технологию. Задумался, я же совсем не знаю принципов, как это работает. Мне казалось, что эта технология еще достаточно «далеко» от обывателя, а оно уже вот рядом и совсем доступно.

Давайте разберемся чуть подробнее …

Оказывается, принцип работы беспроводного зарядного устройства очень прост — достаточно поместить гаджет на специальную панель, чтобы он зарядился. В основе аксессуара лежит принцип работы индукционной катушки.

Беспроводные зубные щетки длительное время уже используют беспроводную зарядку. Технологию традиционно сопровождали проблемы низкой эффективности и медленной зарядки, но они были не критическим недостатком для зубной щетки или электрической бритвы, которые вы используете только в течение нескольких минут каждый день. Использование индуктивной зарядки является более безопасным, с той точки зрения, что нету провода, и он не замкнет, и вы случайно не дотронетесь мокрыми руками к участкам с плохой изоляцией.

Такой способ передачи энергии становится очень популярной в последнее время. В 2015 году всемирно популярный бренд начал продавать мебель, в которую будет встроен модуль беспроводной зарядки. Сегодня все флагманские модели смартфонов поддерживают Qi.

Ожидается, что в скором времени трансмиттеры или, другими словами, модули можно будет найти в аэропортах, ресторанах, кинотеатрах, фастфудах, торговых центрах, что позволит осуществлять зарядку телефонов и планшетов в любое время. На самом деле это облегчит жизнь юзерам мобильных гаджетов. Мы входим в новую эру, где совсем необязательно носить с собой повсюду проводные зарядные устройства для всех девайсов, которыми мы пользуемся.

Стандарт беспроводного питания называется Qi. В русской транскрипции слово произносится как «Ци». Такое имя стандарт носит в честь термина восточной философии и означает поток энергии. Он разработан Консорциумом беспроводной электромагнитной энергии WPC. Эта организация объединяет мировых производителей электроники и ставит перед собой важную задачу — стандартизировать процесс зарядки гаджетов индукционным методом. В ближайшем будущем все девайсы можно будет заряжать без подключения к сети. Это невероятно удобно. Каждый из нас хотя бы раз сталкивался с ситуацией, когда разряжается смартфон. Приходится в срочном порядке искать выход. В скором времени модули беспроводной зарядки появятся во всех общественных местах, а также дома у каждого юзера.

В домашних условиях можно просто расположить модуль в удобном месте, и он никогда не потеряется, в отличие от проводной «зарядки». Достаточно просто поместить на него гаджет, немного подождать, пока пополнится ёмкость аккумулятора. Принцип работы беспроводной «зарядки» основан на свойствах индукционной катушки передавать электрический ток. В школьном курсе физики нас учили, что при подключении индукционной катушки к источнику питания в ней возникает магнитное поле перпендикулярно виткам катушки. Таким образом, если расположить две катушки в радиусе действия магнитного поля и при этом подключить одну из них к источнику питания, то во второй катушке появится напряжение. При этом важно учитывать тот факт, что две индукционные катушки ни в коем случае не должны соприкасаться между собой. Такой простой принцип положен в работу беспроводных зарядных устройств, поддерживающих технологию Qi.

Существует две разновидности стандарта Qi. Первая предполагает зарядку при низкой мощности — 5 ватт, а вторая — при высокой мощности — 120 ватт. Qi высокой мощности сейчас не выпускается производителями в силу объективных факторов. С помощью Qi на 120 ватт можно выполнить зарядку ноутбука. Qi на 5 ватт используют для пополнения ёмкости аккумулятора планшетных компьютеров и телефонов. Следует отметить, что для планшета и смартфона необходима различная сила тока. Беспроводное зарядное устройство для телефона создаёт силу тока в 1 ампер, а для планшетного компьютера — 2 ампера. При выборе аксессуара обязательно обращайте внимание на такие характеристики.

Современное беспроводное зарядное устройство состоит из двух компонентов. Один из них встроен непосредственно в гаджет, который поддерживает Qi и называется ресивером беспроводной зарядки. По сути, он является приёмником, который проводит электрический ток к аккумулятору. Второй компонент называют трансмиттером. Если подразумевается покупка беспроводной «зарядки», речь идёт именно о трансмиттере. Они бывают самых разных форм и размеров. В основном распространены круглые и прямоугольные передатчики.

Чтобы лучше понять, как работает беспроводная зарядка, следует учесть, что магнитное поле способно передавать не только электрический ток, но и данные о байтах и битах, что учли разработчики стандарта Qi. Взаимодействие между катушками будет возникать только в тот момент, когда гаджет со встроенным трансмиттером будет находиться поблизости от передатчика. Если аксессуар для зарядки гаджета будет функционировать в фоновом режиме, то посылаемый каждые 0,4 секунды передатчиком импульс не будет изменять напряжение в катушке, встроенной в трансмиттер. Можно сделать вывод, что современный аксессуар умеет распознавать, в каком режиме функционировать. Как только поблизости на расстоянии нескольких сантиметров окажется смартфон, напряжение в индукционной катушке резко снизится, и устройство перейдёт в режим активной работы. Как только аккумулятор смартфона будет заряжен, соответствующий сигнал переведёт зарядное устройство в фоновый режим. Можно сделать вывод, что современные беспроводные аксессуары для пополнения ёмкости батареи являются энергоэффективными.

Еще больше графиков и формул смотрите ВОТ ТУТ.

Некоторые пользователи ошибочно полагают, что функция беспроводной зарядки Qi может нанести вред здоровью. Дело в том, что магнитное излучение не является ионизирующим. По своему влиянию на организм оно похоже на сигнал мобильной связи, сигнал Wi-Fi, радиосигнал. При этом сигнал мобильной сети, который поступает с вышки, является более сильным и имеет непрерывный характер, в то время, как электромагнитное излучение пропадает сразу после зарядки батареи смартфона. Мощность беспроводных зарядных устройств составляет 5 ватт. Её недостаточно чтобы оказать воздействие на человеческий организм. О негативном воздействии можно говорить лишь в том случае, когда мощность таких девайсов будет равняться 120 ваттам. Но подобные модели не выпускаются в промышленных масштабах. Этим объясняется отсутствие беспроводных зарядных устройств для ноутбуков. Важно знать, что технология беспроводного заряда аккумулятора давно используется во многих моделях электробритв и электрических зубных щёток, что в очередной раз доказывает её безопасность.

Перспективы

Данная индуктивная зарядка может быть удобна, но малый радиус действия является проблемой. Это разительно уменьшает удобство пользования данной технологией Изменится ли это? Может быть. Было проведено много исследований потенциала беспроводной зарядки и в различных технологиях были успехи в радиусе действия. Лазеры, микроволновые печи и более мощные варианты индуктивной зарядки смогли достичь больших расстояниях передачи. Недостатки препятствуют распространенное это слишком мощное излучение выше сказанных технологий. Можете обжечься или еще чего хуже. Трудно сказать, кто возьмет пальму первенства на этом рынке. Первым кандидатом, является Apple, потому что компания запатентовала устройство, которое может якобы заряжать на расстоянии до одного метра. Беспроводной Консорциум питания также постоянно ищет лучшие варианты. А тут еще Intel, которая недавно объявила, что она работает над интегрированной технологией магнитных устройств, которые будут помещены в ноутбук и раздавать питание на близлежащие смартфоны и периферийные устройства.

[источники]
источники
http://www.russianelectronics.ru/leader-r/review/doc/70732/
http://protabletpc.ru/accessories/besprovodnoe-zaryadnoe-ustrojstvo.html
http://texhepl.ru/chto-takoe-besprovodnaja-zarjadka-i-kak-ona-rabotaet/

Еще несколько интересных технологий: вот например Прозрачный бетон, а вот Гигантские аудиокассеты из Японии и Прозрачный алюминий. А вы видели когда нибудь Лазерную бритву или Компьютер в аквариуме?

В наши дни беспроводная зарядка стала довольно распространенной. От столов в кофейнях до приборных панелей автомобилей и даже ковриков для мыши — вы найдете зарядные устройства практически везде. А если у вас есть совместимое устройство, то все, что вам нужно сделать, это поместить его в отмеченное место, и магическим образом начнется зарядка. Я уже давно начал ей пользоваться, и для меня при выборе нового телефона обязательное условие, чтобы в нем была беспроводная зарядка. Правда, как показывает практика, несмотря на ее популяризацию и распространение, многие еще не знакомы с этой технологий. Сейчас попробуем рассказать о ней более подробно.

Как работает беспроводная зарядка

Как бы удобно это ни было, не все беспроводные зарядные устройства устроены одинаково. И хотя, несомненно, заманчиво избавиться от проводов навсегда, есть некоторые предостережения, связанные с этой технологией.

Беспроводная зарядка основана на довольно простом принципе электромагнитной индукции. В двух словах это представляет из себя пропускание переменного тока через медную катушку, которая создает магнитное поле в непосредственной близости от себя. Если вы поместите другую катушку в зону досягаемости поля, то принимающая катушка будет ”вырабатывать” ток.

Спор на тему: почему нужно пользоваться беспроводными зарядками и почему лучше этого не делать

В контексте беспроводной зарядки первичная катушка находится внутри зарядного устройства и получает питание от розетки. Вторичная катушка находится внутри вашего смартфона и получает индуцированный ток полностью без проводов.

Именно поэтому устройства с беспроводной зарядкой называются именно беспроводными, хотя формально провода все же есть (от розетки до зарядной станции). Тут есть одно важное ограничение — беспроводная зарядка работает только через стекло или пластик. Алюминиевый корпус экранирует передачу и зарядка без проводов невозможна. Исключением является Google Pixel 5, но там создатели пошли на хитрость. Они вырезали в задней стенке отверстие, в которое вставили катушку, и нанесли на него полимер. Так кажется, что стенка полностью алюминиевая, но это ложное ощущение.

Все ли беспроводные зарядки одинаковые

Гаджеты и зарядные устройства для них должны взаимодействовать друг с другом, чтобы определять скорость зарядки и другие параметры. В далеком прошлом существовало несколько конкурирующих стандартов беспроводной зарядки. Однако на сегодняшний день доминирующим стал стандарт Qi (читается ”чи”), разработанный консорциумом Wireless Power Consortium. Большинство беспроводных зарядных устройств поддерживают стандарт Qi, за вычетом нескольких исключений, о которых мы поговорим ниже.

Общий стандарт выгоден, потому что покупатель не должен задумываться о совместимости. Достаточно того, что в принципе есть поддержка беспроводной зарядки. Так получается отвязаться от конкретных брендов. Это как USB в мире зарядок — единый стандарт.

Зарядка QI

Qi все делают по определенному стандарту, который включает в себя рекомендации по многочисленным аспектам процесса зарядки, таким как зона зарядки, пределы температуры и обнаружение объектов. Последнее особенно важно, потому что если вы случайно оставите металлические предметы, такие как монеты, в зоне поля, они могут быстро нагреться. Стандарт помогает предотвратить это, делая аксессуар более безопасным. Зарядные устройства будут генерировать поле только при обнаружении Qi-совместимого гаджета.

Впрочем, некоторые производители предлагают свои стандарты беспроводной зарядки, чтобы выйти за границы ограничения Qi по мощности. OnePlus, например, предлагает беспроводную Warp Charge 50. Она полностью восстанавливает батарею OnePlus 9 Pro менее чем за 40 минут. AirVooc от Oppo еще больше ускоряет этот процесс, предлагая 65 Вт. Одна общая черта этих реализаций заключается в том, что они требуют использования специального беспроводного зарядного устройства. Впрочем, с обычными Qi-зарядками они тоже совместимы, но скорость будет более низкой.

Что делать, если не заряжаются беспроводные наушники.

Чем зарядка MagSafe отличается от остальных

Хотя решение Apple для быстрой беспроводной зарядки MagSafe может показаться проприетарным продуктом, на самом деле это не так. Зарядная шайба MagSafe просто содержит кольцо магнитов, окружающих обычную катушку стандарта Qi. Все, что оно делает, это упрощает совмещение катушек для более высокой скорости зарядки. В итоге мощность зарядки получается максимальной для стандарта — 15 Вт.

Но есть у Apple и действительно проприетарная зарядка. Она используется для Apple Watch. А AirPods могут заряжаться от обычной Qi, как и Samsung Galaxy Watch 4. То есть, как видим, размер корпуса и уменьшение размера катушки не является тем, что помешает пользоваться беспроводной зарядкой. Многие полагают, что в Apple Watch может использоваться программное ограничение на использование зарядок.

С точки зрения удобства беспроводные зарядные устройства почти всегда выходят на первое место. Однако часто бывает наоборот, когда вы смотрите на такие параметры, как скорость, эффективность и тепловыделение.

Почему телефон сильно греется. Вот причины.

Как быстрее всего зарядить телефон

Мы уже говорили, что стандарт Qi допускает максимум 15 Вт. Однако многие производители смартфонов перешли на 33 Вт, 65 Вт и даже 160 Вт для проводной зарядки. Это означает, что беспроводная зарядка гораздо хуже подходит для быстрого пополнения аккумулятора.

Что касается эффективности, то исследования показали, что беспроводная зарядка потребляет примерно на 50% больше энергии от розетки по сравнению с подключением телефона проводом. Вам просто придется брать с собой более мощный и громоздки блок питания. А если вам интересно, куда уходит энергия, то она просто теряется в виде тепла. И это еще одна серьезная проблема, с которой приходится сталкиваться производителям.

Чрезмерное тепло во время зарядки — это плохо, потому что оно может сократить срок службы аккумулятора телефона. Для этого крайне важно, чтобы смартфоны и беспроводные зарядные устройства имели встроенные механизмы защиты от перегрева. Многие производители, такие как Samsung и OnePlus, даже добавляют в свои зарядные устройства охлаждающий вентилятор. Однако он может быть довольно шумным, поэтому проводное решение в любом случае может быть предпочтительнее.

В общем, именно из-за этих недостатков беспроводная зарядка еще не нашла применение в других отраслях, таких как электромобили, где токи существенно выше. Когда найдет, мы обязательно расскажем об этом в нашем новостном Telegram-канале.

A еще у нас есть свой Яндекс Дзен. В нем публикуется много материалов, которых нет на сайте.

Зарядка гаджетов от телефона

Обратная беспроводная зарядка — относительно новая функция, предлагаемая в основном на топовых флагманских смартфонах, таких как Google Pixel и Samsung серии Galaxy S. Принцип электромагнитной индукции остается прежним, за исключением того, что вместо этого смартфон, который до этого сам заряжался от специальной станции, превращается в первичную катушку. Проще говоря, телефон использует энергию собственной батареи для создания магнитного поля. Затем на поверхность телефона можно поместить другие устройства, чтобы начать беспроводную зарядку привычным нам способом.

Обратная беспроводная зарядка позволяет заряжать дополнительные устройства, такие как наушники, часы и даже целые телефоны, на задней панели вашего смартфона.

Можно ли зарядить телефон от другого телефона

Имейте в виду, что те же недостатки, что мы обсуждали выше, есть и здесь. Обратная беспроводная зарядка довольно неэффективна, поэтому вы разряжаете значительную часть аккумулятора своего смартфона, чтобы зарядить часы или наушники. А значит, способ скорее подойдет на случай экстренного. Поэтому многие производители предлагают использовать эту функцию, когда смартфон подключен к сети. Это фактически устраняет необходимость носить с собой отдельную зарядку для небольших устройств.

Точно так же технически возможно зарядить другой смартфон с помощью обратной беспроводной зарядки, но низкая эффективность и вероятность перегрева делают его полезным только в крайних случаях. Еще одно предостережение, которое следует учитывать, заключается в том, что скорость обратной зарядки часто весьма ограничена — в некоторых случаях она всего 5 Вт.

Это все, что надо знать о беспроводной зарядке. Расскажите в Telegram-чате, что вы думаете о ней и готовы ли ей пользоваться?

Inductive charging (also known as wireless charging or cordless charging) is a type of wireless power transfer. It uses electromagnetic induction to provide electricity to portable devices. Inductive charging is also used in vehicles, power tools, electric toothbrushes, and medical devices. The portable equipment can be placed near a charging station or inductive pad without needing to be precisely aligned or make electrical contact with a dock or plug.

Inductive charging is named so because it transfers energy through inductive coupling. First, alternating current passes through an induction coil in the charging station or pad. The moving electric charge creates a magnetic field, which fluctuates in strength because the electric current’s amplitude is fluctuating. This changing magnetic field creates an alternating electric current in the portable device’s induction coil, which in turn passes through a rectifier to convert it to direct current. Finally, the direct current charges a battery or provides operating power.^[1][2]

Greater distances between sender and receiver coils can be achieved when the inductive charging system uses resonant inductive coupling, where a capacitor is added to each induction coil to create two LC circuits with a specific resonance frequency. The frequency of the alternating current is matched with the resonance frequency, and the frequency is chosen depending on the distance desired for peak efficiency.^[1] Recent improvements to this resonant system include using a movable transmission coil (i.e., mounted on an elevating platform or arm) and the use of other materials for the receiver coil such as silver-plated copper or sometimes aluminum to minimize weight and decrease resistance due to the skin effect.

History[edit]

Induction power transfer was first used in 1894 when M. Hutin and M. Le-Blanc proposed an apparatus and method to power an electric vehicle.^[3] However, combustion engines proved more popular, and this technology was forgotten for a time.^[2]

In 1972, Professor Don Otto of the University of Auckland proposed a vehicle powered by induction using transmitters in the road and a receiver on the vehicle.^[2] In 1977, John E. Trombly was awarded a patent for an «Electromagnetically coupled battery charger.» The patent describes an application to charge headlamp batteries for miners (US 4031449). The first application of inductive charging used in the United States was performed by J.G. Bolger, F.A. Kirsten, and S. Ng in 1978. They made an electric vehicle powered with a system at 180 Hz with 20 kW.^[2] In California in the 1980s, a bus was produced, which was powered by inductive charging, and similar work was being done in France and Germany around this time.^[2]

In 2006, MIT began using^{[clarification needed]} resonant coupling. They were able to transmit a large amount of power without radiation over a few meters. This proved to be better for commercial needs, and it was a major step for inductive charging.^{[2][failed verification]}

The Wireless Power Consortium (WPC) was established in 2008, and in 2010 they established the Qi standard. In 2012, the Alliance for Wireless Power (A4WP) and the Power Matter Alliance (PMA) were founded. Japan established Broadband Wireless Forum (BWF) in 2009, and they established the Wireless Power Consortium for Practical Applications (WiPoT) in 2013. The Energy Harvesting Consortium (EHC) was also founded in Japan in 2010. Korea established the Korean Wireless Power Forum (KWPF) in 2011.^[2] The purpose of these organizations is to create standards for inductive charging. In 2018, The Qi Wireless Standard was adopted for use in military equipment in North Korea, Russia, and Germany

Application areas[edit]

Applications of inductive charging can be divided into two broad categories: Low power and high power:

• Low power applications are generally supportive of small consumer electronic devices such as cell phones, handheld devices, some computers, and similar devices which normally charge at power levels below 100 watts. Typically, the AC utility frequency of 50 or 60 Hertz is used.^[4]
• High power inductive charging generally refers to inductive charging of batteries at power levels above 1 kilowatt. The most prominent application area for high power inductive charging is in support of electric vehicles, where inductive charging provides an automated and cordless alternative to plug-in charging. Power levels of these devices can range from approximately 1 kilowatt to 300 kilowatts or higher. All high-power inductive charging systems use resonated primary and secondary coils. These systems work in the long wave range with frequencies up to 130 kHz. The use of short wave frequencies can enhance the system’s efficiency and size^[5] but would eventually transmit the signal worldwide. High powers raise the concern of electromagnetic compatibility and radio frequency interference.

Advantages[edit]

• Protected connections – No corrosion when the electronics are enclosed, away from water or oxygen in the atmosphere. Less risk of electrical faults such as short circuits due to insulation failure, especially where connections are made or broken frequently.^[6]
• Low infection risk – For embedded medical devices, the transmission of power via a magnetic field passing through the skin avoids the infection risks associated with wires penetrating the skin.^[7]
• Durability – Without the need to constantly plug and unplug the device, there is significantly less wear and tear on the socket of the device and the attaching cable.^[6]
• Increased convenience and aesthetic quality – No need for cables.
• Automated high power inductive charging of electric vehicles allows for more frequent charging events and consequently an extension of driving range.
• Inductive charging systems can be operated automatically without dependence on people to plug and unplug. This results in higher reliability.
• Automatic operation of inductive charging in roads theoretically allows vehicles to run indefinitely.^[8]

Disadvantages[edit]

The following disadvantages have been noted for low-power (i.e., less than 100 watts) inductive charging devices, and may not apply to high-power (i.e., greater than 5 kilowatts) electric vehicle inductive charging systems.^{[citation needed]}

• Slower charging – Due to the lower efficiency, devices take 15 percent longer to charge when supplied power is the same amount.^[9]
• More expensive – Inductive charging also requires drive electronics and coils in both device and charger, increasing the complexity and cost of manufacturing.^[10][11]
• Inconvenience – When a mobile device is connected to a cable, it can be moved around (albeit in a limited range) and operated while charging. In most implementations of inductive charging, the mobile device must be left on a pad to charge, and thus can’t be moved around or easily operated while charging. With some standards, charging can be maintained at a distance, but only with nothing present between the transmitter and receiver.^[6]
• Compatible standards – Not all devices are compatible with different inductive chargers. However, some devices have started to support multiple standards.

Inefficiency has other costs besides longer charge times. Inductive chargers produce more waste heat than wired chargers, which may negatively impact battery longevity.^{[13][better source needed]} An amateur 2020 analysis of energy use conducted with a Pixel 4 found that a wired charge from 0 to 100 percent consumed 14.26 Wh (watt-hours), while a wireless charging stand used 19.8 Wh, an increase of 39%. Using a generic brand wireless charging pad and mis-aligning the phone produced consumption up to 25.62 Wh, or an 80% increase. The analysis noted that while this is not likely to be noticeable to individuals, it has negative implications for greater adoption of smartphone wireless charging.^[14]

Newer approaches reduce transfer losses through the use of ultra thin coils, higher frequencies, and optimized drive electronics. This results in more efficient and compact chargers and receivers, facilitating their integration into mobile devices or batteries with minimal changes required.^[15][16] These technologies provide charging times comparable to wired approaches, and they are rapidly finding their way into mobile devices.

Safety[edit]

An increase in high-power inductive charging devices has led to researchers looking into the safety factor of the electromagnetic fields (EMF) put off by larger inductor coils. With the recent interest in the expansion of high power inductive charging with electric cars, an increase in health and safety concerns has arisen. To provide a larger distance of coverage you would in return need a larger coil for your inductor. An electric car with this size conductor would need about 300 kW from a 400 V battery to emit enough charge.^{[clarification needed]} This much exposure to the skin of a human could prove harmful if not met within the right conditions. Exposure limits can be satisfied even when the transmitter coil is very close to the body.^[17]

Testing has been done on how organs can be affected by these fields when put under low levels of frequency from these fields. When exposed to various levels of frequencies you can experience dizziness, light flashes, or tingling through nerves. At higher ranges, you can experience heating or even burning of the skin. Most people experience low EMF in everyday life. The most common place to experience these frequencies is with a wireless charger, usually on a nightstand located near the head.^[18]

Standards[edit]

Standards refer to the different set operating systems with which devices are compatible. There are two main standards: Qi and PMA.^[12] The two standards operate very similarly, but they use different transmission frequencies and connection protocols.^[12] Because of this, devices compatible with one standard are not necessarily compatible with the other standard. However, there are devices compatible with both standards.

• Magne Charge, a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles (BEV) formerly made by General Motors.
• The emerging SAE J2954 standard allows inductive car charging over a pad, with power delivery up to 11 kW.^[19]
• Qi, an interface standard developed by the Wireless Power Consortium for inductive electrical power transfer. At the time of July 2017, it is the most popular standard in the world, with more than 200 million devices supporting this interface.
• AirFuel Alliance:
  • In January 2012, the IEEE announced the initiation of the Power Matters Alliance (PMA) under the IEEE Standards Association (IEEE-SA) Industry Connections. The alliance is formed to publish a set of standards for inductive power that are safe and energy-efficient, and have smart power management. The PMA will also focus on the creation of an inductive power ecosystem^[20]
  • Rezence was an interface standard developed by the Alliance for Wireless Power (A4WP).
  • A4WP and PMA merged into the AirFuel Alliance in 2015.^[21]

Electronic devices[edit]

Many manufacturers of smartphones have started adding this technology into their devices, the majority adopting the Qi wireless charging standard. Major manufacturers such as Apple and Samsung produce many models of their phones in high volume with Qi capabilities. The popularity of the Qi standard has driven other manufacturers to adopt this as their own standard.^[22] Smartphones have become the driving force of this technology entering consumers’ homes, where many household technologies have been developed to utilize this technology.

Samsung and other companies have begun exploring the idea of «surface charging», building an inductive charging station into an entire surface such as a desk or table.^[22] Contrarily, Apple and Anker are pushing a dock-based charging platform. This includes charging pads and disks that have a much smaller footprint. These are geared for consumers who wish to have smaller chargers that would be located in common areas and blend in with the current décor of their home.^[22] Due to the adoption of the Qi standard of wireless charging, any of these chargers will work with any phone as long as it is Qi capable.^[22]

Another development is reverse wireless charging, which allows a mobile phone to wirelessly discharge its own battery into another device.^[23]

Examples[edit]

• Oral-B rechargeable toothbrushes by the Braun company have used inductive charging since the early 1990s.
• At the Consumer Electronics Show (CES) in January 2007, Visteon unveiled its inductive charging system for in-vehicle use that could charge only specially made cell phones to MP3 players with compatible receivers.^[24]
• April 28, 2009: An Energizer inductive charging station for the Wii remote was reported on IGN.^[25]
• At CES in January 2009, Palm, Inc. announced its new Pre smartphone would be available with an optional inductive charger accessory, the «Touchstone». The charger came with a required special backplate that became standard on the subsequent Pre Plus model announced at CES 2010. This was also featured on later Pixi, Pixi Plus, and Veer 4G smartphones. Upon launch in 2011, the ill-fated HP Touchpad tablet (after HP’s acquisition of Palm Inc.) had a built in touchstone coil that doubled as an antenna for its NFC-like Touch to Share feature.^[15][26][27]
• March 24, 2013: Samsung launched the Galaxy S3, which supports an optionally retrofittable back cover accessory, included in their separate “Wireless Charging Kit”.
• Nokia announced on September 5, 2012, the Lumia 920 and Lumia 820, which supports respectively integrate inductive charging and inductive charging with an accessory back.
• March 15, 2013: Samsung launched the Galaxy S4, which supports inductive charging with an accessory back cover.
• July 26, 2013: Google and ASUS launched the Nexus 7 2013 Edition with integrated inductive charging.
• September 9, 2014: Apple announced Apple Watch (released on April 24, 2015), which uses wireless inductive charging.
• September 12, 2017: Apple announced the AirPower wireless charging mat. It was meant to be capable of charging an iPhone, an Apple Watch, and AirPods simultaneously; the product however was never released. On September 12, 2018, Apple removed most mentions of the AirPower from its website and on March 29, 2019, it canceled the product completely.^[28]

Qi devices[edit]

• Nokia launched two smartphones (the Lumia 820 and Lumia 920) on 5 September 2012, which feature Qi inductive charging.^[29]
• Google and LG launched the Nexus 4 in October 2012 which supports inductive charging using the Qi standard.
• Motorola Mobility launched its Droid 3 and Droid 4, both optionally support the Qi standard.
• On November 21, 2012 HTC launched the Droid DNA, which also supports the Qi standard.
• October 31, 2013 Google and LG launched the Nexus 5, which supports inductive charging with Qi.
• April 14, 2014 Samsung launched the Galaxy S5 that supports Qi wireless charging with either a wireless charging back or receiver.
• November 20, 2015 Microsoft launched the Lumia 950 XL and Lumia 950 which support charging with the Qi standard.
• February 22, 2016 Samsung announced its new flagship Galaxy S7 and S7 Edge which use an interface that is almost the same as Qi. The Samsung Galaxy S8 and Samsung Galaxy Note 8 released in 2017 also feature Qi wireless charging technology.
• September 12, 2017 Apple announced that the iPhone 8 and iPhone X would feature wireless Qi standard charging.

Furniture[edit]

• Ikea has a series of wireless charging furniture that supports the Qi standard.

Dual standard[edit]

• March 3, 2015: Samsung announced its new flagship Galaxy S6 and S6 Edge with wireless inductive charging through both Qi and PMA compatible chargers. All phones in the Samsung Galaxy S and Note lines following the S6 have supported wireless charging.
• November 6, 2015 BlackBerry released its new flagship BlackBerry Priv, the first BlackBerry phone to support wireless inductive charging through both Qi and PMA compatible chargers.

Research and other[edit]

• Transcutaneous Energy Transfer (TET) systems in artificial hearts and other surgically implanted devices.
• In 2006, researchers at the Massachusetts Institute of Technology reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin Soljačić, theorized that they could extend the distance between the coils by adding resonance to the equation. The MIT inductive power project, called WiTricity, uses a curved coil and capacitive plates.^[30][31]
• In 2012 the Russian private museum Grand Maket Rossiya opened featuring inductive charging on its model car exhibits.
• As of 2017, Disney Research has been developing and researching room-scale inductive charging for multiple devices.

Transportation[edit]

Electric vehicle wireless power transfer or wireless charging is generally divided into three categories: stationary charging when the vehicle is parked for an extended period of time; dynamic charging when the vehicle is driven on roads or highways; and quasi-dynamic or semi-dynamic charging, when the vehicle moves at low speeds between stops,^[32]: 847 for example when a taxi slowly drives at a taxi rank.^[33] Inductive charging is not considered a mature dynamic charging technology as it delivers the least power of the three electric road technologies, its receivers lose 20%-25% of the supplied power when installed on trucks, and its health effects have yet to be documented, according to a French government working group on electric roads.^[34]

Stationary charging[edit]

In one inductive charging system, one winding is attached to the underside of the car, and the other stays on the floor of the garage.^[35] The major advantage of the inductive approach for vehicle charging is that there is no possibility of electric shock, as there are no exposed conductors, although interlocks, special connectors and RCDs (ground fault interruptors, or GFIs) can make conductive coupling nearly as safe. An inductive charging proponent from Toyota contended in 1998 that overall cost differences were minimal, while a conductive charging proponent from Ford contended that conductive charging was more cost efficient.^[36]

From 2010 onwards car makers signaled interest in wireless charging as another piece of the digital cockpit. A group was launched in May 2010 by the Consumer Electronics Association to set a baseline for interoperability for chargers. In one sign of the road ahead a General Motors executive is chairing the standards, effort group. Toyota and Ford managers said they also are interested in the technology and the standards effort.^[37]

Daimler’s Head of Future Mobility, Professor Herbert Kohler, however, has expressed caution and said the inductive charging for EVs is at least 15 years away (from 2011) and the safety aspects of inductive charging for EVs have yet to be looked into in greater detail. For example, what would happen if someone with a pacemaker is inside the vehicle? Another downside is that the technology requires a precise alignment between the inductive pick-up and the charging facility.^[38]

In November 2011, the Mayor of London, Boris Johnson, and Qualcomm announced a trial of 13 wireless charging points and 50 EVs in the Shoreditch area of London’s Tech City, due to be rolled out in early 2012.^[39][40] In October 2014, the University of Utah in Salt Lake City, Utah added an electric bus to its mass transit fleet that uses an induction plate at the end of its route to recharge.^[41] UTA, the regional public transportation agency, plans to introduce similar buses in 2018.^[42] In November 2012 wireless charging was introduced with 3 buses in Utrecht, The Netherlands. January 2015, eight electric buses were introduced to Milton Keynes, England, which uses inductive charging in the road with proov/ipt technology at either end of the journey to prolong overnight charges.,^[43] Later bus routes in Bristol, London and Madrid followed.

Dynamic charging[edit]

The first working prototype of an electric vehicle that charges wirelessly while driving, which is known as «dynamic wireless charging» or «dynamic wireless power transfer», is generally regarded to have been developed at the University of California, Berkeley in the 1980s and 1990s. The first commercialized dynamic wireless charging system, Online Electric Vehicle (OLEV), was developed as early as 2009 by researchers at the Korea Advanced Institute of Science and Technology (KAIST).^[32]: 848 Vehicles using the system draw power from a power source underneath the road surface, which is an array of inductive rails or coils.^[44][45] Commercialization efforts of the technology have not been successful because of high costs,^[46] and its main technical challenge is low efficiency.^[47]: 57 Dynamic inductive charging infrastructure was found to increase the occurrence of reflective cracks in road surfaces.^{[47]: 64 [48]} As of 2021, companies and organizations such as Vedecom,^[49] Magment, Electreon, and IPT are developing dynamic inductive coil charging technologies.^[50] IPT is additionally developing a system that uses inductive rails instead of coils, as the current standards which use coils are «extremely expensive» for dynamic charging, according to the CEO of IPT.^[51]

Research and development[edit]

Work and experimentation is currently underway in designing this technology to be applied to electric vehicles. This could be implemented by using a predefined path or conductors that would transfer power across an air gap and charge the vehicle on a predefined path such as a wireless charging lane.^[52] Vehicles that could take advantage of this type of wireless charging lane to extend the range of their onboard batteries are already on the road.^[52] Some of the issues that are currently preventing these lanes from becoming widespread is the initial cost associated with installing this infrastructure that would benefit only a small percentage of vehicles currently on the road. Another complication is tracking how much power each vehicle was consuming/pulling from the lane. Without a commercial way to monetize this technology, many cities have already turned down plans to include these lanes in their public works spending packages.^[52] However this doesn’t mean that cars are unable to utilize large scale wireless charging. The first commercial steps are already being taken with wireless mats that allow electric vehicles to be charged without a corded connection while parked on a charging mat.^[52] These large scale projects have come with some issues which include the production of large amounts of heat between the two charging surfaces and may cause a safety issue.^[53] Currently companies are designing new heat dispersion methods by which they can combat this excess heat. These companies include most major electric vehicle manufacturers, such as Tesla, Toyota, and BMW.^[54]

Examples[edit]

• EPCOT Universe of Energy is equipped with moving theater «pews,» which take passengers/viewers through the exhibit. They are self-propelled, and inductively recharged when at rest.^[55] This exhibit with the recharging technology was in place ca. 2003.
• Hughes Electronics developed the Magne Charge interface for General Motors. The General Motors EV1 electric car was charged by inserting an inductive charging paddle into a receptacle on the vehicle. General Motors and Toyota agreed on this interface and it was also used in the Chevrolet S-10 EV and Toyota RAV4 EV vehicles.
• September 2015 Audi Wireless Charging (AWC) presented a 3.6 kW inductive charger^[56] during the 66th International Motor Show (IAA) 2015.
• September 17, 2015 Bombardier-Transportation PRIMOVE presented a 3.6 kW Charger for cars,^[57] which was developed at Site in Mannheim Germany.^[58]
• Transport for London has introduced inductive charging in a trial for double-decker buses in London.^[59]
• Magne Charge inductive charging was employed by several types of electric vehicles around 1998, but was discontinued^[60] after the California Air Resources Board selected the SAE J1772-2001, or «Avcon», conductive charging interface^[61] for electric vehicles in California in June 2001.^[62]
• In 1997 Conductix Wampler started with wireless charging in Germany, In 2002 20 buses started in operation In Turin with 60 kW charging. In 2013 the IPT technology was bought by Proov. In 2008 the technology was already used in the house of the future in Berlin with Mercedes A Class. Later Evatran also began development of Plugless Power, an inductive charging system it claims is the world’s first hands-free, plugless, proximity charging system for Electric Vehicles.^[63] With the participation of the local municipality and several businesses, field trials were begun in March 2010. The first system was sold to Google in 2011 for employee use at the Mountain View campus.^[64]
• Evatran began selling the Plugless L2 Wireless charging system to the public in 2014.^[65]
• Volvo Group invested in January 2019 in U.S.-based wireless charging specialist Momentum Dynamics.^[66] Volvo and Momentum Dynamics will run a three-year pilot project, starting in 2022, for wireless charging of electric taxis in taxi ranks.^[67]
• BRUSA Elektronik AG, a specialist provider and development company for electric vehicles, offers a wireless charging module named ICS with 3.7 kW power.^[68]
• A partnership between Cabonline, Jaguar, Momentum Dynamics, and Fortum Recharge is launching a wireless charging taxi fleet in Oslo, Norway. The fleet consists of 25 Jaguar I-Pace SUVs equipped with inductive charging pads rated at 50-75 kW. The pads use resonant inductive coupling operating at 85 Hz to improve wireless charging efficiency and range.^[69]
• On February 3, 2022, Hyundai Motor Group developed a wireless charging system for electric vehicles using the principle of magnetic induction.^[70] Power is transmitted to the vehicle through resonance between the magnetic pad at the bottom of the charging space and the magnetic pad at the bottom of the vehicle. The transmitted power is stored in the battery through a converter in the vehicle system. It was applied on a trial basis at Genesis Motor EV charging station located in South Korea.^[71]

Medical implications[edit]

Wireless charging is making an impact in the medical sector by means of being able to charge implants and sensors long-term that is located beneath the skin. Multiple companies offer rechargeable medical implant (e.g. implantable neurostimulators) which use inductive charging. Researchers have been able to print wireless power transmitting antenna on flexible materials that could be placed under the skin of patients.^[53] This could mean that under skin devices that could monitor the patient status could have a longer-term life and provide long observation or monitoring periods that could lead to better diagnosis from doctors. These devices may also make charging devices like pacemakers easier on the patient rather than having an exposed portion of the device pushing through the skin to allow corded charging. This technology would allow a completely implanted device making it safer for the patient. It is unclear if this technology will be approved for use – more research is needed on the safety of these devices.^[53] While these flexible polymers are safer than ridged sets of diodes they can be more susceptible to tearing during either placement or removal due to the fragile nature of the antenna that is printed on the plastic material. While these medical based applications seem very specific the high-speed power transfer that is achieved with these flexible antennas is being looked at for larger broader applications.^[53]

See also[edit]

References[edit]

External links[edit]

• How Inductors Work
• How Electric Toothbrushes Recharge Using Inductors
• Wireless Electricity Is Here
• Wireless charging
• Electric Bus Rapidly Recharges Using Wireless Charge Plates at Stops Archived 2016-03-07 at the Wayback Machine – Wired
• Tesla Tower – Inductive charging in year 1900
• Wireless Qi Charger, DiodeGoneWild on YouTube 16 August 2017

Inductive charging (also known as wireless charging or cordless charging) is a type of wireless power transfer. It uses electromagnetic induction to provide electricity to portable devices. Inductive charging is also used in vehicles, power tools, electric toothbrushes, and medical devices. The portable equipment can be placed near a charging station or inductive pad without needing to be precisely aligned or make electrical contact with a dock or plug.

Inductive charging is named so because it transfers energy through inductive coupling. First, alternating current passes through an induction coil in the charging station or pad. The moving electric charge creates a magnetic field, which fluctuates in strength because the electric current’s amplitude is fluctuating. This changing magnetic field creates an alternating electric current in the portable device’s induction coil, which in turn passes through a rectifier to convert it to direct current. Finally, the direct current charges a battery or provides operating power.^[1][2]

Greater distances between sender and receiver coils can be achieved when the inductive charging system uses resonant inductive coupling, where a capacitor is added to each induction coil to create two LC circuits with a specific resonance frequency. The frequency of the alternating current is matched with the resonance frequency, and the frequency is chosen depending on the distance desired for peak efficiency.^[1] Recent improvements to this resonant system include using a movable transmission coil (i.e., mounted on an elevating platform or arm) and the use of other materials for the receiver coil such as silver-plated copper or sometimes aluminum to minimize weight and decrease resistance due to the skin effect.

History[edit]

Induction power transfer was first used in 1894 when M. Hutin and M. Le-Blanc proposed an apparatus and method to power an electric vehicle.^[3] However, combustion engines proved more popular, and this technology was forgotten for a time.^[2]

In 1972, Professor Don Otto of the University of Auckland proposed a vehicle powered by induction using transmitters in the road and a receiver on the vehicle.^[2] In 1977, John E. Trombly was awarded a patent for an «Electromagnetically coupled battery charger.» The patent describes an application to charge headlamp batteries for miners (US 4031449). The first application of inductive charging used in the United States was performed by J.G. Bolger, F.A. Kirsten, and S. Ng in 1978. They made an electric vehicle powered with a system at 180 Hz with 20 kW.^[2] In California in the 1980s, a bus was produced, which was powered by inductive charging, and similar work was being done in France and Germany around this time.^[2]

In 2006, MIT began using^{[clarification needed]} resonant coupling. They were able to transmit a large amount of power without radiation over a few meters. This proved to be better for commercial needs, and it was a major step for inductive charging.^{[2][failed verification]}

The Wireless Power Consortium (WPC) was established in 2008, and in 2010 they established the Qi standard. In 2012, the Alliance for Wireless Power (A4WP) and the Power Matter Alliance (PMA) were founded. Japan established Broadband Wireless Forum (BWF) in 2009, and they established the Wireless Power Consortium for Practical Applications (WiPoT) in 2013. The Energy Harvesting Consortium (EHC) was also founded in Japan in 2010. Korea established the Korean Wireless Power Forum (KWPF) in 2011.^[2] The purpose of these organizations is to create standards for inductive charging. In 2018, The Qi Wireless Standard was adopted for use in military equipment in North Korea, Russia, and Germany

Application areas[edit]

Applications of inductive charging can be divided into two broad categories: Low power and high power:

• Low power applications are generally supportive of small consumer electronic devices such as cell phones, handheld devices, some computers, and similar devices which normally charge at power levels below 100 watts. Typically, the AC utility frequency of 50 or 60 Hertz is used.^[4]
• High power inductive charging generally refers to inductive charging of batteries at power levels above 1 kilowatt. The most prominent application area for high power inductive charging is in support of electric vehicles, where inductive charging provides an automated and cordless alternative to plug-in charging. Power levels of these devices can range from approximately 1 kilowatt to 300 kilowatts or higher. All high-power inductive charging systems use resonated primary and secondary coils. These systems work in the long wave range with frequencies up to 130 kHz. The use of short wave frequencies can enhance the system’s efficiency and size^[5] but would eventually transmit the signal worldwide. High powers raise the concern of electromagnetic compatibility and radio frequency interference.

Advantages[edit]

• Protected connections – No corrosion when the electronics are enclosed, away from water or oxygen in the atmosphere. Less risk of electrical faults such as short circuits due to insulation failure, especially where connections are made or broken frequently.^[6]
• Low infection risk – For embedded medical devices, the transmission of power via a magnetic field passing through the skin avoids the infection risks associated with wires penetrating the skin.^[7]
• Durability – Without the need to constantly plug and unplug the device, there is significantly less wear and tear on the socket of the device and the attaching cable.^[6]
• Increased convenience and aesthetic quality – No need for cables.
• Automated high power inductive charging of electric vehicles allows for more frequent charging events and consequently an extension of driving range.
• Inductive charging systems can be operated automatically without dependence on people to plug and unplug. This results in higher reliability.
• Automatic operation of inductive charging in roads theoretically allows vehicles to run indefinitely.^[8]

Disadvantages[edit]

The following disadvantages have been noted for low-power (i.e., less than 100 watts) inductive charging devices, and may not apply to high-power (i.e., greater than 5 kilowatts) electric vehicle inductive charging systems.^{[citation needed]}

• Slower charging – Due to the lower efficiency, devices take 15 percent longer to charge when supplied power is the same amount.^[9]
• More expensive – Inductive charging also requires drive electronics and coils in both device and charger, increasing the complexity and cost of manufacturing.^[10][11]
• Inconvenience – When a mobile device is connected to a cable, it can be moved around (albeit in a limited range) and operated while charging. In most implementations of inductive charging, the mobile device must be left on a pad to charge, and thus can’t be moved around or easily operated while charging. With some standards, charging can be maintained at a distance, but only with nothing present between the transmitter and receiver.^[6]
• Compatible standards – Not all devices are compatible with different inductive chargers. However, some devices have started to support multiple standards.

Inefficiency has other costs besides longer charge times. Inductive chargers produce more waste heat than wired chargers, which may negatively impact battery longevity.^{[13][better source needed]} An amateur 2020 analysis of energy use conducted with a Pixel 4 found that a wired charge from 0 to 100 percent consumed 14.26 Wh (watt-hours), while a wireless charging stand used 19.8 Wh, an increase of 39%. Using a generic brand wireless charging pad and mis-aligning the phone produced consumption up to 25.62 Wh, or an 80% increase. The analysis noted that while this is not likely to be noticeable to individuals, it has negative implications for greater adoption of smartphone wireless charging.^[14]

Newer approaches reduce transfer losses through the use of ultra thin coils, higher frequencies, and optimized drive electronics. This results in more efficient and compact chargers and receivers, facilitating their integration into mobile devices or batteries with minimal changes required.^[15][16] These technologies provide charging times comparable to wired approaches, and they are rapidly finding their way into mobile devices.

Safety[edit]

An increase in high-power inductive charging devices has led to researchers looking into the safety factor of the electromagnetic fields (EMF) put off by larger inductor coils. With the recent interest in the expansion of high power inductive charging with electric cars, an increase in health and safety concerns has arisen. To provide a larger distance of coverage you would in return need a larger coil for your inductor. An electric car with this size conductor would need about 300 kW from a 400 V battery to emit enough charge.^{[clarification needed]} This much exposure to the skin of a human could prove harmful if not met within the right conditions. Exposure limits can be satisfied even when the transmitter coil is very close to the body.^[17]

Testing has been done on how organs can be affected by these fields when put under low levels of frequency from these fields. When exposed to various levels of frequencies you can experience dizziness, light flashes, or tingling through nerves. At higher ranges, you can experience heating or even burning of the skin. Most people experience low EMF in everyday life. The most common place to experience these frequencies is with a wireless charger, usually on a nightstand located near the head.^[18]

Standards[edit]

Standards refer to the different set operating systems with which devices are compatible. There are two main standards: Qi and PMA.^[12] The two standards operate very similarly, but they use different transmission frequencies and connection protocols.^[12] Because of this, devices compatible with one standard are not necessarily compatible with the other standard. However, there are devices compatible with both standards.

• Magne Charge, a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles (BEV) formerly made by General Motors.
• The emerging SAE J2954 standard allows inductive car charging over a pad, with power delivery up to 11 kW.^[19]
• Qi, an interface standard developed by the Wireless Power Consortium for inductive electrical power transfer. At the time of July 2017, it is the most popular standard in the world, with more than 200 million devices supporting this interface.
• AirFuel Alliance:
  • In January 2012, the IEEE announced the initiation of the Power Matters Alliance (PMA) under the IEEE Standards Association (IEEE-SA) Industry Connections. The alliance is formed to publish a set of standards for inductive power that are safe and energy-efficient, and have smart power management. The PMA will also focus on the creation of an inductive power ecosystem^[20]
  • Rezence was an interface standard developed by the Alliance for Wireless Power (A4WP).
  • A4WP and PMA merged into the AirFuel Alliance in 2015.^[21]

Electronic devices[edit]

Many manufacturers of smartphones have started adding this technology into their devices, the majority adopting the Qi wireless charging standard. Major manufacturers such as Apple and Samsung produce many models of their phones in high volume with Qi capabilities. The popularity of the Qi standard has driven other manufacturers to adopt this as their own standard.^[22] Smartphones have become the driving force of this technology entering consumers’ homes, where many household technologies have been developed to utilize this technology.

Samsung and other companies have begun exploring the idea of «surface charging», building an inductive charging station into an entire surface such as a desk or table.^[22] Contrarily, Apple and Anker are pushing a dock-based charging platform. This includes charging pads and disks that have a much smaller footprint. These are geared for consumers who wish to have smaller chargers that would be located in common areas and blend in with the current décor of their home.^[22] Due to the adoption of the Qi standard of wireless charging, any of these chargers will work with any phone as long as it is Qi capable.^[22]

Another development is reverse wireless charging, which allows a mobile phone to wirelessly discharge its own battery into another device.^[23]

Examples[edit]

• Oral-B rechargeable toothbrushes by the Braun company have used inductive charging since the early 1990s.
• At the Consumer Electronics Show (CES) in January 2007, Visteon unveiled its inductive charging system for in-vehicle use that could charge only specially made cell phones to MP3 players with compatible receivers.^[24]
• April 28, 2009: An Energizer inductive charging station for the Wii remote was reported on IGN.^[25]
• At CES in January 2009, Palm, Inc. announced its new Pre smartphone would be available with an optional inductive charger accessory, the «Touchstone». The charger came with a required special backplate that became standard on the subsequent Pre Plus model announced at CES 2010. This was also featured on later Pixi, Pixi Plus, and Veer 4G smartphones. Upon launch in 2011, the ill-fated HP Touchpad tablet (after HP’s acquisition of Palm Inc.) had a built in touchstone coil that doubled as an antenna for its NFC-like Touch to Share feature.^[15][26][27]
• March 24, 2013: Samsung launched the Galaxy S3, which supports an optionally retrofittable back cover accessory, included in their separate “Wireless Charging Kit”.
• Nokia announced on September 5, 2012, the Lumia 920 and Lumia 820, which supports respectively integrate inductive charging and inductive charging with an accessory back.
• March 15, 2013: Samsung launched the Galaxy S4, which supports inductive charging with an accessory back cover.
• July 26, 2013: Google and ASUS launched the Nexus 7 2013 Edition with integrated inductive charging.
• September 9, 2014: Apple announced Apple Watch (released on April 24, 2015), which uses wireless inductive charging.
• September 12, 2017: Apple announced the AirPower wireless charging mat. It was meant to be capable of charging an iPhone, an Apple Watch, and AirPods simultaneously; the product however was never released. On September 12, 2018, Apple removed most mentions of the AirPower from its website and on March 29, 2019, it canceled the product completely.^[28]

Qi devices[edit]

• Nokia launched two smartphones (the Lumia 820 and Lumia 920) on 5 September 2012, which feature Qi inductive charging.^[29]
• Google and LG launched the Nexus 4 in October 2012 which supports inductive charging using the Qi standard.
• Motorola Mobility launched its Droid 3 and Droid 4, both optionally support the Qi standard.
• On November 21, 2012 HTC launched the Droid DNA, which also supports the Qi standard.
• October 31, 2013 Google and LG launched the Nexus 5, which supports inductive charging with Qi.
• April 14, 2014 Samsung launched the Galaxy S5 that supports Qi wireless charging with either a wireless charging back or receiver.
• November 20, 2015 Microsoft launched the Lumia 950 XL and Lumia 950 which support charging with the Qi standard.
• February 22, 2016 Samsung announced its new flagship Galaxy S7 and S7 Edge which use an interface that is almost the same as Qi. The Samsung Galaxy S8 and Samsung Galaxy Note 8 released in 2017 also feature Qi wireless charging technology.
• September 12, 2017 Apple announced that the iPhone 8 and iPhone X would feature wireless Qi standard charging.

Furniture[edit]

• Ikea has a series of wireless charging furniture that supports the Qi standard.

Dual standard[edit]

• March 3, 2015: Samsung announced its new flagship Galaxy S6 and S6 Edge with wireless inductive charging through both Qi and PMA compatible chargers. All phones in the Samsung Galaxy S and Note lines following the S6 have supported wireless charging.
• November 6, 2015 BlackBerry released its new flagship BlackBerry Priv, the first BlackBerry phone to support wireless inductive charging through both Qi and PMA compatible chargers.

Research and other[edit]

• Transcutaneous Energy Transfer (TET) systems in artificial hearts and other surgically implanted devices.
• In 2006, researchers at the Massachusetts Institute of Technology reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin Soljačić, theorized that they could extend the distance between the coils by adding resonance to the equation. The MIT inductive power project, called WiTricity, uses a curved coil and capacitive plates.^[30][31]
• In 2012 the Russian private museum Grand Maket Rossiya opened featuring inductive charging on its model car exhibits.
• As of 2017, Disney Research has been developing and researching room-scale inductive charging for multiple devices.

Transportation[edit]

Electric vehicle wireless power transfer or wireless charging is generally divided into three categories: stationary charging when the vehicle is parked for an extended period of time; dynamic charging when the vehicle is driven on roads or highways; and quasi-dynamic or semi-dynamic charging, when the vehicle moves at low speeds between stops,^[32]: 847 for example when a taxi slowly drives at a taxi rank.^[33] Inductive charging is not considered a mature dynamic charging technology as it delivers the least power of the three electric road technologies, its receivers lose 20%-25% of the supplied power when installed on trucks, and its health effects have yet to be documented, according to a French government working group on electric roads.^[34]

Stationary charging[edit]

In one inductive charging system, one winding is attached to the underside of the car, and the other stays on the floor of the garage.^[35] The major advantage of the inductive approach for vehicle charging is that there is no possibility of electric shock, as there are no exposed conductors, although interlocks, special connectors and RCDs (ground fault interruptors, or GFIs) can make conductive coupling nearly as safe. An inductive charging proponent from Toyota contended in 1998 that overall cost differences were minimal, while a conductive charging proponent from Ford contended that conductive charging was more cost efficient.^[36]

From 2010 onwards car makers signaled interest in wireless charging as another piece of the digital cockpit. A group was launched in May 2010 by the Consumer Electronics Association to set a baseline for interoperability for chargers. In one sign of the road ahead a General Motors executive is chairing the standards, effort group. Toyota and Ford managers said they also are interested in the technology and the standards effort.^[37]

Daimler’s Head of Future Mobility, Professor Herbert Kohler, however, has expressed caution and said the inductive charging for EVs is at least 15 years away (from 2011) and the safety aspects of inductive charging for EVs have yet to be looked into in greater detail. For example, what would happen if someone with a pacemaker is inside the vehicle? Another downside is that the technology requires a precise alignment between the inductive pick-up and the charging facility.^[38]

In November 2011, the Mayor of London, Boris Johnson, and Qualcomm announced a trial of 13 wireless charging points and 50 EVs in the Shoreditch area of London’s Tech City, due to be rolled out in early 2012.^[39][40] In October 2014, the University of Utah in Salt Lake City, Utah added an electric bus to its mass transit fleet that uses an induction plate at the end of its route to recharge.^[41] UTA, the regional public transportation agency, plans to introduce similar buses in 2018.^[42] In November 2012 wireless charging was introduced with 3 buses in Utrecht, The Netherlands. January 2015, eight electric buses were introduced to Milton Keynes, England, which uses inductive charging in the road with proov/ipt technology at either end of the journey to prolong overnight charges.,^[43] Later bus routes in Bristol, London and Madrid followed.

Dynamic charging[edit]

The first working prototype of an electric vehicle that charges wirelessly while driving, which is known as «dynamic wireless charging» or «dynamic wireless power transfer», is generally regarded to have been developed at the University of California, Berkeley in the 1980s and 1990s. The first commercialized dynamic wireless charging system, Online Electric Vehicle (OLEV), was developed as early as 2009 by researchers at the Korea Advanced Institute of Science and Technology (KAIST).^[32]: 848 Vehicles using the system draw power from a power source underneath the road surface, which is an array of inductive rails or coils.^[44][45] Commercialization efforts of the technology have not been successful because of high costs,^[46] and its main technical challenge is low efficiency.^[47]: 57 Dynamic inductive charging infrastructure was found to increase the occurrence of reflective cracks in road surfaces.^{[47]: 64 [48]} As of 2021, companies and organizations such as Vedecom,^[49] Magment, Electreon, and IPT are developing dynamic inductive coil charging technologies.^[50] IPT is additionally developing a system that uses inductive rails instead of coils, as the current standards which use coils are «extremely expensive» for dynamic charging, according to the CEO of IPT.^[51]

Research and development[edit]

Work and experimentation is currently underway in designing this technology to be applied to electric vehicles. This could be implemented by using a predefined path or conductors that would transfer power across an air gap and charge the vehicle on a predefined path such as a wireless charging lane.^[52] Vehicles that could take advantage of this type of wireless charging lane to extend the range of their onboard batteries are already on the road.^[52] Some of the issues that are currently preventing these lanes from becoming widespread is the initial cost associated with installing this infrastructure that would benefit only a small percentage of vehicles currently on the road. Another complication is tracking how much power each vehicle was consuming/pulling from the lane. Without a commercial way to monetize this technology, many cities have already turned down plans to include these lanes in their public works spending packages.^[52] However this doesn’t mean that cars are unable to utilize large scale wireless charging. The first commercial steps are already being taken with wireless mats that allow electric vehicles to be charged without a corded connection while parked on a charging mat.^[52] These large scale projects have come with some issues which include the production of large amounts of heat between the two charging surfaces and may cause a safety issue.^[53] Currently companies are designing new heat dispersion methods by which they can combat this excess heat. These companies include most major electric vehicle manufacturers, such as Tesla, Toyota, and BMW.^[54]

Examples[edit]

• EPCOT Universe of Energy is equipped with moving theater «pews,» which take passengers/viewers through the exhibit. They are self-propelled, and inductively recharged when at rest.^[55] This exhibit with the recharging technology was in place ca. 2003.
• Hughes Electronics developed the Magne Charge interface for General Motors. The General Motors EV1 electric car was charged by inserting an inductive charging paddle into a receptacle on the vehicle. General Motors and Toyota agreed on this interface and it was also used in the Chevrolet S-10 EV and Toyota RAV4 EV vehicles.
• September 2015 Audi Wireless Charging (AWC) presented a 3.6 kW inductive charger^[56] during the 66th International Motor Show (IAA) 2015.
• September 17, 2015 Bombardier-Transportation PRIMOVE presented a 3.6 kW Charger for cars,^[57] which was developed at Site in Mannheim Germany.^[58]
• Transport for London has introduced inductive charging in a trial for double-decker buses in London.^[59]
• Magne Charge inductive charging was employed by several types of electric vehicles around 1998, but was discontinued^[60] after the California Air Resources Board selected the SAE J1772-2001, or «Avcon», conductive charging interface^[61] for electric vehicles in California in June 2001.^[62]
• In 1997 Conductix Wampler started with wireless charging in Germany, In 2002 20 buses started in operation In Turin with 60 kW charging. In 2013 the IPT technology was bought by Proov. In 2008 the technology was already used in the house of the future in Berlin with Mercedes A Class. Later Evatran also began development of Plugless Power, an inductive charging system it claims is the world’s first hands-free, plugless, proximity charging system for Electric Vehicles.^[63] With the participation of the local municipality and several businesses, field trials were begun in March 2010. The first system was sold to Google in 2011 for employee use at the Mountain View campus.^[64]
• Evatran began selling the Plugless L2 Wireless charging system to the public in 2014.^[65]
• Volvo Group invested in January 2019 in U.S.-based wireless charging specialist Momentum Dynamics.^[66] Volvo and Momentum Dynamics will run a three-year pilot project, starting in 2022, for wireless charging of electric taxis in taxi ranks.^[67]
• BRUSA Elektronik AG, a specialist provider and development company for electric vehicles, offers a wireless charging module named ICS with 3.7 kW power.^[68]
• A partnership between Cabonline, Jaguar, Momentum Dynamics, and Fortum Recharge is launching a wireless charging taxi fleet in Oslo, Norway. The fleet consists of 25 Jaguar I-Pace SUVs equipped with inductive charging pads rated at 50-75 kW. The pads use resonant inductive coupling operating at 85 Hz to improve wireless charging efficiency and range.^[69]
• On February 3, 2022, Hyundai Motor Group developed a wireless charging system for electric vehicles using the principle of magnetic induction.^[70] Power is transmitted to the vehicle through resonance between the magnetic pad at the bottom of the charging space and the magnetic pad at the bottom of the vehicle. The transmitted power is stored in the battery through a converter in the vehicle system. It was applied on a trial basis at Genesis Motor EV charging station located in South Korea.^[71]

Medical implications[edit]

Wireless charging is making an impact in the medical sector by means of being able to charge implants and sensors long-term that is located beneath the skin. Multiple companies offer rechargeable medical implant (e.g. implantable neurostimulators) which use inductive charging. Researchers have been able to print wireless power transmitting antenna on flexible materials that could be placed under the skin of patients.^[53] This could mean that under skin devices that could monitor the patient status could have a longer-term life and provide long observation or monitoring periods that could lead to better diagnosis from doctors. These devices may also make charging devices like pacemakers easier on the patient rather than having an exposed portion of the device pushing through the skin to allow corded charging. This technology would allow a completely implanted device making it safer for the patient. It is unclear if this technology will be approved for use – more research is needed on the safety of these devices.^[53] While these flexible polymers are safer than ridged sets of diodes they can be more susceptible to tearing during either placement or removal due to the fragile nature of the antenna that is printed on the plastic material. While these medical based applications seem very specific the high-speed power transfer that is achieved with these flexible antennas is being looked at for larger broader applications.^[53]

See also[edit]

References[edit]

External links[edit]

• How Inductors Work
• How Electric Toothbrushes Recharge Using Inductors
• Wireless Electricity Is Here
• Wireless charging
• Electric Bus Rapidly Recharges Using Wireless Charge Plates at Stops Archived 2016-03-07 at the Wayback Machine – Wired
• Tesla Tower – Inductive charging in year 1900
• Wireless Qi Charger, DiodeGoneWild on YouTube 16 August 2017