Since wireless charging technology was first applied in the iPhone 8/iPhone X, the demand for wireless chargers has started to thrive, causing wireless charging standards to gradually be set and encouraging more factories to join in this field. In this article, we will introduce a type of wireless charger reference design to facilitate factories which intend to make an investment into the wireless charger market to accelerate its development speed.

Wireless Charging Criterion Gradually Set Market Grows up Rapidly

Wireless charging, also called as induction charging or non-contact inductive charging, transmits energy to a power device via a power supply device (charger) by making use of near-field induction, that is, inductive coupling. This device charges a battery by making use of the energy received and meanwhile uses the energy for itself. Basically, the energy is transmitted in the form of inductive coupling between the charger and the power device, so there is no need to use an electric cable for connection, therefore, both the charger and the power device can realize no exposure of conductive contact, and it is more convenient than wired charging.

Actually, wireless charging technology had already been launched for a long time, during which it experienced a variety of competitions in terms of technologies and standards. Due to the lack of a unified standard, the speed of promoting wireless charging technology has been affected. With the iPhone 8/iPhone X selecting Qi wireless charging technology, Qi wireless charging technology has already got the upper hand by relying on the huge sales volume of iPhone cellphones, although we cannot regard the argument regarding wireless charging technology criterion as having been ended.

Qi (pronounced and named after the Chinese character of qi, "energy flow"), is an interconnection standard for short-distance (40mm, 1.6 inches) wireless inductive power transmission formulated by the Wireless Power Consortium (WPC), with the aim of providing wireless charging for mobile phones and other portable electronic devices. According to the Qi standard, a power of 5W or less can be transmitted by making use of inductive transmission under a low power standard, and both receiving and transmitting make use of flat inductance and energy transmitted via an inductive coupling method. The distance between two inductors (coils) can be 5mm, or up to 40mm as needed

After issuing the specifications of the 1.2.1 version for Qi wireless charging technology, specifications of medium-power products were also added. At present, there are more than 700 (mobile phones and mobile power packs are included) types of products which have passed the certification of Qi wireless charging technology, and restaurants such as Starbucks and McDonald are also starting to provide Qi wireless charging pads to their clients, accelerating the promotion and popularization of wireless charging technology even more.

In order to assist manufacturers in developing wireless chargers as soon as possible, Arrow ESC introduced the ST wireless charger reference design. The reference design of this type of ST 15W fixed frequency wireless charger is based on the STWBC-EPTR transmitter chips for ST medium-power wireless chargers, so it is a low-cost reference solution.

The reference design of this type of fixed frequency wireless charger ST 15W conforms to the Qi 1.2.2 specification, and it supports half-bridge topology, and can support Foreign Object Detection (FOD) based on the quality factor (Q factor) , and it also supports Foreign body Detection technology based on calibration power loss calculation, supports a 15W Qi MP receiver, and is available with an LP receiver of 5W of output power, with a quality factor measurement, as well as LED which can be used for indicating charging status. It also supports quick chargers as well as power supplies ranging between 5-12V.

The core chips used in this wireless charging reference design include STWBC-EPTR, TSV521ICT, STL8DN6LF3, STL10N3LLH5 from STMicroelectronics, and MCP14700 from Microchip, C1812C104J1GACTU of Kemet, and SRF1260-4R7Y from Bourns. It is mainly used in mobile phone charging, tablet charging, handheld devices, mobile phone accessories, and other fields

With Apple choosing the Qi standard as its wireless charging standard, more manufacturers have been led to produce devices which support the Qi wireless charging standard, and the production cost and sales price of wireless chargers has also been decreased, and the sales volume of wireless charging devices has also improved. There will be more and more mobile devices which support wireless charging technology in the future, truly freeing mobile devices from the bondage of "wires", so there would be an extremely spectacular market development future, and it is worthy for manufacturers to be engaged in the development of related products.