Last time we briefly described the choice of wireless solution chip in this article(Selection and recommendation of wireless charging chip). Now we elaborate further in wireless charging scheme and chips.

Currently, there are many QI standard wireless charging solutions on the market. First of all, let us understand the differences between ordinary wireless charging solutions and QI standard wireless charging solutions:

Ordinary wireless charger solutions include the QI-compliant and non-compliant wireless charger solution. Not every useful wireless charger solution can pass the QI tests, though they can work normally.

Incompatible with QI: ( There are two types of wireless charging solutions )

One is non-protocol with no FOD detection. The MCU with a cost of about RMB 1 yuan or less is used for completion.
The other one applies protocols with FOD detection functions, but can not pass QI tests. Their action of transmission and reception are peer-to-peer. They are typically used for low current wear products.

Compatible with QI:

This kind of scheme is more common, and the largest number on the market is this type of scheme. Common MCU chips come from ST, generalplus, nuvoton, chipsea etc. This chip is an 8-bit microcontroller. The price of these chips is higher than the chips incompatible with QI.

These solutions can generally perform functions such as FOD and OCP(Over Current Protection). However, DPL(Dynamic PowerLimiting) and ATB(Automatic Temperature Balance) do not be supported.

They may have FOD (foreign object detection) or PMOD (enhanced parasitic metal detection) function. When the metal plate is detected the charging can be stopped. But they could not perform reliability test under various possible conditions. Therefore, maybe some of these products in the market have no ability to pass QI laboratory tests.

At present, the difficulty in QI testing is generally in FOD, DPL, and ATB. Much wireless charging cannot pass the test just because of the failure of these three items.

So, ST’s wireless charger must not pass QI certification?

It is not absolutely. But it is difficult for software engineers because of the slower running 8-bit microcontroller. It is relatively rare for the market to really use it to pass QI test. It also means that if you use an 8-bit microcontroller to QI need to spend a huge R & D time to verify this possibility. So people are reluctant to do it. It is not worth to spend six months to 1 year on a product QI test.

Wireless charging solutions that can pass the QI test:

There are about two camps for QI-certified wireless charging solutions (Note: 32-bit MCUs are used)

Made in China: nuVolta, E-Charging, chipsvision, generalplus etc.
Not made in China: TI, NXP, IDT, ST32-bits etc.

They often use a 10W power chip integrated + 2 drivers + 4 MOSs to make the peripheral LAYOUT simple. Or use TI driver + ONsemi MOS. They all can achieve 83-85% conversion efficiency.
These programs greatly facilitate the design of engineers. Reduced the difficulty of passing QI detection.