Chip design of wireless power transfer using frequency variation

Wireless power transfer (WPT) and rapid charging system is important issue for many applications, particularly on mobile and biomedical devices. To perform high efficiency, first the system tracks maximum power transfer by sweeping the resonant frequency. The transmitter can use the best resonant frequency for wireless power transfer, and the receiver device charges a battery as fast. This can correct the frequency drift in manufacture, to promote the transferring efficiency. A voltage detection circuit of the receiver device is detecting charging state of the battery. Transmitter device checks whether a high-frequency transmission circuit transmits a fully-charged signal. The transmitter device shuts down the power and enters standby mode as the battery is fully charged. By maximum power tracking approach, higher wireless transmission efficiency can be achieved. The prototyping chips of transmitter and receiver had been implemented using TSMC 0.25 μm HV process. Experiments shown the max. efficient of WPT can achieve about 60 ~ 70%.