Open loop dynamic transmitter voltage scaling for fast response and wide load range power efficient WPT system

This paper presents a fast response wireless power delivery system with open loop dynamic transmitter voltage scaling technique to keep power efficiency in wide load range. In this technique, according to change of receiver side power consumption, the driving voltage of the transmitter (TX) coil is properly adjusted to control transmission power. The transmitting power and switching loss can be reduced in proportion to the square of the driving voltage. Therefore, it can improve power efficiency. To enhance power control speed, the driving voltage is not locally regulated but automatically determined by the feedback loop of the total WPT system. Fabricated test chips in 180-nm LDMOS process achieved maximum power efficiency of 50.9% when the output power is 0.5W. The output power ranges from 0.03W to 0.5W. The output voltage ripple is kept within 3.5% even when the output power is abruptly changed by one order of magnitude.