Efficiency Enhancement of Power Amplifier Using Power Pulsewidth Modulation for Wireless Power Transfer

Power amplifier (PA) is the core device for dc-RF conversion in wireless power transfer (WPT) system. However, the drain efficiency (DE) of PA decreases significantly due to the load mismatch effect at low output power levels. In this letter, a power pulsewidth modulation (PPWM) power supply is proposed to enhance the wide-power-range efficiency of PA. In this way, the average output power demand is met, and the maximum DE can always be achieved when the output power backs off. A prototype comprising a driver amplifier, a 5.8-GHz/10-W class-F PA and a 30-W PPWM power supply is fabricated and tested in the lab. Experimental results and performance comparison are provided to verify the effectiveness of the proposed method.