A 6.78MHz Adaptive-ZVS Class-D PA with Dynamic Dead-Time for Wireless Power Transfer system

Department of Electrical EngineeringIn this thesis, a class-D power amplifier (PA) with adaptive zero-voltage switching (A-ZVS) technique for Low power 6.78 MHz resonant wireless power transfer (R-WPT) system is proposed. In R-WPT operation, the loading impedance of a PA can be varied by the process tolerance of the LC resonant components and WPT environments, such as the resonant topology, coupling coefficient and loading condition of the receiver. The proposed A-ZVS feedback loop of PA calibrates the equivalent resonant capacitance using PWM-controlled switched capacitor in real-time to achieve ZVS by adjusting the loading impedance to be slightly inductive. Furthermore, the proposed PA adjust the dead-time according to variation of WPT environments. The proposed PA was fully integrated except for one switched capacitor used as the tuning element and fabricated in a TSMC 0.18um BCD process. The measurement results demonstrated robust ZVS operation with a peak system efficiency of 52.7% and an enhanced maximum transmitting power of 107%.ope