Ringing suppressing method in 13.56MHz resonant inverter for wireless power transfer systems

This paper presents the ringing suppressing method in class D resonant inverter operating at 13.56MHz for wireless power transfer systems. The ringing loop in half-bridge topology inverter at 13.56MHz strongly effect to the stable, performance and efficiency of the inverter. Typically, this ringing can be damped by using a snubber circuit which is placed parallel to the MOSFETs or using a damping circuit which is place inside the ringing loop. But in the resonant inverter with high power and high frequency, the snubber circuit or general damping circuit may reduce performance and efficiency of inverter. A new damping circuit combining with drive circuit design solution is proposed in this paper. The simulation and experiment results showed that the proposed design significantly suppresses the ringing current and ringing voltage in the circuit. The power loss on the MOSFETs is reduced while the efficiency of inverter increases 2% to obtain 93.1% at 1.2kW output power. The inverter becomes more stable and compact.