This paper describes a high-speed switching method of MOSFETs applied to a chopper and a half bridge inverter. By using a voltage boost auxiliary circuit fed by the gate drive power supply, the turn-off time of the MOSFET can be effectively reduced, which enables a high-frequency drive and reduction of the switching loss. It was confirmed through experimental tests that the turn-off dv/dt of the MOSFET was drastically improved by 9 times with the proposed method, especially in the low-load range.