The surge analysis of induction heating power supply with PLL

This paper presents the mechanism of surges with induction heating power supply. A 2 kW full-bridge series resonant inverter based on zero-voltage-switching (ZVS) and phase-locked-loop (PLL) control is used as a power supply. In this inverter, the PLL does not only keep the output current and voltage in phase but also manage the system to operate at ZVS mode. When the PLL mismatches the resonant frequency in a manner of phase lead, the inverter works at the nonZVS mode and the surge voltage appears on the switching elements heavily, which is almost decided by the recovery energy of drain-source diode of power devices. The surge model found in this paper is very useful.