An automatic half-bridge resonant inverter with three-phase three-switch buck-type rectifier

This paper presents a design of a 1.5kW half-bridge resonant inverter system for induction heating applications. The inverter operates at a switching frequency range of 20-40 kHz where the zero voltage condition operation is maintained. The rectifier circuit employs a pulse-width modulation (PWM) operating at the switching frequency of 10 kHz. With the proposed system, the output power can be controlled by both the inverter frequency and the dc bus voltage. This provides sufficiently fast response to alleviate the switch´s current under no load situation (i.e. no work-piece in the induction coil). The advantages of the proposed control system are small size of filter circuitry, low switching loss and faster response at a no load condition.