High frequency voltage-fed inverter with phase-shift control for induction heating

A voltage-fed resonant LCL inverter with phase-shift control is presented. The control strategy is seen to offer advantages in the megahertz operating region where a constant switching frequency is required. The inverter topology is inherently modular and higher output powers may therefore be readily achieved by adding additional MOSFET switching cells, the devices in each cell having only a modest rating. The inverter steady-state operation is analysed using fundamental frequency analysis. The predictions are verified through time-domain simulations and measurements of a 1.6 MHz 1 kW prototype.