A new induction heating circuit with clamped capacitor voltage suitable for heating to above Curie temperature

Abstract

The partial series-resonant power converter, previously only used for DC-DC converters, is applied to induction heating. The circuit is a half-bridge, series-resonant circuit with clamping diodes that constrain the voltage of the resonant capacitors to values between zero and the supply voltage. Three types of control are investigated: constant switching frequency; constant turn-off current; and a combination thereof. The latter seemed to be the best. This circuit is only found suitable for loads for which the Q value is low while the temperature of the workpiece is below the Curie temperature.<>