Abstract: A power supply receives an alternating current which is converted by a fixed rectifier to a direct current. The direct current is converted by an inverter to an alternating current of a desired frequency and provided to a parallel resonant fixed load circuit such as a work-coil of an induction heater. The power supply includes a device for reducing amplitude of at least a second harmonic of a fundamental frequency of the current output by the inverter so that a filter connected to the load circuit can have a roll-off frequency close to the design frequency of the load circuit.