Induction heating inverter with active power factor correction

Abstract

The behaviour of a resonant inverter used as a power factor corrector, aimed at induction heating applications, is described. The bulky dc filter between the rectifier and the inverter is substituted by a high frequency filter in such a way that the input to the inverter is a full-wave rectified waveform. For a given power at the load, and compared with an inverter with a constant input, it is shown that power factor correction is achieved at the expense of a higher current stress in the inverter, although there is no loss of efficiency. A procedure for rating the elements of the power stages is provided, and a design example is worked out. It is also shown that, when the inverter does not operate during the full input cycle, both the output power and the power factor are degraded.