Induction heating inverter with active power factor correction

The behaviour of a resonant inverter used as a power factor corrector, aime d at induction heating applications, is described. The bulky de filter betw een the rectifier and the inverter is substituted by a high frequency filte r in such a way that the input to the inverter is a full-wave rectified wav eform. 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 l oss 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, whe n the inverter does not operate during the full input cycle, both the outpu t power and the power factor are degraded.