Quasi-series-resonant-type soft-switching phase shift modulated inverter

A prototype of a series-load resonant and quasi-resonant hybrid-type soft-switching high frequency inverter is proposed for induction heating applications, together with its operating principle. The bridge legs of the inverter treated here have the salient feature of a power regulation function under a constant switching frequency which is based on pulse phase shift modulation due to the current leading leg and the current lagging leg. Because quasi-resonant current flowing through each active power switch becomes a trapezoidal waveform or quasi-square waveform due to the quasi-series resonant operation, it is expected that the conduction loss increase by the peak current through each power semiconductor switching device in the full bridge arm be basically suppressed as compared with that of the conventional series load resonant high frequency inverter. The design procedure of circuit components to achieve a soft-switching of this high frequency inverter, the reduction effect of switch peak voltage stress and its power regulation performance are described and discussed in detail. The effectiveness of the 5 kW-21 kHz soft-switching pulse phase shift modulated high frequency inverter using the IGBT power modules is proved on the basis of the power regulation performance and power conversion efficiency.