Reducing IGBT losses in ZCS series resonant converters

The fundamental operational parameter that controls the losses in series resonant power converters was found to be the (reflected) voltage transfer ratio. Losses, which are a function of the average current (such as conduction losses of IGBTs and diodes), are independent of the switching frequency. Losses which are associated with the RMS are a function of both the (reflected) DC current voltage ratio and the switching frequency ratio. Universal and normalized graphs, derived in this study, can be conveniently used to assess expected RMS and average current conduction losses under any given operational conditions. The residual switching losses in “ZCS” series resonant power converters operating in the continuous current mode can be reduced by simple current snubbers placed in the commutation circuits. The experimental results confirm the theoretical predictions that the turn-on snubbers can reduce switching losses by about 1.5% at a switching frequency of 65 kHz