Snubbers for the distributed interwinding capacitance in high-output-voltage converters

In high-output-voltage full-bridge power converters, the ringing in the rectifier circuit is usually linked with the reverse recovery of the high voltage diodes and the leakage inductance of the transformer. The superimposed reverse recovery voltage spike of the rectifiers is one of the parameters that limits the practically achievable output voltage. However, the effect of the interwinding capacitance can contribute considerably to the ringing, specially when the number of secondary turns is large. This paper analyzes the effect of the interwinding capacitance using a 1.2 kW full-bridge phase-shifted DC/DC power converter with a maximum output voltage of 600 V. A snubber is proposed that reduces the ringing caused by the interwinding capacitance. This snubbing method is applicable to transformers as well as inductors that have a dominant interwinding capacitance.