Sub-resonant series resonant converter having improved form factor and reduced emi

摘要

The converter includes a resonant tank circuit which is coupled to a load circuit. Current is supplied from a unipolar source to the load circuit. The resonant tank circuit includes resonant tank elements defining a dominant resonant frequency. Current is supplied to the tank circuit through alternately activated switching devices provided in a bridge inverter circuit. The switching devices are activated at a switching frequency lesser than the dominant resonant frequency of the tank circuit. During the positive half cycle current is supplied to the tank circuit through the activated switching device. During the negative half cycle the current in the tank circuit is reversed by an antiparallel shunting diode. The resonant tank elements have a series combination of a first inductor (L2) and a first capacitor (C1). An additional capacitor (C2) is connected in series with the first capacitor and the first inductor. A boost inductor (L3) is parallelly connected to the additional capacitor. A load is connected parallelly across the additional capacitor. The additional capacitor draws current due to which the form factor of the supplied current is reduced. The negative half cycle of the supplied current is reduced so that reverse current through the antiparallel diode of one switching device is terminated.