A novel passive lossless soft-switching snubber for PWM inverters

This paper presents a novel passive lossless snubber circuit for pulse-width modulation (PWM) inverters to achieve soft-switching purposes without an extra switch and additional control circuitry. This novel passive lossless soft-switching snubber employs an inductor/capacitor snubber circuit for each switching device in an inverter to achieve passive zero-current turn on and zero-voltage turn off. Furthermore, instead of conventional bulky transformer coupling for energy recovery, three inductors coupled tightly on a single core are used to losslessly recover snubber energy to the input in the proposed snubber. In addition, freewheeling of output phase current of inverters can be realized via energy storage components in the snubber in the dead-time and the effect of dead-time is reduced. The distortion ratio of the output phase current in low output frequency is also reduced. All components in the snubber circuit are passive, thus having a better price/performance ratio than their active counterparts. The snubber has been incorporated into a PWM inverter. Experimental results are given to demonstrate the validity and features of the snubber circuit.