A low-cost soft-switching high step-up flyback converter with stacked output cells

A low-cost isolated high step-up dc-dc converter with a single switch and multiple output cells is proposed. The magnetizing inductance of the multiple-winding transformer and a multitude of capacitors are used to form a parallel LC resonant link. The capacitors create a Zero Voltage Switching (ZVS) condition at turn-on and turn-off and reduce the switching losses of the switch and diodes. Rate of voltage change (dv/dt) on all semiconductors is limited by the link capacitors, and the diodes turn off with suppressed reverse recovery transients. The converter requires no auxiliary clamps or switches to achieve soft-switching. An analytical approach is developed to establish a relationship between link parameters, input and output voltages, and link frequency. Experimental results on a 60 V to 600 V converter at 250 W are included to corroborate the design and operation.