LAUSR

This article presents the feasibility of a flyback charger for electric vehicles (EV) based on silicon-carbide (SiC) devices. The flyback topology is simplest, but its device voltage stresses are strongly affected by the transformer leakage inductance. To reduce the device voltage stresses by recovering the energy stored in the transformer leakage inductance, an active-clamp circuit and active snubber circuit are adopted in both sides of the transformer. Also, the active-clamp circuit helps to reduce the switching losses by making zero-voltage-switching (ZVS) condition. By deriving the loss equations of switching devices and transformer as a function of the switching frequency and magnetic flux swing, design optimization considering loss and volume is attempted. The snubber capacity and diode voltage stress are quantitatively suggested through the analysis of the power absorbed by the active snubber. Based on the analysis, a 3.3 kW/100 kHz prototype is designed and experimented to show the feasibility. Test results demonstrate 96.7% peak efficiency and 96.4% full load efficiency at 330V output voltage.