Active-clamping quad-flyback converter

An active-clamping quad-flyback converter is proposed to achieve zero voltage switching (ZVS) for all power switches. The secondary sides of quad-flyback converter are connected in parallel to share the load current. Thus, the transformer copper losses and the conduction losses on the output diodes are reduced. Active-clamping part including one auxiliary switch and one clamp capacitor can release the energy stored in the magnetizing and leakage inductances such that the voltage stress of main switch is clamped and main/auxiliary switches can be turned on at ZVS. In the proposed circuit, the constant switching frequency with asymmetrical PWM waveform is generated to realize the ZVS turn-on of switches at the transition interval between main and auxiliary switches. Thus, the switching losses and thermal stresses of the semiconductors are reduced. The operation principle, system analysis and design consideration of the proposed converter are discussed in detail. Finally, a prototype of the proposed converter is implemented by 200 V input voltage, 48 V output voltage, 480 W output power and 90 kHz switching frequency to verify the theoretical analysis and the effectiveness of the proposed converter.