High Efficiency High Power Density Double-Clamp ZVS Flyback Converter With Secondary Absorption

The double-clamp zero-voltage-switching (DCZVS) flyback converter can achieve high efficiency and high power density through high-frequency soft switching and inherent primary side regulation (PSR) feature. However, conventional resonance schemes for DCZVS flyback converters fail to simultaneously enable lossless leakage inductance energy recovery and high-precision PSR. In this article, a secondary absorption scheme is proposed for the DCZVS flyback converter, which employs the output capacitance of secondary-side synchronous rectifier switch to achieve lossless absorption of leakage inductance energy. Furthermore, the secondary absorption scheme reduces the voltage ripple of the clamp voltage and enhances PSR accuracy. The proposed scheme is validated on a 160-420 V input and 28 V/600 W output prototype. Compared with the highest power density level at present, the experimental prototype achieves a peak efficiency of 94.37% with an increase of 0.68% and achieves an ultra-high power density of 1290 W/inch(3) with an increase of 7.2%.