Active Dead-time optimization for wide range Flyback active-clamp converter

The Flyback Active-clamp topology can work on a wide input voltage range. But the parasitic capacitor of the main MOSFET used in the soft switching is affected by the input voltage variation and then reduces the efficiency of the converter. In this article, the strategy used to maintain an optimal valley switching by adapting PWM dead-times is described. We have tested our strategy on a 20 V to 120 V input I 30 W converter operating at 200 kHz We have obtained a 2% efficiency increase above 60 V compared to a fixed dead-time control.