The Resonant Characteristics Comparison between Primary-Side Resonant and Secondary-Side Resonant Active Clamp Flyback

Abstract:
The use of Active Clamp Flyback (ACF) has become popular in high frequency, high power density, low power applications, such as mobile charging adapters and server auxiliary power for its ability to enable faster switching speeds, smaller sizes and improved efficiency. There are two types of ACF: primary-side resonant ACF (PSR-ACF) and secondary-side resonant ACF (SSR-ACF). While the circuit diagrams are almost identical, there are key considerations for choosing one over the other. This paper shows a detailed comparison of PSR-ACF and SSR-ACF, and highlight opportunities for design optimization when the resonant characteristics of PSR-ACF and SSR-ACF are fully understood.