High Precision Primary Side Regulation Constant Voltage Control Method for Primary and Secondary Resonant Active Clamp Flyback Converter

Active clamp flyback (ACF) converter has been demonstrated that which is better than traditional flyback in high-frequency power-adaptor applications. According to the circuit structure, ACF has two modes, primary resonant ACF (PR-ACF) and secondary resonant ACF (SR-ACF). In order to improve the power density, a high-precision primary side regulation (PSR) constant voltage control method for ACF converter is proposed in this article. The proposed method not only can be effectively adopted in PR-ACF but SR-ACF converter. The high-precision output voltage is predicted by highly accurate sampling points on primary auxiliary voltage. The applied microcontroller environment improves the practicability and increases the power density of the ACF system. To verify the proposed PSR method, a prototype that can be changed into PR-ACF and SR-ACF is designed. The output voltage offset, operation efficiency, and dynamic performance are analyzed. The tested results show that high-precision output is obtained in ACF converter by using the proposed method and the maximum output voltage deviation which are 4% and 3.5% in PR-ACF and SR-ACF converter, respectively. Moreover, SR-ACF has a higher efficiency compared with PR-ACF converter, and a smaller voltage shoot during dynamic process, which needs a larger regulation time since the additional output inductor.