An Active Clamp Flyback Converter With High Precision Primary-Side Regulation Strategy

The active clamp flyback (ACF) converter has been widely adopted because of the feature of isolation, soft-switching, and high conversion efficiency. On the other hand, due to the characteristic of the circuit cost reduction and the fast control response, the primary-side regulation (PSR) has become a popular control method for isolated power converters. However, high precision PSR strategies for ACF converters are not exposed. Therefore, the aim of this article is to propose a high precision PSR strategy for the ACF converter. Relations between the primary-side current and the secondary-side current are analyzed and derived. Both of the continuous conduction mode operation and the discontinuous conduction mode operation will be considered. The output voltage control mode or the output current control mode can be selected via the proposed strategy. In addition, a secondary-side losses compensation (SSLC) strategy is developed to deal with the non-ideal circuit characteristics as well as to enhance the control accuracy. Operational principles and thorough mathematical derivations will also be revealed. Finally, both simulation and experimental results obtained from a 100 W prototype circuit demonstrate the performance and feasibility of the proposed PSR and SSLC strategy. Validations show that the control accuracy of the output voltage and the output current are 98.54% and 98.42%, respectively.