Feedforward current control of boost-derived single-phase PFC converters

The recently developed input current feedforward control method for boost single-phase PFC converters is generalized and applied to other, boost-derived topologies. The generalized method is applicable even when additional resonant and active clamping circuits are added to achieve soft switching in the converter power stage. The feedforward duty ratio signal in the generalized method is calculated based on the off-state voltage of the main switch instead of the output voltage as in the existing method. Measuring the switch off-state voltage requires a sample-and-hold circuit, which is best accomplished by using digital control. Applications of the proposed method to a transformer-coupled SEPIC converter with active clamping and its digital implementation are presented in detail. Numerical simulation and experimental results are reported to demonstrate the benefits of the proposed method and its suitability for different applications.