Peak current mode-controlled pulse width-modulated active clamp forward converter with centre tap transformer

Abstract

This paper presents the control to output transfer function, principles and performance of peak current mode-controlled active clamp forward converter with centre-tap transformer. There is a clamp circuit comprising of one auxiliary switch and one clamp capacitor, which is used in the forward converter to recycle the energy stored in the magnetising inductor. Due to presence of clamp circuit, the active clamp forward converter with centre tap transformer exhibits fourth-order power stage dynamics. The current mode control is implemented to enhance the performance of the converter by sensing the main switch current. It is demonstrated that current loop gain splits not only the complex-conjugate pole of the output filter but also the complex-conjugate pole pair formed by clamp circuit into real poles. Different transfer functions are derived using state space average model. The peak current mode control is implemented experimentally using controller IC, UCC2891D, and the simulation results are verified with the experimental setup.