A simple constant-frequency nonlinear controller to enhance transient response in the half-bridge with current-doubler rectifier

The half-bridge converter with current-doubler rectifier (HB-CDR) and synchronous rectification is a promising topology to implement new voltage regulator modules (VRMs). In this paper, a novel control scheme is proposed for this converter. Firstly, a large-signal bilinear model is derived, and a steady-state analysis is done in order to study the static performances of the HB-CDR. Secondly, by using the bilinear model a nonlinear feedforward controller is obtained. The proposed controller provides the following features: fast transient response, fixed switching frequency, and high robustness against load and input voltage disturbances. Furthermore, this controller avoids the use of any current sensor and can be implemented by means of cheap analog circuits, which highlights its low-cost and simplicity. Finally, simulation results are provided in order to show the validity of the proposed control technique.