Adaptive Nonlinear Compensation for Asymmetrical Half Bridge DC-DC Converters

Abstract

Asymmetrical half-bridge dc-dc converter has favorable features, which allow the converter to operate at higher frequencies with higher power density. However, asymmetrical half bridge dc-dc converter displays nonlinear dc gain variation with input voltage and duty cycle. The conventional compensator design is based on a small-signal transfer function of power stage and worst case has to be considered in the closed-loop design. With the variation of input line, the system loop gain deviates from the nominal designed trajectory, and correspondingly, the system bandwidth, phase margin and gain margin are going to vary with input voltage line. As a result, the system steady-state and dynamic performance are affected as well. This paper proposes an adaptive nonlinear compensation approach to adjust the system loop gain dynamically and thus achieve unified system loop gain, bandwidth and performance. The adaptive digital compensation algorithm is simulated and verified based on PSIM simulation software.