Fast response controller for a stepping inductance based voltage regulator module

Abstract

Voltage Regulator Modules (VRM) have stringent efficiency and transient response requirements. A promising Stepping Inductance based VRM (SI-VRM) has been proposed in the literature with the aim of achieving fast dynamic current response under step-load conditions. In the SI-VRM topology, the output inductor changes from a comparatively high value to a small value during load-induced transients. This feature has the potential to achieve good performance both under steady state and under transient conditions. However, the scheme proposed in literature to control the SI-VRM has shortcomings. In this thesis, a control scheme is proposed for the SI-VRM which can achieve fast transient response, smooth transition between different operating states and low ripple voltage both under normal and inductor current recovery conditions. The averaged model of the converter is verified by experimental results. Based on this model, a dual-gain voltage controller is proposed which exploits the higher switching frequency of the converter during load-induced transients to achieve better transient performance. The thesis also investigates the relationship between the parameters of the stepping inductance and the steady-state and transient performances of the converter and provides guidelines for the choice parameters of the stepping inductance. Finally, experimental results are provided to confirm the expected improvements in performance with the proposed control method.