Inductance Dual Model and Control of Multiphase Coupled Inductor Buck Converter
Daniel H. Zhou, Youssef Elasser, Jae-Il Baek, Charles R. Sullivan, Minjie Chen
Abstract
This paper presents an inductance dual model for designing coupled inductors in multiphase buck converters. The model is derived as a topological dual of the reluctance model of a multiphase coupled inductor, yielding an inductance-based equivalent circuit with simplified equations for evaluating the transient and steady state performance. The model clearly relates the magnetic geometry to a lumped circuit model, allowing visualization of coupling relationships and magnetic flux in SPICE. The model is conducive to state space and transfer function analysis. The dynamic equations of the M-phase coupled inductor buck converter are derived. It is revealed that the duty ratio to output voltage transfer function of a multiphase coupled inductor buck converter is equivalent to that of a single-phase buck converter. The inductance dual is leveraged to design a programmable coupled inductor that modulates the center leg reluctance to improve the control bandwidth.