Design and analysis of four-phase synchronous buck converter for VRM applications

A four-phase synchronous buck converter is designed and analyzed with an emphasis on the variation of R_DS-on and C_GS of the power MOSFET, and the ESR of the filter inductor. As the R_DS-on of the device decides the voltage drop across the device, and C_GS of the device decides the switching transients, both of these play a role in the efficiency of the multiphase converter. It is shown that, devices of same rating and make may have different performance characteristics, which do affect the efficiency of the converter. Even the inductors of the same rating though expected to behave in the same way, may not literally have the same effect when connected in different phases. In this paper a four-phase buck converter and its performance with and without variation of R_DS-on, C_GS and ESR of the filter inductors are analyzed and presented.