Lossless DCR current sensing for multi-winding coupled inductors

Abstract

Lossless DCR current sensing is common in multiphase point of load converters. A multiphase buck with coupled inductors exhibits a larger steady state inductance than transient inductance. Since there are two distinct values of inductance, it unclear which value to use in the conventional DCR sensing scheme. A first assumption might be to use the transient inductance, so that closed loop stability is not compromised. The current slew will be measured accurately, but the measured ripple magnitude will be incorrect. Accurate measurements of both the ripple and the current slew of coupled inductors cannot be produced using conventional DCR sensing. This paper proposes a new DCR sensing scheme that resolves the inaccuracies of conventional sensing.