Critical output‐capacitor ESR for stability of V 2 controlled buck converter in CCM and DCM

Abstract

It has been reported that subharmonic instability exists in the V2 controlled buck converter in continuous conduction mode (CCM) when the duty ratio is above 0.5 (D > 0.5) and no stability issue exists in discontinuous conduction mode (DCM) when 0 < D < 1. However, the CCM and DCM instabilities will appear in the safe duty ratio range when the equivalent series resistance (ESR) of the output capacitor is below a critical value. The critical output-capacitor ESR for the stabiiity of a V2 controlled buck converter in CCM and DCM is investigated by using the discrete-time model and verified by circuit simulations.