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

It has been reported that subharmonic instability exists in the V 2 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 V 2 controlled buck converter in CCM and DCM is investigated by using the discrete‐time model and verified by circuit simulations.