A circuit-oriented geometrical approach in predicting subharmonic oscillation of dc-dc converters with voltage-mode control

This paper presents a circuit-oriented geometrical approach in predicting subharmonic oscillation of DC-DC converters with voltage-mode control. It is based on straightforward graphical analysis of the operation of the converter without using sophisticated mathematical tools. The critical condition of subharmonic oscillation of the buck converter is derived, which is shown to be related to the slope of the output of the compensator V_ea at the trip point rather than the amplitude of the ripple voltage of V_ea. The proposed analysis is verified for converters with a proportional or a Type-III compensator.