Discrete-time modeling of switching converters including intra-cycle waveform propagation

This paper proposes a small-signal model for variable-switching-frequency hysteretic converters operating in CCM (Continuous Conduction Mode) and DCM (Discontinuous Conduction Mode). The model is capable of predicting flip bifurcation phenomena when the hysteretic converter operates below the CCM/DCM boundary. A comparison with exact simulations is provided to validate the proposed model. The propagation delay of the feedback control circuit is included due to its significant influence on the low-frequency open-loop gain. Experimental results run on a test-chip including a 10MHz TSMC-0.18μm-process hysteretic-mode buck converter are also reported along with the model results.