Unified equivalent circuit model of V2 control

V2 control and its variety named ripple-based control, are popular control schemes in point-of-load Buck converters and Voltage Regulators for microprocessor. This control scheme is elegant when output capacitors with sufficient ESR are employed, such as OSCON capacitors. However, in most cases with small-ESR capacitors, such as ceramic capacitors, instability problem will occur. Up to now, no equivalent circuit model is proposed which is able to predict instability issue. This paper proposes a unified equivalent circuit model which is suitable to all kinds of capacitors by considering the effect of both inductor current ripple and capacitor voltage ripple. The equivalent circuit model is a simple yet accurate, complete model and can be used to investigate all transfer functions. The proposed equivalent circuit model is applicable to both variable frequency modulation and constant frequency modulation. Furthermore, the model can be extended to enhanced V2 control and muti-phase V2 converters. The equivalent circuit model is verified with Simplis simulation and experimental results.

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