Small Signal Analysis of V2 Control Using Equivalent Circuit Model of Current Mode Controls

In $V^{2}$ control, the direct feedback contains the information of the inductor current, the capacitor voltage, and the load current. In this paper, by separating the current feedbacks and the capacitor voltage feedback, an equivalent circuit of $V^{2}$ control with ESR dominant output capacitor is proposed. The proposed equivalent circuit is based on the unified equivalent circuit of current mode controls. It is a completed frequency domain model for $V^{2}$ control with a clear physical insight. $V^{2}$ control can be interpreted as an advanced implementation of current mode control with a proportional voltage feedback and an additional load current feedback. The load current feedback dramatically reduces the output impedance of a current mode controlled converter. The model is extended to the enhanced $V^{2}$ control. The proposed model is applicable to both variable frequency modulations and constant frequency modulations. The modeling results are verified by the Simplis simulation and the experimental results.

I. Introduction

V control, which features simple implementation, and ultrafast transient response [1], is a popular control scheme for low-power point-of-load Buck converter in recent years. The architecture of control is shown in Fig. 1. The output voltage is directly fed back to the pulse-width modulation (PWM) comparator and compared with the control signal , which is the output of the outer slow integral loop. Since the output voltage ripple is used as the PWM ramp, it is also referred to as “ripple based control” [2].