Modeling and autotuning of AVP control with inductor DCR current sensing

A new equivalent circuit model is presented to predict the small-signal characteristic of current-mode control with DCR current sensing accurately, and a simple auto-tuning method is proposed to solve the issue of time constant mismatch in DCR current sensing. The model shows that the mismatch between the current sensing RC network and the output inductor makes the output impedance deviate away from desired load-line resistance, so the transient response impairs. Adding more output capacitors can avoid transient spike, but increase component cost. Prior autotuning method solves mismatch issue by adjusting the time constant of RC network close to another such that output capacitors can be reduced, but the implementation is too complex for monolithically integration. Therefore, this paper develops a simple pole-zero compensation technique to maintain constant output impedance and fast transient under possible mismatch conditions, so output capacitor can be minimized with simpler autotuning circuit on VR controller. The SIMPLIS simulation with state-of-art output filter model of laptop VR and the experiment result on a commercial VR12 controller confirms the effectiveness of the proposed autotuning method.