Fast Transient (FT) Technique With Adaptive Phase Margin (APM) for Current Mode DC-DC Buck Converters

Abstract—This paper proposes a fast transient (FT) control with the adaptive phase margin (APM) to achieve good transient re-sponse in current-mode DC-DC buck converters at different load conditions. The overshoot/undershoot voltage and the transient re-covery time are effectively reduced. The APM control can always maintain the system phase margin at an adequate value under dif-ferent load conditions. That is, the compensation pole-zero pair is adapted to load current to extend the system bandwidth and get an adequate phase margin. Experimental results show the over-shoot/undershoot voltage is smaller than 60mV (3%) and transient period is smaller than 12 s as load current suddenly changes from 100 to 500 mA, or vice versa. Compared with conventional designs without any fast transient technique, the undershoot voltage and recovery time are enhanced by 45 % and 85%, respectively. Index Terms—Adaptive phase margin (APM), fast transient (FT), loop bandwidth, pole-zero cancellation, stability. I