Fast Transient Technique and Adaptive Phase Margin Control for Current Mode DC-DC Buck Converters

• Main Authors: Lee, Yu-Huei, 李昱輝
• Other Authors: Chen, Ke-Horng
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/64591111535900245083

碩士 === 國立交通大學 === 電機與控制工程系所 === 97 === This paper proposes a fast transient (FT) control with adaptive phase margin (APM) to achieve good transient response of current-mode DC-DC buck converters at any load condition. Thus, the overshoot/undershoot voltage and the transient recovery time are effectively reduced. Owing to the load-dependent output pole of the current-mode buck converters, the operation of a load-dependent compensation pole-zero pair is designed to be moved to a higher frequency at transient period and back to an optimum position for pole-zero cancellation in steady state. Therefore, an adaptive phase margin is always maintained at a suitable value in all load conditions for achieving good transient responses. In other words, the compensation pole-zero pair is adapted to the load current to extend the system bandwidth and get the optimum phase margin. Experimental results demonstrate the improved transient performance at transient period and good phase margin in steady state. The overshoot/undershoot voltage is smaller than 60mV and the transient period is shorter than 12μs as the load current suddenly changes from 100mA to 500mA, or vice versa. Compared with the conventional design without any fast transient technique, the performances of undershoot voltage and recovery time are enhanced 45 % and 85 %. With the proposed technique, the performance of the current-mode buck DC-DC converter is improved significantly.