Current-mode control is frequently used in dc-dc buck converters. Many current-mode buck converters apply type-II compensators for obtaining high loop gain to reduce the steady-state error and maintaining the loop stability with restricted bandwidth. However, when large load-current transients occur, significant transient undershoot/overshoot is generated due to the restricted loop bandwidth. In response, a type-II compensator with the proposed voltage-setting control (VSC) is presented in this paper. By simply setting the voltage of the compensation capacitor and the input voltage of the compensator, the proposed VSC, which is activated by a transient detector, greatly suppresses the transient undershoot and overshoot. Implemented in 0.35μm CMOS process, this work occupies 0.91mm2 including pads, and features a peak efficiency of 96.3%. With the proposed method, the maximum undershoot and overshoot are respectively suppressed from 150mV to 58mV and 92mV to 62mV for ± 1A load current steps.
['Pai-Yi Wang', 'Szu-Yu Huang', 'Kuan-Yu Fang', 'Tai-Haur Kuo']
An undershoot/overshoot-suppressed current-mode buck converter with voltage-setting control for type-II compensator