Loop bandwidth extension technique for PWM voltage mode DC-DC switching converters

Abstract

A loop bandwidth extension technique for voltage mode pulsewidth modulated DC-DC switching converters operating in continuous conduction mode is proposed. The conventional fixed ramp is replaced by a ramp with a variable slope adjusted by the output voltage through a low power and area-efficient transconductance cell, pushing the complex pole pair of the LC filter to a higher frequency and hence improves the system loop bandwidth. Theoretical analysis is presented. A prototype buck converter with a maximum load current of 50mA is fabricated using a 0.35μm CMOS process, occupying an active area of 0.095mm2. Experimental results show that the proposed converter has reduced transient overshoot and undershoot, and settling times are reduced by 50% compared to a conventional voltage mode buck converter. The results match well with the theoretical analysis.