A Fast Response PWM Buck Converter With Active Ramp Tracking Control in a Load Transient Period

This brief proposes a pulse-width modulation buck converter with an active ramp tracking control to achieve a fast load transient response. When the difference between the output voltage and reference voltage is increased to a certain level in the load transient situation, the ramp bias voltages track the error voltage and provide a full duty to power switches. This helps restore the output voltage to the reference voltage, improving the load transient response speed and decreasing the overshoot/undershoot and their recovery times at the output voltage. A test chip was fabricated in a 65-nm CMOS technology, whose performance evaluation results indicated that the proposed buck converter reduced overshoot/undershoot at the output by up to 61.1% and the recovery time by up to 60.0% for a 450-mA load current step. The maximum power conversion efficiency of the proposed converter is 92.0% for 3.3 V input voltage and 1.8 V output voltage.