Current mode DC-DC buck converters with optimal fast-transient control

A load dependent proportional-integration (PI) compensation is proposed in this paper for minimizing transient dropout voltage and accelerating the transient response of current mode DC-DC converters. The adaptive compensation resistance and capacitance are used to react to the sudden load variations: At the beginning of load transient response, the adaptive compensation capacitance is decreased to move the compensation pole-zero pair to a higher frequency for achieving fast transient response. At the end of load transient response, the pole-zero pair is moved back to an optimal position for extending the system bandwidth and phase margin based on the instant load condition. Simulation results demonstrate the excellent performance at transient period and steady-state with this proposed fast transient control and adaptive pole-zero compensation. The overshoot/undershoot voltage is smaller than 45mV and transient period is shorter than 15us as load current suddenly changes between 100mA and 500mA.