A Dead-Beat-Controlled Fast-Transient-Response Buck Converter With Active Pseudo-Current-Sensing Techniques

Abstract

This paper presents a dead-beat-controlled (DBC) fast-transient-response buck converter with active pseudo-current-sensing techniques. The dynamic-slope control can compensate for the ramp slope to reduce subharmonic oscillation issue of the current-mode converter when the duty cycle is greater than 50%. The proposed active pseudo-current sensor can shorten the time of transient response, because it does not need a sample-and-hold circuit to eliminate spikes, and it can obtain inductor current information precisely. Thus, the DBC circuit including the dynamic slope generator and the proposed active pseudo-current sensor can compensate for the inductor current slope to stabilize the converter in one duty cycle when the output voltage is changed and can accelerate the transient response to achieve a better performance. The proposed converter has been implemented with TSMC 0.35- $\mu \text{m}$ CMOS 2P4M technology, and the chip area is 1.5 mm $\times \,\, 1.5$ mm (including PADs). The operating frequency is 1 MHz, the maximum output current is 600 mA, and the peak power efficiency is 89% under 200-mA load current. The output voltage range is from 0.8 to 2.5 V, and the fast transient responses are $2~\mu \text{s}$ from light load to heavy load and from heavy load to light load. This buck converter also has the characteristic of low output ripple.