Soft-Switching Auxiliary Current Control for Faster Load Transient Response of Buck Converter

A control method for the auxiliary buck/boost converter is proposed to improve the load transient of the buck converter. The proposed technique maximizes the efficiency of the auxiliary converter by enabling the soft switching operation. The proposed control is free form complicated arithmetic operation, digital sampling, and load prediction, and is realized by simple analog components only. The design guidelines for achieving capacitor charge balance of the output capacitor during the transient are also presented. The simulation results revealed that the output voltage overshoot and settling time during the load step-down transient were 62 mV and 29.4 μs, respectively; however, in the case of conventional time-optimal control, these values were 666 mV and 57.2 μs, respectively, under the same condition. The prototype buck converter of which is input is 15 V, output is 3.3 V, switching frequency is 200 kHz had been built to prove the performance and effectiveness of the proposed technique.