Auxiliary Parallel Inductor Switching Control for Improving the Load Transient Response Performance of Buck Converters

This brief proposes an auxiliary parallel inductor switching control (ISC) scheme for buck converters to improve the transient response caused by load steps. During a transient period, an auxiliary inductor is connected with the buck converter in parallel to decrease the equivalent inductance, so as to increase the slew rate of the inductor current. In the steady state, the auxiliary inductor is switched out of the main circuit to ensure an expected ripple content in the steady state. Also, the switching moment of the auxiliary inductor during the transient period is derived based on the capacitor-charge balance principle. Finally, the proposed ISC scheme implemented by a digital processor and analog circuits is applied to a 30 V-15 V buck converter prototype. Experimental results show that the settling time and the voltage deviation are improved by 45% and at least 35.5%, respectively, for a load step 4.5 A compared to the time-optimal control.