Multi-Period Frame Transient Switching Control for Low-Voltage High-Current Buck Converter With a Controlled Coupled Inductor

This paper presents a multi-period frame transient switching control (MP-TSC) scheme for buck converter with a controlled coupled inductor, aiming at improving the load transient response. The proposed buck converter utilizes a controlled coupled inductor as the output inductor. During a load transient, the coupled inductor is controlled as a small equivalent inductance so as to achieve fast transient regulation. While in the steady state, the coupled inductor behaves as a large inductance to reduce the output current ripple. Furthermore, on the basis of the proposed variable inductance circuit, an MP-TSC control scheme is proposed and implemented in a digital form. With the proposed control scheme, the load transient event is divided into n + 1 sub-periods, and in each sub-period, the capacitor-charge balance principle is used to determine the switching time sequence. Moreover, the control principle design and transient response index analysis are provided. Furthermore, its feasibility is validated in simulation and experiment with a 12-3.3V low-voltage high-current synchronous buck converter. Experimental results demonstrate that the voltage deviation of the proposed MP-TSC scheme (coupled coefficient of the controlled coupled inductor is 0.52) has improved by more than 79% compared to that with the auxiliary circuit disabled.