Extension of bandwidth of two-stage DC-DC converter with low-voltage / high-current output

This paper presents the fast transient response improvement of a two-stage DC-DC converter by using the current feedback control. The two-stage converter consists of a buck converter used as the first stage and a half-bridge converter used as the second stage. The proposed control system using the first-stage inductor current and the conventional voltage-feedback control system are analyzed and compared. As a result, it is analytically clarified that the crossover frequency becomes higher by adding the first-stage inductor current in the feedback control loop. The experimental confirmation was obtained with a good agreement, and the effectiveness of the proposed control strategy was verified.