Abstract
This thesis presents design and implementation of an isolated two-stage dc/dc converter with division-summation (D-Σ) digital control. The first stage is a buck converter, and the second stage is a full-bridge converter with current-doubler rectifier which is controlled with phase-shift switching method. Therefore, the primary-side power devices can achieve zero voltage switching. With D-Σ digital control, the converter is allowed to have wide inductance variation caused by high current flowing through inductor, and to track current reference precisely for achieving tight output voltage regulation. This paper derives D-Σ control law for dc/dc converter in detail, and initiates the application of D-Σ control in DCM operation. The major contributions of this paper is: this research applies D-Σ digital control on dc/dc converter unprecedentedly, and verify that the control can reduce steady-state error as compared with peak current-mode control and achieve faster dynamic response over average current-mode control. Moreover, it presents a modified D-Σ control law for DCM operation to enables the applicability of the control in both CCM and DCM operation. Last, the research implements a high voltage step-down dc/dc converter with input voltage 600 V, output voltage 26 V and power rating 2.6 kW.