Single-Stage Switched-Capacitor Integrated DC Transformer for DC Distribution Networks

To avoid the centralized capacitor on the high-voltage side and reduce the power stage, a single-stage switched-capacitor integrated DC transformer (SCIDCT) with wide input voltage range and self-balancing is proposed. The proposed converter includes a boost inductor and N LC series resonant full-bridge modules, where the switched-capacitors are integrated to realize single stage. The switched-capacitors of adjacent modules are not directly connected in series, and the LC resonant tank of each module is located on the secondary side. The voltage gain of each module is a constant, which is only related to the transformer turns ratio. Therefore, the proposed SCIDCT realizes the input voltage sharing and output current sharing autonomously thanks to its DCT feature. Moreover, with the pulse frequency modulation, the maximum magnetic flux density of the high-frequency transformer is fixed under different switching frequencies, simplifying the transformer design. The soft switching of all secondary diodes and most primary switches can be realized with the help of the resonant tank. The operation principles of the proposed SCIDCT are analyzed. A three full-bridge module based SCIDCT prototype was built, and the proposed solution is well verified by the experimental results.