| When we develop a DC-DC converter for the aerospace applications, optical-coupler is forbidden to improve the reliability. In order to realize isolated control, magnetic feedback and isolated driving methods are employed, however, they have some demerits such as complex control, difficult self-starting, and low dynamic response.This thesis proposes a two-stage approach for the DC-DC converter. Half-bridge converter is adopted as the first stage, it is open-loop controlled with full duty cycle, achieving isolation and voltage step-down, just like a DC transformer. Buck converter is taken as second stage, it is closed-loop controlled, achieving the precise regulation of the output voltage. Synchronous rectification is used in the Buck converter to increase the efficiency. In order to increase power density, multi-layer PCB and planar transformer technologies are involved, and the winding arrangement is discussed. A prototype with 80V-120V input and 3.3V/10A output is fabricated and tested to verify the effectiveness of the two-stage DC-DC converter.In order to improve the electromagnetic compatibility of the DC-DC converter, a electromagnetic interference (EMI) input filter is developed. Based on the basic EMI filter structure, the thesis focuses on the analysis of the parasitic couplings among the components, which affect the filter's performance, especially in high frequency range. With circuit decoupling methods, the approaches to improve EMI filter's high frequency performance are discussed. A prototype is fabricated and tested, and the experimental results are included to show the excellent performance of the EMI filter. |
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