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Bipolar DC–DC converter plays an important role in data center and distributed renewable energy unit with the advantages of high efficiency and low cost. In order to improve the power density of bipolar DC–DC converter, a high frequency and high power density bipolar DC–DC converter based on Gallium Nitride High Electron Mobility Transistor (GaN HEMT) is proposed under the development trend of miniaturization, lightweight and high power density of power electronic converter. By using gallium nitride (GaN) switch device, the switching frequency of the converter is increased to 1 MHz, which effectively reduces the volume and weight of the device. In addition, through the design of high frequency driver circuit, two separate pull-up/pull-down outputs are provided for the control signal, and the rising and falling rates of the switch signal are controlled by adjusting the resistance to obtain good performance and driving stability. The experimental results show that the total weight of the converter with radiator is only 121.6 g, the power density is 35.23 W/in3, and the maximum efficiency can reach 92.7%. Compared with the same type of converter, the volume and weight of the converter are greatly reduced, effectively realizing the goals of miniaturization, lightweight and high power density of the converter.

A high-reliability SEPIC converter with reconfigurable voltage conversion gain is proposed, which is composed of a basic SEPIC converter and n extended units. Adopting an interleaved parallel structure on the input side of the converter not only achieves leg-level hardware redundancy but also reduces the input current ripple. When one branch of the converter suddenly changes or fails, due to the redundancy between branches, the converter can still to work, and the duty cycle of the other branches can be readjusted by using PI control without changing output voltage and power of the converter. This feature undoubtedly presents the reliability of the converter. On the contrary, when the converter works in normal operation, it can also actively control operation mode of each branch to achieve reconfigurable voltage conversion gain function. In addition, since the duty cycles of the switches are not limited, voltage conversion gain of the converter is widely, which makes it more suitable for the occasions where the input side fluctuates greatly. Section 2 details the working principle of the proposed converter and the voltage and current stress on components. Then, the reconfigurable voltage conversion gain of the converter and its high reliability characteristics are analyzed in Section 3. Finally, the correctness of the theoretical analysis is verified by experiments.