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Wide Range and High Power Density GaN-Based DC-DC Converter Design

Fig. 1. Topology
The ability to deal with a wide input voltage range and maintain a high efficiency are two criterions for a DC-DC converter. In this work a high power density converter is designed using a GaN device that switches at 1MHz in order to minimize the volume and maximize the efficiency. Figure 1 shows the topology structure which is a revised three-switch active-clamp flyback converter. The design starts by using theoretical calculations and a simulation analysis with loss modeling to evaluate the performance. Then, the converter board test follows to verify functions and provide guidance for further design and optimization.

Since the input voltage of the converter ranges eight times, it brings more pressure on the devices to produce a fixed output voltage regulation. The proposed topology eases the voltage stress on the main switches which also gives more design freedom for the transformer. According to the high power density requirement, the power loss mainly comes from switching loss and the transformer's (winding plus core) loss so this topology can provide a better performance potential when compared to the other two-stage converters. Although this structure needs more components and circuits to do the driving functions, the total volume can still be relatively small with the help of an embedded transformer. The first version of the embedded transformer is in the design and test process to get the best performance and match the converter specifics. The converter non-integrated test board is designed and made for the test. Then a more reliable and controllable converter will follow and add the integration technique.

Fig. 2. Transformer