Design of high efficient point-of-load DC/DC converter using enhancement-mode gallium nitride high electron mobility transistors (HEMTs)

In this study, the design of 1MHz switching frequency and 25W output power level 28 to 3.3V non-isolated point of load converter which uses enhancement mode gallium nitride transistors as switching element is realised. In order to decrease the size and increase power density of the point of load converter, the converter is switched at high frequency. Furthermore soft switching technique is used to increase the efficiency of the converter. Quasi square wave zero voltage (QSW-ZVS) indirici converter is used as power topology in the converter. To achieve soft start, the output filter inductor and output capacitances of GaN transistors are used for resonance rather than the use of discrete passive elements. A prototype of the converter that is designed theoretically and simulated, was made and tested succesfully in laboratary test setup. The design requirements of the converter were met and 88.8 % efficiency was obtained from the converter at full load. In order to use the converter in the satellite applications, the total ionization dose effects to the GaN transistors caused by the radiation in the space environment is investigated in gama radiation tests. The decrease in the gate threshold voltages of the transistors is observed based on the radiation dose amounts.