Research On A Five-element Resonant Converter

HVDC 270 V power supply is usually applied to All-Electric-Aircraft, but many aircraft electrical devices can not directly use it, so it is necessary to study buck DC/DC converter with DC270 V input.LLC resonant converter is widely used in many applications because it can achieve ZVS turn on for primary switches and ZCS turn off for secondary switches in a wide load range. However, it's hard to limit the current of LLC resonant converter under the conditions of overload, so a five-element resonant converter is adopted which adds a notch filter to LLC resonant converter to make the voltage gain drop quickly even to zero as the working frequency increases in the high working frequency range.Firstly, this paper introduces the voltage gain and working principle of LLC resonant converter, and analyzes the reason why it's hard to limit the current. Secondly, based on the analyses of LLC resonant converter, the voltage gain and working principle of the five-element resonant converter is presented from which we can find that it can not only achieve ZVS turn on for primary switches and ZCS turn off for secondary switches under wide load conditions but also control current efficiently by increasing switching frequency. Thirdly, this paper gives the design of circuit parameters and conducts simulation by using the designed parameters to verify the theoretical analyses. Finally, experimental prototype is developed and the experimental results verify the accuracy of the theoretical analyses.