2.5 MHz谐振频率GaN基LLC谐振变换器设计

GaN-based LLC resonant converter with a 2.5 MHz resonant frequency

直流-直流变换器是航天二次电源的核心部件之一,体积小、重量轻、高功率的变换器是航天电源未来发展的趋势。提高变换器开关频率是缩减整机体积与重量、提升变换器性能的重要手段,所以,“高频化”是未来直流-直流变换器的重要发展趋势。使用GaN高电子迁移率晶体管作为开关器件,研究了在电路实现软开关的情况下,特定GaN器件对LLC谐振变换器可实现的最大工作频率的影响。研究发现,在保持软开关特性的情况下,GaN器件的输出电容越小,作为LLC谐振变换器的开关器件时可以使变换器实现的最高频率越大,但是GaN器件本身的损耗也会随之增加。针对损耗与高频的折衷关系,建立了精确的GaN器件损耗模型,为效率最优方案提供参考。并针对270 V输入、28 V输出、200 W额定功率的GaN基LLC谐振变换器做出了详细分析,通过使用GaN器件实现了2.5 MHz的高频变换器,整机功重比达到3.1 kW/kg,转换效率峰值为92.8%。原理样机验证了该设计方法可以实现更高频的LLC变换器,为未来制作高频变换器提供了设计参考。

The DC-DC converter plays a pivotal role in secondary power supplies for aerospace applications.The ongoing development trend for aerospace power supply converters emphasizes compact size,lightweight,and high-power output.To achieve these goals,enhancing the“power-to-weight ratio”and increasing the switching frequency are critical strategies.Notably,the pursuit of higher frequencies is a significant focus for future DC-DC converters.In this paper,GaN(Gallium Nitride)based HEMTs(High Electron Mobility Transistors)is employed as a switching device to investigate the impact of device characteristics on the maximum achievable operating frequency when the LLC resonant converter operates in the soft-switching mode.It is found that reducing the output capacitance of GaN devices leads to higher switching frequencies.However,it is essential to consider the tradeoff between frequency and power losses.To address this problem,we establish an accurate loss model for GaN devices,providing valuable insights for optimizing efficiency.Finally,a 200W 270 V~28 V LLC resonant converter is realized and the detailed analysis is carried out.By utilizing GaN devices as a switching component,a high-frequency converter operating at 2.5 MHz is achieved.The resulting power-to-weight ratio reaches 3.1 kW/kg,with a peak conversion efficiency of 92.8%.Our prototype validates the feasibility of designing higher-frequency LLC converters,and provides a design reference for the future production of a high-frequency converter.