MHz级应用下GaN器件损耗机理及损耗抑制技术

The Gallium Nitride (GaN) devices have better high-frequency performance than traditional Silicon devices, so the applications of GaN devices are expected to increase the switching frequency of the power converters to MHz range, thereby significantly increasing the converters’ power density. However, studies have shown that in the case of MHz applications, the loss mechanisms of GaN devices are much more complicated than that in low-frequency case. The losses are often much larger than the theoretical results, and even up to an order of magnitude, which becomes the bottleneck limiting the improvement of the converters’ efficiency and power density. Therefore, it is of great significance to study the loss mechanism and loss suppression technology of GaN devices in MHz applications. This project is intended to study the unique or significant loss problems of GaN devices in MHz applications, including AC on-resistance characteristics, high-frequency dynamic on-resistance effects, output capacitance loss characteristics, and equivalent body diode characteristics. The purpose is to find out the variation laws of losses with various parameters, reveal the loss mechanisms of GaN devices under high frequencies, give the optimal design principles of loss suppression, and propose digital synchronous driving technologies suitable for MHz applications. The related results are expected to be applied to the power supplies for equipment such as spacecraft, servers, and new energy vehicles, significantly increasing their power density. Therefore, this project has important academic significance and engineering application value.

氮化镓(GaN)器件比传统硅器件具有更好的高频特性，因此采用GaN器件有望将功率变换器的开关频率提高到MHz范围，从而显著地提高变换器的功率密度。然而研究表明，在MHz级应用场合下，GaN器件的损耗机理比低频情况更加复杂，损耗往往比理论结果偏大，甚至会高出一个数量级，成为限制变换器效率和功率密度提升的瓶颈之一，因而研究MHz级应用下GaN器件的损耗机理和损耗抑制技术具有重要意义。本项目拟对MHz应用下GaN器件特有或显著的损耗问题展开研究，具体包括交流导通电阻特性、高频动态电阻效应、输出电容损耗特性以及等效体二极管特性，旨在明确各参数作用下的损耗变化规律，揭示高频下GaN器件的损耗机理，给出损耗抑制的设计原则，提出适用于MHz级应用的数字同步驱动技术。相关成果有望应用于航天器、服务器、新能源汽车等设备的电源中，显著提高其功率密度，具有重要的学术意义和工程应用价值。

采用GaN器件有望将功率变换器的开关频率提高到MHz范围，从而显著地提高变换器的功率密度。然而研究表明，在MHz级应用场合下，GaN器件的损耗机理比低频情况更加复杂，损耗往往比理论结果偏大，成为限制变换器效率和功率密度提升的瓶颈之一，因而研究MHz级应用下GaN器件的损耗机理和损耗抑制技术具有重要意义。本项目对MHz应用下GaN器件的损耗问题展开研究，旨在明确各参数作用下的损耗变化规律，揭示高频下GaN器件的损耗机理，给出损耗抑制的设计原则，具体研究如下：.1）高频交流导通电阻特性研究。研究了GaN器件在高频下的导通电阻特性，并发现导通电阻与频率有关，通过电实验和热实验对该特性进行了证实，这一特性不是由动态电阻效应引起的，而是与GaN器件内部高频电流分布密切相关。然后通过有限元仿真分析揭示了导通电阻随频率变化的机理。最后设计了基于GaN器件的10MHz DC-DC变换器，优化后的变换器效率提高了2%。.2）动态导通电阻特性研究。提出了适用于高频软开关工作条件的动态电阻测量方法，该方法能够工作于单脉冲模式和多脉冲模式，具有响应速度快、易于控制等优点。然后详细分析了单脉冲和多脉冲模式的工作过程，以及提高测量准确性的要点和改进方法。最后研究了高频软开关情况下GaN器件动态电阻随母线电压、开关频率等的变化规律。.3）高频临界导通模式软开关的精确控制研究。提出MHz临界导通模下自适应软开关的控制方法，通过检测GaN器件“体二极管”的导通状态，自适应调节GaN器件的关断时间，最终实现ZVS并且最小化环流。搭建了1MHz Boost变换器，实现99%的峰值效率，并将该方法应用到图腾柱PFC电路中，验证了该方法的可行性。.在本项目的资助下发表了期刊论文5篇，均为SCI检索；发表国内外高水平国际会议5篇，均为EI检索；申请中国发明专利5项，其中3项已授权。相关成果有望应用于航天器、服务器、新能源汽车等设备的电源中，有望进一步提高其效率和功率密度，具有重要的学术意义和工程应用价值。