氮化镓晶体管高频和高速开关应用的负面效应机理及解决方案

Gallium Nitride (GaN) high electron-mobility transistors (HEMT) have the capability to switch fast and to operate in high switching frequency. However, industry converter designs by adopting GaN HEMT do not show the outstanding improvements in power density and reliability. Hence, it is demanding needs to conduct comprehensive and theoretical research on the negative effects of fast switching transients with GaN HEMTs.. The project will focus on studying the mechanisms of negative effects on the control circuits, driver circuits and EMI filter when GaN HEMTs operate in the high switching frequency and high switching transients. Also, the project aims at proposing the practical solutions and design principles to overcome these negative effects. The main innovations include: A. Study on the influence of junction capacitance and dead time on the controller under the high switching frequency and related compensation solutions based on the proposed modulation close-loop scheme. B. Reveal failing mechanisms of driver circuits under high dv/dt switching transients and realize high driving reliability with proposed common mode (CM) noise suppression method by adopting passive CM choke or active impedance circuits. C. Propose a ‘negative impedance’ new concept to improve the filter high frequency attenuation by utilizing the gyrator to eliminate the coupling inductance in EMI filter.. The blueprint of the project is to reduce the trade-off design in the GaN-based converter, and to truly take advantages of high performance of GaN HEMTs, and filling up the framework of design theory in the high frequency power converters, thereby building the technical fundamentals for large-scale application on medium power converters in the industry.

GaN晶体管具有高频、高速开关的能力，但当前基于GaN晶体管的变换器在功率密度、可靠性等方面尚未体现出明显优势，GaN晶体管应用中的负面效应是重要原因。项目深入研究GaN晶体管在高频和高速开关瞬态下应用时，对控制电路、驱动电路、EMI滤波器等产生负面影响的机理，提出切实可行的系统解决方案和设计准则。主要创新研究内容包括：①研究高频下结电容和死区等对控制器的影响机理，提出以调制器闭环为基础的高频PWM波形补偿方法；②揭示驱动电路在高dv/dt瞬态下的失效机理，提出通过共模电感和有源电路提高驱动电路瞬态共模抑制能力的方法，实现高可靠驱动；③提出利用回转器原理产生“负阻抗”，抵消EMI滤波器中近场耦合电感的新方法，显著改善滤波器高频段的衰减性能。该项研究有助于减少GaN变换器的折衷设计，充分发挥GaN器件的潜力，将丰富和填补高频功率变换器的设计理论，为其在中等功率场合的早日规模化应用奠定基础。

GaN晶体管具有高频、高速开关的能力，但基于GaN晶体管的变换器当前在功率密度、效率等方面尚未体现出明显优势。项目深入研究GaN晶体管在高频和高速开关瞬态下应用时，对控制电路、驱动电路、EMI滤波器等产生负面影响的机理，提出了切实可行的系统解决方案和设计准则。主要创新性研究工作包括：.1.针对桥臂中点高频SPWM波形畸变引起的AC侧电压/电流畸变问题，提出了基于调制器闭环的PWM波形单周期补偿方法，给出了电路结构和参数优化设计方法，将交流侧THD由4.97%降低到2.02%。.2.GaN HEMT的高开关速度导致严重的CM干扰，影响变换器驱动、控制、采样等弱电回路的正常工作。基于单相全桥逆变器推导了噪声传输模型，给出了噪声干扰的定量分析方法，并验证了优化隔离电容、差分采样、共模电感、软开关等措施的有效性。.3.以全桥电路为例建立了考虑PCB寄生电容的电路模型、以Buck电路为例建立了平面电感的寄生电容模型，并给出了桥臂中点寄生电容产生附加电路损耗的定量分析方法和低损耗优化措施，并基于量温法实验验证。.4.针对GaN HEMT的低短路承受能力与高dv/dt带来的强噪声环境，设计了基于GaN HEMT输出特性曲线的强抗干扰能力的快速短路保护电路，给出了保护电路抗干扰能力的评估方式，实现了110ns以内的可靠短路瞬态保护。.5.针对高频高升压比有源箝位反激变换器难以实现软开关的问题，提出了适用于该场合的谐振倍压有源箝位反激变换器的软开关实现设计准则。.6.针对现有减小共模电感自电容的方法存在工艺复杂、寄生参数敏感等问题，提出了基于负电容变换器的共模电感自电容抵消技术，给出了负电容变换器的关键参数设计准则和实施方案，显著增加了共模干扰回路中频段的插入损耗。.项目的研究有助于减少基于GaN晶体管的功率变换器的折衷设计，充分发挥GaN晶体管的潜力，将丰富和填补高功率密度电力电子变换器的设计理论，为其在中等功率场合的早日规模化应用奠定基础。