【作者】 张楠；

【导师】 李艳；

【作者基本信息】 北京交通大学 ， 电气工程， 2023， 硕士

【摘要】 相比硅(Silicon,Si)器件,氮化镓(Gallium Nitride,GaN)器件具有较高的开关速率和较低的导通电阻,在很多领域得到了广泛的应用。然而,由于高的dv/dt和较低的阈值电压,GaN器件容易在主动管开通和关断过程中出现持续振荡现象,导致器件损坏。为明确GaN器件在实际应用中出现持续振荡的条件,本文将从电路振荡稳定性的角度出发,提出了一种判断电路振荡稳定性的方法,分析在常规驱动方法下电路的振荡稳定性。在此基础上,提出了在驱动回路加入无源器件来提高电路振荡稳定性。根据无源器件的种类、是否具有初值以及其加入的位置,可以分为在驱动回路引入负压、串联高阻尼支路以及并联低阻抗支路三类。首先,提出了一种利用无源器件实现GaN器件负压关断的方法,该方法中分压器由稳压二极管、电阻和电容组成,它与驱动芯片间具有两种连接方式,可以实现恒定不变的负压和具有自恢复的负压,在开通回路串联的二极管可起到抑制栅源极电压振荡的作用。基于双脉冲电路,对两种连接方式的无源驱动优化方法进行了模态分析,详细说明了相关参数的设计要点,通过仿真和实验验证了该方法的有效性,在此基础上分析了负压关断对电路振荡稳定性的影响。其次,分析了采用常规驱动方法时,GaN器件在开关过程中出现持续振荡现象的诱因,根据诱因建立了在驱动回路串联高阻尼支路(关断电阻、磁珠)的负电导模型,提出利用环路电导值作为衡量电路稳定度的标志,归纳总结了串联高阻尼支路前后环路电导值的变化规律,通过仿真和实验验证了理论分析的准确性。最后,根据振荡诱因建立了在驱动回路并联低阻抗支路(RC阻尼器)的负电导模型,归纳总结了并联低阻抗支路后环路电导值的变化规律,通过仿真和实验验证了理论分析的准确性。在此基础上对比了负压关断、串联高阻尼支路、并联低阻抗支路这三种无源驱动优化方法的优劣,为选择合适的无源驱动优化方法提供了指导。更多还原

【Abstract】 Compared with Silicon(Si)devices,Gallium nitride(GaN)devices have been widely used in many fields due to their higher switching rate and lower on-state resistance.However,high dv/dt and low threshold voltage cause GaN devices to be easily exposed to sustained oscillation during switching-on process and switching-off process of the active device,resulting in device damage.Therefore,in order to clarify the conditions for sustained oscillation of GaN devices in practical applications,this paper studies from the perspective of stability,analyzing the oscillation stability of the circuit under the conventional driving method,proposing a method to judge the oscillation stability of the circuit.Based on this,it is proposed to improve the oscillation stability of the circuit through the addition of passive components in driving circuit.According to the types of passive components,whether they have initial values and their incorporation locations,this paper proposes three passive driving optimization methods,which consist of introducing negative voltage in driving circuit,connecting high damping branches in series and low impedance branches in parallel,respectively.Firstly,A negative voltage turn-off method applicable to GaN devices has been proposed using passive components,and there are two types of connections between the divider consisting of Zener diode,resistor and capacitor and the driver chip,which achieve both constant negative voltage and self-recovery negative voltage.Meanwhile,the diode connected in series in switching-on circuit suppresses oscillation of the gate source voltage.Taking the double pulse circuit as an example,analysis of the mode of the passive driving optimization method for the two connection methods is carried out,the design requirements of the relevant parameters in this method are given and the validity of the method is verified by simulation and experiment.Based on this,the impact of negative voltage turn-off on the oscillation stability of the circuit is analyzed.Secondly,the inducement of sustained oscillation phenomenon of GaN devices during switching-on process and switching-off process adopting conventional driving method has been analyzed,and the negative conductance model with high damping branches(switching-off resistance,ferrite beads)has been established according to the inducement.It is proposed to take the loop conductance value as a symbol of circuit stability and summarizes the rules of loop conductance value before and after connecting high damping branches in series.and the accuracy of the theoretical analysis is also verified by simulation and experiment.Finally,the negative conductance model with a low-impedance branch(RC damper)connected in parallel in driving circuit has been established,according to the inducement.and summarizes the rules of loop conductance value after paralleling the low impedance branch.and the accuracy of the theoretical analysis is also verified by simulation and experiment.Based on this,a comparison is made between the advantages and disadvantages of three passive driving optimization methods including negative voltage turn-off,high damping branches in series and low impedance branches in parallel.It provides guidance for selecting an appropriate passive driving optimization method.更多还原