Research On Switching Characteristics Of GaN Devices And Design Of Crosstalk Suppression Drive Circuit

The high-performance power electronics technology is the system core of emerging industries such as 5G communications,aerospace,electric vehicles,and fast charging.The high-frequency,high-efficiency,high-power density,and high-voltage design of core power conversion devices has become an inevitable trend in future development.However,traditional Si-based devices have gradually reached their technical bottleneck after more than 60 years of research and development,and it is difficult to further meet the higher performance requirements of semiconductor devices in various fields.As a representative of the third-generation wide-bandgap semiconductor devices,GaN-based power devices have become a research hotspot in the power electronics and electronic information fields with more excellent switching performance,and have gradually replaced Si-based devices in some application fields.However,the development of GaN power devices is still limited by many aspects.Among them,the lack of reliable and high-speed GaN gate drive is one of the reasons why its performance advantages cannot be fully utilized at the moment.In the bridge circuit,as the switching speed of semiconductor devices increases,excessive dv/dt and di/dt will interact with the parasitic inductance and capacitance existing in the drive circuit,and consequently result in significant current and voltage stresses together with serious crosstalk effect.It will not only lead to an increase in switching loss,but also reduce the stability and reliability of the converter,and even cause irreparable damage to the power device in ultimate conditions.Therefore,reasonable control and optimization of various parasitic parameters in the circuit and the use of reliable driving schemes are of great significance for giving full play to the performance advantages of GaN devices and improving the reliability of the converter system.Aiming at dealing with the crosstalk effect in the bridge circuit,this paper conducts a systematic study on the basic characteristics of GaN devices and the design of driving circuits.The main work is as follows:First,the basic characteristics of GaN devices and the crosstalk effect in bridge arms are studied.The basic structure,switching characteristics and reverse conduction characteristics of enhancement mode GaN devices are analyzed and studied.The similarities and differences in the design of driving circuits between GaN devices and Si and Si C devices are compared,and the heat dissipation methods of the top and bottom heat dissipation GaN chips are analyzed and their respective total thermal resistance calculation formulas are derived.Subsequently,the mechanism of the crosstalk effect in the bridge circuit is studied,and the three commonly used methods for the suppression of crosstalk effect are compared and analyzed.Secondly,in view of the crosstalk effect existing in the bridge circuit,a a variablecapacitance dual-voltage-drive auxiliary circuit,which can effectively suppress the crosstalk,is designed.Based on the established parasitic parameter model of the GaN half-bridge circuit,the influence of various parasitic parameters on the switching performance and crosstalk effect is analyzed through theoretical derivation and simulation.Subsequently,three commonly used auxiliary circuits for crosstalk suppression were studied,and their effects on switching performance and crosstalk suppression effects were simulated and compared.On this basis,this article proposes a variable-capacitance dual-voltage-drive auxiliary circuit with crosstalk suppression capability,and its basic structure,working principle and methods of optimization of auxiliary circuit parameters are systematically introduced and analyzed.Finally,the effectiveness and reliability of the auxiliary circuit are verified through Ltspice simulation and prototype tests.Finally,the applications of the proposed crosstalk suppression drive circuit in the GaN-based three-phase inverters for permanent magnet synchronous motors(PMSMs),phase-shifted full bridges and half-bridge LLC bridge circuits are studied.Firstly,the structure and basic control strategy of PMSM are introduced,and the structure of its driving circuit is optimized and improved based on MATLAB simulation software.A vector control simulation model based on the cooperation of MATLAB and Saber is built,and the effectiveness of the improved drive circuit in suppressing crosstalk is effectively verified in simulation.Subsequently,the working mechanism of GaN-based phase-shifted full-bridge and half-bridge LLC resonant circuits,as well as the principles and types of crosstalk effects are analyzed in detail.It is found that both two circuits can achieve the zero voltage switch-on(ZVS)in the primary side bridge arm switch,and the crosstalk effect only exists during the switch-off of bridge arm.Based on this analysis,this article has made improvements to the drive structures of both circuits accordingly,so that they can effectively suppress the crosstalk spikes during the switch-off of bridge arms.Finally,simulation circuit models of both circuits were built in Saber,and their crosstalk suppression effects are verified afterwards.