Research On Dynamic Characteristics Of High-voltage GaN Devices Based On Power Topology

As a third-generation semiconductor material,GaN is used in the field of power electronics due to its excellent characteristics such as high breakdown electric field and high electron mobility.After years of development,GaN power devices are gradually playing a significant role in various fields such as automotive lidar systems,data centers,and consumer electronics chargers.Because the impurities and defects introduced during the epitaxial growth of GaN materials will trap and release electrons under voltage stress conditions,the on-resistance of GaN devices will change dynamically.In recent years,more and more researchers at home and abroad have begun to pay attention to the impact of voltage stress conditions on the dynamic on-resistance of GaN HEMTs.However,the current research is only aimed at the dynamic on-resistance measurement and on-resistance change mechanism analysis of GaN devices under different voltage stress conditions,and does not further study the effect of dynamic on-resistance of GaN devices on the efficiency of power conversion systems under practical application conditions.Based on the above research background,combined with the power half-bridge Buck topology,the dynamic characteristics of the switching behavior of GaN devices are studied,and the influence of the on-resistance variation on the efficiency of the topology system is analyzed.The main contents include the following aspects:(1)Based on the principle of Buck topology,a half-bridge Buck circuit based on GaN devices is designed to complete the selection of GaN-specific drivers,power devices,and power inductors,and the circuit functional simulation is performed using the simulation tool LTspice.(2)Two mechanisms for increasing the on-resistance of GaN devices due to voltage stress are analyzed,and a device test scheme is designed.The effects of temperature and drain-source voltage bias on the on-resistance of P-gate GaN devices at different voltage levels are studied.The results show that after the periodic off-state drain-source voltage bias,the on-resistance of the P-gate GaN device increases by 8% to 46%,the increase amount varies with the bias voltage,and the off-state drain-source bias is removed at the device.In the first few seconds after the reset,the on-resistance recovery is very fast,and then the recovery is gradually slower.It takes hundreds of seconds or even longer to return to the initial state of the device.The off-state drain-source voltage bias has no significant effect on the on-resistance of the mixed-drain structure GaN device,and the variation range is less than 1%.Whether it is a P-type gate GaN device or a mixed-drain GaN device,their on-resistance will increase significantly under high temperature conditions,and the increase will more than double at 150?.(3)Based on the 400V-48 V half-bridge Buck circuit application scenario,the influence of the on-resistance rise caused by the off-state drain-source voltage bias of the GaN device on the system efficiency was evaluated,and the Buck circuit was kept in a normal working state.The self-heating effect of GaN power devices was studied Impact on system efficiency caused by changes in device on-resistance.The results show that the increase in on-resistance caused by the off-state drain-source voltage bias of the GaN device has little effect on the efficiency of the 400V-48 V half-bridge Buck circuit system,and the efficiency does not decrease by more than 0.6%,compared with the conduction caused by the self-heating effect.The effect of resistance change on the system loss is very obvious,which will increase the system loss by about 25%.