Reasearch On Dynamic On-resistance Measurement Methods Of E-mode GaN Power Devices

Gallium nitride(GaN)devices are an important representative of the third-generation power semiconductors.Compared with traditional silicon(Si)devices,GaN power devices have stronger withstand voltage capabilities.Under the same withstand voltage,the on-resistance is extremely low,and the loss is small.It has higher output power density and stronger driving force,and has broad market prospects in the field of power electronic conversion.However,GaN devices have the phenomenon of dynamic resistance degradation,which greatly increases the on-resistance of GaN devices,brings great uncertainty to the loss estimation of GaN devices,and restricts the further development of GaN devices.Accurately measuring the on-resistance of GaN power devices can provide effective data for the design of power electronic applications and reduce the design difficulty.Therefore,the dynamic resistance characteristics of GaN power devices have become a research hotspot.The voltage swing of GaN devices is too large when switching,and traditional voltage measurement circuits cannot accurately measure the on-voltage due to the overshoot effect of the oscilloscope.In recent years,the use of clamp circuits to indirectly measure the on-voltage of GaN devices has become the mainstream method.Several commonly used clamping circuits are analyzed,and a new clamping circuit is designed.At present,most of the dynamic resistance tests for GaN devices are aimed at hard switching,and the operating frequency is not high.In this thesis,test circuits for hard switching and soft switching are designed with clamping circuits,and the measurement frequency can reach the megahertz level.The hard-switching test circuit uses the double-pulse test method commonly used to test switching devices,and controls the operating current of the GaN device to explore the influence of voltage and frequency on the dynamic resistance of the GaN device; the softswitching test circuit is a no-load resonant switching circuit.Two sets of comparators are used for control to achieve zero voltage conversion.In this thesis,two enhancement-mode GaN power devices with different structures are selected to conduct multiple sets of tests in two switching modes,and the experimental data are processed.The experimental results show that the dynamic resistance performance of different structures of GaN devices under soft and hard switching is quite different.Therefore,the influence of dynamic resistance should be fully considered in the design and loss analysis.This thesis analyzes the GaN device model in SPICE,and designs a circuit model according to the characteristic curve of the on-resistance of the GaN device model in LTspice,which can simulate the dynamic resistance degradation of GaN devices in LTspice,and use the actual measurement The parameters of the LTspice model are optimized with the data obtained from,and the loss calculation is performed using the optimized model,and the loss before and after the model optimization is compared with the actual measured loss,which verifies the validity of the model.This model also provides a reference for modeling the dynamic resistance of GaN devices.