Design Of Overcurrent Protection Circuit For Enhancement-mode GaN Devices

Power semiconductor devices based on the third-generation wide bandgap gallium nitride(GaN)material have the advantages of high breakdown voltage,high electron mobility,small parasitic capacitance,and small on-resistance.GaN power devices are gradually replacing silicon(Si)devices for the development of high-frequency,high-voltage electronic systems to meet the needs of high-efficiency and high-power density applications.The overcurrent protection circuit is essential for the safe and reliable operation of power devices,but the overcurrent protection circuit of traditional Si power devices cannot meet the requirements of GaN devices with high operating frequency and short overcurrent withstand time.Therefore,it is important to design a fast-lossless overcurrent protection circuit for GaN devices.The key parameters and short-circuit performance of GaN devices and the advantages and disadvantages of traditional overcurrent protection circuits is first analyzed in this thesis.Then,a fast-lossless overcurrent protection circuit based on drain-source voltage detection is proposed,including a fast-lossless overcurrent detection circuit and an overcurrent fault processing circuit with the indirect soft-shutdown function.The overcurrent detection circuit generates a dynamic blanking time by detecting the on state of GaN devices,which solves the problem of large delay caused by the fixed blanking time of the traditional overcurrent detection circuit.The overcurrent fault processing circuit realizes the indirect soft turn-off function by controlling the turn-on speed of the output stage pull-down NMOS,which avoids the problem of introducing parasitic inductance and capacitance caused by the traditional soft turn-off circuit directly contacting the gate of the GaN device.Based on 0.18?m BCD(Bipolar-CMOS-DMOS)process platform,A fast-lossless overcurrent protection circuit for enhanced GaN devices is designed and performs postsimulation in this thesis.The results show that when the shutdown current is less than or equal to 50 A,the maximum overcurrent detection delay is 95 ns,the maximum fault processing delay is 28 ns,the maximum overall overcurrent response delay is 116 ns,the maximum soft shutdown di/dt is 5.18A/ns and the maximum overshoot voltage is 51 V,the overcurrent detection method is lossless detection and the overcurrent threshold is adjustable,which meets the design requirements.