Research On SiC MOSFET Gate Drive Power Supply And Protection Circuit

Compared with silicon(Si)materials,silicon carbide(SiC)materials have the characteristics of large band gap,high critical breakdown electric field strength,fast saturation drift speed and high thermal conductivity.SiC-based can achieve higher withstand voltage and higher operating junction temperature than Si-based;the characteristics of high electron mobility also make it have higher switching speed;SiC-based devices have lower on-resistance and high temperature stability characteristic.Therefore,SiC-based devices are widely used in high-frequency and high-temperature environments,which is beneficial to reduce switching losses,shorten dead time,and increase switching frequency.The increase of switching frequency can reduce the volume of passive components accordingly,which is beneficial to increase the power density of conversion rate,but the disadvantage is that it often causes serious electromagnetic interference(EMI)problems.In short,once the converter adopts SiC-based devices,its performance will be greatly improved.Driving power semiconductor devices should have sufficient pulse width gate drive capability,gate drive power supply(GDPS)stability for high performance operation.The isolated active clamp flyback(ACF)topology meets the isolation level required by the power circuit while providing positive and negative reliable gate voltages for the gate,and reduces EMI and voltage stress.While ensuring reliable zero-voltage switching(ZVS)of the switching tube,the hybrid resonance method is used to improve the resonant current and the secondary current waveform,which effectively reduces the loss of the switching tube and realizes the zero-current switching(ZCS)of the rectifier diode.The design method of the main power circuit parameters is given through steady-state analysis,and the volume of the converter is further reduced by combining the planar transformer.Use SIMetrix/SIMPLIS to build a simulation circuit to ensure two +18/-5V voltage outputs.Experiments verify the rationality of the parameter design and the effectiveness of the converter topology.Under the influence of high switching speed characteristics and the non-negligible parasitic parameters contained in the device,the SiC MOSFET crosstalk problem of the half-bridge module under the traditional driving method is very serious.Most crosstalk suppression circuits often sacrifice the corresponding switching delay,increase switching loss and At the cost of increasing the complexity of the control process,the relationship between them cannot be well balanced.On this basis,an improved gate drive circuit combining negative voltage shutdown and drive impedance control is proposed.Firstly,the formation mechanism of crosstalk and typical active gate suppression methods are analyzed.Second,based on the auxiliary triode control branch,a low-impedance path is provided for forward crosstalk.A variable gate voltage is then applied through a self-driving auxiliary circuit to reduce negative crosstalk effects.Using the original gate-source voltage as the auxiliary circuit drive signal,the gate driver does not introduce any other control signals,avoiding additional signal isolation.A high switching rate will bring problems such as transient voltage and current spikes,high-frequency oscillation,electromagnetic interference,etc.,and increase the switching loss of the device,and even damage the device in severe cases.This paper analyzes the mechanism of the transient problem,and proposes an Intelligent Digital Active Gate Drive(IDAGD),which monitors the dynamic process of the switch and adjusts it to the optimal switch state through a logic loop.Next,verify the correctness of the circuit and the feasibility of the theory.The active gate drive method reasonably divides the switching process of the device.Through state monitoring and feedback,the optimal gate resistance value is selected by restricting constraints at a specific stage to reduce voltage and current overshoots.with inhibition of oscillations.Ensure safe and reliable operation of the device while balancing switching loss and overshoot.Compared with the conventional gate driver(CGD),the proposed smart digital active gate drive can effectively suppress spikes and oscillations.Finally,Or CAD Pspice simulation and double-pulse test experiments with different load currents were carried out on a 1200V/80 A SiC MOSFET to verify the switching performance of the SiC MOSFET under the action of the IDAGD circuit.