For high-power IGBTs, the driver circuit is selected based on the following parameters: device turn-off bias, gate charge, solid resistance, and power supply conditions. The positive bias VGE negative bias -VGE and gate resistance RG have different degrees of influence on on-state voltage drop, switching time, switching loss, short-circuit resistance and dv\/dt current of IGBT. The relationship between gate driving conditions and device characteristics is shown in Table 1. The positive gate voltage has a great influence on IGBT's on-off characteristics, load short-circuit capability and dVcE\/dt current, while the negative gate bias has a great influence on the turn-off characteristics. In the design of gate circuit, attention should also be paid to the opening characteristics, load short-circuit ability and false triggering caused by dVcE\/dt current (see Table 1). Table 1 Relationship between IGBT gate driving conditions and device characteristics Because the switching characteristics and safe working area of IGBT change with the change of gate driving circuit, the performance of the driver circuit will directly affect the normal operation of IGBT. To make the IGBT work reliably. IGBT has the following requirements for its drive circuit. 1) Provide the appropriate forward grid voltage to the IGBT. And after the IGBT is switched on. The drive voltage and current provided by the grid drive circuit to the IGBT should have sufficient amplitude so that the power output stage of the IGBT is always in a saturated state. When transient overload occurs, the drive power provided by the grid drive circuit should be sufficient to ensure that the IGBT does not exit the saturation zone. The tube voltage drop after IGBT is switched on is related to the gate source voltage. In the case of a certain drain-source current, the higher the VGE, the lower the VDS is, and the smaller the on-off loss of the device, which is conducive to giving full play to the working capacity of the tube. However, the VGE is not the higher the better, generally not allowed to exceed 20 V, the reason is that once the overcurrent or short circuit occurs, the higher the gate voltage, the higher the current amplitude, the greater the possibility of IGBT damage. Generally, 15 V is appropriate for comprehensive consideration. 2) Can provide sufficient reverse grid voltage to IGBT. During IGBT shutdown, due to the work of other parts of the circuit, some high-frequency oscillation signals will be generated in the gate circuit, and these signals will make the IGBT that should be cut off in a micro state, increasing the power consumption of the tube. Heavy will make the voltage regulator in the short-circuit straight-through state. Therefore, it is best to add a reverse gate voltage (amplitude is generally 5 ~ 15 V) to the IGBT in the cutoff state, so that the IGBT can still be reliably cutoff when the gate has switching noise. 3) with grid voltage limiting circuit to protect the grid from breakdown. The IGBT gate limit voltage is generally 20 V, and the drive signal beyond this range may destroy the gate. 4) Because IGBT is mostly used in high pressure situations. It is required to have sufficient input and output electrical isolation capability. Therefore, the drive circuit should be strictly isolated from the entire control circuit at the potential, generally using high-speed optical coupling isolation or transformer coupling isolation. 5) The gate drive circuit of IGBT should be as simple and practical as possible. It should have the complete protection function of IGBT, strong anti-interference ability, and the output impedance should be as low as possible.
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