IGBT - Desaturation Problem This is the output characteristic curve of a certain product. You can see that the IGBT working area is divided into three parts:
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The working principle of the IGBT half-bridge inverter circuit and the voltage and current waveforms when IGBT1 is turned on and off are shown in Figure 1. Lσ represents the sum of all stray inductances (capacitors, busbars, IGBTs) in the entire commutation circuit (within the stripe area) module).
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Using IGBTs in parallel to form switching devices can enable the entire system to obtain a higher rated current. However, some important issues must be considered when designing a parallel system, such as module characteristics, drive circuits and circuit layout.
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In this case, the avalanche event produces a drain current that is larger where the electric field is stronger. The latch-up effect is caused by the parasitic NPN Bipolar Junction Transistor (BJT) in the power MOSFET. If the device is constructed such that the electric field near the parasitic BJT is high, a large amount of current will flow through its base resistor, creating a voltage between the base and emitter. If this voltage reaches a certain threshold, the bipolar transistor turns on and most of the avalanche current flows through it, with potentially damaging effects since there is no way to control the current.
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Under normal circumstances, MOS, which is commonly used for high-end driving, needs the gate voltage to be greater than the source voltage when it is turned on. When the MOS tube for high-end driving is turned on, the source voltage is the same as the drain voltage (VCC), so at this time the gate The pole voltage is 4V or 10V greater than VCC.
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The switching characteristics of the IGBT power module are determined by its internal structure, internal parasitic capacitance and internal and external resistance. In an ideal state, we only need a zero-power voltage signal to be applied to the MOS base to activate the switch. But in practice, the charge stored in the capacitor inside the component must be released, so a driving power signal with the same switching frequency is required. In addition, the commutation process is also affected by parasitic inductance. Parasitic inductance exists in the port loop of the module and inside the module, as well as in the connection lines connecting the transistor chips.
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