Cause Analysis of IGBT Tube Damagevyfservice manual download site
IGBT tube in the course of the use, often subject to capacitive or inductive load impact, the occurrence of overload or even load short circuit, etc., may lead to damage to the IGBT tube. IGBT tube in the use of the reasons for the damage are the following:vyfservice manual download site
(1) overcurrent damagevyfservice manual download site
① locking effect. The IGBT tube is a composite device with a parasitic transistor within which the positive bias of the NPN transistor is not sufficient to turn on within the specified drain current range. When the drain current is large enough, this positive bias is sufficient to turn on the NPN transistor, and the NPN or PNP transistor is in a saturated state. So the parasitic transistor is opened, the gate has lost control, and the locking effect takes place. IGBT tube lock effect occurs, the collector current is too large, resulting in excessive power consumption and lead to damage to the device.vyfservice manual download site
② long overcurrent run. The long running of the IGBT tube means that the operating index of the IGBT tube meets or exceeds the current safety boundary defined by RBSOA (such as selection error, safety factor is too small). In this case, the circuit must be able to shut down the device immediately before the current reaches the RBSOA boundary, in order to achieve the purpose of protecting the device.vyfservice manual download site
③ Short circuit timeout (& gt; 10 μs). Short-circuit timeout means that the current value of the IGBT tube reaches or exceeds the maximum boundary defined by the SCSOA (short-circuit safe working area), such as 4 to 5 times the rated current, the transistor must be turned off within 10 μs. If the maximum voltage at this time the IGBT tube also exceeds the nominal value of the device, the IGBT tube must be turned off in a shorter time.vyfservice manual download site
(2) overvoltage damage and static damagevyfservice manual download site
IGBT tube in the off, due to the existence of inductance components in the circuit, turn off the moment will produce spike voltage. If the peak voltage exceeds the maximum peak voltage of the IGBT device, it will cause damage to the IGBT tube breakdown. IGBT over-voltage damage can be divided into a collector-gate over-voltage, gate-emitter over-voltage, high du / dt over-voltage and so on.vyfservice manual download site
Most of the over-voltage protection circuit design is relatively perfect, but for the high du / dt due to over-voltage fault, the design is basically no sense of capacitance or RCD structure of the absorption circuit. As the absorption circuit designed to absorb the capacity is not enough, will cause damage to the IGBT tube, which can be used voltage clamp, often at both ends of the collector and the gate connected to the Zener diode (recommended by the United States Diodes 1.5KE × times A Product series), the use of gate voltage dynamic control. When the collector voltage instantly exceeds the clamping voltage of the Zener diode, the excess voltage will be superimposed on the gate (the Miller effect will work), avoiding the IGBT tube due to the collector-emitter over-voltage damage.vyfservice manual download site
The use of gate voltage dynamic control can solve the problem of collector-emitter instantaneous overvoltage due to the high du / dt, but its drawback is that when the IGBT tube is in the inductive load running state, Its anti-parallel diode (freewheeling diode) recovery, the collector and emitter voltage across the sharp rise, to withstand the high moment du / dt. In most cases the du / dt value is higher than the collector-emitter voltage rise rate when the IGBT tube is normally turned off.vyfservice manual download site
Due to the presence of the Miller capacitor (Cres), the du / dt value will produce an instantaneous current flow between the collector and the gate to the gate drive circuit. The current interacts with the impedance of the gate circuit, causing the gate-emitter voltage UGE to rise, even beyond the opening threshold UGEth of the IGBT, and the harsh condition is that the IGBT tube is mistakenly triggeredvyfservice manual download site
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(3) overheating damagevyfservice manual download site
Overheating damage generally refers to the use of the IGBT tube junction temperature Tj exceeds the maximum temperature limit of the chip. The current application of the IGBT device or Tjmax = 150 ℃ NPT technology for the mainstream, for this purpose in the IGBT tube module application of the junction temperature should be limited to the value below.vyfservice manual download site