9020 Datasheet, PDF (14/25 Pages) Fairchild Semiconductor – IGBT Basic II

Short-circuit threatens this FBSOA. If there is a short-circuit, IGBT’s I_C increases. However,
depending on the IGBT’s output characteristics—I_C current is limited by the value of V_GG+, but
since the voltage is high when the circuits are shorted, the device must withstand extreme loss
of power. As time passes, temperature rises from power loss, and the temperature of the
device continues to increase. In this case the IGBT must turn off within 10us.
In order to protect the IGBT from short circuit situations, the device’s short circuit capability
must first be known. In general, the simplest short circuit test is testing the IGBT’s short circuit
capability. However, this is different from real application short circuit conditions. In this test, it
is not possible to see the effects of dynamic dv/dt, which induces IGBT’s latch-up. It is possible
to obtain short circuit time with short circuit testing of different products from many companies.
In general, short circuit time becomes longer with high saturation voltage and V_{CE (sat)}. (In
measuring V_{CE (sat)}, gate voltage should be enough for the minimum value of V_CE(sat), and that
level must be maintained during fault test.)
3. Types of Short Circuit
Short circuit can happen while IGBT’s normal function. Short circuit can be divided into two dif-
ferent types. The first is short-circuiting when the device was in on state, which is called “fault
under load” and the second is a circumstance where the device turns on under short circuit,
which is called “hard switch fault.”
A. Type I: Fault under load (FUL)
Fig. 2. Fault under load test circuit
Fig. 3. Fault under load waveform
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Rev. A, April 2002