All the points described so far arise when the IGBT gate is controlled with a bipolar
voltage (e.g. -15V/15V). In a unipolar control regime with 0V/15V only a turn-on delay
will occur. The switching speed, however, will not change.
7.8 Safeoperating area (SOA)
RBSOA stands for "reverse bias safe operating area" and it describes the area inwhich
the IGBT may safely be operated while a reverse voltage is applied. This area is
traversedduring the IGBT turn-off process andmay not beexceeded.
As depicted i
, theRBSOAmay be defined for two different reference points:
Referenced to the module terminals or referenced to the semiconductor chip. The
difference between the two designations can be described by the internal stray
inductance of the module. This limits the maximum useable DC-bus voltage plus
switching over-voltages to values below the nominal blocking voltage U
example shows clearly that a load current
only permits amaximum voltage of
approximately 1070V between the collector and emitter module terminals (given the
specified datasheet conditions).
Examples of RBSOA (Infineon Technologies) and SCSOA (Fuji Electric)
Manufacturers quote the RBSOA only to the value of twice the nominal current and the
maximum IGBT blocking voltage. Operating points above
are not defined. Not
before the short circuit is reached will the conditions then be defined by the
manufacturers and quoted by theSCSOA (short circuit safeoperating area) as shown in