Hitachi IGBT Module Application Manual
Pair of Snubber Circuits between Arms
In Figure 20 charge and discharge are repeated on every switching of each arm from 0V to supply
voltage. Because the snubber loss is large, this circuit is best suited to narrow Reverse-Biased Safe Operating
Area (RBSOA) devices and would, generally, not be used with IGBT modules.
Figure 20. Pair of Snubber Circuits between Arms
5.2.2 Snubber Circuit Operation
Figure 21 represents a circuit in the overvoltage occurrence mode of a bottom-arm IGBT at the time of
turning OFF. Figure 22 represents an equivalent circuit in a transient state at the same time.
Figure 21. Turn-OFF Mode of bottom arm IGBT
Figure 21 represents changes in the current pass when the bottom IGBT, which was ON, is turned OFF.
When the bottom arm IGBT is turned OFF, the load current passes through the FWD at the top arm and is
refluxed. Discharge of energy accumulated in the L
is applied to the bottom arm IGBT as an overvoltage
because the absence of a snubber circuit results in the loss of a discharge destination.
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