Hitachi IGBT Module Application Manual
5.2
Snubber Circuit
Generally, snubber circuits are used to protect the switching IGBT module (when an IGBT module is
turned OFF) by reducing the overshoot voltage generated by the charged energy in the line inductance.
Actual monitoring of the turn-ON and turn-OFF switching waveform is always the best means for deciding
what snubber circuit conditions exist and how to address them.
Note:
For review and reference purposes, the following information
regarding snubber circuits is included here.
5.2.1 Features of Various Snubber Circuits
Figures 18 through 20 provide examples of three typical snubber circuits and their respective features.
5.2.1.1
Snubber Circuit between P and N
In Figure 18 the supply voltage is always charged in capacitor C
s
and controls the overshoot voltage.
Upper- or lower-side relations between D
s
, R
s
, and C
s
are free, so this type of circuit is utilized for small
capacity situations.
Figure 18. Snubber Circuit between P and N
5.2.1.2
Pair of Snubber Circuits between P and N
In Figure 19 the supply voltage is always charged in both capacitors ( C
s
) and controls the overshoot
voltage at each arm. This type of circuit is utilized for large capacity situations.
Figure 19. Pair of Snubber Circuits between P and N
18