© by SEMIKRON / 2020-05-25 / Technical Explanation / SKYPER
®
12 PV
PROMGT.1026/ Rev.7/ Template Technical Explanation
Page 29/37
5.6
Active clamping
The driver offers the possibility to reduce over voltages during the semiconductor’s turn-off process by
using an active clamping feature. Figure 21 shows an example of an active clamping circuitry based on
Zener diodes. The total breakdown voltage of the Zener diodes D
CLMP
determine the voltage level when the
clamping starts. If, during a turn-off of the IGBT the collector-gate voltage V
CG
raises beyond the break
down voltage V
Zener
the clamping diodes will get conductive. This leads to a current feeding energy into the
gate of the IGBT and gradually switches the IGBT on again, until the V
CG
voltage is reduced below the V
Zener
reference.
The CLMP_IN input indicates the driver that the collector-gate voltage raised above V
zener
, if the voltage at
the input exceeds the threshold of 13V. When entering active clamping mode the driver sets the output
channels to high impedance, which reduces the losses on the driver.
Figure 20: SKYPER
12 PV | Active clamping
Figure 21: SKYPER
12 PV | Application example for active clamping
t
V
V
G(on)
V
G(off)
V
G
clamping
active
V
V
Zener
V
DC-Link
V
CE
V
CEsat
0
SKYPER
®
12 PV
R
1
CLMP_IN_TOP X100:07
PWR_GND_TOP X100:08
TOP_OFF X100:06
V
Z
en
er
DC+
T1
R
G(off)_TOP
R
CLMP_TOP
R
G
_
C
L
M
P
AC
&
TOP_IN
D
C
L
M
P
PWR_VS_N_TOP X100:10
D
G
_
C
L
M
P
