SCALE™-2+ 2SC0435T
Preliminary Description & Application Manual
www.power.com/igbt-driver
Page 13
Active Clamping, where the feedback is also provided to the driver’s secondary side at pin ACLx: as soon as
the voltage on the right side of the 20Ω resistor (Fig. 7) exceeds about 1.3V, the turn-off MOSFET is
progressively switched off in order to improve the effectiveness of the active clamping and to reduce the
losses in the TVS. The turn-off MOSFET is completely off when the voltage on the right side of the 20Ω
resistors (Fig. 7) approaches 20V (measured to COMx).
It is recommended to use the circuit shown in Fig. 7. The following parameters must be adapted to the
application:
TVS D
1x
, D
2x
. It is recommended to use:
- Six 80V TVS with 600V IGBTs with DC-link voltages up to 430V. Good clamping results can be
obtained with five unidirectional TVS P6SMBJ70A and one bidirectional TVS P6SMBJ70CA from
Semikron or with five unidirectional TVS SMBJ70A-E3 and one bidirectional TVS SMBJ70CA-E3 from
Vishay.
- Six 150V TVS with 1200V IGBTs with DC-link voltages up to 800V. Good clamping results can be
obtained with five unidirectional TVS SMBJ130A-E3 and one bidirectional TVS SMBJ130CA-E3 from
Vishay or five unidirectional TVS SMBJ130A-TR from ST and one bidirectional TVS P6SMBJ130CA
from Diotec.
- Six 220V TVS with 1700V IGBTs with DC-link voltages up to 1200V. Good clamping results can be
obtained with five unidirectional TVS P6SMB220A and one bidirectional TVS P6SMB220CA from
Diotec or five unidirectional TVS SMBJ188A-E3 and one bidirectional TVS SMBJ188CA-E3 from
Vishay.
At least one bidirectional TVS (D
2x
) per channel must be used in order to avoid negative current
flowing through the TVS chain during turn-on of the antiparallel diode of the IGBT module due to its
forward recovery behavior. Such a current could, depending on the application, lead to undervoltage
of the driver secondary voltage VISOx to VEx (15V).
Note that it is possible to modify the number of TVS in a chain. The active clamping efficiency can be
improved by increasing the number of TVS used in a chain if the total threshold voltage remains at the
same value. Note also that the active clamping efficiency is highly dependent on the type of TVS used
(e.g. manufacturer).
R
aclx
and C
aclx
: These parameters allow the effectiveness of the active clamping as well as the losses in
the TVS and the IGBT to be optimized. It is recommended to determine the value with measurements
in the application. Typical values are: R
aclx
=0…150Ω and R
aclx
*C
aclx
=100ns…500ns. R
aclx
=0Ω is
recommended to improve the effectiveness of active clamping.
D
3x
, D
4x
and D
5x
: It is recommended to use Schottky diodes with blocking voltages >35V (>1A
depending on the application).
Please note that the 20Ω resistor as well as diodes D
3x
, D
4x
and D
5x
must not be omitted if AAC is used. If AAC
is not used, the 20Ω resistor as well as diodes D
3x
and D
4x
can be omitted.
Application note AN-1302 /7/ gives information about Dynamic Advanced Active Clamping (DA
2
C) which allows
increasing the DC-link voltage to higher values in non-switching off-state condition.
Gate turn-on (GHx) and turn-off (GLx) terminals
These terminals allow the turn-on (GHx) and turn-off (GLx) gate resistors to be connected to the gate of the
power semiconductor. The GHx and GLx pins are available as separated terminals in order to set the turn-on
and turn-off resistors independently without the use of an additional diode. Please refer to the driver data
sheet /3/ for the limit values of the gate resistors used.
