2SC0435T
Target
IGBT-Driver.com
Page 11
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The diode D6x must have a very low leakage current and a blocking voltage of > 40V (e.g. BAS316).
For more details about the functionality of this feature and the dimensioning of the response time, refer to
“VCE monitoring / short-circuit protection” on page 13.
Active clamping (ACLx)
Active clamping is a technique designed to partially turn on the power semiconductor as soon as the collector-
emitter (drain-source) voltage exceeds a predefined threshold. The power semiconductor is then kept in linear
operation.
Basic active clamping topologies implement a single feedback path from the IGBT’s collector through transient
voltage suppressor devices (TVS) to the IGBT gate. The 2SC0435T supports CONCEPT’s advanced 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 20
Ω
resistor (see Fig. 6) 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 20
Ω
resistors (see Fig. 6) approaches 20V (measured to COMx).
It is recommended to use the circuit shown in Fig. 6. The following parameters must be adapted to the
application:
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TVS D1x, D2x: it is recommended to use:
- 1x440V TVS (or 2x220V TVS) with 600V IGBTs with DC-link voltages up to 400V
- 2x440V TVS (or 4x220V TVS) with 1200V IGBTs with DC-link voltages up to 800V and
- 3x440V TVS (or 6x220V TVS) with 1700V IGBTs with DC-link voltages up to 1200V
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Raclx and Caclx: These parameters allow the effectiveness of the active clamping as well as the losses
in the TVS to be optimized. It is recommended to determine the value with measurements in the
application. Typical values are: Raclx=0…150
Ω
and Raclx*Caclx=100ns…500ns.
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D3x, D4x and D5x: it is recommended to use Schottky diodes with blocking voltages >30V (>1A
depending on the application).
Please note that the 20
Ω
resistor as well as diodes D3x, D4x and D5x should not be omitted if advanced active
clamping is used. If advanced active clamping is not used the 20
Ω
resistor as well as diodes D3x, D4x can be
omitted.
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.
A resistor between GLx and COMx of 4.7k (other values are also possible) may be used in order to provide a
low-impedance path from the IGBT/MOSFET gate to the emitter/source even if the driver is not supplied with
power. No static load (e.g. resistors) must be placed between GLx and the emitter terminal VEx.
Note however that it is not advisable to operate the power semiconductors within a half-bridge with a driver in
the event of a low supply voltage. Otherwise, a high rate of increase of V
ce
may cause partial turn-on of these
IGBTs.
