SCALE™-2+ 2SC0435T
Preliminary Description & Application Manual
www.power.com/igbt-driver
Page 15
V
CE
monitoring / short-circuit protection
Each channel of the 2SC0435T driver is equipped
with a V
CE
monitoring circuit. The recommended
external circuitry is shown in Fig. 7. A resistor
(R
thx
in Fig. 7) is used as the reference element
for defining the turn-off threshold. The value of
the current through R
thx
is 150μA (typical). It is
recommended to choose threshold levels of about
10V (R
thx
values around 68kΩ). In this case the
driver will safely protect the IGBT against short-
circuit, but not necessarily against overcurrent.
Overcurrent protection has a lower timing priority
and is recommended to be realized within the
host controller.
In order to ensure that the 2SC0435T can be
applied as universally as possible, the response
time capacitor C
ax
is not integrated in the driver,
but must be connected externally.
During the response time, the V
CE
monitoring
circuit is inactive. The response time is the time
that elapses after turn-on of the power
semiconductor until the collector/drain voltage is measured (Fig. 8).
Both IGBT collector-emitter voltages are measured individually. V
CE
is checked after the response time at turn-
on to detect a short circuit or overcurrent. If the measured V
CE
at the end of the response time is higher than
the programmed threshold V
thx
, the driver detects a short circuit or overcurrent. The driver then switches off
the corresponding power semiconductor. The fault status is immediately transferred to the corresponding SOx
output of the affected channel. The power semiconductor is kept in off-state (non-conducting) and the fault is
shown at pin SOx as long as the blocking time T
b
is active.
The blocking time T
b
is applied independently to each channel. T
b
starts as soon as V
CE
exceeds the threshold
of the V
CE
monitoring circuit outside the response time span.
The value of the response time capacitors C
ax
can be determined with the following table in order to set the
desired response time (R
vcex
=1.8MΩ, DC-link voltage V
DC-LINK
>550V):
C
ax
[pF]
R
thx
[kΩ]/V
thx
[V] Response time [μs]
0
43 / 6.45
1.2
15
43 / 6.45
3.2
22
43 / 6.45
4.2
33
43 / 6.45
5.8
47
43 / 6.45
7.8
0
68 / 10.2
1.5
15
68 / 10.2
4.9
22
68 / 10.2
6.5
33
68 / 10.2
8.9
47
68 / 10.2
12.2
Table 1 Typical response time in function of the capacitance C
ax
and the resistance R
thx
Fig. 8 Turn-on characteristic of an IGBT or
MOSFET
