© by SEMIKRON / 2019-07-23 / Technical Explanation / SKYPER
®
42 LJ R
PROMGT.1026/ Rev.7/ Template Technical Explanation
Page 26/35
5.5.1
DSCP | Functional description
As long as the driver keeps the semiconductor in off-state the high voltage diode D
VCE
is operating in
reverse direction. The voltage V
CE(IN)
at the VCE_IN pin is set to 10V by the voltage divider of R
1
and R
2
.
The CFG_VCE pin is internally shorten to PWR_VS_P and pulls the voltage V
CE(ref)
at the CFG_VCE pin to
PWR_VS_P. The output of the internal comparator is forced to its negative rail voltage.
When the driver initiates the turn-on process of the semiconductor the internal bypass will be interrupted
and the capacitor C
CFG
discharges until the voltage level defined by voltage divider of R
1_CFG
and R
2_CFG
is
reached. The trip level during the on-state of the semiconductor has reached the static level
(V
CE(ref)
= V
CE(stat)
).
Simultaneously to the discharging process of the capacitor C
CFG
the semiconductor has to switch into
conductive mode and reduces the collector-emitter voltage V
CE
to V
CEsat
. When the collector-emitter voltage
of the IGBT falls below 10V the high-voltage diode D
VCE
is starting to operate in forward direction. Now, the
voltage V
CE(IN)
at the VCE_IN pin follows the collector-emitter voltage of the semiconductor with an offset
caused by the forward current I
F
of the high-voltage diode D
VCE
multiplied by the resistance of R
VCE
plus the
voltage drop V
F
of the high-voltage diode.
The DSCP feature is active from the moment the voltage V
CE(ref)
at the CFG_VCE pin is below 10V. The time
elapsed from initiating the turn-on process of the semiconductor until the DSCP feature is activated is
called blanking time t
bl(VCE)
.
In active state the DSCP triggers an error event, if the voltage V
CE(IN)
at the VCE_IN pin exceeds the
voltage V
CE(ref)
of the CFG_VCE pin.
Figure 19 shows on the left side the above described process for a well-configured blanking time t
bl(VCE)
and
static threshold voltage V
CE(stat).
The upper right side of Figure 19 shows a desaturation event of an IGBT during the DSCP feature is active.
In the moment when the voltage V
CE(IN)
exceeds the threshold voltage V
CE(ref)
the driver enters into error
state.
Also the lower right side shows an error condition. In this case caused by a too short determined blanking
time. The threshold voltage V
CE(ref)
has already fallen below 10V before the monitored voltage V
CE(IN)
is
below that level.
Figure 19: SKYPER
42 LJ R | Dynamic short circuit protection
5
10
15
V
t
V
CE(sat)
V
CE(ref)
V
CE
0
t
bl(VCE)
V
CE(stat)
V
CE(IN)
5
10
15
V
t
V
CE(sat)
V
CE(ref)
V
CE
0
t
bl(VCE)
V
CE(stat)
V
CE(IN)
V
5
10
15
t
V
CE(sat)
V
CE(ref)
V
CE
0
t
bl(VCE)
V
CE(stat)
V
CE(IN)