IR22141 International Rectifier, IR22141 Datasheet - Page 18

• Manufacturer Part Number: IR22141
• Description: HALF-BRIDGE GATE DRIVER IC
• Manufacturer: International Rectifier

IR2214/IR22141(SS)
5. Active bias
For the purpose of sensing the power transistor
desaturation the collector voltage is read by an
external HV diode. The diode is normally biased
by an internal pull up resistor connected to the
local supply line (V
is “on” the diode is conducting and the amount
of current flowing in the circuit is determined by
the internal pull up resistor value.
In the high side circuit, the desaturation biasing
current may become relevant for dimensioning
the bootstrap capacitor (see figure 19). In fact,
too low pull up resistor value may result in high
current discharging significantly the bootstrap
capacitor. For that reason typical pull up resistor
are in the range of 100 k . This is the value of
the internal pull up.
While the impedance of DSH/DSL pins is very
low when the transistor is on (low impedance
path through the external diode down to the power
transistor), the impedance is only controlled by
the pull up resistor when the transistor is off. In
that case relevant dV/dt applied by the power
transistor during the commutation at the output
results in a considerable current injected through
the stray capacitance of the diode into the
desaturation detection pin (DSH/L). This coupled
noise may be easily reduced using an active bias
for the sensing diode.
18
2. Undervoltage on V
3. FAULT/SD is externally driven low either
is forced low and held until the
undervoltage is active (not latched).
from the controller or from another
IR2214 device. This event is not latched;
therefore the FLT_CLR cannot disable
it. Only when FAULT/SD becomes high
the device returns in normal operating
mode.
B
or V
CC
). When the transistor
CC
: the FAULT\SD pin
ADVANCE DATA
An Active Bias structure is available only for
IR22141 version for DSH/L pin. The DSH/L pins
present an active pull-up respectively to VB/VCC,
and a pull-down respectively to VS/COM.
The dedicated biasing circuit reduces the
impedance on the DSH/L pin when the voltage
exceeds the V
low impedance helps in rejecting the noise
providing the current inject by the parasitic
capacitance. When the power transistor is fully
on, the sensing diode gets forward biased and
the voltage at the DSH/L pin decreases. At this
point the biasing circuit deactivates, in order to
reduce the bias current of the diode as shown in
figure 16.
6. Output stage
The structure is shown in figure 13 and consists
of two turns on stages and one turn off stage.
When the driver turns on the IGBT (see figure 8),
a first stage is constantly activated while an
additional stage is maintained active only for a
limited time (ton1). This feature boost the total
driving capability in order to accommodate both
fast gate charge to the plateau voltage and dV/dt
control in switching.
R
DSH/L
Figure 16: R
100K ohm
DESAT
threshold (see figure 16). This
DSH/L
Active Biasing
100 ohm
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V
DSH/L