IR22141 datasheet(18/28 Pages) IRF

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IR2214/IR22141(SS)

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ADVANCE DATA

2. Undervoltage on V

CC: the FAULT\SD pin

is forced low and held until the

undervoltage is active (not latched).

3. FAULT/SD is externally driven low either

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.

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

B or VCC). When the transistor

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

Ω. 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.

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

DESAT threshold (see figure 16). This

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.

Figure 16:

DSH/L Active Biasing

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.

VDSH/L

100 ohm

100K ohm

RDSH/L

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