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I am building a half-bridge with IR2101 as half bridge driver and I am being confused by something in the datasheet of IR2101. My main supply voltage will be 40V. The VCC of the IR2101 will be 15V stepped down from the same supply. Below is the circuit I am making. Half-Bridge with IR2101

According to my circuit VB is going to 14.5V. Now the datasheet mentions that the max value of VS should be VB+0.3, In reality when the high side Mosfet is ON, VS will be equal to 40V which is clearly very high then the absolute maximum rating. When the high side Mosfet in OFF, it will be 0V which is okay according to the datasheet. Am I interpreting the datasheet wrong or the circuit is not good for this task. But then again the datasheet contains this as an example circuit diagram with supply voltage as 600V. What am I missing here? Any help would be appreciated.

Ir2101 Datasheet

Muhammad Usman
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1 Answers1

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Am I interpreting the datasheet wrong

Yes you are.

Bootstrapping "lifts" the voltage at VB significantly higher than the 15 volt supply rail when the switching begins. That is why there is a diode present and, that is why there is a capacitor present (C1 often called the bootstrap capacitor).

Any help would be appreciated

This is what bootstrapping does; it acquires a voltage on the bootstrap capacitor (your C1) that is about 10 to 15 volts higher than Vcc (40 volts in your case). It does this so that the specialized internal drive circuit can properly activate the upper MOSFET.

Andy aka
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