IR2110 and H-Brdige not working less than 12v

[naseerak]

I have designed an H-Bridge using IR2110 but when the battery voltage depletes to less than 12v it becomes unstable perhaps the bootstrap supply circuit stop working at this voltage, but I have read its datasheet which states it can work up to 10V.

 

[Pulsetronics]

Kindly upload the circuit

 

[naseerak]

This is the circuit, actually I want to shut down my invt till 10.5v (a common phenomena here) or better call it a tradition, no body will accept your inverter if it shuts down early.

 

[--BawA--]

Did you see the gate waveforms of high side mosfets during DC link voltage <12V ?
Also i don't see a DC link Capacitor in your schematics.

 

[red_alert]

I don't see (in your schematic) an output voltage feedback circuit (you might actually use one at the MCU level).

During the feedback process, when the input voltage is low, the PWM modulation might reach 100% (trying to keep the output at the rated output voltage - 230V) so the bootstrap capacitor doesn't have the possibility to recharge for a longer period (it needs the low-side switch to be in ON state for that).

You should check in your software if the modulation could ever reach 100% (and change that accordingly to 95% or something).

You should also check (with a scope) the high-side MOSFETs gate voltages for a confirmation of this behaviour.

You might try a bigger bootstrap capacitor too (though you didn't mention the switching frequency and the dead time).

The bootstrap diode should be a faster one (depending on your switching frequency, again).

Same thing for the gate turn-off diodes (I also noticed you didn't use such a diode for the second MOSFET gate in a parallel group). Those paralleled MOSFETs have the gate resistors in series - you should connect both of them at the IR2110 output not in series (for identical gate control of both MOSFETs).

 

[chuckey]

Red_alert has got it right. If U2, pin 7 goes to +12V, then Q3 g gets 10/28 X 12 V and Q6 g gets 22/32 of this value. Is this enough?
Frank

 

[naseerak]

I am using 31.25KKhz, as for feedback is concerned it is done on the controller side with optocoupler.