fullbridge problem when turn off

[thaihahust]

hello ,
I've built a fullbridge circuit and it works ok until I turn off all 12V and 5V supply at the same time , the fuses are burn (I use IR2110 driver , motor load with 10KHz - 20% duty cycle PWM)
Can you help me find out the problem here
thank you so much


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my 4 MOSFET and 2 driver are normal , I find that when I turn off 24V first , every thing ok . I thing when shut down Ir2110 , it occurs a signal to open all mosfet

 

[schmitt trigger]

When you power off a bridge driver, you must ensure that all its outputs behave correctly even if there are unwanted states coming from the control circuit..

This is achieved by means of the shutdown pin 11. Ideally, you could connect a voltage supervisor to those pins, which will disable the driver quickly as the voltage Vdd drops.

 

[thaihahust]

thank you for reply
Yes, I have connect Pin 11 (shutdown) to pin (2 and pin 13) already, I forget show it in my shematic

 

[Electro nS]

THIS IS not what the guy meant , you should not connect shutdown to pin2 and 13 all the time (GND) , because this means that the driver will never be commanded to shutdown !

you should make shutdown pin HIGH before you turn off the 12v or 5v ( espically the 5v ) . you can do that by external hardware circuit that detects the voltage of VDD (5v) and using a comparator or something like that will pull that pin (shutdown) to 5v .
or you can acheive that by using a microcontroller .

hope that helps

 

[schmitt trigger]

An inexpensive voltage supervisor IC, will have all the features with a minimum of components for an ironclad reset.
like this:
https://www.ti.com/lit/ds/symlink/tl7705a.pdf

 

[thaihahust]

thank you so much.
sorry for my poor in English
acctualy , my problem can solve if I turn off 24V first , but I want an optimate choice. In my design , I use a flyback circuit to provide all 5 and 12 V, so I turn off all 12 V and 5V means I turn off the voltage provides to flyback , so it dont have any power supply . I dont know whether voltage supervisor can provide a HIGH signal to shutdown pin in this case ? when I read datasheet , they call it "output undefined" zone

 

[schmitt trigger]

Read the datasheet carefully. The particular device I suggested, has both active high and active low outputs.
They are both open collector, and the input of the IR2110, if I remember correctly, has an internal pullup.

So, as you approach the low voltage threshold FOR ANY REASON, the open collector will let go, and your device will shut down, optimally.