Need Help with IR2110 Full Bridge Mosfet Gate Driver fault Detection

[babatundeawe]

Hi all,

Please can someone help me out with a means of detecting gate or bridge fault in full bridge mosfet driver configuration using IR2110.

i know that there is the like of IRS2214 but its not available to me in the local market here. so i thought how to do it with the available do a lot of search and i came across this in the forum.

please can someone explain how it works.

thanks

Tunde

 

[red_alert]

That schematic has some errors:

1. The C8/C6 and C13/C15 capacitors are placed across the LO and COM pins of IR2110 but they supposed to be placed across Vcc (pin 3) and COM.

2. The D14/D15 node shouldn't be tied to GND (it should be left unconnected).

The working principle of the shutdown circuit is as follow: if the LO output of the IR2110 is HIGH but the low-side MOSFET isn't in ON state (Vds = 0), the voltage across D7 (D17) will be above 4V thus the opamp output will switch to HIGH, activating the IR2110 shutdown circuit.

The shutdown signal is self-maintained by the D27 diode so you have to turn off the power supply to reset the shutdown action.

 

[babatundeawe]

Thanks a lot.

i had noticed D14 and D15 too but since i dont know how the circuit works, i coulldnt say much.

Atleast now i have a conviction that the scheme could work. I will redraw and post back with all the errors you pointed out corrected.

and lastly i will like to send the signal to the micro controller, which will decide when the IR2110 should be disabled or enabled.

thanks a lot.

tunde

- - - Updated - - -

Okay here is the circuit diagram with correction in place and i hope this is okay to work with.

thanks.

 

[red_alert]

In the previous schematic, R24-(D9)-R30 and R28-(D16)-R30 are voltage dividers and the middle voltage is compared to a fixed threshold (IN-, 2.5V).

In the new schematic, you don't have any comparator nor that voltage dividers thus the shutdown signal might be inappropriate for a MCU (at least if you're not feeding it to an ADC input).

Anyway, it's better to keep those voltage dividers and the comparator IC and feed the opamp output (being a logical signal) to your MCU. Btw, don't forget to remove that diode across the output and IN+ of the opamp (HIGH output self-sustaining function).

 

[FvM]

The shutdown circuit has a delay in a 100 ms range, so it's only effective in case of overload, but can't disconnect shorts fast enough.

 

[red_alert]

The shutdown circuit has a delay in a 100 ms range, so it's only effective in case of overload, but can't disconnect shorts fast enough.

That could be improved by reducing the C16 capacitor value.

 

[FvM]

"Could be improved", yes.

Apparently the focus isn't on short circuit protection and I doubt that the circuit can ever achieve it. The response time of usual desaturation sense circuits is somewhere in the microsecond range, and they rely on the current limiting behaviour of IGBT, their effectivity for MOSFET bridges is limited.

 

[red_alert]

I've seen it more like a malfunction detector than a real protection anyway. Even the OP has referenced it as a means of "detecting gate or bridge fault".

The "protection" is not effective against Miller effect neither, as long as there is a diode connected to driver output (D8/D14).

 

[babatundeawe]

Hmn!

Thanks a lot for your input in this.

whao your analysis re explict enough.

@FvM, so does it mean detecting bridge fault using full bridge without dedicated chip can be impossible or how can one go about designing something like this and also including short circuit protection, overload and or detecting a MOSFET that does not turn on.

@Red_alert, talking about removing the diodes (D8-D14) will that not affect the rate of turn-off of the MOSFETs, because that was why they were put there before. will increasing the dead time in the software, will it compensate enough for this?

thanks

tunde

 

[red_alert]

Hmn!
removing the diodes (D8-D14) will that not affect the rate of turn-off of the MOSFETs, because that was why they were put there before. will increasing the dead time in the software, will it compensate enough for this?

You already have D10(D13) that will keep the opamp IN+ at GND level when the low-side driver output is LOW thus D8(D14) seems somehow redundant.

Btw, not D8(D14) but D10(D13) will set (increase) the gate turn-off current.

- - - Updated - - -

For shortcircuit/overload protection, you better use one of these **broken link removed** placed inline with your DC-link and poll its output with your MCU on a high enough rate (microseconds).