Time out on IR2113 gate drivers

[A Fresh Lad]

I'm currently building and BLDC ESC, right now just using simple 6 step commutation, but plan on trying to implement FOC. I'm using the IR2113 gate drivers because that's what I had lying around but while using it I've run into a problem. I'm using low side switching meaning the high side of each phase stays on for 2 consecutive steps of the 6 total steps, and at low enough rpm the high side gate drive output from the IR2113 just cuts out. Is there some sort of time out on it where it turns off it left on too long. I wasn't able to find anything about a time out on the datasheet. I'm also quite sure its not the UV lockout, as the low side of one of the other phases is still switching, allowing the boost cap to be charged. I confirmed this by probing it. I currently have a janky workaround involving pulsing the high side off and on for 1 microsecond, which works but I don't want to have to do this when implementing FOC, as low speed operation will be a pain. Am I missing something about the IR2113 or is this just an inherent characteristic? If it is, are there any other popular half bridge drivers I could use without this issue? Especially since the IR2113 is quite expensive, I don't need any of the fancy smarts like the "UV lockout" and "cycle by cycle shutdown", just a basic bootstrap circuit capable of similar currents.
Thanks!

[fourtytwo42]

I'm currently building and BLDC ESC, right now just using simple 6 step commutation, but plan on trying to implement FOC. I'm using the IR2113 gate drivers because that's what I had lying around but while using it I've run into a problem. I'm using low side switching meaning the high side of each phase stays on for 2 consecutive steps of the 6 total steps, and at low enough rpm the high side gate drive output from the IR2113 just cuts out.

That will be high side UVLO caused by boost capacitor discharge, are you using gate to drain resistors on the high side mosfets causing this discharge ?
Your boost capacitors maybe to small or leaky.

as the low side of one of the other phases is still switching, allowing the boost cap to be charged.

Why would this be the case, perhaps you should provide a schematic to show why ?

[Marian_elf]

A differential measurement would also help, either with a differential probe ( preferably ) or with a 2 channel scope using the differential measurement function ( if you do not have a differential probe then make sure you power the circuit to be measured from an isolation transformer if it involves line voltage!!! ).

The idea is to see exactly what happens both with the bootstrap supply voltage in time, and with high side driver output, does it droop at all or does it just cuts out?...

[A Fresh Lad]

Hi, so I followed your advice and I made some measurements using my scope using 2 probes as differential probes and measured the boost cap voltage, and it does seem to be tripping the UV lockout. Before I guess I was making measurements after the UV lockout had already tripped, meaning ofc the boost cap was charged so a bit stupid on my end. On the first capture below, you can see when the UVLO is triggered, the white is high side gate voltage and the purple is the input logic signal to the ir2113. This also explained why my janky workaround of pulsing the logic signal low quickly worked because it seems when the high side mosfet turns off, the inductive kick drags the voltage to ground, allowing the boost cap to be charged again, but after the voltage is back above the UVLO limit, the ir2113 doesn't automatically turn back on. On the second capture below, where white is boost cap voltage and purple is logic input, you can see the boost cap voltage increases after UVLO engages as expected, but the high side gate drive doesn't turn back on until the logic input is pulsed (you have to zoom in a bit as its hard to see, the purple signal is pulsed low very quickly). I'm guessing this is a feature of the ir2113. I don't want to have this workaround, so are there any other mosfet drivers that will re-engage as soon as the voltage is above the limit. Thanks!!

[fourtytwo42]

Hi, so I followed your advice and I made some measurements using my scope using 2 probes as differential probes and measured the boost cap voltage, and it does seem to be tripping the UV lockout. Before I guess I was making measurements after the UV lockout had already tripped, meaning ofc the boost cap was charged so a bit stupid on my end. On the first capture below, you can see when the UVLO is triggered, the white is high side gate voltage and the purple is the input logic signal to the ir2113. This also explained why my janky workaround of pulsing the logic signal low quickly worked because it seems when the high side mosfet turns off, the inductive kick drags the voltage to ground, allowing the boost cap to be charged again, but after the voltage is back above the UVLO limit, the ir2113 doesn't automatically turn back on. On the second capture below, where white is boost cap voltage and purple is logic input, you can see the boost cap voltage increases after UVLO engages as expected, but the high side gate drive doesn't turn back on until the logic input is pulsed (you have to zoom in a bit as its hard to see, the purple signal is pulsed low very quickly). I'm guessing this is a feature of the ir2113. I don't want to have this workaround, so are there any other mosfet drivers that will re-engage as soon as the voltage is above the limit. Thanks!!

Providing schematics instead of wishing for a magic chip is more likely to get your problem resolved.

[Marian_elf]

Hi, so I followed your advice and I made some measurements using my scope using 2 probes as differential probes and measured the boost cap voltage, and it does seem to be tripping the UV lockout. Before I guess I was making measurements after the UV lockout had already tripped, meaning ofc the boost cap was charged so a bit stupid on my end. On the first capture below, you can see when the UVLO is triggered...

Lots of droop just as i suspected, that's why i suggested the scope testing.
You need to increase the capacitor on the bootstrap side enough to cover the lowest frequency expected.
Also the capacitance at the Vcc pin of the driver need's to be large enough to cover both the outputs ( at least several times larger than the cap at the bootstrap supply ).
You increase the capacitance until the high side remains leveled even at the lowest frequency.