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Author Topic: Trouble with driving IGBTs with OptoIsolators  (Read 2153 times)
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I think he probably had the board layout supplied with the board, but not the schematic. Depending on experience, the board layout is handy for troubleshooting as one can see tha actual connections. A schematic can be difficult because the layout of the board and the layout of the schematic can be quite different. Many is the time I have had to draw a board layout so I could figure out where the signals were actually going.

Actually, I think the IGBT could be driven directly from the Arduino. Worst case would be a couple resistors, one from the Arduino and one to ground. I am using a 4 of these in a washing machine (commonly called SSRs) but they are rated 5 to 20V control signal.
« Last Edit: March 18, 2013, 04:46:33 pm by kf2qd » Logged

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You are trying to make an H-bridge with IGBTs and using the same supply to drive the gates on the high-side switches
as on the low-side switches - there is no chance of this working.

You need a floating power supply for each of the high side switches that follows the high-side emitter voltage.  The
way to do this is with a high-side-low-side driver chip.  These are available upto 600V or so, and for higher voltages
you'll need to engineer your own high-voltage charge-pumps...

If the voltage isn't beyond 600V I'd suggest looking at chips like IRS2112, FAN7380, FAN7388 ...
For lower voltages there are more choices of chip.  80V and below the HIP3081 does everything you
need in one.

Ideally for high power use you would want to drive gates negative in an IGBT to reduce turn-off time - this
matters more with high voltage and high current.  Higher voltage IGBT's tend to want higher gate drive
voltages (+15/-5 rather than +12/0)
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I dont have a schematic,
I here this sort of thing a lot from beginners. Tell me how on earth you can make anything if you don't have a schematic so you can see what you are making?
Maybe it's me but I would not even think about trying to do that.

lol, its in my head.
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Why didn't you say. I will put my mind reading hat on.


Dam the batterie is flat.
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This is all setup on a breadboard btw. It seems the arduino cannot supply enough current to switch the IGBTs properly. I decided to add another 12V battery so i have +12 and -12 on the high side of the optos. the problem is that the arduino can only push-pull one opto when its tied to the gate of an igbt. my next step is to get some of these TC4422's to drive them. http://www.ebay.com/itm/170985238551

I need the design to have a low side for the arduino+other stuff (3.3v|5v). a mid side for higher power devices(such as driving the gate of the IGBTs and lighting,etc(12v|15v|24v), and a high side for heavy loads.(12v|24v to 800v)
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It seems the arduino cannot supply enough current to switch the IGBTs properly.
No, it takes virtually no current at all to turn a FET on. Not enough voltage perhaps but current no.

If your design was on paper instead of your head maybe we could help you with it.
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But if a MOSFET or IGBT is switching high voltage and current at high frequency (PWM basically) the gate does
need large currents to charge up and down fast enough to reduce switching losses to acceptable levels.

Also if switching high voltages with MOSFETs you may need a low-impedance gate driver or protection circuitry
to prevent capacitive coupling from the drain to gate burning out your microcontroller.  Especially true for
inductive loads at switch-off.
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It seems the arduino cannot supply enough current to switch the IGBTs properly.
No, it takes virtually no current at all to turn a FET on. Not enough voltage perhaps but current no.

If your design was on paper instead of your head maybe we could help you with it.

I will draw something up here in a bit.

The arduino controlls the optocouplers, and how i have it setup is on pins 2,3,4,5 goto 2 optocouplers each.
the optocouplers are setup in a push-pull mode. When a pin goes HIGH the output from the two optos will put out +12v and -12 when the pin is low. now, when the gate of the IGBTs are not connected everything is ok.
but when i connect the gate, only the pins 2, and 4 actually switch the IGBT. 3, and 5 give odd values like +13 on high, and +8 on low, while the the other pins(2,4) continue to put out +/-12v.
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sloppy but thar u go for now. I will be redrawing the design after I get some sleep.



just to clear some things up, on all the opto leds at the bottom, there is a resistor between the leds and ground.
same with a resistor between the other rail for the leds and +3.3v of the arduino.

As for the the opto connected to the transformer, the opto actually drives a mosfet that is fed from +12v. the opto itself is driven from +5v from the arduino supply.

Common ground is the tie point between the 12v cells. The capacitor, arduino, IGBTs, opto leds, and the mosfet are all grounded to this point.
« Last Edit: March 20, 2013, 01:07:00 pm by MegaGamerGuy » Logged

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But if a MOSFET or IGBT is switching high voltage and current at high frequency (PWM basically) the gate does
need large currents to charge up and down fast enough to reduce switching losses to acceptable levels.

Also if switching high voltages with MOSFETs you may need a low-impedance gate driver or protection circuitry
to prevent capacitive coupling from the drain to gate burning out your microcontroller.  Especially true for
inductive loads at switch-off.
Mark, chill out, this is a H-bridge.
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This one is much cleaner.

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I have to ask, why aren't you using a gate driver?  When I played with a HV project (~400V) and an IGBT, I had to use a gate driver to prevent the IGBT from overheating, but I was PMWing the transistor.
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I have to ask, why aren't you using a gate driver?  When I played with a HV project (~400V) and an IGBT, I had to use a gate driver to prevent the IGBT from overheating, but I was PMWing the transistor.

dont have one yet, and it will be some time before i can afford some. I still need some bolts for my capacitos, 3 more A123 20AH cells, 1200v diodes, the IGBT drivers, more IGBTs, and some mosfets. >.<

I also need to figure out how in the world i can drill threaded screw holes into a larger heatsink. and eventually I plan to use water cooling for the system, but google search does not turn up much. i have to machine all this crap myself, or find someone who can.
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The reason I ask is that it takes Amps of current to switch the transistor at its rated speed.  A micro pin or opto is just not going to cut it if you are switching it quickly.  I think I used the TC4451 from Microchip as the gate driver chip.  I don't think it was very expensive.  It's been several years so I don't recall if that's the exact part I used or not.
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I also need to figure out how in the world i can drill threaded screw holes into a larger heatsink.
Not sure what you are asking but on the face of it all you have to do is to drill a hole of the tapping diameter for the thread you want. And then use a tap to cut the thread. If it is a blind hole you need three taps, a starting tapered tap, a bottoming tap and finally if you are doing it correctly a plug tap for that last turn.
http://www.amazon.co.uk/dp/B000PJDN9Q/?tag=hydra0b-21&hvadid=9557944389&ref=asc_df_B000PJDN9Q
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