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Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Carefully choose your resistor specs though. I experimented with resistors in the output of the driver and it only made the resistor extremely hot too
EDIT :
Bushman wrote ...
I had to design the layout myself as that does not come with the design instructions on the MiniBrute, so very likely I made a mistake there and it only manifests when there is a load on the driver IC. It's a complicated board so going to take a while to redo it, but running out of other options.
Sorry, I misunderstood you. I thought you meant that you etched the exact artwork available from EVR website.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
Hmmm, if you get tired of your board you could buy or obtain a minibrute control PCB fab from EasternVoltageResearch and load your components to his board
Are you sure you have the correct transformer material for your driver transformer? Is it saturating? You could get one of those from Eastern since they are cheep.
It would be easy to see of there is a problem with your bridge board by removing the transformer and get a variable voltage source like a current regulated power supply and connect it to the gate connection with the proper polarity (ie pos on gate) and go from 0 to 20vdc and see if there is any clamping. You shouldn't see any current from your power supply at all accept leakage current. Do this for each FET, IGBT at a time you should be able to get continuity from the drain to the source when you do this. If all is good then your bridge board is good.
change your coupling cap from 1uf to .1uf mono-ceramic if it helps it may not be permanent. you could add a 100 to 300 ohm or grater maybe (2W if necessary) in parallel. You must decrease the amount of the power being dissipated by the UCC IC to probe around it. You could reduce the interrupter pulse width from 50us to 100us. When you test are you using the interrupter? I personally don't think there is is any thing wrong with your driver because you have signal out of the transformer with out the bridge board. Another thing you could try is run the interrupter at a increasing frequency like 1 pulse group per second to 100 per sec and more all the whyle testing the temprature with your finger (carfull don't ge burned). start with no bridge board
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
I bought the cores from EVR as I wanted to be sure of the right material. Did not see an option to purchase just the PCB though. Will have to check again.
Thanks for the ideas on testing the H-Bridge board. I did try a 500ohm resistor but it destroyed the output signal and I didn't want to send that to the IGBT. I will try some DC supply testing like you suggest. I have been using a 200uS pulse interrupter - maybe worth playing around with that. Will try this suggestions and do some more testing. Thanks
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Physics Junkie wrote ...
It's only when I turn on either the modulator OR the signal generator that this problem persists.
Correction, after more testing I found that it too is only the modulator that's causing this. I can drive the IGBT's all day with just the signal generator and everything will be relatively fine, and by that I mean that the 15v regulator gets hot but no longer acts like its shorting. And with both the signal generator and modulator on, I get the same 'relatively normal' operation with some heating n the regulator. Nasty overshoots though on my gates . It is with ONLY the modulator on that the problems start. I monitored the voltage drawn from the regulator when the modulator gets turned on and it drops from 14.99 to a low 6.4ish. I am using F/O too so over voltage of the signal is not a problem. All i have to do is turn the signal generator on and everything goes back to normal. I pulled the regulator out as well as some caps to check them but no broken components... I too tried putting a resistor in parallel with the coupling caps and I also tried in parallel with the tantalum caps at the driver output, neither made a difference. I also tried a 1k pull down resistor at the enable inputs and that did nothing. To hell with it, might as well make a new interrupter at this point
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
One more thing in testing TVS's have lots of capacitance and clamp early maybe 15% under the rated volts so with a 33 transorb clamping is 28v. Just a thought.
an answer to Physics Junkie all regulators should be well heat sunk like a metal box or fat heat synk like a cpu synk
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
teravolt wrote ...
One more thing in testing TVS's have lots of capacitance and clamp early maybe 15% under the rated volts so with a 33 transorb clamping is 28v. Just a thought.
an answer to Physics Junkie all regulators should be well heat sunk like a metal box or fat heat synk like a cpu synk
Thats right. My heatsink is very bulky I attach it when I actually want to run the coil. But for troubleshooting I usually never have it attached, that way I could identify problems that I'm having such as over heating. Now its hot but its "normal" hot. I just need to figure out why the darn things wants to die every time I turn the modulator on. From my findings, theoretically I should be able to run my coil because I'm not seemingly having problems anymore when there is a feedback signal. Problem is that the feedback signal needs to be there first for the circuit to want to work. I've only ever experienced this with on board interrupter's running at 9V which I later learned is a no no. But for this I have no idea at the moment. What do you think is causing the 15V to drop down to 6ish with the modulator on?
Registered Member #4146
Joined: Tue Oct 18 2011, 02:01AM
Location: Wisconsin, U.S.A
Posts: 56
@ Physics Junkie I believe i have had the problem in the past with voltage sagging when i started making a DRSSTC. After i started paralleling up drivers i became a fan of the TC4421/22 TO-220 drivers. Since i haven't had any issues. I'm not sure if this is your problem but its a decent place to start if your seeing a major voltage drop off your drivers.
It all comes down to this in the end.
teravolt wrote ...
I don't think that those little drivers are going to be able to handle the capacitance that you are driving. you will need a driver that comes in a TO-220 package
Edit: The power dissipation for the TO-220 package is double of the ic based ones here is the data sheet If you parallel These up as in 2x4422 and 2x4421 they should be able to run just about anything you can throw at them.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
HB wrote ...
@ Physics Junkie I believe i have had the problem in the past with voltage sagging when i started making a DRSSTC. After i started paralleling up drivers i became a fan of the TC4421/22 TO-220 drivers. Since i haven't had any issues. I'm not sure if this is your problem but its a decent place to start if your seeing a major voltage drop off your drivers.
It all comes down to this in the end.
teravolt wrote ...
I don't think that those little drivers are going to be able to handle the capacitance that you are driving. you will need a driver that comes in a TO-220 package
Edit: The power dissipation for the TO-220 package is double of the ic based ones here is the data sheet If you parallel These up as in 2x4422 and 2x4421 they should be able to run just about anything you can throw at them.
I agree, but these designs have been successfully built by many people and I dont see why this wouldnt work still. Also, the voltage drop is initially coming from the voltage regulator I think. It may be the driver's fault if thats what you are suggesting.
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Gate Driver Problem
. It is with ONLY the modulator on that the problems start. I monitored the voltage drawn from the regulator when the modulator gets turned on and it drops from 14.99 to a low 6.4ish. I am using F/O too so over voltage of the signal is not a problem. All i have to do is turn the signal generator on and everything goes back to normal. I pulled the regulator out as well as some caps to check them but no broken components... I too tried putting a resistor in parallel with the coupling caps and I also tried in parallel with the tantalum caps at the driver output, neither made a difference. I also tried a 1k pull down resistor at the enable inputs and that did nothing. To hell with it, might as well make a new interrupter at this point 
