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Old 12-02-2011, 08:28 PM   #11 (permalink)
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Nice Adam - lets throw it in a Battle-bot

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Last edited by dave koller; 12-19-2011 at 05:31 PM.. Reason: gotta spell ---- gotta spell
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Old 12-03-2011, 07:14 AM   #12 (permalink)
Mark Weisheimer
 
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Nice work Adam!

Which isolated DC-DC(s) are you short?
I have a spare for a P&S controller for certain. Would that work?

Mark
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Old 12-03-2011, 10:16 AM   #13 (permalink)
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Quote:
Originally Posted by Weisheimer View Post
Nice work Adam!

Which isolated DC-DC(s) are you short?
I have a spare for a P&S controller for certain. Would that work?

Mark
Hey Mark,

That dc-dc is of the same series, but is the wrong output.

The new board uses 2 dc-dc converters for full 3kv isolation. One of the converters is for 5V output and the other is 15V output for driving the igbt's. I designed the output section to use both 12v and 15v output modules so that you can use the 15v one for powering the vla500's and you can use the 12v output one to power a modfet driver board.

Here is a link to the 2 dc-dc converts:

15V: EC4A03H Cincon DC/DC Converters & Regulators

5V: EC4A01H Cincon DC/DC Converters & Regulators

-Adam
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Old 12-03-2011, 07:59 PM   #14 (permalink)
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OK, I think that I understand.

The board can be populated at one spot with either a 12v output DC-DC for mosfet drive, or a 15v module for IGBT driver.
The second spot is for a 5v output module in each case.



For testing, I sometimes use old laptop/TV powerpack/charger modules.
They are mostly quite well isolated, but one has to check to be certain.
Just be careful with cell phone chargers as they more commonly lack full isolation.

Sometimes they are big and ugly, but allow testing and further refining to continue until you can get the proper module.
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Old 12-03-2011, 09:52 PM   #15 (permalink)
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Quote:
Originally Posted by Weisheimer View Post
OK, I think that I understand.

The board can be populated at one spot with either a 12v output DC-DC for mosfet drive, or a 15v module for IGBT driver.
The second spot is for a 5v output module in each case.



For testing, I sometimes use old laptop/TV powerpack/charger modules.
They are mostly quite well isolated, but one has to check to be certain.
Just be careful with cell phone chargers as they more commonly lack full isolation.

Sometimes they are big and ugly, but allow testing and further refining to continue until you can get the proper module.
Yes Mark,

I plan to find a 5v supply and I have a 15v industrial supply kicking around. Now that I think of it, I have a 5 v one as well. I will probably use these for the tests.

-Adam
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Old 12-12-2011, 12:54 PM   #16 (permalink)
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Well this weekend I was able to start testing the 3 module driver board. I assembled the driver section up to the gate resistors. I started adding gate resistors with just a 3R3 for on and off. This yielded slower then I had thought rise and fall times.


Untitled by AdamBrunette, on Flickr


Untitled by AdamBrunette, on Flickr

Heres a scope shot of the single 3R3 gate resistor. (Switching at 16kHz)

3R3GateOnOff by AdamBrunette, on Flickr


After this, I decided to speed up the turn off as much as I could without going overboard. The recommended gate resistor value is 3.1R so I went a little smaller with 3.0R. This is put in parallel with the 3.3R with a ultra fast diode blocking it from being used for turn on. This yield's about 1.57R for turn off. This dropped turn off times from 1.14uS to 720nS. This is still considerably slower then the 250nS fall time in the spec sheet. The spec sheet is talking about switch side and not gate side though. This could all change later today when I connect an actual battery and load motor.

Here is a scope shot of the rise. (Switching at 8kHz)

3R3On 3ROff Rise by AdamBrunette, on Flickr

Here is a scope shot of the fall. (Switching at 8kHz)

3R3On 3ROff Fall by AdamBrunette, on Flickr

On a side note, I have been doing some loss simulation calculations and have found out that in order to get the 1000A out of 3 modules, and keep them from overheating, The controller will have to run at 8khz.

Here are screen shots of 16khz and 8khz. Look at switching loss's for each and junction temp average.


Screen shot 2011-12-11 at 11.14.14 PM by AdamBrunette, on Flickr


Screen shot 2011-12-11 at 11.14.01 PM by AdamBrunette, on Flickr

-Adam
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Old 12-12-2011, 03:33 PM   #17 (permalink)
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Nice work ,I am sure you keep away from the little parties scattered here and there at this time, to keep your work in progress.Keep it up.
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Old 12-12-2011, 05:29 PM   #18 (permalink)
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Don't forget that your gate waveforms will differ greatly when driving the transistors with no load or dc bus than when driving on load. That pesky miller effect really takes its toll!
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Old 12-19-2011, 05:05 PM   #19 (permalink)
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Well I spent some time this weekend tuning the driver board. I ordered new carbon composition resistors and matched them in groups of 4 to make specific high tolerance values.

I first started with 3.0R because I messed up with my meter and didnt offset the lead resistance of 0.1R. Heres a shot of what That looked like on the scope.


NewFile7 by AdamBrunette, on Flickr

You can see the turn off was ringing like crazy. It would actually turn the switch fully on with the ring.

I then went to 3.65R and it started looking alot beter. But im curious why there is still such a large ring... I plan to try 4 parallel 16R resistors for about 4R gate resistance and see if that helps. I want to stay as small as possible because switching loss's are already high enough. I dont want to counter my slower 8khz frequency with long switching times.


NewFile17 by AdamBrunette, on Flickr

The turn on of the module has always been pretty good.

NewFile8 | Flickr - Photo Sharing!

Here are the shots of turn on and off with the 3.0 gate resistor. They look pretty good.

Turn on:

NewFile1 by AdamBrunette, on Flickr

Turn Off:

NewFile2 by AdamBrunette, on Flickr


Heres a longer time withe the gate off for comparasion


NewFile20 by AdamBrunette, on Flickr

This is where I left it. About 33V spike on turn off. This is down from about 68V!!


NewFile22 by AdamBrunette, on Flickr

Heres what damien was seeing on his controller. 5V/div 20uS/div

ce1 by AdamBrunette, on Flickr

More testing tonight!!

-Adam
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Old 12-19-2011, 05:38 PM   #20 (permalink)
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I have used ferrite beads with Bots to quench the ring - that help?

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