Driver problem

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Driver problem

Postby Gilly » Mon Oct 01, 2007 1:53 am

My 80M Transmitter has been going well but has developed a fault do to the driver chips...
It uses 2 IRFP450's in parallel driven by 3 UCC37321's...
The 3 ICs get too hot and shut down and with 1 FET are OK and are cool...
Maybe will have to add at least 1 more to drive the 2 FETs although were going fine..
Perhaps I was lucky to get away with this for so long and never realised they were so hot...

Would anyone know how many should work...To double up using 6 makes my circuit board rather crowded...


Thanks


Wayne
Gilly
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Postby frank carcia » Tue Oct 02, 2007 11:25 am

I had the same problem with 4426s. I had 5 in parallel and had to remove 2. They were fighting each other. The best thing to do is have 1 driver drive 1 FET or 2 drivers driving 1 FET. I had the outputs isolated with 10 ohm resistors and they still cooked. I tried all kinds of different bypass caps with little luck. You might consider a better driver chip. fc
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Postby Gilly » Thu Oct 04, 2007 8:05 am

Thanks Frank

I tried using just 1 driver into one FET but they still get too hot and shut down.
Are ordering some IXDD414's and will try them when they arrive and let you know...


Thanks

Wayne
Gilly
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Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Postby Gilly » Thu Oct 04, 2007 8:05 am

Thanks Frank

I tried using just 1 driver into one FET but they still get too hot and shut down.
Are ordering some IXDD414's and will try them when they arrive and let you know...


Thanks

Wayne
Gilly
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Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Postby frank carcia » Thu Oct 04, 2007 10:42 am

I bought a bag of them from Steve but have not tried them yet. Nice thermal interface should keep them cool.
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Postby WA2WVL » Thu Oct 04, 2007 11:42 am

I had a power supply driver chip that got too hot. I solved the problem by bolting a flat piece of 1/4 inch aluminum across the top of the chip
which gave enough additional cooling.
Floyd
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Postby Gilly » Fri Oct 05, 2007 5:49 am

Hi Frank and Floyd

Looking at the IXDD414 they certainly look as though their designed to get rid of the heat using the TO-220 package.
The UCC37321 uses the DIP.
The way I made my driver board is to mount the DIPs upsidedown and mount the components directly to the legs etc:
I find this a quick way to make things but it means dismantling everything to place a heat sink under.
Will set one up on my experimental board and try...


Thanks


Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Postby Gilly » Fri Oct 05, 2007 5:50 am

Hi Frank and Floyd

Looking at the IXDD414 they certainly look as though their designed to get rid of the heat using the TO-220 package.
The UCC37321 uses the DIP.
The way I made my driver board is to mount the DIPs upsidedown and mount the components directly to the legs etc:
I find this a quick way to make things but it means dismantling everything to place a heat sink under.
Will set one up on my experimental board and try...


Thanks


Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia


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