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Old 12th May 2008, 04:20 PM   #1
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Default Any interest Car SMPS

A while ago I designed a real big dual torroid car SMPS with 16 IRFZ 44 fet's powering the two torroids, its unregulated and using a TL494 PWM controller and plenty of capacitance on the PCB.

This thing has served me well and been very reliable.

I havn't done any serious measurements yet but it can draw well over 100 A at 14V so I guess the output is also well over 1200W at 40-0-40V

I am prepared to draw up the schematics, but I first need to know if there's any decent interest?
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Old 12th May 2008, 07:50 PM   #2
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Default Picture top

Here is a picture of the top, the stuff on there was fibreglass resin which I should have never used
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File Type: jpg smps top.jpg (80.0 KB, 746 views)
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Old 12th May 2008, 08:00 PM   #3
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Default PCB pic

This one is of the circuit traces, I needed all of the solder because of the currents involved.
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Old 12th May 2008, 08:00 PM   #4
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Hi Ricsmuts,

Very nice! Could you please post the schematic and any other info? Do you have a printable layout of the PCB for etching?

Thanks!
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Old 12th May 2008, 08:08 PM   #5
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I'd like to see it, too!

How long has it been in service and what have you used it with?
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Old 12th May 2008, 08:15 PM   #6
wg_ski is offline wg_ski  United States
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Aren't those rectifiers just a liiitle bit small to go pushing that much current through? I would have thought TO-247's would be needed. I see no ouput filtering chokes - my guess is you built the trafos with enough leakage reactance so the charging currents of those big-@** caps don't smoke the rectifiers?

Of course we're interested. Especially in the specifics of your magenetics :-) Frequency, perm, turns, # and guage, leakage reactances....
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Old 12th May 2008, 08:29 PM   #7
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Default Schematic

I am going to have to redraw the schematic as it was lost a little while ago, this will take a little time, so please be patient.

I do still have the layout of the PCB traces I can send you, and can list the components and placement if you like.

I decided to share this design because there is nothing out there of it's size that anybody seems to have published, and this was one of the things I have built I got correct from the beginning. It's alo uses a TL494 like the commercial amps and not the SG chip.

The SMPS is basically a dual supply controlled by one TL494 and the outputs of the two supplies are regulated, filtred and joined at the end, but can be split for two channels if needs be.

It's loosely based on the common commercial circuits by reverse engineering several amps and with some features removed. The duty cycle is 50% unregulated and it runs at +/- 2Khz

This SMPS runs cool, has never overheated, and provides more than enough power for 4 X 15" 800W subwoofers, which was my original design goal, but I may have over engineered this one just a little...

The worst part is winding the torroids, as if the wrong cores are used and they saturate the explosion is quite impressive
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Old 13th May 2008, 01:10 AM   #8
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Quote:
Originally posted by wg_ski
Aren't those rectifiers just a liiitle bit small to go pushing that much current through? I would have thought TO-247's would be needed. I see no ouput filtering chokes - my guess is you built the trafos with enough leakage reactance so the charging currents of those big-@** caps don't smoke the rectifiers?

Of course we're interested. Especially in the specifics of your magenetics :-) Frequency, perm, turns, # and guage, leakage reactances....
It very much reminds me of a supply I have from a commercially available amp. It has the same amount of MOSFETs and the same TO-220 rectifier setup. No problems with smoked rectifiers either.

Click the image to open in full size.
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Old 13th May 2008, 06:41 AM   #9
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Default Good point on the rectifiers

Havn't blown them yet, but have been waiting for the bang.

The rectifiers are 25A each with surge ratings of about 50A, but output chokes would be an excellent idea, I also omitted to put chokes on the input which should be nescessary I would think.

The TL494 does a soft start which is probably why it's survived.

The only filtering that's added is the RC filter on the output rails- RHS of picture that quenches any ripple above about 30Khz. They do get quite warm, so they must be doing some serious work.

I need everybody's ideas, and then I will redraw the schematic with the improvements.

Stability and safety is what I'm after because when these babys blow, they go into thermo nuclear meltdown till you cut the power.
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Old 13th May 2008, 08:33 AM   #10
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Default That PS is interesting

What's it from? Similar layout and I see there is an op amp on that board, looks like a protection circuit.

With all those fets, I think decent size transformers are needed, but I wonder what the minimum is?
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