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Old 10th January 2007, 08:11 AM   #21
luka is offline luka  Slovenia
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WoW
0.o

Now this is just beautiful, you probably can't add the schema if you have it, can you?
This would be perfect for small scale one. If it is not that difficult, could you add a picture of bottom side.

Great, great job done here.
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Old 10th January 2007, 11:05 AM   #22
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Thanks Luka. Yes, I will get to the schemo tonight, and a pic of the underside, too. The board's dimensions allow it to fit inside the enclosure of a gutted Dell laptop power supply. Showed it off at my ham radio club's monthly meeting last night. 2 guys wanted one each.
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Old 10th January 2007, 06:21 PM   #23
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Default The Good, the Bad, and the Outright UGLY!

I must warn you, though, that it is not pretty. My lame-a$$ version of wave soldering has left some copper exposed on the underside, which has begun to oxidize. I could pretty it up with a little Scotch Brite scrub pads................
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Old 10th January 2007, 09:54 PM   #24
luka is offline luka  Slovenia
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Hi Steve

What is input/output voltage and what is its power ?
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Old 11th January 2007, 04:13 AM   #25
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Well,

Since you ask, it will work all the way down to 8V (the SG3525's UVLO is from 6-8V), and up to, say, 16V? Its output is switch-selectable at either 16- or 20V. This was originally for a friend, but when I powered it up, I promptly blew a 10A Slow-blow fuse. I panicked and built him a 2-chip SimpleSwitcher, instead, and kept this one for myself. After a couple of months looking at it on the shelf, I rolled up my sleeves and set about troubleshooting it. Turned out there was a solder bridge from one of the 3525's outputs to ground, killing the 3525. Fixed it and popped in another 3525 and tested it. Waveforms looked good, and got progressively fatter as I increased the load. At 20V out, I loaded it with a 4W 10W power resistor combo, only for a few seconds. At the 20V setting, it dropped only 30mV from no-load to full-load. MOSFETs, diode and PWM chip all stayed cool, but core heated a bit then stabilized out at ~30 degrees Centigrade.

I have tested it up to 5A, but I believe it could go higher because the MOSFETs are 75N06s, and the MBR2545CT Diode is rated for 25A (12.5A per leg). Here are a few pics of the underside.
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File Type: jpg sg3525 uppie underside 1 (650 x 488).jpg (94.5 KB, 2393 views)
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Old 11th January 2007, 04:14 AM   #26
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Default Underside #2

Next one...............
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File Type: jpg sg3525 uppie underside 2 (676 x 507).jpg (97.4 KB, 1436 views)
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Old 11th January 2007, 04:16 AM   #27
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Default ...and the Last one.

Here goes........
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Old 11th January 2007, 06:27 AM   #28
luka is offline luka  Slovenia
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Hi Steve

Looks bad?That is not bad at all... I have seen worse that came from myself, but at the end it did still work

Where is schema? I've must missed it somewhere...
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Old 11th January 2007, 01:56 PM   #29
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Fell asleep at the keyboard as I was uploading the last pic. Needless to say, I didn't finish the schemo yet. 4-day weekend coming up, not too many projects, so I will git-er-done today or tomorrow, and then upload it.

Oh, if I only had a wave solder machine (and a pc board-making company..
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Old 11th January 2007, 02:28 PM   #30
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I'm also contemplating something like this to power my laptop from the car lighter plug.

I need something at 12Vin and 16V @4.5A out. would a boost converter be fine or the current draw be too much for that topology? low ESR caps are nowhere to be found here.....

I'm thinking of making two units, a boost converter for a friend (same laptop requirements) and mine would use a half bridge (similar to a car amp's but only one output)

what would be a better/easier way to go?
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