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Forum Index : Electronics : AC-DC or DC converter
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Revlac Guru  Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Thought it might be worth starting on this. I was after some DC-DC Converters to run a few things, there are plenty of options online but worth checking what may be sitting around unused in an old junkbox.  I have scavenged about half a dozen AC-DC converters that are of useful voltage output apart from 1 at 3v. some of the 5v usb phone chargers work on the 50v battery bank as well as a 9v unit that will be running a fan on the other inverter, and a 12 volt unit that might run the fans for the Mad inverter although it is only 1Amp. Also an old 24v Logitech AC-DC converter that used to run the force feedback joystick also runs well.  I have a 15V AC-DC converter however it refuses to run off the 50v battery bank, seems some of these things require a much higher voltage to run, would be a bugger to buy one and find that out later.   After reading on the other thread it might be worth while making some of these to suit what I want, depending on what parts I can find.  Also this might be useful for someone, Mosfet Current ratings Application Note AN-1140 Cheers Aaron Off The Grid |
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| hotwater Senior Member  Joined: 29/08/2017 Location: United StatesPosts: 120 |
See that 2.2M resistor. It is the boot up to get it started. On those converters that have trouble starting on 50V, change this to 270K. It still must be operated at reduced power. More than enough for most micro applications. The internal FET of the chip can easily be 35-40 ohms when on so there will be extra heating. Add some heat sinking. Those with external FET fare much better. Often there are filter inductors or resistors on the input. I short these out for lower voltage drop. Also, I'll remove all but one diode to eliminate that drop. Every volt counts. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Thanks Hotwater That works good now. This IC is SL2128 so the resistor connects to pin2, must be many different IC's around that are used for these. Thought it be worthwhile checking for any power spikes when powering up, after many startups, never saw any.  Its got me thinking about building one from the guts of these old ATX power supplies that are collecting dust, another job for later. Cheers Aaron Off The Grid |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1057 |
Hi Aaron, Have you got a link to the "Other Thread"? Thanks ChopperP |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
That would be Here UCC3808 was suggested 3rd last post I didn't want to interrupt poida's post so I thought it best to start fresh. Just been looking around the workbench, As messy as it is, there is some IC's that might be ok to make a little more powerful converter for another purpose. Have some IRS2453D H-Bridge Driver and Sg3524 which there is actually 1 used in My PIP inverter (that was taken out by lightning long ago), using transformer driven totem pole driver's, not sure if it was running 26khz? Just getting a few ideas. Cheers Aaron Off The Grid |
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| hotwater Senior Member Joined: 29/08/2017 Location: United StatesPosts: 120 |
Most any converter works the same way. I just bought a broken XANTREX power supply. That had a reverse problem. The boot up circuit worked so you could hear it tick and try to start up every second. It then wouldn't run long enough to supply enough power to keep running. Love getting a nice supply that sells for $700 used for only $60. |
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