DIY lab power supply +/- 200V 2A

[LZ1TWB]

Hello, I am in a process of building this double PS for my home lab here and need some advice.

I have two transformers around 400W each, which output 50, 100 or 150V AC. On the high voltage, rectified and smoothed I should get 200V DC. I can change the winding so If I need lower voltages, I could get higher current and less heat in the output transistors. There will be two independent positive stabilizers, which can be connected in series so I can get the +/- output.

The problems is I cannot decide which linear regulator IC to choose for that particular situation. Most of them are designed mostly for lower voltages, but the thing here is different.

I hope you could point me to some device, so I can continue with the design.

Thanks

[tommylight]

That is way to much dissipation for a linear P.S. so you would have to go with SMPS. You would have to deal with electronics that can handle 500 V for linear and nearly 1000 for switch mode.
It is much easier to make 2 or 3 of them for a certain range.

[LZ1TWB]

Hello

Dissipation is not a problem here, I have big, heavy radiators. I never wanted smps for a lab supply, they have their benefits, but I just don't like using them that way, so I'll go with linear.

Last few days I was searching the net for a suitable schematic and ended with the good old LM723 IC. I found a kit of a lab supply 0-30V 0-10A variable and will use it as a reference for my design.

The idea is to have three ranges:
0-60V 0-8A
0-120V 0-4A
0-180V 0-2A
I am still not sure how I am going to change between the three. The easiest way is manually, but I think I'll make it automatic.

That's for now, I will be posting when I make some progress.

[vger]

I used to have a linear supply that was 0-250 V at 40 amps. It was 3 phase 208 input. The transformer was the heaviest part and the heat sink for the transistor pass bank came in second. There were 4 rows of high voltage NPN transistors all paralleled with series ballast resistors on each transistor. The resistors were also attached to the heat sink.

The thing had 2 water connections that went to the heat sink and you just ran city water through it to keep it cool.

I agree with you on the use of linear supply as a lab supply. Too many quirky issues with adjustable switchers.

[LZ1TWB]

Can you give me some info about your supply, was it branded or it was a diy project? I am interested in its schematic.

Happy new year .

[vger]

LZ1TWB,

I think it was a Sorensen supply, but it was made in the early 70's so finding the schematic for it will probably be impossible. I do know that ION laser supplies were designed in a similar manner so take a look at this one....

http://www.repairfaq.org/sam/sgilpsch.pdf

That one controls the current through the tube on the negative (cathode/filament) end but the pass-bank section gives you the idea of how the paralleling works.

Steve