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morpheus82 29th June 2006 03:20 PM

diy dual lab power supply
hi all!
i'd like to build a lab psu...think dual about +/-50 volt adjustable,1 amp ,just to test some diy cicuits...anyone has some schematics and/or pcb?
everything is welcome!!

morpheus82 5th July 2006 08:11 AM

so...i think this silence means that everyone has got his own psu...and everyone has bought it!nobody build it?seems to be impossible...:smash:

Greg Erskine 5th July 2006 09:04 AM

Have a look in the Power Supply Design forum.

There must be something there. :confused:

morpheus82 5th July 2006 09:09 AM

i thought it too...but nothing about variable supplies...i've got some ideas but if someone can post a diy one, just to have some other data...please!!:bawling:

AndrewT 5th July 2006 09:34 AM

the power dissipation becomes enormous if you use maximum current output at minimum voltage output.

Lab supplies often use relay connected multi-tapped secondaries to match the secondary voltage to the required output voltage.
You can hear the relays switching as the voltage setting is adjusted up or down.

A modern version could maybe use solid state switching (what VFETs are really designed for).

Add in dual metering, monitoring both current and voltage on both channels.
Arrange your grounding (floating) so that you can, optionally, series connect the outputs for double voltage. My one also allows parallel connection for double current.
Add adjustable constant current limiting, great for a new project to prevent destruction.
Voltage tracking supplies when in normal dual +- mode would be nice to have.

peranders 5th July 2006 09:42 AM

You could check my QSXPS. Possible modifications:

A "tripleton" output stage instead of Darlington (two transistors)

Feed the opamp with stabilized voltage (max 30-36 Volts)

Variable current limitation

Max sure when you choose an opamp that it can take zero volts at the inputs (common mode limits)

Feed the voltage reference not from the stabilized side.

If you want substantially more output voltage than the opamp can handle you can check the output stage of a super regulator.

There are also lot's of other ideas. Elektor had long time ago a PS which used two transformers and the main thing was a current generator as reference. I have built it but the schematics are available, some help me? The article was published in the mid 80's.

The idea of Elektors have I seen in commercial lab PS and it's pretty good.

destroyer X 5th July 2006 10:00 AM

This one is beeing used last 35 years, and modified
2 Attachment(s)
Are also beeing used by 22 local Radio Amateurs.

The HAM use 20 amperes and 13.8 volts, and this must be hardly stabilized, as current jumps from 1 ampére to 20 amperes in a flash time!..... following the audio signal, when using suppressed carrier transmissions.

Of course the input voltage and many resistors are different to receive 24 Volts DC in its input.

This one works fine.



AndrewT 5th July 2006 10:19 AM

destroyer's posting looks good for about 4A or 5A upto 50V or so.
The pass devices could be 3 pairs of MJE15003/4 (750W & 60A)

That would take some cooling when set to 5A and 5V (600W of dissipation), hence my tapped secondary suggestion.

destroyer X 5th July 2006 10:44 AM

Yes...of course bigger transistors in parallell
2 Attachment(s)
Here is some image of the simulation.

One without load and the other with load.

Of course the transistors must hold the VBE voltage the maximum needed current and adequated they need ot be changed when you change your need.

Also resistors and zener need to be adjusted...also the electrolitic condensers need to be adjusted to the needed working voltage.

But this you already know.

regards...and be happy!


destroyer X 5th July 2006 10:45 AM

As you can see friends, this is only a low current and low voltage supply
2 Attachment(s)
But works as an example.... adapting values, it will work with bigger voltages too, and i normally use them.....never had problems...voltage stable under 5 percent normally.

Sometimes i can have better regulation.

I will stop to feed this thread, as we have correct place to that....answered here just to be kind with the one opened the thread...but i am finishing my cooperation here, not to broke, too much, our forum rules of organization.



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