Adjustable 35V regulator PCB

rensli

Member
2014-07-14 10:00 pm
Hi,

The scheme comes from
DIYfan: Adjustable Lab Power Supply - take two :)

Had some TLE214x opamps laying around. Decided to paint a PCB, using V2 schematic from the link.

The idea was to make it compact and be able to mount outputs directly on the board avoiding long unnecessary leads or wires.

As i was all ready using the V3 schematic from the upper link, i did some mods by adding Cad-adj. capacitors AND input ceramics to regulators years ago and it is still working(two units). But, still had minor problems with reference voltage on V3 schematic when load was connected to the output(6.1R). Reference then moved from 9.4V to 10.x volts. Regardless of that reference jumping up and down, it is still quite stable, the V3 schematic, will replace them as soon as second V2 will be ready.

So, i re-present to you V2 with some mods for improvement in layout and schematics. Reference is always stable at 9.29V.

[IMGDEAD]https://www.upload.ee/image/5806399/schematdiagr.png[/IMGDEAD]

Changes:

*165mR as a current sensing resistor on the ground path(in series with the load)
*LM317AT and LM337AT for both positive and negative supply's, they are very robust and floating, those allow for higher input voltage ranges.
For the LM337, some cheaper brands like fairchild LM337T could be used, as i did in my test setup below. Working well.
*Cad-adj. 10uf capacitors, outputs capacitor 10uF
*Trim-pots for higher variable parameters.
*3 output devices max.

Few notes:
**2x330mR resistors in parallel can get pretty hot in a longer run @ huge current. I would recommend to use 4x470mR all in parallel, 2 beneath the PCB and 2 of them on the top side.
For example, i have used 2x330mR on the V3 for years, never had problems.

**All the Trim-pots should be adjusted to a half of the rated resistance before soldering into the board. This way you insure that regulator will start on nicely.
**I have decoupled opamps with 10nF X7R 50V capacitors, works, it will propably work without all of these ceramics too.
** LM337 input DC voltage must be measured and this can't be greater then 35V !!
**Connections from bridge rectifier are possible only from bottom side of the board, look at the photos. That way you can add few more capacitors in parallel on each side :D

I have powered everything with this PSU(V3), computer perhaps, notebooks, audio projects and so on. Modified schematic should be no different from V3 in terms of reliability.

Recommendations:

*330pF capacitors should be COG or NPO ceramics.
*220nF MKS
*Do not add small film or ceramic capacitors in parallel with Filterbank electrolytes.
*Signal resistors 0.4W or lower.
*Do not use less then 2.2mF rated capacitors. LOW ESR preferred a MUST!.​

In overall, do not use this circuit to charge batteries for 24/7 or start huge motors and pumps all day long :D Get SMPS then.

The design is depending on your transformer specifications, more powerful transformer(higher voltage, higher VA-rating) means more regulated volts and amps. Theoretically it is possible to get 40V @ 6.1R load with 60mV drop with the presented schematic in here.

The TEST:

Xformer that i used is putting out 35V AC, this converts into nearly 50V DC.
Type is un-identified, from the size and voltage drop, it is atleast 200W+ covered with Epox type material.​
No emitter resistance and everything else is seen on the photos.

I will try the circuit with 5534 and 5532 opamps later :D

NB! Use 100R resistor as a current limiting when powering a regulator first time !

Everything from the 0 to finish is here:
UPLOAD.EE - Everything_u_need.zip - Download
 

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rensli

Member
2014-07-14 10:00 pm
Time has passed, work is done... but not yet this one.

I had my time to complitely move from Eagle Cad to KiCad... this gave me oppurtunity to give out Healthy Gerber files.

Decided to go little over the top and build 4 channels into the one case.

2 are identical to the description above and the rest are on the attetchment...

LM317 and LM337 with shortcircuit protection, variable, optoisolated.
This is simulated and constracted on breadboard, worked fine.

Will share the files when PCB's arrive and populated.
 

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rensli

Member
2014-07-14 10:00 pm
Okey, here is the so called "audio Bench psu" :D:D
It is exactly what it is... i have not yet tried to listen to it... will do in near future :D
Lowest impedance in series from transformer windings to the PSU DC regulated output. NO FUSES this time:)

New LM317/337 PSU is built in also which can be regulated from 1.28V to the 25V @ 150mA from + to ground and from ground to -.
I still can't give out the schematic.. cuz there is some problem with current limiting circuit.

It works, if Shorted from either NEGATIVE OR POSITIVE to groound, it acts like a current source then, good.
BUT, if SHORTING NEGATIVE AND POSITIVE TOGETHER then current limit does not work.
MAIN 2x 35V 5A per channel works and gives good results on the multimeter under various loads and shortcircuits.
 

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