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0-30V Stabilized Power Supply


redwire
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please fix my schematics.. i don't know why it is not working properly..

how should i set the 2 potentiometers and the 3 trimmers to know the maximum and minimum voltage i can get?

i couldnt find MC34071 here in philippines.. then i researched about its equivalent.. there i found TL081.. so thats what i used as substitute for MC34071.. is this right?

i will be using 30V 4A = 120W Transformer.. is my AC source in the schematic right?

why is my output voltage varying and not stable..

thx in advance.

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please fix my schematics.. i don't know why it is not working properly.

how should i set the 2 potentiometers and the 3 trimmers to know the maximum and minimum voltage i can get?

i couldnt find MC34071 here in philippines.. then i researched about its equivalent.. there i found TL081.. so thats what i used as substitute for MC34071.. is this right?

i will be using 30V 4A = 120W Transformer.. is my AC source in the schematic right?

The fixed and corrected project will not work with TL081 opamps!!!!
I selected Motorola (ON Semi or another name today) and Texas Instruments opamps because they do what is required and are available almost everywhere. Their max allowed supply is 44V.
The max supply for a TL081 is only 36V so it will probably blow up. (the 30VAC transformer will have an output of 31V or more with no load, then the positive unregulated supply will be 42V. The TL081 needs a negative supply that is at least -4V which is not provided and would result in a total supply of 46V which is 10V more than its max allowed supply!

The MC34071 and TLE2141 opamps do not need a negative supply but the TL081 opamp needs a negative supply of at least 4V. The 1.3V negative supply is provided in the improved circuit so that U3 can turn on the diode to reduce the output voltage when the current is too high.
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now its MC34071.. its voltage is at 53V.. still not correct..

It is impossible to get +53V when you rectify and filter 30VAC.
The peak voltage is 30V x 1.414= +42.4V and the full-wave bridge rectifier drops it to +40.4V.
The max output from the project is about +35V when it is loaded then the calibration trimpot drops it to a max output of 30.0V.

i really cant find MC34071 or TL081.

You do not want TL081 opamps. You need MC34071 or TLE2141 opamps.
Farnell used to have an office in the Philippines but now it is called http://ph.element14.com and they stock both opamps.

how about this OP Amp Dual GP22V/44V 8-Pin SOIC
http://philippines.rs-online.com/web/p/products/7092154/

Why don't they call it by its real name? It is a surface mount TLE2142 which has two TLE2141 opamps inside. But it is tiny so it might over-heat.
RS components have the TLE2141 in a normal DIL package.

Your "remake schematic" has the wrong value for RV3.  It should be 100k ohms.
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they finally restocked MC34071 here in philippines.. i hope when i buy they wont run out again..

is my 30V 3 A transformer the right transformer to use?
(JUST FOR SURE I GOTTA ASK FOR THE LAST TIME.. thanks a lot for the patience)

i am also having a problem how to set the potentiometer and trimmers in the multisim to know the minimum and maximum voltages..

pls correct my schematic again.. if i set my trimmers to 100(i prefer 100 is the maximum) and potentiometers to 100.. voltage is somewhere 20 then an error message.. what to do?

is it alright to have MDA980-1 as bridge on multisim.. which has 12-30 Amps and 50 to 600 volts.. or should i stick with the 4 1n4148 diodes?

later il buy this KBPC10005 which is a 10 A 50V diode bridge available in the philippines.. is this alright?

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Fly3rman ,    The pcb you reference was copied from the 1st post  on page 1 and is still current.    Given it is a double sided board it is a little more difficult to build at home.   I had some commercially made pcb's  from that board file so I know it works.


Thanks for answering and thanks for the PCB. I also crosschecked it yesterday and and seems to be fine, only some values differs.

Alignments its a little bit tricky but there is still some leeway. Ill finish the toner transfer to the 2nd side today and etch this one.
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is my 30V 3 A transformer the right transformer to use?
(JUST FOR SURE I GOTTA ASK FOR THE LAST TIME.

No.
It will overheat. It can supply 30V at 3A which is 90VA.
But the rectifier works with the peak voltage that is 42.4V so when the project has an output of 3A then the transformer must supply 42.4V x 3A= 127.2VA.
Use a 28V or 30V transformer rated at 4.2A.

i am also having a problem how to set the potentiometer and trimmers in the multisim to know the minimum and maximum voltages.

Build it and adjust it without fiddling around with Multisim.

pls correct my schematic again.. if i set my trimmers to 100(i prefer 100 is the maximum) and potentiometers to 100.. voltage is somewhere 20 then an error message.. what to do?

Multisim doesn't work properly.
If the pots are at maximum then reduce the settings of the trimmers until the max voltage is 30.0V and the max current is 3.0A.

is it alright to have MDA980-1 as bridge on multisim.. which has 12-30 Amps and 50 to 600 volts.. or should i stick with the 4 1n4148 diodes?

Forget about Multisim.
The MDA980-1 has a max voltage rating of only 50V which is very close to the peak voltage of 42.4V produced by the transformer. The peak voltage might be 44V without a load and power line spikes will be higher. Use a MDA980-2 that is rated at 100V.
A 1N4148 is a tiny low current signal diode, not a power rectifier.

later il buy this KBPC10005 which is a 10 A 50V diode bridge available in the philippines.. is this alright?

No.
Use a diode bridge with a 100V rating.
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i thought this project's Bridge needs to be 6-10 A / 50V diode bridge module.

Correct. But a 100V one is much better.

may i also ask if the 2 pcs. 2N3055 needs heat sinks also.. 1 for each?

Of course the output transistors get very hot and must have a heatsink. Use one very big heatsink for both or use a smaller but still pretty big heatsink for each one. When the output voltage is low or shorted and the current is set to 3A then each 2N3055 transistor must dissipate about 59W of heat.
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Hello all,

My PCB is made, and all components have been purchased, but I had one question I need some assistance with.  I am making the 5A version, with three MJ11016G paralleled transistors.

My question is:  I'll be using three emitter resistors (0.33 Ohm 5W), but I'm a little unclear on how I should wire them.  My initial thought is to wire each one in series with the emitter before I connect all three emitters together for the parallel connection.  See pic.

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I was gonna ask if you've revised your schematics.



It sounds like you are looking at the original version (and it is a kit) that has many problems.
The latest version has been posted here in these threads many times.

It uses a 6A to 10A rectifier bridge module that can be bolted with heat sink compound to a metal chassis or a heatsink. The original little 1N5402 diodes smoked and burned.
Of course it needs two 2N3055 output transistors each with an emitter resistor and the driver transistor is a BD139 mounted on a heatsink.

Here is the latest schematic and parts list:


Found it though! :D

I've been creating different power supply from different sites with different designs and it seems I'm not satisfied with the results.

Anyways, can I replace 2N3055 with Toshiba's 2SC5200 or 2SC5198? This is what I have for now.
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Hello audioguru,

can I ask which of these transistors I can replace for 2N3055

2SC5198
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7886.pdf

2SC2922
http://www.sanken-ele.co.jp/en/prod/semicon/pdf/2sc2922e.pdf

2SC5198
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7890.pdf

I have these transistors in my work bench and if possible, I could use them in this project. ;)
But I don't know if it can replace 2N3055.

Thanks in advance!

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Hello audioguru,

can I ask which of these transistors I can replace for 2N3055

2SC5198
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7886.pdf

2SC2922
http://www.sanken-ele.co.jp/en/prod/semicon/pdf/2sc2922e.pdf

2SC5198
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7890.pdf

I have these transistors in my work bench and if possible, I could use them in this project. ;)
But I don't know if it can replace 2N3055.

Sorry but I don't have time to look at the datasheets of your Oriental transistors.
The spec's for a 2N3055 transistor are a Vceo of 60V, a minimum hFE of 20 at 4A and a max power dissipation of 115W. If your transistors are the same or better then they can be used.
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