0-30 Vdc Stabilized Power Supply

[audioguru2]

Since the D8 ref voltage is also used in U3, why don't we put a filter before U3-P3?

Good point! ;D
Without a filter then maybe the current regulation is noisy.

 

[indulis]

Prior to the current limit threshold, U3 is "acting" like a comparator, sitting at the positive rail waiting for the voltage across R7 to increase. Unless someone wanted to use the supply as a "regulated current source" whiles it's in current limit, does current regulation matter?? Not that it isn't a good idea, but I can't think of a reason why a "typical hobbyist" would care.

 

[jiangrm]

Prior to the current limit threshold, U3 is "acting" like a comparator, sitting at the positive rail waiting for the voltage across R7 to increase. Unless someone wanted to use the supply as a "regulated current source" whiles it's in current limit, does current regulation matter?? Not that it isn't a good idea, but I can't think of a reason why a "typical hobbyist" would care.

Agree. I want to make it a CV/CC PSU.

 

[audioguru2]

At any moment, it an either regulate the voltage to be steady when the current changes, or it can regulate the current to be steady by reducing the voltage when the load tries to draw more current than its current setting.

 

[faizanbrohi]

Can you attach the suggested parts list . i have everything except the OPA series Op amps , can you suggest any other opamp.

 

[audioguru2]

If you use a 30VAC transformer to allow the output to provide a well regulated 30VDC at 3A, then without a load the unregulated positive voltage will be about +43.8V. Then the total supply voltage for two of the opamps is 43.8V + 5.6V (negative supply)= 49.4V which is too high for 36V and 44V opamps. The OPA445AP is the only high voltage opamp I could find.

Where in the world are you? The OPA445AP is made by Texas Instruments and is very common in North America.

Here is my recommended parts list again:

View attachment 39475

 

[esil]

24V AC is a standard Voltage Output of common transformers, that's why this circuit was designed for this voltage. A few volts up or down(maybe +-5V) aren't going to produce any fault but it is recommended that you use a 24V AC transformer.

 
ID:
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[audioguru2]

Hi Esil,
Welcome to our forum. ;D
People have made the original project and report that the max output is only about 25VDC at about 2.5A. I made a list of the circuit's voltage losses to show why.
The transformer's voltage rating is too low for the project to have a well regulated output of 30VDC at 3A. Even with a 24VAC transformer, when the load current is low then two of the opamps have a total supply voltage that is much higher than their absolute max rating of 36VDC. Therefore opamps with a higher supply voltage rating are needed anyway.

Transformer manufacturers make transformers with many different output voltages and the 30VAC that I recommend for this project is one. 

 

[sophos.pl]

Hi, can anybody help me ?

I have problem with current limiter, when I short output current limiter is works but led dont lights, when I normaly work on this power supply and i want set current limit with P2 led imediatly light and Output voltage is 0V.

sorry for my english..

 

[audioguru2]

Opamp U3 is used for current regulation. It compares the voltage across R7 (which is caused by load current) to the voltage of the current adjustment pot P2. Its pin 4 must be about -5.6V or it won't work correctly.

 

[sophos.pl]

Thanks for reply
voltage in pin 4 is ok -5.5V

problem is that when i turn P2 only little curent limiter is start and v out =0

 

[audioguru2]

voltage in pin 4 is ok -5.5V

problem is that when i turn P2 only little curent limiter is start and v out =0

Then R21 connects to the wrong end of R7.

 

[sophos.pl]

r21 is in correct place.
Short history of my problem :
When i start power supply first time everything was ok. current limiter worked etc... but when i short circuit output then q4 burned, i replace q4 with new 2n3055 and q2 with bd243. Now when i short output curent limiter  work v out = 0v but led dont light. In normal operation current limit is work "too good" when i turn P2 only little led light and v =0v

 

[audioguru2]

U3 is supposed to compare the voltage across R7 caused by the load's current, with the voltage from P2 which is from nearly nothing to 1.7V.
With P2 at max and the voltage from P2 at 1.7V then U3 does nothing until the voltage across R7 is slightly more than 1.7V which would be caused by a load current of 1.7V/0.47= 3.6A. If P2 is set to half then the load current must exceed 1.8A for U3 to begin reducing the output voltage.
Q3 conducts and turns on the LED whenever the output of U3 drops to begin reducing the output voltage.

Maybe your R7 has also burned and is now a much higher value.

 

[rufinus]

Hi everyone!

I just finished reading this threads about 0-30v power supply (both original and 5 amp mod). About 100 pages... 2 days time.. Wow


So, i desided to build it, namely the

 

[audioguru2]

Hi Rufinus,
Welcome to our forum. ;D

It must be a big transformer. Use one of the 24V/5A windings, it is probably 48V with a center-tap. Insulate the other 24V wire.

The voltage adjustment for your project will try to make the output exceed 24V and then settings higher will be full of ripple. Maybe you should add a resistor in series with the voltage adjustment pot to limit the max output voltage to a little lower than where the ripple becomes noticeable with full load.

 

[rufinus]

And here comes Audioguru!

 

[audioguru2]

Now, i remember few pages ago you posted new version of mod with 2 trimpots for V/C limiting, i guess i should use that one?

Adding both trimpots is a good idea. I forgot that the current adjustment pot will try to make a max current of 4A which is way too high.

Parts list stays the same ( 0-30V Mod parts list)?

 

[rufinus]

So far, so good!

Many thanx again. Off i go to produce PCB and collect the rest of the parts.

BTW, Eagle PCB , posted on previous pages, does not work
My Eagle Light says it was made with some faulty version of Eagle

"Load error 283... blah blah blah.."

 

[rufinus]

Went for a walk and had an idea. Surely i want to have an volt/ammeter built in.
Digital one. One way is to buy standard models such as 7021 based. I thought of making one myself. I have spare PIC16F870 which has four 10 bit A/D converters on board. And i just bougt two 2x16 LCD screens on ebay. The question is, how to make multimeter out of this. Software for conversion i can write, but how to interface 0-24 volts to 0-5 volts of PIC? Hardware is my weak point
Besides simple multimeter it is possible to output other info on screen too, such as how mant watt load is consuming, temperatures of power transistors, control of the cooling fan... Any ideas will be appreciated. In the case of success i could share a firmware for PIC here on forum. If anyone interested....