0-30V Stabilized Power Supply

[effenberg0x0]

The link for the project discussion, in the original project page, was updated to point here. This thread content beats up any FAQ IMHO.

There's a recent post in this thread in which someone posted a block diagram of this PSU. It might help newbies.

Hero et al are discussing a new 0-30V PSU in a new thread. I'm sure something interesting will come out.

 

[effenberg0x0]

Oh come on, you have to be more excited than that! :

LOL, I am, I am. Just having a bad week. Xmas is not a happy holiday for me at all.

Here we go: YEY!!!!!!!!!!!!!! A new PSU!!!!!!!!!!!!!! Thanks Santa!!!!!!!!!!!!!

 

[audioguru2]

guru can i put a cooler on U1 output?

What is a "cooler"? Is it a heatsink? Why?
U1 opamp operates with a load current of 5.6mA in the new version and dissipates only 300mW so it is just a little warm. 

other ways without using 2 power supply
for add the cooler?

I do not know what you are asking.

 

[singonn2]

sorry , i mean i hope add a fan cooler for the ps with using the voltage and current from U1 output isn't okay?or other ideas without using 2 power supply for the fan cooler, because my heat sink quite small so i add a fan cooler.

 

[audioguru2]

The U1 opamp has a max output current of about 20mA. A fan draws a lot more current.
The 11.2V from U1 can drive a power darlington transistor which will have an output of about 9.4VDC. The power darlington will get very hot and will also need a pretty big heatsink.

Or you can use an LM317HV adjustable voltage fregulator set for an output of 12V. It will also get very hot and will need a pretty big heatsink.

 

[singonn2]

thx guru.Both method need a heatsink again  :-\ now my problem also hard to get a pretty big heatsink , heatsink is also quite exp , LM317HV 12V with mA also will very hot?can i just put it circuit on a perfboard and cooling with fan cooler also?the input of LM317 can i just borrow the current from bridge rectifier ?

 

[audioguru2]

thx guru.Both method need a heatsink again  :-\ now my problem also hard to get a pretty big heatsink , heatsink is also quite exp , LM317HV 12V with mA also will very hot?can i just put it circuit on a perfboard and cooling with fan cooler also?the input of LM317 can i just borrow the current from bridge rectifier ?

hi sing,
I don't know which transformer you have.
A 28V transformer is  29.5V without a load. Then its peak voltage is 41.7V which is reduced to 40.3V by the full wave rectifier.

You need something  (an LM317HV) to reduce the 40.3V down to 12V for the fan. The voltage limiter will have 40.3V - 12V= 28.3V across it and (I don't know the current of your fan but maybe ) 0.5A so the "something" will dissipate 28.3V * 0.5A= 14.2W and will need a pretty big heatsink.

 

[DenFed]

I collected the original scheme (http://www.electronics-lab.com/projects/power/003/index.html). I have the transformer 20v - 30W. Will tell how to limit the output voltage is adjustable from 0 to 15 volts, the current from 0 to 1,5 A (no longer needed). Sorry for bad English (it's Google Translator).
P.S. Happy New Year!

 

[singonn2]

guru my transformer is 12+12V=24V ,after bridge rectifier is about 36V

actually need how much input voltage for LM317HV to gain 12V with about 0.5A and  the watt is lowest.

isn't LM317 input about 12-13V output will 12to13V also?

 

[audioguru2]

Hi Sing,
Rectify the 12VAC tap on your transformer with one diode and listen to see if the fan hums. If it hums then filter the rectified 12V to get 16V then reduce it to 12V with a resistor in series with the fan.

 

[singonn2]

thx for guide guru,

the transformer i already series for gain 24VAC isn't i can pull one more line from one of 12VAC with a diode mean half-wave rectification = about 6VAC?

the return circuit of the fan is point to the return circuit of transformer?because when i series the transformer 12V+12V the return circuit is doesn't use.

sorry guru i don understand how filter the rectified 12V to 16V use other  rectification way?

any diode also ok ? or at least 3A diode

 

[audioguru2]

thx for guide guru,

the transformer i already series for gain 24VAC isn't i can pull one more line from one of 12VAC with a diode mean half-wave rectification = about 6VAC?

the return circuit of the fan is point to the return circuit of transformer?because when i series the transformer 12V+12V the return circuit is doesn't use.

sorry guru i don understand how filter the rectified 12V to 16V use other  rectification way?

any diode also ok ? or at least 3A diode

Connect the (-) wire of the fan to one 12V wire of the transformer.
Connect the anode of a diode to the 12V tap on the transformer.
Connect the (+) wire of the fan to the cathode of the diode.

The current rating of the diode must be at least the current rating of the fan.

If the fan hums or vibrates at the mains frequency then add a filter capacitor to get smooth 16VDC and add a series resistor to reduce it to 12V for the 12V fan.

You could add a second diode to the other 12V wire of the transformer to have full-wave rectified 16VDC.

 

[singonn2]

I will try it thx guru.

 

[Biggy Boy]

Well I have decided to just mod the existing circuit board, using audioguru's part list, from post #2
I'll try that first, if it still isn't adaquite for 24 volts 2 amps, then I'll make a new board for Redwire's parts list.

Only part I could not locate at the supplier were the OPA445 op-amps.
So I'll see what I have in stock that is comparable.

I'm enjoying reading the posts!!!

Glen  

 

[audioguru2]

Well I have decided to just mod the existing circuit board, using audioguru's part list, from post #2
I'll try that first, if it still isn't adaquite for 24 volts 2 amps, then I'll make a new board for Redwire's parts list.

Only part I could not locate at the supplier were the OPA445 op-amps.
So I'll see what I have in stock that is comparable.

The version with the OPA445 high voltage opamps is an old version.
Use the latest version that uses more common MC34071 or TLE2141 opamps.

 

[Biggy Boy]

The version with the OPA445 high voltage opamps is an old version.
Use the latest version that uses more common MC34071 or TLE2141 opamps.

Ok so I can use the MC34071 or the TLE2141 as drop in replacements for the original schematic and board I built? to replace an TL081? I'll go look at the datasheets for those two op-amps.

I checked my stock of op-amps, all I have is low noise ones for making stomp boxs 18 volt max  :-\

 

[audioguru2]

The original project has many errors. Changing the opamps to MC34071 or TLE2141 opamps with a max allowed supply of 44V fixes only one problem.
The tiny poorly cooled Q2 transistor will melt!
The overloaded transformer might melt or catch on fire.
Many of the resistors get too hot.
The main filter capacitor's value is way too low.

The max allowed supply voltage for ordinary opamps including the TL081 is plus and minus 18V which is a total of 36V. The 28V transformer is 29V without a load which has a peak voltage of 39.6V and is reduced to 38.2V by the full-wave rectifier.
U2 and u3 also need a negative supply voltage which is -1.3v in the latest circuit so the opamps have a max supply of 39.5V. Their max allowed supply is 44V so they are fine.

Ordinary opamps including the TL081 need at least 4V for the negative supply so their total supply of 42.2V is much higher than their max allowed supply voltage.

 

[Biggy Boy]

The original project has many errors. Changing the opamps to MC34071 or TLE2141 opamps with a max allowed supply of 44V fixes only one problem.
The tiny poorly cooled Q2 transistor will melt!
The overloaded transformer might melt or catch on fire.
Many of the resistors get too hot.
The main filter capacitor's value is way too low.

The max allowed supply voltage for ordinary opamps including the TL081 is plus and minus 18V which is a total of 36V. The 28V transformer is 29V without a load which has a peak voltage of 39.6V and is reduced to 38.2V by the full-wave rectifier.
U2 and u3 also need a negative supply voltage which is -1.3v in the latest circuit so the opamps have a max supply of 39.5V. Their max allowed supply is 44V so they are fine.

Ordinary opamps including the TL081 need at least 4V for the negative supply so their total supply of 42.2V is much higher than their max allowed supply voltage.

I'll asume you are responding to me 
Yes thats why I'm upgrading the rest of the components on the original board as suggested by you in the second post on page one of this thread.
New resistors, transistors, larger cap, extra power transistor .33 Ohm 2watt resistor.......

This parts list here!
http://www.electronics-lab.com/forum/index.php?action=dlattach;topic=19066.0;attach=16238;image


Glen

 

[audioguru2]

Glen,
That old version of this power supply project was made years ago when OPA445 high voltage opamps were available. Its 30VAC transformer makes about 31VAC without a load and the rectified peak voltage on C1 is 42.4V. Two of the opamps also have the -5.6V supply so their total voltage is 48V which is too high for most opamps.

 

[bugmenot1]

Because When I decide make this power supply the link to the forum doesnt work, so I make the PCB for the original version. Can I only change the components and increase the pcb traces? Or I have to make a new PCB? Is there any way to use a output of 0-15V 3A (or 5A)? Best Regards to all. Thanks for help.