Jump to content
Electronics-Lab.com Community

0-30V Stabilized Power Supply


Recommended Posts

  • Replies 2.4k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

hi any updates to this project

Why do you show an LT1038? it is obsolete and is not made anymore. It is impossible for it to dissipate 32V x 10A= 320W. Its datasheet shows that with a huge heatsink with fan or with liquid nitr

Posted Images

I had a play with the older design at making digitally controlled, It worked very well I had a coarse and fine settings for the voltage, The coarse did 1V steps and the fine did it in MV steps, But stupid me put to much power out and blew something up on the PCB, I did not invetsigste any further has I want to build the latest version before I  start playing again, I keep reading this topic and the more you guys seem to all the have fun  ;D,  thhis makes get the urge to start playing agian but I has had to put it on the shelf due to other commitments, but now it's coming up to Christmas and christmas is the time to start playing. So I shall blow the cob webs of it and dig deep to find the code I used and get designing,  ;D
I shall design my own PCB to accpect both digital and pot's. That if the digital part does not work out i can stick pots in.

I can remember asking this in the old topic before we lost it but was based on the older version. What is the voltage coming out of U1 pin is was it about 11V or something like that ?

Another question how much of  the old documentation relates to the newer design IE. functions wise ?

Link to post
Share on other sites

The original circuit had many parts overloaded. The new version fixed the overloads by using parts with a higher power rating.
The original circuit did not meet its spec's. The new version does.
The new version fixes all the problems with the original version.

U1 has a 5.6V zener diode at its input and a voltage gain of 2. Then its output voltage is .....?

Link to post
Share on other sites
Guest Timmymna

Just finished reading this thread and I think I'm going to give it a try.

I have been looking on Farnell's site to find a suitable transformer but I'm a little confused at what specs I'm looking for.
In the latest specs it states a 28VAC 4.3A 118VA transformer, I can't see anywhere that says what the max and min should be.
A few posts back it mentions the voltage shouldn't be too high as to cause overheating and higher power losses but must also be able to provide the current required.


Your transformer is too small for a 5A power supply.
It is rated at 30V x 5A= 150VA. But the project makes 42.4V so when the output current is 5A then the transformer will be overloaded with 42.4V x 5A= 212VA.


From this comment could I use this transformer? It is 2x 30V, Secondary Winding:80VA, Secondary Current Rating:2.67A.
If I wired the two secondary's in parallel I get 30V with 160VA, giving 5.3A. If the project requires 42.4V then that still gives me 3.77A, (building the 3A version). Also taking into account peak voltage being < 44V for the opamps.

I'm not sure if this is correct or if I've taken some stuff out of context, I'm trying to understand how to select the best transformer for the job because there's also a 160VA, 2 X 25V transformer but is the 25V too low? Also it's nearly twice the price so trying to justify which is the better option.

Thanks and please feel free to point out my many mistakes  :P
Link to post
Share on other sites

As the voltage oscillates in the outlet, I can also see voltage changes in the Power Supply Output. Voltage in the outlet oscillates a lot more than I thought, about twice every minute +1 to +4V. Can't still calculate how much oscillation this creates in the PS output (single channel multimeter).

A first idea to fix this was to use a Voltage Regulator such as this: http://www.apc.com/products/category.cfm?id=12&subid=57

Or maybe you have any tip to make the PS output stable despite AC voltage changes in the outlet?

Thanks,
Effenberg

Link to post
Share on other sites

Just finished reading this thread and I think I'm going to give it a try.

I have been looking on Farnell's site to find a suitable transformer but I'm a little confused at what specs I'm looking for.
In the latest specs it states a 28VAC 4.3A 118VA transformer, I can't see anywhere that says what the max and min should be.
A few posts back it mentions the voltage shouldn't be too high as to cause overheating and higher power losses but must also be able to provide the current required.

... could I use this transformer? It is 2x 30V, Secondary Winding:80VA, Secondary Current Rating:2.67A.
If I wired the two secondary's in parallel I get 30V with 160VA, giving 5.3A. If the project requires 42.4V then that still gives me 3.77A, (building the 3A version). Also taking into account peak voltage being < 44V for the opamps.

Yes, the 160VA transforer is able to allow the output current of the project to be as high as 3.77A.

I'm not sure if this is correct or if I've taken some stuff out of context, I'm trying to understand how to select the best transformer for the job because there's also a 160VA, 2 X 25V transformer but is the 25V too low? Also it's nearly twice the price so trying to justify which is the better option.

Even the designers of this kit did not calculate the amount of voltage losses there are.
They said to use a 24V transformer but then the measured max output voltage at 3A was only about 25VDC.
In the latest version a 28VAC transformer will be fine. Your 30V one is also fine.
Link to post
Share on other sites

This is my schematic for the power supply, I've check it over but would like someone just to check it over and make sure I've not missed any  thing or any errors This will be a great help, If all correct I then shall transfer to the PCB layout tool,

I've gone for the option of C1 with R1 Across the cap mounted on the case wall and the same for the bridge rectifier, Q4,Q5,Q2,R23,R24,R16 also shall be mounted on a PCB bolted to the heatshink.

Once I know the schematic is 100% correct then I will know that the PCB will be 100%

EDIT: I've missed out D9 that is added
Thanks

Power_supply_V2.pdf

Link to post
Share on other sites

This is my schematic for the power supply

Why will ZD3 reduce the positive supply to U1 and U2 when the transformer is 30VAC? It might cause the max output voltage to be less than 30V when the current is max at 3A.

The 30V transformer might have an output of 31.5V without a load then its peak voltage is 44.5V and the rectifier bridge will make a positive unregulated supply of 43V which is less than the max allowed 44V for an MC34071 or TLE2141 opamp. 
Link to post
Share on other sites

Why will ZD3 reduce the positive supply to U1 and U2 when the transformer is 30VAC? It might cause the max output voltage to be less than 30V when the current is max at 3A.


I seen it in an earlier posting so I thoght I'd add it has you could just put wire link if not need but if it is needed and it's not here it make it look unitdy, But if it's not needed then I will take it out

I've already started to lay the PCB out for it
Link to post
Share on other sites

Hey umm does anyone that has a working supply did a voltage table for the nodes on the circuit? It would be of great help. Thanks in advance

It is a very simple circuit. Tell us which version you made and the problem you have with it and we will tell you the voltages that should be measured and what might cause your problem.

For example the output of U1 is always 11.2V. The output of U2 is about 1.7V higher than the output voltage.
Link to post
Share on other sites

I made the version that is in the page http://www.electronics-lab.com/projects/power/003/. My problem is that the LED is always 'on', and the output voltage steadily declines. The only component taht gets a bit hot is the transistor 2n2219 (Q2) after having it connected 1 minute. The circuit doesn't respond to any of the potentiometers or the trimmer. The rectified/filtered voltage is 36V DC.

Link to post
Share on other sites

I made the version that is in the page http://www.electronics-lab.com/projects/power/003/. My problem is that the LED is always 'on', and the output voltage steadily declines. The only component taht gets a bit hot is the transistor 2n2219 (Q2) after having it connected 1 minute. The circuit doesn't respond to any of the potentiometers or the trimmer. The rectified/filtered voltage is 36V DC.

Check that the -5.6V supply is actually -5.6V.

U3 is the current regulator that detects the voltage across R7 that is caused by load current and compares it to the voltage of the current-setting pot which goes from almost 0V to +1.92V. Since the (+) input of U3 connects to the current setting pot then its voltage is usually higher than the voltage across R7 so the output of U3 is high and then the LED is turned off and D9 does not reduce the output voltage. Check the pins and parts connected to U3.

The 2n2219 is much too small for this project and will over-heat if the output is set to a low voltage or is shorted with the current set high. A BD139 transistor should be used with a real heatsink.

The original project uses TL081 opmps that have an absolute max total supply of 36V. In your circuit U2 and U3 also have the -5.6V supply so their total supply is too high at 41.6V and maybe they are destroyed or maybe they will fail soon. Use MC33071 or TLE2141 opamps that are rated at 44V.
Link to post
Share on other sites

PicMaster,  How come R1 and R2 in your sketch  have signifcantly different values than the revised parts list?


Sorry that's my fault I missed those 2 values I can see that they should be 2K2 and 82R, Thanks for pointing that out, I will recheck the rest of the values,

I presume that everything else is ok ?
PCB is about 80% laid out and routed I will post as soon has it is done.

Thanks
Link to post
Share on other sites

Have any chance to make the RedWire circuit mod work with 30A?
Maybe change only the transformer (30Vx30A) and the retify diodes, number of power transistors and wire diameter?
I suggest Redwire to put in the beginning of the topic the most recent files so that we don't need to seek for the whole topic that today is with 18 pages. Please include the Eagles files too (.sch and .brd)

Link to post
Share on other sites

To get a 30A output then the output transistors must dissipate a total of 1,188W at times.
Liquid nitrogen will be needed to cool them.

The driver transistors also must be many. Opamp U2cannot drive many driver transistors so a pre-driver transistor or a few of them and a pre-pre-driver transistor must be used. Then the max output voltage will be reduced.

If you are a good circuit designer you could use a switching pre-regulator to reduce the heat.

Link to post
Share on other sites

bugmenot,          I have been meaning to do that for a while and I strongly agree it would be more helpful than searching through 20 pages.  When I first posted, I had some info on my computer at work, some at home and some I had to gather from other posters since the site crashed.      I'll try to round up the parts and put them in a zip file.  A continuing  problem is that my Eagle file is double sided and a pain to make at home. 

Link to post
Share on other sites
  • admin featured and pinned this topic

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
  • Create New...