Author Topic: DIY bench power supply  (Read 16628 times)

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Offline FermínTopic starter

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DIY bench power supply
« on: April 15, 2015, 02:05:25 am »
 Hi, I've decided I'm going to build my own bench power supply based on Mjlorton's design.
 As I don't have rail to rail opamps and I want to reach 0V at the output I think (correct me if I'm wrong) I need a negative rail, but I don't need a symmetric power supply i just want something like -10Vcc with a small amount of current so I don want to use a center tap transformer.
 I've been thinking about using tho different transformers, a big one (with the necessary voltaje and current regarding the specs of my power supply) and a small one (with just the necessary voltaje and current to gibe the opamp a negative rail). Or in a more efficient way, one with different windings.
 
I came up with the attached design. I want to know if it is correct or if is there any other (more efficient) way to do it.

Thank you.  :-+
 

Offline ivan747

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Re: DIY bench power supply
« Reply #1 on: April 15, 2015, 02:44:41 am »
There is a more efficient way to do it. Here is an example of a power supply that does it. It does it using a capacitive charge pump, similar to a capacitive voltage inverter. I frankly can't remember its name.
 

Offline FermínTopic starter

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Re: DIY bench power supply
« Reply #2 on: April 15, 2015, 02:54:09 am »
There is a more efficient way to do it. Here is an example of a power supply that does it. It does it using a capacitive charge pump, similar to a capacitive voltage inverter. I frankly can't remember its name.

thank you.
I'd prefer a linear power supply because of the noise. Is there any problem with my design, would it work? I have no idea  :-BROKE
 

Offline rs20

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Re: DIY bench power supply
« Reply #3 on: April 15, 2015, 03:11:57 am »
thank you.
I'd prefer a linear power supply because of the noise. Is there any problem with my design, would it work? I have no idea  :-BROKE

?? The rectified output of your negative transformer supply is going to be a rectified sine wave, so you still need to filter it, and put it through a linear regulator anyway. So, if you really want a very smooth supply, just use ivan's suggestion of a charge pump, coupled to a linear regulator.
 

Offline rdl

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Re: DIY bench power supply
« Reply #4 on: April 15, 2015, 03:16:32 am »
Just go ahead and make a full dual polarity power supply. Having a usable negative rail comes in handy sometimes. The free to download chapter 9 of the Art of Electronics 3rd edition has a good schematic and great information about power supplies in general.
 

Offline FermínTopic starter

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Re: DIY bench power supply
« Reply #5 on: April 15, 2015, 03:23:43 am »
thank you very much.
 

Offline skyjumper

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Re: DIY bench power supply
« Reply #6 on: April 15, 2015, 03:43:51 am »
I need to do a similar thing, and along these lines, did Dave ever make a kit of his battery powered power supply, that he designed in a multi-part blog entry?
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #7 on: April 15, 2015, 11:12:06 am »
There is a more efficient way to do it. Here is an example of a power supply that does it. It does it using a capacitive charge pump, similar to a capacitive voltage inverter. I frankly can't remember its name.
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/

I have two things I just can't visualize in my head:

1 - U2 and U3 must draw very little current - How do C2 C3 and D5 D6 magically invent that negative rail?

2 - I don't see any trusty shunt resistor in the path from rectifier and the final series-pass 3055 (so how's that possible?)

 

Offline rs20

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Re: DIY bench power supply
« Reply #8 on: April 15, 2015, 11:36:19 am »
This video is far more relevant than it might first appear. If you understand this video properly, and then go back to the schematic you posted, it'll make sense:



Sure. the video is a doubler rather than the negative rail that you want, but just flip the diodes around the other way and you'll get your negative rail instead. And the circuit in this thread uses AC as the oscillating signal, rather than a microcontroller pin. Same principle.

If you're wondering why a doubler looks so similar to an inverter, you just have to realise that a doubler and an inverter are exactly the same thing. Think about it: you have 12V (or whatever) and 0V, and you want to generate -12V. Now, measure those voltages relative to the top rail -- the top rail is 0V, the old ground is -12V, and you want -24V. You want a voltage doubler, albeit one that operates on negative rails. Just flip those diodes around.
 

Offline Thor-Arne

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Re: DIY bench power supply
« Reply #9 on: April 15, 2015, 11:56:03 am »
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/
There's a update on this project here.

Also read the electronics-lab forum, there's a lot of comments on this design there.
 

Offline FermínTopic starter

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Re: DIY bench power supply
« Reply #10 on: April 15, 2015, 12:59:54 pm »
Thank you all for te info, I'll start reading and decide how to do it in the best way possible.  :-+
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #11 on: April 15, 2015, 01:06:58 pm »
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/
There's a update on this project here.

Also read the electronics-lab forum, there's a lot of comments on this design there.
Thanks - yeah I saw that note about pushing the TL081's over the brink at the bottom - it's good to see peer review around some of these designs - without it, some of us would be toasting-up too many IC's!
 

Offline Sbampato12

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Re: DIY bench power supply
« Reply #12 on: April 15, 2015, 01:40:55 pm »
It is important to read the forum and updates on that project because they got some corrections.
And they changed the OpAmp, because the phase reversal problem with the TL081...

I've built this circuit, looked good, but I almost never used these power supply. When I was about to use, I found the forum showing the problems, and started I project on my own.
 

Offline rdl

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Re: DIY bench power supply
« Reply #13 on: April 15, 2015, 03:40:49 pm »
I personally wouldn't waste any time on that circuit from electronics-lab.com, it's been debated and modified for years. The last time I looked there were two threads about it with thousands of posts where people have been trying to fix it. It would take days to sort through it all. I would at least start from a circuit that's known to work well.

For anyone thinking about building their own supply I'd highly recommend getting a copy of the free preview pdf of the Art of Electronics third edition. It includes chapter 9 on power supplies, which is over a hundred pages - almost a book on its own. I'm sure there are other places to get it, where you don't need to request a password, but here's the official link:

http://www.cambridge.org/us/academic/textbooks/art-electronics
 

Offline FermínTopic starter

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Re: DIY bench power supply
« Reply #14 on: April 15, 2015, 05:22:46 pm »
I've been reading and I've decided that I'll use MJlortons schematic but I'll add a capacitive charge pump  in the supply, like attached.
what do you think?
 

Online Zero999

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Re: DIY bench power supply
« Reply #15 on: April 15, 2015, 05:44:40 pm »
There is a more efficient way to do it. Here is an example of a power supply that does it. It does it using a capacitive charge pump, similar to a capacitive voltage inverter. I frankly can't remember its name.
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/

I have two things I just can't visualize in my head:

1 - U2 and U3 must draw very little current - How do C2 C3 and D5 D6 magically invent that negative rail?

2 - I don't see any trusty shunt resistor in the path from rectifier and the final series-pass 3055 (so how's that possible?)


That circuit contains many errors.
There are many threads on that site with corrections. Unfortunately the webmaster won't update the circuit on the site.
http://www.electronics-lab.com/forum/index.php?topic=7317.0
http://www.electronics-lab.com/forum/index.php?topic=39481.0
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #16 on: April 15, 2015, 06:38:45 pm »
I finally saw the shunt resistor R7 - a bit uncommon on the negative rail?...  :palm:
 

Offline DarkZero

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Re: DIY bench power supply
« Reply #17 on: April 15, 2015, 07:02:36 pm »
hello !

this is how i would generate -voltage with one transformer

also i have my own design that works pretty well, where you can see how i made charge pump with the help of a user on this forum



http://www.filedropper.com/labpowersupply020v10ma2a
« Last Edit: April 15, 2015, 07:32:51 pm by DarkZero »
 

Offline timofonic

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Re: DIY bench power supply
« Reply #18 on: April 15, 2015, 07:42:10 pm »
There is a more efficient way to do it. Here is an example of a power supply that does it. It does it using a capacitive charge pump, similar to a capacitive voltage inverter. I frankly can't remember its name.
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/

I have two things I just can't visualize in my head:

1 - U2 and U3 must draw very little current - How do C2 C3 and D5 D6 magically invent that negative rail?

2 - I don't see any trusty shunt resistor in the path from rectifier and the final series-pass 3055 (so how's that possible?)


That circuit contains many errors.
There are many threads on that site with corrections. Unfortunately the webmaster won't update the circuit on the site.
http://www.electronics-lab.com/forum/index.php?topic=7317.0
http://www.electronics-lab.com/forum/index.php?topic=39481.0

There are a zillion "forks" of it, that made me to doubt about what one to do.

There's a Dutch design in another forum thread and it seems to be a good one.

Any EE expert to make a forum post collection of DIY power supplies with an extensive and pedagogical review? It would be awesome!
 

Offline mstck

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Re: DIY bench power supply
« Reply #19 on: April 16, 2015, 12:25:42 am »
I personally wouldn't waste any time on that circuit from electronics-lab.com, it's been debated and modified for years. The last time I looked there were two threads about it with thousands of posts where people have been trying to fix it. It would take days to sort through it all. I would at least start from a circuit that's known to work well.

For anyone thinking about building their own supply I'd highly recommend getting a copy of the free preview pdf of the Art of Electronics third edition. It includes chapter 9 on power supplies, which is over a hundred pages - almost a book on its own. I'm sure there are other places to get it, where you don't need to request a password, but here's the official link:

http://www.cambridge.org/us/academic/textbooks/art-electronics

I have made several attempts to download this free file, but so far I have not not received a password.  Is this something you can post here or alternately suggest another link. So far my searches on Google have drawn a blank or pointed at the link you provided.

Thanks

 

Offline BradC

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Re: DIY bench power supply
« Reply #20 on: April 16, 2015, 02:00:16 am »
I finally saw the shunt resistor R7 - a bit uncommon on the negative rail?...  :palm:

Actually, it's mostly seen in the negative rail. Very rarely implemented in the positive rail as the sensing and amplification is much easier low side.
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #21 on: April 16, 2015, 02:10:03 am »

I have made several attempts to download this free file, but so far I have not not received a password.  Is this something you can post here or alternately suggest another link. So far my searches on Google have drawn a blank or pointed at the link you provided.

Thanks

I will buy the book soon but it's been several days for me and, like you, still no password...
Today I stumbled on the sample chapter (online file deleted) see the link RDL posted at the bottom of this thread... :-+
« Last Edit: April 16, 2015, 03:56:34 pm by Cliff Matthews »
 

Offline mstck

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Re: DIY bench power supply
« Reply #22 on: April 16, 2015, 02:37:42 am »
Cliff

Thanks for the link. Appreciate your help  :-+ :-+.
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #23 on: April 16, 2015, 11:12:34 am »
Cliff

Thanks for the link. Appreciate your help  :-+ :-+.
My pleasure, but I have to bring up a question since the publisher is giving this chapter away...
Should a six-part zip of this be posted to "Electronics primers, course material and books" section?

I don't want to get hoofed from box.com (or this site!) on legalities, can anyone advise?
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #24 on: April 16, 2015, 12:35:51 pm »
Some progress: I just got my password for the free TAoE sample chapter 9 (on power supplies).
I replied, asking Fran Robinson (frobinson@cambridge.org) for permission to post it in the books section.

If we get permission, I will post a 6-part zip file for everyone there. MSTCK: did Cambridge.org give your password yet?
 

Offline rdl

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Re: DIY bench power supply
« Reply #25 on: April 16, 2015, 03:44:42 pm »
Sorry, I didn't notice this post until today. I guess you already found the file, but just in case - I got it from a link in this review:

http://www.wisewarthog.com/electronics/horowitz-hill-the-art-of-electronics-3rd-edition.html


I personally wouldn't waste any time on that circuit from electronics-lab.com, it's been debated and modified for years. The last time I looked there were two threads about it with thousands of posts where people have been trying to fix it. It would take days to sort through it all. I would at least start from a circuit that's known to work well.

For anyone thinking about building their own supply I'd highly recommend getting a copy of the free preview pdf of the Art of Electronics third edition. It includes chapter 9 on power supplies, which is over a hundred pages - almost a book on its own. I'm sure there are other places to get it, where you don't need to request a password, but here's the official link:

http://www.cambridge.org/us/academic/textbooks/art-electronics

I have made several attempts to download this free file, but so far I have not not received a password.  Is this something you can post here or alternately suggest another link. So far my searches on Google have drawn a blank or pointed at the link you provided.

Thanks
 

Offline Cliff Matthews

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Re: DIY bench power supply
« Reply #26 on: April 16, 2015, 03:53:18 pm »
Sorry, I didn't notice this post until today. I guess you already found the file, but just in case - I got it from a link in this review:

http://www.wisewarthog.com/electronics/horowitz-hill-the-art-of-electronics-3rd-edition.html

That's the site! (I cleared my cache and forgot where I got it....) Thanks  :-+

Note: To avoid any legal problems, I will remove the file. (already 20 people have downloaded it)
 

Offline mstck

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Re: DIY bench power supply
« Reply #27 on: April 16, 2015, 03:56:53 pm »
Some progress: I just got my password for the free TAoE sample chapter 9 (on power supplies).
I replied, asking Fran Robinson (frobinson@cambridge.org) for permission to post it in the books section.

If we get permission, I will post a 6-part zip file for everyone there. MSTCK: did Cambridge.org give your password yet?

Cliff, I just checked and realized that the password finally arrived.  The subsequent post by RDL and the link provided appears to answer the question surrounding the right to share the file.
 

Offline rdl

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Re: DIY bench power supply
« Reply #28 on: April 16, 2015, 08:56:05 pm »
I can't imagine why they would care if someone made the file available elsewhere since they're providing it for free. Maybe requiring a password was just to avoid excess traffic on their server or something like that.
 

Online Zero999

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Re: DIY bench power supply
« Reply #29 on: April 17, 2015, 12:51:43 pm »
1 - U2 and U3 must draw very little current - How do C2 C3 and D5 D6 magically invent that negative rail?
They form a voltage doubler to make the negative rail.
 

Offline ivan747

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Re: DIY bench power supply
« Reply #30 on: April 19, 2015, 07:22:04 pm »
The whole project around that schematic seems to be at http://electronics-lab.com/projects/power/001/
There's a update on this project here.

Also read the electronics-lab forum, there's a lot of comments on this design there.

AWESOME
Great find!
 


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