0-18V Pos/Neg 1A Current Limited

[liquibyte]

I have come up with what seems a fairly decent power supply using a minimal of parts that are easily obtainable and cheap.  The idea is to have a power supply for working with dual supply op amps.  The schematic in the picture differs from the LTSpiceIV simulation file for clarity.  I've got this sitting on a breadboard and it works but I've only loaded it down to 200mA so far due to my not having had boards made yet and the transistors not being on heatsinks.  Once I've got this completed I'll put up a BOM with everything I've used including the case, meters, heatsinks etc.

Updated to reflect reality.  I'm probably going to just put in analog meters for this project.



View attachment 0-18V-Independently-Variable.zip

 

[liquibyte]

I hate this new forum software. I just did an edit and it lost its mind. I had forgotten to add that you will have to install http://ltwiki.org/files/LtSpiceIV_Plus_12_2009.exe for the extra parts I used. I'm not sure if the OP07 comes with LTSpiceIV by default or not but I do know the bridge rectifier I used doesn't. If you don't want to install them, just replace the rectifier with 4 diodes. I usually use the MUR460's.

 

[admin2]

What problem did you experience while editing the post?

 

[liquibyte]

I hit the submit button and I was taken back to the post but it was if I hadn't done anything in the first place, no changes.

 

[admin2]

It seems like a JavaScript issue. What brower/operating system are you using?

 

[liquibyte]

Then I'd have to say that the software switch was a bad idea. It shouldn't take javascript to post, ever. I have it blocked by default on most sites unless I whitelist it and I hadn't done that yet here because things changed and I'm personally wary of things changing just for the sake of change. I think that this is probably going to have me going back to anonymous lurker status. To be honest, there's not much in relevant content here anymore and I don't see it being brought back to life any time soon without new content. It's one of the reasons I came up with this supply but since the software can't be used without arbitrary and unnecessary js usage, I don't think I want to bother with it anymore.

 

[audioguru2]

I cannot make an attachment here with this new software when I had Windows 8.1 and Internet Explorer 11 and now I also cannot on Windows 10 and Edge or with Internet Explorer 11 even when I activated the latest JavaScript that I never needed to use on any other site.

Maybe this new software works only from a Macintosh operating system? 

 

[liquibyte]

Maybe this new software works only from a Macintosh operating system? 

I don't know about function but it certainly seems like it's trying to look like it.  I get why he wants everything integrated and looking the same but I despise the web 2.0 look.  The first person to do this was doing something unique, everyone else, not so much.

 

[CBETO3AP]

Hello liquibyte
I propose a small change that would improve the stability under variable load.



Svetozar

 

[audioguru2]

C11 and C12 slow down the outputs too much, causing poor voltage regulation if the load current changes of if the load current is modulated. The circuit will have serious overshoots and might oscillate.

 

[liquibyte]

You guys are late to the conversation.  I've had the boards made and from my testing things work rather nicely.  I did make a mistake on the gerbers and forgot to connect D2 to R2 but since it was a short hop, I left the lead on the zener long, folded it over and soldered it to the lead of the resistor on the bottom.

I have no way to vary the current dynamically and I'd not imagine anyone doing that so I'd say, all in all, things work as expected with no oscillation at all.  I've got less than 20mV ripple at full load on the output.  For what I designed this for, I'd say it works nicely.

 

[CBETO3AP]

I am glad you are happy with what has been achieved. I did not mean to criticize, simply insignificant change without complicating the circuit can eliminate the fall of 0.62v when consumption is 1A. The audioguru also right, C11 and C12 better be around 0.XXXuF.

Without wishing to disturb: Svetozar

 

[liquibyte]

I am glad you are happy with what has been achieved. I did not mean to criticize, simply insignificant change without complicating the circuit can eliminate the fall of 0.62v when consumption is 1A. The audioguru also right, C11 and C12 better be around 0.XXXuF.

Without wishing to disturb: Svetozar

Your change adds significant oscillations to my simulation output on the positive side of things.

C11 and C12 slow down the outputs too much, causing poor voltage regulation if the load current changes of if the load current is modulated. The circuit will have serious overshoots and might oscillate.

As for the 2.2u cap, it could have just as well been 1uF but 2.2uF is what I had on hand that solved the issue I was working on also in regards to oscillations.  I got the value from doing some research into problems I was having and this was a recommended solution and, no offence, it worked.  I'd link what I was reading but I can't find it again.  Suffice to say that it was from a reputable source and not instructables or the like.  I think it was actually an ap note and I'll link it if I find it.

The bottom line is that while math and theory can go a long way, up until you build something you never know what you're going to get.  Oh, and always run board checks.  The missing trace was a dumb mistake on my part.  The pic of the board shows the fix I had to do.

This is a redesign of something I found online and wanted to see if I could simulate it an manipulate it to do what I wanted.  My changes worked so well that I wanted to put it on a manufactured board so I did.

 

[CBETO3AP]

Your change adds significant oscillations to my simulation output on the positive side of things.

 

C11 and C12 slow down the outputs too much, causing poor voltage regulation if the load current changes of if the load current is modulated. The circuit will have serious overshoots and might oscillate.

If you like to experiment try This

"I have come up with what seems a fairly decent power supply using a minimal of parts that are easily obtainable and cheap.  The idea is to have a power supply for working with dual supply op amps."

A very basic and stable example. The op-amp burn equal to 1A or 5A.

Very good work

 

[audioguru2]

The two series diodes at the outputs of the regulators RUINS their excellent voltage regulation. Why two diodes, why not just one diode, it will also ruin the voltage regulation but not as much as two diodes?

The sliders on your 5k pots are shown disconnected.

The 240 ohm resistors are for the more expensive LM138 and LM137. LM338 AND LM337 need 120 ohms (and the pot value also halved) to prevent the output voltages from rising if the load current is low.

 

[CBETO3AP]

Hihi because I'm lazy. I just grab the first Internet scheme as an example. I do not know who and why has put diodes. The potentiometer is understood. And of course, LM317, LM337 are more appropriate. It's just as basic example.

 

[liquibyte]

The fact that you even suggested that circuit tells me that you either know nothing and are trying to fake it or that what you think you know is entirely wrong.  Linear regulators as a lab supply is just stupid and I'm tired of seeing that dumbass circuit all over the net being suggested as so.

 

[CBETO3AP]

If I'm wrong about something (of course this can be and prefer to see in the community), there is audioguru, who always find the error and tell, and always right, which I respect a lot. This is already on frame of contecst so I would like to haver not said anything about your "work of art". Practically not get anything more than what can be done with the LM317, LM337. In fact you've gotten worse stability, thereby constructively we have discussed before. I will not bother to draw a circuit totally different from yours, it's easier to grab any circulating on the internet and we would have the same result as minimum. Everything I've said has been with good intentions, so far. I am sorry that you've had that bad.

 

[liquibyte]

In fact you've gotten worse stability, thereby constructively we have discussed before.

Really, 20mV p/p is worse stability?  I've got a nice scope trace I'd like you to look at then.