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Battery Powered Power Supply

BobK

Jan 5, 2010
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A battery is a power supply.

Your schematic is unreadable. How about telling us what you are trying to do?

Bob
 

CDRIVE

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May 8, 2012
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Why does this circuit look familiar? Maybe it's just all the white space or is it the RJ45 connector?

Chris
 

gregfox

Mar 25, 2013
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Hi CDRIVE, I got it from the EEV blog, and propose some mods... like
Low voltage turn off/Warning, 10V output, Push Button ON/OFF etc.
 

CDRIVE

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I think you're going to have to eliminate as much white space as you can. It's too difficult to analyze a schematic that has to be scrolled. ;)

Chris
 

(*steve*)

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It looks like you've simplified Dave Jones' design to the bare bones
 

KrisBlueNZ

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It would also be helpful to see the original design. A link to the schematic would be enough.
Dave Jones is a lot more knowledgeable than me, and most of the members of this forum. I trust his designs and I would only be interested in the differences between your design and his.
 

gregfox

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Hi, The Lab power supply was presented at EEVblog #224 - Lab Power Supply Design - Part 1, Part 2 and Part 3 A link is below


He went much further on with this power supply, adding a micro and LCD display etc. but I just need the basics, although it would be nice to have the whole design, but my c coding is poor to say the least, so the basics is just fine.

My dream list is as follows:
Battery powered by (4) 3.7V 2500mAH 18650 cells.
Constant current and constant voltage
Variable from “0” to 10-12V output.
Variable current limit max 1AMP
Separate meter for current and voltage
Indicator when current limit reached
Automatic Battery low level cutoff (So as not to damage the Li-Po batteries)

I'm trying to reduce the Schematic, and will post when done.

Thanks all
 

gregfox

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Can this be read?

Please let me know, if you can read this...
Thanks
 

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gregfox

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Read this?

Might be easer to read.
 

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gregfox

Mar 25, 2013
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better?

I Think this may be a better schematic.
 

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KrisBlueNZ

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That schematic is OK. You could make it more readable by reducing the number of right-angles - instead of zig-zagging, try to keep everything direct.

Do you have the schematic of Dave Jones's design for comparison?
Is there a circuit description in text form?
I looked on eevblog.com but it just has the videos.
 

CDRIVE

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I guess my eyes don't make a good benchmark for schematic readability. My eyes are old and tired. Both of those prints look washed out to me. I find the contrast awful. I can barely read the text in the schematic and that's after I've magnified it. After magnifying it I'm back to scrolling it. What CAD - Spice software are you using? Whatever it is it's not eye friendly.

Chris
 

gregfox

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I'm using Eagle software and exporting it. I'll try some other way to export...

Try this and please let me know how it is.
 

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gregfox

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Org Circuit

This is the original I got from the video...
 

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(*steve*)

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OK, I'm going to repeat a question I asked on the eevblog forums which was never answered...

With the low pass filter on the control input of the LT3080, surely the transient response to changes in load (when the power supply is operating in constant current mode) is going to be poor.

edit: the time constant can;t be better than 22ms by my calculations. If you assume you need between 4 and 5 time constants, then you're looking at around 0.1 seconds. That's a long time if someone accidentally shorts your power supply.
 
Last edited:

KrisBlueNZ

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Yes, Steve, I was thinking that as well.
I would prefer a design where voltage and current were both controlled by linearly varying the control voltage.
 

(*steve*)

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If you follow Dave's videos on this, he adds that filtering to remove noise on the output.

This is fine for when the device is regulating voltage since you want a constant voltage and limiting the rate at which it can change is not an issue.

I do note that he seems to have this project on the back burner for now.

I would perhaps have an alternate arrangement which allows a smaller capacitor and a lower resistance for discharging it in the current limit path.
 
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