Hi all 😀
I'm looking for a circuit to limit the current output from a TLE2426 + BUF634A rail splitter. The 634A is rated at 250mA output, so I reckon a limit of 100mA each for the + and - rails is suitable. Accuracy isn't super important, as long as it's within 5% or so. A bit of a voltage drop (say, 1V or so) is no problem.
A real bonus would be to have LEDs that indicate when the current limiting is active.
I've looked at various efuses, but their lower current limit is too high for models that can handle 15V (e.g. the TI ones start at 400mA). I'm also not 100% sure how one would go about using this with a negative supply.
I thought of a LM317 and 337 to do the limiting, but then there's the 2.5V drop to consider. And I'm not sure how to incorporate the LED indicators here. There are low dropout regs (e.g. LT1083), but I can't find negative versions that work in the same way.
It might be simpler to do the current limiting before the TLE2426
Any ideas, good people?
I'm looking for a circuit to limit the current output from a TLE2426 + BUF634A rail splitter. The 634A is rated at 250mA output, so I reckon a limit of 100mA each for the + and - rails is suitable. Accuracy isn't super important, as long as it's within 5% or so. A bit of a voltage drop (say, 1V or so) is no problem.
A real bonus would be to have LEDs that indicate when the current limiting is active.
I've looked at various efuses, but their lower current limit is too high for models that can handle 15V (e.g. the TI ones start at 400mA). I'm also not 100% sure how one would go about using this with a negative supply.
I thought of a LM317 and 337 to do the limiting, but then there's the 2.5V drop to consider. And I'm not sure how to incorporate the LED indicators here. There are low dropout regs (e.g. LT1083), but I can't find negative versions that work in the same way.
It might be simpler to do the current limiting before the TLE2426
Any ideas, good people?
look for CC/CV regulator boards on Ebay.
https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=202605338573&_sacat=0
Set the CV higher than you are using so it has no effect.
Set CC to the required value.
https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=202605338573&_sacat=0
Set the CV higher than you are using so it has no effect.
Set CC to the required value.
Such a circuit could easily be designed by some members of this forum, including me, but I am pretty sure that it already exists somewhere on the internet: make a reallly good search, with the right terms, on specialized sites like seekic or Johnson's schematics collection and others, magazines circuits ideas (EDN, elecDesign,...) and you will find something, maybe not exactly what you are looking for but a circuit that can be adapted according to your needs.
In fact, I might already have designed such a thing myself, but I do not know where it could hide in my digital archives.
I have designed a limiter for members Vasko and AV-trouvaille on this site, but it is a latching type, not quite what you are looking for.
Keep searching, you will find something.....
In fact, I might already have designed such a thing myself, but I do not know where it could hide in my digital archives.
I have designed a limiter for members Vasko and AV-trouvaille on this site, but it is a latching type, not quite what you are looking for.
Keep searching, you will find something.....
How do you feel about using a dual gang (two section) potentiometer to adjust the current limit?
How do you feel about using an opamp, a current sense resistor, and a voltage comparator, per rail?
How do you feel about using parts only available in SMD?
How many components is too many? How complex is too complex?
How do you feel about using an opamp, a current sense resistor, and a voltage comparator, per rail?
How do you feel about using parts only available in SMD?
How many components is too many? How complex is too complex?
What is the actual problem you are trying to solve? 😕
Please describe it in detail.
You joking? 😀
Same thing.
Your goals are a tad unrealistic 🙄
Just curious, why do you think circuit would go into current limiting?
You expect regular output shorting?
Welcome to the Real World.
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I spent a couple of hours digging here on DIYAudio and elsewhere, but thank you for the suggested sites - I will dig onward 😀!
I'm happy with all of those things. SMD was a no-go for a while, but since I made a hotplate assembly is much easier. As for complexity, I don't mind complex (within reason - 50 components might be a bit much 😀)
The actual problem is that the BUF634 has a current limit that I don't want to exceed. I don't foresee short circuits being a problem, it's more for safety reasons - no need to cook the 634 in case something goes awry with a prototype. As for joking about 5%, nope. Surely a tolerance of 95 - 105mA is reasonable?
Thank you, that looks great! The splitter circuit in question is here: Virtual Ground Circuits . It's the last schematic toward the bottom of the page.
Good point. I had actually forgotten about flipping positive regulators
IF you are able to source a dual gang, ten ohm, 1 watt potentiometer ... ... (a big IF) ... ... then this circuit is reasonably simplistic. The pot is there to provide smooth infinitely variable adjustment range (instead of a finite number of discrete steps). You could of course replace it with a DP4T rotary switch and some 1% resistors, if you only wanted four different output current settings. That might actually be an option {holding your nose} if you can't find the dual gang pot in stock anywhere.
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Here is a possibility:
It handles the two polarities, and is adjustable with a single potentiometer from ~0 to 150mA or even more.
Each side has a LED indicating the limitation.
Here it is shown with P varied from 0 to 140K:
The outputs are on the collectors of Q1 Q4. The diode and current sources are the loads, to illustrate the operation.
It will drop a max of ~0.4V at 100mA output.
It handles the two polarities, and is adjustable with a single potentiometer from ~0 to 150mA or even more.
Each side has a LED indicating the limitation.
Here it is shown with P varied from 0 to 140K:
The outputs are on the collectors of Q1 Q4. The diode and current sources are the loads, to illustrate the operation.
It will drop a max of ~0.4V at 100mA output.
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Something worth considering: if the limiter(s) is to be used with a rail splitter, the primary supply will be unipolar. This means that an overload on a rail will ipso-facto also happen on the other: for example, if a short happens between V+ and GND, the V+ line will see an overcurrent, but this overcurrent will be dumped into the V- line by the rail splitter.
This means that only one limiter is required if it is placed upstream of the rail splitter.
It will of course not be possible to indicate which rail is subjected to an overload without additional means.
If two limiters are placed downstream, they will be able to function individually and indicate which rail causes the problem if they have individual LED indicators
This means that only one limiter is required if it is placed upstream of the rail splitter.
It will of course not be possible to indicate which rail is subjected to an overload without additional means.
If two limiters are placed downstream, they will be able to function individually and indicate which rail causes the problem if they have individual LED indicators
Fantastic, thank you so much everyone! This is really, really useful. Lots for me to experiment with this weekend!