Hi, i need precision current limiter for LM337 with TL431, as there is non existing negative version of TL431 is there alternative simple device that works in POS and NEG version of regulator?
I have here on simulation working LM317+TL431 as 250mA current precision limiter but for LM337 i can't get it working because it needs negative version of TL431.
Any suggestions of simple current limiter for LM3x7 voltage regulators? And yes i don't count BJT as limiter as they are not precise.
I have here on simulation working LM317+TL431 as 250mA current precision limiter but for LM337 i can't get it working because it needs negative version of TL431.
Any suggestions of simple current limiter for LM3x7 voltage regulators? And yes i don't count BJT as limiter as they are not precise.
There are current sensing chips available that will only require mV drops across a sense resistor that might be a better fit for what you want to do.
The ACS712 chip might be the one you want. Ali Express or ebay have modules built around the chip, look for 5A full scale, output is 185mV/A.
I have used one myself, for overcurrent protection.
I have used one myself, for overcurrent protection.
The INA199 from Texas Instruments (here's the datasheet) is cheap and easy to use. So is the ZXCT181Q from Diodes Inc. (another datasheet)
It is correct orientation, but it will not work as TL431 output positive voltage on ADJ pin of LM337 and LM337 needs negative voltage on ADJ pin to work correctly.
If you connect to ADJ pin battery that minus pole go to ADJ pin of LM337 then you will get -24,01VDC at output and it is working.
But there is no TL431 that gives negative output voltage. To shame for manufacturer that does not make TL431 in pos and neg output voltage.
That's problem.
If we use TL431 then we will have only two components with precision current limiting.
This way current limiting goes when Ilimit=2,5V / 10R = 250mA.
But as there is non existing version of TL431 it can't be done.
One idea is to convert positive output voltage from TL431 to negative that goes to LM337. This way it should work.
if you could move the current sensing R5 and U2 TL431 from the GND side to the negative input side, then mirror the TL431 current to the ADJ pin of the LM337, would it work?
Here is your suggestion it is working as negative output this way but it is NOT working as Current Limiter, i put 2R load resistor to simulate short at output of regulator and on POS regulator i got current limitting and output is 222mV and on NEG side we need -222mV but we got FULL voltage swing, so there is no current limiting on NEG side of regulator and preamp will be burned.
This is why TL431 have no one idea how to fix this because we don't have TL431 as negative version...
If you have any other ideas please write.
First image is Working -24VDC out with TL431, and second image top is current limiting voltage output on POS side and on NEG side.
POS and NEG side needs to get about 222mW and -222mW when current limiting is on schematic, but as you can see NEG version does not work.
This is why TL431 have no one idea how to fix this because we don't have TL431 as negative version...
If you have any other ideas please write.
First image is Working -24VDC out with TL431, and second image top is current limiting voltage output on POS side and on NEG side.
POS and NEG side needs to get about 222mW and -222mW when current limiting is on schematic, but as you can see NEG version does not work.
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In second image LM317 with TLVH431 (1,25Vref) with Rshunt R11 5R6 will start current limiting @225mA
Rshunt (R11) also provide necessary voltage drop for LM317 to work properly also in CCM below Vout 1,25VDC or even @OUT dead-short=Vout=0VDC
Better solution in first image is adding PNP BJT/P-Mosfet activator (+some passive) which will channel the R2 (2K18) current.
In third image With LM337+"431 additional PNP BJT/P-Mosfet activator (+some passive) will do the work,
but we need extra voltage drop (Rdrop) for addit. 1,25VDC voltage drop for running properly CCM below Vout 1,25VDC
In second image LM317 with TLVH431 (1,25Vref) with Rshunt R11 5R6 will start current limiting @225mA
Rshunt (R11) also provide necessary voltage drop for LM317 to work properly also in CCM below Vout 1,25VDC or even @OUT dead-short=Vout=0VDC
Better solution in first image is adding PNP BJT/P-Mosfet activator (+some passive) which will channel the R2 (2K18) current.
In third image With LM337+"431 additional PNP BJT/P-Mosfet activator (+some passive) will do the work,
but we need extra voltage drop (Rdrop) for addit. 1,25VDC voltage drop for running properly CCM below Vout 1,25VDC
Can the inputs to the regulators be isolated?
Then use two positive regulator circuits, joining the outputs for +/0/-.
On the second circuit, the TLVH431 has to be in the ground rail for it to work how you intended.
This is not how I would implement current limiting.
Then use two positive regulator circuits, joining the outputs for +/0/-.
On the second circuit, the TLVH431 has to be in the ground rail for it to work how you intended.
This is not how I would implement current limiting.
Johnnyx could you present here your simple current limiting circuit for LM337 and LM317?
It needs to limit curent at 250mA.
It needs to limit curent at 250mA.
My circuit was for an overcurrent trip, the current-sensing module's output going to a comparator, not what you want at all.
I don't know what you have that you can use, or what it's for.
My Friend, now deceased, got me into using cheap Chinese modules, often they are cheaper than buying the parts. Search for the function you want, and a seller appears.
Occasionally you find a dud, but some are great.
I gave up on building power supplies, I just buy them instead. I have a good TTI Lab Supply with current limiting that serves me well.
I don't know what you have that you can use, or what it's for.
My Friend, now deceased, got me into using cheap Chinese modules, often they are cheaper than buying the parts. Search for the function you want, and a seller appears.
Occasionally you find a dud, but some are great.
I gave up on building power supplies, I just buy them instead. I have a good TTI Lab Supply with current limiting that serves me well.
Hi, a current mirror would be needed in my suggested solution, something like what is in the attached picture, a current mirror made with a dual PNP transistor.
You can't source the TL431 cathode current to the LM337 ADJ node, but you can probably mirror that current to it - with a current mirror.
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exactly. But I'd leave that part to @ronovar as it has to do with how much current R7 and R8 will be sinking and the TL431 cathode current will have to swamp it. Perhaps 10mA? I don't have it in simulation.
Something like this:
Decoupling omitted for schematic transparency
CCM
LOAD is almost dead-short, Iout_max 211mA, T1 channels current Iprog 1,24/120R=10,5mA from GND, current on Rshunt=>222mA_max
The current limiter works (1,25Vref/5R6= cca 220mA, PSU for PREamps...) down to 0,0VDC Vout with dead-short with that additional Rdrop!
Below is image of limit status, "431 is on the age to conduct!
Vout=24VDC/211mA with no current limiting,
CVM.
Vshunt almost 1,24V
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