General > General Technical Chat
LED Lighting (350 mA). Is there any standard for # of LEDs is a string?
T3sl4co1l:
Try a resistor from Rshunt to REF, and a C or R+C from REF to A.
Tim
Benta:
--- Quote from: T3sl4co1l on August 10, 2022, 10:31:42 pm ---Try a resistor from Rshunt to REF, and a C or R+C from REF to A.
Tim
--- End quote ---
Sorry, but throwing capacitors at the problem does not help (I already tried all that in all permutations).
I suggest you read the following (scroll down to "Advanced Amplifier Topics and Design Examples"):
https://www.sciencedirect.com/topics/engineering/emitter-follower
T3sl4co1l:
No not the emitter follower, the TLV431.
Follower stability is just, add base resistance.
Tim
Benta:
Seems you're in stenographic/shorthand mode today. Not really intelligible.
Perhaps tomorrow.
T3sl4co1l:
I mean if you want to discuss, you're welcome to, but... ???
--- Quote from: Benta on August 10, 2022, 10:18:32 pm ---but add in a TLV431 which has a lot of gain, and it gets very hairy.
The TLV431/BD679 combination proved impossible to tame, which made me go back to the BD437 plus a relatively large base resistor. This is stable and works reliably.
--- End quote ---
--- Quote from: T3sl4co1l on August 10, 2022, 10:31:42 pm ---Try a resistor from Rshunt to REF, and a C or R+C from REF to A.
--- End quote ---
You already discovered the base resistor, that's fine.
You seemed to indicate reducing TLV431 gain might be helpful...
...That's the way to do it.
It's not clear if your "impossible" search included such. So it's worth mentioning.
Perhaps a diagram is missing; I take words for granted much too often.
This for example stabilizes a '431 into a C load:
You already have the R3, more or less. R2 is missing. C1 can be R+C for additional phase margin.
Some damping (R+C) at the output (C-E or C-GND) can also help, when the load is squirrelly. LEDs wouldn't usually be long enough I think, but a high fT transistor might be able to anyway.
I could further describe how to solve for such values, but I'm guessing that isn't necessary here.
Not sure how much more detail to add. Emitter ferrite bead?
Tim
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version