Electronics > Projects, Designs, and Technical Stuff
Bench CC/CV PSU Based on Daves uSupply (Not Anymore)
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KC0PPH:

--- Quote from: Edd on March 27, 2019, 02:58:35 pm ---KCOPPH . . . . .
Not so much that you made the PCB smaller . . .but MORE importantly was that you made that schematic of

=https://www.eevblog.com/forum/projects/bench-cccv-psu-based-on-daves-usupply/?action=dlattach;attach=688722;image

Smaller . . . so much that the alpha numerics aspects  are now too small to reliably be able to read.

You were so image density stingy /limiting, that your whole schematic page came out as ~ 805 X 621 pixels.
Best that you doubled  . . 2X'd that size . . . to then be fully  readable.

73's de Edd

I KNOW the speed of light  . . . .So, what is the speed of dark?

--- End quote ---

Correct, the PNG is not a high res version.

I will make it full screen before i do a capture again and see if that fixes it.
KC0PPH:

--- Quote from: Kleinstein on March 27, 2019, 05:04:21 pm ---With no variable load, there is no need for an extra buffer of the reference. So one could use 4 OPs as.
1 x CC mode regulator
2 x CV mode regulator
1 x Current set buffer
1 x CC/CV indication  between the outputs of the first 2 OPs.

Just using the LEDs with no OP between the outputs of the OPs would give a variable intensity and would not work with voltage near the upper limit.  The CC limit can also be reached at a relatively high voltage.

The TL431 itself can do some amplification like 2.5 V to 5 V or 7 V. The LM329 would be 7 V directly. So no extra OP is needed to buffer the reference.

--- End quote ---

--- Quote from: Kleinstein on March 27, 2019, 05:04:21 pm ---With no variable load, there is no need for an extra buffer of the reference. So one could use 4 OPs as.
1 x CC mode regulator
2 x CV mode regulator
1 x Current set buffer
1 x CC/CV indication  between the outputs of the first 2 OPs.

Just using the LEDs with no OP between the outputs of the OPs would give a variable intensity and would not work with voltage near the upper limit.  The CC limit can also be reached at a relatively high voltage.

The TL431 itself can do some amplification like 2.5 V to 5 V or 7 V. The LM329 would be 7 V directly. So no extra OP is needed to buffer the reference.

--- End quote ---

I am starting to agree with you on the not buffering of the VREF.

First I dont like the idea of introducing additional temp-co's to the ref- I am sure a lot will disagree with me here.
Second the VREF is only tied to the 2 Pots. The total resistance is 25K for one and 50K for the other.
Through the 25K Pot I get a current of 0.1mA and through the 50K pot I get a current of .05mA
This is well within spec for the Voltage Reference. (There is also the SET voltage divider with 0.5mA.

On the final design I will have a single high end VREF that will most likely be buffered due to how much will be using it (Still need to determine for sure). This makes less "Rework" for this design as the VREF buffer does not need to be removed.

not1xor1:

--- Quote from: imo on March 27, 2019, 06:18:09 am ---My simulation also shows the not1xor1's blinking works, there is a region where the both may lit (Iout pretty close to the SlowCC limit) but that situation is rather rare.

--- End quote ---

Really??? I've just checked my simulation (with unmatched LEDs/diodes) and while the current limit appears to be 1.9989A, if I set the constant current load to 1.999A only the CC LED is on, if I set it to 1.9988A the CV LED current drops from 2.1247mA to 2.1059mA, while the CC LED current stays at 2.1039pA.

If both LED are on then the problem would not be a LED one, but that the PSU is in an undetermined state (a Schrödinger PSU  ;D) with both CC and CV opamps active or in an unregulated state where the input voltage is too low for the programmed output voltage and current.
not1xor1:

--- Quote from: KC0PPH on March 27, 2019, 04:46:16 pm ---
--- Quote from: imo on March 27, 2019, 06:18:09 am ---My simulation also shows the not1xor1's blinking works, there is a region where the both may lit (Iout pretty close to the SlowCC limit) but that situation is rather rare.

I checked my wiring and it was wrong on the breadboard. I did notice the issue at low voltage (around 400mV) that the LED's did not light up. But I dont plan on really using it that low.

--- End quote ---

--- End quote ---

I can't see how it can't work even at low voltages. It does down to about 9mV in simulations, and should go below that if you manage to to drive it in CC mode at those low voltages (your load should be less than a few mΩ inicluded contact and wire resistances).

BTW please correct your quoting.
Please make use of the quote tag (it is next to the # icon in the toolbar).
not1xor1:

--- Quote from: Kleinstein on March 27, 2019, 05:04:21 pm ---Just using the LEDs with no OP between the outputs of the OPs would give a variable intensity and would not work with voltage near the upper limit.  The CC limit can also be reached at a relatively high voltage.

The TL431 itself can do some amplification like 2.5 V to 5 V or 7 V. The LM329 would be 7 V directly. So no extra OP is needed to buffer the reference.

--- End quote ---

It looks like you haven't grasped the working of the circuit. The current through the LED is roughly constant in any situation.
And yes both LEDs are on if the input voltage is too low, but that is not a bug  ;D, but rather a feature as that would clearly point to an under-voltage problem
If you drive the LEDs through an opamp comparator, in case of input under-voltage, just one of them, randomly depending on the offset voltage, would be on.
I just can't see any advantage in that.  :-//
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