Electronics > Projects, Designs, and Technical Stuff

Bench CC/CV PSU Based on Daves uSupply (Not Anymore)

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Kleinstein:
Against turn on / turn off transients it might be a good idea to have something like a 12 V zener in series with R2. So the current source is off when the supply is too low or not yet low enough for the OP to work.

iMo:
 :phew: Again a small issue in my schematics - I grounded the 2200uF cap into the ground instead to the -1.3V..
I've replaced the picture in my above post. The switching off looks ok with "2 diodes" negative supply..
Better, you may doublecheck..

PS: below a more realistic scenario - switching on/off (200ms on, 4sec off) the AC before the diode bridge, "2diodes" negative supply.

KC0PPH:
Just wanted to give an update. I have been busy with work and school, and so this took a back seat.

I had my first board populated, and had issues trying to get it to actually regulate. It tuns out the resistor that limits current into the OpAmp Outputs for Voltage or Current Control was 51.1K not 51.1 Ohm... So that explains why I could not get it to regulate.

I gave that one to my father, and am in the process of populating another one. I have been doing it slowly and powering it up to keep an eye on things. So far it is looking like it will work, the problem I have is missing parts. I only ordered 1 TL431 thinking I had a handful. What I do have is 4040's. With that I will be waiting on the postman again.

One question for everyone though.

In the attached picture I am trying to figure out why that LED does not stay lit. It only turns on when I short out the Collector of that transistor to ground (through a 51 Ohm Resistor). I thought this was wrong and did it up on the proto board with same results???

I have also been racking my brain trying to figure out the Fast CC calculation. I have .15 ohm as the shunt resistor and need to figure out how to do that math? Could anyone give me a starting place so I can calculate the fast CC based on my requirements?

Once again Thanks in Advance!

iMo:
The LED does not lit because of a wiring issue (doublecheck the transistor type and its wiring).
The current through the LED should be 4-5mA when the collector is sourcing the current.
When the collector is floating the I_LED is around 0.5mA.
With shorted collector to gnd the I_LED is around 5mA.

The Fast CC calculation (aprox):

I_fcc_limit = 0.6V / Rsense = 0.6 / 0.15 = aprox 4A

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