Electronics > Projects, Designs, and Technical Stuff
Bench CC/CV PSU Based on Daves uSupply (Not Anymore)
iMo:
BTW - this one
https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg2275563/#msg2275563
has some advantage over the one we mess with here - you can set for example 80V output with 12V opamp's Vcc :)
You can set the Vout and I_Limit with DACs as well.
jaycee:
--- Quote from: imo on March 17, 2019, 05:05:57 pm ---BTW - this one
https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg2275563/#msg2275563
has some advantage over the one we mess with here - you can set for example 80V output with 12V opamp's Vcc :)
You can set the Vout and I_Limit with DACs as well.
--- End quote ---
The output stage has gain in that version?
In my own design, Im using separate transformer taps to create a +5/-5 supply biased around the output
KC0PPH:
I am going to continue testing the circuit you guys have worked up in this thread and see where it goes. I am pretty new with this stuff and decided to take a different approach while I am waiting on caps to arrive.
Using the latest version from iMo I have implemented the 4mA CC drive and the TIP120.
Rather than using OpAmps I am using a 5K pot. I need to do some further testing and see whats going on, but at the output of my TIP120 I can only get 3V3 with a 5V input. I was thinking I should only get .7V drop?
Also as I increase the Vout the LED begins to Dimm and eventually turns off. I have not investigated this, however I dont think that should be happening. I am wondering if I am overloading my AD2 which I am using to power this.
BTW the Emitter of the TIP120 is connected to a 100 ohm resistor to ground.
iMo:
The stuff works such the 4ma current source produces a constant current which flows from the CCS's collector "somewhere".
Without the opamps wired the whole CCS current flows into the TIP120 base and the output voltage shall be at its Max.
You have to "redirect/steal/sink" the CCS current by pulling it off the TIP's base in order to decrease the voltage at the output.
Kleinstein:
A darlington transistor has about 1.5 V drop, as there are 2 BE junctions. So I would expect a little more than 3.3 V, but not much. With load current there is additional drop at the shunt. The circuit shown here is never made to work with a low drop - more like good enough to get 12 V out from a 18 V source (e.g. laptop supply). The other points are keeping the circuit simple and cheap and use a high side shunt, so that it could be used in combination with an LM317 / LM7805 or similar regulator from the same raw source.
Just using a pot to set the base voltage would be only a very crude voltage adjustment. So this would be a much simpler circuit and the test on this circuit would not tell much about the final circuit.
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