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| Bench CC/CV PSU Based on Daves uSupply (Not Anymore) |
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| jaycee:
You could always put two 2016 packages in parallel and have a 0.05 ohm shunt.. then adjust the gain of the sense amp, if dissipation is an issue. There's also plenty of real shunt resistors out there which are not all that expensive. I chose the LT1006 simply because it was the first single supply opamp I came across in LTSPICE. Im sure a great many parts would work I've now simulated it and it does work fairly well. I'll post the LTSPICE file in a bit. |
| Kleinstein:
The simulation has no problem with the difference amplifier, but in real world the common mode rejection is not that good unless very accurate resistors are used. So the tendency is to use a higher value shunt to start with a little higher voltage at the shunt. This also helps when a small current limit is set. I know the problem of heating of the shunt. The resistor is a compromise between self heating and demand on the amplifier. For a simple circuit I wold prefer a high value and higher power resistor, e.g. vitrohm KH206 or KH208 (4/6 W cemented wire wound). A larger resistor needs less speed from the amplifier and thus makes the CC regulation easier. |
| KC0PPH:
Let me pull my horns in for a bit and breadboard up that circuit and see what I get. I have some general Op Amps (LM324 I think) I might be shy on Cap values but should be good on resistors. Thanks for the advice and I will update with how the circuit performs. |
| jaycee:
Have a play around with this in LTSPICE :) LM324 might work actually. I couldn't get LTSPICE to behave with the TLE2021 model... convergence problems edit: Added an image for those who are LTSPICE impaired :) |
| KC0PPH:
I got it in LTSPICE and have been playing around with it. In playing with the Voltage Divider for V-SENSE I am a bit confused why the 3 resistors and the capacitor C6 vs just 2 resistors. |
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