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My attempt at a linear variable PS (power supply) using the LM317. Notice that at low current, the power comes from the chip, but at high current load, the power transistor kicks in to support the chip.
I had to update my EC LM317 model because the simpler one I have been using will not work with this circuit.
My simple model seems to work well. But, it has some drawbacks. First, the input pin doesn't do anything. That means circuits that require a functional input pin, like this one, would not work.
Second, the current at the Adjust Pin was not taken into account. This could lead to inaccuracies.
I tried to fix this.
I put a Current Controlled Current Source (CCCS) to draw in through the input pin the same current that is exiting the chip through the output pin. Now, current actually flows into the chip, and the PNP transistor will work. Not a perfect solution since the voltage is not taken into account, but better, I think.
And, I put a 50uA current source on the Adjust Pin. Now, the more accurate equation for an adjustable voltage regulator is used.
Vout = 1.25 × (1 + R2 / R1) + (50u × R2)
Vout = 1.25 × (1 + (63.1%×100k/22k)) + (50u×63.1%×100k) = 8V.
LM317 Series:
Adjustable Voltage Regulator: https://everycircuit.com/circuit/6138847104335872
Constant Current Source: https://everycircuit.com/circuit/5424946364547072
Adjustable Current Source: https://everycircuit.com/circuit/4902539157569536
Soft Power On: https://everycircuit.com/circuit/6070007032971264
Simple Battery Charger: https://everycircuit.com/circuit/4594156412076032
CCCV Li-ion Battery Charger: https://everycircuit.com/circuit/5336266329292800
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