What components from MultiSim to use, to set voltage input, output and adjust in this 0V to 30V LM317 regulator-based circuit - is it DC_POWER?

[GGoodwin]

I would like to respond to your latest reply, however, I don't have much time available (again) today.

I'll just attach some Multisim Live simulation results which I was not able to include in my previous reply. You can open my Multisim Live circuit, LM317 Adjustable Down To 0V Voltage Regulator, and just modify the values based on the images provided below if you want to reproduce the results.

Note that aside from the output-setting resistances, I also modified the input voltage and the load resistance. The input voltage is now raised to 35 V because the output voltage needed is now higher. The load resistance is increased to 1 kΩ because I want to focus on output voltage first. For Multisim Live Free Subscription, 1N4148 is the only diode available with real-world part number.

The screenshot below is the simulation result for maximum voltage of
Figure 12. 0-V to 30-V Regulator Circuit, §9.3.1 of LM317 3-Terminal Adjustable Regulator "Documentation"

(Multisim Live Simulation) Figure 12. 0-V to 30-V Regulator Circuit, maximum voltage

The screenshot below is the simulation result for minimum voltage of
Figure 12. 0-V to 30-V Regulator Circuit, §9.3.1 of LM317 3-Terminal Adjustable Regulator "Documentation". Note that the minimum voltage is a significant negative voltage not 0 V.

(Multisim Live Simulation) Figure 12. 0-V to 30-V Regulator Circuit, minimum voltage is negative (not 0 V)

[GGoodwin]

A deeper analysis of what may happen in real circuit follows.

If rheostat R2 is adjusted very near the bottom position (R2 < ≈120 Ω), the formula yields a negative output voltage. The calculated value will be realized only if the current from (reversed because of polarity reversal of output voltage) the load is small. If this reversed load current increase in magnitude, it can start to impede the flow of quiescent current in the voltage regulator IC (LM317). At sufficiently large magnitude of reversed load current, the voltage regulator IC (LM317) will not function properly and the formula may not hold.

[GGoodwin]

Meanwhile you can try experimenting with my Multisim Live circuit LM317 Adjustable Down To 0V Voltage Regulator by altering the values based on the listed modifications or screenshots that I provided for the two circuits described below.

Here are some improvements which I mentioned in my previous post for 0-V to 30-V

Regulator Circuit based on my Multisim Live circuit LM317 Adjustable Down To 0V Voltage Regulator:

R1              : I previously recommended 200 Ω, refine to 210 Ω or 205 Ω
R2 (adjustable) : replace with 5 kΩ
Diode           : replace with voltage reference IC such as LM313, LM385-1.2, or other suitable voltage reference IC

Here are the simulation results using Multisim Live, note that aside from the output-setting resistances above, I also modified the input voltage and the load resistance. The input voltage is now raised to 35 V because the output voltage needed is now higher. The load resistance is increased to 1 kΩ because I want to focus on output voltage first.

LM317 0-V to 30-V Regulator minimum voltage is close to 0 V.

LM317 0-V to 30-V Regulator maximum voltage is close to 30 V.

You can also use that same Multisim Live circuit LM317 Adjustable Down To 0V Voltage Regulator for the 0-V to 20-V Regulator Circuit that you need. Here are the modifications needed:

R1              : replace with 154 Ω, 158 Ω, or 150 Ω
R2 (adjustable) : replace with 2.5 kΩ
Diode           : replace with voltage reference IC such as LM313, LM385-1.2, or other suitable voltage reference IC

Here are the simulation results using Multisim Live, note that aside from the output-setting resistances above, I also modified the input voltage and the load resistance. The input voltage is now changed to 24 V and the load resistance is at 1 kΩ because I want to focus on output voltage first.

LM317 0-V to 20-V Regulator minimum voltage is close to 0 V.

LM317 0-V to 20-V Regulator maximum voltage is close to 20 V.

[GGoodwin]

Here are the modifications to make Figure 12. 0-V to 30-V Regulator Circuit work:

R1              : replace with 210 Ω or 205 Ω
R2 (adjustable) : replace with 5 kΩ
R3              : replace with 1.47 kΩ

These are encircled red in the image below

Here are the simulation results using Multisim Live

[aryniec-pw]

Is it wrong if I stay with my 0V to 20V circuit and LM317, just change the potentionometers values to values you've recommended?

Just asking.

[GGoodwin]

In my previous reply I intended to provide the modifications to "Figure 12. 0-V to 30-V Regulator Circuit" both for the original purpose of 0-V to 30-V Regulator and for the reduced-output 0-V to 20-V Regulator that you need. However, I was only able to complete the first part. I had the opportunity to log in yesterday but the computer I was using has only Snipping Tool (instead of a full image editor such as Paint) and Calculator is not installed so I have to use a less familiar online calculator. I then decided to defer my plan because I might spend too much time if I continue.

Finally, I have free time today and here are the modifications needed to convert "Figure 12. 0-V to 30-V Regulator" to "0-V to 20-V Regulator":

R1              : replace with 154 Ω, 158 Ω, or 150 Ω
R2 (adjustable) : replace with 2.5 kΩ
R3              : replace with 1.1 kΩ
Input Voltage   : lower to about 24 V or 25 V

These are encircled red in the image below

Here are the simulation results using Multisim Live

[GGoodwin]

In my previous reply I committed a mistake in Multisim Live simulation. What I should simulate is the modification to convert "Figure 12. 0-V to 30-V Regulator" to "0-V to 20-V Regulator". Thus, a simple p-n diode should be used but I failed to replace the Zener diode (voltage reference) in the circuit. The screenshots of corrected simulation are below