#### CookingGirl

Joined Nov 20, 2023
1
Hi guys.
I have a question about the power supply current.
What function does the Current dial do?
The converter I made turns the Current dial, raises it, and the output is fine,
If you lower it, the output doesn't come out. What's the problem?

Thank you.

#### Ya’akov

Joined Jan 27, 2019
8,973
Hi guys.
I have a question about the power supply current.
What function does the Current dial do?
The converter I made turns the Current dial, raises it, and the output is fine,
If you lower it, the output doesn't come out. What's the problem?

Thank you.
Welcome to AAC.

Your question is extremely hard to follow. Here is general information about the constant current function of a power supply.

Bench supplies generally operate in two modes: Constant Voltage (CV) and Constant Current (CC). In CV mode, the voltage control selects a target voltage and the supply will increase the current until that voltage is reached.

In CC mode, the current control is set to a target current and the supply will adjust the voltage until that current is reached.

This is based on the formula $$\mathsf{V = {I\over{R}}}$$ where V is voltage (in Volts, V), I is current (in Amps, A), and R is resistance (in Ohms, Ω). As you can see from the formula, you can increase voltage by increasing current or reducing resistance, and increase current by increasing voltage or reducing resistance.

But, there is no direct way to increase current because the resistance of the load determines it. On the other hand, you can increase voltage by adjusting the output of your supply, and you can increase maximum current using the current control on it.

When you turn the current control all the way down, the supply will enter CC mode since any current is more that 0A. This means it will reduce the voltage to 0V to achieve it. If you have, say, a load of 1Ω and want a current limited to 1A, according to the formula above, and in practice, when set to 1A in this situation, the supply will regulate the voltage to 1V.

If you set the supply to a .5A limit, the output will be .5V to make that happen.

I hope that helps, but if not please try rewriting your post to be more clear.

#### MrChips

Joined Oct 2, 2009
30,467
Current and Voltage dials are limits, not operating conditions.
The power supply is always at one of the limits. It is either at the current limit or voltage limit, never both at the same time.

#### liaifat85

Joined Sep 12, 2023
48
Hi guys.
I have a question about the power supply current.
What function does the Current dial do?
The converter I made turns the Current dial, raises it, and the output is fine,
If you lower it, the output doesn't come out. What's the problem?

Thank you.
I think it will be hard to reply without any idea about the design of your converter.

#### MisterBill2

Joined Jan 23, 2018
17,790
I own a power supply that has an over-voltage limit control. When that control is set to zero there is no output. I got a great deal on the supply because it had no output. I read the directions and saw how to use it. That was a very good deal.

#### WBahn

Joined Mar 31, 2012
29,857
Hi guys.
I have a question about the power supply current.
What function does the Current dial do?
The converter I made turns the Current dial, raises it, and the output is fine,
If you lower it, the output doesn't come out. What's the problem?

Thank you.
How did you manage to make your converter if you don't know how it works?

What do you mean "the output doesn't come out"?

In either case, the current output will be determined by the lesser of the current limit you set and the current that is drawn by the load at the set voltage output.

#### dl324

Joined Mar 30, 2015
16,677
The converter I made turns the Current dial, raises it, and the output is fine,
If you lower it, the output doesn't come out. What's the problem?

The current limit adjustment should set the current at which the power supply goes into constant current mode. There us usually an LED that indicates CC operation.

#### MisterBill2

Joined Jan 23, 2018
17,790
In a correctly operating DC power supply, when current regulating is in effect, reducing the current setting will reduce both the voltage and the current. In addition, setting the current to zero will usually bring the voltage to zero.

#### AnalogKid

Joined Aug 1, 2013
10,944

It sounds like your supply has an adjustable constant-current limit feature. If the load on the supply exceeds the adjusted value, the output voltage starts to sag per Ohm/s Law. This can be used to limit the current into a circuit that has a fault. It also protects the power supply itself from output short circuits.

ak

Last edited:

#### MisterBill2

Joined Jan 23, 2018
17,790

It sounds like your supply has an adjustable constant-current limit feature. If the load on the supply exceeds the adjusted value, the output voltage starts to sag per Ohm/s Law. This can be used to limit the current into a circuit that has a fault. It also protects the power supply itself from output short circuits.

ak
I will do that when i can get to it, presently things have been re-arranged due to some changed priorities.

#### AnalogKid

Joined Aug 1, 2013
10,944
I was requesting the TS. I edited the post.

ak