Hi,
Can someone direct me to a tutorial or explain in detail from basics the modes of Constant Voltage and Constant Current in Power Supplies?

 

Hi,
Can someone direct me to a tutorial or explain in detail from basics the modes of Constant Voltage and Constant Current in Power Supplies?

Simple, CV mode monitors the output voltage of the supply and increases or decreases the current as needed to maintain the programmed voltage, while CC mode monitors the output current and increases or decreases the voltage as needed to maintain the programmed current.

They names pretty much say it all, don't they?

 

Additional info, if not obvious, is that the CC and CV modes only work within the current and voltage limits of the power supply.

Another note, is that it can go between the CV and the CC mode as the load resistance changes.
Suppose the CC is set to 1A and the CV to 5V.
It will thus be in the CC mode when the load is below 5Ω and the CV mode when it goes above 5Ω.

 

Thanks WBahn, crustchow. This is a great starting point. Do you have tutorial sheets of examples or exercises that relates to this?

 

Thanks WBahn, crustchow. This is a great starting point. Do you have tutorial sheets of examples or exercises that relates to this?

What kind of "tutorial sheet" or "exercise" are you looking for?

This is akin to asking what the difference is between front-wheel drive and four-wheel drive and, after being told the difference, asking for tutorials and exercises related to it?

What, precisely, is it you are looking for?

 

Do you have tutorial sheets of examples or exercises that relates to this?

I believe the functions have been well explained.
Are you asking when you use CC and/or CV modes in actual practice?

 

To answer your question: yes. Because this concept is applied in Battery Charging, Solar-Powered Supplies, Step-down Buck Converter and more. So I wish to look at more practical examples or exercises!

 

To answer your question: yes. Because this concept is applied in Battery Charging, Solar-Powered Supplies, Step-down Buck Converter and more. So I wish to look at more practical examples or exercises!

It's all about the application.

If your application needs a constant current, then use a constant current supply. If you application needs a constant voltage, then use a constant voltage supply.

In either case, choose (or design) a supply that takes into account all of the other things that may be important, such as how closely regulated the controlled parameter needs to be and what limits there need to be on the uncontrolled parameter. Also what happens if the output is short-circuited or open-circuited.

When I was working at NIST we had superconducting magnets that needed closely-controlled constant current supplies. These were low voltage (max output voltage would trip at about 2 V) but delivered up to 120 A. A very big concern for us was what would happen if things became open-circuited because a 74 H inductor with 110 A of current flowing in it will flat light you up it it gets open-circuited. Current stability wasn't a huge concern because 74 H of inductance makes for a great low-pass filter (and that was the low-inductance magnet). The current supplies for the samples, on the other hand, were very different. Here we needed to supply up to 4000 A of current at a fraction of a volt and the noise had to be low enough that we could measure DC voltages across the sample that were just a few nanovolts. I demonstrated one day (quite unintentionally) that someone standing ten feet away messing around with a three-foot section of rubber vacuum hose could completely trash a measurement due to the fields generated by the moving charges on the hose. Very different applications leading to very different designs.

 

It's all about the application.

If your application needs a constant current, then use a constant current supply. If you application needs a constant voltage, then use a constant voltage supply.

In either case, choose (or design) a supply that takes into account all of the other things that may be important, such as how closely regulated the controlled parameter needs to be and what limits there need to be on the uncontrolled parameter. Also what happens if the output is short-circuited or open-circuited.

When I was working at NIST we had superconducting magnets that needed closely-controlled constant current supplies. These were low voltage (max output voltage would trip at about 2 V) but delivered up to 120 A. A very big concern for us was what would happen if things became open-circuited because a 74 H inductor with 110 A of current flowing in it will flat light you up it it gets open-circuited. Current stability wasn't a huge concern because 74 H of inductance makes for a great low-pass filter (and that was the low-inductance magnet). The current supplies for the samples, on the other hand, were very different. Here we needed to supply up to 4000 A of current at a fraction of a volt and the noise had to be low enough that we could measure DC voltages across the sample that were just a few nanovolts. I demonstrated one day (quite unintentionally) that someone standing ten feet away messing around with a three-foot section of rubber vacuum hose could completely trash a measurement due to the fields generated by the moving charges on the hose. Very different applications leading to very different designs.

That reminds me of a research establishment I was involved with that was experimenting with creating artificial ball lightning. Two approaches to this were being tried, one was using 2 Volts at many thousands of amps supplied from dozens of fork lift truck battery cells wired in parallel.
They had a 3 foot square block of copper and a 6 inch diameter contact made of tungsten carbide. The two where rammed together with a pneumatic ram, there followed a deafening bang with balls of volatilised copper in some plasma state hovering over the copper plate for a second or so. Power was cut off by the crater made in the copper being deeper than the stopped contact could reach. It was the difficulty in directing and sustaining the balls of energy that was the hardest task.
The 2 nd method they tried that I was involved with, used 750 kV at hundreds of amps and indeed we did achive some some success in control with massively powerful magnetic fields and lots of liquid Nitrogen. I'll say no more in case the results are still secret. The 70's were when a lot of exciting things were going on until the funding was stopped by bureaucrats who were more interested in counting the pennies instead of promoting technological advancement.

 

To answer your question: yes. Because this concept is applied in Battery Charging, Solar-Powered Supplies, Step-down Buck Converter and more. So I wish to look at more practical examples or exercises!

If you are working on a project that you want to make sure does not go up in smoke when you connect it up for the first time, set a low CC mode.

 

Bench power supplies are commonly designed as CC and CV.

One important thing to remember is you cannot have both at the same time.

Think of CC and CV as limits.
CC sets the maximum current output.
CV sets the maximum voltage output.

The CC/CV power supply unit (PSU) will always hit one of those two limits and will automatically be in CC or CV mode, which ever limit is reached first. The CC light or CV light will indicate which limit has been reached (assuming the PSU has CC and CV indicator lights).