Power Supplies - Common Terms and Limitations

[Gryd3]

Gryd3 submitted a new resource:

Power Supplies - Common Terms and Limitations - What is a power supply (source) and how can I control the voltage and current?

I've seen this question come up a large number of times.
"I have a 12V 2000mA Power supply, but the device I have only needs 12V 350mA"
-or-
"How do I control the Current and Voltage going to my device?"

I'll also cover a couple terms such as Constant Voltage and Constant Current, and a break down of a battery to help you choose a power source for your project.

Constant Voltage
This is how the vast majority of Power Sources operate. The plug in the wall... it supplies...

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[dorke]

Gryd3 submitted a new resource:

Power Supplies - Common Terms and Limitations - What is a power supply (source) and how can I control the voltage and current?



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I have seen linear regulated wall-warts and actually have a few.
So, a slight correction in the "how do I pick a good supply?"
section is needed.something like this:

"If you need a constant voltage output use a voltage regulated wall-wart"

 

[dorke]

About the issue Constant Current :
In my view it actually started with protection of the Power Supply against excessive output current which may damage the P.S .
Most P.S actually only have that over current protection.
In this case the output voltage is set to zero volts and the current is at it's limit value.

The more expansive/LAB P.S and LED drivers do have Constant Current Mode with a possible variable current control.

There is also the"strange creature" -
Fold-back protection mechanizem ,
in which both the voltage and current of the P.S are reduced (gradually ,not at once to zero) to protect the Series Regulating Element of the P.S.

 

[Gryd3]

About the issue Constant Current :
In my view it actually started with protection of the Power Supply against excessive output current which may damage the P.S .
Most P.S actually only have that over current protection.
In this case the output voltage is set to zero volts and the current is at it's limit value.

The more expansive/LAB P.S and LED drivers do have Constant Current Mode with a possible variable current control.

There is also the"strange creature" -
Fold-back protection mechanizem ,
in which both the voltage and current of the P.S are reduced (gradually ,not at once to zero) to protect the Series Regulating Element of the P.S.

Thank you for the added details. Although I didn't put them in word-for-word I adjusted some of the wording to cover what you have pointed out to me.

 

[hevans1944]

About the issue Constant Current :
In my view it actually started with protection of the Power Supply against excessive output current which may damage the P.S .
Most P.S actually only have that over current protection.
In this case the output voltage is set to zero volts and the current is at it's limit value.

The more expansive/LAB P.S and LED drivers do have Constant Current Mode with a possible variable current control.

There is also the"strange creature" -
Fold-back protection mechanizem ,
in which both the voltage and current of the P.S are reduced (gradually ,not at once to zero) to protect the Series Regulating Element of the P.S.

Here is a nice article on foldback current limiting. I hate this mode of operation and much prefer that the heat sinks be sized to allow indefinite full current output at zero voltage.

 

[dorke]

Here is a nice article on foldback current limiting. I hate this mode of operation and much prefer that the heat sinks be sized to allow indefinite full current output at zero voltage.

Agree with you.
The "Hick-up mode" sounds even more annoying.
A good article.