Wall Wart PSU Questions

[angrykoko]

So I have a couple wall power supplies and I've noticed that the output volts stated on the plastic is never what it really is.  For example:
I have one that says it's 9v DC but hook it up to a DMM and it's 12v DC
I have another that says 12v DC but it reads 14v

• Is this because they are not a "regulated" type (a term I've heard before when folks talk about these)?
• What does "regulated" really mean when we talk about a wall psu?
• I've poked around Mouser but I couldn't see anything obvious that would indicate Regulated / non regulated. Is there a different term?
• What if I really really wanted something locked down closer to 12v, what specs would I look for?

Thanks!
Koko

[twin1965]

This explains it quite well:

http://www.apogeekits.com/power_adapter_selection.htm

For effects pedals it's a good idea to get a well filtered regulated power supply with low ripple.

When buying one look out for the terms: regulated, smps, switching or switch mode power supply.
Sent from my GT-I9100 using Tapatalk 2

[RobA]

With unregulated or even regulated supplies, they need a load on them to output the correct rated voltage. Your DMM won't be putting a heavy enough load for the regulation to work. Try putting a few mA load on it using a resistor and LED or two and then measuring again.

If it is an unregulated supply, and the input voltage is higher than specified, which your wall power can be, then you might be a bit higher on the output too.

[Govmnt_Lacky]

The rating on ANY of those wall wart types... regulated or non-regulated just means that the PS will put out that much voltage UP TO that much current being drawn.

EX: If the PS says Output: 9VDC @ 500mA

This means the wall wart will put out 9VDC UP TO a draw of 500mA. If you plug it into a circuit that draws, lets say, 600mA... then the PS might only put out 7.5VDC and so on.

The difference between a regulated and non-regulated PS is that the NON-regulated ones will usually put out MORE than the stated amount up to the current draw listed. For my example, it might be up to 13VDC when at a small current draw and as you approach the 500mA limit, the voltage will get closer to 9VDC.

A regulated PS will start at the listed voltage (9VDC) and keep that voltage level until you reach the rated current draw.

Are you confused now? 

[angrykoko]

Thanks!

Not confused at all, excellent information.

Confirms what I was guessing regulated meant.  Didn't know about the lack of load causing non-regulated to be high.
Really great stuff.. Thanks again

Koko

[RobA]

Depending on the type of regulator being used in the device, the output voltage can be high even in a regulated power supply. It doesn't usually matter because the times you would have a power supply with that small of a load are rare, but I've run into the issue with couple of things I've played with where the current draw was down in the 100µA range and the converter I was using sat at about 14V when it should have been at 9V. It turned out that the converter needs about 5mA on it to regulate the output well.