Re: DC Power Supply Question



Ignoramus26315 wrote:

> I need an approximately 16V DC power supply, to drive a few IC chips
> and such.
>
> I have a pile of old wall wart power supplies, from things that I have
> long thrown away. One of them is a 12V nominal DC power supply by
> Motorola, 2.4W output.
>
> To my surprise, when I measured output of that 12v supply, it was
> producing 16.4 V! Imagine my surprise. I have a relatively nice extech
> multimeter, so I am relatively confident of this result.
>
> So, I am confused, how can a 12 V power supply produce 16.4V? Why was
> it labeled 12V if it supplies 16.4 V? Am I confused by something?
>
> This voltage is pretty ideal for my purpose, but I want to get some
> clarity.

You were measuring *no load*.

All wall warts behave like that. They are 'unstabilised' power supplies.
Try measuring with the rated load.

I'd never trust the voltage on a wall wart label anyway !

Graham

.

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