PSU Terminology

[Rocketman46]

Hi All,

Just a very general PSU question about what modes a PSU runs in.

Can somebody confirm what "free-Running" mode means? I understand "No Load" and "Under-Load" but i have never heard of "Free-Running"?

Look forward to your replies.

Jeff

 

[treez]

My friend i can assure you, there is no such term in the general PSU world.
Unless of course it means a PSU that runs by its own analog control circuitry, without it having its behaviour changed by a microcontroller.

 

[Rocketman46]

Hi,

I have never heard of it before either.

I am working on a document, and it mentions test by design and not test in "free-running" mode.

Somebody mentioned a flyback with a clock connected is in "free-running" mode?

Does this mean it is in free-running mode?

Thanks ,

Jeff

 

[treez]

I think sometimes SMPS are denoted as "free-running" if they run kind of open loop, with a "dumb" oscillator simply switching the fet continuously at a fixed duty cycle......eg a CCM buck on fixed load run at a fixed "free-running" duty cycle will give an output voltage of Vin/D.

its called "free-running" because no control system has handles on it.....ie, its "free".

 

[Rocketman46]

Thanks Treez, good explanation.

 

[KlausST]

Hi,

If there is a document, then give us the link to it.
Usually there is some explanation of the phrase or an information where it can be found.

Maybe a service manual, maybe some test description...

Klaus

 

[mtwieg]

I am working on a document, and it mentions test by design and not test in "free-running" mode.

Somebody mentioned a flyback with a clock connected is in "free-running" mode?

Perhaps it's referring to a controller which can be synchronized to an external clock. Free running mode might refer to operation when the external clock is absent, and the controller defaults to its default frequency.

Can you just post the document here?

 

[treez]

Perhaps it's referring to a controller which can be synchronized to an external clock. Free running mode might refer to operation when the external clock is absent, and the controller defaults to its default frequency.

...thats the answer i was looking for.....my money's on this....i am sure i remember "free running" being used in this context.