Noisy Power supply

[PPC800]

I have a switching power supply that I am using and as soon as I turn it on, there is a very wierd squeking noise (very annoying), is this attributed to the frequency of the switching? Is there anything I can do to eliminate this very loud audible noise?

 

[itsmoked]

Does this noise occur only during the startup, as you aren't clear on this?

If it happens only on starting I advise you to ignore it. If it does this all the time try changing the load. Otherwise it has a problem. Different things cause the noise. Certain ones will mean failure in minutes some not.

I have a switcher I use to run a desk lamp. It chirps 5 times during startup and has for 7 years.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

If it is continuous, you may just have a cheap power supply. All switch mode power supplies make a high pitched whine to be sure, but quality products include filtering and shielding to mitigate it as much as possible. Cheap versions flooding the market from 3rd world countries right now do not necessarily go to that trouble.

If it's temporary, another possibility is that your PS is going into current limit or crow-bar disconnect on start-up because of some sort of inrush load on the output. That's probably what is happening with itsmoked's, especially on a lamp that may have a positive coefficient of temperature. When the lamp is cold, it has low resistance so the current is high and the PS can't supply it all. So when the current exceeds the PS's capacity, it either lowers the voltage to keep current lower (an expensive option by the way). More commonly, it uses its crow-bar circuit to just cut off the output, then on again, then off, then on, then off etc., but as the lamp warms up each time, the resistance increases so the current stabilizes and the PS is OK.

 

[itsmoked]

Yep, lots of entertainment. I flip the tiny switch I put thru a hole in the U-Channel.

Nothing happens for about 3 seconds.

Then, chirrrrrrp, chirrrrrp, chirrrrp, chirrrp, chirrp(visible light appears), chirp, silence and full light.

Oh 'nothing happens' unless your fingers stray into the supply and connect up. LOL

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[PPC800]

Yes the PS is going into current limit on start-up because the lamp (...in my spectrometer system) has to have a constant current.

I'll leave it on overnight and see if the high pitched whine goes away.

 

[itsmoked]

Oh if it is that way during normal ops... It won't go away. You may need to replace it for peace'en quiet.

I have a 1.5kW lab supply with a big fan in it. It doesn't seem very loud but after a few hours... It lands on yo like a ton of bricks.. Very, very, annoying all of a sudden.

Quiet is worth money.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com