×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Noisy Power supply

Noisy Power supply

Noisy Power supply

(OP)
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?

RE: Noisy Power supply

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

RE: Noisy Power supply

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.

RE: Noisy Power supply

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

RE: Noisy Power supply

(OP)
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.

RE: Noisy Power supply

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources