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Electronics => Projects, Designs, and Technical Stuff => Topic started by: MikeLemon on September 24, 2018, 04:57:23 pm

Title: How to eliminate acoustic noise in high current circuits?
Post by: MikeLemon on September 24, 2018, 04:57:23 pm
Hello there,

In every circuit I build with a simple switching mosfet at 10KHZ+ with 5A+ (to around 40A) I get audio able noises even tough I don't use any inductive components like inductors and such.

Any hint on how to eliminate such noises?

Thanks for helping.
Title: Re: How to eliminate acoustic noise in high current circuits?
Post by: hlavac on September 24, 2018, 05:03:56 pm
Ceramic caps making the noise?
Easiest fix may be to move up the switching frequency above 25kHz...
Title: Re: How to eliminate acoustic noise in high current circuits?
Post by: SiliconWizard on September 24, 2018, 05:31:29 pm
Yes ceramic caps can be pretty noisy especially SMD ones, transmitting vibration to the PCB they are soldered on.

A few pointers:
https://www.edn.com/design/components-and-packaging/4364020/Reduce-acoustic-noise-from-capacitors (https://www.edn.com/design/components-and-packaging/4364020/Reduce-acoustic-noise-from-capacitors)

Now if you don't use any ceramic cap in the power section we'll have to look elsewhere obviously.
Title: Re: How to eliminate acoustic noise in high current circuits?
Post by: tpowell1830 on September 24, 2018, 05:40:01 pm
Could also be board layout, the traces are inductors and the PCB is a sounding board?

Potting could reduce the noise.
Title: Re: How to eliminate acoustic noise in high current circuits?
Post by: SeanB on September 24, 2018, 06:51:37 pm
Traces near a steel chassis, where you get nice magnetic forces turning the chassis into a speaker.
Title: Re: How to eliminate acoustic noise in high current circuits?
Post by: ejeffrey on September 24, 2018, 08:04:29 pm
Also remember that your circuit includes the part *before* the switch too.  If you have inductors or capacitors on the input/supply side they can make noise just as well as the load side.