EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: MikeLemon on September 24, 2018, 04:57:23 pm
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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.
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Ceramic caps making the noise?
Easiest fix may be to move up the switching frequency above 25kHz...
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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.
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Could also be board layout, the traces are inductors and the PCB is a sounding board?
Potting could reduce the noise.
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Traces near a steel chassis, where you get nice magnetic forces turning the chassis into a speaker.
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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.