Noise in smps

Thread Starter

tpseh9985

Joined Aug 31, 2009
4
Hi,

I am using SMPS in my design to reduce temperature raising rate. The drawback is that noise generated is quite high, about 10%. So, I am finding a way to reduce the noise. May anyone suggest a way to reduce the noise? Some information is that my SMPS is at 100kHZ. Can I assume that the noise is at 100kHZ? I try using bandstop filter at 100kHZ. But it does not work. Please help me on this. Thank you.
 

Thav

Joined Oct 13, 2009
82
If it's a hard switching power supply (most likely) then the noise generated by it will have frequency content up to 1MHz at least. I recently did a design at 400kHz that had radiated noise up to 30MHz!

SgtWookie and Bill are putting you on the right track.
 

bountyhunter

Joined Sep 7, 2009
2,512
Hi,

I am using SMPS in my design to reduce temperature raising rate. The drawback is that noise generated is quite high, about 10%. So, I am finding a way to reduce the noise. May anyone suggest a way to reduce the noise? Some information is that my SMPS is at 100kHZ. Can I assume that the noise is at 100kHZ? I try using bandstop filter at 100kHZ. But it does not work. Please help me on this. Thank you.
Do you mean EMI noise as in electrical interference?

Some information is that my SMPS is at 100kHZ. Can I assume that the noise is at 100kHZ?
No, the EMI generated will have significant energy content out to hundreds of Mega Hertz.

Containing EMI in a switcher is not a simple topic, it has many facets. It requires laying the PS out optimally, using shielding correctly, and L-C filters on lines entering and leaving the hot areas so EMI is not conducted out.
 
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