radiated emission SEPPIC 24W

[seridj_mse]

HI,

We have tested our equipment SEPIC DC DC input:9-30V output : 12V/24W (PCB 2LAYER) for CISPR 16 radiated emission limits. The emission result is attached. I have trouble shooted the problem element.

for pics i know its about quartz 50Mhz but the probleme is with renonant , i tried with RC , and RDC snubber but i cant solve probleme

 

[scopeprobe]

YES i know , with my probe i have only image of noise and i work to reduce this noise below -40dbm to pass test.

yes of corse it will reduce noise but how i can add this foil in my borad for industrial use and how its cost ....

Typically if screening addresses the issue then production solutions maybe consider a better inductor/transformer with a screen included in the part, a screened box or copper tape over the top of your transformer to 0v by design, or even some ferrite material on the top of the transformer to absorb (& turn to heat) the RF. Yes it comes with a delta cost but the question i'm asking is, is it the cost of compliace if the approach is fixed. I agree they're not attactive propositions to cost targets but switching converters without screening can be a challenge at the best of times. Without knowing the precise proportion of the noise associated with each part you have to try it and make a judgement if the result is significant enough.

 

[scopeprobe]

HI,

We have tested our equipment SEPIC DC DC input:9-30V output : 12V/24W (PCB 2LAYER) for CISPR 16 radiated emission limits. The emission result is attached. I have trouble shooted the problem element.

for pics i know its about quartz 50Mhz but the probleme is with renonant , i tried with RC , and RDC snubber but i cant solve probleme






View attachment 178636View attachment 178637

Just another Tip & sorry if you already know this. For your Rigol it may be useful to turn off the 10db Attenuation and Switch on the PreAmplifier which will have the positive effect of lowering the noise floor and may make some of the additional frequencies visible. Also has you only seem interested between 30Meg and 1Ghz change your start and stop frequencies to be closer to what you want to look at have make your bandwith smaller you may find the plots will give you more useful data. Oh and also using the dBuV scale in the Rigol will align the scales with your test house, even though the measurements are only relative

 

[seridj_mse]

Just another Tip & sorry if you already know this. For your Rigol it may be useful to turn off the 10db Attenuation and Switch on the PreAmplifier which will have the positive effect of lowering the noise floor and may make some of the additional frequencies visible. Also has you only seem interested between 30Meg and 1Ghz change your start and stop frequencies to be closer to what you want to look at have make your bandwith smaller you may find the plots will give you more useful data. Oh and also using the dBuV scale in the Rigol will align the scales with your test house, even though the measurements are only relative

ah thanks for information , no i didnt use analyzer before

 

[seridj_mse]

So the new scope without any change in pcb :

mesure around diode ref B360B.

mesure around coupled self.

and my last pcb and change ref of diode and add 50R in gate mosfet i have :

i think -40dbm is equivalent of 67dbuV .