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UCC28950 / adding the spectrum spread circuit

Guru 20090 points
Other Parts Discussed in Thread: UCC28950
Hello,
 
Our customer are designing UCC28950 for their AC/DC power supply system.
Currently , they has EMI problem for achieving the CISPR 22 Class B.
Could you please kindly let me know as below ?
 
<Question 1>
Could you please let me know the spectrum spread circuit or any circuit for reducing the EMI ?
If there are any application note or reference, please let me know too.
I believe that UCC28950 don't have the spectrum spread future.
 
<Question 2>
Since UCC28950 control switching from the secondary circuit, we need pulse trans for isolation.
Does this method occur EMI than primary control ?
 
Best Regards,
Ryuji Asaka