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Inquiries related to SMPS implemented with TOP257PN

Posted by: Kenneth.Seo on Fri, 07/30/2021

Dear All,

I have a few questions below, could you help me?

1. The switching waveform of TOP257PN is driven at about 30Khz, the product data sheet is 66Khz switching operation

2. Attached waveform input: 220V
                         Output: 5V 0.27A / 12V 0.03A

  This is the switching waveform for each part. What causes the output ripple current of 12V to exceed 400mA?

3. Does the position issued by the above 12V output ripple have anything to do with switching?

   ** Under the condition of 12V 0.8A, the ripple current of the output electrolytic cap is measured about 1.6A, which is considered an abnormal operation.
      Even after changing the 12V load to almost no-load under the above conditions, the MAX of the ripple current exceeds 400mA.

thanks in advance

 

Files

Attachment 大小
waveform 420.36 KB
schematic 217.34 KB
SMPS with TOP257PN_0.pdf 217.34 KB
switch waveform_20210729_0.pdf 420.36 KB

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Submitted by PI-csbabu on Tue, 08/03/2021

Hi Kenneth,

      Unfortunately I didn't find the attachment showing the switching waveforms. Please share the schematic, transformer design, input and output specifications to analyze the problem. Thank you.