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INN3167C - EMC Test Problems

Posted by: Matteo on

Hi,

I'm using INN3167C IC in a wide range power supply with 2 outputs, 5V and 28V, total power 30W. I'm using an EF25 transformer.

I have problems in the power emissions tests (30 MHz-300MHz). I tried to add snubbers on the primary and seconday side, adjust clamps in the primary and secondary side...tried to adjust the layout of the board following the suggestion of the application notes but I'm not able to solve the problem.

Can you help me to solve the problem?

Do you need some documentation?

 

Thanks,

Matteo

Files

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INN3167C.JPG 102.93 KB

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Submitted by PI-Martok on 01/22/2022

Hi Mateo,

    Thanks for using Power Integrations InnoSwitch3 device. May I see your schematic, PCB layout and transformer design?  Here some of my initial suggestions

1.  Shorten all noisy loops. (bias supply loop, Primary snubber loop, secondary rectification loop and primary drain loop.)

2.  Shorted Primary drain copper trace. must be close to the primary winding terminal

3.  Adding RC across the primary bias diode might help reduce radiated EMI. You can also try to use standard recovery diode instead of fast recovery on the primary bias diode

4.  Add high frequency common mode choke on the input side ( < 100uH)

5. Add small capacitor across the primary snubber diode (start with 47pF)

6. Add copper shield around the transformer core 

Submitted by Matteo on 02/07/2022

Hi,

thanks for your feedback.

I have more or less solved the problem but there is a strange behavior in the secondary side.

I always see a 16 MHz oscillation across the secondary mosfet: I inserted RC snubber (using different values) on the mosfet and on the secondary winding but it is not possible to remove this oscillation.

Do you have any suggestions?

Attached the schematic, layout and transformer design.

 

Thanks,

Matteo.

 

 

 

 

첨부 파일 파일 크기
Schematic.JPG 99 KB
Layout_2.jpg 227.42 KB
Trasfo.JPG 65.36 KB
Submitted by PI-Martok on 02/15/2022

Hi 

   Can you try adding RC across the secondary winding? Sometimes some parasitic may be filtered on across the secondary winding

 

Submitted by s.zavgor on 09/03/2023

Hi Matteo,

I have a very similar problem with radiated emission around 30MHz-60MHz. Could you tell me about your decision that helped solve this problem?

 

Thanks, Sergii.

Submitted by PI-Martok on 09/07/2023

Hi Mateo,

          Can you try to add copper shield around the EF25 transformer?  I think EMI noise could be radiated from the EF25 transformer since it has a large winding area. Please also provide pictures of your board, schematic and pcb layout if this solution did not work on your design.

 

Best Regards,