UCC28180EVM-573: pfc conductive emission issue

Bobby Lam95

Part Number: UCC28180EVM-573
Other Parts Discussed in Thread: UCC28180

Hi,

I used the reference design UCC21180EVM-573 in my power supply. As the result, it failed the conductive emission at the program frequency 40 Khz with the the Rfreg of 26.1 Kohms. I have an AC line filter in the front end after AC input to pass some of the high frequencies of 163 Khz, but still have high peak of 40 Khz. I tried to program the frequency up and down from 15 to 100 Khz, but the amplitude of the frequencies don't change. Do I need to add one more external line filter? if yes, what would the values of the inductance/capacitors be? I don't have any way to sweep the frequency band. Any advise would be greatly appreciated. Thanks

Bobby.

over 2 years ago

0 David Huang33 over 2 years ago

TI__Genius 9140 points

hello Bobby,

can you send the schematic and the set up process of the AC input line filter to me?

UCC28180EVM only has one stage common inductor at input filter circuit.

I would suggest to add a second stage of common inductor and X cap. You add the second stage in front of L1 in the evm, and start with 1uF x cap and 2mH common mode inductor to see whether it works.

0 Bobby Lam95 over 2 years ago in reply to David Huang33

Intellectual 320 points

Hi David,

Thanks for your suggestion. I have line filter mounting on the chassis before entering the board as such. This helps to eliminate some of the frequencies, but not the switching frequency of the UCC28180.

0 David Huang33 over 2 years ago in reply to Bobby Lam95

TI__Genius 9140 points

Hi Bobby,

since we do not have the line filter circuit, I would suggest you can add one more stage input filter as I suggested yesterday.

if it can still not solve your issue, you can add one Pi filter after bridge.

0 Bobby Lam95 over 2 years ago in reply to David Huang33

Intellectual 320 points

Hi David,

Thanks for your suggestion. I used a receptacle with a filter built in instead of a plain one. This helped me to pass the test. Thanks for you help. Bobby.

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UCC28180EVM-573: pfc conductive emission issue