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UCC28740: Jitter Function and Influence for EMI Optimization

Part Number: UCC28740

Hi Team,

For the jitter application of UCC28740, could your help with the following 2 questions?

1. When applying jitter frequency to improve EMI, comparing with non-jitter status, will the load regulationof the non-feedback circuit drop in the flyback circuit? More importantly, will the voltage of the non-feedback circuit in light load state go much higher?

2, In order to verify the visual effects of the jitter and non-jitter on load regulation rate, is there any additional circuits are recommended to add to disable the jitter function?

Thanks,

Rebecca

  • Hi Rebecca,

    First, Jitter will not impact the output regulation, and jitter is disabled in light load when Ifb current higher than 14.6uA.

    Second, as mentioned in above ,  The boundary of enable and disable jitter is Ifb current equal to 14.6uA. It's hard to measure the FB current. but you can test the switching frequency at ~30khz and 32khz to identify  the controller is running at FM mode or AM mode . while the power level is not too much difference around Ifb =14.6uA, shown in below control law.