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UCC28056: UCC28056 issue

Part Number: UCC28056
Other Parts Discussed in Thread: UCC28950

Tool/software:

Hi, 

The customer Liyuan haina is debugging the 300W ACDC power with  PFC (UCC28056A) + DCDC PSFB (UCC28950),  now one issue for PFC is that  at AC 250V input peak voltage with full load,  the inductor current goes to zero for more than 20us time and  then inductor current  starts to increase from 0A, and after a few switching cycles the inductor current  becomes very bigger and this current will trigger OCP, why? Please find the following abnormal waveform. CH1 is Vgs for PFC mosfet, CH2 is Vds for PFC mosfet,  CH4 is PFC boost inductor  current with abnormal bigger current. Thanks!

Best Regards

Linda