I am designing a 120W PFC using the TI UCC28051 controller. The converter works as it should when I look at the output voltage which is about 396 V, but when I look at the current through the inductor it looks like the controller enters some kind of burst mode.
You can see a plot of the inductor current (green) and gate signal (yellow) below, during a 50 Hz cycle, the converter was delivering 60 watt to a load when the plot was made:
I had expected to se a current shape evenly distributed over the entire cycle, where the average current would follow a sinus. I cannot find any answer in the datasheet on how to solve this so therefore I would like to ask if anybody have seen a PFC behave this way before? Or if there is somebody who might know what my problem could be?
We will need a copy of your schematic including all part values to determine the cause of your problem. Once we get that information we may require further scope pictures to add in the analysis.
It turned out to be the IC which was malfunctioning.
I had newer thought of it myself since the PFC was regulating but somebody at another forum asked if I was sure the IC worked so I replaced it with a new IC and after that everything worked like it should.
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