Other Parts Discussed in Thread: UC3854
Hello, I started to use UC3854ADW from 2000 in many of our products for Power Factor Correction. The power range is from 500W to 5KW in a single phase power system. In the past 18 years, the input current waveform was nearly perfect, it is almost the same shape of input voltage, and the quality is very stable. However, recently, the input current waveform was distorted when we compare with the controller UC3854A made before 2018. The Power Factor is dropped sharply after 2018. We see spikes when the current happened at zero crossing(Figure 1). The harmonic current is over the limit of 1000-3-2 class A. We confirmed if UC3854ADW made before about 2018(do not know the exact date), the input current was perfect(Figure2). I would like to know if TI changed the design/process recently. And if other customers have the same complain.
Figure 1: Channel 3 purple current has large spike at zero current crossing. The PFC controller at this figure was made in 2019.
Ref: Channel 1 is AC Input voltage at 220V. Channel 3 is AC input current.
Figure 2: Channel 3 purple waveform is the input current has no spike at zero current crossing. The only difference is the chip UC3854A was replaced from the newer date code to the old date code one(2014). All of the rest components are the same.
