Dear colleague,
Our board now uses TPS54525 to generate 3.3V power from 12V, and 12V is generated from 220V AC with AC-DC module. Now we have observed such a phenomenon. Several boards share a power supply strip, and the 220V AC power supply network fluctuates caused by switching the power of one board. Sometimes the 12V output of other boards also fluctuates through the AC-DC module. This fluctuation affects 3.3V through the TPS54525. Power on. As shown in Figure 1 below, the blue line is the 12V power waveform measured at the VIN pin of 54525, and the yellow line is the output 3.3V power waveform. The amplitude of the two fluctuations is about ±2V, and the duration of the fluctuation is about 200ns. , Because this time is much shorter than the switching cycle of the switching power supply, so the feedback of the switching power supply cannot compensate for this fluctuation. At present, I try to add capacitance to the power supply. Figure 2 below is our schematic diagram. On the basis of the original 0.1uF and 22uF capacitors, I added 1uF and 10uF capacitors to the input and output, but there is no obvious effect. Is there any other way to avoid or improve the 3.3V from 12V fluctuations?
Thanks a lot!
Best Regards,
Rock Su
