Attached is a spreadsheet with waveforms of a power supply using the UCC28810. The waveforms show the pin voltages during the powerup sequence. I've used the VCC voltage as a reference for each waveform. The waveforms show the UCC28810 starting up initially and then shutting down for about 100mSec, and then starting again. This behavior is only observed when the supply has been powered off for about a minute. If the supply is powered on, and then shut off, and then powered up again within a minute, this behavior is not observed. This particular supply uses the UCC28810 as a buck current source, just like the secondary stage of your LED light power supply in App Note SLUU355a, Figure 2, page 5. However, we have observed the same behaviour in our other power supplies where the UCC28810 is used just like the boost stage shown in the same App Note, Figure 1, page 4. The behaviour doesn't cause us a problem except that we need a large capacitance to hold up VCC for 100mS. We would like to know if TI has seen this before.
John
