
Example: 100 W CCM PFC
- Number of switching cycles per line cycle varies with load current
- You might get 3560.7 or 3561.2 switching periods per line period instead of a nice round 3561
- POP will fail
- No POP, no AC

For POP to succeed, we need the total number of switching periods in an AC line cycle, when added together, to equal exactly one AC line period.