T
treez
Guest
This post relates to this closed thread, as there are further questions about the LT3799 Active PFC Flyback controller…..
https://www.edaboard.com/showthread.php?t=332473
Hello,
The LT3799 is said to be a “Flyback controller with Active PFC”.
However, when I ran the linear.com provided simulation of the LT3799 in LTspice, it is evident that the current is not really in phase with the line voltage. (as the attached waveform shows…the power factor is 0.97)
I have attached the LTspice simulation that they provided here, and have LC filtered the mains input current, so it can be easily seen. You can see that it’s not in phase with the line voltage.
Why are they saying that it is Actively Power Factor Corrected?.......when all it is doing is making the primary peak current be a scaled factor of the primary DC Bus voltage? (As you know, that provides a power factor of unity with the Boundary conduction BOOST topology…..but NOT with the Flyback topology).
- - - Updated - - -
Also, the LT3799 sets the primary peak current on the basis of the "Vin_sense" pin voltage, and the lowest of the voltages voltage on the three CNTRL pins......so where in the LT3799 datasheet is the graph which shows primary peak current against Vin_sense voltage, and there should be a series of such graphs for the various CNTRL pin voltages.....i cannot understand why they dont show such a graph?
https://www.edaboard.com/showthread.php?t=332473
Hello,
The LT3799 is said to be a “Flyback controller with Active PFC”.
However, when I ran the linear.com provided simulation of the LT3799 in LTspice, it is evident that the current is not really in phase with the line voltage. (as the attached waveform shows…the power factor is 0.97)
I have attached the LTspice simulation that they provided here, and have LC filtered the mains input current, so it can be easily seen. You can see that it’s not in phase with the line voltage.
Why are they saying that it is Actively Power Factor Corrected?.......when all it is doing is making the primary peak current be a scaled factor of the primary DC Bus voltage? (As you know, that provides a power factor of unity with the Boundary conduction BOOST topology…..but NOT with the Flyback topology).
- - - Updated - - -
Also, the LT3799 sets the primary peak current on the basis of the "Vin_sense" pin voltage, and the lowest of the voltages voltage on the three CNTRL pins......so where in the LT3799 datasheet is the graph which shows primary peak current against Vin_sense voltage, and there should be a series of such graphs for the various CNTRL pin voltages.....i cannot understand why they dont show such a graph?