Hello! I am designing a wide input range flyback converter using the altair04-900 for my formula student team.
For testing the switching behaviour, I simulated the ALTAIR04-900 using the schematics in the datasheet of figure 4-7. figure 4-6 shows results comparable with the values specified on the datasheet- with Idss(off) being 104uA instead of 80uA. Simulating figure 7 I made the following assumption: the IC should actually switch. My reasoning: Icc has the value of the operating current as stated in the datasheet. However the simulation results show discrepancies (reference see „simfigure7“); Icc has the expected value, but voltage at ZCD never goes above arming threshhold, therefore the IC should not be able to switch. My explanation: Some kind of brown-out, as Vzcd is below the internal clamping voltage as stated in the datasheet. Also notable: Vdc above 2.79V on COMP pin gives a converging error. Instead, I used a close value of 2.79Vdc. For further testing I altered figure 7 (reference see „mytest“) to ensure a voltage above arming threshhold and below the switch-on-logic. Still, the IC does not switch (reference see „simulationresults“)
I think that the model does not behave "logically" and I cannot simulate a realistic behaviour of neither the IC nor my flyback design schematic.
Is the model even suitable for "actual" switching? or does it only show pin behaviours?
If someone has any experience, elp is much appreciated.
If I made a mistake also please let me know.
many thanks in advance!
