PSUDII simulation vs reality

[Navyblue]

Originally Posted by SY

You can't use a simple formula since each consecutive stage forms a reactive load with the previous stage. Likewise, the previous stage shows a reactive source impedance to the succeeding stage. So the usual simplifying assumptions (zero source impedance, infinite or pure resistive load impedance) don't hold. That's why sim software like PSUDII is so valuable- the hand calculations are not easy.

Thanks a lot. That certainly clears it up.

How about the low pass frequency of each LC stage? Can it still be calculated with the simple formula like it is on its own?

[DF96]

Only approximately, for the same reason: each stage is loaded by the next. Fortunately in PSU design 'approximately' may be good enough, as component tolerances are wide anyway.

[Navyblue]

Thanks guys.