I've build the following linear power supply:
Before building it I tried to model it in LTspice. I couldn't find an LTspice model of L4941BV LDO (datasheet [PDF]) or a suitable replacement. Thus I used the following "naive" model:
R1, R2, L1 and L2 are measured resistance and inductance of a transformer windings. V1 is 50Hz, amplitude: 310 V. Here is Vout:
My idea was following. Let's say that all extra voltage turns into heat, and also account for ~10 mA quiescent current of LDO itself. In other words assume that this circuit's output power is ~0.95W.
Naturally this model turns out to be inadequate. It predicts PF 0.442 and efficiency 32%. The real device can produce up to 217 mA before a noticeable ripple (60 mV) will be observed. Under these circumstances it's measured PF is 0.925, consumed power - 2.75 W and efficiency - about 39.5%.
I tried to play with values used in the model but didn't come even close to observed PF and efficiency. Thus it looks like a less naive model is required.
The problem is I have no clue how to make an accurate model of an LDO. Could you please explain how it can be done or at least suggest some literature on the subject.