Poynt,

I have to respectively disagree so I'll give my logical explanation for this issue.

I don't understand your point/argument, sorry.

Respectfully, I have to say I stand by my statement.

A few salient points from "Power Measurement 101":

1) The power of a source, or a component (or device as a whole) is measured by taking the voltage directly across it and the current into (through) it and multiplying the two for power as a product. For scope type measurements, the average (MEAN) is taken of a minimum of 10 cycles of operation of this product. (There is obviously a bit more detail here I've not included for clarity).

2) The polarity of "power" when correctly measured for a source is negative. The polarity of "power" for all loads connected to a source are positive. Most often folks ignore the polarity however.

3) As a consequence of 2), power is conservative. Just as there is "KVL", there is also an implied "KPL", whereby all the "powers" in a circuit and source sum to zero.

Let's take your sim for example:

a) Power measured from the 20V source is 3.38W. Correct.

b) Power measured in the 50 Ohm load is 1.72W. Correct.

c) Power measured across MOSFET/DIODE/CAP is 0.561W. This is incorrectly associated with input power to the transformer. As per 1) above, it is not.

d) Power measured/computed when 20V is subtracted from the voltage measurement in c), is 2.81W. This is the actual input power measurement as per 1) above.

Surely you do not believe that by strange coincidence, 3.38W=0.561W + 2.81W ? I can assure you that it is not a coincidence. This is simply an illustration of the power balance in every circuit (in this case, between the 20V source, and the input side of the transformer).

What about the 1.72W measured in the 50 Ohm load? Since we know that 2.81W is what goes into the primary (and comes out the secondary), we know that the remaining 1.09W (2.81W-1.72W) must be getting dissipated in the output MOSFET.

Attached is a diagram illustrating the above points. Note, L5 is actually a source on the output side of the transformer, so its power is negative at -2.81W. There are two power loops, one on the input and one on the output side, and each sums to zero as per 3) above.