Constant power load with LTspice?

Hello,
Do you know why this constant power load (20W) simulation won't work.

I need the resistor to dissipate 20W constantly , throughout the bus voltage excursions.
(LTspice schematic and simulation attached)

Here you go. Cant figure how you would build it, but I can simulate it.

I guess that a "constant power" circuit is a constant-voltage output SMPS connected to a fixed resistance load?

MikeMI, Amazing!, Thanks very much.

I'd spent longer than i'd care to admit trying to do that.

And yes, in the past, I always ,made up constant voltage SMPSs to do constant power loads, and it was nowhere near as good as what you have provided there.

-I am sure you will see the useage.....to assess the dc bus voltage excursions that smps's will give with certain value bus caps.....I used to do this in excel using an imperial method, but it assumed a constant input current of the smps, which of course it is not.

With the simulation you provided....just read it off and its easy and quick