Yeah, and given that the mistake is consistent between the text and the image, I think the author just sort of doesn't understand inductors.

"The efficiency numbers aren’t based on calculations or research – I merely ran each circuit in the excellent Lush Projects simulator [SIM] and recorded the numbers it gave me."

I don't want to diss people for writing about stuff as they learn, but I wouldn't take this article too seriously. You can theoretically achieve very high efficiency with basic architectures. The main problem is that you typically also want to make the device small and cheap.

I think the transformer on it is just supposed to be a 'black box' to show what the other conversions are meant to be filling out

But it will make a single pulse when you first connect it. Dealing with inductive inrush transients can easily become the single most annoying thing in electronics design, besides ESD.

So annoying that a lot of OSHW designs seem to just completely ignore it! It's amazing things work as well as they do!

Nor does it make sense to measure the efficiency of a boost converter as a single, static number. In the real world, that'll depend on 1) the input and output voltages, 2) the load, 3) the switching frequency, and 4) the parameters of the inductor (like its resistance and saturation current).

(A big missing piece here is regulation - all of the test circuits are running open-loop with a 1 kHz square wave switching waveform. Real switching regulators observe the voltage at the output and adjust the switching duty cycle and/or frequency to hit the target voltage.)

The first circuit is a generic block diagram serving as a placeholder. All following circuits are implementations. It wasn't run in the simulator nor were efficiency numbers recorded for it.

The circuits simulated are valid, just that first picture is bad.

The serial boost converter is interesting, I've never seen that topology before - can anyone offer an explanation on how it works?

I assumed it was an ideal transformer, with near infinite inductance and never saturates