Comparing Voltage Boosting Circuits | Hacker News Reader

Comparing Voltage Boosting Circuits

blog.georgovassilis.com

That first circuit makes no sense. DC into a resistor and then a transformer won't do anything but create heat after the core saturates.

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

Thank you. That's exactly the case.

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!

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?

As I played around with the simulator I found that higher input voltages lead to better efficiency. My intuition is that as the first BC provides a higher input voltage to the 2nd BC, the 2nd BC operates with a higher efficiency.

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

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.

If you need higher voltages at modest currents you can consider using one of many voltage doubler circuits after the booster. Just make sure you have enough Ic and simulate it.

https://en.wikipedia.org/wiki/Voltage_doubler

https://en.wikipedia.org/wiki/Voltage_multiplier

That's pretty bad... When calculating the efficiency, transitional effects and non-ideality of parts are critical. And what does the author choose? A generic mosfet, unnamed diode, constant duty cycle.. this is not realistic at all.

And the selection of parts seems just random, especially given low output power (0.1W), no design will use it. A MOSFET for 5V circuit. 1KHz switching frequency (!). Fixed duty cycle and voltage regulation via inductance changes (!!). Huge inductors (0.3H!), because of very low frequency.

All this blog post shows is that author can put parts into simulator. Very little relation to real world.

If you get rid of the diode and instead use a well timed MOSFET, you can save a diode's drop worth of energy on each cycle. Synchronous switching supplies as they are called can have over 95% efficiency

Have you considered this one? https://en.m.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_gen...

Isn't that a charge pump? If so, then yes, but it didn't perform well enough to be included.

wehnelt interrupter / electrolytic interrupter can work as a switching up or down converter, fully analog, no transistors, thyristors, no ic, no capacitors, just coil.

single electric motor can be used stationary as a transformer

or in pairs, in motion like inverter, rectifier, (synchronous rotary converter)

autotransformer

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