[sdiy] Vanilla electronics question

[Rutger Vlek]

Dear list,

Against my wishes, I'm working on repairing my eBike's rear light, instead
of building something synth related. However, I'm stumbled by a seemingly
simple circuit that just does not behave as I expected. Of course I
considered buying a new rear light, but for the sake of the planet (and my
own knowledge gathering), I'm trying to revive the original one.

The circuit is simple, I'll try to describe it. Positive voltage
(appox. 12V) from the bike's battery enters two red, parallelled power LEDs
(in forward direction), goes through a 150 ohm resistor, and then through
what seems like a Schottky diode (SMD package labelled SS16) in reverse
(!), non-conducting direction to ground. The point before the SS16 is also
connected via a capacitor to the positive supply.

I replaced the LEDs and they are testing fine now (didn't before). From the
start I assumed the SS16 (presumed Schottky diode) to be there for reverse
voltage protection, until today... when I looked at the direction in which
it's placed. Moreover, the resistance and power dissipation capacity of the
resistor don't seem to fit a traditional LED circuit. In other words, the
resistor would run the LEDs very close or over their maximum current
rating, and would burn out due to the heat it had to dissipate while doing
so.

So....can anyone tell me, what is this circuit? If I had to guess, it's
either:
(1) an attempt at a traditional LED circuit by someone who messed-up badly
(2) some kind of switching voltage regulator (the rear light indicates to
be capable of handling a supply anywhere between 6V to 12V). So I'm
guessing it's the latter.

If moderation feels this is way off topic, I can completely understand.
Although I'm interested to learn about this circuit, as it perhaps could
find its way into synthesizers too.

Rutger
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