SK14 diodes in a 12V DC LED circuit?

[cooperhow]

I just pulled apart a 12V LED anchor light for a small boat. When looking at the board, I see:

• 4x SK12 diodes
• 3x resistors
• 1x empty capacitor pad
• 8x SMD LEDs

I assumed that 4 Schottky diodes were used for a bridge rectifying AC to DC, about which I were not quite sure, though.
I’ve read about them being used for switching, but this light is just wired to a simple on/off switch.
What would be their purposes in a 12V DC circuit?
Thank you.

 

[rjenkinsgb]

Probably a bridge rec so it works regardless of the input power polarity. A lot of LED lamps & LED filament bulb replacements have that.

It avoids the problem of it not working due to the positive and negative being reversed.

 

[Diver300]

As well as making the lamp that it doesn't mind the polarity, it could also be to allow for AC supplies if the light is run from an alternator that produces AC.

It may not be done any more, but some lighting driven from small engines, like pull-start outboards, lawnmowers and kick-start motorbikes is driven directly from the alternator coils on AC. It's still common on the generators on bicycles, so the LED bike lights designed to run from them will have the bridge rectifier, even though some will be run from battery packs.

The empty capacitor pad may show that the manufacturers don't think it's needed any more. You may get some flicker with AC if the capacitor is missing.

It's certainly better for the manufacturer of the light include the diodes than to require the customer to wire the light one way, or to have really bad light flicker when connected to an AC supply.