Which is better, series or parallel for COB LED?

What set up will minimize losses for better illuminance?thanks :)

I prefer series wiring for any kind of LED, because circuit elements wired in series share the same current. Thus every device in a series string is guaranteed to have the exact same current running through it, and I only need one current limiting device per series string of LEDs.

The fear I have concerning LEDs wired in parallel (recall circuit elements wired in parallel share the same voltage), is thermal runaway. That is to say, one of the LEDs is going to get warmer than the others, then get less resistive, then start hogging most of the current.

By the way, you might have noticed, on the COB, on the Chip-On-Board itself, they've got an array of LEDs wired in series and parallel, like the designer was not worried about thermal runaway. But I think the thing that makes that possible, is the fact that the LEDs on a COB are so physically close together they're guaranteed to be in thermal equilibrium with each other; i.e. they share the heat, and they're all very close to the same temperature.

But I think the thing that makes that possible, is the fact that the
LEDs on a COB are so physically close together they're guaranteed to be
in thermal equilibrium with each other.

And they are likely assembled from dies made of the same exact batch.

Yeah. The fact that all the LEDs on a COB are almost identical, have the same current-voltage-temperature behavior, I'm sure that helps too.

That depends on your power supply.

Parallel if it is your supply is minimum voltage with lots of current.

Series if your supply has lots of voltage but little current.

And both with some extra current and voltage.