[Big Clive] picked up some chip-on-board (COB) LEDs meant for hydroponics that were very unusual and set out to examine them on video. Despite damaging the board almost right away, he managed to do some testing on these arrays and you can see the results in the video below. He also compares it to older LED modules.
The 144 LEDs produce a lot of light. In addition to powering the device up, he also looks at the construction of the LEDs under a magnification, comparing the older style that used tiny bond wires to make connections versus the new version soldered on the board directly.
The right side of the board has an AC connection, a metal oxide varistor to prevent overvoltage, and a bridge rectifier. The other side contains an LED current sink circuit. [Clive] does a bit of math and decides that the LEDs are in an arrangement that lets you select if have clusters of LEDs to accept 220V input or 110V.
The devices in the current sink didn’t show up in an Internet search. [Clive] does a bit of probing and analysis to shed light on what’s happening in the circuit. There’s an IC, a Zener diode, and a beefy transistor.
Chip on board isn’t very new but it poses the same kind of problems for experimenters that surface mount once did. These appear to use the “flip” method where the boards have solder balls placed on them and rest on the inverted components as everything goes through an oven. In some cases, though, fine bond wires or ribbons are welded using a laser or ultrasonic methods in the same way that conventional ICs attach to their lead frames.