LED lighting panels

**Doddy** · 20-01-2021

14 parallel LEDs? without independent current limiting resistors?, that's a crap design - the drive circuit will - as you say - be designed to drive the power of each LED, but any variance (and they'll be plenty) in the characteristics (forward-volt drop) will see that particular LED consume more power and fail sooner - and, as identified - that results in a cascade of subsequent LED failures.

Designed to fail.

**Kitwn** · 21-01-2021

Originally Posted by Doddy

14 parallel LEDs? without independent current limiting resistors?, that's a crap design - the drive circuit will - as you say - be designed to drive the power of each LED, but any variance (and they'll be plenty) in the characteristics (forward-volt drop) will see that particular LED consume more power and fail sooner - and, as identified - that results in a cascade of subsequent LED failures.

Designed to fail.

And somebody will have been paid to design that!

In practice LEDs are best supplied with a constant current supply rather than constant voltage as the forward voltage of the devices is very temperature dependant. I think most commercial units have a simple chopped AC drive circuit which is unidirectional but pulsed. A propper constant current DC supply will give a stable light output and greater reliability. You can also dim them very easily over a wide range. I designed and made a set of hight stability, dimmable LED stage lights for my former animation studio a few years back. The drive circuit isn't expensive to build and is fed from a standard Chinese switch-mode PSU. I can probably find (or redraw) the circuit if anyone is interested.

**A_Camera** · 19-02-2021

Originally Posted by Kitwn

And somebody will have been paid to design that!

...probably not a lot...

Also, some times management's decision can not be overruled by an engineer's recommendation. Especially not in those cheap labour countries. So maybe it's not the designer's fault but the management taking stupid decisions without enough knowledge about the subject.

**Kitwn** · 19-02-2021

Originally Posted by A_Camera

...probably not a lot...

Also, some times management's decision can not be overruled by an engineer's recommendation. Especially not in those cheap labour countries. So maybe it's not the designer's fault but the management taking stupid decisions without enough knowledge about the subject.

Putt's Law comes to mind here...

"Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand."