One of my regular blog readers submitted an LED globe for post-mortem analysis, having failed well before the expected lifetime. I take a look inside, determine the configuration and analyze the relatively "anonymous" product which seems to show several design shortcomings which I discuss and think might be relevant to other readers at the element14 community.

 

The article is posted at http://goughlui.com/2016/06/01/failed-click-ltmr5w3k-5w-led-mr16-replacement-globe/

 

What really gets me is that many products are still designed using multiple-parallel LEDs without any current balancing mechanisms (e.g. remember emitter feedback resistors when paralleling BJTs?) and that leads to potential for a single string to be overstressed continually, fail early, and begin the cascade of failure as other LEDs are forced to soak up current in excess of their ratings, and operate in less efficient regimes resulting in greater heat production and degradation of the semiconductor material. Of course, if you went all-series, you would have an all or nothing situation and require higher voltage driver electronics, but I personally would gravitate to this arrangement for reliability reasons, or go with multiple independent channels if reliability is demanded.

 

Any comments, or stories related to LED globes or LED light designs are very much welcome.

 

- Gough