Philips LED bulb: Tear-down Part I (light patterns)

-February 14, 2011

Philips sent me one of their 12.5W dimmable LED bulbs to evaluate. (This is Philips L-Prize entry, for those following the DOE contest. WRONG, see below.) Tear-down time!

Some of you have mentioned that long posts with lots of pictures are too painful at slower download speeds, so I’m breaking this it into installments because it’s both lengthy and has lots of photos. Here’s a preview of the main points of this tear-down:

  • There is a variation in light patterns created by light bulbs, and manufacturers have found some creative solutions to mimic the near-360-degrees of an incandescent light.
  • Philips jumped through a lot of hoops minimize hand soldering in its new bulb.
  • A look at which IC vendor’s power management chip is in the bulb.

See how the 12.5W dimmable LED bulb's light patterns and dimming responses compare to incandescent, CFL, and LED bulbs in this video:

OK, first, some field-testing was in order, because that’s a pretty odd-looking light-bulb.


Granted, CFLs are *really* odd-looking…


…and “sno-cone” LEDs likewise are an acquired taste.


Come to think of it, the first Edison socket light bulbs were probably greeted with head-scratching by a public used to oil lamps and gas light.


My concern with the Philips bulb was what kind of light pattern did it produce? An incandescent bulb is a uniform, nearly global source of light. Intuitively, the sno-cone light will produce a semi-sphere of light, and the CFL – well, I didn’t really know how light was dispersed from a CFL. So my first test was to find a way of comparing the bulbs’ light patterns.


This is the home-made jig: It’s basically a slanted rim – a conical section of very light cardboard -  that encircles the light bulb, reflecting its light over the 360 degrees around the bulb. What were the results? Here’s the familiar global light distribution of the incandescent bulb:


The CFL had a fairly universal light distribution also, although slightly less than the incandescent.


The sno-cone LED light was less than half of a semispherical pattern, which you’d expect because the LEDs rest on a flat surface, pointing up with little to no secondary optics to direct the light to the sides or down.


Now take a look at the Philips light: Virtually the same as the incandescent light:


How does the Philips bulb create such a spherical light pattern? We’ll take a closer look at the bulb in the next part of this tear-down (which I hope to get posted later today.)

UPDATE:  Both Maury Wright and reader Navigator below in the comments point out that the L-Prize bulb is a different bulb. I checked with Philips and got this prompt reply: “The L Prize lamp that is in consideration is 900 lumens, less than 10 watts and is not commercially available as the DOE is still in the process of considering it.

The Philips EnduraLED is 806 lumens, 12.5 watts and currently commercially viable.  We took what we learned with the L Prize lamp to bring a viable 60 watt equivalent to market.”

Back to uploading photos for the next part…

Click here to read part II

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