Introduction

I recently ordered various LED home lighting from a UK supplier (theledspecialist.co.uk), and unfortunately one arrived smashed : ( They kindly sent a replacement very quickly, but before I threw out the damaged one, I couldn't resist a teardown : )

It is a 9.5W, 760 lumen LED bulb, warm white, with an Edison E27 fitting. It has a 25,000 hour life (longer than the usual 15,000 hour rating), intended for lobbies, walkways and so on according to the datasheet at the Philips Lighting website. As its name suggests, the beam is fairly tight (about 25 degrees overall). I'm using it in the workshop as some temporary lighting (it replaced a bulb that I needed elsewhere, and I was curious to find out what this new-ish model Philips bulb was like!).

Teardown

Opening the box, I saw the bulb was smashed : ( Rarely for an LED bulb, it actually has a lot of glass! Definitely not one to drop! Despite all the glass that front lens is plastic, and there are more detailed photos further below.

The glass body is extremely thick (about 4mm). I couldn't understand why there was so much glass used, but I'm wondering if it was needed for producing the inner mirror reflective surface, or for strength. Perhaps the inner surface is intended to reflect out heat as well as lots of light. The inner surface was extremely reflective, just like a first-surface optical mirror, but with the dimple pattern that you can see from the outside in the photo below (and in some of the fragments in photos further below). I get the feeling that the entire enclosure forms a large part of the cost of this lamp!

The front lens was quite interesting. I could not guess what plastic, it could be polycarbonate or something more exotic, since it needs to withstand heat and be highly transparent. But the part was stunning. It is extremely intricate.

Here's a side view. It looks like a fairly complex shape!

Inside the bulb, the LED was mounted on an metal-core PCB (MCPCB), held in place by a clip (removed for the photo below). The connecting wires appear to have a silicone-like insulation, and there is heat-proof sheathing around that too, where the cable passes through to the other side of the aluminium heatsink.

I could not identify the LED manufacturer, I'd initially assumed it was a Lumileds part, but it is not a shape that I could see in their online catalog. The heatsink is actually not that thick! Given the shape of it, and how it is attached at its sides to the glass, I'm wondering if the glass plays a role in the heat sinking too. The LED is clearly very efficient though, just from the sums - the bulb offers 760 lumens at 9.5W, so even at 85% efficiency from the driver, that's close to 95 lumens per watt, and it could be higher still. I'm tempted to do further measurements : ) but there are plenty other projects to do too

The circuitry was potted, but it didn't look overly crushed together; the E27 fitting shape has more than enough room for this circuit. It looks about the level of quality to be expected I think, not bad at all. There are a few inductors, and a MOSFET in an unusual package (i.e. small!) next to the yellow square inductor.

The underside contained more semiconductors. The main IC is iW3689 from Dialog Semiconductor (PDF brief datasheet).

The brief datasheet circuit looks similar to the implementation on the circuit board, although I didn't inspect closely.

Summary

I was quite impressed at the design of this LED bulb. It's definitely a more involved design than I would have expected! By the way its un-smashed sibling has a nice warm-white and powerful light output too, as expected.