Samsung LED light bulb teardown includes objective dimming numbers
Samsung sent me one of their new LED sno-cone-type bulbs to try out. The bulb specs are: 550 lumens at 10Wat a color temperature of 3000K, and comes with a 5-year warranty. Its list price is $19.98.
First off, how does the bulb perform?
Here’s a light pattern of the Samsung LED:
(To find out more about the light pattern ring, click here.)
For comparison’s sake, here’s the light pattern of an incandescent bulb:
As you can see, the Samsung’s bulb light projects predominantly upwards, as you’d expect from a sno-cone type bulb design.
Non-incandescent lights face a challenge when controlled by an old-style traic-based dimmer switch. In the past I’ve just put a bulb in a socket with a dimmer switch, put it through its paces, and have given a subjective thumbs-up/down. But this is not very gratifying, and it’s difficult to defend my results. What I needed was an objective way to measure dimming, and turn-on time, too, in the case of CFLs.
To do this dimming test I used a TAOS light sensor from Adafruit, controlled by an arduino development system. This allows an objective measurement of light dimming, and is such a useful tool that I will devote an entire blog post to it in the future.
Here’s a plot of the dimming characteristics of three different light bulb technologies — LED, CFL, and incandescent — with their dimming performance measured as a percentage of their highest light output, rather than with an absolute measure, say, in lux. Note that the L-Prize bulb competition uses a similar definition of dimming: “Must be continuously dimmable to at least 20% of maximum light output [italics added] …” So based on the output of the Taos light sensor, here’s what the dimming characteristics of the three bulbs are:
Notice that the incandescent bulb (yellow line) does not dim linearly with power. It’s main achievement is that it does dim down to zero. A CFL does a better job of dimming with power, and the Samsung LED light is very good, dimming quite linearly with power. However, it drops out at just under 20% of its max output light. (Which, however, more than meets the L-Prize spec.)
OK, so the Samsung bulb performs quite well. What’s inside the bulb? I took the plastic bulb cover off, using the Pete DiMaso method of baking the bulb in a 200°F oven for an hour before prying the cover off with a screw driver. (I have refined my technique so that I can get by with kitchen hot pads rather than leather gloves.)
There’s no marking on the LED but it’s probably a safe bet that it’s one of Samsung’s – Samsung made a big splash at the last LightFair that it was getting into the LED component business for lighting.
Lighting up the LED with the cover off, and then taking a photo through a welding mask allows you to see that the LED comprises six different die. Well. I think it does. I can definitely see two long rectangles of light, which I think are each made up of three smaller squares which are individual die. I forgot to measure the voltage across the LED at this point, which would have told me a lot about the die configuration. Oh well.
Going deeper into the guts of the light required its destruction…
It’s usually a treasure hunt to find out what power management IC is used in an LED bulb, and this one was no exception. See that white blog blob of goo just to the left of the yellow-wrapped transformer? I couldn’t find a likely-looking IC visible anywhere in the module, so by process of elimination it seemed it must be under the blog. Sure enough…
When I scraped off the white goo, the vertically mounted IC showed a Power Integrations logo and a LinkSwitch part number, I think LNK403EG.
My overall review of the bulb’s performance is that it does it’s job quite well, given that it’s a sno-cone configuration and therefore doesn’t have a spherical a light-throw as other LED lights. And, as evidenced by the graphical results above, its dimming performance is excellent.
patel commented:
Ms. Conner, nice job on the teardown and reporting it.
Did you happen to see a fuse on the AC line for short circuit protection? Or an MOV (varistor) for surge suppression? If not, what was used to meet UL and pass Energy Star?
Patel commented:
Did you see a fuse or an overcurrent protection device on the AC side? ALso, any surge suppression component such as an MOV (varistor)?
Nice job on the teardown.
enduser commented:
The problem I've had with "dimmable" CFL and LED lamps is they make a horrible buzzing sound at anything less than full power. This is a non-starter inside a home.
Steve Nordquist commented:
Anti-reflection PolyStyrene-ish dome surfaces? And venturi at the underside of the dome material in case it's installed base-up! Such oddly sealed dome/body profiles and oversymmetry (if you don't want dust in zone zero on the dome, base-down fixture allowing;) are people hosing down their sockets from now on? (Watch, it'll be Northern Ontario (NO) electrolytics; color me impressed if they're rated 85 degrees C.) I guess the automated PCB stuffer would be something to see in motion (perhaps the same line used to make Exploding Heart Kenhun and Barbjae Seasonal Condition Dolls,) too!
It would be cute© to get a little (cholingeric liquid crystal) circle graph on the base vetting whether day insolation, caps, LED temperature (self/otherwise), encapsulation, dome optics, MMO rage (...) or hosedown are most likely to render the thing EOL.
Neat job, Samsung, Margery. Now to see if it takes well to a stochastic dimmer (fluttering on purpose to emulate (partially) shaded sunlight.)
PaulM commented:
Really too expensive, and i shudder at the potential RF radiation "Fog" from the multiple convertor(s)blotting out Analogue
CEDUP commented:
So teh Philips lamps are more better? Better build, better distribution, and I got the Ambi LED for $14.95 at Home Depot a while ago. 12.2 W, superb color and high brightness, run 4 of em on a Cassablance light fixture hanging off the fan. Perfect, no issues. Philips beats em all. Philips non L-prize is cheaper and functions better.
Andy Smith commented:
I would like to offer a comment about the use of electrolytics in this design (Disclaimer: I work for PI)
Electrolytics are the most cost effective way to instantiate a lot of capacitance and Samsung’s price point is very aggressive – I suspect that they had no room in the budget for ceramics. Even so the design does not use a high voltage electrolytic bulk capacitor. This is the one circuit location that can cause significant life-shortening as a result of heat induced aging of electrolytics. So this driver will likely last a long time even with the other electrolytic capacitors present.
The LinkSwitch-PH can work with either cermaics or electrolytics – folks building super-high reliability lights would probably invest in the ceramic option that PI details in their DER-284 reference design
Cor commented:
@AJF: The datasheet further says that the circuit needs 100uF on the output, which is not a trivial thing without Electrolytics. See Figure 7 in the datasheet? This is their suggested Schematic of an Isolated, TRIAC Dimmable, High Power Factor, Universal Input, 14 W LED Driver.
I count exactly 5 Elco's in that schematic...
Maybe they thought of using SPA (Solid Polymer Aluminum) capacitors to avoid electrolytics?
AJF commented:
It is interesting that the LNK403EG data sheet says"Enables very long lifetime designs (no electrolytic capacitors)", yet I count what appears to be 5 electrolytics in the assembly photo.
Tom commented:
For those that doubt the like expectancy claims, save the box and receipt. Then when it fails return it for replacement. I find the CLFs usually don't last the expected life if you left them on 24hrs a day.
Arby commented:
Andy/idler, Wikipedia entry on English plural:
Dies is used as the plural for die in the sense of a mold; dice as the plural in the sense of a small random number generator. Dice is also the accepted plural form of die in the semiconductor industry.
AFAIK, die is never the plural of die.
Arby commented:
Andy/idler, From Wikipedia on English plural:
Dies is used as the plural for die in the sense of a mold; dice as the plural (and increasingly as the singular) in the sense of a small random number generator. Dice is also the accepted plural form of die in the semiconductor industry.
AFAIK, die is never the plural of die.
budm commented:
I doubt that this buld will last 5 years, none of my CFL's last more than two years so far.
I took apart failed CFL and found out that the Electrolytics (105c) caps failed, just like thousands of LCD TV and LCD monitors that I have been fixing for the last 10 years.
I also bought one LED bulb (9W) from COSTCO about a month ago to try out, I cannot even touch the heatsink, it gets very hot so Iknow that the caps inside the buld will not last. Check out badcaps.net or look at my photos of failed TV and monitors at photobucket, just look for budm.
Andy T commented:
For you grammar Nazis, plural of semiconductor "die" is either "die" or "dice", though "dice" is principally used as a verb.
The main thing in that circuit that "dies" is the electrolytics.
Consumer commented:
Good luck with reliability, as good as the weakest component. The CFL’s in my house which the box says can last for 7 years, die more often than good ol’ incandescent.
eng35 commented:
very nice work. Still pricy for my application. I will look forward to your reviews.
Bill commented:
I have about 10 lights that are a pain to change so if I could get a 100W type bulb for $50-60 I would consider it worthwhile. At 30,000 hours it would last 20 years for me.
Phil Hobbs commented:
So to get the equivalent of a 100-W tungsten lightbulb (1690 lumens), I need three of these, at 30 W and $60. That's a lot less compelling than the solid-state light enthusiasts would have us believe.
I suppose nobody reads anymore, so folks think something this dim is okay for a table lamp?
Cheers
Phil Hobbs
idler commented:
@arby
Isn't the plural of die in this context : "dice" ?
jim van damme commented:
My first job was replacing filter electrolytics in AC-DC tube radios to get rid of the hum. Perhaps my last job will be replacing electrolytics in light bulbs. BTW the IC is made by Power Integrations.
Cor commented:
@Slobodan, Why don't you buy one of these lights at Lowe's (which is the retail store where they are offered according to the linked article) and see for yourself? I can't determine from the pictures, but I expect that it will be 105 deg C at minimum.
@Bob, no need to keep Home Depot receipts around (because you can get it at Lowe's...)
I am slowly converting more lights from CFL to LED, but due to the fact that I mainly buy cheap Chinese lights, it is hit and miss. The usable bright lights often over-drive the LEDs and that, or a combination of heat and surges on the net voltage, kills many of them early. Some lights continue to perform well and I have already taken an interest to simply buying 3W LEDs and making my own.
@Margery, if you re-connect the two wires to the LED then you can fire up the light and measure the voltage (don't run it more than a few seconds as it will get hot if you do not re-assemble it onto the alu heatsink)
Bgai Bob commented:
Nice Job. I wonder whether they (Samsung) think the bulb will operate for 5 years or if they have decided some kind of duty cycle or orientation or external temperature environment. The complexity of LED and (I guess) CFL bulbs seems to be a primary failure mode: solder connection fails, etc. I really want to buy LED lights, but I can't imagine keeping Home Depot receipts around to get the warranty effects.
Tom O'Donnell commented:
Nice job and very interesting. I know what you meant on the "blog". Some people just love to criticize.
Larry M commented:
> Also, it's a white *blob* of glue.
Or maybe "glob". I wonder if Margery meant to type glob and had a finger check or a dyslexic moment.
Allen Schott commented:
I take from the photos that the lower casing is aluminum. Good packaging effort, and great forensic engineering.
warpten commented:
The plural form of die in this case is either dice OR dies.
Arby commented:
The plural form of "die" is "dies."
Also, it should be "blob of goo."
"Blog" is a web site where individuals
record their opinions (such as this one ;)
Arby commented:
The plural form of "die" is "dies."
Also, it's a white *blob* of glue.
"Blog" is a site where individuals
record opinions or thoughts (such
as this one ;)
Slobodan Radoicic commented:
Ms./Mrs. Conner, would you be so kind to tell me what is the working temperature (85C,105C or maybe even 125C) of the electrolytics capacitors used (I presume that they are the Samsung brand, of course)?
Chris commented:
nice job. thanks!
