Capacitors: a Case Study in LED Light Bulbs

**redwire** · 06-20-2013, 04:56 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Low cost, high brightness, long life - pick any two, that's the (triangle) rule for product development. You can't have it all :}
I find it's just getting rid of the LED's heat - at 10-20W you need heatsinks and airflow, or else you cook the electronics, which Cree seems to be pushing.
Too bad they didn't use a chunk of finned aluminum.

**cheapie** · 06-20-2013, 08:44 PM

Re: Capacitors: a Case Study in LED Light Bulbs

I just tore apart a 12W (60W equiv.) omnidirectional Greenlite LED bulb (bought for US$10.99 at a grocery store). I discovered that it uses 24 SMD LEDs running at 94VDC. Unfortunately, the power supply portion was potted. The UL number on the LED board traces to "Shung Ching Electronic Technology Co." which appears to just be a PCB manufacturer.

**retiredcaps** · 06-21-2013, 12:37 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by cheapie

I just tore apart a 12W (60W equiv.) omnidirectional Greenlite LED bulb (bought for US$10.99 at a grocery store).

Pictures?

**cheapie** · 06-21-2013, 08:27 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by retiredcaps

Pictures?

Unfortunately, I can't upload anything while the Internet connection is throttled. I'll post them tonight if I remember.

**cheapie** · 06-22-2013, 12:28 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by cheapie

Unfortunately, I can't upload anything while the Internet connection is throttled. I'll post them tonight if I remember.

Here they are. The pictures are:

-The bulb before I disassembled it
-The top of the bulb removed
-The LED board (I wonder why one of the LEDs has a dark spot. This bulb was still working before I took it apart)
-The bulb clamped in a vise, attempting to open it further
-The base of the bulb, showing the visible portion of the power supply.

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**budm** · 06-26-2013, 10:03 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Here is another tear down of LED lamp.
http://www.eetimes.com/design/smart-...r?pageNumber=0

**retiredcaps** · 06-26-2013, 06:35 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by budm

Here is another tear down of LED lamp.
http://www.eetimes.com/design/smart-...r?pageNumber=0

The caps in those pictures are teal Rubycon RX series rated to 130C. Those might have a chance to survive long term in the heat.

**japlytic** · 06-29-2013, 04:22 AM

Re: Capacitors: a Case Study in LED Light Bulbs

I am amazed that the only electrolytic capacitor in the regulator for LED lamps is on the output to the LED array - no 200/250/400/450V electrolytics there!

**ben7** · 06-29-2013, 04:53 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by japlytic

I am amazed that the only electrolytic capacitor in the regulator for LED lamps is on the output to the LED array - no 200/250/400/450V electrolytics there!

Yeah. I think the control chips usually have some sort of "pfc". Not regular pfc, they just follow the sine wave. It's nice, no big high voltage capacitors, leaving more room for the other electronics.

**cheapie** · 06-29-2013, 09:05 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by ben7

Yeah. I think the control chips usually have some sort of "pfc". Not regular pfc, they just follow the sine wave. It's nice, no big high voltage capacitors, leaving more room for the other electronics.

It does mean that you get 120Hz flicker (100Hz in more sane countries) though.

**kaboom** · 07-03-2013, 08:49 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by cheapie

I wonder why one of the LEDs has a dark spot

Too much current! This will be the common problem with the cheep, upcoming Light Emitting Decorations. It was, and still is, a problem with those nasty harbor freight LED "flashlites." Multiple LEDs, either overdriven and/or with no current limiting, other than the batteries. After just a few weeks, you have DEDs- dark emitting diodes...

Ben7- some of your "corn bulbs" used to use a simple capacitive dropper power supply. Just an X cap, a few 1N4004/7s, and a zener. As LED light power supplies, they have terrible ripple, most of the time there are no large electros.

The nicer ones have a proper buck converter, even fed by a proper PFC- just like a computer/monitor power supply!

Ah yes, LED "lights." Where CRI doesn't even matter! Because there isn't any...
http://en.wikipedia.org/wiki/Color_rendering_index

"White" LEDs are disgusting- mostly blue, with a yellow phosphor. Guess what happens to that phosphor when the LED is over driven?

I cannot tell red resistor color bands from the green ones with a 1W LED flashlight. I can under PSMH, halogen, and even good T12s! 800/825 T8s and T5s are even nicer.

Yes, even common PSMH lamps blow those cheap LEDs outta da water, and then some. The only LEDs to ever be taken seriously for lighting are the Crees.

**eccerr0r** · 07-03-2013, 09:33 PM

Re: Capacitors: a Case Study in LED Light Bulbs

There are those "corn" bulbs with multiple sub-watt diodes, and there are the high intensity watt+ LED bulbs, anyone prefer one or the other?
I suspect the "corn" bulbs are easier to cool because the diodes are spread apart and you don't have hot spots, but the high intensity LEDs are smaller...except they need larger, heavier heatsinks...

**budm** · 07-03-2013, 11:10 PM

Re: Capacitors: a Case Study in LED Light Bulbs

I bought two packs of these LED lamps from Costco last year when they were on sale for $12 for 3-lamp package. I use them for my desk lamp and front porch lamp, it has warm white, the color of the lights are really good, it is labeled as 'warm white'.
So far so good, I have been using them since 3/2012.

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**ben7** · 07-04-2013, 06:30 AM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by kaboom

Too much current! This will be the common problem with the cheep, upcoming Light Emitting Decorations. It was, and still is, a problem with those nasty harbor freight LED "flashlites." Multiple LEDs, either overdriven and/or with no current limiting, other than the batteries. After just a few weeks, you have DEDs- dark emitting diodes...

Ben7- some of your "corn bulbs" used to use a simple capacitive dropper power supply. Just an X cap, a few 1N4004/7s, and a zener. As LED light power supplies, they have terrible ripple, most of the time there are no large electros.

The nicer ones have a proper buck converter, even fed by a proper PFC- just like a computer/monitor power supply!

Ah yes, LED "lights." Where CRI doesn't even matter! Because there isn't any...
http://en.wikipedia.org/wiki/Color_rendering_index

"White" LEDs are disgusting- mostly blue, with a yellow phosphor. Guess what happens to that phosphor when the LED is over driven?

I cannot tell red resistor color bands from the green ones with a 1W LED flashlight. I can under PSMH, halogen, and even good T12s! 800/825 T8s and T5s are even nicer.

Yes, even common PSMH lamps blow those cheap LEDs outta da water, and then some. The only LEDs to ever be taken seriously for lighting are the Crees.

I've never had problems with the CRI of LEDs. Of course, I have young eyes, that may be why.

That is the way white LEDs work. They are actually a blue LED, which then has white phosphors inside.

LEDs dont really care about ripple. One way to make them brighter is to pulse the current through them. These current pulses can be many times the average current rating, but it is only acceptable if the total average current does not exceed it's ratings. Your eyes and persistence of vision do the rest!

**kaboom** · 07-05-2013, 10:04 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by ben7

I've never had problems with the CRI of LEDs. Of course, I have young eyes, that may be why.

That is the way white LEDs work. They are actually a blue LED, which then has white phosphors inside.

They can be yellow or white:

http://www.mt-berlin.com/frames_crys..._phosphors.htm

I've seen newer LED spots that I honestly thought were halogen. I have no idea who made them, as they were in fixtures in a store display. A place called Country Junction to be exact. No flicker, excellent CRI. Not sure about color temp, probably 3000-3200k.

It wouldn't be hard to use those "premium" phosphors to provide excellent light quality. You'd have the LED equivalent of those 800/825/850 T5 and T8 fluorescent tubes!

**BigTroll** · 06-02-2014, 01:34 PM

Re: Capacitors: a Case Study in LED Light Bulbs

I really love my cree bulbs I got the daylight 5000k throughout my house now, the 60w equivalent variety, I notice i can see more crisp detail with 5000k plus they seem to keep me more awake and focused.

**RJARRRPCGP** · 06-02-2014, 01:59 PM

Re: Capacitors: a Case Study in LED Light Bulbs

In 2010, I experimented with tiny Feit CFLs and 1 failed right off the bat! (Failed quietly, just dimmed and went out. )
(Right after turning it on for the first time, didn't even last 1 minute!)

(You would think that even a 1920s incandescent light bulb would do a lot better!)

I rather have a T12 or a T8 any day!

**stj** · 06-02-2014, 03:19 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by RJARRRPCGP

In 2010, I experimented with tiny Feit CFLs and 1 failed right off the bat! (Failed quietly, just dimmed and went out. )
(Right after turning it on for the first time, didn't even last 1 minute!)

(You would think that even a 1920s incandescent light bulb would do a lot better!)

I rather have a T12 or a T8 any day!

bulbs in the 1920's probably cost a fortune,
incans now can be real crap.

i had some "shop-brand" tradesman crap that out of a 10pack,
2 pinged in under a minute and one exploded and dumped glass all over the stairs.
it would be the one that needed a fucking ladder!!!
i had hell trying to get the base out of the fitting!

**RJARRRPCGP** · 06-02-2014, 03:25 PM

Re: Capacitors: a Case Study in LED Light Bulbs

Originally posted by stj

bulbs in the 1920's probably cost a fortune,
incans now can be real crap.

Back then there reportedly was a light bulb cartel that made the light bulbs lucky to last 7 months! Only rated at 1,000 hours!

http://en.wikipedia.org/wiki/Phoebus_cartel

I would be lucky to get 4 months for a plant light at that time!

The Bell of light bulbs!

**ben7** · 06-02-2014, 04:31 PM

Re: Capacitors: a Case Study in LED Light Bulbs

I've said this on here before (not sure if it was earlier in this thread or not ... :P) but I had a recent experience with a crappy bulb. I needed a new bulb for my reading light, so I got a pack of two, 25W GE bulbs. The kind with the small candelabra base, but the large spherical globe. The one I first put it sparked all of a sudden when I was screwing it in, the cause was the fact that the bulb's metal screw base was inadequately adhered to the glass - it broke loose, and the wires twisted together, shorting out... lol
The second one from that pack didn't do that, and I'd say it had a normal lifespan. (I've since replaced it, maybe a month or so ago..)

Capacitors: a Case Study in LED Light Bulbs

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