Author Topic: Explain to me the (de?)-evolution of LED lightbulb technology  (Read 7716 times)

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Offline TimNJTopic starter

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Greetings,

In 2014, I bought some Cree LED bulbs, some of the first mainstream varieties available. Not cheap - I think they were at least $10-15/bulb, at the time. I still have one circa-2014 100W equivalent Cree I use every day in my desk lamp. Anecdotally at least, they seem reliable.

The construction of the early bulbs tended to be quite exotic - Fancy cast aluminum pieces, fancy connectors, and so on. Obviously, it was a technology in its infancy.

From an electronics perspective, these bulbs had (relatively) complex driver boards with some sort of switch-mode driver. Board was usually crammed with big inductor, one or more electrolytic caps, an MOV, fusing, EMI filter, switching MOSFET -- All the normal stuff you'd see an a power supply connected to mains.

Fast forwarding a few years, the market has reached equilibrium, seemingly at the absolute lowest cost implementation possible. These days, seems most bulbs have some simple capacitive dropper or some all-in-one current regulator IC.

How did we get here? Why is it "acceptable" or "reasonable" now to go for these super cheap implementations but 6-7 years ago we needed to cram a full-blown AC-DC power supply in the base of a bulb? Have the LED chips improved? COB style LEDs?

In my experience, the newer bulbs have poor reliability, but I can't tell if that's a result of their overall design topology or if they are just built like crap. Or both.

Anyone able to summarize what happened over the last few years?

Thanks.
 

Offline NiHaoMike

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #1 on: March 23, 2021, 03:19:48 am »
In my experience, the newer bulbs have poor reliability, but I can't tell if that's a result of their overall design topology or if they are just built like crap. Or both.
Mostly just pushing the components harder to reduce cost, if you derate the power by dimming them or modifying them, they'll last a very long time.
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Offline sleemanj

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #2 on: March 23, 2021, 04:03:47 am »
Your cree bulb has not failed.  Manufacturers want things that will fail so they can sell you another one. 

Bonus is that making them as cheap as possible...

  1. means they can sell more
  2. means they make more profit
  3. means they fail earlier
  4. goto 1

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Offline james_s

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #3 on: March 23, 2021, 04:43:27 am »
The natural evolution has been greatly reducing the cost. This has resulted in approximately a 50% reduction in rated lifespan but has also nearly doubled the efficiency since the early Philips and Cree bulbs I bought. The modern LEDs are much more efficient which allows them to be driven at lower current. This reduces the complexity of the cooling required as well as simplifies the driver. Highly integrated driver ICs have resulted in simpler drivers with lower parts count.

So far I can't really complain, even 15,000 hours is a long time, and some of the early 30k-50k rated bulbs have not lasted as long as they were supposed to. For a long time I had almost no failures but recently two of the Philips bulbs in my bathroom had gotten substantially dimmer, a teardown revealed the LEDs themselves had deteriorated. I had a couple of the larger 800 lumen Philips bulbs fail too, those had drivers fail, the LEDs look fine.
 

Offline Berni

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #4 on: March 23, 2021, 07:39:53 am »
This is just the typical race to the bottom that happens once a technology becomes popular.

At the start when LED lighting was new technology people found it normal to be more expensive, but they bought it anyway because its shiny new tech, perhaps they bought it mostly for that reason, not because the light bulb was actually that much more superior to what they already had. Most people didn't bother but those that did care ware prepared to pay good money for it. Most new technology starts off like this.

But then as LED lighting gains popularity, the bulbs become ever more efficient more, the word gets around about how good they are...etc and more people become interested in this newfangled LED stuff. But they bought the bulb because of how much power this fancy new light is going to save them. But if they care about buying this bulb to save money they will buy the cheapest bulb they have at the store, they wont care about CRI or efficiency or lifespan. The end result is cheep bulbs sell better, so the competition will make an even cheaper bulb, the next competition will make an even cheaper bulb than that. Before you know it you will find two similarly looking 15W LED bulbs on the store shelf, one of them costing $2.99 while the other name brand costs $15, this makes the high quality expensive bulb seam even more overpriced, making them sell even worse. Eventually they just stop making these high quality bulbs because they just don't sell.

This happens with most areas. Once market volumes become large enough the cheep low quality products come in and displace the expensive high quality stuff. Its a sad reality. :(
 

Offline james_s

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #5 on: March 23, 2021, 08:00:47 am »
But in this case the "cheap low quality" bulbs are in many cases perfectly adequate and actually perform much better than the early expensive bulbs. The early bulbs were complex and expensive because at the time they were struggling to get 800 lumens out of something the same size and shape as the standard 60W incandescent bulb they were trying to replace. It was a big challenge to drive the LEDs sufficiently hard and get rid of the heat they generated in order to achieve reasonable life. An additional challenge is that CFLs had gained a reputation of not lasting anywhere near as long as claimed lifespan so the LED makers knew they had to over-engineer the early bulbs because if $50 light bulbs started crapping out long before they were supposed to that would have killed the market and they would never have achieved the volume necessary to drop the price.

The bulbs we have now may be much more cheaply made and much simpler, but that means they are affordable so they have achieved widespread adoption. Gains in efficiency have eliminated the need for the complex and expensive cooling solutions, reduced the resources required to manufacture the lamps, and in the process they have become much more efficient, deliver better quality light and still last a very long time. At this point I have retired most of my early LED bulbs, not because they have worn out, but because the modern cheap ones offer dramatically improved performance in most applications, and so far despite having a much cheaper feel, they have not proven to be any less reliable. Changing burned out light bulbs is largely a thing of the past.
« Last Edit: March 23, 2021, 05:03:31 pm by james_s »
 

Offline tszaboo

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #6 on: March 23, 2021, 08:51:02 am »
Well, the thing is, I can go to IKEA, and buy a LED lamp for 1 EUR. 470 Lumen. Sometimes half the price of this. And it works.

They also sell a bigger one, that is 1000 Lumen, you can change the color temperature, wirelessly dimmable, and has 11W rating, and it is surprisingly heavy, with polycarbonate housing.

They also sell LED panels, with separate drivers, 34W, you can change the color temperature, wirelessly dimmable, about 7kg.

I placed the first one in the garage, the second one in the bedroom, the third in the office. I dont think the quality decreased during the years. I think there is a larger variety to choose from. And it needs to be, because incandescent is obsolete and they don't sell it anymore.
 

Offline TimNJTopic starter

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #7 on: March 23, 2021, 12:36:51 pm »
Thanks everyone. I understand the basic economics of it. Of course, the market equilibrium point gravitates towards lower cost.

But in this case the "cheap low quality" bulbs are in many cases perfectly adequate and actually perform much better than the early expensive bulbs. The early bulbs were complex and expensive because at the time they were struggling to get 800 lumens out of something the same size and shape as the standard 60W incandescent bulb they were trying to replace. It was a big challenge to drive the LEDs sufficiently hard and get rid of the heat they generated in order to achieve reasonable life. An additional challenge is that CFLs had gained a reputation of not lasting anywhere near as long as claimed lifespan so the LED makers knew they had to over-engineer the early bulbs because if $50 light bulbs started crapping out long before they were supposed to that would have killed the market and they would never have achieved the volume necessary to drop the price.

The bulbs we have now may be much more cheaply made and much simpler, but that means they are affordable so they have achieved widespread adoption. Gains in efficiency have eliminated the need for the complex and expensive cooling solutions, reduced the resources required to manufacture the lamps, and in the process they have become much more efficient, deliver better quality life and still last a very long time. At this point I have retired most of my early LED bulbs, not because they have worn out, but because the modern cheap ones offer dramatically improved performance in most applications, and so far despite having a much cheaper feel, they have not proven to be any less reliable. Changing burned out light bulbs is largely a thing of the past.

Well, my experience is only anecdotal, but my experience with modern bulbs is a mixed bag. I've had a few go flaky on me, and a few outright fail. I understand that the simpler solutions are often the most reliable, as there is less to go wrong. But, I know I'm not the only person reporting early failures of modern bulbs labeled as "20,000+ hours".

But, my suspicion is that the "topologies" used in modern bulbs are acceptable, but perhaps the parts are just underspecified and/or the quality control is poor on some of the cheap bulbs.

My main point of curiosity is in understanding *what changed* between 2014 and now. What has gotten more efficient? The LEDs themselves? Why did the drive electronics go from complicated (50+ parts on the BOM) to completely minimalist (maybe 3-5 parts on the driver BOM). Did the ICs not exist yet?

Thanks.
 

Offline Tomorokoshi

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #8 on: March 23, 2021, 01:45:22 pm »
On average my LED bulbs fail at maybe half the rate of incandescent or CFL A19-base bulbs. However, some packs burn out quickly while others seem to work. My voltage is around 124. I have a small collection of LED and CFL bulbs that I will eventually disassemble to find out what components failed.

I just bought a couple Philips T12 F40 LED direct replacements. Nice color, no flicker, instant on. I will get more and try them out. They were maybe $7 each compared to $5 each for classic fluorescent.
 

Offline madires

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #9 on: March 23, 2021, 01:57:20 pm »
I took a few apart which failed early because I was curious about the reason. The common issues are poor thermal design and cheap electrolytic caps.
 

Offline MK14

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #10 on: March 23, 2021, 02:04:04 pm »
My understanding is that one single country, has introduced a law, so that the only Led bulbs allowed, are extremely long life (I'm NOT sure of the exact rules/law, so this could be WRONG), super efficient ones. So, seeing an opportunity, the manufacture(s) have produced such Led bulbs. But ONLY allow them to be sold in that particular country.

BigClive found out about this, managed to obtain such Led bulbs and has done teardowns, reverse engineered schematics and measurements of 'our' Led bulbs vs those much better ones.
I suspect, they don't even cost that much more to produce, so hopefully sell for reasonable prices.

Essentially, they seem to have just doubled (or even tripled/quadrupled or more) the number of Leds, halved/quartered (approx) the current, and presumably/hopefully under-stress/underrate the power components, so that they can last perhaps 35,000 .. 50,000+ hours, at a guess.

« Last Edit: March 23, 2021, 02:14:20 pm by MK14 »
 
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Offline madires

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #11 on: March 23, 2021, 02:20:30 pm »
Yep, those Dubai LED lamps are designed well. It's a pity we can't buy them easily outside of Dubai.
 

Offline coppice

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #12 on: March 23, 2021, 02:28:06 pm »
People like compact lights, and lights that fit into traditional sockets. That usually means some parts are being roasted, especially if the lamp is used inside an enclosed luminaire. Its not the electrical stresses that kill the current cheap LEDs. Its mostly the thermal stresses.
 

Offline TimNJTopic starter

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #13 on: March 23, 2021, 02:46:40 pm »
I love the filament bulbs, just wondering how we get away with a tiny 6x12mm or 8x12mm electrolytic cap in the base + some dinky looking diode bridge, while 5 years ago, the average LED light bulb had some monster 10x16mm cap, inductors, MOSFETs, all sorts of control stuff. We just don't need it anymore? Much better integration with new control ICs? In the early days companies were taking a much more old skool approach to doing constant current driver from mains?

I've seen (I think electronupdate) do a filament bulb life test and they seem just as capable of lasting a long time, all things considered. I'm mainly just wondering where the heck all the control and power conversion circuitry went.
 

Offline Sal Ammoniac

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #14 on: March 23, 2021, 03:45:46 pm »
I wonder if this race to the bottom price-wise results in LED bulbs that generate lots of RF noise? I wouldn't be surprised at all if it did.

So now we have a product that generates two kinds of pollution: RF pollution and light pollution.
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Offline TimNJTopic starter

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #15 on: March 23, 2021, 04:43:59 pm »
Here's an example of an circa-2013 LED bulb:


Here's a slightly newer construction (circa 2016), less parts, but still generally high level of complexity:



Now, LED bulb might just have a simple capacitive dropper like this one. Remind me what the downsides of these are again? Power power factor for one.



Or some highly integrated constant current driver like this. But, as far as I know, these are linear constant current drivers, i.e. MOSFET/BJT operated in ohmic region to maintain constant current? Is it that LED efficiency has improved so much that burning a little power in the driver is less of an issue since the lumens per watt is better than it was before?

 

Offline TimNJTopic starter

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #16 on: March 23, 2021, 04:47:00 pm »
And, adding the above point about linear constant current regulator. If it's effectively a linear regulator, then there's no real need (or less of a need) for EMI filter since there's likely no high frequency switching activity.
 

Offline james_s

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #17 on: March 23, 2021, 05:08:48 pm »
My main point of curiosity is in understanding *what changed* between 2014 and now. What has gotten more efficient? The LEDs themselves? Why did the drive electronics go from complicated (50+ parts on the BOM) to completely minimalist (maybe 3-5 parts on the driver BOM). Did the ICs not exist yet?

The LEDs themselves mostly, they have gotten much more efficient. This enables them to be driven at much lower current, which simplifies everything else. The efficiency of an LED drops pretty dramatically as you crank up the current and the early ones had to be driven hard to get enough light out of them. This meant a mechanically complex design to deal with all the heat since almost none is radiated along with the light as with incandescent, instead it all ends up in the die itself. Then there are many new ICs that didn't exist before, and due to the lower power requirements enabled by newer more efficient LEDs the drive circuits can be simpler as everything runs at lower current.
 
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Offline james_s

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #18 on: March 23, 2021, 05:14:52 pm »
I love the filament bulbs, just wondering how we get away with a tiny 6x12mm or 8x12mm electrolytic cap in the base + some dinky looking diode bridge, while 5 years ago, the average LED light bulb had some monster 10x16mm cap, inductors, MOSFETs, all sorts of control stuff. We just don't need it anymore? Much better integration with new control ICs? In the early days companies were taking a much more old skool approach to doing constant current driver from mains?

I've seen (I think electronupdate) do a filament bulb life test and they seem just as capable of lasting a long time, all things considered. I'm mainly just wondering where the heck all the control and power conversion circuitry went.

The filament bulbs have dozens of LED dies in series and drop close to the full line voltage across the LEDs at very low current, this makes it reasonable to use a simple linear regulator IC without crazy high losses. Compare this to an early bulb with perhaps 6-8 LEDs with a total forward drop of 30-40V being driven at 300-700mA, naturally it's going to require a more complex driver with bigger capacitors. A significant downside of many of the simpler bulbs though is that they flicker at line frequency, I find the flicker annoying and avoid those.
 

Offline coppice

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #19 on: March 23, 2021, 05:15:24 pm »
The LEDs themselves mostly, they have gotten much more efficient.
They are not just more efficient. In 2014 Cree and one or two others had solved the problem of rapid ageing, while most makes were far dimmer after a few thousand hours. Now it seems most LEDs fade very slowly.
 
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Offline BrokenYugo

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #20 on: March 23, 2021, 05:46:20 pm »
I wonder if this race to the bottom price-wise results in LED bulbs that generate lots of RF noise? I wouldn't be surprised at all if it did.

So now we have a product that generates two kinds of pollution: RF pollution and light pollution.

The super cheap non dimmable ones, at least in 120V land, seem to have gravitated towards a linear driver setup. Those are silent to the best of my testing ability (holding a AM transistor radio near a 100W one I got from the dollar store).

I wouldn't doubt it if the more complex dimmable and smart bulbs with buck converters and radios of their own make all sorts of noise though.
 
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Offline ogden

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #21 on: March 23, 2021, 06:06:53 pm »
Anyone able to summarize what happened over the last few years?

Customers who buy cheapest (***t) they can get - happened. It does not mean that quality products do no exist anymore. Such are simply out of scope for generic buyers who check only nearby grocery store or lowest cost Amazon/Aliexpress offers.
 

Offline TimNJTopic starter

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #22 on: March 23, 2021, 06:49:04 pm »
Anyone able to summarize what happened over the last few years?

Customers who buy cheapest (***t) they can get - happened. It does not mean that quality products do no exist anymore. Such are simply out of scope for generic buyers who check only nearby grocery store or lowest cost Amazon/Aliexpress offers.

While part of my question was indeed about the (possible) decline in quality, due to a "maturing" market -- and capitalism being capatalism and cheap-asses being cheap-asses -- really I was just wondering what explains the overall shift in design approach. I think the few replies above neatly explain it.  But, I do agree, part of it is consumers un-willingness to pay a premium for something that actually lasts (no shock there) and manufacturers willing to make crap in response.

But, to my main point, here's my summary of the above responses:

Earlier LEDs required much more current for X amount of lumens. So, you probably couldn't just throw in one of these (modern) linear constant current drivers because the driver dissipation would probably be way too much. I don't have any ballpark figures to compare then vs. now, but makes sense. So, they went for switch-mode constant current driver with relatively high driver efficiency. Nowadays, larger number of LEDs in series + much improved efficiency means the forward current can be much lower, making a linear constant current driver practical.
 
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Offline andy2000

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #23 on: March 23, 2021, 08:19:16 pm »
I wonder if this race to the bottom price-wise results in LED bulbs that generate lots of RF noise? I wouldn't be surprised at all if it did.

So now we have a product that generates two kinds of pollution: RF pollution and light pollution.

I recently bought some new LEDs to replace some early ones that were starting to fail.  Coincidentally, around the same time I noticed a lot of interference on a vintage analog TV in the next room that gets used to watch the news.  There were very noticeable wide horizontal noise bars moving up the picture.  It turned out that the new bulbs were causing the interference.  The set is fed using a shielded coaxial line, so I was surprised so much noise was leaking in.  With the coax unplugged, the usual snow was completely obscured by the interference.

Out of curiosity, I used my spectrum analyzer to look at the interference.  This was with just an dangling probe as an antenna.  You can see the FM band on the left side, and a couple of ATSC TV channels on the right.  The bulbs were generating interference over the entire spectrum up to about 500 MHz.  Needless to say, they went back to the store.  The old bulbs generated no visible interference. 
 
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Offline Tomorokoshi

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Re: Explain to me the (de?)-evolution of LED lightbulb technology
« Reply #24 on: March 23, 2021, 08:39:06 pm »
I wonder if this race to the bottom price-wise results in LED bulbs that generate lots of RF noise? I wouldn't be surprised at all if it did.

So now we have a product that generates two kinds of pollution: RF pollution and light pollution.

I recently bought some new LEDs to replace some early ones that were starting to fail.  Coincidentally, around the same time I noticed a lot of interference on a vintage analog TV in the next room that gets used to watch the news.  There were very noticeable wide horizontal noise bars moving up the picture.  It turned out that the new bulbs were causing the interference.  The set is fed using a shielded coaxial line, so I was surprised so much noise was leaking in.  With the coax unplugged, the usual snow was completely obscured by the interference.

Out of curiosity, I used my spectrum analyzer to look at the interference.  This was with just an dangling probe as an antenna.  You can see the FM band on the left side, and a couple of ATSC TV channels on the right.  The bulbs were generating interference over the entire spectrum up to about 500 MHz.  Needless to say, they went back to the store.  The old bulbs generated no visible interference.

Feit. I could have guessed that. Those fail the quickest for me.
 


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