GE Genura electrodeloss compact fluorescent lamp (CFL) teardown - Page 1
Forum section: electronics / projects

author: JohnG
author_rank: Frequent Contributor
timestamp: November 08, 2020, 07:48:59 pm
content: Here is a little bit of lighting history. When it had become clear that incandescent lighting had past its peak, there was a brief period where consumers would pay extra for long-lasting, efficient lamps. Efficient LEDs were an expensive lab curiousity, especially white ones. A lot of money was invested in compact fluorescent lamp technology, which integrated a small electronic ballast with a small fluorescent lamp.Fluorescent lamps are complicated beasts from an electrical point of view. There is plasma plasma physics, chemistry, mercury, highish voltages, strong aging effects, etc. It is highly non-linear and has large negative incremental resistance, and so the lamps generally cannot be driven directly from a voltage source, at least, not for very long. This probelm was originally solved with a "ballast", usually a series inductor that would present an impedance larger than the negative impedance of the lamp, so that the net impedance was postive. That would limit the current and prevent it from running away. An inductor was used becuase it had much lower loss than a resistor, but at 50 or 60 Hz, you can imagine these inductors were large.There were other issues as well, such as needing a high voltage (several hundred) to strike the arc that would ionize the plasma and allow the lamp to start operating, and other circuits helped this happen.With the advent of modern power electronics, it became possible to build a high frequency power source in a small space, and the high frequency meant that you could shrink the ballast inductor.One of the main factors limiting the lamp life was electrode wear. The arc would eat away at the electrodes, which would darken the glass and poison the gas mix, and eventually the lamp would fail. This led to a brief period where manufacturers tried to develop electrodeless lamps that would induce a current in the plasma via a magnetic field, eliminating the need for electrodes. The GE Genura was one such lamp. I had a couple of these, and my last one failed after about 11 years of near daily use. I thought it would be interesting to look inside:Here's the lamp:If we tear open just a bit, we see the actual lamp and part of what is a shorted copper ring that is spaced just a bit from the lamp and does not connect to anything electrical. This is almost certainly a shorted turn to reduce EMI.Removing more of the case allows us to separate the lamp from the ballast. The lamp is completely seal, and has no electrical connection through the glass. You can see that there is a coil that protrudes into a pocket in the lamp itself. This is what forms a transformer primary, with the secondary being a conductive ring of plasma in the lamp. This plasma generates the UV that lights up the lamp phosphor. A silver conductive coating on the outside of the lamp is probably part shielding, and maybe it helps shape the plasma torus that forms inside the lamp. Note the slits in the coating so that it does not for a good shorted turn.The ballast itself runs at 2.56 MHz. One side has a die-cast shield, and the other a plated brass (I cut through the plating, definitely brass) heat sink. Removing these, we see a coil and some diodes under the shield, and a complementary pair of MOSFETS (IRF9214 and IRF214). This formed a self-oscillating half-bridge that GE used to use in their CFLs.You can see a lot of char on the PCB, and the crystalization of the solder. These and other CFLs ran pretty close to the device ratings, because electrical margin ate directly into profit margin, and nobody likes to pay a lot for a light bulb. This one was really expensive, due to the shield, the complicated glass of the lamp, etc. Once LEDs because viable, CFLS have all but disappeared.Hope you found this interesting,John

author: ConKbot
author_rank: Super Contributor
timestamp: November 09, 2020, 02:40:42 am
content: GE solving fluro bulb aging reducing bulb aging, other manufacturers doing it by making the driver so cheap the driver fails first. I can see why this type didn't catch on.

author: james_s
author_rank: Super Contributor
timestamp: November 09, 2020, 05:05:39 am
content: I remember the Genura lamps. They were cool, but very expensive, they cost more than $30 each back when they came out and they were not widely available. I never ended up getting one of those, but I did get my hands on a 165W Philips QL induction lamp and driver. Then just a few years ago I picked up a pack of "Finally bulbs" that Costco had, the marketing on the package was somewhat cryptic but I figured out they must be induction lamps and they are. I don't know if they're made anymore though, they were obsolete by the time they came out and I only bought them because I'm a lighting geek. I believe the company was affiliated with VU1, the company that made the very novel but also too little, too late "ESL" bulb, essentially a flood gun CRT. I have one of those too, of the three I bought one was defective out of the box and another failed soon after.

author: Haenk
author_rank: Super Contributor
timestamp: November 09, 2020, 08:22:35 am
content: Datecode dates this 19 (!) years back. LED certainly was no option back then, even the most crappy ones were at least 10-15 EUR.Considering the waste, these compact CFLs should never have happened. I have to admit, I had dozens installed as well...(Though CFLs are not bad in general, i.e. with electronic load and replacable tubes. In office, I have a couple of hundred installed - after 10 hours daily use for 15 years I think I have replaced 4 or so now.)

author: JohnG
author_rank: Frequent Contributor
timestamp: November 09, 2020, 02:12:55 pm
content: If you look at the picture of the induction coil, you can see missing insulation and charring. I think this is where the failure occurred. However, the lamp had gotten dimmer over time, and the glass had gotten that grayish color that old fluorescent lamps get, so perhaps some of this was due to phosphor degradation.What you cannot see, because my photography skills are not great, is that on the thin little stem that goes down inside the induction coil, there is a tiny metal clip inside the bulb. I'm not sure if it is for starting, or if it is part of the mercury maintenance system like the amalgam pellet. I did not break open the bulb to see more clearly.Also interesting is the circuit used. Very simple, wholly analog, and few parts. Some description can be found here:https://patents.google.com/patent/US5796214A/en. It makes use of P-channel FETs, which are expensive compared to N-channel, but the whole circuit is basically a soft-switched resonant converter.Finally, I hear there was an allowance made by the FCC to raise the EMI limit at 2.65 MHz, so that you could sell these lamps. I don't remember how wide it was, but this whole circuit had to be tuned and keep its frequency in the window. A nice feat of engineering to make this all work.John

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 09, 2020, 02:27:45 pm
content: Quote from: Haenk on November 09, 2020, 08:22:35 amThe problem was, classic light bulbs were banned and LEDs not yet mature enoughSo CFL was for some time the only way

author: JohnG
author_rank: Frequent Contributor
timestamp: November 09, 2020, 02:36:04 pm
content: In the US, cost-effective LED lamps were already here by the time they started to ban incandescent lamps. They are even cheaper, now. People bought CFLs because initially, they used a lot less electricity and lasted a lot longer. The biggest early customers for CFLs were businesses, especially the hospitality industry (hotels and the like). The energy cost payback was measured in months, even early on. If you had a lot of ceiling fixtures, the labor cost savings was huge as well. The savings were enough that they overlooked the bad color and noise of the early lamps, which got better quickly.John

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 09, 2020, 02:45:38 pm
content: Most business and municipal lighting here (and neighboring European countries) used linear fluorescent, as they are long lasting and proven by decades, and have better efficiency than compact onesYou will see incandescent bulbs just at homes

author: james_s
author_rank: Super Contributor
timestamp: November 09, 2020, 06:48:18 pm
content: Quote from: Miyuki on November 09, 2020, 02:45:38 pmThat's largely true here, but incandescent was widely used for decorative and accent lighting. Linear fluorescent lacks that "cozy" look that is often desired in places like hotel lobbies.I upgraded every light in my house to CFL and stopped using incandescent for general illumination completely around 2001, long before any bans. Around 2010 good LED bulbs finally appeared and I started slowly upgrading to those, I swapped out my last CFL in service a couple years later by which time LED bulbs had dropped dramatically in cost.

author: helius
author_rank: Super Contributor
timestamp: January 08, 2021, 03:25:10 am
content: I recently acquired an electrodeless lamp. There seem to be many more companies getting into this market these days.It's a 200W globe with a hollow center to accept the emitting coil. Extremely bright: not too sure where I can put it.

author: JohnG
author_rank: Frequent Contributor
timestamp: January 08, 2021, 02:28:24 pm
content: Quote from: helius on January 08, 2021, 03:25:10 amI'm curious about this. would you mind sharing more details, such as the model of the lamp? Used or new? I'm assuming that's 200 W input power? That would make a helluva bright lamp.If you need an intensely bright (high optical power density) source with a lot of absolute optical power, these lamps are probably the way to go, since you can't run an LED at such high temperatures. For most lighting purposes, it has become very difficult to compete with LEDs.Cheers,John

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 08, 2021, 02:39:38 pm
content: What happened to these?https://en.wikipedia.org/wiki/Sulfur_lamp

author: SeanB
author_rank: Super Contributor
timestamp: January 08, 2021, 03:18:34 pm
content: Funny enough I have a number of CFL lamp units that used a plug in base and then you simply used a standard 2 or 4 pin PL type lamp in the socket, and the base provided the drive for the cheap PL unit. Some used an all electronic ballast, using TO220 MJE 13004 (?) transistors, though later on the case changed from TO220 to TO92.Another type I have a few of still uses a toroidal wound ballast coil in the base, and this works with 2 pin PL lamps, as it has the starter glow bottle in the lamp itself, so the changing of lamp and starter is a single operation. The electronic ones often could use a 2 pin or 4 pin PL base lamp, as they had a dedicated PTC thermistor in there to allow the filaments to heat up to operating temperature, so the lamp would take a half second to come on. electronic ones I actually used to repair, as the lamp was, in around 1994, very expensive to buy, so repair was economical, as the typical failures were the fusible resistor in the mains input burning out, and the input bridge rectifier ( 4 1N4003 diodes, replaced with 1N4007 always) having a shorted diode, and perhaps a failed 2u2 400V 85C electrolytic. Any value from 1u to 3u3 that would fit went in there, not a critical part, and the odd failed transistor, though by the time the transistors failed you could not solder to the board, as it was burnt black and the traces would fall off.But now CFL units are cheap, actually cheaper than the PL lamps, and LED lamps are under $1 each, so are considered disposable, though the LED floodlights at $10 are almost worth stripping for parts, or at least for reuse of the good parts to fix failed ones.

author: helius
author_rank: Super Contributor
timestamp: January 09, 2021, 02:24:32 am
content: Quote from: Alex Eisenhut on January 08, 2021, 02:39:38 pmIt appears that a few companies have tried to develop microwave-excited sulfur lamps since the original 1980s patents. They never seemed to find much of a market, probably because of the extreme intensity and cooling requirements. Sulfur lamps don't make sense unless very intense, and the high internal pressure requires rotating the bulb to prevent hot spots forming. So you can have a projected 1,000,000 hour life, but the waveguide and rotator motor may need to be replaced several times. Seems to be optimizing the wrong part as noted in Reply #1.How you deliver the intense light is also an ergonomic and optics problem. Either a very high ceiling bay (terrible for HVAC efficiency) or mirrors and light pipes? So complicated. I would still love to have one!

author: SilverSolder
author_rank: Super Contributor
timestamp: January 09, 2021, 04:40:14 pm
content: Very cool teardown, never heard of this type of lamp.I have a couple of 50W CFLs (150W incandescent equivalent) in the garage that are approaching 18 years old, still shining bright. They were not all badly made...

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2021, 11:46:28 pm
content: Quote from: JohnG on January 08, 2021, 02:28:24 pmI have a very similar lamp, it's a Philips QL, mine is the 165W version of this:http://lamptech.co.uk/Spec%20Sheets/D%20ED%20Philips%20QL85.htmThese things were the bees knees prior to the LED revolution. They were very expensive though so never really showed up in domestic settings. More recently an induction lamp did come to market though, the "Finally bulb" which was sold by Costco for a few months a couple years ago, I bought a pack of them just for the novelty factor. It was obvious they were too little, too late, LEDs had won the race years earlier but the induction lamp is a nifty bit of technological history.I have one of the GE Genura lamps that started this thread too, I actually had forgotten I owned one and don't recall getting it but I found it going through one of my boxes of rare lamps. It's hardly been used.

author: james_s
author_rank: Super Contributor
timestamp: January 10, 2021, 12:16:16 am
content: Quote from: helius on January 09, 2021, 02:24:32 amI remember reading about the microwave sulfur lamp when it was developed, I only ever saw (pictures of) one or two actual installations, they used long light pipes to spread the light across the area. I read that the light had a distinct greenish tinge to it although I never saw one in the flesh.LEDs are wonderful but they really have made lighting boring. As recently as a decade ago there were numerous different competing technologies, incandescent, fluorescent (linear, compact and electrodeless), low pressure sodium, numerous flavors of HID, and active development in many of these. Thousands and thousands of different lamps were produced in a dizzying array of sizes and shapes optimized for all different jobs. Now all lighting development is LED, a few years ago a friend of mine in the industry went to a trade show and he said the vast array of different technologies was gone, literally everything there was LED, it was like nothing else existed.

author: james_s
author_rank: Super Contributor
timestamp: January 10, 2021, 12:21:15 am
content: Quote from: Miyuki on November 09, 2020, 02:27:45 pmIncandescent lamps weren't banned here until well into the LED era, and even the ban still had lots of loopholes for decorative and special purpose lamps, and unusual wattages, like 53W high efficiency halogen capsule inside a traditional looking bulb to replace 60W. Personally I don't like the idea of any sort of mandate or ban, but I recognize that new technologies like LED bulbs need a kick in the pants to take off due to the fact that most people are short term thinkers and will buy the 75 cent bulb that uses $50 worth of electricity over its lifetime over the $20 bulb that uses $5 worth of electricity every time. What I would have done is impose a tax on low efficiency lamps to subsidize high efficiency LED lamps, that way people who need or really want the old style bulbs can still get them but the higher cost of ownership is nudged up front rather than being hidden in the power bill.

author: JohnG
author_rank: Frequent Contributor
timestamp: January 11, 2021, 01:53:56 pm
content: Quote from: helius on January 09, 2021, 02:24:32 amHere is an interesting link (Molera and Cebrian) on the optical subdivision of a carbon arc light using a system of mirrors, tubes, and prisms,from 1879:https://play.google.com/books/reader?id=Vk_XQNzC_HQC&hl=en&pg=GBS.PA33, page 33 if the link doesn't get you there.Interestingly, they also address running the arc in vacuum to get longer electrode life, as well as converting some of the prodigious UV output of the arc into visible light.Cheers,John