Teardown of el-cheapo fluorescent energy-saving lamp

[wkb]

One of my fluorescent "energy saving" lamps just died on me, which obviously gave me an excuse to dismantle it to inspect it's guts.

As you can see, really high-quality soldering, but oh-so-RoHS compliant    A money saver it for sure was not, typical case of infant mortality.   

[SeanB]

So what died? Bridge diodes, transistor and of course the fusible resistor. Capacitor may have gone open circuit as well.

[wkb]

So what died? Bridge diodes, transistor and of course the fusible resistor. Capacitor may have gone open circuit as well.

I have not tried to troubleshoot it.  I did notice some rather lousy soldering on both one through-hole component as well as a multiple SMD components.

[SeanB]

What do you expect from a product made by the cheapest supplier using the cheapest parts, assembled by the lowest cost poorly trained labour using the cheapest equipment. Amazing that most work when you buy them, as I often have faulty ones in a big batch, so I prefer to pay more for the better quality ones.

[Mechatrommer]

so I prefer to pay more for the better quality ones.

what is better quality brand? i have bunch of philips flou's that died, almost the same circuit as posted above. now i have in stock many type of brand, each time i replace, i will write the date on it, so i can check which one will last longer than others. your recommendation may speed this process up dramatically.

[Neilm]

I remember reading an article in a magazine that said that poor quality "energy saving" light bulbs might actually waste more power than ordinary light bulbs. This is because they would produce harmonics on the mains that would cause parts to heat up and waste power.

Neil

[Zero999]

I remember reading an article in a magazine that said that poor quality "energy saving" light bulbs might actually waste more power than ordinary light bulbs. This is because they would produce harmonics on the mains that would cause parts to heat up and waste power.

You mean they have a poor power factor.

Any fluorescent lamp under 100W will not have a power factor correction unit which is the case for all CFLs.

I doubt they really waste more power than the equivalent incandescent, even when the power factor is taken into account.

[Neilm]

I remember reading an article in a magazine that said that poor quality "energy saving" light bulbs might actually waste more power than ordinary light bulbs. This is because they would produce harmonics on the mains that would cause parts to heat up and waste power.

You mean they have a poor power factor.

Any fluorescent lamp under 100W will not have a power factor correction unit which is the case for all CFLs.

I doubt they really waste more power than the equivalent incandescent, even when the power factor is taken into account.

Not the power factor, but the switching they used would cause harmonics on the mains, causing parts of the supply chain (transformers and the like) to heat up. Harmonics are covered considered under EMC legislation.

Neil

[IanB]

The real issue with CFLs is the vastly increased complexity of manufacture and consumption of resources (look at all those disposable electronics in every lamp). Even if they get recycled they will be shipped by the container load to China where they will be processed in human misery factories. Then of course there is the mercury content, multiplied by the billion for every lamp made. Sometimes when the lamps fail they overheat and cause fires, leading to further costs.

CFLs are born out of politics, not science, and few political decisions are good ones.

[Neilm]

CFLs are born out of politics, not science, and few political decisions are good ones.

Amen to that - CFLs, Lead free solder, the list goes on.

Neil

[kripton2035]

it's time to switch to led lights ...
I'm pretty sure the quality of the led lights supply is not more than this cfl light,
but at least it consumes really less power...

[siliconmix]

the bumf on these energy saver bulbs  is that they last ten years .my arse.3 to 5 average i've experienced.i'd take them back but i forget where i bought them.great things mind use less juice you just have to put up with falling down the stairs every no and then

[oliver602]

Wouldn't it be better to have the electronics in the light fitting instead of attached to the bulb? more room to keep cool etc, less waste. Besides 'lack of adoption'(are there domestic fittings like this available? I can't find any) is there a technical reason for this?

[westfw]

See also http://www.instructables.com/id/Take-apart-a-Compact-Fluorescent-Bulb/

[Zero999]

Not the power factor, but the switching they used would cause harmonics on the mains, causing parts of the supply chain (transformers and the like) to heat up. Harmonics are covered considered under EMC legislation.

I don't think you understand, the poor power factor and switching noise are separate issues.

High frequency noise generated by the switching transistors, doesn't travel very far and doesn't cause any problems in the power supply chain but it can interfere with other pieces of equipment: radio, TV, etc.

The poor power factor is a result of the current drawn by the CFL not being in proportional with the mains voltage. The input of a CFL consists of a bridge rectifier with a capacitor connected across it. Current is only drawn from the mains when the voltage is 0.7V greater than the voltage on the capacitor so the resulting current waveform consists of high current peaks every time the mains voltage passes through 90^o and 270^o.

The distorted current waveform causes problems in the electrical supply chain: the high current pulses and associated harmonics cause greatier heating in transformer cores and triple-n harmonics add together in the neutral conductor, resulting in a higher current than predicted.

Wouldn't it be better to have the electronics in the light fitting instead of attached to the bulb? more room to keep cool etc, less waste. Besides 'lack of adoption'(are there domestic fittings like this available? I can't find any) is there a technical reason for this?

You can buy lamp fixtures with built-in drive electronics for CFLs. The problem is, the ballast has to be matched to the tube so you can't put a 7W tube into a fitting designed for a 15W lamp and most CFLs are designed to retrofit fitting designed for incandescents.

I suppose it's possible to develop a system to tag each CFL so the ballast knows the power rating and delvers the correct current but it's probably not worth the development cost and standardising it wouldn't be easy.

[PStevenson]

these are pretty cool things for salvagers like myself, minus the hardware of course there are enough parts in a CFL to make a really nice treble booster overdrive for guitar.

where I live these things actually come in the post from the council for free (I didn't request them they just send them, I don't know why and when I contacted them, they didn't know why either, nor did they stop) so having gained a cupboard full of the things I started dismantling them, I don't use them much since I started using LED lights, definitely worth salvaging from if you're that type.

[jerry507]

where I live these things actually come in the post from the council for free (I didn't request them they just send them, I don't know why and when I contacted them, they didn't know why either, nor did they stop) so having gained a cupboard full of the things I started dismantling them, I don't use them much since I started using LED lights, definitely worth salvaging from if you're that type.

In Iowa, the power company sends them to you for free if you ask them. They hate building new power plants because of the cost and risk, so they'd much rather have homes drawing a lot less energy to make room for industry. The US will start phasing out incandescent bulbs in 2014, I gather a few countries like Australia and others have already started. Despite naysayers, this is quite a good thing

[westfw]

CFLs are rather a kludge of a replacement for incandescants, though.  A sort of "where's the worst possible place to put an electronic ballast."  Sigh.  And few fixtures are well-designed for CFLs.  And the brightness claims are frequently bogus and usually not enough (I used to have a 200W desk lamp and 300W halogen torchieres.  The energy efficient replacement is "remodel the house." (the kitchen is nice.  three dual four-foor t12 tube fluoresents in the ceiling, plus small t5 fluorescents under each cabinet, plus occasional halogen spots.  All I need is an extra 12 inches between floors, and I could do that everywhere. (but let's not get started on what building codes actually require!)) (actually, the replacement is "use twice as many lamps and put up with it being dimmer.")

For CFL, I rather like Ikea for both their bulbs and fixtures, though I usually end up buying the cheap CFLs at the local bulk store.  In general, I haven't found name-brands to be significantly better than no-names.   Nor cheap lights with external electronic ballasts to be that much more reliable than CFLs (just ... much harder to fix.)  The "obvious" failures involve swollen and burst electrolytics, but I don't know for sure whether that was the initial failure or a result of failure somewhere else; there are frequently other failures as well  (but: component with finite and exponentially decaying lifetime based on temperature, stuffed inside a lamp base...)

It'd be interesting to see a series of projects (for hobbyists) based on CFL guts...

[wkb]

Believe it or not: #2 out of a batch of 3 said 'pop' this morning. Apparantly something in the electronics went south 

[Rerouter]

kinda looks like you could get a few bits of a switch mode supply out of it, but the real question on my mind is, if one went and redesigned those boards with ceramic caps, and to be all the more reliable, would it exceed or fall short of the cost of replacing the crappy ones every few months

[kripton2035]

I still cannot understand why people loose time and money to build, buy and fix these cfl lights
the led lights are more interesting in many points ...

[westfw]

I can't get a 75W equivalent LED light for a reasonable price, and that's about the minimum that I need for many fixtures.

Also, existing LED lights aren't living up to their promises either; many use inferior quality LEDs whose output degrades quite rapidly, efficiency is similar to CFLs, and the power supplies are frequently subject to the same problems as CFL ballasts (more electrolytic caps near heat-emitters.)
(The electrolytics in question typically rectify the 60cycle mains to HVDC, prior to a fancy (or not) switching circut that does voltage conversion and/or current limiting.   I don't think ceramics are a viable alternative there.)

(An interesting idea is to convert to rectified HVDC in the fixture, using nice big caps far away from most of the heat.  That should reduce some heating in the lamps themselves (ripple current in the caps), prevent cap failures from being so noticeable (the following circuits would get DC anyway), and avoid the emissions problems that might be caused by long wires leading from the electronic ballast to the lamps.  And it would be backward compatible with existing lamps that have full-wave rectifiers anyway.  And it wouldn't even add a lot of cost to the fixture.  You could even do a magic snake-oil "extend the life of your CFL bulb" cord-wart thing that might actually work.  PROVING that it works might be a problem.  And I suspect that there are all sorts of regulatory issues involved (sigh.))

[IanB]

I've noticed that all the CFL bulbs on the shelf say "not dimmable", and all the LED bulbs I've looked at say "dimmable". So I'm not sure what circuit topology the LED bulbs use but I suspect it is very simple. If the circuit tried to regulate power to the LEDs it would fight against the dimmer switch.

The LEDs I've seen are in the $15-$20 price range if not more, and that seems a bit high for uncertain quality and technology (even with a brand name like Philips).

[wkb]

Yup, mine are definitely stamped "non-dimmable"

[grumpydoc]

The LED lamps go "pop" as well - they also cram electrolytics into a small, hot, space.

Here's one I fried (well, it fried itself) earlier - a 3x3W GU10 jobbie. Don't know what died exactly - there's a dead short across the bridge output. I assumed that it was the cap but that's still reading OK. Won't know whether it's gone high resistance until I build an ESR meter but it's reading 4.6uF. If you look carefully you can see where the track on the mains side of the bridge tried to act as a fuse. Not sure what the blue thing is - PTC or fuse, presumably, but it's insides are liberally blown all over the electronics.

Active components, for interest, are - MB6S 0.5A BR, 9910B LED driver, SM2N60 n-channel FET, and a MURS160T3G power rectifier (marked U1J). Oh and a zenner of some sort but being SMD all I have to go on is the Z1 label on the PCB printing.

Circuit looks straight off the 9910B data sheet.

The LED chips themselves are OK so I'm just trying to figure out how best to reuse them.