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The proposed ban on incandescent lamps . . . What will it mean? In February 2007, Malcolm Turnbull, Federal Minister for the Environment and Water Resources, announced that incandescent light bulbs would be phased out and replaced by more efficient lights such as the compact fluorescent light. Superficially, it seems like a good idea but closer examination shows that there would be substantial drawbacks. T here is no denying that Malcolm Turnbull is a very clever man. He was the co-founder of Ozemail, a successful barrister and merchant banker and now a prominent member of Federal parliament. But that does not make him infallible and particularly not with regard to decisions involving electrical and electronic equipment. We think he has been badly advised. Yes, incandescent light bulbs are inefficient when compared to fluorescent lights and other forms of lighting. As a corollary of that, they pump out a lot of heat for the amount of light that they produce. And yes, typical compact fluorescent light (CFL) bulbs produce about five times the light output of 10  Silicon Chip an equivalent incandescent bulb. Under ideal conditions, they can also last somewhere between four and 10 times longer than incandescent lamps and therefore can lead to substantial energy savings. The trouble is, ideal conditions do not occur very often in household use. For a start, depending on ambient temperature, a CFL takes about 10 to 15 minutes to reach full brilliance. So while they come on as soon as you throw the switch, their initial light output can be quite weak and can have a tendency to flicker as well. If you install a CFL in a toilet or bathroom you may find that they are seldom on long By LEO SIMPSON enough to get to full brilliance. Some very ambitious claims are made for life on CFLs. For example, a GE 15W unit in our office at the time of writing claims 8000 hours on the packet while a range of CFLs made by Mirabella claims 15000 hours. In our experience, these are very ambitious figures and are probably longer than you could expect from a typical 36W fluorescent tube. After all, at 10 hours a day, 15,000 hours is equivalent to an operating life of over four years. Not only that, by the time 15,000 hours rolled around, a typical 36W tube would be a pale tube indeed. CFLs certainly do not last as long as conventional fluorescent tubes and the reduction in light output is siliconchip.com.au proportionately greater as they age. A 15W CFL may be equivalent to a 75W incandescent when new but after several thousand hours its light output will be quite weak, if indeed it has survived for that long. In fact, the only practical applications for CFLs are where they are in use every day for several hours at a time. If you operate them under those conditions, particularly where they are used in applications such as stair wells and external lighting for home units (ie, on for long periods at a time), they can easily last for around 8000 hours or more. But if you use them in other domestic applications, their life can be shortened drastically, to the point where they often do not last as long as the much-maligned incandescent. The reason they don’t last well where they are used for frequent short periods is that they simply don’t work well with short start/stop cycles. The tube phosphor becomes blackened and the tube becomes much harder to start or the complex electronic driver circuit simply fails. As you can see from the description in the separate panel, a CFL circuit may use up to 30 components and these are highly stressed, operate at high temperatures and are subject to severe temperature cycling if frequently switched on and off. Other drawbacks If you take a look at the packet for any CFL, you should see warnings about suitability. Specifically, they are not suitable for use with electronic dimmers. In fact, they don’t work at all with dimmers. Any warranty will be void if they have been used with a dimmer. Nor are they suitable for use with any electronic switch or remote control, sensor lights or with timers. The last two are significant because that is an acknowledgement by the manufacturers that CFLs do not last well when switched on or off frequently or at short time intervals. Heat, cold and vibration CFLs cannot be used in any application where they get hot. They need plenty of air circulation around them. They cannot be used in recessed light fittings or in table lamp fittings where they are closely confined or poorly ventilated. That rules out a siliconchip.com.au T11/07 20 February 2007 World first! Australia slashes greenh ouse gases from ineffic ient lighting In a world first move, the Australian Government is taking action to phase light bulbs. out ineffic ient The step, announced tod ay at Double Bay Public School by Minister for the and Water Resources, Ma Environment lcolm Turnbull MP, should reduce Australia’s greenh emissions by 4 million ton ouse gas nes by 2012. The reduction in emissions will increase as the phase out progresses and the ann reduction between 2008-2 ual average 012 is estimated at around 800,000 tonnes. However, the annual cut in emissions by 2015 will have soared to an esti mated 4 million tonnes per Household lighting costs annum. can be reduced by up to 66 per cent. “The most effective and immediate way we can red uce greenhouse gas emissi using energy more efficien ons is by tly,” Mr Turnbull said. “Electric lighting is a vita l part of our lives; global ly it generates emissions cent of those from all the equal to 70 per world’s passenger vehicle s.” “But it is still very ineffic ient. We have been using incandescent light bulbs and up to 90 per cent of for 125 years the energy each light bul b uses is wasted, mainly as heat.” “A normal light bulb is too hot to hold – that heat is wasted and globally represe of tonnes of CO2 that nee nts millions dn’t have been emitted into the atmosphere if we had efficient forms of lighting used more .” “These more efficient ligh ts, such as the compact fluo rescent light bulb, use aro cent of the electricity to und 20 per produce the same amoun t of light.” “A compact fluorescent light bulb can last betwee n 4 and 10 times longer incandescent light bulb, than the average which can lead to major savings in household ene rgy costs.” “While they may be more expensive to buy up fron t, they can pay for themse power bills within a yea lves in lower r.” In Australia, lighting cur rently represents around 12 per cent of greenhous from households, and aro e gas emissions und 25 per cent of emissi ons from the commercia l sector. Working with its state and territory counterparts, the Australian Government phase out all inefficient will gradually light bulbs and is aiming for full enforcement of new standards legislation by lighting 2009 to 2010. Special nee ds areas, such as medical oven lights, will be taken lighting and into consideration. The Government will also work with the world’s larg est manufacturers of ligh including China, to broade t bulbs, n the benefits beyond Au stralia. “The International Energy Agency has estimated tha t if all countries made the to compact fluorescent ligh global switch ts that by 2030, annually it would save energy equ more than 5 years of Au ivalent to stralia’s current electricity consumption,” Mr Turnbu ll said. “The climate change cha llenge is a global one. I encourage other countries Australia’s lead and make to follow the switch to more energy efficient products like com fluorescent light bulbs.” pact lot of lamp fittings, including oysters (ceiling) and those which include a glass tube within another glass housing. Nor can they be used in ovens, microwave ovens or refrigerators. Why not refrigerators? Because CFLs and standard fluorescent lamps, for that matter, will not work in the cold; they simply refuse to start. And since CFLs have lots of internal electronic components they don’t like vibration either. That means that they should not be used inside garage door openers, vacuum cleaners or combined light/exhaust fans in bathrooms. There is also a substantial environApril 2007  11 Typical CFL lamps as used already in thousands of homes, offices and public buildings around Australia (indeed, around the world). The manufacturers make some incredible claims for long life and brightness – which we find just a little difficult to substantiate. mental drawback: mercury. All fluorescent tubes contain a small amount of mercury and CFLs are no different. The mercury is there because that is what sustains the electrical discharge in the tube once it is fired. When the tube fires, the mercury is vapourised by the high voltage across the ends of the tube and the resulting electrical discharge produces intense ultraviolet light. This irradiates the white phosphor coating on the inside of the tube and it “fluoresces” to produce visible light. The amount of mercury inside a CFL is small, typically 4 to 5mg. While it is inside the tube, it is perfectly safe. But once the tube is broken or crushed, as will ultimately happen, the mercury will be released into the environment. With millions of CFLs likely to be disposed of every year, that amounts to a lot of mercury going into the environment. Electrical interference CFLs can cause two forms of interference, electrical and infrared. Part of 12  Silicon Chip the electrical interference is inherent in any fluorescent or vapour discharge tube. The high voltage discharge radiates interference over a wide frequency range, up to 10MHz or more and can interfere with radio reception on the broadcast and shortwave bands. The interference from conventional fluorescent tubes is modulated at 100Hz, giving a rough buzzing sound in an AM broadcast radio. But interference from a typical CFL is worse because it is modulated by the high frequency inverter used to drive the tube. So whereas a fluorescent tube might cause a buzzing sound on weak stations in the broadcast band, CFLs can completely obliterate reception in rural areas. While the discharge inside fluorescents and CFLs is mainly ultraviolet, they also produce heat (infrared) and this is also modulated by twice the driving frequency. So a typical fluorescent light produces heat (you can easily feel it) modulated at 100Hz. A CFL also produces heat (they get quite hot) modulated by twice the inverter frequency. This modulation can typi- cally be at around 20-30kHz but can be in the slightly higher frequency range used by typical infrared remote controls. So if you have a CFL in the same room as your TV or hifi system, the infrared remote control may not work at all – its signal will be completely blanketed by the modulated infrared from the CFL. By the way, in some CFLs, you can actually hear the whistle from the inverter/electronic ballast. Whether this is a sub-harmonic or because the operating frequency is low is not clear but some people will find it objectionable. Huge range of incandescents So far this article must seem pretty negative concerning CFLs. We have harped on about short life, reliability, heat, cold, vibration, interference and so on. What other problem could there possibly be with a general changeover from incandescent lamps to CFLs? The biggest problem of all is simply the huge range of currently available incandescent lamps. In my own home I can count at least siliconchip.com.au They haven’t really thought this one through, have they? This photo by no means shows the full range of incandescent lamps currently in use (eg, how about all the high intensity halogen floodlights out there) – but the only incandescent lamps that CFLs can now replace are the standard-sized BC and ES general lighting types. 10 different styles of incandescent bulb. In addition to the standard-sized bayonet cap (BS) and Edison screw (ES) bulbs, there are fancy round, candle and twisted candle, in miniature BC and ES, as well standard bases, large round (100mm and larger), double-ended lamps for lighting bathroom mirrors and cabinets, miniature incandescents for sewing machines and so on. Then there are 100W and 150W ES reflector lamps used in outdoor security lights. Where does it all end? Most of these “non-standard” incandescent lamps will never be duplicated in CFL, particularly the smaller ones. If you want to see the scope of the problem, just visit your local lighting retailer or a branch of Bunnings. The range of available lamps is astounding. Even if CFLs can fit in place of incandescents in many light fittings, they may still not be suitable because of their longer form factor – they may simple poke out of a fitting rather than be fully housed. Some light fittings do not suit CFLs because of their different light output siliconchip.com.au distribution. For example, most CFLs have little light output on their longitudinal axis. With the best will in the world, we cannot see too many people being happy with a 24-lamp chandelier fitted out with CFLs! And what about 240VAC doubleended halogen lamps used in higherpowered exterior lighting used around homes and commercial buildings? In truth, we do not yet know the scope of this proposed ban or phaseout of incandescent lamps because the announcement released by Malcolm Turnbull (reproduced elsewhere in this article) is quite general in tone, with no specific details or timetable. But if the aim is to phase out inefficient incandescent lamps, what about 12V halogens used in such large numbers in modern homes? These are a real drain on Australia’s electricity grid, both in homes and retail showrooms where their numbers are so great that they substantially increase the air-conditioning load. Mind you, if 12V halogens were to be banned, a great many homes and shops would require substantial rewiring and all new lamp fittings, unless reasonably effective LED equivalents become readily available. Existing LED equivalents are expensive and not as bright as halogens. Ultimately, if the proposed ban is to be all encompassing, a large proportion of home-owners are going to be very unhappy when they realise the full implications. Finally, if you don’t accept our word on the above disadvantages and drawbacks of CFLs, just go to http://www. gelighting.com/na/business_lighting/faqs/cfl.htm This is a list of frequently asked questions (FAQs) on CFLs on General Electric’s Consumer & Industrial Lighting website. Note that GE do have a dimmable CFL available in the USA but we have not seen a version of it on sale in Australia. Will the whole idea of phasing out incandescents be quietly shelved after the next Federal election? We think that is a strong possibility. If not, you had better stock up on the more unusual incandescents in your home. April 2007  13 How CFLs work make up an oscillator or inverter. The fluorescent tube is driven via inductor L2 and winding N1 of the transformer. T1 also drives the gates of Q1 & Q2 via windings N2 & N3 which are connected in antiphase. Tube starting This photo shows the internal circuitry of a current model CFL used in a recent promotion by Sydney’s major electricity distributor, Energy Australia. The two Mosfets are tiny, in TO-92 encapsulation. The 4.7mF main DC filter capacitor can be clearly seen. It is this capacitor which is the component most at risk from high temperatures. The operation of a compact fluorescent lamp (CFL) is rather more complex than the simple resistive element of an incandescent lamp. The circuit above is for a typical compact CFL operating at 240VAC. Note that this is a general description of CFL circuit operation. Actual circuits vary widely from brand to brand and model to model but the broad principle of operation is much the same. It uses a bridge rectifier in series with a small inductor (L1) and 47W resistor together with diode D1 and capacitor C1, to develop around 340V DC. The rectifier in American CFLs (operating from 110V) uses a voltage doubler on the input instead of a bridge rectifier. The 340V DC is fed to the rest of the circuit which functions as an inverter and ballast. In effect, what happens is that the circuit operates in two separate modes, one to start the tube and the second mode for normal running. Two Mosfets (Q1 & Q2), transformer T1 and a number of associated components Taken with a short antenna in close proximity to CFLs, these scope screen shots demonstrate the RF interference modulation. In this scope shot, we see a 22kHz carrier modulated by 100Hz. The 22kHz is the inverter frequency of the CFL ballast circuit while the 100Hz is a product of the bridge rectifier and 50Hz 240VAC mains supply. 14  Silicon Chip When power is first applied, the 2.2nF capacitor connected to Diac 1 charges via the 560kW resistor. When the voltage reaches about 30V, the Diac fires (breaks down) and discharges the capacitor into the gate of Q2. Zener diode ZD2 protects the gate from over-voltage. Mosfet Q2 is now switched on and current flows from the positive supply via the 47nF capacitor, the fluorescent tube top filament, the 3.3nF capacitor, the second tube filament, inductor L2 and transformer T1’s N1 winding. This current flow in N1 then applies gate drive to Q1 via N2 and switches off gate drive to Q2 via N3 due to the antiphase connection of this winding. If oscillation doesn’t occur, the process starts all over again with the 2.2nF capacitor charging again to fire the Diac to turn on Q2. When oscillation does occur, Mosfets Q1 and Q2 rapidly switch on and off in alternate fashion. The frequency of operation is set by the combined inductance of L2 and the N1 winding, together with the 3.3nF capacitor across the tube. The startup circuit comprising the 2.2nF capacitor and the Diac is now prevented from operating by diode D2. This diode Here we see the same CFL waveform running at a higher timebase frequency to show its roughly sawtooth waveform. siliconchip.com.au 47nF 340V P-P D1 + A 240V AC N 47 ~ A K +340V 2.2nF ~ 330k 560k 100nF 100nF A The frequency of oscillation is now deter- A Q2 G S K 2.2nF L2 D 10 N3 ZD2 33 A mined by the prop­erties of the core used for transformer T1. As the current builds up in winding N1, the core begins to saturate. When this happens, the flux in the core stops changing and gate drive to Q1 or Q2 ceases. The flux now collapses to drive the opposite Mosfet and this process continues to maintain oscillation. The current through the tube is limited by the current at which T1’s core saturates and by L2’s inductance. The two 10W resistors, together with zener diodes ZD1 & ZD2, limit the gate drive to Q1 & Q2, while the 2.2nF capacitor The scope shot above, from another CFL, shows a 30.75kHz waveform modulated at 100Hz while the scope shot at right shows the same waveform at higher timebase speed (20ms/div) to show its sawtooth shape. siliconchip.com.au 3.3nF 33 DIAC1 A typical circuit for a 240V CFL. It incorporates a bridge rectifier to produce about 340V DC and an electronic ballast which is basically an inverter/oscillator. Normal running CFL ZD1 N1 L1 discharges the 2.2nF capacitor every time Q2 is switched on. The oscillator current now flows through the filaments of the fluorescent tube and allows the normal mercury discharge to take place. This means that the fluorescent tube will light up. When this happens, the 3.3nF capacitor is effectively shunted by the mercury discharge and the voltage across the tube is now about 100V peak. S K K C1 100nF 4.7 F Q1 G N2 D2 – T1 D 10 at the cathode of D2 forms a snubber network to suppress commutation in the opposing Mosfet at switch on. This considerably reduces the switching losses in each Mosfet. The 330kW resistor in parallel with this capacitor keeps diode D1 reverse biased at start-up. Finally, the 4.7nF capacitor in series with one of the tube filaments ensures that the tube is driven by AC. This prevents mercury migration to the tube ends which would cause blackening and shorten the tube life. SC None of these waveforms reveal the modulated broadband RF noise radiated by CFLs but this is easily demonstrated if you operate a standard AM broadcast band radio in close proximity to any CFL. April 2007  15