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An incredible year for Solid-State Lighting – the future is bright for LEDs

issue 34 Dec / Jan 2006 / 7

In this column last year, LEDs were described as the unstoppable lighting revolution predicted to radically change the face of the lighting industry forever. However, the pace of LED development and a sudden realisation by consumers, companies and Governments that the environment and energy usage is key to sustainability and possibly life itself could ensure Solid-State Lighting is not only Desirable but could create a market valued at $155 billion by 2020.

The year has seen a relentless amount of research focused on Solid-State Lighting (SSL)
technologies resulting in significant new lighting developments that have propelled LEDs to overtake the majority of conventional light sources in terms of efficacy or Lumens/Watt, lifetime and light source control. The lighting industry will look back at 2006 and remember it was the year when LEDs and Solid-State Lighting grew up to compete on equal terms with compact fluorescents, Metal Halides and the majority of fluorescent tubes. Previously, LED evangelists would feel obliged to proclaim all of the LED benefits in an attempt to overcome two major weaknesses, notably, cost per lumen and efficacy. Today, the major LED manufacturers are overcoming such weaknesses to pave the way for rapid adoption of LEDs in most lighting installations including “Big” white applications such as street lighting and image projection systems.
The importance of LEDs to the future of the lighting industry is simply demonstrated with the major lighting manufacturers positioning themselves to exploit the technology before 2010.
Lighting companies such as Philips finally took full control of LED specialists Lumileds whilst GE Lighting acquired the remainder of GELCORE paving the way for LED lighting to become the main lighting technology of the future.
The Global Lighting Market in 2006 The lighting market in 2006 is estimated by the Freedonia Group to be in excess of $102
Billion with over 75% of the value retained in lighting fixtures as shown in Figure 1. The market is expected to continue to grow at between 3.5 – 5% growth rates to 2020 giving a market size of more than $172 billion. Two of the most significant drivers in the market will be the predicted growth of the world’s population from approximately 6.5 Billion people to more than 7.6 Billion people by 2020 and the lighting needs of developing nations.
The lighting fixture market can be split geographically with North America, Western Europe, Japan / China and the Rest Of the World respectively representing approximately 25% of the market.
Current estimates by the US Department of Energy expect SSL technologies to have achieved 90% penetration of the annual lighting market by 2020 representing a market value of approximately $155 billion. The majority of the SSL market will be dominated by three
product groups:
1. General illumination - white lighting
2. Specification Grade - illumination
3. Speciality illumination -  Colour lighting

LED Market Predictions
According to iSuppli, during 2005 the market for LED emitters increased by 5.8% primarily due to aggressive reductions in pricing of High-Brightness (HB) blue and white LEDs and a deceleration in the increase of demand for LEDs within the mobile phone market. The rapid growth of mobile phones over recent years has meant strong competition with Average Selling Prices (ASPs) for blue High Brightness LEDs used in keypad backlighting declining by 26 percent in 2005 and ASPs for white LEDs employed in handset backlighting seeing a decrease of about 20 percent. It is predicted that further aggressive ASP erosions will continue during 2007 making LEDs far more attractive for SSL applications.
The growth drivers for the SSL industry are shifting from backlighting of small-screen LCDs to new applications requiring high-flux LEDs - also referred to as Ultra High Brightness (UHB) LEDs. It is predicted that the market for LEDs will have a Compound Annual Growth Rate (CAGR) of 10.6 percent through to 2011, when it will exceed $9.1 billion. A significant portion of this growth will be driven by UHB LEDs. In 2011, UHB LEDs will account for approximately 33 percent of the total LED market – up from approximately 4 percent in 2005.
The predicted market revenue of high brightness LED emitters until 2011 is shown in Figure 2.

LED Market Drivers

As discussed in the December 2005 column there are many advantages offered by LED luminaires. However 2006 has seen several strong market drivers for SSL become prevalent, including:
• Energy conservation
• The environment and the “Green” issue
• Government regulations /legislation
• A significant decrease in the price/performance ratio of LEDs
• Analogue to Digital LED transition

A rapid increase in LED efficiency
In 2006 the LED industry has focused on increasing the efficacy of white LEDs with astounding results. Last November, Nichia Corporation in Japan had just announced a white LED using a small die with efficacies in excess of 110 lumens per watt in their research labs but within just seven months the record had been increased by approximately 20% to 131 lumens per watt by Cree Inc. Although such white LEDs are only demonstrated in research labs the trend is undeniable, they are the most efficient man-made light source today!
During 2006 many lighting engineers and system designers asked the question when would they be able to purchase high efficiency white LEDs that generate 100+ lumens per package. Today, we have several high-powered, lighting class white LEDs that meet such requirements, including the Luxeon K2 from Philips-Lumileds and the XLamp 7090 XR series from Cree inc.
Figure 3, outlines the first three generations of high power LEDs in terms of typical luminous flux per LED against their efficacy in lumens per watt.
The recently launched Cree XLamp 7090 XR-E raises the bar for in-production, high-powered white LED emitters by producing an industry topping luminous flux figure of up to 95 lumens or 85 lumens per watt at 350 mA, and up to 160 lumens at 700 mA. In just one year the typical efficacy of a white LED in production has nearly doubled and LEDs are achieving efficacy levels formerly delivered only by the most efficient traditional lighting sources, including fluorescent sources. Table 1 demonstrates how the most efficient white LEDs compare to conventional light sources in terms of efficacy and total useable light from a system. It can be easily demonstrated that lighting fixtures developed with directional light output LEDs provide systems with significantly better useable light outputs than conventional lamp technologies which can witness up to 50% fixture losses of the lumens generated.
The current world record holder for white LED efficiency in research is Nichia Corporation of Japan who have produced an LED with an efficiency of 138 lm/W and a high power LED with an output of 402 Lumens at 2 Amps and an efficiency of 92 lm/W at 350mA.
As the cost of energy and energy consumption continued to rise throughout 2006 there was a significant change in consumer and Government attitudes towards energy conservation and high efficiency lighting. These trends are beginning to adapt consumer awareness and it is predicted that LEDs will become the light source of choice over the next few years despite the issue of high initial capital cost.

The environmental advantage

LEDs provide a significant advantage over conventional lighting technologies in terms of environmental issues. LEDs contain virtually no hazardous waste material such as mercury used in many gas-based lamps and their long-life characteristics significantly reduce the disposal of light sources or fixtures at the end of their lives. Indeed, many governments are already starting to favour highly efficient light sources through a variety of policies that essentially mark the end for the majority of conventional light sources.
For example, in Europe environmental regulations include:
• RoHS is the acronym for
Restriction of Hazardous Substances and restricts the use of specific hazardous materials found in electrical and electronic products. All applicable products in the EU market after July 1, 2006 must pass RoHS compliance. The substances banned under RoHS include lead (Pb), mercury (Hg) and cadmium (Cd) which are hazardous to the environment, pollute landfills, and are dangerous in terms of occupational exposure during manufacturing and recycling.
• WEEE stands for Waste
from Electrical and Electronic Equipment and mandates the
treatment, recovery and recycling of electric and electronic equipment. All applicable products in the EU market after August 13, 2006 must pass WEEE compliance.

There are numerous countries working on their own version of RoHS including:
• RPCEP (Regulation for Pollution Control of Electronic Products): China. Goes into effect July 1, 2006
• JGPSSI (Japan Green Procurement Survey Standardization Initiative): Japan. Goes into effect July 1, 2006
• SB20 (Electronic Waste Recycling Act of 2003):California, USA. Goes into effect January 1, 2007
• Adopting the EU RoHs Directive: Australia, Canada, Korea, Taiwan

In California, new legislation such as Title 22 covering hazardous waste will no doubt change the mindset of consumers to not simply dispose of their traditional light bulbs. Current guidelines for disposing of hazardous waste illegally include sentences of up to 1 year in prison and/or $100k fine.
From October 1, 2005, the California Energy Commission introduced a new set of standards for residential lighting known as Title 24 standards. These standards relate to new and remodeled homes in California, and aim to reduce lighting energy consumption by requiring the use of new energy-efficient technologies. Table 2 (below) shows the minimum lamp efficiencies required for inclusion in the new standards and today LED technology can comfortably meet such requirements.

The LED emitter roadmap
As discussed last year there are three main approaches for generating light from LEDs including:
1. Small chip packages (~300 um x 300um)
2. Large chip packages (~mm x mm)
3. Multiple chip packages (~10’s mm x 10’s mm)
During 2006 there has been a definitive trend towards high-power large chip packages with the majority of manufacturers developing new products such as the Luxeon K2 (see figure 4), Cree Xlamp and Osram Golden Dragon based upon single large dies.

Ultra high power LEDs
However, during 2006 the numbers of new multi-chip developments have increased significantly creating an ultra high power (UHP) class of LEDs catering for compact high luminous flux output applications. These UHP LED emitters are finding applications in task lighting, high-specification down lighting for offices and hotels and high brightness image projection systems.
The OstarTM from OSRAM was one of the first UHP white LED emitters developed by a leading LED manufacturer providing two variants of 10 W and 15W. The 15W version shown in figure 5 contains 6 LED dies packaged tightly together to provide more than 420 lumens output in a 120 degree beam angle. The Ostar™ package has a low thermal resistance at less than 4 K/W and features a colour temperature of 5600 K (daylight white).
UK Company, ENFIS, has recently launched the Quattro LED light engine series in both single and multi-coloured versions. The multi-coloured light engine is available in 200W or 400W versions and the LED array emits light in an area of just 40mm x 40mm using 4 colours, Red, Green, Blue and Amber. The 200W unit, shown in figure 6, operates from 48V DC has a very low thermal resistance (<0.4°C/W) whilst emitting 3500 lumens at 25°C ambient temperature and containing integrated thermal feedback control.
Taiwanese manufacturer, Edison Opto Corporation, is taking a lead on developing cost effective white UHP LEDs with the recent announcement of a single 50W white LED in a package size of just 25mm x 25mm. The 2500 Lumen output LED is stated to achieve 50 lumens per watt efficacy at a correlated colour temperature of 6500K by its launch in the first quarter of 2007. The new 50W Edipower emitter shown in figure 7is aimed at architectural, street and commercial lighting applications. Today, Edison’s 5-20W LED emitters are incorporated into architectural products such as the MR16 equivalents shown in figure 8.
The future for UHP LEDs appears to be very bright according to Edison’s roadmap of UHP development revealed in figure 9. It is forecast that by the end of 2010, only four years away, the efficacy of White UHP LEDs will reach 140 lumens per watt and the price for 10 lumens
will be just two pence!

LED drivers and total system efficiencies
It is important to understand that LED efficacy alone does not provide a highly efficient lighting fixture so care must be taken in order to maximise the conversion of energy into useable light.
The overall efficiency of a fixture can be simply described as shown in formula 1, where System‘Total’ is the total efficiency of the LED system, Driver‘eff’ is the total efficiency of the LED power driver circuits, Fixture‘eff’ is the efficiency of the lighting fixture and Cable‘eff’ is the efficiency of the connectors and cables connecting the fixture to the power source.
LED fixture efficiencies are variable according to the power applied to the LEDs and the ambient temperature however it can be determined by measuring the efficiency of the LEDs and optics under constant power and thermal loads.
Recent developments in the design of new LED drivers such as the iDrive™ from Radiant Research has meant that driver efficiencies are now approaching 90% irrespective of the type or number of LEDs used within a lighting fixture. Many LED drivers in the market have low efficiencies between 70-80% so it is important to specify highly-efficient LED drivers along with quality designed fixtures.

Lighting fixture design trends
During 2006 there were clearly two types of LED lighting fixture designs emerging within the marketplace these being:

1. Intelligent remote LED drivers controlling multiple low cost fixtures
2. Lighting fixtures with intelligence built-in

The first types of fixtures are very simple to manufacture and contain no driving circuits so tend to be lower in cost and usually several fixtures are controlled from a single driver unit. Many manufacturers in the UK have followed this path such as Tryka LED, Crescent Lighting, Solar GB, iVision and Dialight Lumidrives to name but a few.
The second type of lighting fixtures incorporate drivers within the lighting fixture and although generally more expensive they have the benefit of providing optical feedback to ensure the lighting fixture maintains a steady light and colour (or colour temperature) output. These systems are preferred by North American companies such as Avago and TIR Systems.
LEXEL™ from TIR offers a fully integrated LED-based light source that utilises full feedback control of LED fixtures to provide exact CCT settings within a range of 2700K – 6500K and full dimming capabilities without any CCT variation. As shown in the schematic of figure 10, the LEXEL™ system incorporates thermal management systems, an optical sensor feedback system for precise intensity and colour control and an integrated LED power control system.
The development of the Avago ADJD-J823 closed loop optical feedback controller shown in figure 11 is ideal for precise colour control of RGB LED lighting fixtures. The system incorporates a CMOS mixed-signal controller with an integrated RGB photosensor that samples the light output from an LED array, processes the colour information and adjusts the light output from the LED array until a desired colour is achieved. The integrated controller can maintain the fixture’s light and colour output over time and temperature ensuring perfect control. This solution is the first of its type to be fully integrated into one single package and could pave the way for LED lighting fixtures that provide precise and controllable CCT solutions.

This was a vital year for the development of LEDs and Solid-State Lighting fixtures and even the most sceptical of lighting engineers now have to admit that LEDs are a significant lighting source that is here to stay. The number of LED products shown at major lighting exhibitions in 2006 expanded exponentially and most lighting companies will have started or expanded their LED-based fixture developments.
The pace of LED technology development has increased significantly over the last twelve months resulting in LEDs becoming the most efficient man-made light source available today. The pace of development will continue unabated during 2007 and I predict the development of the first 150lm/W white LED and the first 200+ lumen from a single LED!
As environment and green issues continue to be at the front of consumers, government and companies minds the energy-efficient and environmentally friendly LED will no doubt be the light source of choice. Indeed, the LED lighting industry should now begin working together to ensure standards are created for LED products to enable governments to provide robust legislation that essentially assigns conventional light sources to the history books.


Figure 1

Figure 1: The Global Lighting Market in 2006


Related Articles
  • Figure 2

    Figure 2: LED market revenue forecast


  • Figure 3

    Figure 3: A new lighting class of single LED emitters


  • Table 1: Comparing LEDs and conventional light sources


  • Table 2: California Title 24 ratings for high efficacy luminaires


  • Figure 4

    Figure 4: Schematic of a Luxeon K2


  • Figure 5

    Figure 5: The 15W UHP white OSTARTM LED


  • Figure 6

    Figure 6: The 200W Quattro LED array from ENFIS


  • Formula 1

  • Figure 7

    Figure 7: The new 50W Edison Opto white UHP LED delivering 2500 lumens


  • Figure 8

    Figure 8: The Edison 5W MR16 lamp with integrated reflector, heat sink and driver


  • Figure 9

    Figure 9: The road map for white UHP LEDs demonstrates how LEDs will be more cost effective and efficient than all conventional lighting sources by 2010


  • A schematic of the LEXEL system


  • Figure 10b: The Tempura track light from Zumtobel incorporating the LEXEL design


  • Figure 11: Avago’s built in colour sensor and LED controller



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