The future prospects of LED lighting and its driving technology

Solid-state lighting (SSL) or light-emitting diode (LED) lighting is the obvious replacement for incandescent and FL/CFL lighting, driven by government regulations, high efficiency, long life, and environmental concerns. As governments continue to phase out incandescent bulbs (e.g., Europe mandates a ban on 100W bulbs by the end of 2009 and 75W bulbs by the end of 2010), the only options left are CFL bulbs and LED bulbs, which contain trace amounts of mercury, but unfortunately, LED bulbs still cost much more than incandescent or CFL. In addition, LED bulbs are RoHS compliant and contain no mercury or other hazardous substances—better for the environment.

However, this goal will be driven by major companies, for example, IKEA announced that they will first phase out incandescent bulbs and only supply CFL and LED bulbs in the future. Another point to note is that the price of LEDs will slowly come down on its own, effectively reducing the total LED bulb price. This will allow consumers to replace their old bulbs with longer-lasting, more environmentally friendly LED bulbs. As the replacement rate of LED bulbs accelerates, we can foresee that more features will be built into these bulbs in the future, which will change the way we use lamps in our daily lives. Traditional incandescent bulbs basically have a unique correlated color temperature (CCT) due to the heating and cooling of the tungsten filament.

With a dimming device, this CCT varies between orange-red when dimmed deeply and bright white at full power (no dimming). With LEDs, different types of colored LEDs can be combined to produce colored light to provide a CCT similar to an incandescent bulb, or any CIE 1931 chromaticity diagram color as shown in Figure 1. In addition, we can add features such as remote/wireless control for dimming, grouping, and changing the color of the light output of these bulbs - and this is just the beginning.

Figure 1 CIE 1931 Chromaticity Diagram: The black curve reflects a light bulb using a tungsten filament

It’s not just the home market that benefits from LED lighting. According to a 2008 report by the United States Department of Energy, if all U.S. retailers switched to LED systems to illuminate refrigerated display cases, “… 2.54 billion kilowatt-hours of electricity could be saved. This is equivalent to saving 273.8 TBtu of energy, which is equal to the annual coal consumption of four large thermal power plants, or the annual electricity consumption of more than two million households.” The trend of switching to LED lighting has been going on for some time, and many large retail companies are gradually adopting LED lighting. For example, Wal-Mart announced in December 2009 that it would replace ceramic metal halide lamps with LEDs in 650 stores; by the end of 2010, more than 500 stores’ display cases would be switched to LED lighting, in order to achieve the goal of saving 16 million kilowatt-hours of electricity per year.

SuperMax, located in Puerto Rico, is replacing all of its store lighting with LED-based lighting technology. According to a recent white paper released by Nualight, fluorescent lighting increases power consumption by about 25%-50% in some applications such as refrigeration equipment, including display cabinets, refrigerators, cold storage and automatic beverage vending machines. In fact, LED lighting is ideal for these low-temperature display equipment because LEDs generate very little heat in comparison. Therefore, they consume very little energy to provide the same or even better lighting, while having no significant impact on the compressor and without the need for excessive heat dissipation of the refrigeration unit. In addition, the use of LED lighting in the freezing and refrigeration of food also eliminates the potential risk of mercury contamination caused by broken fluorescent bulbs.

LED colors can be adjusted to match the type of display, and the life of LEDs far exceeds that of refrigerators. As early as 2008, Naulight signed a contract with Tesco to transform 115 of its Irish stores, and has transformed its stores in the UK and its Tesco US store Freshandeasy. In the UK, Sainsbury's has installed LED lighting systems in more than 15,000 refrigerated display cabinets in all its UK stores.

In addition, the outdoor and infrastructure markets are also moving from traditional lighting equipment LPS, HPS and mercury vapor to LED-based lighting solutions. LEDs have many advantages, such as: brightness adjustability, instant turn-on (no warm-up time to reach maximum brightness output) and low maintenance. Many innovative pilots are being carried out around the world to upgrade parking lot lighting, street lights and traffic lights. With the help of US government stimulus funds, some cities have installed LED street lights in 2009, and dozens of other cities are planning to do so. At least 30 cities have applied for more than $104 million in federal stimulus funds to help them implement the above lighting upgrades. In 2009, the European Commission passed a regulation aimed at effectively phasing out traditional office, industrial and street lighting fixtures, which will have a huge impact in 2012. The specific contents are as follows:

2010: Phase out of halo-phosphate fluorescent tubes

2012: Phase out of T12 fluorescent (FL) lamps

2012: Phase out of High Pressure Sodium (HPS) standard quality lamps (only E27/ E40/ PGZ12 affected)

2012: Phase out of low-efficiency metal halide (MH) lamps (only E27/E40/PGZ12 affected).

Europe's goal is to reduce energy consumption by 20% by 2020, and the European Commission announced a plan in February 2011 to raise 10 million euros to implement two or three major large-scale projects to demonstrate the many benefits of LED lighting in terms of light quality, low energy consumption, low total operating costs and user acceptance.

While governments are playing an active role in promoting the adoption of more efficient lighting devices such as LEDs, if we really want to accelerate the promotion and application of LED lighting in the general lighting market, we need to achieve three important technological breakthroughs.

First, the cost of drivers needs to be reduced to achieve mass consumption of LED bulbs and lamps in the general lighting market. Many LED chip and power IC suppliers are studying how to reduce the cost of their LED chips or driver ICs little by little through new or improved technologies, with the goal of providing higher efficacy (higher lumens/watt) at a lower price.

Secondly, LED drivers need to be developed that can seamlessly interface with the currently installed power infrastructure. We have already encountered this problem with “dimmable” LED bulbs, which need to work correctly with phase-breaking dimmers such as leading edge (TRIAC-based) and trailing edge (transistor-based), digital dimmers, and motion sensors. MR16-type LED bulbs need to be compatible with the currently installed magnetic electronic transformers (dimming), while also being compatible with LED bulbs that consume less power than traditional halogen MR16 bulbs. There are considerable challenges in maintaining high efficiency in the bulb itself while also meeting the minimum power consumption requirements of the electronic transformer (eTransformer).

Finally, LEDs offer a very high level of flexibility compared to their incandescent and CLF counterparts. However, smart control technology for LED lighting needs to be developed to truly maximize the value of this technology. This ranges from smart dimming of LED bulbs for home or office use, which adjusts the brightness based on how much light enters a room, or changing the brightness of street lights based on the time of day (dawn, dusk, night). Another advantage of LEDs is their ability to turn on instantly, so there is no "warm-up" time requirement compared to currently used equipment such as stadium lighting.

TI is committed to serving this important growth market. For example, TI has a business unit dedicated to LED lighting for the general lighting market. The main challenge facing TI and its competitors is that this market is still in its infancy, so it is full of turmoil, confusion and constant change. One of the main problems in this market now is that the requirements in different regions of the world are more or less different, such as: input voltage, power factor, electromagnetic interference (EMI), rating standards, cost, etc. This means that as a manufacturer of power controllers and converter ICs, it is difficult for us to achieve theoretical economies of scale because the industry is simply unable to develop a truly universal LED bulb (at least not in the short term). However, with some traditional competitors and many new entrants to the industry, competition has become very fierce, and this situation will accelerate the emergence of new solution products for this market.

The benefits of this fierce competition in the market are the emergence of innovation and cost reduction, which are the two key factors driving the development of this emerging market. Before the market is unified, the winners of the competition will be those who find and invest in the right market segments, and eventually there will be only a few large companies dominating the market. TI focuses on the development of products tailored for LED lighting, which also have a high degree of flexibility and can quickly adapt to the changes in the requirements of various LED lighting market segments. This market is still in the early trial application stage and will explode in the next two to three years. The products currently being developed by TI and the capacity investment being implemented will make TI a leader in this exciting and growing market. It can ensure that TI's customers will succeed in the competition in the LED lighting market.