Power modules play a key part in power saving. TM Technology's MSI sales department senior manager Alex Hor introduced their power module solutions and analyzed its technical challenges in the future.
LED lighting market
Hor first explained LEDs' characteristics and the history of lighting. He stated that LEDs save energy and enable long battery life; moreover, LEDs are mercury-free, small, rich in colors, sturdy, easy-to-control, and efficient. Hor also noted that the concept of lighting emerged in the 1800s. The candle lamp was invented in 1810. Sixty years later Thomas Edison invented the first incandescent lamp, which was popular for the next 60 years before fluorescent lights became available in 1938. In 1996, the need for next-generation lighting technology gained more attention due to the issue of global warming. Additionally, incandescent lights will be prohibited in 2012, and white light LEDs will be the mainstream, with OLED being another option.
The advance of LED technology has allowed LEDs to penetrate the lighting market. Red lights, yellow-green lights, and orange lights had been commercialized by 1990. GaN blue lights and green lights were commercialized in 1993 and 1994, respectively. White LEDs were commercialized in 1996. Commercialized white LEDs reached 100 l m/W in 2008. In 2009 Nichia displayed white LEDs with 249 lm/W.
According to Strategies Unlimited's estimates in 2009, the luminous efficacy of cool white and warm white LEDs will reach 120 lm/W and 100 lm/W, respectively, in 2010, and 150 lm/W and 130 lm/W in 2013.
Current LED lights can replace regular bulbs, candle lamps, PAR lamps, reflector lamps, mercury lamps and fluorescent lamps. Strategies Unlimited estimated its CAGR from 2008-2013 to reach 146%, 211%, 92%, 119% and 45%, with overall CAGR of 134%.
Some catalysts are driving LED lights' growth. Lighting is an elementary need of human beings, but it consumes a lot of energy. The huge costs mean significantly low energy efficiency. Moreover, lighting creates a lot of carbon dioxide. Therefore, governments all over the world have announced plans to ban incandescent light bulbs during 2010-2015, and may prohibit fluorescent lights that contain mercury. But there is an issue: we are not certain whether LED lights are good enough to replace fluorescent lights.
IEK has provided the reasons for robust sales of LED light bulbs in Japan. First, the luminous efficacy of warm white LEDs has increased to 97 lm/W from 83 lm/W, and cool white LEDs to 147 lm/W from 132 lm/W. Moreover, the price of LED lights has dropped from 9,000 yen to 2,000-3,000 yen. Additionally, the rise of environmental consciousness, higher electricity rates, (2.5 times that of Taiwan), recognition of LED lighting's advantages, and government support have all helped drive sales of LED light bulbs.
LED lighting power solutions
When we analyze LED lighting's cost structure, we will find thermal components make up 30%, power supply 20%, assembly 5%, and LED components 45%, the most expensive of all. The US Department of Energy expects the price of LED light bulbs to decline 15%-20% yearly, or even faster, so that they can replace conventional lighting devices in 2012-2015.
Power modules play a key role in LED lighting's power-saving. The basic requirements concern the difference in input and output voltages, maximum output voltage, efficiency under different power sources, load and temperatures. The HV LED is a possible trend; its working environment is related to its life cycle (decided by the environment) and operating temperatures. Related technologies include the measurements of PFC and driver systems. Its protection functions address power surge and over-voltage, as well as extra protection. Compatibility involves special dimming systems and ambient light sensors.
There are two kinds of power module solutions: linear and switching. The advantages of linear solutions are: free from the electromagnetic compatibility (EMC) problem, fewer external components, higher current stability and smaller size. Its disadvantages are: lower efficiency, heat problems, and more restrictions on design. The advantages of switching modules are: higher efficiency and higher current stability; and its disadvantages are more external components, difficult to design, larger in size and problem with EMC. TM Technology has combined the advantages of linear and switching modules to provide four solutions: mobile solutions, switching solutions, isolated solutions and non-isolated solutions for different LED lighting markets.
The challenges of LED lighting technology
LED lights have encountered many challenges, including higher prices, difficulty in designing its power management and driver ICs, temperatures, product reliability, quality and education of clients.
LED lighting power management also faces a lot of challenges in terms of EMC, and the efficiency and size of power modules. For example, LED lighting modules with built-in PSR and power MOS will effectively reduce the adoption of peripheral parts and the size of the circuit. LED lighting module makers also need to consider dimming technology. Designers should weigh the pros and cons and see how they can integrate the different dimming technologies of TRIAC, ON/OFF, and PWM.
Passive power factor adjustment can now reach 0.8 from the previous 0.9. The structure is simple, the price is low, and the operating frequency is the same as power supply. But passive components are big and heavy, and they have to be designed according to specific input voltage and load conditions. TM Technology can provide passive valley-fill filter to adjust its overall power factor, so that the LED driver's power factor can reach beyond 85%, in order to achieve the goal of energy saving. TM Technology's upcoming driver will adopt active power factor adjustment, with its overall power factor to surpass 95%. TM Technology expects its latest products to be more environmentally friendly.
TM Technology's MSI sales department senior manager Alex Hor
Photo: Digitimes, October 2010