LED applications are like the morning sun
If there are some bright spots in the sluggish semiconductor industry, LED light sources and their drivers can be considered one. Especially in the 2008 Beijing Olympics, the dazzling LED light show amazed the world and put a perfect exclamation mark on China's LED display technology.
The recent years have been a growth period for the development of LED, and there are several major types of applications: 1. LED lighting applications are like the sun rising slowly at six or seven o'clock in the morning. LED lamps are green, energy-saving, and long-life. The power of outdoor lighting comes from the government's energy-saving and environmental protection policies, and advertising lighting comes from companies paying for it. Therefore, the demand is huge and the development is considerable; indoor lighting is a massive product needed by thousands of households. With the further reduction of LED costs, the development potential is huge. 2. LED backlight applications involve portable products such as mobile phones, MP3s, NB (laptops) used in people's daily lives, to LCD screens of large consumer electronics such as TVs. 3. LED automotive lighting, mainly for front and rear lights, especially the rise of high-efficiency cars, has heated up. In addition, there are special applications such as industrial lighting and camera flash.
Therefore, the semiconductor industry’s LED light source and its driver IC technology have developed rapidly. Currently, the world’s major patent holders of white LED light sources are Japan’s Nichia and TG, the United States’ Cree, and Europe’s Philips and Osram [1]. The LED industry has also entered our field of vision without us noticing, creating many new manufacturers. For example, Lighthouse (Zhaoguang Technology) has only been established for 11 years and has become the world’s leading supplier of LED display screens. my country’s well-known LED display screen manufacturer Beijing Leyard used 570,000 driver chips from Taiwan’s Macroblock Technology, the MBI5030, for the opening ceremony of the Beijing Olympics. Companies such as Seoul Semiconductor, Diodes Zetex (Note: Diodes acquired Zetex), and Leadis are also growing stronger.
Figure 1 Photo source: Beijing Leyard
"China's LED market is still relatively fragmented, mainly concentrated in signage, signal, mobile and lighting applications. China's LED market share is still relatively small, but it has maintained a very fast growth rate in the past few years." Billy Han, global marketing director of optical materials for Dow Corning Electronics Industry, said, "The LED industry is developing very rapidly, especially in the field of lighting, and cost competitiveness is very important. In view of this, it is expected that China's LED industry will continue to grow at a rate higher than the industry average."
Photo: Billy Han, Global Marketing Director, Optical Materials, Electronics Industry, Dow Corning
Four driving forces of lighting
@Environmental protection and energy saving
LEDs are mainly used in street lamps and general lighting. Because LEDs are 20 times more energy efficient than incandescent lamps and 5 times more energy efficient than fluorescent lamps. "Traditional tungsten filament lamps, high discharge current bulbs (HID) and cold cathode fluorescent lamps (CCFL) will be phased out and replaced by LED lamps with lower energy consumption and less pollution," said He Xianbin, general manager of National Semiconductor (NS) China. Because LEDs do not contain any hazardous materials, unlike CFLs that have toxic mercury vapor inside their tubes, they are "green and environmentally friendly."
Photo: He Xianbin, General Manager of NS China Business
The U.S. Department of Energy points out that the energy consumed by lighting accounts for 22% of the annual electricity generation in the United States, so the energy saving effect of LED is quite significant. The widespread use of LED lighting will reduce this energy consumption by 50%. If this is taken into account objectively, by 2027, the annual energy consumption reduction achieved by LED lighting will be equivalent to 500 million barrels of oil, while also reducing carbon dioxide emissions.
@LED light output
High-power LEDs have already achieved a milestone of 100 lumens per watt, with some manufacturers even claiming 120 lumens per watt. This means that LEDs are now energy efficient, surpassing CFLs (which have an output of 80 lumens per watt). It is predicted that by 2012, LEDs will reach 150 lumens per watt.
LED cost reduction
"Price is a key factor, especially in the Chinese market," said Liang Houquan, technical marketing director of Asia Pacific at Diodes Zetex. Robert L. Lucas, marketing manager of Intersil's industrial and communications power supply division, said that at present, a single LED for lighting costs $2 each, and in comparison, the price of LED drivers is not expensive. If there is an opportunity to significantly reduce the price of LEDs, the problem of LED popularization can be easily solved. Power Integrations (PI for short) feels the same way. Doug Bailey, vice president of marketing, believes that the main obstacle facing the general LED lighting market is that it cannot prove that its total cost of ownership (TCO) is competitive with other lighting products (incandescent lamps, halogen lamps, LFL/CFL, etc.). If your product has a very long service life (35-50-100K hours) and uses an efficient driver, then the problem is solved. A 10W LED driver with a 10% higher efficiency and a service life of 50K hours can save $10 in electricity bills. This saved cost can reduce TCO, thereby highlighting the advantages of LED lamps.
Photo: Liang Houquan, Technical Marketing Director, Asia Pacific, Diodes Zetex
Robert L.Lucas, Marketing Manager, Industrial and Communications Power Division, Intersil
Doug Bailey, Vice President of Marketing at PI
However, "the cost of LED lighting is falling very fast." Tony Armstrong, product marketing director of Linear Technology's power products division, gave an example, "Polybrite (a leading supplier of lighting products using LED technology) pointed out that in the past 12 months, the price of individual white light diodes (some of which have been adopted by LED bulbs and account for most of their costs) has dropped from $8 to $1.50. They further predict that in 2009, the price of replacing incandescent bulbs with LED bulbs will be acceptable to consumers."
Photo Tony Armstrong, Director of Product Marketing, Power Products Division, Linear Technology Corporation
@Application heating up
LED applications are mainly in lighting and backlighting, in addition, there are also automotive lighting applications.
其中大型LED显示屏增长最快。据DIGITIMES的预估,大型LED显示屏用LED产值2008年至2010年分别为11.8亿、16.4亿、23.2亿美元,年成长率分别为34.1%、39%、41.5%,可谓是LED众应用领域当中,年成长率最显著的产品。
Since the LED display screen uses a low-voltage scanning drive, it has the advantages of low power consumption, long life, low cost, high brightness, wide viewing angle, long visible distance, waterproof, and a variety of specifications. It can meet the needs of various application scenarios. Even under direct sunlight, the screen can adjust its own brightness to adapt to the needs of high-brightness environments.
In addition, the breakthrough in appearance technology will further broaden the application field of LED display screens. In terms of appearance changes, the shape of LED display screens is not limited to the traditional square; LED display screens can also be designed into different shapes according to different application needs. For example, the chain-shaped LED display screen breaks through the limitations of the traditional LED display setting place. It can be wrapped around a cylinder, laid on a curved staircase, or hung like a waterfall. At the same time, with the advancement of technology, LED display screens are also moving towards the direction of continuously reducing the pixel pitch, which will make the growth potential of LED display screens unlimited.
High-brightness LED and driving technology trends
High brightness LED (HB LED) has become a hot topic in 2009. It has been widely used in various fields recently, including LCD backlight module, automotive lighting, general lighting and semiconductor lighting. These applications make the growth prospect of high brightness LED in the next five years quite optimistic. "We estimate the average annual compound growth rate to be 20%." Billy of Dow Corning said.
The latest trend of high-brightness (HB) LEDs is high power, higher lumens/watt, and higher photoelectric efficiency. Liang Houquan, technical marketing director of Diodes Zetex Asia Pacific, explained that white or warm white high-brightness LEDs are the best choice for indoor lighting, while RGB high-brightness LEDs are suitable for decorative and mood lighting. Another market for high-brightness LEDs is the front and rear lights of cars. Although HID lamps and traditional light bulbs still dominate the market, high-brightness LED applications have the advantages of better color temperature and longer service life, so they are gradually becoming popular in China.
众所周知,高亮度LED系统的热性能是设计人员的重要考虑。这是由于LED应用与一般灯泡及低强度的3或5mm轴向LED不同,它所产生的热量非常低。灯泡也会产生大量热能,但这并不会构成任何问题。但是,高亮度LED产生过多热度时,热能需要在最短时间内散去,以避免对LED造成损害。因此,从设计的角度来讲,系统的热量问题是一项重大的挑战。梁后权说:“Diodes Zetex的高亮度LED驱动器的操作温度可维持于世界级的125℃。凭藉此优势,整体系统的可靠性能够在高操作温度下提升。这个特性是照明系统——特别是高亮度LED照明系统的必要条件。”
Since high-brightness LEDs have a lifespan of up to 50,000 hours, designers of high-brightness LED systems have been looking for reliable designs. Specific system considerations include photoelectric efficiency, lumens/watt, color temperature drift, light intensity attenuation over time, and thermal resistance of the package. In addition, designers have been looking for high-brightness LEDs with high forward voltage, high color temperature, and high intensity. These parameters play a major role in the visual function of the system. The LED driver required by the market needs to have a small, low thermal resistance package, high reliability, high efficiency, and good LED dimming functions, such as PWM and DC dimming functions with high dimming ratios.
另一项挑战可说是系统的光学设计,因为这涉及各种各样的参数,例如外壳、透镜及反射镜的用料及设计,甚至是LED的观看角度。系统的整体效率则是最终的考验。低效率的系统会造成很多问题,例如过热、缩短使用寿命、降低可靠性,更严重的问题是周边温度上升,使高亮度LED的光衰弱加深。因此,这为LED 驱动器厂商提出了挑战。Diodes Zetex称能够帮助设计人员克服这些问题,包括提供评估板、应用及设计资料、模拟模型和Excel计算器,并由经验丰富的应用工程人员为客户提供协助,可显著缩减设计周期。
A microcontroller driver is required for brightness adjustment. This is because advanced LED lighting equipment requires intelligent driving electronic technology that controls the current of the LED and monitors the equipment in real time. Because LEDs themselves cannot emit high-brightness white light like traditional incandescent and fluorescent lamps. And most of today's LED-based devices require light output that can change over time. These characteristics and requirements have caused trouble for many lighting manufacturers. "Cypress can provide special solutions to help solve these problems," said Donald Parkman, Cypress's director of public relations. "Using our software designers can easily write programs to ensure that the LED maintains accurate color and intensity output."
Photo: Donald Parkman, Cypress Communications Director
The design and production technology of DC LED light sources and their driver ICs have been increasingly improved, and the price has been declining by 20% to 30% every year, creating a good atmosphere for the widespread application of LED lamps. Yan Chongguang, a senior engineer at China Resources Siwei Technology Co., Ltd., said that AC LED is still a new product that has just started [2]. Its performance needs to be improved. The current price is still far from the civilian level. It may take several years to reach the level of today's DC LED. However, many driver manufacturers have not considered making DC LEDs. In this regard, Robert from Intersil explained that the reason why companies such as Seoul Semiconductor use AC LEDs is that the company also makes LED light sources, so it directly uses AC to drive LED solutions. However, most independent IC manufacturers still use DC driver solutions. The advantage is that AC and DC are isolated, which can protect the LED consumer end. For example, Intersil's solution can support 110-220V AC and has a maximum withstand voltage of 277V.
Photo: Yan Chongguang, senior engineer of China Resources Silicon Power
* Single LED drivers for lighting will maintain growth momentum
Since the LED driver needs to be integrated into a single lamp body, PI believes that the main requirements for the LED driver are as follows:
* Higher efficiency to reduce power dissipation within the lamp and enable the LED driver to operate at an acceptable temperature;
* Equipped with power factor correction circuit to meet the new Energy Star regulations;
* Small size to fit into the lamp housing;
* Prefer isolation design solutions, which are easier to meet safety requirements;
* Under current requirements, single LED chips for general lighting will continue to grow (making it more difficult for LED lamps to meet high energy efficiency requirements).
However, although China's current LED design activities are very active, most of the design activities are aimed at the European and American markets, not the domestic market.
Some LED drivers and dimming solutions
ON Semiconductor: Diverse LED Drivers and Dimming Chips
Including a variety of components to drive LEDs and dimming. "LED technology with ever-increasing lumens per watt will continue to move forward in 2009, and constant current drive architecture is the key to driving LEDs." said Jiang Jialiang, marketing manager of the Asia Pacific Power Management Division of ON Semiconductor. "In addition, to achieve a robust LED driver product, a system-oriented approach is needed, considering multiple factors such as light source, power conversion, LED control and drive, heat dissipation and optics."
ON Semiconductor focuses on using low voltage and high voltage technologies, as well as expertise in power management, to continuously launch leading technologies and products, such as the latest CAT3224 driver, the industry's first 4A single-chip LED driver, providing high-intensity LED flash capabilities for supercapacitor-based LED camera flash and industrial applications, in which LEDs are used to replace xenon flash.
ON Semiconductor's LED driver power solution product line meets a wide range of needs from high-voltage offline AC-DC switching power supplies to medium-voltage LED power supplies with a wide input range, as well as portable product backlight and flash drive applications.
For example, the offline PWM switching regulator NCP1014/1028, with integrated 700V high-voltage MOSFET, has features such as output open-circuit voltage clamping, frequency jittering to reduce electromagnetic interference (EMI) signals, and built-in thermal shutdown protection, which is suitable for applications such as LED ballasts, building lighting, display backlighting, sign and channel lighting, and task lights. Or replace E27/GU10 lamps.
Photo: Jiang Jialiang, Marketing Manager of Power Management Division, Asia Pacific, ON Semiconductor
China Resources Silicon Power: Will launch E27 lamp solution
China Resources Siwei has mass-produced LED driver ICs since 2006. PT4115 and PT4107 have been used by domestic and foreign customers to mass-produce various LED lamps. Since 2008, we have provided customers with DEMO boards, BOMs, and PCB board drawings for MR16, LED fluorescent lamps, LED ceiling lamps, etc. that can be directly used in the production of LED lamps; in 2009, we launched DEMO boards, BOMs, and PCB board drawings that can be directly used in the production of E27 LED lamps; and there are many new system application solutions under design, such as LED street lights, solar LED lights, etc.
Macroblock: The first LED driver with built-in 16-bit PWM
MBI5030 is claimed to be the industry's first intelligent LED driver chip with built-in 16-bit PWM. It can create a full-color display screen with up to 65,536 grayscale applications, which is sufficient to provide wide image processing capabilities and meet the high-level requirements of high-end LED displays for color performance and grayscale performance. In addition, MBI5030 improves the function of traditional PWM, dispersing the time of an image conduction into several shorter conduction times to increase the overall visual update rate, up to 7680Hz (@ GCLK=8MHz), allowing high-speed cameras to capture images without flickering when shooting.
PI: High reliability and integration
The company's ICs have extremely high reliability, with a failure rate (FIT) of about 1. PI's power ICs use on/off or multi-mode control to improve the energy efficiency level of the driver. In addition, PI products can reduce the number of external components required, thereby extending the mean time between failures (MTBF) of the driver. It is entirely possible to design a 350 mA, 12 V LED driver using only 15 external components.
ST: Solar LED Street Light
ST launched the Solar LED street light (Photo 1) in February this year and is promoting it with partners. The overall solution consists of two modules: an 85W solar charger and a 25W LED driver, which saves energy and improves lighting effects.
Photo 1: ST's solar street light solution
NS: RGB backlit mobile phone screen:
NS introduced a new technology of the company - RGB (red, green and blue) backlight driver, which replaces the usual white light driver of mobile phones. According to Huang Hanji, the marketing director of power products in Asia Pacific of NS, the disadvantage of white light backlight is that it cannot achieve pure white, so the image color is not realistic enough. The advantage of RGB is that it can achieve 100% color gamut, which can make the image brighter. And it can ensure a relatively stable effect under any conditions. In addition, white light driver also has a large energy consumption; but after RGB is added with a high-performance filter, it can achieve a good energy-saving effect. Figure 1 shows a comparison of white light LED backlight and RGB light LED backlight displays.
Figure 1 Comparison of white LED backlight and RGB LED backlight displays
Figure 2 RGB is more energy-efficient than white light backlight
Dow Corning: Silicon-based sealing materials
As an important technical goal of the LED industry, light output is extremely important. Dow Corning believes that silicone-based encapsulants (Photo 2) have great potential because of their higher refractive index (>1.5RI), which is extremely important for promoting the application of LEDs in high-performance fields.
Photo 2: Plastic moldable silicone
Silicon-based sealing materials can not only protect LEDs from the elements, but also help control light output and improve long-term stability at low to high operating temperatures (-40 to 150°C). Compared to epoxy materials, silicone-based sealing materials can withstand higher LED operating temperatures. The advantages of silicone-based sealing materials also include high light transmittance, excellent adhesion to a variety of materials, low moisture absorption, and can also meet a wider range of hardness and viscosity requirements.
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