Technology Trends of LED Driver Chips for Lighting

As LEDs are further developed, their utility, or ability to produce light output from a power source, will only continue to increase. Second, LED lighting is environmentally friendly and does not require the handling, exposure, and disposal of toxic mercury vapor commonly found in cold cathode fluorescent lamps (CCFLs). Finally, incandescent bulbs often need to be replaced after about 1,000 hours of use, while fluorescent bulbs can last up to 10,000 hours. However, these numbers pale in comparison to the more than 100,000 hours of life that LED lighting can provide.

　　Heat dissipation, reliability and safety regulations need to be considered

　　As we all know, the working environment temperature of LED driver modules is relatively high, and the heat dissipation conditions of the modules are relatively poor, which causes the LED driver circuit to operate at a relatively high temperature all the time. This will lead to a series of problems such as reduced reliability and shortened service life of LED applications. Therefore, heat dissipation has to be considered as a key consideration. Reliability and safety regulations are parts that are easily ignored intentionally, especially before the relevant regulations are enforced. In order to reduce costs, some LED lighting manufacturers will omit reliability and safety circuits. However, this is precisely the foundation for the long-term development of the LED lighting industry, and it is also a reflection of the design capabilities of LED driver chip manufacturers. The solutions provided by different chip manufacturers vary greatly in the cost of adding this part of the circuit.

　　Yu Zhongwei, product director of Macroblock Technology Co., Ltd. in Taiwan, believes that we should pay attention to the trend of standardization, such as the US Energy Star and Japan PSE specifications. In addition, the dimming function is becoming more and more important, such as traditional thyristor dimming, 1~10V dimming, and DALI dimming. Finally, the requirements for driving solutions derived from solving the heat dissipation problem, in addition to cost considerations and lighter requirements, must also take into account better electrical characteristics (efficiency, power factor, electromagnetic interference, output ripple, etc.).

　　LEDs require a wide range of power conversion and drive solutions

　　Lin Zhiyan, technical marketing manager of ON Semiconductor Lighting Market, said that LED is essentially a low-voltage device. Depending on the color and current, its forward voltage drop may vary between 2 and 4.5 V, and LED needs to be driven with a constant current to ensure the required luminous intensity and color. At the same time, LED applications are diverse and require different power supplies, such as high-voltage AC-DC, medium-voltage DC-DC, and low-voltage DC-DC.

　　This requires the use of appropriate power conversion and LED drive solutions to drive LEDs according to specific application requirements, such as switch-type drivers, linear drivers, linear constant current regulators (CCRs), as well as high-voltage switching power supply solutions, power factor correction (PFC) controllers, and even novel lighting management integrated circuits (LMICs) to meet specific application requirements, provide high energy efficiency and high reliability, and help maximize the long life advantages of LEDs.

　　Macroblock also believes that the market is no longer blindly pursuing "one-stop" solutions, but understands that there are conflicts between various characteristics. For example, under the traditional single-stage output architecture, the power factor and output ripple cannot be optimized at the same time and must be compromised. Therefore, Macroblock's strategy is to propose different solutions for different customer needs. In terms of architecture, when the market has been unilaterally inclined towards isolated solutions in recent years, Macroblock believes that the irreplaceable advantages of non-isolated architectures in specific applications cannot be ignored, so it continues to develop diverse products. In addition to active power factor correction products, thyristor dimming and four-stage dimming products that have been successfully put into service, Macroblock is also actively working towards more cost-effective solutions.

　　Offline power drive promotes application

　　Tony Armstrong, director of product marketing for Linear Technology's Power Products Division, said that especially when driving HB (high brightness) LEDs, Linear Technology's LED driver ICs can provide sufficient current and voltage for many different types of LED configurations by using a conversion topology that meets the input voltage range and the required output voltage and current requirements.

　　Specifically, driving LEDs with only offline power supplies can lead to exponential growth in applications, as this form of power is readily available in both commercial buildings and residential buildings. Although replacement accessories for LED lamps are relatively simple and easy for end users to install, new requirements for LED driver ICs have been greatly increased. Since LEDs require a well-regulated constant current source to provide constant light output, powering LEDs with AC input power requires some special design methods to meet some very special design requirements. To this end, Linear Technology recently launched an innovative offline single-stage active power factor correction (PFC) isolated flyback LED controller, the LT3799.

　　Compatibility and integrated control are the highlights

　　Lance Zheng, marketing director of Marvell Green Energy Division, pointed out that in 2011, the entire lighting market grew by more than 40%, and 2012 became a key year for the LED market to take off. Compatibility and integrated control will become the two highlights of technology development.

　　First of all, compatibility. The existing lighting architecture is based on traditional lighting technology, such as incandescent lamp technology. Due to space constraints, if these bulbs and configurations are to be replaced, LED lamps need to use bulbs of the same specifications in order to match the lighting control equipment (such as the already configured TRIAC dimmer). In order to cope with this problem, the area of ​​the driver circuit board in the bulb needs to be reduced, and at the same time it needs to be compatible with various dimmers.

　　The second is integrated control functions. By adding wireless control technology to the LED drive circuit at a very low cost, new features such as color temperature adjustment, mode lighting, scene control, etc. These cool features are based on LED technology and help increase user acceptance of LED lighting technology.

　　The era of cognitive lighting is coming

　　Sajol Ghoshal, director of sensor-driven lighting at Austrian Microelectronics, pointed out that the main factor driving the continuous development of LED lighting technology is regulations. At present, building new power plants has become very expensive, so in the next decade, governments around the world are looking for ways to significantly reduce energy consumption. A high proportion of energy consumption in a building comes from lighting. Therefore, new regulations that force the reduction of energy consumption will affect the design and installation of lighting systems. The European Union is planning to phase out inefficient light bulbs and has also formulated regulations for commercial lighting.

　　Historically, lighting has been a crudely controlled electrical load that is manually controlled with a simple switch, but can be further refined. For example, California Assembly Bill 32 requires buildings to reduce their energy consumption by half by 2018. Other building codes, such as California Title 24, have even more specific requirements, such as requiring daylight capture through windows and skylights to reduce energy consumption, and requiring buildings to be equipped with automatic lighting control systems. Currently, low-cost passive infrared detectors are rarely used in rooms. Controlling lighting through building systems can greatly reduce energy consumption and provide users with highly optimized lighting to improve comfort experience. From this point of view, there is obviously still a long way to go.

　　Therefore, it will be a major trend to realize lighting control in the next generation lighting system by taking advantage of LED power supply and flexibility. This solution enables the lighting system to adjust the brightness and color of the LED itself according to environmental changes to meet environmental needs. For example, when there is enough daylight in the room or the room is unoccupied for a long time, this method can automatically reduce a lot of energy consumption.

　　Intelligent dimming solution

　　NXP Semiconductors is also an active promoter of smart dimming. Zhang Weichao, its Greater China lighting product marketing manager, said that for LED lighting driver manufacturers, the design solution needs to maximize performance, including key performance such as PFC, THD, efficiency, and output constant current accuracy, while reducing circuit board space requirements, design complexity, and system costs. At the same time, with the development of LED residential and commercial lighting applications, the demand for dimming has increased, but the thyristor dimming used in incandescent lamps will still exist, so the architecture design of the driver IC needs to face a wider range of dimming compatibility issues.

　　At the same time, future lighting solutions tend to be more intelligent dimming. Considering energy saving factors, the biggest breakthrough in the field of lighting is to improve the application mode of lighting, that is, intelligent, wireless lighting control, or "smart lighting". Smart lighting marks a fundamental change in our relationship with light - whether at home, in the office, or even outdoors. Using a secure, small, and low-cost solution to link wireless IP with energy-efficient lighting technology can transform the way we design, control and manage lighting. For each bulb with an IP address, this complete hardware/software solution can achieve inter-IP connectivity, so that an advanced lighting system that can be easily controlled by smartphones, tablets, and personal computers can be established.

　　Smart lighting network, including lamps, switches, sensors, remote control, and optional IP control through smartphones, tablets and PC network management. These lamps can be controlled by network IP through JenNet-IP stack protocol based on 6LoWPAN.

　　Compared with traditional control solutions, JenNet-IP SW stack allows the system to be controlled by smartphones, tablets and PCs. These functions can be realized through low-cost gateways, which can be controlled via the Internet or via a local area network (LAN). The chip iCFL or iSSL solution is suitable for home users to professional users with management systems.