Technology trends of LED driver chips for lighting

With the further development of LEDs, their utility or ability to generate light output from power sources will only continue to increase. Second, LED lighting is environmentally friendly and does not require handling, exposure, and disposal of toxic mercury vapors common in cold cathode fluorescent lamps (CCFL). Finally, incandescent bulbs often need to be replaced after about 1,000 hours of use, while fluorescent lamps can last up to 10,000 hours. However, these figures pale in comparison to LED lighting that can provide a lifespan of more than 100,000 hours.

Heat dissipation, reliability and safety regulations need to be considered

As we all know, the operating temperature of the LED driver module is high, and the heat dissipation conditions of the module are poor, resulting in the LED driver circuit always working at a higher temperature, which will lead to a series of problems such as reduced reliability and shortened service life of the LED application Have to focus on consideration; reliability and safety regulations are easily overlooked, especially before the enforcement of the relevant regulations, in order to reduce costs, some LED lighting manufacturers will omit reliability and safety regulations; but this is precisely Whether the LED lighting industry can develop for a long time is also a manifestation of the design capabilities of LED driver chip manufacturers. The solutions provided by different chip manufacturers greatly increase the cost of increasing this part of the circuit.

Yu Zhongwei, product director of Taiwan's Juji Technology Co., Ltd., believes that the trend of standardization should be noted, such as the US Energy Star and the Japanese PSE regulations. In addition, dimming functions have received increasing attention, 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, lighter requirements, and also must take into account better electrical characteristics (efficiency, power factor, electromagnetic interference, output ripple, etc.) .

LED needs rich power conversion and driving solutions

Lin Zhiyan, technical marketing manager of ON Semiconductor's lighting market, said that LEDs are essentially low-voltage devices. Depending on the color and current, the forward voltage drop may vary from 2 to 4.5 V, and the LED needs to be driven with a constant current. Make sure to provide the required luminous intensity and color. At the same time, LED applications are diverse and require different power sources for power supply, such as high-voltage AC-DC, medium-voltage DC-DC, and low-voltage DC-DC.

This requires the use of suitable power conversion and LED drive solutions to drive LEDs according to specific application requirements, such as switching drivers, linear drivers, linear constant current regulators (CCR), and high-voltage switching power supply solutions, power factor correction (PFC ) The controller, or even a novel lighting management integrated circuit (LMIC), to meet specific application needs, provide high energy efficiency and high reliability, and help to play the advantages of LED long life.

Accumulation Technology also believes that the market no longer blindly pursues a "one-time satisfaction" solution, but understands that there are conflicts between various characteristics. For example, under the traditional single-stage output architecture, power factor and output ripple cannot be optimized at the same time and must be made. compromise. Therefore, Accumulation Technology's strategy is to propose different solutions for different customer needs. In terms of architecture, when the market has favored isolated solutions unilaterally in recent years, Jiji believes that the non-isolated architecture has no irreplaceable advantages in specific applications, so it continues to develop a variety of products. At present, in addition to active power factor correction products, thyristor dimming and four-stage dimming products have been successfully in service, Accumulation is also actively working towards higher cost-effective solutions.

Offline power drive to promote application

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

Specifically, driving LEDs with an offline power supply can exponentially increase the application, because this type of power supply can be obtained very conveniently no matter in commercial buildings or residential houses. Although the replacement device for LED lights is relatively simple and easy for the end user to install, the new requirements for LED driver ICs have greatly increased. Since the LED requires a well-regulated constant current source to provide a constant light output, using AC input power to power the LED 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, LT3799.

Compatibility and integrated control become highlights

Marvell Green Energy Marketing Director Lance Zheng 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 two highlights of technological development.

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

The second is the integrated control function. At a low cost, adding wireless control technology to the LED driver circuit can bring new features, such as color temperature adjustment, mode lighting, scene control, and so on. These cool features are based on LED technology, which helps increase user acceptance of LED lighting technology.

The era of perceived lighting is coming

Sajol Ghoshal, director of the Austrian microelectronics sensor-driven lighting department, pointed out that the main factor driving the continuous development of LED lighting technology is regulations. Currently, the construction of new power plants has become very expensive, so over the next decade, governments around the world are looking for ways to significantly reduce energy consumption. In a building, a very high proportion of energy consumption comes from lighting. Therefore, the new regulations that forcibly reduce energy consumption will affect the design and installation of lighting systems. The EU is planning to phase out inefficient light bulbs, and regulations have been formulated for commercial lighting.

Historically, lighting is a rough-controlled electrical load, which can be further refined by manual control with a simple switch. For example, the California State Council Act 32 regulations require buildings to reduce energy consumption by half by 2018. Other building regulations, such as TItle 24 in California, have even made 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. At present, low-cost passive infrared detectors are rarely used in rooms. Controlling lighting through building systems can greatly reduce energy consumption and bring users highly optimized lighting to improve the comfort experience. From this perspective, there is obviously a long way to go.

Therefore, using the advantages of LED power supply and flexibility, the realization of lighting control in the next generation lighting system will be the main trend. This solution enables the lighting system to adjust the brightness and color of the LED itself to meet the environmental needs according to changes in the environment. For example, when there is enough sunlight in the room or the room is unattended for a long time, this method can automatically reduce a large amount of energy consumption.

Intelligent dimming solution

NXP Semiconductors is also an active promoter of smart dimming. Zhang Weichao, the lighting product marketing manager for Greater China, introduced that for LED lighting driver manufacturers, the designed solution needs to improve performance to a greater extent, including key performance such as PFC, THD, efficiency, and output constant current accuracy, while reducing circuit board space requirements , Reduce design complexity and system cost. 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 driver IC architecture design needs to face a wider range of dimming Compatibility issues.

At the same time, future lighting solutions tend to be more intelligent dimming, considering the factors of energy saving, the biggest breakthrough in the field of lighting is to improve the application mode of lighting, namely intelligent, wireless lighting control, or "smart lighting". Smart lighting marks a fundamental change in our relationship with light-whether at home, office, or even outdoors. Using a safe, 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 realize the connection between IPs, so that an advanced lighting system that can be easily controlled by, for example, smartphones, tablets, and personal computers can be established.

The intelligent lighting network includes lights, switches, sensors, remote control, and optional IP control methods implemented through the network management of smart phones, tablets, and personal computers. These lights can realize network IP control through JenNet-IP stack protocol based on 6LoWPAN.

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

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