Experts explain the key design elements of smart LED lighting

Mr. Zheng Zhaoxiong, Senior Marketing Director of the Application Products Division of ON Semiconductor, believes that "intelligent LED lighting" that integrates sensing and detection, intelligence, communication and control is expected to grow significantly in 1 to 5 years. ON Semiconductor's expertise and technology in industrial applications provide the company with a unique position to help develop the "intelligent lighting" market.

　　The degree of intelligence in LED lighting systems is an issue that deserves attention. LED lighting can reduce energy consumption and maintenance costs, and intelligent LED lighting design can further improve system performance in two ways: getting better performance per watt and reducing long-term operating costs. Power measurement, ambient light detection and communication are the basis of intelligent LED lighting design: power measurement provides information on the health and energy consumption of the system; ambient light detection can reduce the actual lighting time of the LED, saving energy and extending the life of the diode; and communication functions connect each light source together for maintenance identification and system-level coordination. This article will explore the impact of each circuit on the overall system.

　　introduction

　　Imagine a marathon in hot, smoggy weather, where every ounce of energy saved can make all the difference. Often, the race seems decided before the halfway mark. The frontrunners seem untouchable, as they are able to cover greater distances with less energy. The frontrunners are radiant and radiant, remaining calm and in good shape despite the heat and competition. But can these runners really hold their pace and stay ahead in the second half of the race? Among athletes who have been carefully trained and competed, talent and potential can only go so far. To succeed, you need to expend a great deal of potential on the road. Can today's frontrunners tap into their potential, apply strategies, and cope with the elements to finally achieve their goals? Time and wisdom will tell.

　　Now, you might be asking me, "What does a marathon have to do with LEDs? Do you really know what you're talking about?" I think so. Just like a strong runner leads a marathon, LEDs are leading the way in energy-efficient lighting. The main technological advantages of LEDs over incandescent and fluorescent lighting are that they consume less energy, last longer, and allow for greater control over the color and direction of the light.

　　It is estimated that lighting accounted for 19% of electrical energy in the United States in 2010;1 by 2030, lighting energy consumption will reach 767 terawatt hours (TWh) per year.2 What a great opportunity for us to be the leaders of this special marathon! By 2030, LED lighting can reduce electricity consumption by 25%.2 In addition, because LEDs last five times longer than other lighting solutions and contain no hazardous materials, they can reduce the amount and type of solid waste generated by lighting. It may even be necessary to replace LEDs instead of replacing them when renovating a building. Moreover, the ability to fine-tune color using red, green, and blue (RGB) LEDs also opens up new opportunities for quality and creativity. LEDs will eventually be used for more than just space lighting, and will be more suitable for new styles and installations.

　　LED intelligence - the key to winning the game

　　How will LEDs fulfill their potential? The first hurdle is, of course, price. LEDs currently cost much more than existing lighting solutions. Energy savings are often not enough to convince price-sensitive businesses and consumers to buy more expensive products. Over time, mass production may reduce prices, but whether costs can be reduced enough and at a pace that users expect is uncertain and beyond the scope of this article. If we go to two hardware stores and try to find the same LED light, it may be very difficult. Many retailers will not stock enough variety or quantity just to attract a few consumers. Why? It comes down to price and inventory turnover. So what does this mean for us engineers and innovators? How can we make LED lighting realize its potential? How can we win this marathon? What if we give LEDs a "brain" and make them intelligent? Give these lights eyes, throats, and counting functions. Designing valuable semiconductor materials in the field of lighting will optimize energy efficiency, extend lighting life, and reduce maintenance costs. This will help LEDs run the entire race, persist to the end, and win the race with wisdom.

　　Key elements of LED intelligence

　　Ambient light sensing, communication, and energy measurement are key elements of intelligent lighting systems. Ambient light sensing allows dimming of lights when other light sources are providing adequate lighting, and by sensing the color of ambient light, the color of advanced RGB  LED lighting systems can be adjusted. Communication capabilities allow remote control and connecting small and large lighting installations into a central network. Energy measurement accurately calculates the power consumed, providing system insights for predictive maintenance. All of these features—ambient light sensing, communication, and energy measurement—will further save energy and reduce operating costs. This article explores the key design considerations for adding ambient light sensing, communication (both wireless and power line), and energy measurement capabilities to LED lighting systems. Reference design examples are provided.

　　Ambient light sensors (ALS) detect the amount of light near the sensor. These simple devices become the "eyes" of the LED lighting system and are key to saving energy. When the room is already well lit, lighting is completely unnecessary and can be dimmed or turned off completely to reduce power consumption and extend lamp life. Key features of the ALS include power consumption, lumen detection range, and IR and UV filtering. These sensors must sit quietly in the system and not consume so much power that it defeats the purpose of saving system energy. A good ALS consumes less than 1μA. The lumen detection range must be within the typical lumen range of an outdoor environment. 0.1lx to 100,000lx generally meets most application requirements. For system reliability reasons, it may be necessary to use a slightly larger range. IR and UV filtering eliminates the spectrum of invisible light in a practical system.

　　Light Detection

　　Figure 13 shows an ALS design in a light source. The sensor must be shielded from the light of the lamp itself to avoid affecting the ambient light measurement. In this design, the ALS is located on a separate circuit board, in the shadow of the lamp bracket. This simple design allows the ALS to shut off the lamp when it detects that the ambient light exceeds a preset value. RGB sensors can even add more "functionality" to lighting applications. An LED lighting system with RGB LEDs and ALSs like the one shown in the figure can dynamically adjust its color output to meet special application needs, such as stage scene lighting or display effects in department stores.

Figure 1: The ALS is mounted on a separate PCB and is in the shadow of the light fixture, preventing the sensor from reading the light intensity of the light itself 　　.

　　Next, we discuss the intelligent communication of LEDs . Ears and throats are the next most important functions to realize the intelligence of LED lighting . By simply networking the lights, the lights can be turned on, off, or dimmed through the network, which will reduce energy consumption. Communication also provides fast feedback for power outages, maintenance, and emergencies, and this information will save overall system maintenance costs. Wireless and wired communications can work well in different environments, depending on the size and topology of the network. Wireless is more suitable for small indoor and large outdoor applications, the latter of which requires continuous line of sight, available frequency bands, and sufficient transmission power margin. Power line communication (PLC) uses existing power lines to achieve communication. PLC is very suitable for large municipal lighting installations, tunnels, indoor parking lots, and other environments where natural light cannot be used due to physical location or building walls. In all communication applications, reliability is the key. If the communication fails, the system is of no benefit.

　　In wireless applications, the signal transmission method may be Wi-Fi, ZigBee, or other standard protocols that are often in, but not limited to, the Industrial, Scientific, and Medical (ISM) radio frequencies. Limiting power consumption provides network flexibility, which is critical if the endpoints are using batteries. Figure 2 shows a unique application where a light switch is equipped with an energy harvesting radio frequency (RF) transceiver. The system harvests the energy used to flip the switch and generates a usable DC voltage to support the radio communication (<1GHz RF) of the lighting fixture. The switch can be placed anywhere in the room as long as the signal can reach the light source. Without the need to wire a light switch, interior design is more flexible and lighting control is more reliable.

Figure 2: A building automation application where a light switch features a wire-free, energy-harvesting RF transceiver to control LED lighting.

　　PLC lighting control methods utilize existing power lines and are a cost-effective option. Because communication is achieved through well-maintained existing power lines, PLC avoids many problems, such as shared communication frequencies, performance in bad weather, and network maintenance. Range, speed, and reliability are key to designing PLCs.

　　Power lines are extremely noisy, affecting the reliability of system communication. G3-PLC communication is a new PLC standard based on OFDM that enables reliable communication on power lines. The standard supports speeds up to 300kbps, mesh networking, and a reliable mode in high-noise environments, making it ideal for LED control networks. OFDM-based, PLC-controlled lighting networks are similar to existing G3-PLC.

　　Figure 3 shows a PLC device used for tunnel lighting by Nyx Hemera Technologies.4 The system has saved 25% of electricity and reduced maintenance costs by 30%. The large-scale facility system supports up to 1022 lights and has a communication distance of up to 3 km.

　　Figure 3: Example of a municipal streetlight network using PLC.

　　Smart LED lights also need to be able to calculate power. From smart meters to voltage controllers to electric vehicle chargers, every smart grid device has power measurement capabilities to provide accurate power usage information to power companies and users in real time. Most lighting devices that send back power consumption provide detailed information about the building and municipal lighting environment, which can ensure that power companies' charges are strictly consistent with power consumption. Respond to user needs in a timely and accurate manner by dimming or turning off lights when not in use. In addition, fluctuations in power consumption of specific lights indicate the need for system repair, maintenance or replacement. Of course, many lights are in hard-to-reach areas, and optimizing maintenance can save money. To generate useful data in the smart grid, power measurement designs must maintain high-precision measurements over a wide current range. Not only that, limiting or eliminating calibration time will also reduce overall system costs. Figure 4 shows a flexible LED lighting reference design with power measurement capabilities. 5 The power measurement chip also provides system dimming and DALI interfaces.

　　Many cities currently have non-intelligent LED lighting installed, which provides a huge business opportunity for integrated modules that improve the performance of LED lighting facilities. To achieve upgradeability, these systems need to be connected to intelligent lighting systems. Given the cost and capacity of LEDs, simply replacing relatively new and efficient LEDs is not cost-effective. Simple interfaces, such as DALI, allow ALS, communication and energy measurement functions to be added in the future.

Figure 4: A complete smart LED lighting reference design with energy measurement, ambient light sensing, and communications capabilities.

　　The final winner

　　What does this mean for us? Consumer acceptance and conversion of LED lighting is a long process. It is clear that LED lighting has the potential to change the way lighting is done and save huge amounts of electricity. Adding the key elements of "smart" lighting - ALS, communication and power measurement - will make LEDs more powerful and more attractive. The measurement data provided by intelligent LEDs can further reduce the energy consumption of lighting systems and reduce operating and maintenance costs. Add intelligent design and LEDs will fully realize their potential and beat traditional lighting in an already fierce competition.