Digital control flexibility allows OEMs to design a controller to drive various end products, enhance design flexibility, and bring new intelligence and differentiation to lighting installations.
As the lighting industry turns to LED technology, it also increases the demand for smarter controllers and drivers. The high-efficiency operation of LED can effectively suppress the rising electricity expenses of households and units. Many applications need to provide constant lighting quality while supporting advanced control functions such as dimming, color temperature equalization, and accurate color mixing. Application self-diagnosis can reduce the need for technicians, thereby reducing maintenance costs. Remote connection has also become a routine requirement for these applications.
Adding intelligence to LED lighting applications may require a shift from fixed-function LED drivers to microcontroller-based or programmable architectures. The dedicated power electronic microcontroller can also control the lighting power supply in addition to lighting control and communication, thereby making lighting applications more efficient and cost-effective. The conversion to digital control enhances flexibility and enables lighting products to reach new levels of intelligence and differentiation.
Get an intelligent platform
The lighting industry is quickly taking advantage of many advantages of LED technology (see sidebar "Advantages of LEDs"). However, LED applications have very different capabilities for the support they need.
Home applications include bulb replacement, accent lighting, and small outdoor lighting. Normally, only a few LEDs need to be lit, usually one string to two strings. In view of the low-cost pressure in this market, advanced control functions are not commonly used.
Business applications include fluorescent ballasts, bulb replacement, and accent lighting. Only a few LEDs need to be lit, generally one string to two strings. Although focusing on cost, this market also focuses on energy saving. Higher-end applications require remote connectivity and some controller intelligence.
Entertainment applications include high-end displays and situational lighting. Full control of light intensity and consistent color quality are basic requirements, as well as remote connectivity and support for industry standard protocols such as DALI (Digital Addressable Lighting Interface) and DMX512.
Outdoor and infrastructure applications include street lighting and the lighting of factories and large office buildings. Usually a large number of LEDs are required and many light strings must be supported; high-brightness LEDs are also commonly used. These applications require remote connectivity and a high level of controller intelligence.
The simplest LED-based lighting system uses an LED driver, usually a fixed-function device, which provides a simple, direct, and low-cost control method. In general, they have good power efficiency and do not require software programming. Developers at most do some calculations when choosing a driver or deciding the specific values ​​of components on a circuit board.
Although simple and clear to use, many LED drivers lack the full flexibility of more advanced systems. To support multiple LED types or LED string structures in a given application, different solutions may be required. In fact, any modification in the system may require changes to the driver, such as a change in the number of LEDs in a string, or a change in the number of LED strings in a device. Therefore, most lighting products provided by an OEM may require a dedicated analog driver. If the number of products is large, this requirement will increase the variety of OEM or supplier inventory varieties, may reduce economies of scale, or lead to higher equipment costs.
On the other hand, smart controllers enable developers to create more flexible lighting systems. In a system using a microcontroller, configuration codes can be used to support various types of LEDs, proprietary power stage requirements, different string lengths, and different string numbers without major hardware changes. The system can be designed to automatically detect the number of LEDs that need to be driven. The programmable features of the microcontroller system can even achieve advanced dimming and timing functions for more advanced lighting scene control and automatic illumination levels.
The flexibility of digital control allows OEMs to drive a variety of end products as long as they design a controller. Reusing control IP can also greatly reduce design investment. A flexible controller can reduce the number of components that need to be stocked, and reduce the overall system cost through economies of scale.
Integration with digital control
The basic architecture of an intelligent LED lighting system includes three main parts: power conversion, LED control and communication (Figure 1).
The power conversion stage provides the correct voltage and current for the LED. It starts with AC / DC rectification, then a PFC (power factor correction) stage, followed by one or more parallel DC / DC conversion stages. Energy-efficient power conversion requires precise and flexible control of these stages.
Each part of the main stage requires an intelligent controller to maintain its efficiency and function. Fixed-function analog solutions may require independent PFC, DC / DC, LED, and communication controllers. The dedicated power electronic microcontroller can achieve a high degree of integration, reducing the number of power supply components. In fact, a single microcontroller has enough performance, power-optimized peripherals and communication ports to provide a centralized programmable platform to coordinately control all three levels of an intelligent lighting system and handle power, LED The task of lighting control and communication.
Digital power control also makes it possible for dynamic systems to achieve higher conversion efficiency. Although the efficiency of LEDs has been significantly improved compared to traditional light sources, which has correspondingly reduced the cost of usage and electricity costs, not all LED systems are the same. Digital power control can make the power stage achieve higher efficiency when dimming, changing the color output, or adjusting the light output of the LED lighting system. Similarly, under fixed lighting conditions, the microcontroller can increase operating efficiency through more advanced power stage design. This increase in efficiency is very attractive to end users and can be a key difference when the two LED systems compete with each other.
Suppose a city intends to replace 2,000 street lights, and the two models are being evaluated with a 10% difference in efficiency (Figure 2). For high-efficiency systems, the input power into the system is 178W, while low-efficiency systems require 200W to obtain the same 160W optical output. This alone is the power of the power supply, which is converted into annual energy costs, which can save about 10%, in this case, $ 33,726. Savings balance exceeds savings using LED system.
Benefits of intelligence
For many applications (including commercial displays and entertainment lighting), the quality of the light is very important. At this time, quality refers to the ability to output stable light intensity and color. There are three main factors that affect LED performance: manufacturing differences, temperature, and aging.
The output of different batches of LEDs may vary greatly; devices using the same product line but different batches of LEDs may have different luminous qualities because of manufacturing differences. Using the same batch of LEDs on a single device can maintain the consistency of quality. If this is not possible, the luminous quality of the devices made of different batches of LEDs can be noticeable when installed adjacent to each other Accept) the difference. With an intelligent controller, the system can calibrate and compensate for any differences. Since this work is done by software, if product consistency is required, the calibration process can be completed during device manufacturing.
As the ambient temperature changes, the LED output will also change. To compensate for this effect, the system needs a sensor to detect the temperature of the environment. The microcontroller reads the sensor data, adjusts the LED driver accordingly, and dynamically calibrates the color and light intensity. Since the temperature only needs to be checked regularly, the workload of this work is not high. This also allows the system to monitor its own security status. For example, when the LED temperature exceeds a specified threshold, the lighting controller can reduce the light intensity, or turn off a certain LED string, and notify the staff remotely. Extreme temperatures can cause premature aging of LEDs and degrade their light output. Ensuring that the LED does not exceed a certain temperature can extend its service life.
The aging of LED will affect the luminous quality and cause the color change. For example, red LEDs age faster than blue LEDs, and a certain color produced by a certain power output or PWM frequency will drift over time. The intelligent controller can take into account the aging situation and correct the color curve to maintain a consistent light emission throughout the life cycle of the LED system.
The same technology used for quality control can also improve safety and efficiency. The luminous intensity can be adjusted to match the current ambient light. For example, in stormy weather, street lights may be turned on in advance, or when there is sufficient ambient light, it can be turned down. Brightness to save energy consumption. Sensors on traffic lights or special street lights can monitor the traffic conditions late at night. If more traffic flows, the brightness of street lighting can be increased.
In the warehouse, workers may use different spaces scatteredly. The indoor sensor can illuminate only the part that is being used. If at any time, only 50% of the workshop area is used, the remaining lights can be turned off, saving half of the energy consumption.
Also consider the street lamp example in Figure 2. In the middle of the night, many street lights can be dimmed than when they are full, because the traffic flow drops. If there is a communication network between the motion sensors, the street lights can be switched on and off dynamically to meet the needs of traffic flow. To achieve higher efficiency, the 178W input system shown in Figure 2 can turn off 25% of the lights, correspondingly saving 25% of energy consumption, which is equivalent to 68,218 US dollars per year, calculated by the following formula: 1,819,160kWhr / Year & TImes; 75% / night working hours = 1,364,370kWhr / year1,364,370kWh r / year & TImes; $ 0.15 / kWhr = 204,656 dollars annual cost 272,874 dollars initial cost minus 204 The annual cost after correction of $ 656 = $ 68,218 per year. Adding the savings in power efficiency to the savings in smart work can save $ 101,944 per year, which is about 33% of the system.
Remote Connection
Remote connection is a key feature of smart lighting systems. Smart devices can automatically manage their own operations, improving efficiency and quality. But unless the device can communicate with the central controller, this kind of intelligence must be pre-programmed, and only a single device can get the highest efficiency.
By connecting the various components in the lighting system, developers can coordinate the operation of each device in the overall installation. This can achieve a brand new function, including remote dimming, remote shutdown and emergency control. The operator can adjust the illumination intensity of the entire light group from a central control position without adjusting each lamp individually.
To get the most functionality, each component must be able to both receive information and send it back to the operator. In this way, the street light can do a simple self-diagnosis to determine whether the LED is burnt out or the performance is below a minimum quality threshold, and then inform the operator to do the necessary maintenance. In this way, there is no need for technicians to do regular maintenance to ensure that the equipment is working properly. Operators can make remote inspections, and only send technicians when the problem is serious to a certain extent. The combination of this remote monitoring and the long working life of the LED can greatly save maintenance costs and increase the safety of operation, because faults can be judged immediately.
Remote control can also realize other advanced functions, which have a significant impact on work efficiency and cost. It can dynamically control lights and connect multiple lighting points to a control point somewhere. This control point may be related to the actual light. The location is far away. For example, street lights may need to be adjusted according to daylight saving time. At this time, there is no need to send a technician to each control box. The lighting system operator can modify the schedule of all lights in the system. The operator can also easily make temporary changes in the schedule, such as providing road lighting after the sports meeting at the end of the evening, or maintaining factory lighting during busy seasons. Remote control can also directly control lights in an emergency situation, thereby improving safety.
Smart lighting in business and industry also has a more beneficial function, which is to accurately track power consumption. For example, in the past, the payment rate of street lights was fixed, and with the intelligent light controller, municipal operators can track the actual power consumption and send the data to a central control point to ensure that the electricity fee paid by the city does not exceed the actual Amount.
Data recording of actual usage allows operators to precisely adjust their operating cost planning, maintenance resources, and future investment. It also enables more advanced prospective diagnosis. Dynamic high energy consumption or the need to replace a large number of bulbs. If these problems can be notified to the operator early, they can be dealt with as soon as possible before they drive up the cost of operation and maintenance.
Connectivity is also the basis of many lighting systems, especially entertainment applications. There are many communication standards in this market, including DALI, DMX512, and KNX, and devices that support these protocols have a competitive advantage.
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