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Keywords: ON Semiconductor LED area lighting With the increasing awareness of energy conservation and environmental protection, the industry is increasingly concerned about the impact of energy consumption on the environment. Among various energy consumption pathways, it is estimated that up to 20 to 22 electric energy is used for illumination. Increasing the energy efficiency of lighting applications and even further reducing their energy consumption will help reduce carbon dioxide emissions and create a greener world. Therefore, energy-efficient lighting is becoming a focus of competition in the industry.
From the application field, lighting covers different categories such as residential lighting, industrial lighting, street lighting and restaurant, retail and service lighting. In terms of power level, in addition to low-power lighting, high-power area lighting, typical applications such as column lights, wall washers, exterior wall lights, tunnel lighting, street lights, parking lots and public safety lighting, industrial and retail lighting, etc. Outdoor lighting, as well as indoor lighting such as low ceiling lights, high ceiling lights, freezers/refrigerators and parking garages.
There are many challenges in high-power area lighting, such as the possibility that the luminaire may be difficult to access, the safety problem may occur when the light source fails, and there are many extreme environmental conditions in the outdoor. In addition, it should not be overlooked that existing light sources (such as metal halide lamps, high pressure sodium lamps, linear fluorescent lamps, and compact fluorescent lamps) used in high-power area lighting have many limitations, such as poor color rendering of high-pressure sodium lamps (CRI is about 22), the typical luminaire loss of metal halide lamps is higher (40) and the time from start-up to luminescence to full brightness may be as long as 10 minutes, the cold-temperature performance of linear fluorescent lamps is poor, and the start-up speed of compact fluorescent lamps is slower. .
On the other hand, with the continuous improvement of high-brightness white light-emitting diodes (LEDs) in terms of performance and cost, they are increasingly used for high-power area lighting, and provide advantages that traditional light sources do not have, such as emitting light per lumen. It consumes less power, has better direction control, better color quality, is environmentally friendly, and can be more easily controlled by turning it on and off, allowing automatic detection of ambient light to change brightness; in addition, LED reliability is better, which is beneficial to the LED. Reduce maintenance costs and total cost of ownership.
First, the LED area lighting application requirements LED driver's main function is to flow at a lower limit of various conditions, and to protect the LED from surges and other fault conditions, and provide a certain level of safety, avoid (electrical and / or mechanical Mode) shock and fire. For regional lighting applications, the outdoor environment poses a temperature challenge to the LED driver and may need to withstand a higher input voltage than the standard voltage of 277Vac, 347Vac or even 480Vac.
LED drivers for regional lighting applications may also need to meet certain specifications for power factor or harmonic content. For example, the European Union's International Electrotechnical Union (IEC) IEC61000-3-2 standard requires harmonic content of lighting equipment (class C) with a power exceeding 25W, equivalent to a total harmonic distortion (THD) of less than 35; The IEC61000-3-2C harmonic content requirements do not necessarily indicate that the power factor (PF) is higher than 0.9. In some markets (such as the US), PF is generally required to be higher than 0.9 and THD is lower than 20. Many regional lighting applications are outdoors. It may be subjected to a variety of stringent temperature conditions, which will affect the overall service life. While the overall system design has a significant impact on service life, it is important to use an energy-efficient LED driver with less internal heat generation and lower losses, and to thermally isolate the driver from the LED heat source in the design to enhance system reliability.
Figure 1 Intelligent dual brightness level LED street lighting example LED lighting control can also become more intelligent. Traditional street lights come from the main control with a timer or ambient light sensor. The use of power line communication (PLC) or wireless control technology can provide highly flexible LED area lighting control, such as time-based light output level centralized control, vehicle flow sensor based lighting level control, and control based on detection of people and vehicle activity. Downtown lighting, taking care of walking cars and street lighting. LED intelligent control technology saves energy and does not compromise safety. Typical applications include smart dual-brightness lighting, such as parks, gas station ceilings, parking lots, stairs, and refrigerator cabinet lighting that support lighting levels that adjust brightness levels as needed. LEDs can be turned on and off instantly, allowing for easy adjustment of lighting levels based on motion or activity in these applications, such as providing a brightness level of 20-40 when no activity is detected and 100 brightness when detecting activity . This will save a lot of extra power consumption.
2. LED area lighting power supply architecture and typical LED driving scheme 1) Distributed/modular scheme suitable for applications such as linear lamps and trunking lamps In high-power LED area lighting applications, a common power supply architecture is power factor correction (PFC). Constant voltage (CV) Constant current (CC) three-stage architecture. In this architecture, the AC input power supply is subjected to power factor correction and isolated DC-DC conversion, and outputs a fixed voltage of 24 to 80 Vdc, which is supplied to a constant current LED module with a built-in DC-DC buck converter circuit. (See Figure 2). The design of this architecture provides a modular approach to field upgrades that can flexibly change the number of LED strips as needed to increase or decrease the light output to meet specific area lighting application requirements. In this architecture, AC-DC conversion and LED driver circuits are not integrated, but distributed configuration, which simplifies security considerations and enhances system flexibility. It is also called distributed solution, typical application. Including linear lights and trunking lights.
Figure 2. Typical Modular LED Area Lighting Power Architecture Schematic In this modular approach, one design can be extended for multiple light output levels. Moreover, as the LED light output performance is enhanced, the LED module must provide the same light output level, and the required light bar is better. Each light bar is equipped with a dedicated DC-DC LED driver, such as the CAT4201 high-efficiency buck LED driver from ON Semiconductor. Optimized for driving high current LEDs, the CAT4201 features a patented switching control algorithm that delivers energy efficient and accurate LED current regulation (up to 350mA). The CAT4201 can be powered from a supply voltage of up to 36V and is compatible with 12V and 24V standard lighting systems. Figure 3 shows the CAT4201's high-voltage LED driver configuration. The peripheral N-channel MOSFET supports high-voltage input: LED power is 30W at 100V input voltage; LED power is 13W at 50V input.
Figure 3 CAT4201 high-voltage LED driver configuration 2) Integrated / single-segment solution for applications such as wall washers, exterior wall lights, etc. Not all regional lighting applications require a distributed/modular solution. With the rapid improvement of white LED performance, new LEDs can be used with the new LED driver design method. Leading LED manufacturers have introduced new LEDs that support higher currents and higher luminosity, such as Cree's XP-G series LEDs (with a forward voltage drop of 3.3V) delivering 330 lumens at 1A, SeoulSemiconductor The P7 series LEDs (with a forward voltage drop of 3.3V) provide 400 lumens of light output at 1.4A. Under these conditions, a novel LED driver can be configured to directly drive a large current of 1A to 3A. For example, an NCL30001 power factor corrected TRIAC dimmable LED driver from ON Semiconductor can be used.
The NCL30001 is a monolithic/single-segment LED driver solution that integrates a PFC and isolated DC-DC converter circuit and provides a constant current to directly drive the LED. This solution is equivalent to converting AC-DC with The LED driver two-part circuit is integrated and located in the lighting fixture, saving the linear or DC-DC converter integrated in the LED strip. This monolithic solution has fewer power conversion segments, reduces component usage (such as optical components, LEDs, electronic components, and printed circuit boards), reduces system cost, and supports higher overall energy efficiency of LED power supplies. Of course, this solution has higher power density and may not be suitable for all area lighting applications. Its optical pattern may be more suitable for lower power LEDs. Typical applications include LED street lights, exterior wall lights, wall washers and refrigerator cabinets. Lighting, etc.
Figure 4. 90W LED Driver Demonstration Board Circuit Based on NCL30001 LED Driver and NCS1002 Controller. This 90W constant voltage constant current demonstration board accepts an extended universal input voltage of 90 to 265Vac (305Vac can be supported under replacement components), providing a constant 0.7A to 1.5A. Current output range (selectable by micro-amplitude resistor æ ) and constant output voltage range of 30V to 55V (selectable by resistor divider), maximum output power 90W, support 50 to 1,000Hz dimming control, and include A 6-pin interface to an optional dimming card for analog dimming applications such as current regulation/dual brightness level digital dimming. In addition, the demo board provides a wide range of protection features such as short circuit protection, open circuit protection, over temperature protection, over current protection and over voltage protection. Tests show that the demo board has an energy efficiency of more than 87 at 50W output power, 1,000mA output voltage / 48V forward voltage drop (see Table 1 for details), power factor greater than 0.9 at 50 to 100 load conditions, and compliance with IEC61000 -3-2C equipment harmonic content standard.
Figure 5 Energy Efficiency Test Results for 90W LED Driver Demonstration Board Based on NCL30001 and NCS1002 3) Energy-Efficient LLC Topology Drive Power for Higher Power Area Lighting Applications In recent years, the industry has become more interested in ultra-efficient LED lighting topologies. Provides high energy efficiency (eg, above 90) in more powerful 50W to 250W LED area lighting applications. To provide such high energy efficiency, an energy-efficient power supply topology, such as a resonant half-bridge dual inductor plus single capacitor (LLC) topology, is required to take advantage of zero voltage switching (ZVS).
In this type of ultra-high-power LED area lighting application that requires ultra-high efficiency, it can be combined with ON Semiconductor's NCP1607PFC controller and NCP1397 dual inductor plus single capacitor (LLC) half-bridge resonant controller for powers from 50 to 300W. Range of energy efficient LED street lighting applications. The NCP1397 is the latest high performance resonant mode LLC controller with integrated 600V high voltage floating driver, supports high frequency operation from 50 to 500kHz, built-in high-end and low-end drivers, supports adjustable and accurate minimum frequency, provides extremely high energy efficiency, and A variety of fault protection features.
Figure 6 Street lighting energy-efficient LED power supply scheme based on NCP1607 and NCP1397 III. Protection scheme for enhancing LED string reliability Multi-string LEDs are usually used in regional lighting applications. Although the LED itself is highly reliable, if one of the LED strings is open, the entire string of LEDs may be turned off, and this situation should be avoided in applications such as street lighting, thereby reducing post-maintenance costs. ON Semiconductor has introduced the NUD4700LED current bypass protector. This device is a shunt device. If an LED in the LED string is open, it will provide current bypass to ensure that the entire LED will not turn off under the condition of a certain LED failure; and it can also support proper heat dissipation. Large current greater than 1A.
IV. Summary As a leading high-performance, energy-efficient silicon solution provider for green electronics, ON Semiconductor offers a variety of solutions for LED area lighting applications, such as CAT4201 for distributed/modular power architectures. Buck LED driver, NCL30001 single-stage high power factor LED counterpart for integrated power architecture, NCP1607PFC controller for high-power LED area illumination and NCP1397 resonant half-bridge LLC controller solution to meet different application needs of customers . ON Semiconductor also offers networked LED streetlight control solutions based on AMIS-49587 power line communication (PLC) modems, as well as related MOSFETs, rectifiers, filters and protection products, providing users with a wide range of options to help them shorten design cycles To speed up product launch.