Intelligent control design of LED street light

To use LEDs in street and area lighting applications to replace HID and produce the same light output requires the use of large arrays of LEDs. To drive these large arrays of LEDs, designers can choose different solutions. In addition, the brightness of different LED strings needs to be consistent. If an LED has an open circuit failure, it may cause the entire string of LEDs to turn off. Therefore, it is necessary to take into account the solution to provide protection for the LED string. High-intensity gas discharge lamps (HID) such as high-pressure sodium lamps (HPS) have the characteristics of high light intensity and long life, and are widely used in area lighting applications such as street lighting, parking lots and parks in public places. On the other hand, high-brightness white light-emitting diodes (LEDs) continue to improve in terms of performance and cost, which are very suitable for regional lighting applications, and provide some advantages that HID does not have, such as better directionality, better color quality, and environmental protection. And its turn-on and turn-off can be controlled more conveniently, and it is easy to automatically detect the ambient light to change the brightness; in addition, the reliability of the LED is also better, which will help reduce maintenance costs and total cost of ownership.

To construct a networked intelligent LED street light control system, it is also necessary to adopt a suitable communication and line drive scheme. The following will discuss these issues and the corresponding ON Semiconductor solutions.


The power for area lighting applications is generally higher than 40W. According to different application conditions or requirements, different power supply schemes can be used to drive the LED array. As the premier supplier of high-performance and energy-efficient silicon solutions for green electronic products, ON Semiconductor provides different power solutions for LED street lights and area lighting to meet the different needs of customers.

1) Current adjustable constant current power factor correction area lighting LED power supply based on NCL30001 Some area lighting applications require an isolated regulated output voltage with input power factor correction. These applications usually use a two-stage power conversion architecture, where the boost power factor correction (PFC) converts and pre-regulates the AC input line voltage to a DC 400V voltage, and then provides the voltage to a conventional DC that can be of any suitable topology. -Direct current (DC-DC) converter (usually a flyback converter in applications where the power does not exceed 150W).

We can use a simpler method to improve this traditional two-stage conversion architecture, making it a single-stage architecture that integrates power factor correction and the main converter (ie, DC-DC converter). This single-stage architecture provides significant application advantages because there is no need to use large-size boost inductors, high-voltage MOSFETs, power rectifiers and large capacitors. Of course, this single-stage architecture will bring some performance trade-offs in some aspects, but it is a highly energy-efficient and cost-effective solution, suitable for applications with relatively constant load, such as LED area lighting.

NCL30001 is a single-stage controller that integrates power factor correction and isolated step-down DC-DC conversion circuits to help reduce the number of components, reduce system costs, and support higher overall LED power efficiency. NCL30001 provides steady current and constant current to directly drive LEDs, eliminating the need for linear or DC-DC conversion integrated in the LED light bar. ON Semiconductor’s design note AND8427 describes an LED power supply based on NCL30001 single-segment continuous current mode (CCM) PFC controller and NCS1002 secondary side constant voltage constant current (CVCC) controller, suitable for street lighting and other area lighting applications.

The NCL30001-based LED drive power solution is suitable for 40 to 125W area lighting applications. Tests show that under 90 to 264Vac input voltage conditions, the NCL30001-based LED power supply provides high energy efficiency higher than 85%, the power factor is also higher than 0.9, and provides a short circuit And overvoltage protection. The designer slightly adjusts the resistance in the secondary-side control circuit to adjust the steady current and voltage to support the specific application requirements of the end product. It is also worth mentioning that although this power supply is designed to provide a tightly regulated fixed current, it can also work in constant voltage mode because its current and voltage are based on the tightly regulated 2.5V reference voltage integrated in NCS1002 To stabilize the current and stabilize the voltage.

2) Ultra-high-efficiency and high-power LED street lamp power supply solutions based on NCP1607 and NCP1397 In recent years, the industry has become increasingly interested in ultra-high-efficiency LED lighting topologies. It is expected to provide more than 90% when the power level is relatively low ('50W). % Energy efficiency, this energy efficiency target is even higher than the energy efficiency requirements of the 'Energy Star' version 2.0 external power supply (the energy efficiency is higher than 87% when the power does not exceed 49W). To achieve such high energy efficiency, new topologies are required, such as switching from a flyback topology to a resonant half-bridge topology, so as to give full play to the advantages of zero voltage switching (ZVS). Advantageously, ON Semiconductor has already begun to develop high-efficiency half-bridge solutions that can be used in LED drive power supplies, such as NCP1396 and its upgraded version NCP1397 high-performance resonant mode controller. NCP1397 has built-in high-end and low-end drivers, supports adjustable and precise minimum frequency, provides extremely high energy efficiency, and has a variety of fault protection features. The LED power solution based on NCP1607PFC controller and NCP1397 dual inductor plus single capacitor (LLC) half-bridge resonant controller is very suitable for high-efficiency LED street lighting applications with power in the range of 50 to 300W.

Street lighting high-efficiency LED power solutions based on NCP1607 and NCP1397 In addition to these solutions, designers can also choose other ON Semiconductor LED power solutions based on design requirements, such as NCP1607PFC controller + NCP1377 quasi-resonant controller, or NCP1607+NCP1392/3 Wait.

Protection scheme to enhance the reliability of LED strings

As mentioned earlier, multiple strings of LEDs are usually used in area lighting applications. Although the reliability of the LED itself is very high, if an LED in the LED string has an open circuit failure, the entire string of LEDs may be turned off. This situation must be avoided in applications such as street lighting, thereby reducing subsequent maintenance costs. In view of this, ON Semiconductor has introduced the NUD4700 LED current bypass protector (. This device is a shunt device, in case an LED in the LED string is open, it will provide a current bypass to ensure that a certain LED failure condition The entire string of LEDs will not be turned off; and if heat dissipation is properly handled, large currents greater than 1A can also be supported.


Build a networked LED street light intelligent control system

For LED street lighting, two-way communication can be applied between the centralized control center and street lights to build a fully networked smart street lighting system. In this way, government agencies, power companies, or commercial groups can remotely adjust the light output of LED street lights, thereby reducing the total energy consumption of the street lighting network and reducing costs. In addition, an ambient light sensor can also be integrated into the system to automatically adjust the light output of the LED according to the brightness of the ambient light, thereby helping to save energy.

Advantageously, designers use ON Semiconductor’s AMIS-49587 power line carrier (PLC) modem, PLC line driver NCS5650 and ambient light sensors such as NOA1302 to easily build a networked LED street light intelligent control system based on power lines. Among them, ON Semiconductor's ambient light sensor includes output types, such as NOA1302 and NOA1305 that provide digital output, while NOA1211 is analog output. The working current of these light sensors is extremely low, only 58μA, 550μA and 115μA under the condition of 100 lumens light output respectively, so the impact on system energy efficiency is minimal.

Networked LED street light intelligent control system based on AMIS-49587 and other devices. ON Semiconductor, as the premier supplier of high-performance and energy-efficient silicon solutions for green electronic products, provides complete solutions for LED area lighting applications, such as based on NCL30001 The current adjustable constant current power factor correction solution and the ultra-high-efficiency high-power solution based on NCP1607 and NCP1397, the LED string protection solution based on NUD4700, the networked LED street light control solution based on AMIS-49587, NCS5650 and NOA1302 , And related MOSFETs, rectifiers, filters and thermal protection products, etc., to provide users with a wealth of choices to help them shorten the design cycle and speed up the product launch process.