Henan LED street lights, Zhengzhou sign poles, Zhengzhou solar street lights, octagonal poles
Little-known features of solar street lights
Category: Industry News
Dec 06,2021
1. The characteristics of LED lighting are that it has the function of directional light emission, as power-type LEDs are almost always equipped with reflectors, and the efficiency of these reflectors is significantly higher than that of the fixtures' reflectors. Additionally, the light efficiency testing of LEDs already includes the efficiency of their own reflectors. Road lighting fixtures using LEDs should make the most of the directional light emission characteristics of LEDs, allowing each LED in the road fixture to directly project light onto various areas of the illuminated road surface, and then use the fixture's reflector for auxiliary light distribution to achieve a reasonable overall light distribution for road lighting fixtures. It should be said that LED street lights must meet standards.
1. The characteristics of LED for lighting include the ability to emit directional light, as power-type LEDs are almost always equipped with reflectors, and the efficiency of these reflectors is significantly higher than that of the fixtures' reflectors. Additionally, the light efficiency measurement of LEDs already includes the efficiency of their own reflectors. Road lighting fixtures using LEDs should make full use of the directional light emission characteristics of LEDs, allowing each LED in the road fixture to directly illuminate different areas of the road surface, and then utilize the auxiliary light distribution from the fixture's reflector to achieve a reasonable overall light distribution for road lighting fixtures. It should be noted that LED road lighting fixtures must meet standard requirements for illuminance and uniformity, and the fixtures should include a three-stage light distribution function to achieve this effectively. LEDs with reflectors and reasonable beam output angles inherently possess good primary light distribution capabilities. Within the fixture, by designing the installation positions and light emission directions of each LED according to the height of the streetlight and the width of the road surface, good secondary light distribution can be achieved. In such fixtures, reflectors serve only as auxiliary means for tertiary light distribution to ensure better uniformity of road illuminance.
In the design of actual road lighting fixtures, it is possible to fix each LED with a spherical universal joint under the premise of setting each LED's emission direction. When the fixture is used at different heights and illumination widths, adjusting the spherical universal joint can achieve satisfactory results for each LED's emission direction. When determining each LED's power and beam output angle, calculations can be made based on E (lx) = I (cd) / D (m)² (the inverse square law of luminous intensity and illuminance), to determine the required power for each LED at a basic selected beam output angle. Furthermore, by adjusting each LED's power and providing different power outputs from the LED driver circuit to each LED, it is possible to ensure that each LED's light output meets expected values. These adjustment methods are unique to road lighting fixtures using LED light sources; fully utilizing these characteristics can reduce lighting power density while meeting road surface illuminance and uniformity requirements, achieving energy-saving goals.
2. The power supply system for LED streetlights is also different from traditional light sources. The constant current driver power supply required by LEDs is a cornerstone for ensuring their normal operation; simple switch-mode power supply solutions often lead to damage to LED devices. Ensuring safety for a tightly packed group of LEDs is also an indicator for evaluating LED streetlights. The requirement for driver circuits in LEDs is to guarantee constant current output characteristics because when LEDs operate in forward mode, their junction voltage varies very little; thus, maintaining a constant current through the LED driver essentially ensures a constant output power from the LEDs. Given the unstable state of power supply voltage in our country, it is essential for LED driver circuits in streetlights to have constant current output characteristics to ensure stable light output and prevent over-power operation of LEDs.
To achieve constant current characteristics in an LED driver circuit, looking inward from the output end of the driver circuit, the output internal impedance of an LED streetlight must be high. During operation, load current also passes through this output internal impedance. If the driver circuit consists of a step-down rectification filter followed by a DC constant current source circuit or a general switch-mode power supply with resistive circuits, it will inevitably consume significant active power; therefore, these two types of driver circuits cannot achieve high efficiency while fundamentally meeting constant current output requirements. The correct design solution is to use active electronic switching circuits or high-frequency currents to drive LEDs; employing these two solutions can maintain good constant current output characteristics while still achieving high conversion efficiency.
In our country, most road lighting fixtures use HID light sources combined with trigger devices and inductive ballasts. Although this mode has issues with low energy efficiency and flickering problems, using electronic driver circuits in LED fixtures poses an important threat to their plasticity when used in outdoor lighting situations due to lightning induction issues.
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