What are the design standards of LED street lamps - Yangzhou Chuang Chuang photoelectric Group Co., Ltd.

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What are the design standards of LED street lamps?

2020/5/27 17:34:57 Click:

The difference between LED street lamp and regular street lamp is that the LED light source adopts low voltage direct current power supply and high efficiency white light made from GaN based power blue LED and yellow. It has the unique advantages of high efficiency, safety, energy saving, environmental protection, long life, fast response speed and high color rendering index. It can be widely applied to roads. High temperature resistance up to 135 degrees, low temperature up to -45 degrees. LED street lamp The design has the following requirements:


1, the biggest feature of LED for lighting is the function of directional light emission, because power LED almost contains reflectors, and the efficiency of such reflectors is obviously higher than that of lamps.


In addition, the efficiency of self reflector has been included in the detection of optical efficiency of LED.


LED's road lighting should make use of the directional emission characteristics of LED as much as possible, so that each LED in the road luminaire will directly light the light to each area of the road surface, and then use the auxiliary light distribution of the lamp reflector to achieve a reasonable comprehensive lighting of the road lighting.


It should be said that road lighting should meet the requirements of illumination and illuminance uniformity according to CJJ45-2006 and CIE31 and CIE115 standards. The function of luminaire should include three times of light distribution. The LED with a reflector and a reasonable beam output angle has a good light distribution function in itself.


In the luminaire, we can design the LED installation position and the direction of the emitted light according to the height of the road lamp and the width of the road surface, so that we can achieve a good two light distribution function. The reflectors in such lamps and lanterns only serve as auxiliary three light distribution means to ensure better evenness of road illumination.


In the design of the actual road lighting, it is possible to fix every LED with a spherical universal joint on the lamp under the premise of basically setting the firing direction of each LED. When the lamp is used at different heights and illuminating widths, the direction of each LED will be satisfied by adjusting the spherical joint.


When determining the power and beam output angle of each LED, according to the E (LX) =I (CD) /D (m) 2 (intensity inverse ratio law of illumination distance), we calculate the power that each LED should have when the output angle of the selected beam is basically calculated, and we can adjust the output power of each LED and the output power of LED drive circuit to each LED's different power to make the output of each laser light. Achieve the expected value.


These adjustment methods are unique to the road lighting with LED light source. Taking full advantage of these characteristics, we can reduce the lighting power density and achieve the goal of energy saving on the premise of satisfying the illumination and uniformity of the road surface.


2, the power system of LED street lamp is also different from the traditional light source. The constant current driving power required by LED is a cornerstone of ensuring its normal operation. The simple switching power supply scheme often brings damage to LED devices.


How to make a group of LED tightly compacted together is also an index for inspecting LED street lamps. The requirement of LED to drive circuit is to guarantee the characteristic of constant current output, because LED is very small in the relative change area of junction voltage when working, so it ensures the constant LED drive current and basically guarantees the constant output power of LED.


For the unstable situation of power supply voltage in China, it is necessary to drive the circuit LED with constant current output characteristics, which ensures constant output and prevents LED from operating at super power.


To make the LED drive circuit present a constant current characteristic, the output impedance must be high from the output side of the drive circuit.


At work, the load current also passes through this output internal impedance. If the drive circuit is composed of a DC voltage source, a DC constant current source circuit or a general switching power supply plus resistance circuit, it must consume a large amount of active power, so the efficiency of the two types of driving circuits is not high enough to satisfy the constant current output.


The correct design plan is to use active electronic switch circuit or high frequency current to drive LED. The above two schemes can make the driving circuit still have a high conversion efficiency under the premise of maintaining good constant current output characteristics.


China's road lighting basically adopts HID light source plus flip flop and inductance ballast mode. Although this mode has low energy efficiency and strobe problems. The use of electronic driving circuit LED lamps, when used in field lighting occasions, is one of the most important threats to its plasticity.


As we all know, the lightning in the sky is a broad spectrum of radio waves, and overhead road lighting supply lines are well received by wireless.


The radio waves emitted by the same lightning from two power lines are common mode interference signals for the driving circuit. The common mode interference can reach several hundred volts to thousands of volts, and it is easy to break the EMC ground capacitance in the driving circuit or the small air gap between the ground and the outer shell, causing damage to the driving circuit.


In addition, because the power supply line of our country is a polar power source with three phase four wire neutral line grounded, so in each segment of two overhead power lines, the instantaneous voltage difference between two power lines can cause a differential mode interference voltage between the two power lines, and the instantaneous differential mode interference voltage can also reach hundreds of volts to more than 3000 volts. This voltage often breaks the electrical gap between the power rectifier diode and the different polarity electrodes on the printed circuit board, and the LED controller also damages the drive circuit.


To solve this problem, it must be in the input port of LED drive circuit and fast response varistor to ensure the release of differential mode interference. Because the inductive interference of lightning is repeated many times, when the interference voltage is high, the current of the varistors can be discharged instantly, so the varistors should not only have fast response capability, but also have instantaneous conduction capacity of tens of amperes without damage.


In addition to adopting varistors, the input terminals of the driving circuit of LED should also be combined with the protection of conduction interference (EMI) to design compound LC networks, so that these LC networks can not only obstruct the leakage of internal EMI to the power network, but also suppress the interference signals of lightning obviously.


In addition, the electrical clearance of the LED drive circuit should be kept above 7mm. The grounding capacitance of EMI and the ground insulation strength of the drive circuit should meet the requirements of enhanced insulation (4V+2750V), so that the driving circuit of LED can have good resistance to differential mode and common mode lightning induction.

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