LED street lighting design standards and lighting requirements

LED street lamp is different from conventional, LED light source adopts low voltage DC power supply, by the high white GaN based blue LED and yellow synthesis, has the advantages of high efficiency, safety, energy saving, environmental protection, long life, fast response, high color rendering index unique advantages, can be widely used in the road. The outer cover can be made up to 135 degrees, and the temperature can reach -45 degrees. LED street lighting design has the following requirements:

1, the most important feature of the LED is the use of directional light emission function, because almost all of the power LED is equipped with reflectors, and the efficiency of such reflectors are significantly higher than the reflector efficiency of the lamp. In addition, the efficiency of the LED has been included in the efficiency of the reflector. The road lamp LED should as far as possible the use of the characteristics of LED directional emission of light, so that all LED road lamps in various regions were directly to the light illuminated the road, then use the auxiliary light reflector lamps, road lamps to achieve a reasonable comprehensive light distribution. It should be said that the road lighting to really meet the requirements of CJJ45-2006 and CIE31 and CIE115 standard illumination and illumination uniformity requirements, lamps should include three times the function of light distribution in order to achieve better. The reflector with a reasonable beam output angle of the LED itself has a good function of light distribution. In the lamp, according to the height of the road lamp and the width of the road to design the installation position of each LED and the direction of the light emission can achieve a good two light distribution function. In this kind of lamps and lanterns of the reflector, only as a subsidiary of the three light distribution means, to ensure better uniformity of road lighting.

In road lighting design practice, can be used in the basic premise of setting every LED design direction, each LED with ball joint is fixed on a lamp, when the lamp is used in different height and width can be adjusted by irradiation, ball joint so that the irradiation direction of each LED can achieve satisfactory results. In determining the power, each LED output beam angle, according to the E (LX) =I (CD) /D (m) 2 (light intensity and illuminance inverse square law), calculate the power of each LED should have the basic beam angle of the selected output power, and can adjust the power to the LED and LED output driver circuit for every LED every LED light output has reached the expected value. These adjustment means are typical road lamps using LED light source, in order to reduce the lighting power density in order to meet the demand of road illumination and the illumination uniformity of the full use of these features will be able to achieve the purpose of energy saving.

The power supply system, 2 LED street is different from the traditional source, LED constant current drive power needs, is to ensure the normal operation of a large base, simple switching power supply scheme will bring LED devices. How to make a compact compact LED security, is also an indicator of LED street lamps. LED requirements for the driving circuit can guarantee the characteristics of constant current output voltage, because the relative changes in a very small area of LED positive work, so to ensure the constant driving current of the LED is the basic guarantee for the constant output power of LED. For the current situation of power supply voltage instability in our country, it is necessary to have a constant current output characteristic of the driving circuit of the road lamp LED, which can ensure the constant output of the light and prevent the LED from running at a super power.

In order to make the LED drive circuit present a constant current characteristic, the internal impedance of the driving circuit must be high. When the load current is also through the output impedance, if the switching power supply and resistor circuit driver circuit by the buck rectifier filter with DC constant current source circuit or general composition, in which must have active power consumption greatly, so the two driving circuit to meet the basic premise of constant current output next, efficiency is not high. The correct design is the use of active electronic switch circuit or using high frequency current to drive the LED, using the above two schemes can make the driving circuit in good constant current output characteristics of the premise, still has very high conversion efficiency

China's road lamps, the basic use of HID light source plus the trigger and the inductance of the ballast mode, although there is a pattern of low energy efficiency and stroboscopic problem. When the LED lamp is driven by electronic driving circuit, it is one of the most important aspects that threaten its plasticity when it is used in the field of lighting.

As we all know, the lightning emitted in the sky is a broad spectrum of radio waves, while the overhead road lighting power lines, is a good acceptance of wireless. A radio wave with a lightning two power line received from the driving circuit is belongs to the common mode interference signal, the common mode interference to reach hundreds of thousands of volts volts, easily breakdown drive circuit EMC grounding capacitance or smaller to (for housing) clearance, the damage caused by the driving circuit.

In addition because of the power supply line in China is the polarity of the power supply system of neutral grounding line four phase, so the two overhead power line segments, in the induction lightning radio waves of the moment, because the two power line on the instantaneous impedance to produce a differential mode interference voltage between the two power lines the instantaneous, differential mode interference voltage can reach hundreds of volts to more than 3 thousand volts. This voltage is often the clearance of different polarity electrode driving circuit breakdown power rectifier diode and the printed circuit board of the LED controller will also drive circuit damage.

To solve this problem, it is necessary to input the LED driver circuit, and then respond to the fast response of the varistor, in order to ensure the release of differential mode interference. Due to the inductive interference of lightning was repeated several times, when the interference voltage increases, the varistor instantaneous discharge current conduction may be large, so the varistor should not only have rapid response ability, should also have the instantaneous turn-on discharge capacity of tens of AMPS without damage. In addition to the varistor, the drive circuit input end of the LED should be combined with conduction interference (EMI) shielding design of composite LC network, the LC network can not only hinder the internal leakage of EMI on power grid, and the lightning interference signal on to inhibit the obvious.

Also, the LED drive circuit of each point to ground clearance should be maintained at more than 7mm, EMI protection grounding capacitance and the driving circuit of the insulation strength, should be to strengthen the insulation (4V+2750V) requirements, so that the LED drive circuit has good ability of anti common mode and differential mode of lightning induction.