LED lights and conventional street lamps is different, LED light source with low voltage DC power supply, by the GaN-based power-type blue LED and yellow synthesis of high efficiency white, with high efficiency, safety, energy saving, environmental protection, long life, fast response, high color rendering index Unique advantages can be widely used in roads. High temperature of 135 degrees, low temperature -45 degrees. LED street lamp design has the following requirements:
1, the biggest feature of LED lighting with directional light emission function, because the power LED is almost always equipped with reflectors, and the efficiency of this reflector are significantly higher than the lamp reflector efficiency.
In addition, LED light efficiency detection has been included in the efficiency of its own reflector.
LED road lighting should be used as far as possible the use of LED directional light emission characteristics, so that the road lamps in the LED were directly directed to the light through the various areas of the road, and then use the lamp reflector auxiliary light, to achieve Very reasonable road lighting integrated light distribution.
It should be said that the road lamps to be truly in line with CJJ45-2006 and CIE31 and CIE115 standard illumination and illumination uniformity requirements, the lamp should contain three times the function of light distribution can be better achieved. And with a reflector and has a reasonable beam output angle of the LED itself has a good light distribution function.
In the lamp, according to the height of the road lighting and the width of the road design of the LED installation location and the direction of the launch light can achieve a good secondary light distribution function. Reflectors in such lamps, only as auxiliary three light distribution means, to ensure greater uniformity of road illumination.
In the actual design of the road lighting, you can use the basic set in the direction of each LED set under the premise of each LED with a spherical universal joint fixed on the lamp, when the lamps used in different height and irradiation width , Can be adjusted by the spherical universal joint so that the direction of each LED to achieve satisfactory results.
In determining the power of each LED, the beam output angle, according to E (lx) = I (cd) / D (m) 2 (light intensity and illumination distance square inverse law), respectively, the LED in the basic selection The beam output angle should have the power, and can be adjusted by the LED power and LED driver circuit output to each LED different power to make each LED light output to achieve the expected value. These adjustment methods are the use of LED light source of the road lamps unique, and make full use of these features can be achieved in the road to meet the road illumination and illumination uniformity under the premise of reducing the lighting power density, to achieve the purpose of energy conservation.
2, LED lights power system is also different from the traditional light source, LED special constant current drive power is to ensure its normal work of a cornerstone, a simple switching power supply program often bring LED device damage.
How to make a tightly packed together a group of LED security, but also an indicator of LED lights. LED on the drive circuit requirements is to ensure that the characteristics of constant current output, because the LED forward work when the junction voltage relative to the region is very small, so to ensure that the LED drive current is also a constant guarantee of LED output power is constant.
For China's power supply voltage supply instability of the status quo, road lighting LED drive circuit with constant current output characteristics is necessary to ensure that the light output is constant and to prevent the LED super power operation
To make the LED drive circuit exhibits constant current characteristics, from the output of the drive circuit inward view, the output impedance must be high.
Work, the load current is also through the output impedance, if the drive circuit by the buck, rectifier filter after adding DC constant current source circuit or a common switching power supply and resistance circuit, on which must also consume a lot of active Power, so these two types of drive circuit in the basic to meet the premise of constant current output, the efficiency is not high.
The correct design is the use of active electronic switching circuit or the use of high-frequency current to drive the LED, the use of these two programs can make the drive circuit to maintain a good constant current output characteristics of the premise, still has a high conversion efficiency.
China's road lighting, the basic use of HID light source with flip-flop and inductance ballast model, this model although there is lower energy efficiency and strobe problem. The use of electronic drive circuit LED lamps, lighting applications in the field, the threat to its plasticity is an important aspect of lightning induction problem. The same time as
As we all know, the air lightning is a broad spectrum of radio waves, while the overhead road lighting power lines are well received by wireless.
Two power lines to receive the same lightning generated by the radio waves, the drive circuit is part of the common mode interference signal, the common mode interference to ground up to several kilovolts to several thousand volts, it is easy to breakdown within the drive circuit EMC ground capacitance or smaller ground (for the shell) of the electrical clearance, causing damage to the drive circuit. The same time as
In addition, because China's power supply line is a three-phase four-wire neutral grounding power, so in the two overhead power supply lines, in the induction of lightning to the moment of the radio waves, due to the two power lines to the ground The instantaneous impedance of the two supply lines to produce a differential between the interference voltage, the instantaneous differential mode interference voltage can reach hundreds of volts to more than 3000 volts, this voltage will often breakdown the drive circuit power supply rectifier diodes and printed The electrical gap between the different polar electrodes on the circuit board, the LED controller will also damage the drive circuit.
To solve this problem, must be in the LED driver circuit input, and then quickly respond to the varistor to ensure differential mode interference discharge. As the lightning sensor interference is repeated many times, when the interference voltage is high, the varistor instantaneous conduction discharge current may be large, so the use of varistors should not only have a fast response capability, but also should have instantaneous guidance Pass the capacity of 10 amps without damage.
In addition to the use of varistor, the LED driver circuit input should also be combined with conduction interference (EMI) protection, designed a composite LC network, so that these LC network can not only hinder the internal EMI on the power grid leakage, Lightning interference signal plays a significant role in the suppression. The same time as
Also, the LED drive circuit to the ground of the electrical gap should be maintained at 7mm or more, EMI protection of the grounding capacitance and drive circuit to the ground insulation strength, should be to strengthen the insulation (4V +2750V) requirements, so that the LED The drive circuit has a good resistance to differential mode and common mode lightning induction capability.