Since the Ministry of Science and Technology launched the Ten Cities and Ten Thousand Proposals, local governments have responded with full efforts to promote LED street lights. The vast majority of these are the transformation of existing high-pressure sodium lamps into LED street lamps, so the original AC power supply circuit is still in need, and a number of LED street lamps powered by commercial power are urgently needed. Although the main street power supply LED street lights also use constant current power supply, most of them do not have dimming function. However, even if the mains power supply is used, how to further save energy is still an important issue. To this end, Shanghai Longmao Co., Ltd. and Hong Kong Trent Co., Ltd. have cooperated closely to launch a series of power supply solutions for dimming LED street lamps. Among them are 80W (100W), 112W (150W), 168W (200W), various solutions (the numbers in parentheses represent the wattage of the constant voltage source used). All of these solutions use a first constant voltage and then constant current scheme to achieve the highest performance.
Take the 112W LED street light as an example. Its block diagram is as follows.
Among them, the AC/DC constant voltage source adopts the constant voltage source of VP28SA150U from Hong Kong. Its maximum output power is 150W, the output voltage is 28V DC, and the maximum output current is 5.36A. Its efficiency is as high as 92%, and the power factor is as high as 0.99 or more. The outline drawing is shown in the photo.
The output voltage can be increased by 2-3V according to the maximum voltage required by the LED load, so that the subsequent constant current driving source operates in the buck mode to obtain the highest efficiency.
Connected to Long Mao's dimmable buck constant current source SLM2842JD, this constant current source can accept pulse width modulation (PWM) dimming signal. Its efficiency is as high as 97% or more. Used here to drive 4x7 1W LEDs. A total of four such modules are shared to drive a total of 112W of LEDs. The dimming controller uses the SLM4801 produced by Longmao. The dimming controller can set the brightness of the area according to the traffic flow measured in the area in advance. This controller can start timing and dimming when the entire street light is turned on. It can also be metered according to the light sensor that comes with it, and it will turn on automatically when it is dark. After the program is dimmed, it can save more than 60%.
These kinds of programs have been adopted by relevant enterprises and are ready to be used in several street lights.
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