Global humans are working hard to change the impact of the global warming effect, and the call for energy conservation and emission reduction is high. The "LED Street Light", which is now the focus of the energy-saving "long life" project, has become the "darling" of the energy-saving lighting industry. According to a survey by the High-tech LED Industry Research Center, among the 21 pilot cities in the “Ten Cities and Ten Thousand Cities†in 2009, LED street lights (including tunnel lights) have been installed, which is about 222,000 baht. Among them, 35,000 in Weifang, 28,000 in Wuhan, 25,000 in Chongqing, and 15,000 in Yangzhou. The sum of the installed lights in the four cities is 103,000, accounting for nearly half of the total. Most cities are still in the pilot phase of the project in 2009 and are expected to be rolled out in large quantities within two years.
But we must clearly understand that when everyone is promoting the long life of LED, it ignores or avoids another key issue that determines the life of LED lamps: that is the quality of LED driver power.
In this regard, the author has made a brief analysis of the key parts that affect the quality of LED power supply, for your reference!
LED power supply life:
Since LED lamps are different from traditional lamps, except for part of the power converted into light energy, most of the power is converted into infrared radiation energy to the external space of the lamp (just like the Yuba lamp), and the LED is semiconductor light. Except for part of the power converted into light energy, most of the power is converted into heat, which can only be dissipated by the lamp body tightly coupled with the chip.
In order to make the overall structure of the lighting products beautiful, the business often closely designs the power supply and the LED light body structure. The heat of the LED and the heat of the power supply are superimposed, so that the power source and the LED light source are in a bad working environment, when the temperature of the working environment When the temperature exceeds a certain temperature, the life of the power supply and the LED is greatly reduced. When the temperature is set inside the power supply, the phenomenon of repeatedly switching the light will occur. If the temperature protection is not set, the high temperature will damage the power supply device and accelerate the light decay of the LED.
The LED power supply belongs to the switching power supply. The quality and reliability of the switching power supply depend on its circuit design, production process, and quality of the device. Electrolytic capacitors are an integral part of high-power switching power supplies.
The normal working life of the switching power supply depends on the life of the electrolytic capacitor used by the power supply. The life of the electrolytic capacitor depends on the life of the capacitor itself and the operating temperature.
Electrolytic capacitors vary greatly in their operating life at different temperatures.
Take a famous foreign brand electrolytic capacitor as an example:
Its universal -40 ° C - +105 ° C specification capacitor life guarantee value (at 105 ° C full load conditions) 4000 hours. If we design the capacitor ripple current load value to use up to 85%, then: according to the life estimation formula provided by the capacitor temperature of 65 ° C can only guarantee about 80,000 hours;
The life of the capacitor at 75 ° C can only guarantee about 40,000 hours;
The life of the capacitor at 85 ° C can only guarantee about 20,000 hours;
The life of the capacitor at 95 ° C can only guarantee about 10,000 hours;
From the above calculations: for every 10 °C rise in electrolytic capacitor temperature, the life will be halved.
Schematic diagram of the operating temperature of the electrolytic capacitor:
The self-temperature rise of the power supply : the power supply design of the better power device temperature rise is around 25-30 °C, the design of the relatively poor temperature rise is greater than 35 ° C, the outdoor LED power supply requires waterproof, a sealed enclosure is required, for the protection level Improve the manufacturer's requirements for potting treatment, different colloidal materials cost and cost are different, thermal conductivity is not the same, low-cost adhesives have poor thermal conductivity, and need high temperature baking, which often causes different degrees of invisible damage and tight strain of components. Leave hidden dangers. (The bad heat treatment makes the working environment of the electrolytic capacitor in the housing be like a thermos bottle, and the temperature accumulation cannot be released).
The temperature rise of the lamp itself: Because the large amount of heat generated by the LED itself relies on the housing to dissipate heat, the temperature of the LED lamp housing is reasonably designed to be between 20 ° C and 25 ° C.
Namely: under the working condition of room temperature 25 ° C, the lamp housing temperature is about 45 ° C -50 ° C.
Working environment temperature of lamps: In some areas, the outdoor surface temperature in summer is as high as 40 °C or even higher.
Comprehensive application conditions: The temperature of the capacitor working environment will be greater than 95 °C in harsh environments. It has also been suggested whether ceramic or solid capacitors can be used, but with the current capacitive technology, these two capacitors cannot be made into high voltage and large capacity. Of course, a good saddle needs to be equipped with a good horse. Using a long-life capacitor does not necessarily guarantee the life of the power supply. To improve the life of the power supply, it needs to be improved in many ways: using a higher-life capacitor, improving the power efficiency, and optimizing the power supply. The heat dissipation design optimizes the heat dissipation design of the luminaire. In order to consider the compactness of the luminaire design in order to reduce the weight, many luminaire companies require that the power supply volume be compact and installed in a closed space, and the heat dissipation conditions of the power supply are limited. Therefore, high efficiency, small size and better heat dissipation design are challenges for power supplies.