| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 101 === Facing the global energy crisis and the growing climate warming problem, and to find new ways of energy saving has become a topic of global concern. The light-emitting diode (LED) is a solid-state light source, following the incandescent, fluorescent, high intensity discharge lamps (such as high-pressure sodium lamps and metal halide lamps) light sources. Significantly enhancing the luminous efficiency, and having the advantages of long life, miniaturization, and easily driving, LED lighting gradually replaces the traditional light sources, and becomes the mainstream light source for the latest generation of lighting systems. In many lighting systems, table lamps have become the most auxiliary lighting source while working or reading, the future is bound to gradually replace today''s lamp light sources as LED. Therefore, this study is based on a table lamp of LED in an external 5V DC power supply or a USB powered condition to explore the performance of both analog and pulse-width modulation constant current dimming power efficiency and brightness. I hope the measurement results can suggest or provide the necessary research reference.
This paper presents two dimming circuit structure, from simulation data that shows analog dimming circuit efficiency is low but the price is cheaper, the price difference in filtering flyback element. The inductance price of 0.08990 U.S. dollars, diodes prices of 0.06858 U.S. dollars, both the total spread of 0.15848 U.S. dollars. In dimming efficiency performance, both exactly are opposite trend; analog dimming, the higher the efficiency of adjusting the more bright, and the pulse-width modulation circuit, adjusting lower of the light that efficiency are more bright. This dimming when 50% of the power as the difference between the power comparison, analog power consumption of 2.5 watts and pulse-width modulation power of 1.85 watts , a difference of 0.65 watts. If every night for approximately three hours, calculation of one year, assuming 1000 hours a year, which is the year tariff spread of 0.65 degrees per kWh electricity 0.1 U.S. dollars, year electricity charge difference of 0.065 U.S. dollars, the cost differences less than 0.15848 U.S. dollars, need 0.15848/0.065, = 2.438 U.S. dollars, that is using to two and a half years of time.
LED be used life time more than ten thousand hours, but the general table lamp warranty in the following three years, if a heavy user, may should select the products are manufactured to the pulse-width modulation circuit, while the mild users may to choose the cheaper analog dimming products are cost-effective, and luminous uniformity, there will be no interference with the radiation of high frequency pulsating DC.
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