Brief In order for fluorescent lamps and germicidal lamps to work properly, three conditions must be met: a, the preheating current or filament current of the filament b, high voltage start c, limit the working current Specific analysis The working principle of the electronic ballast is because the gas discharge lamp (such as fluorescent lamp, neon lamp, metal halide lamp, etc.) is a negative resistance electric light source with the characteristics of VI shown in Figure 1, which is a negative value, as can be seen from Figure 1. When the lamp current rises, the working voltage of the lamp decreases, but the supply voltage does not drop. When the extra voltage is applied to the lamp, the lamp current will rise further, and the cycle will eventually burn out the lamp or lamp. The tube is extinguished, so for the lamp to work properly, a ballast element as shown in Figure 2 should be used to limit and stabilize the lamp current. This current limiting device is called a ballast. At present, there are two types of ballasts commonly used in gas discharge lamps: inductive ballasts and high frequency AC electronic ballasts. Because the inductive ballast works at the power frequency mains frequency, it is bulky and heavy, and it also needs to consume a lot of metal materials such as copper and silicon steel. It is difficult to dissipate heat, work efficiency is low, and the lamp has stroboscopic light, so now some electric light source circles Technicians are looking for new methods of ballasting, and high-frequency AC ballasts are an effective method. The principle of ballast is shown in Figure 3. The working characteristic curve of the ballast circuit is shown in Figure 4. In the circuit shown in Figure 2, the operating voltage on the lamp plus the voltage on the ballast element is equal to the supply voltage, which ultimately allows the gas discharge lamp to operate stably. In the circuit shown in Figure 2, the lamp power can be calculated as follows: P=IVα (1) The α in the formula represents the illuminance of the lamp, which is related to the operating voltage and operating current of the lamp. For the inductor ballast, α can be taken as 0.8, and for the high-frequency electronic ballast, α can be taken as 0.99. During the stable operation of the lamp circuit, the voltage on the lamp is stable, so the lamp power mainly depends on the magnitude of the lamp current, and the magnitude of the lamp current is related to the impedance of the ballast element and the level of the power supply voltage, and the power supply frequency is The operation of fluorescent lamps also has an effect, as shown in Figures 5 and 6. For example, for inductor ballast, the impedance of the ballast inductor is ZL=2πfL. The inductance of the inductor ballast is related to the number of winding turns and the size of the core. Therefore, when the power supply frequency is high, the volume of the ballast inductor will also be Smaller. This is why the volume and size of the ballast inductors are small after the high frequency AC electronic ballast circuit is used. At present, some famous universities, research institutes and companies all over the world have invested a lot of power in the research, development and production of high-frequency AC electronic ballasts. For example, the research center led by Professor Li Zeyuan of the University of Virginia Power Electronics Research Center (VPEC) has published relevant papers and experimental reports every year in IEEE Power Electronics, and proposed high-frequency energy feedback, using charge pump power factor correction. The concept of electronic ballasts, Professor S.CUK of the California Institute of Technology (UCT) on single-stage high-power factor electronic ballasts, an E-class electronic ballast for compact fluorescent lamps, Spain, Brazil, Some famous universities, research institutes and companies in Taiwan and Hong Kong have invested in high-level scientific research personnel and laboratories for scientific research and development. At the same time, some famous domestic research institutes and universities have invested a lot of power in scientific research and development. This can be seen from the relevant domestic scientific literature. However, it is undoubted that China is a big country in the world of electronic ballasts, and there are many companies and enterprises engaged in the production of such "green electric light source" products. Especially since the late 1980s and early 1990s, IEC928 (1990), GB15143 (1994) "General requirements and safety requirements for AC electronic ballasts for tubular fluorescent lamps" and IEC929 (1990), GB/T15144 Technical standards such as the performance requirements of AC electronic ballasts for fluorescent lamps have been promulgated and implemented one after another, so that the research, development and production of AC electronic ballasts have unified technical specifications. Due to the small size and low cost of the high frequency AC electronic ballast, and the strict requirements on electromagnetic radiation interference, input power factor, crest factor, reliability and other technical requirements, it is necessary to make a high performance. High-frequency AC electronic ballasts that require low price, small size, low electromagnetic radiation interference, and safe and reliable use are not easy, so they often feel like a simple electronic product, but the technical content is very high. Involved in circuit topology, high frequency electronic conversion, resonant switch (ZVS, ZCS), LC string, parallel resonance, power factor correction (PFC), electromagnetic interference suppression (EMC, EMI), signal sensing, acquisition and control, electronic components Electronic products such as electric light source devices and other aspects of power electronics technology. At the same time, how to measure the technical parameters of high-frequency AC electronic ballast, such as power, high-frequency harmonic components, efficiency, electromagnetic radiation interference (EMI), is also a research hotspot of high-frequency AC electronic ballasts. Practice has proved that to make a high-performance high-frequency AC electronic ballast, you need to understand its lamp load technology characteristics, lamp load and power supply technical requirements, otherwise you have to make a high-performance high. Frequency AC electronic ballasts are also unrealistic.
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How electronic ballasts work