The filamentless hot cathode fluorescent lamp has been in existence for nearly ten years. Through the unremitting efforts of researchers in the past ten years, the filament fluorescent lamp has been completely rewritten in many parameters and characteristics such as luminous efficacy, life and switching times, pipe diameter and mercury supply. The best history. Recently, researchers have further transplanted this technology to UV lamps that are also low-pressure gas discharge lamps, and have achieved even more impressive results.
First, no filament hot cathode from fluorescent light to ultraviolet light
The so-called no filament, "no" here is the verb, that is, the meaning of the filament function is removed. Fluorescent lamps have filaments that are inherent. In the process of production, there is no filament to decompose and decompose the cathode electron powder. There is no fluorescent lamp; especially after the birth of about half a century, the low-frequency driving lamp of the inductor ballast has to be powered by the filament. Warm up before starting. Since the end of the last century, fluorescent lamps, especially energy-saving lamps, have become more and more mature. The initial resonant voltage of lamps can be as high as 3000V under high-frequency driving. Electronic ballasts without filament preheating discrete components can also be started satisfactorily; The resonant frequency of the component is unstable and the randomness is large. It cannot guarantee that the lamp will be broken through in one cycle of the turn-on of the switch tube. It is often necessary to turn the lamp back and forth for N times to start the turn-on lamp; Under bad conditions, the switch is delayed by 0.1s at a time, which also makes the cathode withstand the ion bombardment of the resonant high voltage for several thousand times, while the good quality lamp has good starting characteristics, and N tends to the minimum, so the good lamp is only Suitable for filamentless, the number of switching can be increased without filament, and the short-life of the defective product; therefore, the use of discrete components electronic ballast switch lamp becomes a new method to quickly distinguish the quality of the lamp.
In the past ten years, the filamentless hot cathode fluorescent lamp has been rewritten to the best of filament fluorescent lamps in many parameters and characteristics such as luminous efficacy, life and switching times, pipe diameter and mercury supply. history record. For example, the A60 cover energy-saving lamp made with no filament (Fig. 1) has a luminous efficiency of up to 75 lm/W, a nominal input power of 12 W, a luminous flux of nearly 900 lm, a mercury content of only 0.6 mg per lamp, and a lifetime of 15,000 h. Discrete component electronic ballast drive switch times more than 20,000 times; no filament energy-saving lamp from the diameter of 2.9mm single spiral 3.5W/5.5W (Figure 2) ultra-high surface brightness, can replace the crystal lamp with 15~25W incandescent lamp An IC-driven electronic ballast pulls five mushroom-type lamps 150W, and is ideal for replacing 400W metal halide lamps at a height of 12 meters.
Figure 1, A60 with cover energy saving lamp
Figure 2. Single-screw 3.5W/5.5W filamentless energy-saving lamp
The development of a filament-free hot cathode from a fluorescent lamp to an ultraviolet lamp (Fig. 3) has yielded more promising results through experiments. First of all, the shape of the filament is developed from the "flat wire" of the conventional and fluorescent lamps to the "vertical wire", and the diameter of the third spiral of the filament is expanded to be close to the inner diameter of the lamp; thus the ultraviolet lamp tube is sealed without the double molybdenum plate bracket, Single molybdenum sheet, the inner guide wire is changed to the nickel-plated iron wire hook and directly pressed; the third spiral coil number of the filament can be arbitrarily selected according to the needs. The more the number of turns, the more the electron powder stored in the cathode is, the longer the lamp life is; After the "vertical wire" structure, the design of tungsten wire mg200 should be increased, not only for the aesthetic appearance of the cathode clamping clamp, but more importantly, the cathode-based metal tungsten wire can withstand the enhanced ion bombardment ability, and the lamp switch characteristics are good. Electronic powder heat evapotranspiration is also small. Further, the cathode decomposition utilizes the characteristics that the quartz glass tube can withstand the high temperature above 1000 ° C, the oven temperature is increased on the exhaust vehicle, and the heating source is added to the cathode portion of the lamp tube to ensure that the cathode is heated up to 1000 ° C during the decomposition process. The various parts of the lamp are uniformly heated to 1000 ° C, and the impurity gas released by the electronic powder does not reside on the inner wall of the lamp when it is decomposed, so that the ultraviolet lamp produced is absolutely superior in quality.
Figure 3. No filament hot cathode UV lamp
Based on the above two points or starting point, we have greatly expanded our imagination of UV hot cathode lamps.
First, the diameter of the lamp tube is no longer constrained by a flat wire. The design choice of the tube diameter can approach the cold cathode ultraviolet lamp; this is very beneficial for the production of various portable miniaturized UV lamps, even in the same tube as the cold cathode. The hot cathode can achieve higher UV radiation efficiency in diameter, size and volume.
Second, the life of the lamp can be greatly extended. Under the driving of the most common electronic ballasts, almost all of the lamps end up. The energy-saving lamps are so. The ultraviolet rays are like this. The characterization before the end of life is the consumption of electronic powder. Now, I finally found a way to extend the life of the lamp almost infinitely, because the electronic powder can almost increase indefinitely.
Third, the power can be greatly increased under the limited pipe diameter. For the ultra-high-power ultraviolet lamp that needs to be produced by several tens of hundreds of watts, the pipe diameter can be reduced by at least half under the existing pipe diameter; for example, the T5 pipe diameter It can make 100~150W UV lamp completely, and use IC's boost APFC circuit electronic ballast to drive the lamp, the life can be greatly extended.
Fourth, the amount of mercury in the UV lamp can be reduced by more than 50%. Half of the people in the industry think that the UV lamp is inseparable from mercury. The more mercury is applied, the better. It is actually a misunderstanding. As long as the cold end of the lamp is set properly, After the tube diameter is reduced, the wall load is increased, and the cold end temperature is inevitably increased with the increase of the temperature of the tube. The theoretical value of the mercury content of the lamp can be reduced by half for every 10 °C increase; and the mercury stored in the ultraviolet tube is mainly supplied to the cathode. Due to the above-designed filamentless hot cathode, the switch sputtering and the working heat evaporation are small, and as the above-mentioned exhaust gas decomposition process improves the residual impurity source in the lamp tube is very limited, the design of the reserve mercury amount need not be too conservative.