Abstract: This paper discusses the basic structure and performance characteristics of EEFL, and focuses on the understanding and analysis of the EEFL discharge principle for reference.
Keywords: external electrode fluorescent lamp structure discharge principle electrodeless discharge
1. Introduction EEFL is the abbreviation of External Electrode Fluorescent Lamp. Its structural feature is that there is no electrode inside the lamp tube. The glass tube is filled with working gas and the inner surface is coated with phosphor layer. It can be said that Root "empty pipe". The outer surface of both ends of the EEFL glass tube is covered with a conductive layer or a metal sleeve to form an external electrode that has an important influence on the discharge of the lamp. The name of the EEFL is also derived therefrom.
Figure 1. Schematic diagram of the basic structure of EEFL
1 glass tube 2 trichromatic phosphor layer 3 external electrode 4 working gas (Ne, Ar, Hg mixture)
In order to have a relatively intuitive understanding of the structure and performance characteristics of EEFL, let us do a few experiments first. Take a 3mm diameter glass tube, after normal venting process and fill it with 80 乇氖 gas, seal it off, it looks like a clean and bright "empty" glass tube. At both ends of the transparent glass tube, a layer of aluminum foil is wrapped around the outer surface of the glass tube, and the aluminum foil at both ends of the glass tube is connected to the output end of the CCFL inverter power supply of the cold cathode fluorescent lamp. When the power switch is turned on, it is immediately ignited. The helium gas in the glass tube is discharged and emits a bright red light, like a thin tube neon. In fact, it can be said that this is an external electrode neon.
If the inflation in the glass tube is replaced by a mixture of Ne, Ar, and Hg, and a phosphor layer is applied to the inner wall of the glass tube, the external electrode neon lamp becomes the external electrode fluorescent lamp EEFL. By connecting the output of the corresponding CCFL inverter power supply to its external electrode, it can ignite and illuminate like a CCFL.
In fact, any fluorescent lamp, after the outer surface of both ends of the glass tube is covered with a conductive layer to form an external electrode, constitutes a certain type of EEFL, which can be illuminated with a high frequency power supply of 1-3 kV. This shows that the distance between EEFL and us is so close!
Through the above, we have actually felt the first outstanding feature of EEFL, that is, the structure is simple, the process is simple, and the cost is low.
The second outstanding feature of EEFL is electrical performance, that is, EEFL lamps can be used in parallel, that is, direct parallel ignition. When it is necessary to illuminate multiple EEFLs at the same time (such as the direct-type backlight of an LCD color TV), it is often only necessary to use a high-frequency driving power source to directly illuminate several to tens of EEFLs, which is very simple and cost-effective to use. Lower. It should be noted that almost all gas discharge lamps can not be used directly in parallel, it is rare for EEFL to give us such convenience!
In addition to the above, many sources report that EEFL has higher brightness and longer life than CCFL. Therefore, EEFL is considered to be a product of CCFL technology advancement, and is a new light source that was emerging in the early 21st century and will soon replace CCFL.
Is EEFL really cheaper than CCFL and will replace CCFL? Judging from the actual development in recent years, this is not the case at present. Despite the great interest and expectation of EEFL, there are indeed many companies that try and test EEFL, but they are still in the trial stage, and their production and sales are far from being comparable to CCFL. why? Because the performance consistency and stability of China's EEFL products are not good enough, especially EEFL has high requirements for its supporting high-frequency drive power supply. Many of the existing products can not meet the requirements of use and cannot be used normally. Therefore, the current development of EEFL faces the problem that both the lamp and the supporting circuit need to be further improved.
Second, the discharge principle of EEFL EEFL structure is so simple, lighting is so easy, direct parallel use is so convenient, so that people are interested in contact with it, want to ask the truth, plus the current task of improving EEFL performance is imminent, therefore, It is no longer evasible to find out the research on the discharge principle of EEFL. Only by correctly understanding the basic process of gas discharge in EEFL, starting from the basic concept to improve the structure and process of EEFL, will receive good results.
However, in the papers on EEFL that I have seen, it is always a matter of talking about the discharge principle of EEFL. There are only a few general sentences, and there is no more accurate analysis and discussion. For example, some mention only that it is an electromagnetic induction electrodeless discharge, that is to say, like the well-known stepless fluorescent lamp, this is obviously wrong. Because EEFL cannot have a strong high-frequency magnetic field passing through the lamp tube, it can induce a high-frequency electric field sufficient to ignite the discharge; some mention that the high-frequency electric field is caused by the coupling of the EEFL external electrode and the wall capacitance to the tube. Gas discharge is a high-frequency electrodeless discharge; some are considered to be a gas discharge generated by a high-frequency voltage applied to an external electrode through a glass medium, and are a dielectric barrier electrodeless discharge or the like. According to the definition of "the discharge mode in which the electrode is not exposed to the ionized gas is called the electrodeless discharge", there is no electrode installed in the EEFL tube, and only the outer electrode on the outer surface of the two ends of the glass tube appears to be unobjectionable.
However, in-depth analysis of the gas discharge process occurred in EEFL, it is found that the electrode process is still essential to maintain the EEFL high-frequency discharge. Specifically, the EEFL still has a cathode that emits electrons and a cathode drop of accelerated electrons and positive ions. To illustrate this point, let us revisit the analysis of several cases of high-frequency discharge by gas discharge theory.
The discharge generated by the gas under the excitation of high-frequency energy is called high-frequency discharge, and its current density j is:
j=[nee2υ/me(υ2+ω2)]E (1)
Where E is the electric field strength, ω is the angular frequency of the applied high-frequency electric field, and υ is the effective collision frequency of the electron, υ is calculated by:
υ=3.19×109×P/√Te0.5 (2)
Where P is the gas pressure (mm Hg) and Te is the electron temperature (K).
According to the relative magnitude of the applied high-frequency electric field angular frequency ω and the effective electron collision frequency υ, the high-frequency discharge can be divided into three cases of ω <> 。. When ω< when the frequency of the applied high-frequency electric field is greatly increased to ω≌υ and ω>>υ, the movement of the electrons in the discharge will undergo a fundamental change, and the electrons in the plasma region are constantly moved back and forth by the action of the high-frequency electric field. Increases the probability of electrons colliding ionization. At this time, the stable discharge is no longer required for the electrode process, that is, the cathode is not required to emit electrons, the cathode is not needed, and the cathode drop region is not present, thereby forming a high-frequency electric field. Electrodeless discharge. An example of such a high frequency electrodeless discharge occurs in a radar antenna switch having an operating frequency of about 1000 MHz and a gas pressure in the discharge tube of no more than 20 乇.
In contrast to the above theoretical analysis of high-frequency discharge, the well-known electronic ballast fluorescent lamp ECFL and cold cathode fluorescent lamp CCFL (operating frequency are both 20KHZ-100KHZ) are both ω< Let us return to the gas discharge in the EEFL. The operating frequency of the EEFL is the same as that of the CCFL (20KHZ-100KHZ), and the type and pressure of the aeration are similar to those of the CCFL. Therefore, their discharge types are similar (genus ω). It is important to note that the EEFL is formed by the inner wall of the glass opposite the outer electrode. The inner electrode has a prominent feature, that is, it is innumerable "micro island" shape, because the inner surface of the glass must not be a metal electrode, and its surface is non-conductive, regardless of the inner surface, attracting electrons to form wall charges (or attracting positive Ion and generate secondary electron emission and accumulate positive charge), there is no electrical communication between the point, we can call it "micro island" electrode. Therefore, it can be considered that the internal electrode of EEFL is composed of external electrode The corresponding "micro island" electrode on the inner wall of the glass is composed.
In summary, we can draw a schematic diagram of the equivalent electrode structure of the EEFL, as shown in Figure 2:
Figure 2 Schematic diagram of EEFL equivalent electrode structure
1 external electrode 2 discharge space 3 glass capacitor 4 "micro island" electrode
There is a view accepted by most people that the high-frequency electric field is introduced into the EEFL discharge space by the external electrode through the glass-wall capacitor, and acts directly on the plasma region of the discharge to generate and maintain a stable high-frequency electrodeless discharge. We will not talk about the negation of this view by the aforementioned theory, but from the perspective of counter-evidence. If a high-frequency electric field is introduced, a stable discharge can be maintained without an electrode action. Then, if the CCFL with the same EEFL discharge condition directly introduces a high-frequency electric field into the discharge space, why must the electrode process be used to maintain a stable discharge? If the electrode process is really insignificant, why does the CCFL electrode process concentrate so much power that it has an extremely important impact on the discharge performance?
In order to investigate the presence or absence of the inner wall electrode of the EEFL, we can judge by observing whether there is a cathode drop zone on the inner wall surface corresponding to the outer electrode of the EEFL, and the actual photograph taken is shown in Fig. 3. It can be clearly seen from Fig. 3 that the luminescence of the inner wall of the plasma zone glass is quite different from the luminescence of the inner wall of the glass corresponding to the outer electrode. The inner wall surface corresponding to the plasma region does not emit red light, and the inner wall surface corresponding to the outer electrode emits red light similarly to the surface of the CCFL electrode. The reason is very clear. The electron energy in the plasma region of the fluorescent lamp is low, and it cannot cause the helium atom to be excited. Only when the electron is accelerated into a high-energy electron in the cathode drop region can the germanium atom be excited and return red light when returning to the transition.
Figure 3 Observing the photo of the inner wall of the EEFL glass
In addition, we dissected the EEFL tube after thousands of hours of life test. The surface condition of the glass wall corresponding to the plasma area changed little, while the inner wall of the glass corresponding to the outer electrode was severely blackened. This is obviously caused by the positive ion bombardment of the cathode. as a result of.
Finally, we comparatively measured the luminous efficacy curves between the output luminous flux and the output power of CCFL and EEFL of the same structure (same glass, same diameter, same production process), and found that their shapes and data are quite close. This also shows that the same type of discharge is produced in EEFL and CCFL, and there is no significant difference in the discharge principle. It will not be described in detail here.
The above analysis of the EEFL discharge principle may have important practical significance, that is, to improve the performance of the EEFL, attention should be paid to the surface state of the inner wall of the two ends of the tube as the inner electrode, and what kind of process, material or even some kind of coating is used. It is possible to significantly improve the performance and longevity of the EEFL.
Third, the application prospects of EEFL EEFL as the advertising, photos, pictures of ultra-thin light boxes and flat-panel TV LCD color TV backlight, especially the large-screen LCD color TV direct-type backlight is very optimistic, as long as the performance is reliable Will be listed as the preferred product by many users, because of the unique advantages of the direct parallel use mentioned above, and the lower price brought by its lower production cost. A Japanese company that produces LCD TVs has visited almost all CCFL and EEFL production plants in Nanjing not long ago. He claims that LCD TVs will be widely popularized. In the next three years, the demand for CCFL or EEFL will increase sharply and supply will be in short supply. The reason is that the cost of the LCD screen will drop one step at a time, making it difficult for other flat-panel TVs to compete. I believe his prediction. Therefore, the application prospect of EEFL can be very optimistic with the promotion of LCD TVs and ultra-thin light boxes. People must say, don't forget the LED, LED as the backlight will be the last attribution. However, regardless of the final situation, I think that within 5 to 10 years, LEDs are difficult to weather. It is also the information provided by the Japanese person mentioned above. He said that his company has solved all the technical problems of using LED to make several major specifications of LCD TV backlights. They have made good samples and can be successfully displayed, but the cost is Very high. For example, a backlight for a medium screen uses 3,500 LEDs with high color rendering index, high brightness and long life. The cost is high. I think it may be a lot after five or even ten years. Obstacles.
References [1] "Gas Discharge - Application of Plasma Physics" by Peng Guoxian, 1988
[2] "The Propagation of Electromagnetic Waves in Plasma" B.JI. Jinzbao. Qian Shan Harmony 1978
[3] "Gas Discharge and Ion Tube" Chengdu Institute of Telecommunications Engineering Selected 1956
[4] "The Lifetime and pinholes in the External Electrode Fluorescent Lamps" DHGill et al, SID 05 DIGEST (200)
Editor: Chen Dan
Multi-core cpu is more and more popular, people are used to take dual core processors laptop before. However, Quad Core Laptop is becoming selling like a hot cake nowadays. You can find Quad Core Processor Laptop at our store, like I3 Quad Core Laptop,I7 Quad Core Laptop, I5 Quad Core Laptop, intel celeron J4125 or N5095 15.6 Inch Laptop, even N4120 quad core 14 Inch Laptop, etc. Therefore, you can just share the parameters prefer, like size, cpu, ram, rom, gpu, application scenarios, thus save much time to get a win-win solution.
Do you know the reason why more people choose quad core device? The core reason is that heavier tasks people need to finish at a higher speed than before. Nowadays quick rhythm is becoming the main style in city even everyone is eager to downshifting. So more powerful laptop, computer, mobile phone is a trend, though most functions never are used in lifetime.
Other 15.6 inch Gaming Laptop or 14 Inch Gaming Laptop is becoming the most popular level at the market.
Quad Core Laptop,I3 Quad Core Laptop,I7 Quad Core Laptop,I5 Quad Core Laptop,Quad Core Processor Laptop
Henan Shuyi Electronics Co., Ltd. , https://www.shuyipcs.com