Hot Cathode Fluorescent Lamps Research Articles

A Dimming Method for Hot Cathode Fluorescent Lamp Using a Resonant Inverter Operating at Fixed Switching Frequency

This paper describes a dimming method for hot cathode fluorescent lamp (HCFL) using a resonant inverter operating at fixed switching frequency. The proposed method is based on burst dimming and decreases the inverter output voltage during the burst-off period by changing the switching pattern of the inverter. Consequently, the lamp can be turned OFF, while the filaments of lamp are kept preheated without adding an inverter for preheating. Once the lamp is turned OFF, N-times resonant mode (where N means a natural number) occurs because the characteristic of the resonant circuit (which depends on lamp impedance) changes drastically. This mode keeps the root mean square of filament currents large enough to ensure long lamp life. Moreover, the inverter operates in zero-voltage-switching resonant mode during both the burst-on and burst-off periods. Experimental results showed that stable burst dimming and preheating characteristics were attained. The proposed method thus contributes to achieving long lifetime, small size, and low cost of lighting system for HCFLs.

ELECTRONIC BALLAST IC WITH ADJUSTABLE PREHEAT TIME AND MINIMUM FREQUENCY FOR HOT FLUORESCENT LAMP

A novel ballast control IC is presented, which fully satisfies specific needs of hot cathode fluorescent lamp and significantly simplifies the external circuit design with the great reliability, generality and practicability. Integrated with a simple multi-frequency oscillator, the IC obtains adjustable preheat-time by controlling frequency changing rate with an external capacitor, and adjusts the minimum frequency by controlling minimum charging current with an external resistor. And a steady dead-time can also be achieved. Based on 0.5 μm BCD process, the HSPICE simulation was done with 14 V voltage supply. While a 1 μF capacitor and a 100 kΩ resistor are utilized in the external circuit, this IC gives out a preheating frequency up to 175 kHz and the minimum working frequency is 75 kHz. A high frequency preheating time of 1 s and a steady dead-time of 2 μS can also be achieved.

An Auxiliary Self-Oscillating Preheating System for Self-Oscillating Fluorescent Lamp Electronic Ballasts

The fluorescent lamp lifetime is very dependent of the start-up lamp conditions. The lamp filament current and temperature during warm-up and at steady-state operation are important to extend the life of a hot-cathode fluorescent lamp, and the preheating circuit is responsible for attending to the start-up lamp requirements. The usual solution for the preheating circuit used in self-oscillating electronic ballasts is simple and presents a low cost. However, the performance to extend the lamp lifetime is not the most effective. This paper presents an effective preheating circuit for self-oscillating electronic ballasts as an alternative to the usual solution.

Comparative Analysis and Experiments of Resonant Tanks for Magnetically Controlled Electronic Ballasts

This paper presents a comparative analysis and experiments of resonant tanks for magnetically controlled electronic ballasts, focusing on their behavior and performance when driving hot cathode fluorescent lamps. Four different resonant tanks are analyzed: LC, LCC, capacitive impedance inverter, and CLL. The analysis is performed using a 36-W fluorescent lamp, which has been previously tested and modeled experimentally. The lamp model is used to derive the dimming characteristics of the different resonant tanks when using the resonant inductance as a control parameter. Analysis and experiments showed that instabilities appear when the lamp power is decreased below a minimum value, which effectively limits the dimming range of the ballast. Nevertheless, the proposed control method can be used to control lamp power in an adequate range provided that the resonant tank should be selected and designed properly.

LCD backlights, light sources, and flat fluorescent lamps

Abstract— Backlights are indispensable for the operation of LCDs. Light sources or lamps are the core components of backlights. There are many types of light sources for backlights such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), hot‐cathode fluorescent lamps (HCFLs), flat fluorescent lamps (FFLs), and light‐emitting diodes (LEDs). Recently, FFLs are becoming one the most interesting light sources for LCD‐TV backlights. Channel profiles and the structure of FFLs in more detail are discussed in this paper. The channel profile of FFLs with maximum brightness uniformity was designed, fabricated, and characterized. The FFL backlight demonstrated 10,500 nits and the total power consumption was 110 W at room temperature.

면광원 램프 및 이를 이용한 조명 기기의 효율 특성 연구

LCD(liquid crystal display) TV용 백라이트의 광원으로서 면광원이 개발되었으며, 이를 이용한 조명 기기를 제작 및 평가하였다. 면광원은 유리성형을 통하여 채널을 형성하였으며 채널의 모양을 최적화하여 면광원을 이용한 조명 기기의 효율을 향상시킬 수 있었다. 본 논문에서는 특히 현재 주로 사용되고 있는 형광등과의 비교 평가를 통하여 조명용 면광원의 광 효율 및 조도 특성에 관한 성능을 평가하였다. 채널의 구조가 최적화된 면광원을 이용하여 제작된 32

Setting the Preheating and Steady-State Operation of Electronic Ballasts, Considering Electrodes of Hot-Cathode Fluorescent Lamps

This paper presents a new methodology for the adjustment of the preheating process and steady-state operation of electronic ballasts intended for hot-cathode fluorescent lamps. The classical series-resonant parallel-loaded half-bridge inverter is the power stage analyzed in this paper. In addition, the preheating process is based on the imposition of a constant rms current through the electrodes, in order to provide a proper value of the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ratio before the lamp start. According to the proposed methodology, it is possible to set suitable operating points for the electronic ballast, considering optimal conditions for the lamps electrodes. Therefore, the proposed methodology for setting the preheating and steady-state operation is a complete platform to the design of electronic ballasts for hot-cathode fluorescent lamps

Model for Electrodes' Filaments of Hot Cathode Fluorescent Lamps, During Preheating With Constant rms Current

This paper presents a new model for the representation of electrodes' filaments of hot-cathode fluorescent lamps, during preheating processes based on the injection of currents with constant root mean square (rms) values. The main improvement obtained with this model is the prediction of the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ratio during the preheating process, as a function of the preheating time and of the rms current injected in the electrodes. Using the proposed model, it is possible to obtain an estimate of the time interval and the current that should be provided by the electronic ballast, in order to ensure a suitable preheating process. This estimate of time and current can be used as input data in the design of electronic ballasts with programmed lamp start, permitting the prediction of the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ratio during the initial steps of the design (theoretical analysis and digital simulation). Therefore, the use of the proposed model permits to reduce the necessity of several empirical adjustments in the prototype, in order to set the operation of electronic ballasts during the preheating process. This fact reduces time and costs associated to the global design procedure of electronic ballasts

The Study on the Relation between the Cathode Fall Voltage and the Electrode Material of the CCL

To improve the efficiency of the cold cathode lamp (CCL), it is important to select the optimum electrode material to reducing the cathode fall voltage (CFV). Furthermore, it is necessary to understand the relationship between the electrode material and the CFV. Considering the above, we measured the CCL’s CFV with an indirect CFV measurement method using a hot cathode fluorescent lamp. By observing the negative glow of the electrode, we investigated the relationship between the CFV and the negative glow condition. The results showed that there is a relationship between the CCL’s CFV and the γ coefficient of the electrode. Moreover, they make it clear that there is a relation between the CFV and the negative glow condition of each electrode material. We conclude that the CFV measurement method is useful for estimating the performance of a CCL’s electrode.

18.3: Life Aspects of HCFL Light Sources in LCD Backlighting Application

With the application of Hot Cathode Fluorescent Lamps (HCFL lamps) in LCD Backlighting applications high brightness backlights with a good motion fidelity and dynamic contrast can be realized. In this contribution the operation principles will be discussed. Experimental data will be presented to show that with HCFL lamps it is possible to achieve a good lifetime performance, a good light output maintenance performance and good chromaticity maintenance.

The Cathode Fall Voltage of Low Current Fluorescent Lamps

The characteristics of hot cathode fluorescent lamps in low current regions (10∼40mA) were investigated by experiments and numerical analysis. A quantitative correlation between the cathode fall voltage and the lifetime was obtained. If the cathode fall voltage is less than or equal to 14V, arc discharge can be maintained stably during the lifetime, and hence, the life reliability of lamps can be improved. In order to reduce the cathode fall voltage for a given lamp current, it is effective to increase Ar gas pressure, and to decrease the surface area of the coils. The cold spot temperature is not effective to reduce the cathode fall voltage in the range of 10 to 60°C. The relation between the lamp design parameters and the cathode fall voltage was analyzed numerically on the basis of a modified theoretical model. The calculated results support the experimental results.

小電流熱陰極蛍光ランプの陰極降下電圧

The characteristics of hot cathode fluorescent lamps in low current regions (10∼40mA) were investigated by experiments and numerical analysis. A quantitative correlation between the cathode fall voltage and the lifetime was obtained. If the cathode fall voltage is less than or equal to 14V, arc discharge can be maintained stably during the lifetime, and hence, the life reliability of lamps can be improved. In order to reduce the cathode fall voltage for a given lamp current, it is effective to increase Ar gas pressure, and to decrease the surface area of the coils. The cold spot temperature is not effective to reduce the cathode fall voltage in the range of 10 to 60°C. The relation between the lamp design parameters and the cathode fall voltage was analyzed numerically on the basis of a modified theoretical model. The calculated results support the experimental results.

熱陰極蛍光ランプを用いたカラー液晶ディスプレイ用バックライトの設計

The design of a back-lighting system for color LCDs using hot cathode fluorescentlamps requires consideration of the lamps' life, heat evolution and thin making. We developed a long life hot cathode fluorescent lamp whose diamiter is 10 mm. The improved cathode design, installation of getter and pre-heat operation brought about an excelent long life of more than 5000 hrs. under continuous operation and 60000-80000 cycles under flickering test. We described the practical heat design of the back-lighting system. The center-gap cored transformer of the inverter contributed to lowering the heat evolution of the system, when the inverter was packed in a chassis to keep the display system off an electro-magnetic interference. As the exhaust tip of the lamp was settled outside the lamp house, the lamp was easy to re-start at high surface temperature of the lamp above 100°C. The lamp showed good adaptability to edge-lighting of a thin back-lighting system with little increase in temperature of the illumination surface. Moreover we discussed the possibility of the possibility ofthe application of this system for a re-chargable battery driven hand-held conputer.

小形熱陰極蛍光ランプの長寿命化の検討

小形熱陰極蛍光ランプの長寿命化の検討

熱陰極蛍光ランプの陰極降下電圧に関する数値解析

熱陰極蛍光ランプの陰極降下電圧に関する数値解析

小電流熱陰極蛍光ランプの陰極降下電圧に関する検討

小電流熱陰極蛍光ランプの陰極降下電圧に関する検討

The Starting of Fluorescent Lamps

Methods of starting hot-cathode fluorescent lamps may conveniently be divided into three categories, which together cover most, if not all, of the common starting devices. The paper discusses the processes occurring and the factors which affect the ease of starting when a lamp is started by means typical of each of these basic methods. Data are given which show how starting is affected by lamp parameters and conditions external to the lamp. The choice of starting method is briefly discussed with reference to the limitations of the more common types.

Hot Cathode Fluorescent Lamps with Auxiliary Plate (II)

The test of hot cathode fluorescent lamps with auxiliary plates have been carried on at the State Osaka Railway Bureau since April in 1953.In this paper we are to report the results of the fundamental measurements of these lamps.The operating circuit for these lamps is shown in Fig. 1. The property of our lamps differs from that of commercial lamps in several points as will be stated below.1. Usually commercial lamps have the directly heated filament type cathode. Our lamps, however, have not only the same catode as that of commercial lamps but the indirectly heated filament type cathode Fs and F (Fig 1). The operating life of these lamps is very long.2. Electro-magnetic type relay was used in order to start these lamps. When starting, the auxiliary discharge current between the auxiliary plate G and the directly heated filament type cathode Df...(G and Df are both at the positive side of d. c. source)...is the working current of the relay. Once it was started, main are current becomes the working current.3. R1 and R2 are the auxiliary resistances which were used in order to give the potential difference between G and Df. M1 and M2 are the coil of the relay and P is the contact. In this device even if the source voltages drop to 75V, our lamps can easily start. Starting time is abott 0.5-1sec.4. L1 and L2 are the choke coils which are used to give the transient high voltages to the lamp for starting. These two coils are set at each side power source, and thus we can minimize the bulk of the choke coil because the choke coil that is connected to negative side of d. c. source contributes mainly to the starting of the lamp. In this circuit, the polarity of the power sourceis changed by a change-over switch.5. We succeeded to delay the time when the so-called dark-end effect is observed, by using this indirectly heated filament type cathode. At the temperature up to 0°C, we did not find this effect for about 50 hours. Further practical tests for these lamps are now going on well in our laboratory.

Hot Cathode Fluorescent Lamps with Auxiliary Plates (1)

Hot Cathode Fluorescent Lamps with Auxiliary Plates (1)

The dimming of low-pressure discharge lamps

The fundamental requirements for the satisfactory dimming of low-pressure hot-cathode and cold-cathode fluorescent lamps are discussed. D.C. operation is first considered, and the treatment is then developed to cover a.c. circuits. Lamp stability is considered from the points of view of smooth control of current, supply-voltage variation, and intermittent extinction. Lamp circuits are generalized in terms of Thevenin's theorem, and the ideas of voltage control and impedance control are introduced. Practical circuits are discussed, the difficulties of multiple-lamp control, and the means for overcoming these, being mentioned. The separate-impedance method of control is described by reference to several circuits, and methods of unifying the control are suggested.