JP2004127540A - Fluorescent lamp lighting method and fluorescent lamp lighting device - Google Patents

Abstract

An object of the present invention is to provide a fluorescent lamp lighting means capable of suppressing the consumption of an internal electrode and a rise in the temperature of a tube wall near the internal electrode, and obtaining a required brightness over the entire length.
A glass tube (16) having a phosphor coating (15) formed on an inner wall thereof and containing a discharge medium containing at least a rare gas, and lead wire terminals (17a, 17b) drawn out and sealed at both ends of the glass tube (16). A fluorescent lamp having a pair of internal electrodes 18a and 18b and an external electrode 19 formed on the outer peripheral surface of the glass tube 16 by periodically applying an AC voltage.
The low voltage side of the power supply 21 that generates a periodic AC voltage is connected to the external electrode 19, and the high voltage side is connected to the pair of internal electrodes 18a and 18b so as to be switchable. It is characterized by switching on and lighting.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a discharge lamp driving device suitable for a backlight light source or the like which can achieve high luminance and can be stably lit.
[0002]
[Prior art]
For example, with the spread of personal computers and the like, liquid crystal display devices used for personal computers, navigation and the like are required to have high performance and long life. In these configurations, a cold cathode fluorescent lamp is generally used as a backlight light source, but further improvement in the performance of the light source system is also expected.
[0003]
In response to this expectation, an external electrode fluorescent lamp whose configuration example is shown in cross section in FIG. 8 has been developed. That is, a glass tube 2 in which a phosphor film 1 is formed on the inner wall surface and a rare gas (discharge medium) mainly composed of xenon is hermetically sealed, and a lead terminal 3 is led out to one end side of the glass tube 2. An external electrode fluorescent lamp is used which has an internal electrode 4 which is sealed by sealing, and an external electrode 5 which is spirally wound on the outer peripheral surface of the glass tube 2 at a required pitch over substantially the entire length in the tube axis direction. It is getting.
[0004]
Here, the glass tube 2 has an outer diameter of about 1.2 to 10.0 mm and a length of about 50 to 800 mm, and is filled with a rare gas mainly composed of, for example, xenon gas as a discharge medium. In FIG. 8, reference numeral 6 denotes a light-transmissive heat-shrinkable tube that covers the winding surface of the external electrode 5 and has a function of preventing the winding position of the external electrode 5 from being shifted. The end 5a of the external electrode is fixed to a lead terminal 7 implanted at the other end sealing portion of the glass tube 2.
[0005]
The external electrode fluorescent lamp is connected to the internal electrode 4 via the lead terminal 3 and to the external electrode 5 via the lead terminal 7, and from the power supply (inverter) 10 side via the voltage supply lines 8 and 9, a required periodicity. When an AC voltage (for example, 1 to 3 KV) is applied, discharge by both electrodes 4 and 5 starts, and ultraviolet rays are radiated in the glass tube 2. The emitted ultraviolet light is converted into visible light by the phosphor film 1 on the inner wall surface of the glass tube 2, and functions as a fluorescent lamp having good luminous efficiency and stable lighting.
[0006]
[Problems to be solved by the invention]
However, the conventional fluorescent lamp lighting method has the following disadvantages. For example, as the size of a liquid crystal display device increases, the length of a fluorescent lamp is required as a backlight source. However, in order to obtain required light emission over the entire length of the glass tube 2, discharge is performed over the entire glass tube 2. In order to widen the voltage, it is necessary to set the applied voltage to be much higher as shown by the straight line a in FIG. Here, spreading the discharge over the entire length of the glass tube 2 involves a problem that the tube current increases as shown by the straight line b in FIG.
[0007]
This point will be described in more detail. As shown schematically in FIG. 9A, when a positive column expands in the radial direction of the glass tube 2 over the entire length of the glass tube 2 (diffusion positive column). In addition, the luminance of the phosphor can be almost uniformly increased over the entire length. However, when the tube current is increased in order to make the glass tube 2 longer and discharge the entire length of the glass tube 2, as shown schematically in FIG. It becomes a thin linear state (contracted positive column). Here, in the state of the contracted positive column, the brightness of the phosphor in the region of the contracted positive column becomes less than half the brightness of the region in the diffused positive column state. That is, as shown in FIG. 10, uneven brightness occurs in the axial direction of the glass tube 2, and the glass tube 2 does not function as a fluorescent lamp exhibiting substantially uniform brightness over the entire length. Therefore, in the conventional lighting method, there is a limit to the length of the arc tube in forming and securing a uniform diffused positive column region, which limits the size of the backlight.
[0008]
In addition, since the discharge is performed in the entire area of the long glass tube 2, if the tube current is set high, there is a problem that the wear of the internal electrode 4 due to the sputtering during the lighting life is promoted and the life is shortened. Further, since the entire current flows intensively into the internal electrode 4 sealed on one end side, the temperature of the tube wall near the internal electrode 4 rises, and in the process of using the same, there is a possibility of adversely affecting adjacent peripheral members. .
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and suppresses the consumption of internal electrodes and a rise in tube wall temperature in the vicinity of the internal electrodes, and achieves a required substantially uniform brightness and brightness over the entire length of the fluorescent lamp. It is an object of the present invention to provide a lighting means for the obtained fluorescent lamp.
[0010]
[Means for Solving the Problems]
The lighting method of a fluorescent lamp according to the present invention is directed to a glass tube in which a phosphor film is formed on an inner wall surface and a discharge medium containing at least a rare gas is sealed, and lead wire terminals are led out to both ends of the glass tube to be sealed. A method of lighting a fluorescent lamp having a pair of internal electrodes and an external electrode formed on the outer peripheral surface of the glass tube by applying an AC voltage,
One output terminal of the power supply for generating the AC voltage is connected to an external electrode, and the other output terminal of the power supply is switched and connected to a pair of internal electrodes at a predetermined cycle.
[0011]
In the lighting method of a fluorescent lamp according to the present invention, the predetermined switching cycle is the same as the cycle of the AC voltage or a cycle that is an integral multiple thereof.
[0012]
A lighting device for a fluorescent lamp according to the present invention is a glass tube in which a phosphor film is formed on an inner wall surface and a discharge medium containing at least a rare gas is sealed, and lead wire terminals are drawn out and sealed at both ends of the glass tube. A pair of internal electrodes, and a fluorescent lamp having an external electrode formed on the outer peripheral surface of the glass tube, an AC power supply that generates an AC voltage applied to the pair of internal electrodes and the external electrode of the fluorescent lamp, Switching means for alternately applying an alternating voltage generated by a power supply between one of the pair of internal electrodes and the external electrode, and between the other of the pair of internal electrodes and the external electrode at a predetermined cycle. It is characterized by the following.
[0013]
In the lighting device for a fluorescent lamp according to the present invention, the predetermined switching cycle is the same as the cycle of the AC voltage or a cycle of an integral multiple thereof.
[0014]
In the lighting device for a fluorescent lamp of the present invention, a phosphor film is formed on an inner wall surface, and a glass tube in which a discharge medium containing at least a rare gas is sealed, and lead wire terminals are led out to both ends of the glass tube. A fluorescent lamp having a pair of internal electrodes sealed and an external electrode formed on the outer peripheral surface of the glass tube, and an AC voltage intermittently at a predetermined cycle between one internal electrode and the external electrode of the fluorescent lamp. And a second AC power supply for applying an AC voltage intermittently at a predetermined period between the other internal electrode and the external electrode of the fluorescent lamp, wherein the first AC power supply And the second AC power supply is characterized in that the phases of the intermittent AC voltage generation are different from each other.
[0015]
Further, in the fluorescent lamp lighting device according to the present invention, the second AC power supply stops generating the AC voltage during a period in which the AC voltage is supplied from the first AC power supply. Is what you do.
[0016]
The lighting means of the fluorescent lamp according to the present invention is characterized in that an AC voltage (sine wave voltage or rectangular wave voltage) is applied between an internal electrode sealed in a glass tube and an external electrode provided over the entire outer surface of the glass tube. The means for driving by applying and lighting is characterized by the following points. That is, the fluorescent lamp has internal electrodes opposed to each other at both ends of the glass tube, and an external electrode is mounted on the outer peripheral surface of the glass tube, and when power is supplied between the external electrode and the internal electrodes, a pair of internal electrodes is connected to the internal electrode. By periodically and alternately changing the power supply, apparently, the required diffused positive column is always formed over the entire length of the glass tube. As a result, even in the case of a long glass tube, a uniform diffused positive column is formed. The essence is to obtain light emission of brightness and luminance.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment will be described with reference to FIGS. 1, 2, 3, 4, 5, 6 and 7.
[0018]
FIGS. 1A and 1B are schematic diagrams for explaining a schematic configuration and a driving operation of a lighting means of a fluorescent lamp according to a first embodiment. 1A and 1B, the fluorescent lamp 14 has the following configuration. That is, a glass tube 16 in which a phosphor film 15 is formed on the inner wall surface and a rare gas (discharge medium) mainly composed of xenon is hermetically sealed, and lead terminals 17a and 17b are provided at both ends of the glass tube 16, respectively. And a pair of internal electrodes 18a, 18b sealed to face each other, and external electrodes 19 spirally wound on the outer peripheral surface of the glass tube 16 at a required pitch over substantially the entire length in the tube axis direction. An external electrode fluorescent lamp having:
[0019]
Here, the glass tube 16 has an outer diameter of about 1.2 to 15.0 mm and a length of about 50 to 800 mm, and is filled with a rare gas mainly composed of, for example, xenon gas as a discharge medium. Also, the internal electrodes 18a and 18b can be periodically switched by the switch element 22 to the high voltage side of the power supply 21 that periodically generates an AC voltage (rectangular wave voltage) via the voltage supply lines 20a and 20b. Connected. Further, the lead terminal 19a of the external electrode 19 is connected to a low voltage side of a power supply 21 that generates an AC voltage (rectangular wave voltage) via a voltage feed line 20c. Reference numeral 23 denotes a light-transmissive heat-shrinkable tube that covers the winding surface of the external electrode 19 and has a function of preventing the winding position of the external electrode 19 from being shifted.
[0020]
The fluorescent lamp 14 is connected, for example, to the internal electrode 18a via the voltage supply line 20a and the lead terminal 17a, and to the external electrode 19 via the voltage supply line 20c and the lead terminal 19a. When the alternating voltage on the low voltage side is selectively applied, discharge is started by both electrodes 18a and 19, and a diffused positive column is generated on the side of the internal electrode 18a in the glass tube 16, and ultraviolet rays are mainly generated in the diffused positive column region. Is converted into visible light by the phosphor film 15 on the inner wall surface of the glass tube 16. On the other hand, the high voltage side AC voltage of the power supply 21 is applied to the internal electrode 18b via the voltage supply line 20b and the lead terminal 17b, and the low voltage side AC voltage is applied to the external electrode 19 via the voltage supply line 20c and the lead terminal 19a. When a voltage is selectively applied, discharge is started by the two electrodes 18b and 19, and a diffused positive column is generated on the side of the internal electrode 18b in the glass tube 16. The light is converted into visible light by the phosphor film 15 on the wall surface. That is, when the alternating voltage on the high voltage side of the power supply 21 is periodically switched and applied to the internal voltages 18a and 18b, a diffused positive column is formed over the entire length of the glass tube 16, and as shown in FIG. And uniform brightness / brightness can be obtained over the entire range.
[0021]
The timing of alternately switching the high-voltage side AC voltage of the power supply 21 with respect to the internal voltages 18a and 18b is performed in synchronization with the rectangular wave voltage (AC voltage) output from the power supply 21. That is, the timing chart of the switching element 22 may be, for example, as shown in FIG. 3A, alternately switching to the voltage supply line 20a or 20b every one cycle of the AC voltage, or as shown in FIG. The voltage supply line 20a or 20b is alternately switched every two periods of the rectangular wave voltage, or a voltage pause period is provided between the rectangular wave voltages as shown in FIG. 22. Note that, in the case of a method in which switching is performed by the switching element 22 during the voltage suspension period, it is possible to cope with a delay in switching of the switching element 22.
[0022]
In the switching lighting drive, the relationship between the length of the glass tube 16 (the length of the fluorescent lamp) and the output voltage of the power supply 21 is, as shown by the straight line A in FIG. On the other hand, since it can be set relatively low, wear due to the sputtering of the internal electrodes 18a and 18b is also suppressed, and the life of the lamp is extended. Further, the relationship between the length of the glass tube 16 (the length of the fluorescent lamp) and the current flowing through each of the internal electrodes 18a and 18b is, as shown by the straight line B in FIG. Has been greatly improved. In addition, an increase in the temperature of the tube wall near the internal electrodes 18a and 18b is also suppressed, and the risk of adversely affecting the peripheral portion is also reduced.
[0023]
FIGS. 6A and 6B are schematic diagrams for explaining a schematic configuration and a driving operation of the lighting means of the fluorescent lamp according to the second embodiment. 6A and 6B, the configuration of the fluorescent lamp 14 is basically the same as that of the first embodiment except that a power supply 21 for generating a periodic AC voltage is provided for each of the internal electrodes 18a and 18b. Since this is the same as the case, detailed description of the configuration is omitted. That is, in the case of the second embodiment, the internal electrodes 18a and 18b are periodically switched to the high voltage side of the power supplies 21a and 21b that generate an AC voltage (rectangular wave voltage) via the voltage supply lines 20a and 20b. Connected as possible. Further, the lead terminal 19a of the external electrode 19 is configured to be connected to the low voltage side of power supplies 21a and 21b that generate an AC voltage (rectangular wave voltage) via a voltage feed line 20c.
[0024]
In the fluorescent lamp 14 according to the second embodiment, for example, an AC voltage on the high voltage side of the power supply 21a is applied to the internal electrode 18a via the voltage supply line 20a and the lead terminal 17a, and the voltage supply line 20c and the lead terminal 19a. When an AC voltage on the low voltage side is selectively applied to the external electrode 19 via the respective electrodes, discharge by the two electrodes 18a and 19 starts, and a diffused positive column is generated on the internal electrode 18a side in the glass tube 16, and this is mainly caused. Ultraviolet light is converted into visible light by the phosphor film 15 on the inner wall surface of the glass tube 16 in the diffusion positive column region. On the other hand, the high voltage side AC voltage of the power supply 21b is applied to the internal electrode 18b via the voltage supply line 20b and the lead terminal 17b, and the low voltage side AC voltage is applied to the external electrode 19 via the voltage supply line 20c and the lead terminal 19a. When a voltage is selectively applied, discharge is started by the two electrodes 18b and 19, and a diffused positive column is generated on the side of the internal electrode 18b in the glass tube 16. The light is converted into visible light by the phosphor film 15 on the wall surface. That is, when the alternating voltage on the high voltage side of the power supplies 21a and 21b is periodically switched and applied alternately to the internal voltages 18a and 18b, a diffused positive column is formed over the entire length of the glass tube 16, as shown in FIG. As described above, uniform brightness and luminance can be obtained over the entire length.
[0025]
The timing of alternately switching the high-voltage side AC voltages of the power supplies 21a and 21b with respect to the internal voltages 18a and 18b is controlled by controlling the phases so that the power supplies 21a and 21b do not output simultaneously. That is, in the voltage waveforms of the power supplies 21a and 21b, for example, as shown in FIG. 7, rectangular AC voltages are generated intermittently at a predetermined cycle, and the generation timing is such that the power supply 21a generates the AC voltage. During this period, the power supply 21b stops generating the AC voltage. Conversely, while the power supply 21a stops generating the AC voltage, the power supply 21b generates the AC voltage. As described above, the voltage waveforms of the power supplies 21a and 21b are different from each other in the phase of their complete generation.
[0026]
The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the size and shape of the fluorescent lamp, the rectangular wave voltage to be applied, the shape and material and arrangement of the internal electrodes, and the shape, material and arrangement of the external electrodes and the like may be appropriately selected according to the use condition.
[0027]
【The invention's effect】
According to the present invention, a long discharge space is shared by a discharge between one internal electrode and an external electrode and a discharge between the other internal electrode and an external electrode, and the required diffusion is periodically and alternately performed. By adopting a configuration for generating a positive column, visually uniform light emission can be obtained over the entire length. That is, the emission length assigned to one internal electrode is set to be short. Therefore, uniform emission of a long lamp can be ensured at a low voltage, and a tube current (consumption current) flowing to one internal electrode can be reduced. ), Suppression of consumption of the internal electrode during lighting (extension of life), reduction of the temperature of the tube wall near the internal electrode, and the like are achieved. That is, it is possible to provide a backlight mechanism that can sufficiently cope with an increase in the size of a liquid crystal display device (display panel) and that can display a high-quality image.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views schematically showing a schematic configuration and operation of a fluorescent lamp lighting method according to a first embodiment.
FIG. 2 is a characteristic diagram showing a luminance distribution in a lamp length direction by the fluorescent lamp lighting means according to the first embodiment.
FIGS. 3A, 3B, and 3C are timing charts showing modified examples of a rectangular wave voltage periodically applied to an internal electrode in the fluorescent lamp lighting means according to the first embodiment.
FIG. 4 is a characteristic diagram showing the relationship between the power supply voltage and the lamp length in the fluorescent lamp lighting means according to the first embodiment, in comparison with the case of a conventional lighting means.
FIG. 5 is a characteristic diagram showing the relationship between the current flowing through one internal electrode and the lamp length in the fluorescent lamp lighting means according to the first embodiment, in comparison with the case of a conventional lighting means.
FIGS. 6A and 6B are cross-sectional views schematically showing a schematic configuration and operation of a fluorescent lamp lighting method according to a second embodiment.
FIG. 7 is a timing chart showing a modification of the rectangular wave voltage periodically applied to the internal electrodes in the fluorescent lamp lighting means according to the second embodiment.
FIG. 8 is a sectional view showing a schematic configuration of a conventional fluorescent lamp lighting means.
FIG. 9 is a cross-sectional view schematically showing a state in which a diffused positive column is generated in a conventional fluorescent lamp lighting means.
FIG. 10 is a characteristic diagram showing a luminance distribution in a lamp length direction by a conventional fluorescent lamp lighting means.
[Explanation of symbols]
15 phosphor coating 16 glass tubes 17a, 17b internal electrode lead terminals 18a, 18b internal electrode 19 external electrode 19a external electrode lead terminals 20a, 20b, 20c voltage supply line 21 Power supply 22 Changeover switch element

Claims (6)

A glass tube in which a phosphor film is formed on an inner wall surface and a discharge medium containing at least a rare gas is sealed, a pair of internal electrodes that are led out and sealed at both ends of the glass tube, and the glass A method of lighting a fluorescent lamp having an external electrode formed on the outer peripheral surface of the tube by applying an AC voltage,
A method for lighting a fluorescent lamp, comprising: connecting one output terminal of the power supply for generating an AC voltage to an external electrode, and connecting the other output terminal of the power supply to a pair of internal electrodes at a predetermined cycle. 2. The fluorescent lamp lighting method according to claim 1, wherein the predetermined switching cycle is the same as the cycle of the AC voltage or a cycle that is an integral multiple thereof. A glass tube in which a phosphor film is formed on an inner wall surface and a discharge medium containing at least a rare gas is sealed, a pair of internal electrodes that are led out and sealed at both ends of the glass tube, and the glass A fluorescent lamp having an external electrode formed on the outer peripheral surface of the tube,
An AC power supply that generates an AC voltage applied to a pair of internal electrodes and an external electrode of the fluorescent lamp;
A switching unit that alternately applies an AC voltage generated by the AC power supply at a predetermined cycle between one of the pair of internal electrodes and the external electrode, and between the other of the pair of internal electrodes and the external electrode,
A lighting device for a fluorescent lamp, comprising: 4. The fluorescent lamp lighting device according to claim 3, wherein the predetermined switching cycle is the same as the cycle of the AC voltage or a cycle that is an integral multiple thereof. A glass tube in which a phosphor film is formed on an inner wall surface and a discharge medium containing at least a rare gas is sealed, a pair of internal electrodes that are led out and sealed at both ends of the glass tube, and the glass A fluorescent lamp having an external electrode formed on the outer peripheral surface of the tube,
A first AC power supply that applies an AC voltage intermittently at a predetermined cycle between one internal electrode and the external electrode of the fluorescent lamp;
A second AC power supply that applies an AC voltage intermittently at a predetermined cycle between the other internal electrode and the external electrode of the fluorescent lamp,
The lighting device for a fluorescent lamp, wherein the first AC power supply and the second AC power supply have different phases of the intermittent AC voltage generation. The fluorescent lamp lighting device according to claim 5, wherein the second AC power supply stops generating the AC voltage during a period in which the AC voltage is supplied from the first AC power supply.

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