JP2007200680A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device in which a dielectric barrier discharge of an internal-external electrode system, having a separated arrangement of a lamp and an external electrode is used and in which system efficiency is improved, since current leakage from a high-withstanding voltage cable is prevented. <P>SOLUTION: The discharge lamp lighting device is provided with a first lighting circuit 5 for impressing a high-frequency high voltage between an external electrode 1 and an internal electrode 3 and a second lighting circuit 6 for impressing a high-frequency high voltage between the external electrode 1 and an internal electrode 4. The first lighting circuit 5 and the second lighting circuit 6 output a high-frequency high voltage with an approximately same phase and potential and as a result a length of a high-withstanding voltage cable 14 to connect the first lighting circuit 5 with the internal electrode 3 and the length of a high-withstanding voltage cable 20 to connect the second lighting circuit 6 with the internal electrode 4 can be shortened by as much as possible, and thus current leakage from the high-withstanding voltage cables 14, 20 can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device of an external electrode type that is lit by dielectric barrier discharge, and more specifically, a rectangular wave voltage is applied, and lighting is performed by a pulse current that flows when the voltage value of the rectangular wave voltage changes. The present invention relates to a discharge lamp lighting device for lighting a dielectric barrier discharge lamp.

  2. Description of the Related Art In recent years, research on external electrode type rare gas discharge lamps that are lit by dielectric barrier discharge has been actively conducted for backlight applications such as liquid crystal displays. This is based on the reason that the rare gas discharge lamp does not require mercury, and therefore does not cause a decrease in luminous efficiency due to an increase in mercury vapor pressure and is environmentally preferable. In the lighting operation using the dielectric barrier discharge, the dielectric pair layer is charged by applying the drive voltage, and the action of causing the discharge by the high voltage generated when the drive voltage is inverted is used. A wave voltage is used. In addition, the dielectric barrier discharge is characterized in that a plurality of lamps can be lit in parallel with a single lighting circuit because the load characteristics of the lamps are capacitive positive characteristics.

  An example of a discharge lamp lighting device using dielectric barrier discharge is disclosed in Japanese Patent Laid-Open No. 2003-168304. 8A is a plan view showing the configuration of the conventional discharge lamp lighting device, FIG. 8B is a plan view showing the configuration of the back side of the conventional discharge lamp lighting device, and FIG. 8C is the conventional discharge lamp lighting device. It is a longitudinal cross-sectional view in Fig.8 (a).

  8A, 8 </ b> B, and 8 </ b> C, 101 is a reflector, 102 is an external electrode disposed on the reflector 101, and 103 is disposed on the reflector 101 in contact with the external electrode 102. A discharge lamp 104, an internal electrode sealed at one end of the discharge lamp 103, and a lighting circuit 105 for lighting the discharge lamp 103 by applying a high frequency high voltage between the external electrode 102 and the internal electrode 104, 106 Is a high voltage electric wire electrically connected to the lighting circuit 105 and the internal electrode 104. The reflector 101 not only reflects the light emitted from the discharge lamp 103, but also has a groove for fitting the discharge lamp 103, and the discharge lamp is fixed thereto with an adhesive, an adhesive tape, or the like. The external electrode 102 is formed on the reflection plate 101 by printing or the like, and is configured to be orthogonal to the tube axis direction of the discharge lamp 103. The external electrode 102 is connected to the low voltage output of the lighting circuit 105 through a lead wire and fixed to the GND potential. The discharge lamp 103 has a light-emitting tube formed of a light-transmitting material (for example, borosilicate glass), and a gas containing Xe as a main component as a discharge gas is sealed in a pressure range of about 2 kPa to 35 kPa. Yes. In addition, phosphors appropriately formulated for RGB are applied to the inner wall of the arc tube so that desired light can be obtained. The internal electrode 104 is formed of a metal such as nickel or niobium, for example, and is connected to the high voltage output of the lighting circuit 105 via a lead wire. The lighting circuit 105 includes an inverter circuit such as a push-pull method or a half-bridge method using a step-up transformer, and converts an input DC voltage into a high-frequency high voltage (for example, 20 kHz 3 kVp-p) rectangular wave voltage.

  The operation of the conventional discharge lamp lighting device as described above will be described. When a power source (not shown) is turned on, a high frequency high voltage having a rectangular waveform is generated from the lighting circuit 105. A high frequency high voltage applied between the external electrode 102 and the internal electrode 104 generates a discharge in the arc tube. When the discharge starts, Xe, which is a discharge gas, generates ultraviolet light of 172 nm by excimer emission. The generated ultraviolet light is converted into visible light by the phosphor on the inner wall of the arc tube. Visible light from the discharge lamp 103 is reflected by the reflecting plate 101, becomes a uniform surface light source through a diffuser plate, a lens sheet or the like (not shown), and is used as a backlight.

  In the discharge lamp lighting device using the internal-external electrode type dielectric barrier discharge as described above, it is known that the lamp voltage depends on the lamp length. This is because it is necessary to generate a stronger electric field in order to generate plasma even at a position away from the internal electrode. Since an increase in lamp voltage contributes to a decrease in system efficiency due to leakage current, the configuration in which the internal electrode 104 is disposed at one end of the discharge lamp 103 shown in FIG. 8 is usually a small liquid crystal display (for example, 10 Used for car navigation of inches or less.

Further, in recent years, large-sized liquid crystal TVs of about 15 inches to large-sized liquid crystal TVs of about 15 inches have been put into practical use. In order to cope with the increase in the screen size in this way, as shown in FIGS. Thus, the internal electrodes 104 are disposed at both ends of the discharge lamp 103. As a result, an increase in lamp voltage due to an increase in lamp length can be suppressed by about 10 to 40% compared to when the internal electrode 104 is disposed on one side of the discharge lamp 103.
JP 2003-168304 A

  In general, a leakage current from a high-voltage electric wire 106 that connects the lighting circuit 105 and the discharge lamp 103 is known as one factor of a decrease in system efficiency. That is, a part of the electric power output from the lighting circuit 105 is not transmitted to the discharge lamp 103 but is lost as heat through another path, so that the light output is reduced.

  As a countermeasure against a decrease in system efficiency due to leakage current, when the internal electrode 104 is arranged on one side of the discharge lamp 103 as shown in FIG. 8, the lighting circuit 105 is arranged as close as possible to the internal electrode 104 to shorten the high-breakdown-voltage electric wire 106. This can be done to some extent. Further, when the internal electrodes 104 are arranged at both ends of the discharge lamp 103 as shown in FIG. 9, the high withstand voltage electric wire 106 having a length corresponding to at least the lamp length is required, and the leakage current tends to increase. In the configuration in which the external electrodes 102 are in contact with each other, the lamp voltage is still relatively low, and the leakage current can be almost neglected by measures such as devising the wiring location of the high voltage wire 106 and increasing the high voltage wire 106. Can take measures.

  By the way, a discharge lamp using Xe excimer light emission still has a lower light emission efficiency than a discharge lamp using mercury. The inventors of the present application have made efforts to improve the luminous efficiency, and in the discharge lamp lighting device using the internal-external electrode type dielectric barrier discharge, the issuance efficiency is improved by increasing the distance between the discharge lamp 103 and the external electrode 102. I know that

  However, when the distance between the discharge lamp 103 and the external electrode 102 is increased, the lamp voltage increases. This is because the lamp impedance increases because the distance is increased. As described above, an increase in lamp voltage causes a decrease in system efficiency due to an increase in leakage current, and countermeasures are necessary. However, an increase in lamp voltage due to the increase in the distance between the discharge lamp 103 and the external electrode 102 is caused by discharge. This is much larger than the increase in lamp voltage due to the length of the lamp 103, and it has already been impossible to cope with it by devising the wiring location of the high withstand voltage electric wire 106 or increasing the withstand voltage of the high withstand voltage electric wire 106.

  The present invention has been made in view of such circumstances. In a discharge lamp lighting device using an internal-external electrode type dielectric barrier discharge in which a lamp and an external electrode are spaced apart from each other, An object of the present invention is to provide a discharge lamp lighting device that suppresses leakage current and improves system efficiency.

  A discharge lamp lighting device according to a first aspect of the present invention includes a reflector, a plurality of external electrodes disposed on the reflector or integrally formed with the reflector, and a plurality of internal electrodes at both ends disposed away from the external electrode. A high frequency high voltage is applied between the first lighting circuit for applying a high frequency high voltage between the discharge lamp, the external electrode and one of the pair of internal electrodes, and the other of the external electrode and the pair of internal electrodes. And a second lighting circuit, wherein the first lighting circuit and the second lighting circuit output a high-frequency high voltage having substantially the same phase and substantially the same potential to light a plurality of discharge lamps.

  In the first invention, since the high-voltage wiring connecting one of the internal electrodes and the first lighting circuit and the high-voltage wiring connecting the other of the internal electrodes and the second lighting circuit can be shortened, the leakage current is suppressed. System efficiency can be improved.

  A discharge lamp lighting device according to a second invention is characterized in that, in the first invention, a rare gas containing at least Xe is enclosed as a discharge gas.

  In the second invention, when the discharge gas is Xe, the ionization and excitation efficiency during discharge is excellent, and a light source with high brightness and high efficiency can be obtained.

  A discharge lamp lighting device according to a third aspect of the present invention is characterized in that, in any one of the first and second aspects, the high frequency high voltage has a substantially rectangular waveform.

  In the third aspect of the invention, since the high frequency high voltage has a substantially rectangular waveform, the discharge gas can be efficiently ionized and excited, and a light source with high brightness and high efficiency can be obtained.

  A discharge lamp lighting device according to a fourth invention is characterized in that, in any of the first to third inventions, at least the first lighting circuit and the second lighting circuit share at least a drive system circuit.

  In the fourth aspect of the invention, by sharing the drive system circuit, the configuration of either the first or second lighting circuit can be simplified and the cost can be reduced.

  According to the present invention, in a discharge lamp lighting device using an internal-external electrode type dielectric barrier discharge in which a lamp and an external electrode are spaced apart from each other, leakage current from a high-voltage wiring portion can be suppressed, and various uses can be achieved. It has excellent effects such as being able to be used as a light source.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

(Embodiment 1)
FIG. 1A is a plan view showing the configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention, and FIG. 1B is the configuration of the back side of the discharge lamp lighting device according to Embodiment 1 of the present invention. FIG.1 (c) is a longitudinal cross-sectional view in Fig.1 (a) of the discharge lamp lighting device which concerns on Embodiment 1 of this invention.

  The discharge lamp lighting device according to Embodiment 1 of the present invention includes an external electrode 1, a discharge lamp 2, a pair of internal electrodes 3, 4, a first lighting circuit 5, a second lighting circuit 6, a high And withstand voltage wires 14 and 20.

  The external electrode 1 has a structure in which the reflection plate and the external electrode are integrally molded as provided with the function of the reflection plate. The external electrode 1 is made of a conductive metal material. For example, if a metal material with aluminum deposited on its surface is used as a base material, an external electrode having a function of a reflector can be easily formed by pressing. can do.

  An example of the configuration of the discharge lamp 2 is shown in FIG. As shown in FIG. 2, the discharge lamp 2 has a cylindrical arc tube 7 made of borosilicate glass, soda glass or the like having excellent transmittance in visible light (380 nm to 770 nm) and xenon as a discharge gas. A mixed gas as a main component is enclosed, and the enclosure pressure is, for example, 20 kPa. As mixed gas components other than xenon, helium, neon, argon, krypton, etc. are mixed at a mixing ratio of 6: 4, for example. A phosphor 8 is applied to the inner surface of the arc tube 7. Internal electrodes 3 and 4 made of metal such as nickel and niobium are disposed at both ends of the arc tube 7 and are electrically led out of the arc tube 7 by lead wires. As shown in FIG. 1, the discharge lamp 2 is disposed apart from the external electrode 1, and the distance between the discharge lamp 2 and the external electrode 1 is fixed to, for example, 3 mm by a spacer (not shown). The spacer is made of a white or transparent resin.

  An example of the configuration of the first lighting circuit 5 and the second lighting circuit 2 is shown in FIG. In FIG. 3, 1 is an external electrode, 2 is a discharge lamp, 3 and 4 are internal electrodes, 5 and 6 are a first lighting circuit and a second lighting circuit, and 14 and 20 are high-voltage electric wires. Although four discharge lamps 2 are shown in FIG. 1, only one simple lamp is shown here.

  Since the external electrode 1, the discharge lamp 2, and the internal electrodes 3, 4 are the same as described above, the details are omitted.

  Each of the first lighting circuit 5 and the second lighting circuit 6 is a push-pull inverter circuit. Each of the first lighting circuit 5 and the second lighting circuit 6 includes DC power supplies 9 and 15, drive circuits 10 and 16, FETs 11, 12, 17 and 18 which are switching elements, and step-up transformers 13 and 19. The DC power supply 9 and FETs 11 and 12 are connected to the primary winding of the step-up transformer 13, and the DC power supply 15 and FETs 17 and 18 are connected to the primary winding of the step-up transformer 19. The drive circuit 10 outputs a gate signal to the FETs 11 and 12, and alternately turns the FETs 11 and 12 on and off. The drive circuit 16 outputs a gate signal to the FETs 17 and 18, and turns the FETs 17 and 18 on and off alternately. The drive circuits 10 and 16 operate in synchronization with each other so that there is no phase difference between the output voltage of the first lighting circuit 5 and the output voltage of the second lighting circuit 6, and the frequency of the gate signal to be output. The duty and the like are substantially constant, and the FETs 11 and 17 are operated to be ON, the FETs 12 and 18 are OFF, and the FETs 11 and 17 are OFF and the FETs 12 and 18 are ON. The drive circuits 10 and 16 can be easily configured with a commercially available IC or the like, and there are some built-in functions of the IC with respect to the synchronous operation. The step-up transformers 13 and 19 convert the DC voltage from the DC power sources 9 and 15 into a high frequency high voltage having a rectangular waveform. The frequency at this time depends on the frequency of the output signals of the drive circuits 10 and 16, and is 20 kHz, for example. The step-up ratio depends on the turn ratio of the primary winding and the secondary winding of the step-up transformers 13 and 19, and for example, DC 24V is converted into a 6 kVp-p rectangular wave voltage. At this time, the output voltages of the step-up transformers 13 and 19 do not necessarily have an ideal rectangular waveform, and include some ringing due to the influence of the leakage inductance, parasitic capacitance, and the like of the step-up transformer. The 6 kVp-p indicates the value of peak to peak including ringing. The output voltages of the step-up transformers 13 and 19 (that is, the output voltages of the first lighting circuit 5 and the second lighting circuit) have substantially the same phase and substantially the same potential. When the output voltage of the step-up transformer 13 and the output voltage of the step-up transformer 19 have different phases and different potentials, discharge occurs between the internal electrode 3 and the internal electrode 4, and the luminous efficiency of the discharge lamp 2 decreases. To do. In other words, the output voltages of the step-up transformer 13 and the step-up transformer 19 may not be substantially in phase and substantially the same potential as long as no discharge is generated between the internal electrode 3 and the internal electrode 4. , The design becomes complicated. One end of the secondary winding of the step-up transformer 13 is connected to the internal electrode 3 via the high-voltage wire 14, and the other end is connected to the external electrode 1 and to GND. One end of the secondary winding of the step-up transformer 19 is connected to the internal electrode 4 through the high-voltage wire 20, and the other end is connected to the external electrode 1 and to GND. Since the voltage is low, the connection between the other end of the secondary winding of the step-up transformers 13 and 19 and the external electrode and GND does not have to be a high-voltage electric wire. The 1st lighting circuit 5 and the 2nd lighting circuit 6 are arrange | positioned in the immediate vicinity of the internal electrodes 3 and 4 so that the high voltage | pressure-resistant electric wires 14 and 20 may become as short as possible (refer FIG. 1).

  In the above configuration, when a rectangular wave high frequency high voltage is applied between the internal electrodes 3 and 4 of the discharge lamp 2 and the external electrode 1, the voltage value of the rectangular wave high frequency high voltage changes, that is, the polarity is inverted. When this occurs, a pulse current flows between the internal electrode 3 and the external electrode 1 and between the internal electrode 4 and the external electrode 1, and a dielectric barrier discharge is generated in the discharge lamp 2. At this time, the gap between the arc tube 7, the discharge lamp 2, and the external electrode 1 acts as a dielectric. When the dielectric barrier discharge starts, xenon sealed in the arc tube 7 is excited by electrons and emits ultraviolet rays. The ultraviolet rays are converted into visible light by the phosphor 8 applied to the inner wall of the arc tube 7, and the discharge lamp 2 is lit. In general, in a lighting operation using a dielectric barrier discharge, by lighting with a rectangular wave voltage rather than a sine wave voltage, the excimer emission of xenon increases and a lot of ultraviolet rays are emitted, so that the light emission efficiency is improved.

  Since the high-voltage high voltage is applied to the high-voltage wires 14 and 20 while the discharge lamp 2 is lit, the external electrode 1 and other metal members (for example, a housing of a liquid crystal TV) are disposed through the coating of the high-voltage wires 14 and 20. Leakage current flowing toward the body, etc.) occurs, but leakage from the high-voltage electric wires 14 and 20 by arranging the first lighting circuit 5 and the second lighting circuit 6 in the immediate vicinity of the internal electrodes 3 and 4 The current can be suppressed to a minimum, and a decrease in system efficiency of the discharge lamp lighting device can be suppressed.

(Embodiment 2)
FIG. 4 is a diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention. The second embodiment is different from the first embodiment in that the drive circuit 23 is shared by the first lighting circuit 21 and the second lighting circuit 22, and the rest is the same as the first embodiment. The same reference numerals are given to the same components, and detailed description is omitted. By sharing the drive circuit 23, the first lighting circuit 21 and the second lighting circuit 22 that mainly use a high frequency high voltage of a rectangular wave having substantially the same phase and substantially the same potential can be configured more easily. The 1st lighting circuit 21 and the 2nd lighting circuit 22 are arrange | positioned in the immediate vicinity of the internal electrodes 3 and 4, respectively, and the high voltage | pressure-resistant electric wires 14 and 20 are shortened as much as possible.

  With the above configuration, it is possible to suppress the leakage current from the high-voltage electric wires 14 and 20 and to suppress a reduction in system efficiency of the discharge lamp lighting device, and it is possible to greatly reduce the overall cost of the discharge lamp lighting device. The first lighting circuit 21 has the same configuration as the lighting circuit 5 in FIG. 3, but the configuration of the second lighting circuit 22 is simplified. In this configuration, a wiring for transmitting a gate signal is required between the first lighting circuit 21 and the second lighting circuit 22, but the gate signal is usually a low voltage of about 5 to 15V. The leakage current from this wiring hardly occurs, and the system efficiency is not affected.

  Further, in addition to the configuration of FIG. 4, the configuration shown in FIG. The first lighting circuit 24 has the same configuration as the first lighting circuit 5 in FIG. 3 and the first lighting circuit 21 in FIG. 4, but the configuration of the second lighting circuit 25 is further simplified. Thereby, the overall cost of the discharge lamp lighting device can be further reduced. However, in this case, a wiring through which a high-frequency large current flows is required between the first lighting circuit 24 and the second lighting circuit 25, and leakage current from the wiring hardly occurs because the voltage is low. The generation of unnecessary radiation noise due to a large current is considered, and it is necessary to consider the wiring location.

  The external electrode 1 has a planar configuration, but is not limited to this configuration, and may have a waveform cross-sectional shape as shown in FIG. Moreover, the material should just have electroconductivity. However, if it is formed integrally with the reflector, it must be made of a material having high reflectivity and conductivity. Further, as shown in FIG. 7, a configuration in which the external electrode 30 is disposed on the reflection plate 29 may be employed. The reflector 29 can be made of, for example, white resin, and the external electrode 30 can be made of, for example, copper, aluminum, or the like. Further, the reflector 29 may have a corrugated cross section as in FIG. Further, although the external electrode 30 is configured in a stripe shape, other shapes may be used.

  Further, the discharge lamp 2 has an enclosed gas pressure of 20 kPa, but other gas pressures may be used as long as it is in the range of about 5 to 35 kPa. Further, the example in which the four discharge lamps 2 are lit in parallel has been described, but other numbers may be used, and the number of lamps depends on the size of the liquid crystal display. For example, when the size is 32 inches, the number of lamps is about 16 to 20 Necessary. Further, although the distance between the discharge lamp 2 and the external electrode 1 is 3 mm, the distance is not limited to this, and may be in the range of about 1 to 20 mm. When the lamp length is 250 mm or more, the leakage current suppressing effect is particularly remarkable.

  Moreover, although the internal electrodes 3 and 4 are shown in a cup shape, they may be in a rod shape.

  Moreover, although the first lighting circuits 5, 21, 24 and the second lighting circuits 6, 22, 25 are of the push-pull method, other methods such as a half-bridge method and a full-bridge method may be used. Further, the DC power supplies 9 and 15 may be constituted by a chopper circuit or the like. The FETs 11, 12, 17, 18, 26, and 27 may use bipolar transistors, IGBTs, or the like instead. Moreover, although the drive frequency was 20 kHz, other frequencies may be used, and it may be about 5 to 30 kHz from the viewpoint of light emission efficiency. Further, although the output voltage of the step-up transformers 13 and 19 is 6 kVp-p, this value varies depending on design factors such as the length of the discharge lamp 2 and gas pressure, and may be other values depending on the discharge lamp. Needless to say.

  As described above, according to the present invention, in the discharge lamp lighting device using the internal-external electrode type dielectric barrier discharge in which the discharge lamp and the external electrode are arranged apart from each other, one of the external electrode and the pair of internal electrodes A first lighting circuit for applying a high-frequency high voltage between the first electrode and a second lighting circuit for applying a high-frequency high voltage between the external electrode and the other of the pair of internal electrodes. And the second lighting circuit can output the high-voltage high voltage with substantially the same phase and substantially the same potential, so that the high-voltage electric wire connecting the first lighting circuit and the second lighting circuit and the internal electrode can be shortened as much as possible. Leakage current from the high-voltage electric wire can be suppressed, and the system efficiency of the discharge lamp lighting device can be improved. Thereby, the discharge lamp lighting device according to the present invention is useful for a light source for backlight such as a liquid crystal display, a copier, a scanner, and the like.

The block diagram which shows an example of the discharge lamp lighting device which concerns on Embodiment 1 of this invention The block diagram which shows an example of the discharge lamp which concerns on Embodiment 1 of this invention 1 is a circuit diagram showing an example of first and second lighting circuits according to Embodiment 1 of the present invention. The circuit diagram which shows an example of the 1st and 2nd lighting circuit which concerns on Embodiment 2 of this invention The circuit diagram which shows another example of the 1st and 2nd lighting circuit which concerns on Embodiment 2 of this invention Configuration diagram showing another example of configuration of external electrode Configuration diagram showing another example of configuration of reflector and external electrode The block diagram which shows the structure of the conventional discharge lamp lighting device The block diagram which shows another example of a structure of the conventional discharge lamp lighting device

Explanation of symbols

1,28,30,102 External electrode 2,103 Discharge lamp 3,4,104 Internal electrode 5,21,24 First lighting circuit 6,22,25 Second lighting circuit 7 Arc tube 8 Phosphor 9,15 DC power supply 10, 16, 23 Drive circuit 11, 12, 17, 18, 26, 27 FET
13, 19 Step-up transformer 14, 20, 106 High voltage electric wire 29, 101 Reflector 105 Lighting circuit

Claims (4)

A plurality of discharge lamps having a reflection plate, an external electrode disposed on the reflection plate or integrally formed with the reflection plate, a pair of internal electrodes at both ends disposed away from the external electrode, and the external electrode A first lighting circuit that applies a high-frequency high voltage between the external electrode and one of the pair of internal electrodes, and a second lighting that applies a high-frequency high voltage between the external electrode and the other of the pair of internal electrodes A discharge lamp lighting device, wherein the first lighting circuit and the second lighting circuit output a high-frequency high voltage having substantially the same phase and substantially the same potential to light the plurality of discharge lamps. . The discharge lamp lighting device according to claim 1, wherein the plurality of discharge lamps are filled with a rare gas containing at least Xe as a discharge gas. The discharge lamp lighting device according to claim 1, wherein the high-frequency high voltage has a substantially rectangular waveform. 4. The discharge lamp lighting device according to claim 1, wherein at least a driving system circuit is shared by the first lighting circuit and the second lighting circuit. 5.

Images