JP2007227028A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system capable of performing reliable starting and driving of dielectric barrier discharge lamps as light sources even at low temperatures. <P>SOLUTION: In a lighting system 101 including a plurality of dielectric barrier discharge lamps 1 as a light source housed in a housing 11 and an inverter circuit 10 supplying electric power to the plurality of dielectric barrier discharge lamps, the lighting system further includes an installation space 14 for the plurality of dielectric barrier discharge lamps in the housing, a temperature detecting means 13 for detecting atmosphere temperature of the coldest part in the installation space, and feedback control means 26 and 24 feeding back a temperature detection signal from the temperature detecting means to control the lighting operation of the plurality of dielectric barrier discharge lamps. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination device that is optimal as a backlight unit for a liquid crystal display.

  6 and 7 show a general dielectric barrier discharge lamp (EEFL: External Electrode Fluorescent Lamp) 1. In this dielectric barrier discharge lamp 1, a discharge gas 3, which is a mixed gas of mercury and a rare gas such as neon, argon, xenon, etc., is enclosed in a glass tube 2, and a phosphor layer 4 is formed on the inner wall surface of the glass tube 2. Is formed, both ends of the glass tube 2 are sealed, and a metal conductor layer is attached to the outer surface of both ends of the glass tube 2 to form the external electrode 5. Such a dielectric barrier discharge lamp 1 connects the output of the inverter circuit 9 as a high-frequency lighting device between the external electrodes 5 and 5 at both ends of the glass tube 2 and applies a high-frequency voltage to the external electrodes 5 and 5. High frequency power is injected into the glass tube 2 through the C component of the inner glass tube 2, and a continuous discharge is generated in the glass tube 2 so that the lamp emits light.

  Since the dielectric barrier discharge lamp 1 is a capacitively coupled discharge lamp, it has a feature that it is easy to light in parallel. Therefore, when designing a direct type backlight unit, the use of the dielectric barrier discharge lamp 1 as a light source can reduce the cost.

  FIG. 8 shows a backlight unit 100 in which a plurality of the dielectric barrier discharge lamps 1 are incorporated as light sources in parallel. In this backlight unit 100, common power supply members 12, 12 are arranged on both the left and right sides in the housing 11, and a required number of dielectric barrier discharge lamps 1 are connected in parallel to the power supply members 12, 12. The same high frequency voltage is applied to the external electrodes 5 and 5 of the respective dielectric barrier discharge lamps 1 by the inverter circuit 9 to light them. In each dielectric barrier discharge lamp 1, the thickness of the glass portion inside the external electrode 5 functions as a ballast capacitor, and if the length of the external electrode 5 of each lamp 1 is the same, each lamp 1 has almost the same thickness. A common lamp current flows.

  Conventionally, in the backlight unit 100 using such a dielectric barrier discharge lamp 1, it is general that the ballast portion of the inverter circuit 9 does not include a load such as a capacitor as a ballast.

  In this lighting method, the lamp load increases in a low temperature environment, so that a phenomenon that does not reach the stable discharge voltage may occur during start-up. FIG. 9 shows the temperature characteristics of a dielectric barrier discharge lamp for a 32-inch backlight unit. In the case of a 5 mA lighting drive design at 25 ° C., the starting voltage Es needs 1700 Vrms, but for 5 mA lighting driving, a voltage of 2000 Vrms is applied and the lamp normally lights up. However, when the ambient temperature is low (for example, when the ambient temperature is 0 ° C.), 2100 Vrms is necessary as the starting voltage Es, and normal lighting does not occur unless an applied voltage of 2100 Vrms or more of 6 mA drive is applied. That is, it becomes difficult to drive the lighting at a current lower than 6 mA.

  As described above, in a lighting device such as a backlight unit using a dielectric barrier discharge lamp as a light source, in order to be able to start stably even in an environment where the ambient temperature is lowered, it is higher than the starting voltage at room temperature. Conventionally, a boost driving technique in which a high voltage is applied for a certain period of time when starting lighting is known.

However, with the conventional boost drive technology, a high voltage is applied for a certain period of time when lighting is started. When the voltage is canceled and the applied voltage is reduced to the normal lighting voltage, the applied voltage becomes lower than the stable discharge voltage of the dielectric barrier discharge lamp, and there is a problem that the normal lighting may not be performed.
JP 2000-58285 A

  The present invention has been made in view of such a conventional technical problem, and an object of the present invention is to provide an illumination device that can reliably start and drive a dielectric barrier discharge lamp as a light source even in a low temperature environment. And

  According to a first aspect of the present invention, a plurality of dielectric barrier discharge lamps each including a glass tube having a current conductor layer disposed as an external electrode on an outer surface are accommodated in a housing as a light source, and the plurality of dielectric barrier discharges are accommodated. In an illuminating device including an inverter circuit for supplying power to a lamp, temperature detecting means for detecting an ambient temperature installed at a coldest place in an installation space of the plurality of dielectric barrier discharge lamps of the housing, and Feedback control means for controlling the lighting behavior of the plurality of dielectric barrier discharge lamps by feeding back the temperature detection signal of the temperature detection means to the inverter circuit is provided.

  According to a second aspect of the present invention, in the lighting device of the first aspect, the feedback control means corresponds to the temperature of the coldest location in the installation space of the dielectric barrier discharge lamp based on the temperature detection signal at the time of starting the lamp. The inverter circuit is controlled to apply a lamp starting voltage to the plurality of dielectric barrier discharge lamps.

  According to a third aspect of the present invention, in the illumination device according to the first aspect, the feedback control means corresponds to the temperature of the coldest place in the installation space of the dielectric barrier discharge lamp based on the temperature detection signal during lamp lighting. The inverter circuit is controlled to apply a lamp discharge sustaining voltage to the plurality of dielectric barrier discharge lamps.

  According to the lighting device of the present invention, the temperature of the coldest spot in the lamp installation space of the housing is detected and fed back to the inverter circuit, so that a sufficiently necessary starting voltage can be applied to the dielectric barrier discharge lamp even in a low temperature environment. The dielectric barrier discharge lamp can be lit stably by being applied.

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

  (First Embodiment) FIG. 1 shows a backlight unit 101 as an illumination device according to one embodiment of the present invention. In the backlight unit 101 of the present embodiment, common power supply members 12 and 12 are arranged on both the left and right sides in the housing 11 as in the conventional example shown in FIG. 8, and the configuration shown in FIGS. The required number of dielectric barrier discharge lamps 1 are connected in parallel to the power supply members 12 and 12, and a high frequency voltage is applied to the external electrodes 5 and 5 of each dielectric barrier discharge lamp 1 by the inverter circuit 10. To light up.

  As a feature of the present embodiment, a temperature detection element 13 such as a thermistor or a thermocouple as the temperature detection element 13 is a normal cold place in the lamp installation space 14 in the casing 11 of the backlight unit 101. It is installed near the center of the lowermost row of lamps when it is used upright, and the ambient temperature at that location is detected. The temperature detection signal of the temperature detection element 13 is fed back to the control circuit in the inverter circuit 10.

  The inverter circuit 10 performs feedback control of the lamp power and has the circuit configuration of FIG. The inverter circuit 10 includes a DC power source 21, a switching element (SW) 22 that switches the DC power source 21 to generate high-frequency alternating current, and a plurality of dielectric barrier discharge lamps connected in parallel as a load by boosting the high-frequency alternating current. 1 is provided with a transformer 23 that supplies power to 1, an IC 24 that controls the switching operation of the switching element 22, and a rectifier circuit 25 that rectifies the current value from the dielectric barrier discharge lamp 1.

  In this inverter circuit 10, the current value from the dielectric barrier discharge lamp 1 as a load is rectified by the rectifier circuit 25 and a voltage command is input to the IC 24, so that the IC 24 corresponds to the voltage command and the switching element 22. The high-frequency alternating current of the switching element 22 is boosted by the transformer 23 and supplied to the dielectric barrier discharge lamp 1. Further, the inverter circuit 10 feeds back a current commensurate with the detected temperature generated by the temperature detecting element 13 through the control circuit 26 and merges it with a normal feedback current, thereby raising the voltage command to the IC 24 and thereby the transformer. A corresponding voltage is applied from 23 to the dielectric barrier discharge lamp 1.

  The lamp application voltage corresponding to the temperature condition generated by the control of the IC 24 is that shown in FIG. The applied voltage shown in FIG. 3 is continuously changed according to the temperature of the coldest spot in the lamp installation space detected by the temperature detection element 13. On the other hand, the voltage command shown in FIG. 4 is a constant high voltage when the temperature of the coldest spot detected by the temperature detecting element 13 is lower than a preset constant temperature.

  In a long dielectric barrier discharge lamp, in recent years, in order to increase the efficiency of the lamp and reduce the applied voltage, the electrode is elongated to reduce the load on the electrode portion. As a result, the load on the electrode portion is smaller than the load on the positive column portion of the dielectric barrier discharge lamp 1, so that starting in a low temperature environment is severe. However, like the backlight unit 101 of the present embodiment, the temperature of the coldest spot in the lamp installation space 14 is measured, and a high voltage that can be reliably started even under the measured temperature condition can be applied to the dielectric barrier discharge lamp 1. Further, by controlling the inverter circuit 10, stable lighting can be reliably performed even in a low temperature environment.

  (Second Embodiment) A backlight unit 101 as an illuminating device according to a second embodiment of the present invention has the configuration shown in FIG. 1 as in the first embodiment. However, the inverter circuit 10 'differs from the first embodiment in that it has the circuit configuration of FIG.

  Similarly to the inverter circuit 10 of the first embodiment, the inverter circuit 10 ′ in the present embodiment also performs feedback control of the lamp power, and a DC power supply 21 and a switching element that switches this to generate high-frequency AC (SW) 22, a transformer 23 that boosts the high-frequency alternating current and supplies power to a plurality of dielectric barrier discharge lamps 1 connected in parallel as a load, an IC 24 that controls the switching operation of the switching element 22, and a dielectric barrier discharge A rectifier circuit 25 that rectifies the current value from the lamp 1 is provided.

  In the inverter circuit 10 ′ of the present embodiment, the current value from the dielectric barrier discharge lamp 1 as a load is rectified by the rectifier circuit 25 and input to the IC 24, and at the same time, generated by the temperature detection element 13. A current commensurate with the detected temperature is fed back through the control circuit 27, and the IC 24 calculates the voltage command raised by summing the feedback current of the rectifier circuit 25 and the feedback current of the control circuit 27. Thus, the switching element 22 is controlled, and a corresponding voltage is applied from the transformer 23 to the dielectric barrier discharge lamp 1.

  In the inverter circuit 10 ′ in the present embodiment, the lamp applied voltage corresponding to the temperature condition generated by the control of the IC 24 is as shown in FIG. 3 or FIG. 4 as in the inverter circuit 10 in the first embodiment. . As a result, even in the backlight unit of the present embodiment, the temperature of the coldest spot in the lamp installation space 14 is measured, and the inverter is applied so that a high voltage that can be reliably started even under the measured temperature condition can be applied to the dielectric barrier discharge lamp 1. By controlling the circuit 10 ′, stable lighting can be reliably performed even in a low temperature environment.

The top view of the backlight unit of the 1st Embodiment of this invention. The block diagram of the inverter circuit in the backlight unit of the 1st Embodiment of this invention. The graph which shows the correspondence of the temperature condition of the inverter circuit in the backlight unit of the 1st Embodiment of this invention, and a lamp applied voltage. The graph which shows another corresponding | compatible relationship between the temperature conditions of the inverter circuit in the backlight unit of the 1st Embodiment of this invention, and a lamp applied voltage. The block diagram of the inverter circuit in the backlight unit of the 2nd Embodiment of this invention. The front view of a general dielectric barrier discharge lamp. Sectional drawing of a general dielectric barrier discharge lamp. The top view of the conventional backlight unit. The graph which shows the change characteristic with respect to ambient temperature of the applied voltage of a general dielectric barrier discharge lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric barrier discharge lamp 5 External electrode 10, 10 'Inverter circuit 11 Case 12 Feeding member 13 Temperature detection element 14 Lamp installation space 21 Power supply 22 Switching element 23 Transformer 24 IC
25 rectifier circuit 26 control circuit 27 control circuit 101 backlight unit

Claims (3)

A plurality of dielectric barrier discharge lamps each having a glass tube having a current conductor layer arranged as an external electrode on the outer surface, housed in a housing as a light source, and an inverter circuit for supplying power to the plurality of dielectric barrier discharge lamps In the provided lighting device,
Temperature detecting means for detecting an ambient temperature installed at the coldest place in the installation space of the plurality of dielectric barrier discharge lamps of the housing;
An illuminating apparatus comprising feedback control means for controlling a lighting behavior of the plurality of dielectric barrier discharge lamps by feeding back a temperature detection signal of the temperature detection means to the inverter circuit.   The feedback control means applies, to the plurality of dielectric barrier discharge lamps, a lamp starting voltage corresponding to the temperature at the coldest location in the installation space of the dielectric barrier discharge lamp based on the temperature detection signal at the time of starting the lamp. The lighting device according to claim 1, wherein the inverter circuit is controlled to do so. The plurality of dielectric barrier discharge lamps provide a lamp discharge sustaining voltage corresponding to the temperature at the coldest location in the installation space of the dielectric barrier discharge lamp based on the temperature detection signal during lamp operation. The lighting device according to claim 1, wherein the inverter circuit is controlled to be applied to the lighting device.

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