JP3513590B2 - External electrode fluorescent lamp lighting method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting system for lighting an external electrode type fluorescent discharge lamp used as a back light source of a liquid crystal display device used for a personal computer, a word processor or the like. About. [0002] There are a sine wave lighting method and a pulse lighting method as a discharge lamp lighting method using a DC power supply as an input. As a sine wave lighting method, for example, JP-A-4-370696,
JP-B-5-62440, JP-A-5-137343
JP, JP-A-6-310287, JP-A-7-2702
As disclosed in Japanese Patent No. 72879, an inverter circuit is provided to make an alternating current and perform sine wave lighting. [0003] As a pulse lighting method, for example,
As shown in JP-A-61792 and JP-A-5-166589, a discharge lamp is provided on the secondary side of a pulse transformer.
A pulse voltage generated on the secondary side is applied to a discharge lamp; Japanese Patent No. 2691430;
78099, a configuration in which a pulse generating circuit and a discharge lamp are connected in parallel,
As disclosed in Japanese Patent No. 2386, a closed circuit is constituted by a switch or a pulse power supply that is controlled to open and close by a program, a discharge lamp and a DC power supply, and a DC voltage is changed by changing an energizing time, a pause time, and a current intensity. There is a configuration in which the light is shaped into a rectangular wave, and the shaped voltage is applied to a discharge lamp to change the emission color to a desired color by changing the waveform. However, in the case of the sine wave lighting method, there is no current pause period (period in which no current flows), a steep current cannot be supplied, and uneven lighting at low light intensity is not achieved. As a result, high brightness was not obtained, and this was not suitable as a lighting waveform in an external electrode type discharge lamp. The phosphor is excited when a rising current (positive current) and a falling current (negative current) flow, respectively. When a discharge lamp of a unipolar external electrode type is turned on by a conventional pulse inverter, light emission does not spread to the entire bulb at a low tube current, and partial discharge occurs on the internal electrode side.
Unless a tube current of about 0 to 40 mA was passed, light emission did not spread over the entire bulb. In the conventional pulse inverter, the voltage waveform input to the discharge lamp is a single pulse as shown in FIG.
As shown in (b), the current continuously flows positively and negatively, the tube current flows substantially simultaneously in time, and then the quiescent period occurs, and the first positive and negative currents excite the phosphor. This is because it takes time until the next current flows, and the discharge lamp does not perform normal lighting with the light emission spread over the entire bulb unless the tube current is high. Therefore, the power consumption of the discharge lamp becomes high, and the temperature of the bulb wall near the internal electrode, which is the highest, is 2
When the discharge lamp was heated to a high temperature of 00 ° C. or more, there was a problem of heat resistance of the backlight case when the discharge lamp was incorporated in the backlight. [0006] The invention disclosed in Japanese Patent Publication No. 53-42386 has a configuration in which a DC voltage is shaped into a rectangular wave by a switch or a pulse power supply and applied to a discharge lamp. However, it is impossible to increase the voltage. In addition, there is a problem that it is not suitable as a lighting method of a rear light source of a liquid crystal display device which requires a large number of discharge lamps, eliminates flickering, and requires high luminance. The problem to be solved by the present invention is that a so-called discharge lamp inverter device for lighting a discharge lamp used as a back light source of a liquid crystal display device has a stationary period after a current continuously flows positively and negatively. As a result, lighting cannot be performed efficiently, which is inappropriate for a lighting waveform in an external electrode type discharge lamp. An object of the present invention is to provide a circuit capable of generating an optimal rectangular wave high-voltage DC voltage with a fast rise and fall in an external electrode type discharge lamp in a so-called discharge lamp inverter device, so that a rise current and a fall current are substantially reduced. It is an object of the present invention to provide a discharge lamp lighting device that flows at regular intervals so as to operate a fluorescent discharge lamp with higher efficiency than a conventional pulse inverter. According to the first aspect of the present invention , a phosphor film is formed on an inner surface of a glass bulb.
And it was sealed to one end of the glass outer electrode and the glass bulb formed by winding a metal wire spirally on the outer surface of the valve
Lighting method of external electrode type fluorescent discharge lamp with internal electrode
Wherein the repetition frequency between the external electrode and the internal electrode is 10 to 50 KHz, the tube power supplied into the glass bulb is set to be more than 1.0 kW and less than 4.0 kW, and the shock ratio is increased. A rectangular wave pulse voltage set to 50 ± 20% is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on an embodiment of the present invention shown in the drawings. First, the circuit configuration used for the lighting method of the external electrode type fluorescent discharge lamp will be described with reference to the circuit diagram shown in FIG. The discharge lamp lighting device shown in FIG. 1 includes a DC power supply 1, a switching circuit 2 for converting a DC voltage into a rectangular wave, a pulse transformer 3 for converting the output of the switching circuit 2 into a high-voltage pulse voltage, 2
A discharge lamp 4 of a unipolar external electrode type is connected to the secondary side. In this embodiment, as a unipolar external electrode type discharge lamp 4, a phosphor coating 6 is formed on the inner surface of a glass bulb 5 constituting a sealed discharge space as shown in FIGS. An internal electrode 7 is sealed to one end of the glass bulb 5, an external electrode 8 in which a metal wire is spirally wound on the outer surface of the glass bulb 5, and a translucent resin film 9 is wound on the outer surface. Use the formed one. Fig. 2
In addition, the discharge lamp is not limited to the unipolar external electrode type discharge lamp shown in FIG. 3, and a unipolar external electrode type discharge lamp in which at least one electrode is provided on the outer surface of the glass bulb, or both electrodes are glass An external electrode type discharge lamp provided on the outer surface of the bulb is considered. Next, the operation will be described. DC power supply 1
When power is further supplied, a DC voltage is applied to the switching circuit 2. The switching elements constituting the switching circuit 2 perform on / off operations at a high frequency of 10 to 50 kHz, and the switching circuit 2 outputs a rectangular wave voltage shown in FIG. Switching frequency is 10-50
It must be set to kHz and must not exceed 50 kHz. Thus, the switching frequency is between 10 and
The reason for setting the frequency to 50 kHz will be described with reference to FIGS. The discharge lamp 4 uses a positive column, which is a light emitting part in a plasma state in which a potential gradient is positive in discharge and atoms or molecules are actively excited. In the discharge lamp 4, the flicker occurs when a stable lighting area (high luminance area) and a flicker area (low luminance area) occur as shown in FIG. In this case, there are a thick positive column and a thin positive column, and the discharge lamp 4 flickers. According to the graphs shown in FIGS. 6 to 8, when the lamp power is 4.0 W, the flickering region occurs over a distance approximately half the lamp length from the lamp end on the internal electrode 7 side, but the lamp power is 3.0 W. In the case of the internal electrode 7
Exists over a distance of 5 mm from the side lamp end to the other end,
In other words, flicker occurs only around the internal electrode 7,
Further, when the tube power is 2.0 W, the flickering region is completely eliminated, the discharge spreads over the entire lamp, and the discharge lamp 4 is stably lit. For this reason, in order to stably turn on the discharge lamp 4, the power supplied to the discharge lamp 4 needs to be set to less than 4.0W. Further, from FIG. 9 showing a graph of the relationship between the lighting frequency and the tube power, when the discharge lamp 4 is turned on by operating the switching circuit 2 at a switching frequency of 50 kHz or more, the discharge does not spread to the entire lamp, and flickering occurs. An area occurs. According to the experimentally derived numerical values of FIGS. 6 to 9, the switching frequency needs to be set to 50 kHz or less in order to stably light the discharge lamp 4. The timing of the on / off operation of the switching element needs to be operated so that the output waveform of the switching circuit 2 shown in FIG. 4A becomes a rectangular wave having an impact ratio of 30 to 70%. In this method, a current is applied to the discharge lamp 4 at substantially regular intervals, and the impact ratio is set to 50 ± 20% in order to light the discharge lamp 4 with high efficiency. Through the pulse transformer 3, a rectangular wave voltage is generated on the secondary side of the pulse transformer 3 in accordance with the turns ratio with respect to the primary side. 10-5 output to the secondary side
A rectangular wave voltage having a frequency of 0 kHz has a pulse amplitude (Vp−
It is necessary to use a transformer having a leakage inductance of 0.1 to 30% as the pulse transformer 3 so that the rise and fall times until p) becomes 10 to 90% become a rectangular wave of 0.1 to 10 μsec. is there. The primary inductance when the secondary winding of the transformer is short-circuited is measured, and the leakage inductance which is a value obtained by dividing the primary inductance when the secondary winding is opened is 3
When a transformer of 0% or more is used, the rise and fall of the pulse voltage are slow, the voltage waveform is shaped into a shape close to a sine wave, and a steep current cannot flow through the discharge lamp 4 at the time of rise and fall. Light intensity decreases,
In order to perform lighting with low efficiency, a transformer having a low leakage inductance of 0.1 to 30% is used as the pulse transformer 3. By applying a rectangular wave voltage shown in FIG. 4B, which rises and falls quickly, to the discharge lamp 4, positive and negative current pulses shown in FIG. Have and flow. Therefore, in a unipolar external electrode type discharge lamp, highly efficient lighting is performed. Test Example A lighting efficiency test of the rectangular wave inverter according to the present embodiment was performed. The result was as shown by the solid line in FIG. For comparison, a lighting efficiency test using a conventional pulse inverter in which the lamp voltage and the lamp current were set to the waveforms shown in FIGS. 11A and 11B was also performed. The result was as shown by the dotted line in FIG. The rectangular wave inverter according to the present embodiment has an efficiency of about 2.5 times per 1 W as compared with the conventional pulse inverter, and the lighting of the unipolar external electrode type discharge lamp requires the rectangular wave inverter. It turns out that the use is highly efficient. According to the present invention, the switching frequency is set to 10 to 10.
It is set to 50 kHz to stably light the discharge lamp without flickering. Also, the leakage inductance of the pulse transformer is set low to make the rectangular wave voltage applied to the discharge lamp a fast rising and falling waveform.
Since the current is made to flow at regular intervals with a shock rate of 50 ± 20%, unlike conventional pulse inverter lighting, stable lighting with low power consumption, a simple circuit configuration and low cost can be realized. In addition, there is an effect that high luminance can be obtained with a small amount of tube power.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit configuration diagram used for a lighting method of an external electrode type fluorescent discharge lamp. FIG. 2 is a partially cutaway front view showing a discharge lamp. FIG. 3 is a sectional view of a discharge lamp. FIG. 4 is an operation waveform diagram showing the operation of FIG. FIG. 5 is an explanatory diagram showing a state of sunlight when flickering occurs. FIG. 6 is a graph showing the relationship between the distance from the internal electrode side lamp end and the luminance when the tube power is 2.0 W. FIG. 7 is a graph showing the relationship between the distance from the internal electrode side lamp end and the luminance when the tube power is 3.0 W. FIG. 8 is a graph showing the relationship between the distance from the internal electrode side lamp end and the luminance when the tube power is 4.0 W. FIG. 9 is a graph showing the effect of lighting frequency and tube power on the light emission state. FIG. 10 is a graph showing lighting efficiency. FIG. 11 is a diagram showing a tube voltage and a tube current of a discharge lamp by a conventional pulse inverter. [Description of Signs] 1 DC power supply 2 Switching circuit 3 Pulse transformer 4 Discharge lamp

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-112290 (JP, A) JP-A-6-163006 (JP, A) JP-A-11-297278 (JP, A) JP-A-57- 61294 (JP, A) JP-A-7-45388 (JP, A) JP-A-3-12398 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 41/24 H01J 65 / 00

Claims (1)

(57) [Claims 1] A phosphor film is formed on the inner surface of a glass bulb.
And it was sealed to one end of the glass outer electrode and the glass bulb formed by winding a metal wire spirally on the outer surface of the valve
Lighting method of external electrode type fluorescent discharge lamp with internal electrode
A is the at 50KHz repetition frequency from 10 between the external electrode and the internal electrode, the tube power supplied into the glass bulb is driven as below 4.0kw exceed 1.0 kw, the impact ratio A lighting method for an external electrode type fluorescent discharge lamp, characterized by applying a rectangular wave pulse voltage set to 50 ± 20% .