JPH0689792A - Rare gas discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent bent or fluctuation of the positive light beam of a rare gas discharge lamp. CONSTITUTION:A DC current from a DC power supply 12 is converted by an inverter circuit 15 into a high frequency AC current, and the main electrodes 14a, 14b in a pair of a rare gas discharge lamp 14 fitted with an aux. electrode 18 at the periphery of a glass bulb 14c are connected with a pair of output terminals 16a, 16b of the inverter 13 which boosts the voltage with a booster oscillating transformer 16. The resultant impedance Xa of the first current limiting capacitor 19 and the second current limiting capacitor 20 is set approx. the same as the impedance Xb of a third current limiting capacitor 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare gas discharge lamp lighting device suitable as a reading light source for OA equipment such as a scanner and a facsimile, and more particularly to a rare gas discharge lamp lighting device having an improved current limiting capacitor.

[0002]

2. Description of the Related Art Generally, when a rare gas discharge lamp is used as a reading light source for a scanner, a facsimile, etc., FIG.
As shown in FIG. 6, the rare gas discharge lamp 1 is inserted in a U-shaped trough-shaped light-shielding case 2 having conductivity and light-shielding property without contact, and light is emitted only in one direction indicated by an arrow in the figure. Others are shielded from light.

In the rare gas discharge lamp 1, for example, a pair of main electrodes 4a and 4b are sealed in a straight tubular glass bulb 3 to seal a rare gas such as xenon at several tens to several hundreds Torr, while An auxiliary electrode 5 is provided on the outer peripheral surface of the bulb 3 over substantially the entire length. The auxiliary electrode 5 reduces the starting voltage of the rare gas discharge lamp 1 and is formed between the pair of main electrodes 4a and 4b. By always pulling the positive column 6 to the external electrode 5 side, the positive column 6 is always formed at a fixed position, and as a result,
The light emission is stabilized, and the reading accuracy is improved.

The lighting device for lighting the rare gas discharge lamp 1 converts direct current from a direct current power source into high frequency alternating current by an inverter circuit, and further boosts this alternating current by a step-up oscillating transformer to generate high frequency voltage. The discharge lamp 1 is turned on by applying it between the pair of main electrodes 4a and 4b.

[0005]

However, such a conventional rare gas discharge lamp lighting device has a problem that the positive column 6 is bent or shaken as shown in FIG.

That is, in the conventional rare gas discharge lamp lighting device, one of the pair of main electrodes, for example, 4a, and one end of the auxiliary electrode 5 are respectively connected to one of the output ends of the step-up oscillation transformer via the first power feeding path. Connected, and electrically connecting the combined impedance of the first and second current limiting capacitors interposed in the middle of the first power feeding path and the other main electrode 4b to the other output end of the step-up oscillation transformer. The impedance of the third current limiting capacitor interposed in the middle of the second power feeding path is different.

Therefore, for example, as shown in FIG. 7, the voltage Va and the current Ia applied to one main electrode 4a are smaller than the voltage Vb and the current Ib applied to the other main electrode 4b. When, that is, Va <Vb, Ia <I
When b, the waveforms of Va and Ia are Vb and Ia
The amplitude is smaller than the waveform of b, and both waveforms are asymmetric with respect to the reference line indicated by OV or OA.

Therefore, the electrons in the positive column 6 pass through the stray capacitance c between the rare gas discharge lamp 1 and the light shielding case 2 and leak to the light shielding case 2, as shown in FIG. Bending or shaking occurs at 6, and the light emission or irradiation direction is not stable and the reading accuracy and the like are reduced.

Therefore, the present invention has been made in view of such circumstances, and an object thereof is to prevent the bending or rocking of the positive column of a rare gas discharge lamp and to highly stabilize the light emission. It is to provide a discharge lamp lighting device.

[0010]

SUMMARY OF THE INVENTION In the present invention, the problem of the conventional rare gas discharge lamp lighting device is that the combined impedance of the first and second current limiting capacitors and the impedance of the third current limiting capacitor are not equal. It was made based on the new finding that it is caused by the following.

That is, according to the present invention, an inverter circuit reversely converts direct current into alternating current, and then this alternating current is oscillated at a predetermined frequency by a step-up oscillating transformer, and the step-up inverter and the outer peripheral surface of a valve incorporating a pair of main electrodes are provided. A rare gas discharge lamp in which an auxiliary electrode is provided in the axial direction, a light shield having conductivity for surrounding the outer periphery of the rare gas discharge lamp other than the irradiation direction, and one of a pair of output ends of the transformer. ,
A first and a second current limiting capacitors, which are respectively interposed in the middle of both power supply paths electrically connected to one of the pair of main electrodes of the rare gas discharge lamp and one end of the auxiliary electrode, respectively; In the rare gas discharge lamp lighting device according to the first aspect of the present invention, there is provided a rare gas discharge lamp lighting device having a third current limiting capacitor interposed in the middle of a power feeding path for electrically connecting the other output end to the other main electrode of the rare gas discharge lamp. The combined impedance of the second current limiting capacitor and the impedance of the third current limiting capacitor are made substantially equal to each other.

[0012]

Since the combined impedance of the first and second current limiting capacitors is equal to the impedance of the third current limiting capacitor, the waveforms of the voltage and current applied to the pair of electrodes of the rare gas discharge lamp are the same for both electrodes. Are almost equal.

For this reason, it is possible to prevent the electrons in the positive column formed between the pair of electrodes from passing through the stray capacitance between the rare gas discharge lamp and the light shield and leaking to the light shield. Therefore, it is possible to prevent the positive column from being bent or shaken and stabilize the light emission or irradiation direction. Therefore, when the rare gas discharge lamp is used as a reading light source for a scanner or a facsimile, the reading accuracy can be improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an electronic circuit diagram of an embodiment of the present invention. In the figure, a rare gas discharge lamp lighting device 11 includes an inverter 13 connected to a DC power source 12 and a rare gas discharge lamp 14.
Are electrically connected to light at high frequency.

The inverter 13 outputs a direct current from the direct current power source 12 to a high frequency (for example, 23 to 25) by the inverter circuit 15.
KHz) alternating current and then boosted by the boosting oscillation transformer 16. The pair of output terminals 16a, 16b of the transformer 16 have first and second power feeding paths 17a, 17b.
The pair of main electrodes 14a and 14b of the rare gas discharge lamp 14 are connected to each other via 17b.

The first power supply path 17a branches the power supply branch path 17aa in the middle of the first power supply path 17a, and the end of the branch branches to the rare gas discharge lamp 14.
Is connected to one end of the auxiliary electrode 18.

The first feeding path 17a and its feeding branch path 17a
The first and second current limiting capacitors 19 and 20 are provided in the middle of a, while the third current limiting capacitors 19 and 20 are provided in the middle of the second power feeding path 17b.
The current limiting capacitors 21 are provided respectively to prevent an overcurrent from flowing into the pair of main electrodes 14a and 14b when the rare gas discharge lamp 14 is turned on.

Then, the first and second current limiting capacitors 19,
20 combined impedance Xa and third current limiting capacitor 2
The impedance Xb of 1 is set to be substantially equal.
The range of equality of these two impedances is within the range of allowable error of circuit components, and for example, an error of up to 40% is allowable.

On the other hand, in the rare gas discharge lamp 14, for example, a pair of main electrodes 14a and 14b are sealed in both axial ends of a straight tubular glass bulb 14c, and a phosphor film 14d is formed on the inner peripheral surface of the bulb 14c. Is almost entirely covered.

The valve 14c is filled with a rare gas such as xenon at a pressure of several tens to several hundreds of Torr, while the auxiliary electrode 18 made of a conductive film is deposited on the outer peripheral surface of the valve 14c over substantially the entire length. is doing.

Therefore, by applying a required electric potential to the auxiliary electrode 18, the starting voltage of the rare gas discharge lamp 14 can be reduced and the pair of main electrodes 14a, 1
The positive columns formed between 4b can be drawn to the auxiliary electrode 18 side over substantially the entire length.

When the rare gas discharge lamp 14 of the rare gas discharge lamp lighting device constructed as described above is used as a reading light source for a scanner, a facsimile or the like, as shown in FIG. The rare gas discharge lamp 14 is housed in a light shielding case 22 made of metal having conductivity with a required gap around the outer periphery thereof, and light from the rare gas discharge lamp 14 is opened at one opening end of the light shielding case 22. The light is emitted only in one direction indicated by the arrow in the figure, and the other is shielded.

Therefore, since the light shielding case 22 has conductivity, a plurality of stray capacitances c are distributed between the light shielding case 22 and the outer peripheral surface of the rare gas discharge lamp 14, but the pair of main electrodes 14a, 14b.
The positive columns 23 formed between them are attracted to the side of the auxiliary electrode 18 for almost the entire length by the electric field of the auxiliary electrode 18 or the like, so that the positive columns 23 are always formed in a fixed position and the emission or irradiation direction is stabilized. be able to.

According to the present embodiment, the combined impedance Xa of the first and second current limiting capacitors 19 and 20.
And the impedance Xb of the third current limiting capacitor 21 are substantially equal to each other, one of the main electrodes 14 as shown in FIG.
Since the waveforms of the voltage Va and the current Ia applied to the a are almost the same as the voltage Vb and the current Ib applied to the other main electrode 14b and have a symmetrical shape, as shown in FIG. Bending and shaking can be prevented.

Therefore, since the emission or irradiation direction of the rare gas discharge lamp 14 is stable, the reading accuracy can be improved when the rare gas discharge lamp device is used as the reading light source.

[0027]

As described above, according to the present invention, the combined impedance of the first and second current limiting capacitors electrically connected to the pair of main electrodes of the rare gas discharge lamp and the other main electrode are connected. Since the impedance of the third current limiting capacitor is made substantially equal to each other, the waveforms of the voltage and the current applied between the pair of main electrodes are substantially symmetrical between both electrodes. For this reason, it is possible that electrons in the positive column formed between the pair of electrodes pass through a plurality of stray capacitances between the rare gas discharge lamp and the conductive light shield and leak to the light shield. Since this can be prevented, it is possible to prevent the positive column from being bent or shaken, and to stabilize the light emission or irradiation direction. Therefore, when the rare gas discharge lamp is used as a reading light source for a scanner or a facsimile, the reading accuracy can be improved.

[Brief description of drawings]

FIG. 1 is an electronic circuit diagram of an embodiment of a rare gas discharge lamp lighting device according to the present invention.

FIG. 2 is a vertical cross-sectional view of the rare gas discharge lamp shown in FIG. 1 housed in a light shield case.

FIG. 3 is a time chart showing waveforms of voltage and current applied between the pair of main electrodes shown in FIG. 1 in comparison with each other.

4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a vertical cross-sectional view showing a state in which a conventional rare gas discharge lamp is housed in a light shielding case.

6 is a sectional view taken along line VI-VI of FIG.

7 is a time chart showing waveforms of a voltage and a current applied between the pair of main electrodes shown in FIG. 6, respectively.

[Explanation of symbols]

 11 Noble Gas Discharge Lamp Lighting Device 12 DC Power Supply 13 Inverter 14 Noble Gas Discharge Lamp 14a, 14b A Pair of Main Electrodes 14d Phosphor Film 15 Inverter Circuit 16 Boost Oscillation Transformer 16a, 16b A Pair of Output Ends 17a of Boost Oscillating Transformer 16a 1st Feed line 17b Second feed line 17aa Branch feed line 18 Auxiliary electrode 19 First current limiting capacitor 20 Second current limiting capacitor 21 Third current limiting capacitor 23 Positive column

Claims (1)

[Claims] 1. An inverter circuit converts direct current into alternating current, and then this alternating current is oscillated at a predetermined frequency by a step-up oscillating transformer, and an inverter for boosting the voltage and an auxiliary electrode on the outer peripheral surface of a valve containing a pair of main electrodes are provided. A rare gas discharge lamp provided along the axial direction, a light-shielding member having conductivity surrounding the outer periphery of the rare gas discharge lamp other than the irradiation direction, and one of a pair of output ends of the transformer are connected to the rare gas discharge lamp. First and second current limiting capacitors respectively interposed in the middle of both power supply paths electrically connected to one of the pair of main electrodes of the discharge lamp and one end of the auxiliary electrode, and the other output of the transformer. A rare gas discharge lamp lighting device, comprising: a third current limiting capacitor interposed in the middle of a power supply path for electrically connecting an end to the other main electrode of the rare gas discharge lamp. of A rare gas discharge lamp lighting device, wherein the combined impedance of the current limiting capacitor and the impedance of the third current limiting capacitor are made substantially equal to each other.