JP2000106145A - Cold cathode-ray tube structure, drive method for the cold cathode-ray tube, and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize increase of light quantity, while restraining the noise radiation level of a cold cathode-ray tuber for emitting the light with the excitation of the electrons inside the tube inside by the high-frequency high voltage. SOLUTION: Three discharging electrodes 3, 4, 5 are provided in an outer wall of a cold cathode-ray tube 1, and the three-phase alternating current voltage is applied to each discharging electrode. The discharging electrodes 3, 4, 5 are arranged, so that each phase current effective value flowing between each discharging electrode becomes equal to each other. At the application of this cold cathode-ray tube 1 for an image reading device, a three-phase high- voltage power source 36 is provided at a fixed part 3 inside the image reading device main body, and drive power is supplied to each discharging electrodes 3, 4, 5 provided on a movable mirror base from the three-phase high-voltage power source 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-cathode tube structure and a driving method of a cold-cathode tube in a cold-cathode tube which emits light when electrons in the tube are excited by high-frequency high voltage, and a light source for illuminating the cold-cathode tube with a document. The present invention relates to an image reading apparatus used as a computer.

[0002]

2. Description of the Related Art Conventionally, a cold-cathode tube used as an illumination light source for reading a document of an image reading apparatus emits light by performing electron excitation in the tube by a high-frequency high voltage applied to two electrodes provided on the outer wall of the cold-cathode tube. .

However, as the reading speed of the image reading device increases, the image storage time of the image sensor must be shortened. As a result, the image signal output of the image sensor decreases. To get
It is necessary to increase the light amount of an illumination light source, that is, a cold cathode tube.

Therefore, conventionally, in order to increase the light amount of the cold cathode fluorescent lamp, the composition of the rare gas and the fluorescent material in the cold cathode fluorescent lamp are adjusted, and the high-frequency high voltage waveform applied to the two external electrodes of the cold cathode fluorescent lamp is changed to a sine wave. (Sinusoidal wave) is changed to a rectangular wave, and the excitation current is increased to realize an increase in the amount of light.

[0005]

However, in the above-mentioned conventional image reading apparatus, although the light intensity can be increased by making the cold cathode tube excitation voltage waveform a rectangular wave, it is generated by a high voltage rectangular wave. The unnecessary radiation level of the device itself has increased remarkably, and there has been a problem that it is difficult to satisfy the unnecessary radiation regulation value of the device specified in each country with the conventional configuration.

In particular, when a high-voltage power supply for driving a cold-cathode tube is installed in a non-movable portion of an image reading apparatus, a rectangular-wave high voltage is applied to a cold-cathode tube provided in a movable portion by using electric wires. As a result, not only the noise radiated from the high-voltage power supply, but also the noise level radiated from this electric wire is extremely large.

As a normal noise countermeasure, a radiation countermeasure such as shielding a noise source is adopted. However, since it is necessary to transmit an original image on the original plate through the platen glass to the inside of the apparatus, a metal member or the like is used. However, since it is impossible to shield the platen, it is a big problem how to suppress noise radiation.

At present, it is urgently necessary to reduce the size of the image reading apparatus in the era. For this purpose, the driving power supply of the movable part cold cathode fluorescent tube for reading the original must be installed in the non-movable part. As described above, there is a problem in that a choice between an increase in the amount of light and a measure against noise radiation must be made.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a cold-cathode tube structure and a cold-cathode tube capable of realizing an increase in the amount of light of a cold-cathode tube while suppressing a noise radiation level low. It is an object of the present invention to provide a method for driving a cathode tube and an image reading device.

[0010]

The cold cathode tube structure, the driving method of the cold cathode tube, and the image reading apparatus according to the present invention are configured as follows.

(1) The cold-cathode tube structure has a three-electrode structure in which three discharge electrodes for exciting electrons in the cold-cathode tube are provided outside the cold-cathode tube.

(2) In the cold cathode tube structure of (1), three discharge electrodes are provided on the outer wall of the cold cathode tube, and the high frequency high voltage applied to each discharge electrode is a three-phase AC voltage.

(3) In the cold-cathode tube structure of (2), three discharge electrodes are arranged on the outer wall of the cold-cathode tube so that the effective value of each phase current flowing between each discharge electrode is equal.

(4) In the method of driving a cold cathode tube, three discharge electrodes for exciting electrons in the cold cathode tube are provided outside the cold cathode tube, and a three-phase alternating current is applied to each discharge electrode. A high frequency high voltage was applied.

(5) In the method for driving a cold cathode tube according to the above (4), the three discharge electrodes arranged on the outer wall of the cold cathode tube so that the effective value of each phase current flowing between each discharge electrode becomes equal. Was applied with a three-phase AC voltage.

(6) In the image reading apparatus, a cold cathode tube is provided as a light source for illuminating the original, and three discharge electrodes for exciting electrons in the cold cathode tube are provided outside the cold cathode tube. The pole structure was adopted.

(7) In the image reading apparatus of the above (6), the cold cathode tube is provided on a movable mirror table for scanning the original in the apparatus main body, and the scanned original image is projected on the image sensor. .

(8) In the image reading apparatus of (6) or (7), three discharge electrodes are provided on the outer wall of the cold cathode tube, and a three-phase alternating high frequency high voltage is applied to each discharge electrode. I made it.

(9) In the image reading apparatus of the above (8), three discharge electrodes are arranged on the outer wall of the cold-cathode tube so that the effective value of each phase current flowing between each discharge electrode becomes equal.

(10) In any one of the image reading devices (7) to (9), driving power is supplied from a three-phase high-voltage power supply provided in a non-movable portion in the device main body to each discharge electrode on the movable mirror base. Was supplied.

[0021]

FIG. 1 is a circuit diagram showing the main structure of a cold cathode tube lighting device according to the present invention.

In FIG. 1, reference numeral 1 denotes a three-electrode cold-cathode tube (FL) having three discharge electrodes as an illumination light source of an image reading device.
1), 2 is a cold-cathode tube opening (OPN) that emits light emitted by the cold-cathode tube 1, 3 is a first discharge electrode (P) that applies a high-frequency high-frequency voltage to make the cold-cathode tube 1 emit light.
1) and 4 are second discharge electrodes (P2) for applying a high-frequency high-frequency voltage provided on the outer wall of the cold-cathode tube 1 for causing the cold-cathode tube 1 to emit light. A third discharge electrode (P3) for applying a high-frequency voltage.

Reference numeral 6 denotes three discharge electrodes 3, 4, 4 of the cold cathode tube 1.
Reference numeral 5 denotes a three-phase step-up transformer (T1) for generating a high-frequency high voltage to be applied to the reference numeral 5. Reference numeral 7 denotes a first-phase primary winding (W1) for applying the first-phase low-voltage current to the three-phase step-up transformer 6.
1) and 8 are second-phase primary windings (W2) for applying the second-phase low-voltage current to the three-phase boost transformer 6, and 9 are for applying the third-phase low-voltage current to the three-phase boost transformer 6. And a third phase primary winding (W3).

Reference numeral 10 denotes a first-phase boost winding (HW1) for boosting the primary power supplied to the first-phase primary winding 7 of the three-phase boost transformer 6; A second phase boost winding (HW2) 12 for boosting the primary power supplied to the phase primary winding 8 is used to reduce the primary power supplied to the third phase primary winding 8 of the three-phase boost transformer 6. A third phase boost winding (HW3) 13 for boosting is connected in parallel with the first phase primary winding 7 and a first phase resonance capacitor (C1) for primary voltage resonance, and 14 is a second phase primary winding. A second-phase resonance capacitor (C2) connected in parallel with 8 for primary voltage resonance, and a third-phase resonance capacitor (C3) 15 connected in parallel with the third-phase primary winding 9 for primary voltage resonance.

Reference numerals 16 and 17 denote switching transistors (Q1 and Q2) for switching the current supplied to the first phase primary winding 7, and reference numerals 18 and 19 denote switching transistors (Q1 and Q2) for switching the current supplied to the second phase primary winding 8. Q3, Q4), 20, 21 are switching transistors (Q5, Q6) for switching the current supplied to the third phase primary winding 9, and 22, 23 are the base currents of the transistors for turning on the switching transistors 16, 17, respectively. Resistance capacitor (CR
1), 24, 25 are resistance capacitors (CR2), 26, 2 for applying the base currents of the transistors to turn on the switching transistors (18, 19), respectively.
Reference numeral 7 denotes a resistance capacitor (CR3) that applies a base current of the switching transistors 20 and 21 to turn on the transistors.

An oscillator (OSC) 28 is a driving source of the CCFL driver, and a ternary synchronous counter (CN) 29 receives a CLK signal from the oscillator 28 and performs a ternary counting operation.
T) and 30 are signals that receive the count signal of the ternary counter 29 and output a signal when the count value is (00) bin.
An ND gate (G1), 31 receives a count signal of the ternary counter 29, and outputs a signal when the count value is (01) bin. An AND gate (G2), 32 receives a count signal of the ternary counter 29, and counts. But (10) bi
This is an AND gate that outputs a signal when it is n.

Reference numeral 33 denotes a JK flip-flop (FF1) for receiving the outputs of the AND gates 30 and 32 and the CLK signal from the oscillator 29, and generating a first-phase pulse signal.
Is a signal for receiving the outputs of the AND gates 31 and 32 and the CLK signal from the oscillator 28 to generate a second phase pulse signal.
K flip-flop (FF2), 35 is an AND gate 3
A JK flip-flop (FF3) for receiving the outputs of 0, 31 and the CLK signal from the oscillator 28 to generate a third-phase pulse signal. 23
Are applied to the switching transistors 16 and 17 via the switch.

The non-inverted output and the inverted output from the JK flip-flop 34 are connected to resistance capacitors 24 and 25, respectively.
Are applied to the switching transistors 18 and 19 via the switch. The normal output and the inverted output from the JK flip-flop 35 are applied to the switching transistors 21 and 22 via the resistance capacitors 26 and 27, respectively.

[0029]

(Equation 1)

The lighting operation of the cold-cathode tube lighting device having the above configuration will be described with reference to FIG.

When the supply of voltage from the power supply 36 starts, the oscillator 28 generates a CLK signal having a natural frequency at the timing shown in FIG. This CLK signal allows the ternary synchronous counter 2
9 starts the counting operation. The output of the ternary counter 29 changes from (00) bin to (01) bin to (10) bin. The count value of the AND gate 30 is (00) b.
in, the signal B is output, the AND gate 31 outputs a signal C when the count value is (01) bin, and the AND gate 32 outputs the signal value (10) b
When the signal is in, the signal A is output.

The J input terminal of the JK flip-flop 33 has an output terminal of the AND gate 32, and the K input terminal has an AN terminal.
The output terminal of the D gate 30 is connected. The JK flip-flop 33 receives both inputs and the CLK signal from the oscillator 28 and generates a new periodic signal φ1 of HI for three cycles of CLK and LOW for three cycles at the Q terminal of the flip-flop 33. The Q * terminal of the flip-flop 33 generates the same-period signal φ1 * whose polarity is inverted from that of the Q terminal.

Similarly, the Q and Q * terminals of the JK flip-flop 33 are connected to the Q and Q * terminals of the JK flip-flop 34, respectively.
The same-period signal φ whose phase is delayed by 120 degrees (two CLK signal periods) with respect to the periodic signals φ1 and φ1 * output from the terminals.
2, φ2 * is generated. Similarly, JK flip-flop 3 is connected to the Q and Q * terminals of JK flip-flop 35.
4, the periodic signals φ2 and φ2 * output from the Q and Q * terminals
Signals φ3, φ3 * whose phases are delayed by 120 degrees
Is generated.

As described above, each flip-flop 33, 3
Periodic signals φ1, φ2,
φ3 is a three-phase CLK signal whose phase is shifted from each other by 120 degrees. The Q of each flip-flop 33, 34, 35
The periodic signal output from the * terminal is also φ1 *, φ2 *, φ3
* Also becomes a three-phase CLK signal whose phase is shifted from each other by 120 degrees.

The periodic signal φ1 output from the Q terminal of the JK flip-flop 33 turns on the switching transistor 17 through the resistance capacitor 23 at the time of the HI level. When the transistor 17 is turned on, a current is applied from the power supply 36 to the first-phase primary winding 7. This current excites the core of the three-phase step-up transformer 6 to store energy.

Subsequently, the current due to the excitation energy stored by turning off the transistor 17 resonates with the capacitor 13 (periodical waveform φ1a in FIG. 2). When the transistor 17 is turned off, the transistor 16 is turned on at the same time, and the same resonance current flows through the first phase primary winding 7 as described above. A similar current resonance state occurs with the current phases shifted by 120 degrees with respect to the second-phase primary winding 8 and the third-phase primary winding 9 (the periodic waveforms φ2a and φ3a in FIG. 2).

The resonance current energy generated in each of the primary windings passes through the core of the three-phase boosting transformer 6, the first phase boosting winding 10, the second phase boosting winding 11, and the third phase boosting winding 12.
Similarly, a high voltage is generated in which the mutual phases are different from each other by 120 degrees and the voltage is boosted by the boost ratio of the primary winding and the secondary winding. Here, the first-phase boost winding 10, the second-phase boost winding 11, and the third-phase boost winding 12 have a three-phase delta connection configuration in which both ends of the windings are connected to each other. There are feed lines 37a, 37b, 37c
To the respective discharge electrodes 3, 4, 5 of the three-electrode cold cathode tube 1 as three-phase high voltages HVφ1, HVφ2, HVφ3.

In the three-electrode cold-cathode tube 1, the electrons in the tube are excited in three phases by the applied three-phase high voltage, and the fluorescent paint in the tube is stimulated to emit light. Here, the discharge electrodes 3, 4, and 5 facing each other of the three-electrode cold-cathode tube 1 are arranged such that the electrode centers are located at 120 degrees from the center of the cold-cathode tube, and the areas of the electrodes are equal. By doing so, the load balance of the three-phase delta connection becomes uniform, and each phase current (effective value) becomes equal.

As described above, in the present embodiment, the load of the cold cathode tube can be divided into three parts by changing the structure of the cold cathode tube from three external discharge electrodes to three electrodes. The discharge current density can be increased by high-voltage three-phase excitation using the cold-cathode tube load as a three-phase load. It can be achieved without using waves.

Further, since the high voltage applied to the cold cathode tube external electrode is a three-phase high voltage, it is not necessary to perform the rectangular wave high voltage excitation necessary for emitting light with high brightness in the conventional two-electrode tube. In addition, the excitation current density can be increased by three-phase sine wave driving, and high-luminance light emission is realized.

Further, by arranging the electrode center position of the cold cathode tube external electrode every 120 degrees from the center of the cold cathode tube and making each electrode area equal, the load balance of the three-phase high-voltage power supply becomes uniform, It is possible to stabilize the operation of the tube lighting device and to suppress noise radiation from the power transmission line.

Further, by performing the sine wave drive, it is possible to largely suppress the unnecessary radiation noise level which was difficult to reduce by the rectangular wave drive. The cold-cathode tube power supply, which had to be installed in a non-movable part, can be transferred to the non-movable part, and power can be supplied from the non-movable part using a power supply line. This reduces the size and weight of the movable part mirror base. Thus, the size of the image reading apparatus can be minimized.

[0043]

As described above, according to the present invention,
Since a three-electrode structure having three discharge electrodes for exciting electrons in the cold cathode tube is provided outside the cold cathode tube, the discharge current density can be increased and the cold cathode tube can be reduced while suppressing the noise radiation level. There is an effect that the light amount can be increased.

Since three discharge electrodes are provided on the outer wall of the cold cathode tube and the high-frequency high voltage applied to each discharge electrode is a three-phase AC voltage, the excitation current density is increased by three-phase sine wave driving. Thus, there is an effect that the light amount of the cold cathode tube can be increased while the noise radiation level is kept low.

Further, since the three discharge electrodes are arranged on the outer wall of the cold-cathode tube so that the effective values of the respective phase currents flowing between the respective discharge electrodes become equal, the respective phases of the three-phase high-frequency high-voltage power supply are balanced. This has the effect of stabilizing the operation of the power supply circuit and reducing noise radiation from the power transmission path.

When the cold-cathode tube having the above structure is applied to an image reading apparatus as a light source for illumination, noise can be prevented, so that the power supply for driving the cold-cathode tube is moved to the non-movable part, It is possible to supply power using a power supply line, and by reducing the size and weight of the mirror base of the movable part,
There is an effect that the device size of the image reading device can be minimized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main configuration of a cold cathode tube lighting device according to the present invention.

FIG. 2 is a timing chart showing signal waveforms of the cold-cathode tube lighting device of one embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 three-electrode cold-cathode tube 2 cold-cathode tube opening 3 first discharge electrode 4 second discharge electrode 5 third discharge electrode 6 three-phase step-up transformer 28 oscillator 36 DC power supply

Claims (10)

[Claims] 1. A cold-cathode tube structure having a three-electrode structure in which three discharge electrodes for exciting electrons in the cold-cathode tube are provided outside the cold-cathode tube. 2. The cold-cathode tube according to claim 1, wherein three discharge electrodes are provided on the outer wall of the cold-cathode tube, and the high-frequency high voltage applied to each discharge electrode is a three-phase AC voltage. Construction. 3. The cold-cathode tube according to claim 2, wherein three discharge electrodes are arranged on the outer wall of the cold-cathode tube such that the effective values of the respective phase currents flowing between the respective discharge electrodes become equal. Construction. 4. A three-phase AC high-frequency high voltage is applied to each discharge electrode for providing three discharge electrodes for exciting electrons in the cold-cathode tube outside the cold-cathode tube. The driving method of the cold cathode tube. 5. A three-phase AC voltage is applied to three discharge electrodes arranged on the outer wall of the cold cathode tube so that the effective value of each phase current flowing between each discharge electrode becomes equal. Item 5. The method for driving a cold cathode tube according to Item 4. 6. A cold-cathode tube as a light source for illuminating a document,
An image reading apparatus having a three-electrode structure in which three discharge electrodes for exciting electrons in the cold cathode tube are provided outside the cold cathode tube. 7. The cold-cathode tube is provided on a movable mirror table for scanning a document in the apparatus main body, and projects the scanned document image onto an image sensor.
The image reading device according to claim 1. 8. The image reading apparatus according to claim 6, wherein three discharge electrodes are provided on an outer wall of the cold cathode tube, and a high-frequency high voltage of three-phase alternating current is applied to each discharge electrode. 9. The image reading apparatus according to claim 8, wherein three discharge electrodes are arranged on the outer wall of the cold cathode tube so that the effective value of each phase current flowing between each discharge electrode is equal. . 10. A device provided in a non-movable part in an apparatus main body.
10. The image reading apparatus according to claim 7, wherein driving power is supplied from a phase high-voltage power supply to each discharge electrode on the movable mirror base.