JPH0789480B2 - Discharge starter for cold cathode discharge tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge starter for a cold cathode discharge tube used as a backlight of a liquid crystal viewfinder such as a VTR with a built-in camera. This is to improve the starting efficiency.

[0002]

2. Description of the Related Art Conventionally, as a discharge starting assisting means for cold cathode discharge tubes, it is described, for example, on page 72 of "Lighting Engineering" edited by The Institute of Electrical Engineers of Japan (published by Ohmsha, published on July 15, 1938). There is something. This is a circuit as shown in FIG. 19, in which 1 is a discharge tube, 2 is a conductor provided near the discharge tube 1, 3 is a negative electrode, 4 is a positive electrode, 5 is a switching means, 6 Is the power supply.

In the above structure, when the switching means 5 switches, a potential difference is generated between the negative electrode 3 and the positive electrode 4 to generate an electric field, and electrons inside the discharge tube 1 are excited. Movement is slow and does not easily discharge. Therefore, a conductor 2 is provided in the vicinity of the discharge tube 1, the conductor 2 is connected to the negative side of the voltage so as to have the same potential as the negative electrode 3, and the potential difference between the conductor 2 and the positive electrode 4 is increased to concentrate the electric field. By doing so, discharge is facilitated.

More specifically, the discharge start of the cold cathode discharge tube is excited by the electric field generated by the voltage applied to each electrode of the electrons near the negative electrode and the ions near the positive electrode. Excited electrons are accelerated toward the positive electrode and ions are accelerated toward the negative electrode. The accelerated electrons generate gas (Hg, A
It collides with r) and excites or ionizes them to generate secondary electrons. The secondary electrons sustain the discharge. In the hot cathode discharge tube, the initial filament is forcibly emitted by heating the cathode filament, but in the cold cathode discharge tube, since there is no cathode filament, the initial electric field and the initial ion are generated by the electric field generated near the electrode. Therefore, the discharge starting assisting means as described above is required.

[0005]

However, since the cold cathode discharge tube used for the backlight of a liquid crystal viewfinder such as a VTR with a built-in camera is mounted inside a viewfinder (a cool and dark place) where light does not enter, a discharge is generated. There is a problem that the movement of electrons inside the tube is extremely slow and the discharge assisting means does not discharge (light up) reliably.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a first conductor provided close to the negative electrode side of the cold cathode discharge tube and a positive electrode side of the cold cathode discharge tube are provided. A second conductor provided in close proximity to the first conductor, and a high voltage is supplied to the first conductor and a voltage lower than the voltage supplied to the first conductor is supplied to the second conductor. In a discharge starting circuit of a cold cathode discharge tube, the first and second conductors of the cold cathode discharge tube are formed in a shape in which the area decreases from the vicinity of the end portion of the cold cathode discharge tube toward the vicinity of the emission central portion. It is intended to provide a discharge starting circuit.

Further, there is provided a first conductor provided close to the negative electrode side of the cold cathode discharge tube and a second conductor provided close to the positive electrode side of the cold cathode discharge tube. In the discharge starting circuit of the cold cathode discharge tube, wherein a high voltage is supplied to the first conductor and a voltage lower than the voltage supplied to the first conductor is supplied to the second conductor, It is intended to provide a discharge starting circuit for a cold cathode discharge tube in which one of the two conductors has a shape in which the area decreases from the vicinity of the end of the cold cathode discharge tube toward the vicinity of the emission center. .

[0008]

With the above structure, the potential difference between the negative electrode of the cold cathode discharge tube and the first conductor and the potential difference between the positive electrode of the cold cathode discharge tube and the second conductor become large. , The electric field near each electrode concentrates and is easily discharged.

Further, by forming the first and second conductors as described above, the electrolysis is concentrated near the emission center of the cold cathode discharge tube, and the cold cathode discharge tube can be easily turned on.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, FIGS. 17A and 17B show a printed circuit board on which the cold cathode discharge tube of the present invention is mounted. The figure (a) has shown the front surface side of a printed circuit board, and the figure (b) has shown the back surface side of a printed circuit board. In the figure, 16 is a printed circuit board, 19 and 20 are through holes,
17 is a high pressure pattern, 18 is a low pressure pattern, 12 and 1
3 is a connecting portion, and the connecting portion 12 is the discharge tube main body 7
Of the negative electrode 8 and the connecting portion 13 is connected to the positive electrode 9 of the discharge tube body 7.

As shown in FIG. 2B, the high pressure pattern 17
Is connected to the circuit pattern on the front side of the printed circuit board 16 through the through hole 20, and the low voltage pattern 18
Are connected to the circuit pattern on the front side of the printed circuit board 16 through the through holes 19.

Next, FIG. 1 shows a cold cathode discharge tube used in the present invention. In the figure, 7 is a discharge tube body, 8 is a negative electrode provided inside the discharge tube body 7, 9 is a positive electrode also provided inside the discharge tube body 7, and 10 is close to the back surface of the discharge tube body 7. The high-voltage conductor 10 and the low-voltage conductor 11 which are the arranged high-voltage conductors as the first conductor and 11 are the low-voltage conductors as the second conductors which are also closely arranged on the back surface of the discharge tube body 7 are The shape is such that the area is reduced (tapered) from the vicinity of the end portion to the vicinity of the central portion 21, whereby the electric field at the time of starting is concentrated near the central portion and the discharge tube can be easily lighted. You can do it.

In the present embodiment, each of the conductors is made of a conductive double-sided tape and is attached to the back surface of the discharge tube body 7. Further, the discharge tube body 7 is configured to be attached to the above-mentioned printed board 16 by the conductive double-sided tape.

Since the discharge tube is attached to the printed circuit board 16 by the conductive double-sided tape, the high voltage pattern 17 on the printed circuit board 16 and the high voltage conductor 10 on the discharge tube body 7 are electrically connected. Then, the low voltage pattern 18 on the printed circuit board and the low voltage conductor 11 on the discharge tube body 7 are electrically connected.

Next, FIG. 18 is a circuit block diagram showing an outline of the drive circuit of the discharge tube. The power supply voltage terminal (+5 V) of the connector (CN1) and the control signal input terminal (SYN).
A power supply voltage and a control signal are supplied to C) from an external circuit (not shown). When a control signal is supplied from the external circuit to the control signal input terminal (SYNC), the switching element (Q1) performs a switching operation to switch the power supply voltage.

Since the switched power supply voltage is boosted by the transformer (T1) to a high voltage, a high switched voltage is supplied to the positive electrode 9 of the discharge tube body 7, while the negative electrode 8 is not boosted. Voltage will be applied. On the other hand, the low-voltage conductor 11 adjacent to the positive electrode 9 is grounded, and the high-voltage conductor 10 adjacent to the negative electrode 8 is supplied with the switched high-voltage like the positive electrode 9 of the discharge tube body 7. Therefore, the positive electrode 9 and the low-voltage conductor 1
1 and the potential difference between the negative electrode 8 and the high-voltage conductor 10 become large, and the electric field in the vicinity of each of the electrodes becomes high, so that discharge is easily performed.

The low-voltage electrode 11 on the side of the positive electrode 9 is connected (grounded) to GND, but if the voltage applied to the positive electrode 9 is 1 KV or more, it can be effectively connected to the negative electrode 8. is there.

2 to 8 show another embodiment in which the shapes of the high voltage conductor 10 and the low voltage conductor 11 are changed.

In FIGS. 9 to 12, one conductor has a rectangular shape, and the other conductor has a shape in which the area decreases toward one conductor.

Further, FIGS. 13 to 16 show a structure in which one conductor is formed and the area is reduced near the center of the discharge tube.

In the embodiments shown in FIGS. 2 to 12, the shapes of the high-voltage conductor 10 and the low-voltage pattern 18 and the shapes of the low-voltage conductor 11 and the high-voltage pattern 17 are preferably substantially the same, but they are not necessarily the same. It is effective even if it is not a shape. In the case of the embodiment shown in FIGS. 13 to 16, only one of the high voltage pattern 17 and the low voltage pattern 18 is provided, and this and the conductor 14 are electrically connected. Also in this case, it is effective that the shape of the conductor 14 and the shape of the high-voltage pattern 17 or the low-voltage pattern 18 do not necessarily match. Furthermore, in this embodiment,
Although the cold cathode discharge tube used for the backlight of the liquid crystal viewfinder of the VTR with a built-in camera has been described, of course, the invention is not limited to this, and it can be applied to other electronic devices using the cold cathode discharge tube. Needless to say.

[0023]

As described above in detail, according to the present invention, the first conductor provided close to the negative electrode side of the cold cathode discharge tube and the close proximity to the positive electrode side of the cold cathode discharge tube. The second provided
A discharge starting circuit for a cold cathode discharge tube, wherein a high voltage is supplied to the first conductor and a voltage lower than the voltage supplied to the first conductor is supplied to the second conductor. In the above, the first and second conductors have a shape in which the area decreases from the vicinity of the end portion of the cold cathode discharge tube toward the vicinity of the emission central portion, and the first and second conductors are close to the negative electrode side of the cold cathode discharge tube. And a second conductor provided close to the positive electrode side of the cold cathode discharge tube, and a high voltage is supplied to the first conductor and the second conductor is provided. In the discharge starting circuit of the cold cathode discharge tube, a voltage lower than the voltage supplied to the first conductor is supplied to the conductor of the first and second
One of the conductors has a shape in which the area decreases from the vicinity of the end of the cold cathode discharge tube to the vicinity of the center of light emission, so that the discharge tube placed in a cool dark place can be reliably discharged (lighted). It can be done.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a cold cathode discharge tube of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a diagram showing another embodiment of the present invention.

FIG. 10 is a diagram showing another embodiment of the present invention.

FIG. 11 is a diagram showing another embodiment of the present invention.

FIG. 12 is a diagram showing another embodiment of the present invention.

FIG. 13 is a diagram showing another embodiment of the present invention.

FIG. 14 is a diagram showing another embodiment of the present invention.

FIG. 15 is a diagram showing another embodiment of the present invention.

FIG. 16 is a diagram showing another embodiment of the present invention.

FIG. 17 is a view showing the external appearance of a cold cathode discharge tube of the present invention.

FIG. 18 is a circuit diagram showing a drive circuit for a cold cathode discharge tube used in the present invention.

FIG. 19 is a circuit diagram showing a discharge starting circuit of a conventional cold cathode discharge tube.

[Explanation of symbols]

 7 Discharge Tube Main Body 8 Cathode Electrode 9 Positive Electrode 10 High Voltage Conductor (First Conductor) 11 Low Voltage Conductor (Second Conductor) 16 Printed Circuit Board 17 High Voltage Pattern 18 Low Voltage Pattern 19 Through Hole 20 Through Hole T1 Transformer Q1 Switching Element

Claims (2)

[Claims] 1. A first conductor provided close to the negative electrode side of the cold cathode discharge tube and a second conductor provided close to the positive electrode side of the cold cathode discharge tube, wherein: In the discharge starting circuit of the cold cathode discharge tube, wherein a high voltage is supplied to the first conductor and a voltage lower than the voltage supplied to the first conductor is supplied to the second conductor, 2. A discharge starting circuit for a cold cathode discharge tube, wherein the conductor 2 has a shape in which the area decreases from the end portion of the cold cathode discharge tube toward the light emitting central portion. 2. A first conductor provided close to the negative electrode side of the cold cathode discharge tube, and a second conductor provided close to the positive electrode side of the cold cathode discharge tube, wherein: In the discharge starting circuit of the cold cathode discharge tube, wherein a high voltage is supplied to the first conductor and a voltage lower than the voltage supplied to the first conductor is supplied to the second conductor, A discharge starting circuit for a cold cathode discharge tube, wherein one of the two conductors has a shape in which the area decreases from the vicinity of the end portion of the cold cathode discharge tube toward the vicinity of the center of light emission.