JPH05234691A - Discharge tube lighting circuit and image display device using this lighting circuit - Google Patents

Abstract

PURPOSE:To correct the dispersion of the characteristics of individual main ballast inductors and discharge tubes, and to display color images with high fidetity. CONSTITUTION:In a discharge tube lighting circuit wherein a main power supply is connected to the anode electrode of an discharge tube 9 via a series circuit comprising main ballast inductors 4, 5 and a switching transistor 8 and a filament power supply is connected to the filament electrode of the discharge tube 9, a variable resistor 14 for correcting dispersions is connected between the switching transistor 8 and the anode electrode of the discharge tube 9. The base of the switching transistor 8 is connected to the connection point of the variable resistor 14 and the anode electrode of the discharge tube 9 via a constant current control transistor 15 and a voltage regulation diode 15 and the base of the constant current control transistor 15 is connected to the connection point of the switching transistor 8 and the variable resistor 14. A control transistor 12 is connected between the base of the switching transistor 8 and the ground and a display switching control signal S2 is input to the base of the control transistor 12 to light the discharge tube 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube lighting circuit for energizing and lighting a discharge tube which constitutes a display element of a large color display panel, and an image display device using this lighting circuit.

[0002]

2. Description of the Related Art A lighting circuit as shown in FIG. 5 is conventionally used to light a discharge tube constituting each light emitting pixel of a large color display panel. In this figure, the commercial AC power supply AC is converted into DC by the rectifier circuit REa, and then the inverter 1A
Is converted to high frequency. The output terminal of the inverter 1A is connected to the primary winding 2a of the transformer 2,
The secondary winding 2b is connected to the main ballast inductors 4 and 5 via the rectifying diodes 6 and 7. The main ballast inductors 4 and 5 are wound so that the directions of the generated magnetic fluxes are complementary to each other, and the other ends of the inductors 4 and 5 are commonly connected and connected to the collector of the switching transistor 8. The emitter of the transistor 8 is connected to the anode electrode of the discharge tube 9 corresponding to each pixel. The output terminal of the inverter 1B to which the direct current from the rectifier circuit REb is supplied is connected to the primary winding 3a of the transformer 3, and the secondary winding 3b of the transformer 3 is connected to the filament electrode (cathode electrode) of the discharge tube 9. To be done. here,
The discharge tubes 9 and the circuit blocks U3 are provided as many as the number of light emitting pixels of the large-sized color display panel, and the display surface of the discharge tubes 9 includes red (R), green (G) and blue (B). A fluorescent film for applying a desired color is coated.

In the discharge tube lighting circuit of this configuration, the switching control signal S2 for video display is input to the base of each switching transistor 8 from the display drive circuit 13 in one frame period T, so that the transistor 8 is turned on / off. Then, each fluorescent film emits light at a gradation corresponding to the RGB image signal S1 by the light of the discharge tube 9 which is turned on when the transistor 8 is turned on, and a color image is displayed on the large color display panel.

[0004]

By the way, the main ballast inductors 4, 5 and the discharge tubes 9 have variations in their characteristics, and in the conventional lighting circuit, the main ballast inductors 4, 5 and the discharge tubes 9 are provided. No means was provided to correct the variation in the characteristics of. Therefore, there is a problem that it is not possible to light each discharge tube 9 so that each fluorescent film of RGB emits light at an appropriate gradation corresponding to the video signal S1.

The present invention has been proposed in order to solve the problems of the prior art as described above, and it is possible to correct variations in characteristics of individual main ballast inductors and discharge tubes, and to faithfully reproduce colors. An object of the present invention is to provide a discharge tube lighting circuit capable of displaying an image and an image display device using the lighting circuit.

[0006]

In order to achieve this object, the present invention connects a main power source to an anode electrode of a discharge tube through a series circuit of a current limiting means and a switching element, and a filament electrode of the discharge tube. In the discharge tube lighting circuit for connecting the filament power supply to the switching element and turning on / off the switching element based on the display switching control signal, between the auxiliary power source and the control terminal of the switching element, or A variable resistor is connected between the control terminal of the switching element and the ground to correct the variation in the characteristics of the current limiting means and the discharge tube to optimize the discharge current, and the switching control is performed between the control terminal of the switching element and the ground. Connect the element and turn on the discharge tube by inputting the switching control signal for display to the control terminal of this switching control element. And it has a configuration.

Further, according to the present invention, the main power source is connected to the anode electrode of the discharge tube through the series circuit of the current limiting means and the switching element, and the filament power source is connected to the filament electrode of the discharge tube to display the switching element. In a discharge tube lighting circuit that lights a discharge tube by turning it on and off based on a switching control signal for use in the discharge tube, a variation in the characteristics of the current limiting means and the discharge tube is provided between the switching element and the anode electrode of the discharge tube. Connect a variable resistor to correct and optimize the discharge current, and connect the control terminal of the switching element to the connection point between the variable resistor and the anode electrode of the discharge tube via the constant current control element and the constant voltage diode. , Connecting the control terminal of the constant current control element to the connection point of the switching element and the variable resistor, and the control terminal of the switching element Connect the switching control element between the earth, and has a configuration for lighting a discharge tube by inputting the display switching control signal to the control terminal of the switching control device.

Further, in the image display device according to the present invention, the discharge tube according to claim 1 or claim 2 is provided for the plurality of discharge tubes constituting the display screen by providing the discharge tube corresponding to the pixels of the display screen. The lighting circuit is provided.

[0009]

According to the above-mentioned structure, since the variation of the characteristics of the current limiting means and the discharge tube can be corrected by the variable resistor for variation correction, the discharge current flowing from the main power source to the discharge tube via the current limiting means and the switching element. Can be optimized and the fidelity of the image displayed on the image display device can be increased.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a discharge tube lighting circuit and an image display device according to the present invention will be described in detail below with reference to the drawings. An example of this discharge tube lighting circuit is shown in the block diagram of FIG. In this figure, the commercial AC power supply 1 is a rectifier circuit RE
The direct current obtained by being connected to a and being rectified and smoothed by the rectifier circuit REa is converted into a high frequency of about 20 kHz by the inverter 1A. The output terminal of the inverter 1A is connected to the primary winding 2a of the transformer 2. The two main ballast inductors 4 and 5 serving as current limiting means are wound so that the directions of magnetic flux generation are complementary to each other so that the switching operation is good, and the transformer that outputs the main power supply of the discharge tube 9 is provided. One end of the secondary winding 2b of No. 2 is connected to the winding start of one main ballast inductor 4 via the rectifying diode 6, and the other end of the secondary winding 2b is connected to the other via the rectifying diode 7. It is connected to the end of the main ballast inductor 5. The winding end of the main ballast inductor 4 and the winding start of the main ballast inductor 5 are commonly connected and connected to the collector of the switching transistor 8 which is a switching element. The emitter of the switching transistor 8 is connected to the anode electrode of the discharge tube 9 provided for each pixel. The output terminal of the inverter 1B supplied with the direct current from the rectifier circuit REb is connected to the primary winding 3a of the transformer 3, and the secondary winding 3b of the transformer 3 is connected to the filament electrode of the discharge tube 9. The intermediate tap of the secondary winding 2b of the transformer 2 is connected to the non-power source side terminal (ground side terminal) of the filament electrode. The plus terminal of the auxiliary DC power supply 10 is connected to the base of the switching transistor 8 via a variable resistor 11 for variation correction. The negative terminal of the DC power source 10 is connected to the non-power source side terminal of the filament electrode. A control transistor 12, which is a switching control element, is connected between the base of the switching transistor 8 and the negative terminal of the DC power supply 10. Variable resistor 11 for variation correction
Is capable of changing the base current of the switching transistor 8 by adjusting the resistance value and adjusting the collector current (discharge current flowing in the main circuit), so that variations in the characteristics of the main ballast inductors 4 and 5 and the discharge tube 9 are caused. It can be set to a resistance value that can be absorbed. In addition,
The variable resistor 11 may be provided in parallel with the control transistor 12. Instead of using the main ballast inductors 4 and 5, resistance ballasts may be used.

In the discharge tube lighting circuit configured as described above, the switching control signal S2 for video display is input from the display drive circuit 13 to the base of the control transistor 12 in one frame period T as shown in FIG. As a result, during the off period Toff of the control transistor 12, the switching transistor 8 is turned on, the current IL flows in the main circuit, and the discharge tube 9 is turned on. In the on period Ton of the control transistor 12, the switching transistor 8 is turned off because the base current is drawn to the transistor 12 side.
The discharge tube 9 does not light up. The variations in the characteristics of the main ballast inductors 4, 5 and the discharge tube 9 are corrected by the variable resistor 11 and the discharge current IL flowing through the discharge tube 9 is set to an appropriate value (see arrow P in FIG. 2). Drive circuit 13
The discharge tube 9 can be turned on with an appropriate brightness corresponding to the video signal S1 input to the.

Next, a discharge tube lighting circuit of another embodiment shown in FIG. 3 will be described. In this figure, the emitter of the switching transistor 8 is connected to the anode electrode of the discharge tube 9 via the variable resistor 14 for variation correction. Between the base of the switching transistor 8 and the anode electrode of the discharge tube 9, a series circuit of a constant current control transistor 15 as a constant current control element and a constant voltage diode 16 is connected. The base of the transistor 15 is connected to the emitter of the switching transistor 8. Transistor 1
5, the constant voltage diode 16 and the variable resistor 14 constitute a constant current circuit, and the variable resistor 14 is set to a value capable of correcting the characteristic variations of the main ballast inductors 4 and 5 and the discharge tube 9. The positive terminal of the auxiliary DC power supply 10 is connected to the base of the switching transistor 8 via the base resistor 17. The negative terminal of the DC power source 10 is connected to the non-power source side terminal of the filament electrode. A control transistor 12 is connected between the base of the switching transistor 8 and the negative terminal of the DC power supply 10.

In the discharge tube lighting circuit configured as described above, the switching control signal S2 for video display is input to the base of the control transistor 12 in one frame period T, so that the switching transistor is turned off during the off period. 8 is turned on and the discharge tube 9 is turned on. At this time, the discharge tube 9 is turned on when the switching transistor 8 is turned on.
When the discharge current IL flowing in the anode electrode of the transistor increases and the voltage drop in the variable resistor 14 increases, the transistor 15 turns on and the base current is drawn into the main circuit side through the transistor 15 and the constant voltage diode 16. The current flowing through the switching transistor 8 is reduced, and a constant current is achieved. By such a constant current operation and the function of the variable resistor 14 for variation correction, the discharge tube 9 can be turned on with an appropriate brightness corresponding to the video signal S1.

Next, an image display device constructed by using the discharge tube lighting circuit shown in FIG. 1 or 3 will be described with reference to FIG. This embodiment is applied to a large-sized color display panel 18, in which each pixel 19 corresponding to RGB is provided with a discharge tube 9 having a front surface coated with a fluorescent film of each color, and each discharge tube 9 includes: The circuit block U1 or U2 shown in FIG. 1 or 3 is connected. The video signal S1 is input to the display drive circuit 13, and the switching control signal S2 for video display from the display drive circuit 13 is input to the control transistor 12, respectively.
A color image based on the image signal S1 is displayed on the display screen 18a of No. 8. The present invention uses not only a lighting circuit using the single-tube monochromatic discharge tube 9 but also a single-tube multicolor type discharge tube in which three anode electrodes corresponding to RGB are enclosed in one discharge tube. It can also be applied to a lighting circuit.

[0015]

As described above, according to the present invention, variations in the characteristics of the main ballast inductor and the discharge tube can be corrected, so that the discharge tube can be lit at an appropriate brightness corresponding to the video signal. There is an effect that a faithful color image can be displayed on an image display device using a lighting circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge tube lighting circuit according to the present invention.

FIG. 2 is an operation waveform diagram of the discharge lamp lighting circuit of FIG.

FIG. 3 is a circuit diagram showing a discharge tube lighting circuit of another embodiment.

FIG. 4 is a diagram showing a schematic configuration of a large color display panel.

FIG. 5 is a circuit diagram showing a conventional discharge tube lighting circuit.

[Explanation of symbols]

 AC Commercial AC power supply REa, REb Rectifier circuit 1A, 1B Inverter 2 Transformer for main power supply 3 Transformer for filament power supply 4, 5 Main ballast inductor 6, 7 Rectifying diode 8 Switching transistor 9 Discharge tube 10 Auxiliary DC power supply 11, 14 Variable resistance for variation correction 12 Control transistor 13 Display drive circuit 15 Constant current control transistor 16 Constant voltage diode 17 Base resistance 18 Large color display panel 18a Display screen 19 pixels

Claims (3)

[Claims] 1. A main power source is connected to an anode electrode of a discharge tube through a series circuit of a current limiting means and a switching element, a filament power source is connected to a filament electrode of the discharge tube, and a switching element is used for display switching control. In a discharge tube lighting circuit that lights a discharge tube by turning it on and off based on a signal, between the auxiliary power source and the control terminal of the switching element, or between the control terminal of the switching element and ground, the current limiting means and Connect a variable resistor to correct the variation in the characteristics of the discharge tube and optimize the discharge current, connect a switching control element between the control terminal of the above switching element and ground, and display it on the control terminal of this switching control element. A discharge tube lighting circuit characterized in that a discharge tube is turned on by inputting a switching control signal. 2. A main power source is connected to an anode electrode of a discharge tube through a series circuit of a current limiting means and a switching element, a filament power source is connected to a filament electrode of this discharge tube, and a switching element is used for display switching control. In a discharge tube lighting circuit that lights a discharge tube by turning it on and off based on a signal, discharge is performed by correcting the variation in the characteristics of the current limiting means and the discharge tube between the switching element and the anode electrode of the discharge tube. Connect a variable resistor to optimize the current and connect the control terminal of the switching element to the connection point between the variable resistor and the anode electrode of the discharge tube via the constant current control element and the constant voltage diode. Connect the control terminal of the current control element to the connection point between the switching element and the variable resistor, and switch between the control terminal of the switching element and ground. Connect the quenching control device, the discharge tube lighting circuit, characterized in that the discharge tube is turned by inputting the display switching control signal to the control terminal of the switching control device. 3. The discharge tube lighting circuit according to claim 1, wherein the discharge tube is provided corresponding to a pixel of a display screen, and the discharge tube lighting circuit according to claim 1 is provided for the plurality of discharge tubes constituting the display screen. Characteristic video display device.