JP3046898B2 - Cathode ray tube display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube display device.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a part of a conventional cathode ray tube display device, and FIG. 3 is a waveform diagram showing an operation at the time of an abnormality. 3, 1 is a screen voltage control circuit, 2 a high voltage output circuit, 3 of G ₁ voltage control circuit, 4 is a flyback transformer, 7 the cathode ray tube, 15 denotes a focus block.

The operation of the thus constructed cathode ray tube display device will be described below.

[0004] First, is supplied G ₂ voltage from the screen voltage control circuit 1 in the cathode ray tube 7, G ₁ voltage is supplied from the G ₁ the voltage control circuit 3. A high voltage and a focus voltage are supplied from the flyback transformer 4.

[0005]

When a high voltage is discharged by a minute foreign substance or the like in the cathode ray tube 7, abnormal leakage to the focus electrodes G _3-1 and G _3-2 may occur depending on the structure of the cathode ray tube 7. Current may flow. When such a leak current starts to flow, the resistance of the focus block 15 is extremely high, and as shown in FIG. 3, there is a problem that the focus voltage is extremely lowered, the state is maintained, and the state does not return. . At this time, the display is turned off because the focus voltage is extremely low.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and it is possible to automatically return a decrease in focus voltage caused when a high voltage is discharged to an original voltage by using any cathode ray tube. A tube display device is provided.

[0007]

[Means for Solving the Problems] Claim1The cathode ray tube described
The display device is normal for the focus electrode of the cathode ray tube.
Focus block to apply
Of the focus blocknormalLower than focus voltage
Low impedance power supplyVoltageDiode for backflow prevention
ThroughLow impedance power supply applied to focus electrode
And a voltage circuit.

[0008]

[Action] Claim1CRT display device as describedBy
If the focus electrode is lower than the normal focus voltage
Use a diode to prevent backflow of the low impedance power supply voltage.
Applied throughBy doingDuring normal operation, a backflow prevention
Iode is in cut-off state and focus at this time
The normal focus voltage of the block is printed on the focus electrode.
Be added. However, due to abnormalities, the focus electrode
Focus voltage is below the low impedance power supply voltage
When the value falls to
A low-impedance power supply voltage
It will be applied to the focus electrode. As a result,
At times,Focus voltageIs low impedancePower supply
The pressure drops belowButBlockingIsYou. As a result,
The flow converges and the focus voltage returns to a steady state.

[0009]

EXAMPLES For real施例the cathode ray tube display device of the present invention will be described with reference to FIGS. 1 and 4.

[0010] In FIG. 1, 1 is a screen voltage control circuit, 2 a high voltage output circuit, of G ₁ voltage control circuit 3, 4 is a flyback transformer, 7 is a cathode ray tube, 8 low impedance
Reference numeral 15 denotes a focus block.
From the low impedance power supply voltage circuit 8, the focus
The poles G _3-1 and G _3-2 have low input voltages lower than the normal focus voltage.
When the impedance power supply voltage is
17 is applied.

A cathode ray tube display having the above configuration
In the apparatus, since under normal conditions a low impedance power supply voltage of the low-impedance power supply voltage circuit 8 is set lower than the normal focus <br/> scan voltage, the diode 16,
Reference numeral 17 denotes a cutoff state. For this purpose,
Normal focus voltage of focus block 15
Applied to the ground electrode.

When an abnormality such as a high voltage discharge occurs, the output voltage of the low impedance power supply voltage circuit 8 is supplied to the focus electrodes G _3-1 and G _3-2 via the diodes 16 and 17. Therefore, depending on the structure of the cathode ray tube 7, the
Large leak current flows through the focus electrodes G _3-1 and G _3-2
Even, without reducing the focus voltage is below the low-impedance power supply voltage, the focusing electrode G _3-1, G
_The leak current flowing through _3-2 converges and the focus voltage returns to a steady state.

The reason is that the focus electrode
Focus voltage applied to G _3-1 and G _3-2 is low impedance
When the voltage drops below the power supply voltage, the diode 1
6 and 17 are conducting and low impedance power supply voltage circuit 8
The low impedance power supply voltage is the focus electrode G _3-1 ,
This is because the voltage is applied to G _3-2 .

[0014]

【The invention's effect】 A cathode ray tube display device according to claim 1.
According to the configuration, the focus electrodeFor backflow preventiondiode
Supplying low impedance power supply voltage via
The focus voltage drops below the impedance power supply voltage
Never. as a resultThe leakage current converges
Cas voltage isCorrectReturn to normal state.

As described above, it is possible to automatically recover from a decrease in the focus voltage when an abnormality such as high voltage discharge occurs.

[Brief description of the drawings]

1 is a circuit diagram of a real施例the cathode ray tube display device of the present invention.

FIG. 2 is a circuit diagram of a conventional cathode ray tube display device.
You.

FIG. 3 is a diagram showing the state of the cathode ray tube display device of FIG .
It is a waveform diagram of an focus voltage.

FIG. 4 is a diagram illustrating an operation of the cathode ray tube display device shown in FIG .
FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 screen voltage control circuit 2 high voltage output circuit 3 G ₁ voltage control circuit 4 flyback transformer 7 cathode ray tube 8 low impedance power supply voltage circuit 15 focus block

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G09G 1/00 H04N 5/68

Claims (1)

(57) [Claims] 1. A focus block for applying a normal focus voltage to a focus electrode of the cathode ray tube, lower low-in than the normal focus voltage of the focus block
Cathode ray tube display device that includes a low impedance power supply voltage circuit for applying a impedance supply voltage to <br/> the focus electrode through a diode for preventing reverse flow.