JPH09247577A - Video equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a cathode ray tube by using a 1st image quality control signal for a prescribed time after start of power application and selecting a 2nd image quality control signal after the lapse of a prescribed time. SOLUTION: At application of power, when a heater 8 starts power conduction, the heater 8 is heated to warm up a cathode. A cathode voltage based on a video signal 12 is applied to respective cathodes 9, 10, 11 and contrast and brightness image quality adjustment is conducted by changing a pulse from a port of a microcomputer 1 to be applied to circuits 15, 16. The contrast and brightness voltage is set in advance with respect to the elapsed time from power OFF to ON so as to suppress the cathode drive voltage at application of power ON to protect the cathode ray tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video device using a cathode ray tube, and more particularly to a video device having a function of controlling a cathode drive voltage according to a temperature state of a heater of the cathode ray tube.

[0002]

2. Description of the Related Art A video device using a cathode ray tube has a power source O
At the time of N, there is a transfer of the cathode drive voltage. At this point, the temperature of the heater has not yet risen sufficiently and is in a low state, so that the emission material of the cathode is rapidly consumed and the life of the cathode ray tube is shortened. In order to improve this, it is conceivable that a circuit surrounded by a broken line in FIG. 8 is added. This circuit suppresses the transfer of the cathode drive voltage during the rising period and allows the cathode drive voltage to be gently applied.

Another way of thinking is that the cathode drive voltage is not applied to the cathode ray tube by muting the video signal until the heater is warmed up.

[0004]

According to the above-mentioned conventional method, there is a problem that the cost is increased for the addition of the circuit. In addition, regarding a device that mutes a video signal, since no video is displayed during the mute period, the user may mistakenly think that the video signal is defective.

[0005]

In order to solve the above-mentioned problems, the present invention uses a first image quality control signal for a certain period of time after the heater of the cathode ray tube has been energized to use the first cathode. A drive voltage is applied to the cathode of the cathode ray tube, and after a lapse of a certain period of time, switching to the second image quality control is performed to raise the second cathode drive voltage,
The first and second image quality control signals are contrast control signals, and the first and second image quality control signals are
The image quality control signal of is the brightness control signal, and by detecting the temperature of the heater,
A video device for switching between the first image quality control signal and the second image quality control signal.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The video device according to the present invention is powered on.
Sometimes, the contrast control signal and / or the brightness control signal is switched to a preset value so that the cathode drive voltage can be suppressed,
After a certain period of time, the contrast control signal and / or the brightness control signal is switched to a value set by the user or an initial setting value.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the configuration of the present invention will be described. FIG. 1 is a block diagram of an embodiment using a video processing circuit according to the present invention of a television receiver which is one of video devices. The color control signal (color intensity), tint control signal (hue), contrast control signal (video), and brightness control signal (brightness) output from the TV microcomputer 1 are D / A converters 3, 4, 5, 6 Is input to the TV signal processing IC 2 via.

The video signal 12 is input to three ports of the TV signal processing IC 2 for synchronizing signal processing, luminance signal processing and chroma signal processing. The signal input to the luminance signal processing port has a black level correction 13, image quality 14, and contrast 1
5, a video amplifier 16, a pedestal clamp, and a brightness 17 circuit, and a TV signal processing IC
2 is output and is input to the base of the transistor 18. Signal amplified by transistor 18 (-Y)
Is combined with each of RY, G-Y, and B-Y subjected to chroma signal processing, and is input to the red cathode 9, the green cathode 10, and the blue cathode 11 of the cathode ray tube 7, respectively.

Next, the operation will be described. When the power of the television receiver is turned on, the heater 8 starts energizing to generate heat,
The cathode is warmed up. A cathode voltage based on the video signal 12 is applied to the red cathode 9, the green cathode 10, and the blue cathode 11. Here, when the image is a 100% white solid screen, the cathode voltage is
The change in voltage shown in FIG. 6 is the cathode drive voltage. When the image quality adjustment of contrast and brightness is minimum, the amount of change in voltage, that is, the cathode drive voltage is minimum.

The image quality adjustment of the contrast and the brightness is performed by changing the duty ratio of the pulse of the image quality control signal output from the port of the contrast and brightness of the TV microcomputer 1, respectively.
By changing the DC voltage output from the A converter 5.6,
This is performed by applying the contrast 15 inside the V signal processing IC 2 and the circuit of the pedestal clamp and brightness 17.

The main part of the circuit diagram of the contrast 15 is represented by FIG. The voltage output from the D / A converter 5 is applied to the contrast control CV, and when the voltage is increased, the signal current IQ2 of the transistor Q2 is increased.
Becomes larger and the output increases.

Pedestal clamp and brightness 17
The main part of the circuit diagram is shown in FIG. The voltage output from the D / A converter 6 is applied to the brightness controls BV1 and BV2, and when the voltage is increased, the forward bias of Q8 decreases, IQ8 decreases, and Q9 decreases.
The base voltage of the IC decreases and IQ9 decreases. I1 = IQ
Since it is 9-I2, I1 decreases when IQ9 decreases. When I1 decreases, the voltage V1 of the portion connected to the emitter and output of the video amplifier increases. That is, the output level increases.

Next, FIG. 4 showing an embodiment of set values of contrast and brightness according to the present invention will be described. The vertical axis represents the setting values of contrast and brightness, and the horizontal axis represents the elapsed time from power ON.
Both the contrast and brightness setting values are fixed at 0 step (first image quality control signal) from power ON to 3 seconds, and then they are increased by a constant increase amount.
After 6 seconds from N, the value is fixed to the user setting value or the initial setting value (second image quality control signal).

FIG. 5 corresponds to FIG. 4 described above.
The change in the cathode drive voltage with respect to the elapsed time from N is shown. (Video signal is 100% solid white) 50V
Corresponds to the first cathode drive voltage, and 90 V corresponds to the second cathode drive voltage. Further, in the program of the set value as shown in FIG. 4, the program corresponding to the state of the television receiver (for example, by the elapsed time from the power OFF to the power ON) is the RO in the TV microcomputer 1.
M.

Next, FIG. 7, which is an example of a flow chart for setting the contrast and brightness after power-on according to the present invention, will be described. First, when the power is turned on (S1), it is determined whether the elapsed time from power OFF to ON is less than 5 seconds (S2). If it is less than 5 seconds, the set values of the contrast and brightness are It is fixed to the user's set value or the initial set value (S3).

Next, it is judged whether the elapsed time from power OFF to ON is less than 10 seconds (S4), and if it is less than 10 seconds, the set values of contrast and brightness are fixed to 0 step for 1 second. After that, the value is changed by a constant increment, and after 2 seconds, it is fixed to the user's set value or the initial set value (S5). Finally, if the elapsed time from power OFF to ON is 10 seconds or more, after fixing the contrast and brightness set values to 0 steps for 3 seconds,
The value is varied by a fixed increment and fixed to the user's set value or the initial set value after 3 seconds (S6).

Regarding the control by detecting the temperature of the heater, instead of detecting the time after the heater is energized, a thermistor is attached to the CRT substrate connected to the cathode ray tube to increase the cathode temperature of the cathode ray tube. Correspondingly, the temperature of the thermistor on the CRT substrate rises and reaches a constant temperature by comparing the resistance value of the thermistor with the resistance value corresponding to the constant temperature.

[0018]

As described above, according to the present invention, the cathode drive voltage when the power is turned on can be suppressed by controlling the microcomputer, so that the cathode ray tube can be protected at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a video processing circuit according to the present invention.

FIG. 2 is a diagram showing a main part of a circuit diagram of a contrast inside a TV signal processing IC.

FIG. 3 is a diagram showing a main part of a circuit diagram of a pedestal clamp and brightness inside a TV signal processing IC.

FIG. 4 is a diagram showing the setting values of contrast and brightness with respect to the elapsed time since the power was turned on according to the present invention.

5 is a diagram showing a change in cathode drive voltage corresponding to FIG. 4. FIG.

FIG. 6 is a diagram showing changes in cathode voltage due to image quality adjustment.

FIG. 7 is a flowchart for setting contrast and brightness after power-on according to the present invention.

FIG. 8 is a diagram illustrating a main part of a cathode drive voltage swing-in prevention circuit according to a conventional technique.

[Explanation of symbols]

 (1) TV microcomputer (2) TV signal processing IC (5) "Video" D / A converter (6) "Brightness" D / A converter (8) Heater (9) Red cathode (10) Green cathode (11) Blue cathode

Claims (4)

[Claims] 1. A video apparatus using a cathode ray tube, wherein a first cathode drive voltage is applied to the cathode ray tube by using a first image quality control signal for a certain period of time after the heater of the cathode ray tube starts to be energized. In addition to the cathode of the tube, a video device provided with means for switching to a second image quality control signal after a lapse of a certain period of time to raise the voltage to a second cathode drive voltage. 2. The video device according to claim 1, wherein the first and second image quality control signals are contrast control signals. 3. The video device according to claim 1, wherein the first and second image quality control signals are brightness control signals. 4. The image device according to claim 1, wherein the control according to the time according to claim 1 is control by detecting a temperature of a heater of a cathode ray tube.