JPH0879563A - Luminance control circuit - Google Patents

Abstract

PURPOSE: To reduce luminance control adjustment man-hours in a plant and to supply video signals holding stable luminance. CONSTITUTION: A reference signal generator 8 generates reference signals for supplying the video signals holding the stable luminance and eliminating the adjustment of the luminance. A timing pulse generator 7 decides the output timing of the reference signals. A mixing circuit 6 inserts the reference signals to the video signals by timing pulses and the reference signals are detected from the signals of a cathode driving circuit 4 in a detector 9. The detected signals are DC converted in an integrator 10 and compared with the voltage of the output of the reference signal generator 8 in a comparator 11, the output is fed back to an adjustment device 3 and the luminance is held fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal brightness control circuit for a television receiver, a commercial monitor receiver and the like.

[0002]

2. Description of the Related Art A brightness control circuit for a video signal in a conventional television receiver or a commercial monitor receiver will be described below.

A conventional brightness control circuit of this type is constructed as shown in FIG. In FIG. 4, 1 is a signal input unit for inputting a video signal, 2 is a brightness adjusting unit for adjusting the brightness level so as to be within a predetermined value within a certain range, 2a is a brightness adjusting volume for factory adjustment, and 3 is brightness. Adjuster for adjustment, 3a for brightness adjustment volume for user, 4 for CR
A cathode drive circuit 5 for driving the cathode of T is a CRT for displaying a video signal.

The operation of the brightness control circuit will be described below. First, a video signal is input from the signal input unit 1, the brightness is adjusted by the brightness adjusting unit 2 and the adjuster 3, and is output to the cathode ray tube 5 through the cathode drive circuit 4. To adjust the brightness of the video signal, the brightness adjustment section 2 is adjusted by the brightness adjustment volume 2a for factory adjustment so that the cathode drive circuit 4 has a specified brightness level. The user adjusts the brightness of the received video signal by changing the brightness adjustment volume 3a for the user of the adjuster 3 for the video signal adjusted here.

[0005]

However, in the conventional brightness control circuit having such a structure, fluctuations in the brightness of the video signal due to variations in the components of each circuit system also fluctuate due to the adjustment of the brightness adjustment volume for factory adjustment. Therefore, there is a problem that the man-hours for adjusting the brightness control in the factory are indispensable.

The present invention solves the above-mentioned problems of the prior art, and provides a brightness control circuit for reducing the number of man-hours for brightness control adjustment in a factory and supplying a video signal which maintains stable brightness for a long period of time. With the goal.

[0007]

In order to achieve this object, the present invention provides a reference signal generator for generating a reference signal for brightness control, and a timing pulse generator for determining the output timing of the reference signal. A controller that adjusts the brightness of the video signal through a mixing circuit that inserts the reference signal into the video signal, a detector that detects the reference signal from a cathode drive circuit that drives the cathode of the CRT, An integrator for converting the signal detected by the detector into DC and a comparator for comparing the voltage of the signal integrated by the integrator with the voltage output from the reference signal generator are provided, and the output of the comparator is The brightness of the video signal is kept constant by feeding back to the brightness control terminal of the adjuster.

Further, a reference signal generator for generating a reference signal for controlling brightness, a timing pulse generator for determining an output timing of the reference signal, and a mixing circuit for inserting the reference signal into a video signal are passed through. An adjuster for adjusting the brightness of the video signal, a detector for detecting the reference signal from a cathode drive circuit for driving a cathode of a CRT, and a sample and hold capacitor for sampling and holding the signal detected by the detector. A comparator for comparing the voltage of the sampled and held signal with the voltage output by the reference signal generator, and feeding back the output of the comparator to the brightness control terminal of the adjuster The brightness is kept constant.

[0009]

According to the above construction, the detected reference signal is DC-converted by the integrator and the voltage of the output of the reference signal generator is compared by the comparator, and the output has a constant luminance of the video signal. Since the feedback is made to the adjuster as described above, the fluctuation of the brightness in the mixing circuit, the adjuster and the cathode drive circuit is absorbed.

Further, by using the sample-holding capacitor instead of the integrator, the voltage to be compared becomes a pulse voltage from the DC-converted voltage by the integrator, and a voltage higher than the DC-converted voltage can be obtained.

[0011]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 shows an overall configuration diagram of a brightness control circuit according to a first embodiment of the present invention.

In FIG. 1, 1 is a signal input section to which a video signal is input, 3 is an adjuster for adjusting the brightness of the video signal, 3
a is a brightness adjusting volume for the user, 4 is a cathode drive circuit for driving the cathode of the CRT, 5 is a CRT for displaying a video signal, 6 is a mixing circuit for mixing the input video signal and a reference signal, and 7 is a reference signal , A reference signal generator for generating a reference signal, 9 a detector for detecting the reference signal in the cathode drive circuit 4, and 10 a signal detected by the detector 9. An integrator 11 for DC conversion is a comparator for comparing the voltage detected by the detector 9 and further DC converted by the integrator 10 with the voltage of the output of the reference signal generator 8. Further, FIG. 2 is a diagram showing each waveform of the video signal, the reference signal, and the timing pulse.

The operation of the brightness control circuit configured as described above will be described. First, a video signal (FIG. 2A) is input from the signal input unit 1. This video signal is a timing pulse (FIG. 2 (b)) output from the timing pulse generator 7 in the mixing circuit 6, and is mixed with the reference signal (FIG. 2 (c)) output from the reference signal generator 8. It Then, the mixed waveform (FIG. 2D) of the video signal and the reference signal whose brightness is adjusted by the adjuster 3 and the cathode drive circuit 4 is output to the CRT 5. Here, the reference signal is detected by the detector 9.
The detected reference signal (FIG. 2E) is DC converted by the integrator 10 and compared with the voltage of the output of the reference signal generator 8 by the comparator 11. The brightness is kept constant by feeding back the output of the comparator 11 to the brightness adjustment terminal of the adjuster 3. Further, similarly to the conventional example, the brightness of the video signal to be received can be adjusted according to the preference of the user by changing the brightness adjustment volume 3a for the user of the adjuster 3.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. In FIG. 3, those having the same operation and effect as those described in FIG. 1 of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The difference from the configuration of FIG. 1 is that the integrator 10 is a sample-hold capacitor 12. With the circuit configuration as described above, the detected reference signal is DC by the integrator 10.
Since the converted voltage becomes a pulse voltage and becomes higher than the DC converted voltage, the comparator 11 is less likely to cause a comparison error.

[0015]

As described above, according to the present invention,
By using the brightness control circuit, the integrated reference signal compares the DC-converted voltage of the integrator with the output voltage of the reference signal generator, and adjusts the output so that the brightness of the video signal becomes constant. Since it is fed back to, the fluctuation of brightness in the mixing circuit, the adjuster, and the cathode drive circuit is absorbed, and the man-hour for brightness control adjustment can be reduced,
It is possible to supply a video signal with stable luminance for a long period of time.

Further, by using a sample-hold capacitor instead of the integrator, a pulse error voltage higher than the voltage converted from the detected reference signal by the integrator is obtained. It is difficult to cause this, and the number of steps for adjusting the brightness is reduced, so that it is possible to supply a video signal having a stable brightness for a long period of time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a brightness control circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a video signal, a reference signal, and a timing pulse waveform in the brightness control circuit according to the first embodiment of the present invention.

FIG. 3 is an overall configuration diagram showing a brightness control circuit according to a second embodiment of the present invention.

FIG. 4 is an overall configuration diagram showing a conventional brightness control circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal input part, 2 ... Brightness adjustment part, 2a ... Brightness adjustment volume for factory adjustment, 3 ... Adjuster, 3a ... Brightness adjustment volume for user, 4 ... Cathode drive circuit, 5 ... CRT, 6 ... Mixing circuit , 7 ... timing pulse generator, 8 ... reference signal generator, 9 ... detector, 10 ... integrator, 11 ... comparator, 12 ... sample and hold capacitor.

Claims (2)

[Claims] 1. A reference signal generator for generating a reference signal for controlling brightness, a timing pulse generator for determining an output timing of the reference signal, and a mixing circuit for inserting the reference signal into a video signal. An adjuster that adjusts the brightness of the video signal, a detector that detects the reference signal from a cathode drive circuit that drives a cathode of a CRT, an integrator that performs DC conversion on the signal detected by the detector, A comparator for comparing the voltage output from the reference signal generator with the voltage of the signal integrated by the integrator, and feeding back the output of the comparator to the brightness control terminal of the adjuster A brightness control circuit characterized in that the brightness is kept constant. 2. A reference signal generator for generating a reference signal for controlling brightness, a timing pulse generator for determining an output timing of the reference signal, and a mixing circuit for inserting the reference signal into a video signal. An adjuster for adjusting the brightness of the video signal, a detector for detecting the reference signal from a cathode drive circuit for driving a cathode of a CRT, and a sample and hold capacitor for sampling and holding the signal detected by the detector. A comparator for comparing the voltage of the sampled and held signal with the voltage output by the reference signal generator, and feeding back the output of the comparator to the brightness control terminal of the adjuster A brightness control circuit characterized in that the brightness is kept constant.