JPS60223271A - Luminance controller - Google Patents

Abstract

PURPOSE:To improve the visual properties of a display by varying the DC bias according to the selection of a video signal and the external light quantity. CONSTITUTION:A video/chroma demodulation circuit 2 reproduces RGBY signals 3-6 from a video signal 1 and supplies them to a switch circuit 7. While other RGB signals 10-12 are also supplied to the circuit 7 via an amplifier circuit together with a signal 23 given from a DC reproduction circuit. Then these signals supplied to the circuit 7 are sent to a CRT9 via a video drive circuit 8. A switch signal 17 is used to perform switching between two signals. The luminance is controlled by varying the DC biases 18 and 19 according to the change of a resistance R1 and a resistance R9 serving as an external photosensor. While these biases 18 and 19 are also varied by the signal 17 and selected at optimum levels according to the video signal. In such a way, the visual properties of the CRT9 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to color television receivers, monitor televisions, CR
The present invention relates to a brightness adjustment device used in T-display devices and the like.

Conventional configurations and their problems In recent years, CRTs have been recognized for their expressive capabilities, resolution, and visibility, and are being used not only as television receivers but also as teletext receivers, personal computer terminals, and even game terminals. It has come to be widely used. This application ranges from general household use to moving means of transportation.

This indicates that devices that were conventionally used only for reproducing one video signal are now becoming multipurpose devices that can reproduce multiple video signals.

In other words, it has become more necessary than ever to adjust the brightness depending on the use, fatigue, and visibility, and it has become necessary to solve this problem.

A conventional example of the brightness adjustment device shown in FIG. 1 is shown.

In the figure, 1 is a video signal such as a television signal or a video signal. From this, the video/chroma demodulation circuit 2
, G, B, Y signals are regenerated, and the analog switch circuit 7
added to.

On the other hand, R from a computer or text multiplex signal receiver,
G, B signals 10, 11, 12 (hereinafter referred to as TxR).

(abbreviated as TxG and TxB) are the respective amplifier circuits 13° and 14
．． 15 and is applied to one side of the analog switch 7. Since each tax signal is input only at the exchange meeting, the DC regeneration circuit 16 generates a DC signal, and each amplifier 13, 14.
Offset the DC component to 5. The switching signal 17 controls the switching of the analog switch 7, and is generally a logic 'Hn
(high level).

It is indicated by "L" (low level). The signal selected by the analog switch 7 passes through the video drive circuit 8 to the C
It is added to RT9 and displayed as a video.

In this device, the brightness adjustment is artificially performed by a variable resistor R1, and the variable DC component obtained thereby passes through the line 18 on one side and the line 19 on the other side, and the DC offset of the video/chroma demodulation circuit 2 and The brightness is changed by changing the DC offset of the DC regeneration circuit 16.

However, in this device, since the amplification degree and DC regeneration amount of the two amplification systems (i.e., 2 and 13.14.16) are different, when controlled by the DC bias obtained by variable resistor R1, both amplification systems The disadvantage is that the CRT 9 does not have the same brightness in the system, and that the variable resistor R1 must be constantly adjusted in response to changes in the ambient light of the environment in which it is used.

Purpose of the Invention The present invention solves the above-mentioned problems, and enables the selection of multiple video signals and the ability to respond to changes in the surrounding environment, and to maintain optimal brightness for display visibility. It provides a device that responds.

Structure of the Invention The present invention has the following features: 1. Different DC bias voltages are applied to the second amplification system so that the brightness of the CRT does not change depending on the signal selection. Furthermore, in the present invention, the brightness is automatically changed in response to changes in ambient light, thereby improving visibility.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 to 17 shown in the figure are the same as in the conventional example. This device includes a first amplification system including a video/chroma demodulation circuit 2, amplification circuits 13 to 16, and a DC regeneration circuit 16.
A different DC bias is applied to each amplifier system via lines 18 and 19, so that the brightness of the CRT does not change even depending on the selection of the video signal. There is.

A control switching signal 17 for selecting a video signal turns on/off the transistor Q1. R1 is a variable resistor for brightness adjustment. When transistor Q1 is off, the bias applied to the base of transistor 02 is determined by variable resistor R1. The base voltage of this transistor Q2 is impedance-converted and output to the resistor R4, and the resistor R7
and R8. The divided DC bias is a line,
18 and is applied to the video/chroma demodulation circuit 2.

On the other hand, a DC bias divided by resistors R6 and R6 is applied to the amplifier circuits 13, 14.15 and the DC regeneration circuit 16 via a line 19. Resistors R7, R8 and R6°R6 are resistors for matching the DC amplification degrees of the two amplification systems.

The resistor R9 is a sensor (for example, a silicon photodiode) using external light, and supplies the base potential of the transistor Q3 by R1°/R9. By controlling the base potential of the transistor Q3, the DC impedance from the collector to the emitter of the transistor Q3 is changed, and the potentials of the line 18 and the line 19 are controlled in accordance with external light, thereby changing the brightness.

A similar result can be obtained by using a switch instead of a sensor for this resistor R9. In this case, transistor Q3 operates as a switching transistor, and when transistor Q3 is off, the potential of line 18.19 is directly applied to the Emink potential of transistor Q2, and transistor Q
3 is on, the potential on lines 18 and 19 is divided and applied by R7/R8 and R5/R6.

When the control switching signal 17 is l+Hn, the transistor Q1 is turned on, and the voltage divided by the resistors R1 and R3 is applied to the base of the transistor Q2.

This means that the DC amplification degree of the two signal amplification systems is R7/R8,
Even if R5/R6 are made to match, the amount of DC regeneration is still different, so both are made to match.

In this way, it is possible to respond to changes in brightness due to the environment and to unify brightness by selecting a plurality of signals.

Effects of the Invention As described above, according to the present invention, it is possible to match the DC amplification degrees of the two amplification systems, and also to match the DC regeneration amount, so that the CRT can be used even though the input signals are different. It can always be driven to the same brightness. In addition, the brightness can be automatically changed depending on the ambient light, making it very convenient in practice.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional brightness adjustment device, and FIG. 2 is a circuit diagram of a brightness adjustment device according to an embodiment of the present invention. 2...Video chroma demodulation circuit, 7...Switch, 8...Drive circuit, 9...Cathode ray tube,
13゜14.15...Amplifier circuit, Ql, Q2・
...Transistor, R5, R6, R7, R8...
...divider resistance. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] A transistor Q2 that changes the DC bias of a circuit that reproduces multiple signals in a display device using a CRT.
, brightness adjustment volume R1, R7/R8゜R6/R that divides the emitter voltage output to R4, and R9 whose resistance value changes depending on the environmental light or 0N depending on the amount of external light.
A switch that turns 10FF, Q3 that receives the potential and changes the DC impedance, and a control switching signal that turns 0N.
In series with Ql that controls 10FF and R1 that controls the base potential of 02.