JPH0248880A - Brightness adjustment circuit for television receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brightness adjustment circuit for a television receiver suitable for use in, for example, a color video projector.

[Summary of the invention]

The present invention provides a brightness adjustment circuit for a television receiver suitable for use in, for example, a color video projector.
The input video signal with the reference pulse inserted is supplied to a gain control amplifier using DC control, the reference pulse is extracted from the input video signal output from the gain control amplifier, and the level of this reference pulse is compared with the drive adjustment voltage. A brightness control voltage generation circuit is provided, and the output of the product of this brightness control voltage and the drive adjustment voltage controls the cathode ray tube. By controlling the brightness by changing the electrode potential, an independent gain control amplifier for drive adjustment is not required, and contrast and brightness can be adjusted independently with a simple circuit configuration. At the same time, it is possible to adjust the brightness without hue shift.

[Prior Art] Conventionally, a brightness adjustment circuit as shown in FIG. 2 has been proposed for use in a video projector.

In this FIG. 2, (1) indicates a video signal input terminal, the video signal supplied to this video signal input terminal (1) is supplied to a mixer (2), and a pulse signal input terminal for contrast adjustment is used. (3) Contrast adjustment pulse signal and brightness adjustment pulse signal input terminal (
4) The pulse signals for brightness adjustment supplied to the mixers (
2), the contrast adjustment pulse signal and the brightness adjustment pulse signal are mixed in a predetermined portion of the video signal, for example, during the horizontal blanking period, and this mixed signal is supplied to the gain control amplifier (5), and its output is The video amplifier (6
) to the cathode K of the cathode ray tube (7).

In this case, the output of the gain control amplifier (5) is supplied to the sample and hold circuit (8), and this sample and hold circuit (
8) is sampled and held using a sampling signal with the same timing as the pulse signal supplied to the contrast adjustment pulse signal input terminal (3) from the timing signal input terminal (9), and this sampled and held potential is applied to the comparator. The reference value a, which is supplied to one input terminal of (10) and the reference signal input terminal (11), is input to the comparator (
The comparison output is used to control the gain of a gain control amplifier (5) and adjust the contrast of the image displayed on the cathode ray tube (7).

Also, the magnitude of the beam current can be detected by the video amplifier (6), and this detection signal is sent to the sample and hold circuit (
12), and the sampling signal is sampled at the same timing as the pulse signal supplied to the brightness adjustment pulse signal input terminal (4) from the timing signal input terminal (13), which is supplied to the sample hold circuit (12). This sampled and held potential is then passed through a comparator (14).
) and the reference signal input terminal (5) is supplied to the other terminal of the comparator (14), and this comparison output is used to control the cathode ray tube (7). The beam current is controlled and the brightness of the image displayed on the cathode ray tube (7) is adjusted.

However, in this device, the gain control amplifier (5
), when the contrast is adjusted, the magnitude of the brightness adjustment pulse signal in the output signal naturally changes, so the brightness also changes, making it a complicated operation to have to adjust the brightness again after adjusting the contrast. was needed.

Therefore, in view of the above, the present applicant filed the patent application No. 59-1281.
In No. 14, we proposed a brightness adjustment circuit that allows contrast and brightness to be adjusted independently.

FIG. 3 shows the brightness adjustment circuit of this patent application No. 128114/1982.

In the brightness adjustment circuit shown in FIG. 3, a circuit for obtaining the necessary contrast adjustment pulse signal and brightness adjustment pulse signal is provided in the brightness adjustment circuit shown in FIG. (21) indicates a contrast adjustment signal generation circuit, and a signal of a predetermined potential from this contrast adjustment signal generation circuit (21) is transmitted to a gate circuit (21).
2) and a gate signal at a predetermined timing within the horizontal blanking period of the video signal from the timing signal input terminal (9) is supplied to the gate signal input terminal of this gate circuit (22). A signal of a predetermined level from the contrast adjustment signal generation circuit (21) is gated, and the output side of this gate circuit (22), that is, the contrast adjustment pulse signal input terminal (3) of the mixer (2).
), a contrast l-1 adjustment pulse signal of a predetermined level is obtained.

Further, a signal at a predetermined level from the brightness adjustment signal generation circuit (23) is supplied to a multiplier (24), multiplied by a signal at a predetermined level from the contrast adjustment signal generation circuit (21), and this multiplied signal is applied to the gate circuit (24). 25) and is gated with a gate signal of a predetermined timing that does not overlap with the timing signal, and the output side of this gate circuit (25), that is, the mixer (2
The brightness adjustment pulse signal, which is this multiplication signal, is obtained at the brightness adjustment pulse signal input terminal (4) of ).

The rest of the structure is the same as that in FIG. 2.

According to such a brightness adjustment circuit, contrast and brightness are adjusted using a contrast adjustment pulse signal and a brightness adjustment pulse signal configured to be a constant multiple of this pulse signal, so that when contrast is adjusted, However, the brightness is not affected in any way, and therefore, the contrast and brightness can be adjusted independently and with a simple operation, making it suitable for use in high-quality color display devices and the like.

[Problem to be solved by the invention]

However, in such a conventional brightness adjustment circuit,
Since the brightness pulse signal is affected when contrast is adjusted, a circuit that can correct this is required, which is disadvantageous in that the circuit configuration becomes complicated and color adjustment is complicated.
If the circuit operation is not well-understood, there is often a problem in that the quality achieved varies from person to person.

In view of these points, it is an object of the present invention to provide a brightness adjustment circuit that can independently adjust contrast and brightness with a simple circuit configuration, and can perform brightness adjustment without causing hue shift.

[Means to solve the problem]

In the brightness adjustment circuit of the television receiver of the present invention, for example, as shown in FIG. A reference pulse is extracted from the input video signal output from the input video signal, and a comparator (IOR
), and the comparison output is used as a gain control amplifier (
5R) gain is controlled, and a brightness control voltage generation circuit is provided, and the brightness control is performed by changing the potential of the control electrode of the cathode ray tube with the multiplication output of this brightness control voltage and the drive adjustment voltage. This is what I decided to do.

[Effect]

According to the present invention, contrast adjustment and drive adjustment are performed in the same way as in the conventional example shown in FIG. 2, and brightness adjustment is provided with a brightness control voltage generation circuit, and the brightness control voltage and drive adjustment voltage are Since the brightness is controlled by changing the potential of the control electrode of the cathode ray tube using the multiplication output of Adjustments can be made.

[Embodiment] Hereinafter, an embodiment of the brightness adjustment circuit for a television receiver of the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIGS. 2 and 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this Figure 1, (IR), (IG) and (IB
) are red, green and blue primary color signals 5R9SG and S+, respectively.
This input terminal (IR), (I
The red, green, and blue primary color signals SR+Sa and S supplied to G) and (IB) are mixed by a mixer (2R) and (IB), respectively.
2G) and (2B), and the contrast adjustment pulse signal input terminal (3) is connected to the other end of a contrast adjustment variable resistor (26) whose one end is grounded, and the slider of this variable resistor (26) Mixer (2R), (2
G) and (2B), and mixer (2R) receives the contrast adjustment pulse signal supplied to the contrast adjustment pulse signal input terminal (3) of contrast) 11.

(2G) and (2B), and a contrast adjustment pulse signal is mixed in a predetermined portion of each of the red, green, and blue primary color signals, for example, during the horizontal blanking period.

In addition, the mixer (2R) supplies the red signal SR mixed with the pulse signal for contrast adjustment to the gain control amplifier (5R), and the output is sent to the cathode of the red cathode ray tube (7R) via the video amplifier (6R). It will be supplied to K. In this case, the output signal of the gain control amplifier (5R) is supplied to the sample hold circuit (8R), and the timing signal input terminal (9
Pulse signal input terminal for contrast adjustment from R) (3
) is sampled and held using a sampling signal with the same timing as the pulse signal supplied to Connect the other end of the grounded drive adjustment variable resistor (27R), and connect the slider of this variable resistor (27R) to the comparator (
The reference signal supplied to the reference signal input terminal (IIR) is adjusted to a predetermined value and supplied to the other input terminal of the comparator (IOR), and this comparison output The gain of the gain control amplifier (5R) is controlled to adjust the contrast of the image displayed on the red cathode ray tube (7R).

In addition, the slider of the drive adjustment variable resistor (27R) was connected to one input terminal of a multiplication circuit, for example, a double-balanced multiplication circuit (28R), and one end of the brightness adjustment signal input terminal (29) was grounded. Variable resistor for brightness adjustment (3
0), the slider of this variable resistor (30) is connected to the other input terminal of a multiplication circuit (<28R), and one output terminal of this multiplication circuit (28R) is connected to an operational amplifier. (31R) is connected to the non-inverting input terminal ■, and the other output terminal of the multiplication circuit (28R) is connected to the operational amplifier (31R).
Connect to the inverting input terminal O of this operational amplifier (31R).
The output side of the red cathode ray tube (7R) is connected to the first grid G1 of the red cathode ray tube (7R) via the level shift circuit (32R), and the output of the multiplication of the brightness control voltage and the drive adjustment voltage is used to control the red cathode ray tube (
The potential of the control electrode of 7R) is changed to enable brightness control.

In addition, in this example, the background adjustment signal input terminal (33R) is connected to one end of a resistor (34R), and the other end of this resistor (34R) is connected to the other output terminal of the multiplication circuit (28R) and the operational amplifier. (31R) is connected to the connection midpoint with the inverting input terminal θ, and this connection midpoint is grounded via a background adjustment variable resistor (35R) to enable background adjustment.

Further, the green signal system (36G) and the blue signal system (36B) are configured to have the same circuits as the mixer (2G) and the following red signal system circuit (36R).

Further, in this example, a feedback clamp circuit (37R) is added to each of the red, green, and blue signal systems to keep the black level constant.

According to this embodiment, contrast adjustment and drive adjustment are performed in the same way as in the conventional example shown in FIG.
For brightness adjustment, a brightness control voltage generation circuit is provided, and the output of the product of this brightness control voltage and the drive adjustment voltage is used to change the potential of the control electrode of the cathode ray tube to perform brightness control. Since it became independent,
The advantage of this method is that it eliminates the need for an independent gain control amplifier for drive adjustment, allows contrast, brightness, and background to be adjusted independently with a simple circuit configuration, and allows brightness adjustment to be performed without causing hue shift. be.

In the above-described embodiments, the case where the present invention is applied to a color video projector has been described, but it goes without saying that the present invention can also be applied to a reverse color television receiver.

Further, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, contrast adjustment and drive adjustment are performed in the same way as in the conventional example, and brightness adjustment is provided with a brightness control voltage generation circuit, and the output of the product of this brightness control voltage and drive adjustment voltage is used to control the cathode ray tube. Since the brightness is controlled by changing the potential of the control electrode of the control electrode, there is no need for a separate gain control amplifier for drive adjustment, and contrast and brightness can be adjusted independently with a simple circuit configuration, and hue shift can be controlled. There is an advantage that brightness adjustment can be performed without causing a problem.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the brightness adjustment circuit of the television receiver of the present invention, Fig. 2 is a block diagram showing an example of a conventional example, and Fig. 3 is a block diagram showing another example of the conventional example. It is. (IR), (IG) and (IB) are respectively red lights,
Green signal and blue signal input terminals, (2R), (2
G) and (2B) are mixers respectively, (3) is a pulse signal input terminal for contrast adjustment, (5R) is a gain control amplifier, (7R), (7G) and (7B) are red, green and blue cathode rays, respectively. tube, (8R) is a sample hold circuit, (IOR) is a comparator, (IIR) is a signal input terminal for drive adjustment, (27R) is a variable resistor for drive adjustment,
(28R) is a multiplication circuit, (29) is a signal input terminal for brightness adjustment, (30) is a variable resistor for brightness adjustment, (36R)
, (36G) and (36B) are red signal systems respectively. These are green signal system and blue signal system circuits.

Claims (1)

[Claims] The input video signal into which the reference pulse has been inserted is supplied to a gain control amplifier using DC control, the reference pulse is extracted from the input video signal output from the gain control amplifier, and the level of this reference pulse and the drive adjustment voltage are calculated. are compared in level by a comparator, and the gain of the gain control amplifier is controlled by the comparison output, and a brightness control voltage generation circuit is provided to output the product of the brightness control voltage and the drive adjustment voltage. 1. A brightness adjustment circuit for a television receiver, characterized in that the brightness is controlled by changing the potential of a control electrode of a cathode ray tube.