JPS6119197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in projection television receivers.

FIG. 1 shows an overview of a conventional projection television receiver. In the figure, 1 indicates the main body of the projection television receiver, which includes a projection cathode ray tube 2, a deflection yoke 3, etc. ing. 4 is a screen placed opposite to the main body 1, on which an image from the projection type cathode ray tube 2 is projected;
An image of a predetermined size will be reproduced.

By the way, such a projection television receiver is usually configured so that the image is reproduced to fill the entire screen 4. Therefore, when the number of viewers is small and they are viewed close to the screen 4, the raster image is It was so large that it became an eyesore. Also, if you simply reduce the size of the image,
The fluorescent surface of the cathode ray tube 2 would be burnt by the beam current, significantly shortening the life of the cathode ray tube 2.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a projection television receiver in which the raster width is reduced, the raster is less obtrusive, and the brightness is maintained approximately constant. be.

FIG. 2, which is an embodiment of the present invention, will be explained below. In the figure, 5 is a horizontal deflection circuit, including a linearity coil 5a, deflection coils 5b, 5c, and 5 for deflecting red, blue, and green electron beams, respectively.
d and a width coil 5e, by which a normal deflection operation is performed. 6a and 6b are horizontal width correction coils, and 6c and 6d are impedance correction coils. Coils 6a and 6b are deflection coils 5b,
5c and 5d in parallel, and the coil 6
c and 6d are connected in series to the width coil e.
7a connects the coils 6a and 6b to the deflection coils 5b and 5.
c, relay switch for connecting to 5d, 7
b, 7c, and 7d are coils 6b, 6c, and 6, respectively.
This is a relay switch for shorting d. Also,
8 indicates a vertical oscillation circuit, in which an oscillation transistor 8
A vertical width adjustment volume 8b inserted into the collector circuit of a, a vertical linearity adjustment volume 8c inserted between the collector and emitter, and vertical width correction volume 8d, 8e inserted in parallel with the vertical width adjustment volume 8b. These components can adjust the bias of the transistor 8a and set the electron beam to a predetermined vertical width. 20 is a part of the video circuit, which is composed of a bias resistor 21, a sub-contrast volume 22, a contrast volume 23, resistors 24 and 25 for contrast adjustment, etc. By adjusting the bias, it is possible to adjust the screen size. The contrast can be changed accordingly. 10,
Reference numerals 11, 12, 13, 14, and 15 are interlocking switches for energizing the relay coils, and are configured to switch terminals a, b, and c in conjunction with each other.

Under such a configuration, the switches 10, 1
1, 12, 13, 14, and 15 are connected to terminal a, relay switch 7a is turned off, relay switches 7b, 7c, and 7d are turned on, and only deflection coils 5b, 5c, and 5d and width coil 5e are operated. The electron beam is deflected over the entire width of the screen 4. In addition, the regulators 8b and 8d are inserted in parallel to the collector circuit of the transistor 8a, and at this time, the regulators 8b and 8d are set so that the vertical deflection width is the full vertical width of the screen 4. Therefore, the image will be reproduced to fill the screen 4. Next, when switches 10, 11, 12, 13, 14, and 15 are switched to terminal b, relay switches 7a and 7c are turned on, relay switches 7b and 7d are turned off, and coil 6
a, 6b are connected in parallel to the deflection coils 5b, 5c, 5d, and the coil 6d is connected in series to the width coil 5e. Therefore, the horizontal deflection width by the deflection coils 5b, 5c, and 5d decreases, and the volume 8e becomes smaller than the volume 8.
Screen 4 is to be inserted in parallel to b.
The image will be played back at a reduced size compared to the screen size. In addition, by selecting the contrast adjustment resistor 24 in advance, it is possible to set the brightness to the same level as in the case of a large screen size. In other words, the beam current is reduced, making it possible to reduce burning of the fluorescent surface.

Furthermore, when switching to terminal c, relay switches 7a and 7b are turned on and relay switches 7c and 7d are turned off, and coil 6b, which was inserted in parallel to deflection coils 5b, 5c and 5d, is short-circuited and the coil 6c and 6d are inserted in series to the width coil 5e. Also, the volume 8
d and 8e are separated from the collector circuit of transistor 8a, and the collector resistance increases. Therefore, it is possible to reproduce an image that is further reduced in size compared to the image size when connected to terminal b. Further, the switch 15 is switched to the terminal c, and the contrast adjustment resistor 25 is connected to the terminal c, so that the beam current can be further reduced and the image can be reproduced with substantially the same brightness.

Here, impedance correction coils 6c and 6d
By adjusting the impedance at the horizontal deflection yoke, the impedance at the horizontal deflection yoke can be kept constant, thereby stabilizing the flyback pulse and preventing deterioration of focus caused by changes in high voltage.

In addition, in the above embodiment, the image size is set to 3.
Although it is configured to switch in two stages, it may be configured to switch in two stages, or it may be configured to control the horizontal oscillation circuit and the vertical deflection circuit instead of the horizontal deflection circuit 5 and the vertical oscillation circuit 8. Good too.

As explained above, this invention is configured to switch between multiple stroke sizes and keep the brightness constant, making it possible to reduce the eyesore of raster images and also reduce damage to the cathode ray tube. , this invention has great practical value.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional projection type television receiver, and FIG. 2 is a connection diagram showing the main structure of a television receiver according to an embodiment of the present invention. In the figure, 1 is the projection television receiver body, 3
is a deflection yoke, 4 is a screen, 5 is a horizontal deflection circuit, 5b, 5c, 5d are deflection coils, 5e is a width coil, 6a, 6b are horizontal width correction coils, 6c, 6
d is an impedance correction coil, 7a, 7b, 7
c, 7d are relay switches, 8 is a vertical oscillation circuit,
8b, 8c, 8d are vertical width adjustment volumes, 20
is a part of the video circuit, 24 and 25 are contrast setting resistors, 10, 11, 12, 13, 14, 15
is an interlocking switch.

Claims (1)

[Claims] 1. A television receiver main body that houses a projection type cathode ray tube, a screen that is placed apart from the main body and that reproduces images from the projection type cathode ray tube, and a deflection width switching means that switches the electron beam deflection width in the projection type cathode ray tube. and a beam current switching means for switching the beam current of the projection type cathode ray tube, and switching the image to be reproduced on the screen to a plurality of sizes,
In the beam current changing according to each size, the deflection width switching means includes a width correction coil that can be connected in parallel to the deflection coil and an impedance correction coil that can be connected in series to the deflection coil. a deflection circuit including a coil;
and an oscillation circuit including a width correction volume that can be connected in parallel to a width adjustment volume inserted in the collector circuit of the oscillation transistor, and when the width correction coil is connected in parallel to the deflection coil. The projection television receiver is characterized in that the impedance correction coil is connected in series to the deflection coil.