JPH0138628Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a screen display size switching circuit that can be adapted to a video monitor or a character display by using the same screen display device.

(b) Prior Art In general, in a video monitor, the screen amplitude is adjusted to be slightly wider (overscan) using the video signal as a reference, just like a television receiver, in order to connect a video camera.

On the other hand, in recent years, character displays for displaying text information symbols (including graphics and symbol information symbols) used in personal computers and computer terminals have been adjusted to be narrow (underneath) so that the displayed characters and graphics can be sufficiently displayed. Sukyan)
ing.

Therefore, if you try to display both on one display device, if you adjust to overscan, there will be parts of the displayed characters and figures that are not displayed.
On the other hand, if the adjustment is made to underscan, the periphery of the image based on the image signal becomes blank, resulting in deterioration of the characteristics of the display device.

(c) Purpose of the invention This invention uses an appropriate switching circuit to change the screen display size by appropriately switching between images based on video signals as a video monitor and characters and figures based on text information signals (including graphics and symbol information signals) as a character display. The purpose is to switch.

(d) Structure of the invention The present invention provides a screen display device comprising a vertical deflection circuit and a horizontal deflection circuit, each of which is connected to a deflection coil provided on a cathode ray tube, in which a vertical amplitude adjustment device connected to the vertical deflection circuit is provided. a voltage dividing circuit is connected to the horizontal deflection circuit, a tap terminal is provided on the horizontal amplitude adjustment coil connected to the horizontal deflection circuit, and the voltage dividing circuit and the tap terminal are connected to a changeover switch;
The configuration is such that the screen display size is changed by switching the switch.

(E) Embodiment The drawings relate to the screen display size switching circuit of the present invention. FIG. 1 is an embodiment of the circuit, and FIGS. 2A and 2B are perspective views of an embodiment of the horizontal amplitude adjustment coil used in the circuit. Figures and electrical equivalent drawings are shown.

Next, the present invention will be explained according to the drawings. 1 is a DC power supply terminal, 2 is a vertical deflection circuit including a waveform shaping circuit 3, a vertical synchronization separation circuit 4, a vertical oscillation circuit 5 and a vertical output circuit 6, and 7 is a vertical deflection circuit. Deflection coil, 8 a variable resistor for vertical linearity adjustment, 9 a variable resistor for vertical amplitude adjustment, 10 a voltage divider circuit having resistors 11 and 12, 13 a synchronous separation output terminal, 14
is a horizontal deflection circuit, 15 is a horizontal deflection coil, 16 is a horizontal linearity adjustment coil, 17 is a horizontal amplitude adjustment coil, 18 is a tap terminal, 19 and 20 are terminals at both ends, 21 is a changeover switch, and 22 is for vertical deflection.
Indicates IC.

Next, the operation of the screen display size switching circuit of the present invention will be explained. First, when configured as a video monitor, the switching switch 21 is
B and A'-B' are set in a short-circuited state.

One end of the variable resistor 9 for vertical amplitude adjustment connected to the vertical deflection circuit 2 is connected to the voltage dividing circuit 1 because both ends of the resistor 12 of the voltage dividing circuit 10 are short-circuited.
The resistance value of 0 is small, so the vertical amplitude is set large.

The tap terminal of the horizontal amplitude adjustment coil 17 connected to the horizontal deflection circuit 14 and the terminal 18 are short-circuited, the inductance value becomes small, and the horizontal amplitude is set large, which is compatible with the vertical amplitude being set large. In addition, the vertical deflection coil 7 and the horizontal deflection coil 15
Deflection currents corresponding to overscan flow through, and the screen display size on a cathode ray tube (not shown) becomes large.

On the other hand, the changeover switch 21 is set to A-C and A'-.
When switched to the C' side, the resistors 11 and 1 of the voltage divider circuit 10
2 is connected in series to one end of the variable resistance ceramic 9, and the vertical amplitude becomes small.

Since the tap terminal 18 and terminal 19 of the horizontal amplitude adjustment coil 17 connected to the horizontal deflection circuit 14 are open, the inductance value becomes large and the horizontal amplitude becomes small, so that the vertical amplitude is set to a small value. Coupled with this, each deflection current corresponding to underscan flows through the vertical deflection coil 7 and the horizontal deflection coil 15, and the screen display size becomes small.

Figure 2 shows an example in which the horizontal amplitude adjustment coil 17 is provided with terminals 19 and 20 at both ends and a tap terminal 18 as an intermediate tap.If one terminal is added to the coil, which is usually called a width coil, good. In this case, as mentioned above, the terminal 19,
The inductance value between the tap terminal 18 and the terminal 20 is set to the value at the time of under-scanning.

(f) Effects of the invention According to the invention, in a screen display device that is shared as a video monitor and a character display, overscan (for the video monitor) and underscan (for the character display) can be changed by switching the changeover switch. The circuit of the present invention has an extremely simple configuration and is useful for screen display devices.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the screen display size switching circuit of the present invention, and FIG. 2 shows a horizontal amplitude adjustment coil used in the circuit. Explanation of main figure numbers, 2... Vertical deflection circuit, 7...
Vertical deflection coil, 9... Variable resistor for vertical amplitude adjustment, 10... Voltage divider circuit, 14... Horizontal deflection circuit, 15... Horizontal deflection coil, 17... Horizontal amplitude adjustment coil, 18... Intermediate tap terminal.

Claims (1)

[Scope of utility model registration request] In a screen display device comprising a vertical deflection circuit and a horizontal deflection circuit, and in which the deflection circuit is connected to a deflection coil provided on a cathode ray tube, a voltage divider circuit comprising a plurality of resistors is provided as a vertical amplitude adjustment means connected to the vertical deflection circuit. A horizontal amplitude adjusting coil connected to the horizontal deflection circuit is provided with a tap terminal, and the voltage dividing circuit and the tap terminal are connected to a changeover switch that operates in conjunction with each other, and by switching the switch, the screen display size can be changed. A screen display size switching circuit characterized by switching the screen display size.