JPH01307795A - Input signal switching method for cathode-ray tube display device - Google Patents

Abstract

PURPOSE:To prevent the quality of an image plane from deteriorating and circuit components from breaking or deteriorating by applying a blank signal to a video circuit and a power source prior to the switching of a switch. CONSTITUTION:The video circuit 1 and power source 7 are applied with the blank signal to lower the output voltages V1 and V7 of the video circuit 1 and power source 7 and the switch 5 such as a relay is switched during the period. Then operation for returning the output voltages V1 and V7 to normal voltages is performed after a horizontal width coil and a resonance capacitor are so selected as to obtain the best L and C (where L and C are the sum of the inductance of a horizontal deflecting coil and a horizontal width coil in a horizontal deflecting circuit 6 and the sum of the capacitance of a resonance capacitor). Consequently, a decrease in picture quality such as variation in image plane size and the breakage and deterioration of circuit components are prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cathode ray tube display device (multiscan cathode ray tube) that displays a video signal whose horizontal sweep frequency changes.
The present invention relates to an input signal switching method.

[Prior Art] FIG. 3 is a block diagram showing the configuration of an example of the conventional technology, in which 1 is a video circuit, and 2 is a cathode ray tube (hereinafter abbreviated as CRT).

3 is an f/V conversion circuit that changes the output voltage V according to the horizontal sweep frequency fh; 4 is a voltage detection circuit that detects when the output voltage V of this circuit 3 has reached a predetermined level voltage Va; 5 is a horizontal A switch such as a relay for switching between the resonant capacitor and the horizontal width coil in the deflection circuit 6, and 7 a power source.

In FIG. 3, the horizontal sweep frequency fh is equal to t in FIG.

At this point, when fl changes to f2 as shown in Fig. 2(b), the output voltage V of the f/V conversion circuit 3, (Fig. 2(
C)) changes according to the horizontal sweep frequency fh during the time t2 to t1 in Figure 2, and when it reaches a certain level voltage v0, the voltage detection circuit 4 operates for the time t to t5 in Figure 2. , the output voltage L (see FIG. 2(d)) is input, and the switch 5 such as a relay in the horizontal deflection circuit 6 is activated at t3 in FIG.
It switches in ~t4 hours.

Here, in order to suppress large changes in screen size and brightness in a multi-scan CRT, the output voltage Vb of the horizontal deflection circuit 6 is kept constant even if the horizontal sweep frequency fh changes. The output voltage V is expressed by the following equation (1).

(1) where fh is the horizontal sweep frequency, Tr is the retrace time, and V is the output voltage of the power supply 7.

Tr is expressed by the following equation (2).

Tr= πJ ``Bi ・・・・・・・・・・・・
・・・・・・(2) However, L and C are horizontal deflection circuit 6
is the sum of the inductances of the horizontal deflection coil and the horizontal width coil within, and the sum of the capacitances of the resonant capacitor.

Therefore, in order to keep the output voltage v6 constant even if the horizontal sweep frequency fh changes (from formula 11, Tr-Jh= a (a is a constant)...
(3) The horizontal width coil and the resonant capacitor are selected in advance so that the optimum beam C corresponding to the horizontal sweep frequency fh is satisfied so that the equation (3) holds true.

In this way, in the conventional example, the horizontal deflection circuit output voltage V is kept constant by switching the horizontal width coil and the resonant capacitor with the switch 5 such as a relay so that the optimum slope C corresponding to the horizontal sweep frequency h+ is obtained. I kept it.

[Problem to be solved by the invention]

However, in the above conventional example, the horizontal sweep frequency fh is 1, as is clear from the time chart in FIG.
．． It changes at the point in time, and the switching of switch 5 such as a relay is 14
Therefore, the output voltage V becomes unstable during the period from t to t4, resulting in deterioration of image quality such as image distortion and changes in screen size, as well as destruction and deterioration of circuit components. There was an issue.

[Means to solve the problem]

In cathode ray tube display devices, the horizontal sweep frequency f
The problem of deterioration of screen quality and destruction and deterioration of circuit components that occur when h changes is solved by controlling the horizontal deflection circuit output voltage v6 and the video circuit output voltage V, -.

That is, in the method of the present invention, a blank signal S is applied to the video circuit 1 and the power supply 7, and the output voltages V, , V of the video circuit 1 and the power supply 7 are changed.
, and in the meantime, switch 5 such as a relay, select the horizontal width coil and resonant capacitor to obtain the optimum glue, C, and then output voltage L, V? The device is configured to perform an operation to return the voltage to the normal voltage.

[For production]

A blank signal is supplied to the video circuit 1 and the power supply 7, which has enough time for the switching of the switch 5 such as a relay to end (time t1 to t3 in FIG. 2) after the horizontal sweep frequency fh changes from fl to f2. When S (see Fig. 2 (a)) is applied from the outside, during that period (time t0 to t6 in Fig. 2), the video circuit output voltage v1 reaches the black level (m 1' in Fig. 2). The image will go down and become invisible.

Further, the power supply voltage V, decreases to V,' (see FIG. 2 (illustration)), and the horizontal deflection circuit output voltage V, can be sufficiently lowered.

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the method of the present invention.

In FIG. 1, 1 is a video circuit that manually amplifies a video signal v0 and outputs a video signal voltage V, and 2 is a cathode ray tube that receives the output voltage v1 of this circuit 2 and displays the video signal. 3 is an f-conversion circuit that inputs the horizontal sweep frequency fh and outputs the change in the horizontal sweep frequency fh as a change in the output voltage V; 4 is the output voltage V of this circuit 3, which has reached a predetermined level voltage Va. This is a voltage detection circuit that detects this.

6 is a horizontal deflection circuit which inputs the output voltage v4 of this circuit 4 and outputs a constant voltage V to the cathode ray tube 2 by switching between a resonant capacitor and a horizontal width coil by a switch 5 such as a relay; 7 is a horizontal deflection circuit 6 This is a power supply that supplies an output voltage V to .

In the method of the present invention, in such a cathode ray tube display device, the video circuit 1 and the power supply 7 are connected to each other before switching the switch 5.
A blank signal S is applied to the video circuit 1 to lower the output voltage (2) of the video circuit 1 and the voltage v7 of the power source 7, the screen is erased, and the switch 5 is switched.

That is, when the horizontal sweep frequency fh is about to change from f to f2, a blank signal S is applied from the outside to the video circuit 1 and the power supply 7 at time t0 in FIG. 2 in advance.

As a result, the video circuit output voltage V is at the black level (v+')
(see FIG. 2(f)), and the image on the CRT 2 becomes invisible. In addition, the power supply voltage V, also v,
The horizontal deflection circuit output voltage v6 is also sufficiently lowered. Then f/
V conversion circuit 3, voltage detection circuit 4, switch 5 for relay etc.
t and t in FIG. 2 operate in the same manner as before.

time), the switching of switch 5 such as a relay is completed, and f/
After the V conversion circuit output voltage v3 stabilizes, the blank signal S is released (at time 8 in Figure 2), and the horizontal sweep frequency f
Obtain an image corresponding to 2.

〔Effect of the invention〕

As described above, according to the present invention, by applying the blank signal S to the video circuit 1 and the power supply 7 before switching the switch 5, the video circuit output voltage V is set to the black level (V+'').
At the same time, the power supply voltage V,
It is possible to lower the horizontal deflection circuit output voltage V by lowering the horizontal deflection circuit output voltage V, which not only prevents deterioration of screen quality such as image disturbance and screen size fluctuation when switching the horizontal sweep frequency fh, but also reduces the horizontal deflection circuit output voltage V. It is possible to prevent destruction and deterioration of circuit components due to instability of V.

The above effect is particularly effective when video signals having different horizontal sweep frequencies are frequently switched.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 fa) to (gl are time charts for explaining the present invention in detail, and FIG. 3 shows a conventional example. It is a block diagram. 1... Image B path, 2... Cathode ray tube (C
RT), 3...f/V conversion circuit, 4...
... Voltage detection circuit, 5 ... Switch (such as a relay), 6 ... Horizontal deflection circuit, 7 ... Power supply.

Claims (1)

[Claims] A video circuit 1 that inputs the video signal V_0 and outputs the video signal voltage V_1, a cathode ray tube 2 that inputs the output voltage V_1 of this circuit 1 and displays the video signal, and a horizontal sweep frequency fh that inputs the video signal and outputs the video signal voltage V_1. The change in fh is expressed as the output voltage V_
3, a voltage detection circuit 4 that detects that the output voltage V_3 of this circuit 3 has reached a predetermined level voltage Va, and the output voltage V_4 of this circuit 4 is input. A cathode ray tube display device including a horizontal deflection circuit 6 that outputs a constant voltage V_6 to a cathode ray tube 2 by switching between a resonant capacitor and a horizontal width coil using a switch 5, and a power supply 7 that supplies an output voltage V_7 to the horizontal deflection circuit 6. , before switching the switch 5, a blank signal S is applied to the video circuit 1 and the power supply 7 to lower the output voltage V_1 of the video circuit 1 and the voltage V_7 of the power supply 7,
An input signal switching method for a cathode ray tube display device configured to switch the switch 5 by erasing the screen.