JPS5832382Y2 - Color television receiver switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for switching to a state for adjusting the cut-off level of a color cathode ray tube of a color television receiver.

Conventionally, when adjusting the cutoff level of the three guns of a color cathode ray tube, in order to make the beam current equivalent to zero, the vertical deflection operation is stopped, the raster of the screen is turned horizontally, and the video signal is turned off. I stopped it and adjusted the screen voltage.

FIG. 1 shows an example of a conventional switching device, and this circuit will first be explained.

In FIG. 1, 1 is a video amplification circuit of a color television receiver, 2 is a video amplification circuit, and 3 is a video amplification circuit that adjusts the required video signal size to a color cathode ray tube 7.
Add video signal to.

On the other hand, regarding vertical deflection, the vertical synchronization circuit 4 generates a vertical pulse or a vertical sawtooth wave in synchronization with the vertical synchronization signal, the vertical output circuit 5 amplifies the power, and the deflection yoke 6
In addition to this, it also performs vertical deflection.

Now, when adjusting the cutoff of the cathode ray tube 7, the video signal, and the output of the video amplifier circuit 2, are connected to the service switch 8.
By turning the switch to the S side, no video signal is applied to the cathode ray tube 7, and regarding vertical deflection, the service switch 8 is turned to the S side to prevent the signal from being applied to the vertical output circuit, thereby stopping the deflection. ing.

In the case of the conventional device, as is clear from Fig. 1, first,
Lead wires 9, 10, 11.12 to service switch 8
4 wires have to be wired, which takes time in the wiring process, and the cost increases due to the need for many wires.In addition, service switches are not installed on the chassis in consideration of serviceability in the market. Since it is installed at the rear of the switch, it requires long lead wires, which may cause interference or interference.Furthermore, the switch 8 needs to have two circuits and two contacts, which is expensive. be.

Therefore, the present invention aims to eliminate such drawbacks, reduce the number of wires, reduce the number of work hours, cause less disturbance and interference, and provide a switching device that can use inexpensive switches. An example will be described with reference to the drawings.

FIG. 2 shows an embodiment of the present invention.

The same numbers as in FIG. 1 represent the same functions, so the same numbers are given and the explanation will be omitted.

In FIG. 2, 13 is a synchronization separation circuit, and 14 is an integration circuit. A vertical synchronization signal is obtained from the output terminal of this integration circuit.

26 inside the dotted line is a commonly used vertical oscillation circuit, and assuming that the service switch 25 is switched to connect the ground side of the capacitor 22 to the ground,
When the vertical synchronization signal passes through the capacitor 15 and is applied to the base of the switching element transistor 18, the transistor 18 becomes conductive, which causes the other switching element PNP) transistor 19 to also become conductive, and the capacitor 18 is charged at a high speed, and the emitter of transistor 18 instantly rises to voltage B.

When the vertical synchronization signal period ends in this state, the transistor 18
The emitter voltage becomes higher than the base voltage of the transistors 18 and 19, and the transistors 18 and 19 are cut off.

Therefore, the charge charged in the capacitor 22 is transferred to the resistor 2.
1 and starts discharging at a constant time constant, and a sawtooth wave voltage for vertical deflection is output from one end of the resistor 21.

When this voltage drops to a level lower than the base voltage of transistor 18, transistors 18 and 19 automatically conduct again and charge capacitor 22, resulting in a self-oscillating operation.

If a time constant is set so that the next vertical synchronizing signal is applied and the transistors 18 and 19 become conductive before the voltage becomes lower than the base voltage, a sawtooth voltage is generated in synchronization with the vertical synchronizing signal.

As described above, the vertical oscillation circuit whose self-excited oscillation frequency is determined by the capacitor 22, the resistor 21, the base voltage of the transistor 18, etc. is synchronously controlled by the vertical synchronization signal, and a vertical sawtooth wave is applied to the vertical output circuit 5.

Now, during normal operation, when the service switch 25 is set to the N side, the ground side terminal of the capacitor 22 of the vertical oscillation circuit 26 is grounded, forming the above-mentioned oscillation circuit.

Since the S side of the service switch 25 to which the video signal line is connected is open, the video signal is directly applied to the color cathode ray tube 7.

Next, when adjusting the cutoff level of the color cathode ray tube 7, turn the service switch 25 to the S side.

Then, the video signal line is grounded, one end of the capacitor 22 of the vertical oscillation circuit 26 is opened, the vertical oscillation circuit 26 is no longer formed, the vertical sawtooth wave is not applied to the vertical output circuit 5, and therefore no deflection current flows. Screen is horizontal
becomes.

As described above, according to the switching device of the present invention, the lead wire is
Only two 3.24 wires are required, and the service switch is also one-circuit type, which makes wiring work easier, the service switch is also inexpensive, and there is no need to route many lead wires, so that's all. It is less susceptible to external interference, and its practical value is great.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional switching device for a color television receiver, and FIG. 2 is a circuit diagram of a switching device for a color television receiver according to an embodiment of the present invention. 2... Video amplifier circuit, 3... Video output circuit, 7... Cathode ray tube, 26...
... Vertical oscillation circuit, 25 ... Service switch, 22 ... Condenser, 21 ... Resistor, 23゜24 ... Lead wire.

Claims (1)

[Scope of utility model registration request] One end of a switching element that is switched by a vertical synchronization signal is connected to a power supply, and a parallel circuit of a resistor and a capacitor is connected between the other end and ground to oscillate a sawtooth wave voltage for vertical deflection. An oscillation circuit is provided,
Switching of a color television receiver equipped with a service switch that selectively connects one terminal on the ground side of the capacitor and the video signal line that supplies video signals to the color cathode ray tube to the ground. Device.