JPH0391315A - Switching circuit for horizontal oscillation circuit - Google Patents

Abstract

PURPOSE:To prevent oscillation from being interrupted when a switch contact is changed over by off-biasing an on-biased transistor(TR), which is connected between one contact of a switching circuit and a power source, when the other contact is turned on, CONSTITUTION:When contacts 3 and 4 of a switching circuit 2 are changed over, an oscillation frequency from an IC 10 for horizontal oscillation is switched corresponding to the frequency of a horizontal synchronizing signal. Between this contact 3 and a power supply line 11, an on-biased TR 14 is connected and when the contact 3 is switched to the 4, the TR 14 is off-biased by a diode 16 for off-bias, etc. The power supply for oscillation under the switch of the contacts 3 and 4 is secured by a capacitor 9 and while the switch contacts are changed over, the interruption of the oscillation is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching circuit for a horizontal oscillation circuit of a display monitor having a horizontal frequency of 2 or more, which switches the horizontal frequency according to the frequency of a horizontal synchronizing signal.

[Conventional technology]

FIG. 2 shows a conventional switching circuit for this type of horizontal oscillation circuit. In the figure, ■ is a transistor to which a switching signal is applied, 2 is a relay, RC is an excitation coil of relay 2, 3.4 is a contact of relay 2, 5.6 is a volume for first and second horizontal oscillation, 7 .8 is a resistor, 9 is a horizontal oscillation capacitor, 10 is a horizontal oscillation IC (oscillation control circuit), 11 is a power supply, and 12 is a switching signal.

In this configuration, when the relay 2 is switched to the contact 3 side, the capacitor 9 is charged through the volume 5 and the resistor 7, and when the relay 2 is switched to the contact 4 side,
Charged through volume 6 and resistor 8, horizontal oscillation I
Cl0 performs oscillation control. The switching control of the relay 2 is performed by turning on and off the excitation coil RC using the transistor 1.

[Problem to be solved by the invention]

In this conventional switching circuit, the switch of relay 2 is connected to contact 3.
There was a problem in that it took several milliseconds from the time the capacitor 9 left until it came into contact with the contact 4, and during this time there was no charging path to the capacitor 9, and the oscillation operation stopped during that time.

This invention was made to solve the above problem.
It is an object of the present invention to provide a switching circuit for a horizontal oscillation circuit that can prevent the oscillation operation from stopping during switching.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a 1-transistor which is connected to an on-bias between one contact of a switching circuit and a power supply, and which is connected to the other contact and which biases the transistor off when the other contact is closed. The circuit is equipped with a circuit that performs the following steps.

[Effect]

In this invention, since the one contact side and the power supply are short-circuited by the transistor, even if the changeover switch leaves the one contact, a charging path to the oscillation capacitor is secured. Then, when the other contact is switched, the transistor is turned off.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 14 is a transistor, and the power supply 1
The diode 13 is inserted between the contact 1 and the contact 3, and its -\- source is connected to the voltage dividing point of the voltage dividing resistors 15 and 17. Further, the contact 4 is connected to the voltage dividing point via a diode 16. The other configurations are the same as those shown in FIG.

In this configuration, when the relay 2 is currently switched to the contact 3 side, the transistors 1 to 14 are on-biased and conductive. At this time, the capacitor 9 is repeatedly charged and discharged by the volume 5, the resistor 7, and the horizontal oscillation required TCIO, and horizontal oscillation is performed at the first oscillation frequency. Even when the frequency of the horizontal synchronizing signal changes and the switch of relay 2 moves away from contact 3, charging current is supplied to capacitor 9 through transistor 14. When the switch of the switching circuit 2 contacts the contact 4, an off bias is applied to the transistor 14 through the diode 16, and the transistor 14 is turned off. Therefore, the capacitor 9 is charged through the volume 6 and the resistor 8, and the IC required for horizontal oscillation is
l0 will oscillate at the second oscillation frequency. When the switching circuit 2 switches from the contact 4 to the contact 3, when the switch leaves the contact 4, the transistor 14 is biased on, so that the capacitor 9 is charged through the transistor 14, the volume 5, and the resistor 7.

In this way, in this embodiment, the switch contacts are short-circuited until the switch is completely switched from one contact to another, and once the switch is completely switched, the short-circuited state is released and the switch is closed. As soon as the contact is separated from the above-mentioned contact point, the fallen state is immediately recovered, so there is no interruption of oscillation due to switching.

〔Effect of the invention〕

As explained above, this invention secures a charging path even while the switch changes from one contact to another, making it possible to prevent oscillation interruption during this time. Therefore, the above effects can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional switching circuit. In the figure, ■...-transistor, 2-switching circuit, 3
．． 4-switch, 5.6-volume, 7.8-resistance,
9-capacitor, 10-horizontal oscillation IC111-power supply,
14- transistor, 16 diode. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In the switching circuit of the horizontal oscillation circuit of a display monitor that switches the oscillation frequency according to the frequency of the horizontal synchronizing signal, a transistor is inserted between one contact and the power supply and given an on bias, and a transistor connected to the other contact and given an on bias. A switching circuit for a horizontal oscillation circuit, comprising a circuit that turns off and biases the transistor when the other contact is closed.