JP2535613B2 - Degaussing circuit of television receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degaussing circuit for degaussing a cathode ray tube of a television receiver, and more particularly to a degaussing circuit having a function of removing noise such as dimmer noise.

Prior Art FIG. 3 shows an example of a conventional degaussing circuit.

In the figure, reference numeral 11 is a three-terminal module consisting of a positive temperature coefficient thermistor 9 and a heating element 10 thermally coupled to the positive temperature coefficient thermistor 9, and a series circuit of the positive temperature coefficient thermistor 9 and the degaussing coil 12 and the heating element. Each of 10 is connected to an AC power source. Reference numeral 13 denotes a positive characteristic thermistor, which is connected in parallel with the positive characteristic thermistor 9 in the series circuit of the positive characteristic thermistor 13 and the manual degaussing switch 14. 15 is the above degaussing coil
This is a noise removal capacitor that is installed in parallel with 12.

Therefore, when an AC power source is applied to the circuit, a large AC current flows through the degaussing coil 12 because the resistance value of the positive temperature coefficient thermistor 9 is small at first. Since the positive temperature coefficient thermistor 9 generates heat with the lapse of time and its resistance value increases, the alternating current decreases, and the current becomes minute in a state where heat generation is stable, and the degaussing operation ends. When the manual degaussing switch 14 is pressed in this state, the positive temperature coefficient thermistor 13 is connected to the degaussing coil 12 in series, and a large alternating current flows through the degaussing coil 12 at first, and the positive temperature coefficient thermistor 13 generates heat with the passage of time. As the resistance value increases, the current decreases and the manual degaussing operation is performed. When noise occurs in the power supply circuit, it is bypassed by the capacitor 15 to reduce the influence of noise of the degaussing coil 12.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional degaussing circuit, since the resistance value of the positive temperature coefficient thermistor becomes a considerably high value at the end of the degaussing operation, when high frequency noise such as dimmer noise is superimposed on the AC power supply. The capacitor 15 cannot sufficiently remove this noise. Therefore, noise is applied across the degaussing coil,
There are problems that the beam current of the cathode ray tube is deflected to generate horizontal noise on the screen, and noise is induced in another inductance electromagnetically coupled to the degaussing coil.
In order to solve this, a method of providing a negative characteristic thermistor between both ends of the degaussing coil and damping the degaussing coil can be considered.However, when a manual degaussing circuit is attached to this, the negative characteristic is observed in the steady operation state of the television receiver body. There is a problem that the resistance value of the thermistor is so small that the degaussing effect cannot be fully exerted.

Means for Solving the Problems In order to solve the above problems, the present invention provides a degaussing coil and a first PTC thermistor in series with an AC power supply,
A heating element thermally coupled to the positive temperature coefficient thermistor is connected to the alternating current, a negative temperature coefficient thermistor is provided in parallel with the degaussing coil via a break contact of a relay, and the negative temperature coefficient thermistor is connected in parallel with the first positive temperature coefficient thermistor. A second positive temperature coefficient thermistor is provided through a make contact of the relay, and a first state in which the break contact is connected and a second state in which the make contact is connected.
A manual degaussing switch capable of selectively selecting a state is provided, and the manual degaussing switch is configured to switch from the first state to the second state.

Therefore, when the television receiver is turned on, the first
By the positive characteristic thermistor, the degaussing coil is supplied with an alternating current that is gradually attenuated with the lapse of time to perform the degaussing operation.
In the steady operation state of the television receiver, the resistance value of the negative characteristic thermistor connected in parallel with the degaussing coil is kept low, so even if noise such as dimmer noise occurs in the power supply circuit, this The negative characteristic thermistor bypasses the noise to prevent the noise from being guided to the degaussing coil. To perform degaussing manually, press the degaussing switch to switch the relay contacts. As a result, the negative characteristic thermistor is disconnected from the circuit, the second positive characteristic thermistor is connected in series with the degaussing coil, and the demagnetization by manual operation is performed by the second positive characteristic thermistor.

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

In the figure, reference numeral 3 denotes a three-terminal module consisting of a positive temperature coefficient thermistor 1 and a heat generating element 2 thermally coupled to the positive temperature coefficient thermistor 1, and a series circuit of the positive temperature coefficient thermistor 1 and the degaussing coil 4 and the heat generating element. 2 are connected to an AC power source, respectively. Reference numeral 5 is a positive temperature coefficient thermistor, and a series circuit of the positive temperature coefficient thermistor 5 and a common contact 6a and a make contact 6b of the relay 6 is provided in parallel with the positive temperature coefficient thermistor 1.
Reference numeral 7 denotes a negative characteristic thermistor, and a series circuit of the negative characteristic thermistor 7 and a common contact 6a and a break contact 6c of the relay 6 is provided in parallel with the degaussing coil 4. Reference numeral 8 denotes a non-locking manual degaussing switch, which is configured so that the + B power source is connected to the drive winding of the relay 6 when the manual degaussing switch 8 is closed.

FIG. 2 shows the temperature-resistance characteristics of the positive characteristic thermistors 1 and 5 and the negative characteristic thermistor 7.

Therefore, when the power of the television receiver is turned on, the resistance of the positive temperature coefficient thermistor 1 is small at first and the degaussing coil 4
A large alternating current flows through the positive characteristic thermistor 1 over time, and its resistance increases due to the heat generation of the positive temperature coefficient thermistor 1. Therefore, the current is gradually attenuated and the degaussing operation is performed when the power is turned on.

Now, when the manual degaussing switch 8 is in the open state, the common contact 6a and the break contact 6c of the relay 6 are connected, and the negative characteristic thermistor 7 is connected in parallel with the degaussing coil 4. The resistance value of the negative characteristic thermistor 7 gradually decreases as shown in FIG. 2 as the temperature of the surrounding parts rises, such as the temperature rise of the surrounding parts, thereby damping the degaussing coil 4 with a low resistance. Therefore, even if noise such as dimmer noise is superimposed on the power supply circuit after the end of the deactivating operation when the power is turned on, this noise is damped by the negative characteristic thermistor 7 and induces noise to the degaussing coil 4. To prevent horizontal noise from being generated on the screen.

In order to manually perform the degaussing operation in the steady operation state of the television receiver, first, the manual degaussing switch 8 is closed. When the manual degaussing switch 8 is closed, current is supplied to the drive winding of the relay 6, and the common point 6a of the relay 6 is switched from the break contact 6c to the make contact 6b.
A positive temperature coefficient thermistor 5 is connected between the degaussing coil 4 and the AC power supply. As a result, the degaussing operation at the time of manual operation is performed in the same manner as in the case of the positive temperature coefficient thermistor 1.

EFFECTS OF THE INVENTION Since the present invention has the above-described configuration, since the degaussing coil can be damped by the negative characteristic thermistor after the automatic degaussing when the power supply to the set is finished, the degaussing coil is superimposed on the AC power supply. It is possible to remove noise such as dimmer noise between both ends of the degaussing coil, and to prevent horizontal noise from being generated on the screen. Further, during the manual degaussing operation, the negative characteristic thermistor, which has a low resistance, is disconnected from the circuit, so that it is possible to operate without degrading the degaussing effect.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an operation explanatory diagram thereof, and FIG. 3 is a block diagram of a conventional example. 1,5 …… Positive characteristic thermistor, 2 …… Heating element, 4 …… Degaussing coil, 6 …… Relay, 6b …… Make contact, 6c …… Break contact, 7 …… Negative characteristic thermistor, 8 …… Manual demagnetization switch.

Claims (1)

(57) [Claims] 1. A degaussing coil wound around a cathode ray tube of a television receiver and a first PTC thermistor are provided in series with an AC power supply, and a heating element thermally coupled to the first PTC thermistor is provided. A negative characteristic thermistor is provided in parallel with the degaussing coil via a break contact of a relay connected to the AC power source, and a second positive characteristic thermistor is provided in parallel with the first positive characteristic thermistor via the relay and a make contact. And a manual degaussing switch capable of selectively selecting a first state in which the break contact is connected and a second state in which the make contact is connected, and the manual degaussing switch allows the manual degaussing switch from the first state to the second state. The degaussing circuit of the television receiver that can be switched to the state.