JPH04112584U - Demagnetization control circuit - Google Patents

Abstract

(57) [Summary] [Purpose] The present invention provides a degaussing control circuit that can perform automatic degaussing immediately after power-on and manual degaussing using a degaussing switch without causing any delay time when performing degaussing using direct current. The purpose is to provide. [Structure] The present invention charges a capacitor 1 with the DC power supply voltage Vcc, and when the switch transistor 15 is turned on, the charging power of the capacitor 1 is used to flow a current to the degaussing coil 5 to demagnetize the surface of the cathode ray tube. In doing so, a first time constant circuit that controls the charging time of the capacitor 1 is provided.
19, a second time constant circuit 9 for controlling the demagnetizing operation time of the degaussing coil 5, and a transistor 20 connected as an emitter follower.
A time constant circuit 19 is connected, and the connection point of resistors 21 and 22 connected in series between the emitter of this transistor 20 and the ground is connected to the base of the switching transistor 15, and the connection point of these resistors 21 and 22 is connected to the base of the switching transistor 15. The second time constant circuit 9 is connected through a transistor 14 to the second time constant circuit 9.

Description

[Detailed explanation of the idea]

[Purpose of invention]

0001

[Industrial application field]

This invention is used to demagnetize the surface of cathode ray tubes in television receivers, display monitors, etc. The present invention relates to a degaussing control circuit for performing degaussing.

0002

[Conventional technology]

Degaussing circuits used in display monitors etc. automatically degauss when the power is turned on. Both the function of degaussing and the function of degaussing when the degaussing switch is pressed manually are available. There are many things that we have. This degaussing circuit typically consists of a degaussing coil connected to the AC power input. A circuit consisting of a positive thermistor and a positive thermistor is opened and closed by a relay to perform demagnetization control. There is.

0003 FIG. 2 shows a conventionally known degaussing control circuit. In this diagram, the power switch is turned on. When the AC power supply 30 is turned on, the regulator connected to the diode bridge 31 A secondary DC voltage EB is generated from the regulator 32. This secondary side voltage EB is resistor 33, This switch transistor is divided by 34 and added to transistor 35. 35 is turned on and relay 36 is closed. As a result, the degaussing circuit connected to the AC power supply 30 A degaussing current flows through the coil 37 and the positive thermistor 38, and the degaussing coil 37 Automatic demagnetization of the tube surface takes place.

0004 A few seconds after degaussing begins, the time constant circuit consisting of resistor 39 and capacitor 40 41, the voltage across the capacitor 40 gradually increases, turning on the transistor 42, and Since the switching transistor 35 is turned off, the degaussing operation is stopped.

[0005] Also, when the degaussing switch 43 is pressed, the charge stored in the capacitor 40 is discharged. As a result, transistor 42 turns off and switch transistor 35 turns on. Then, the relay 36 closes and a manual degaussing operation is started. After a few seconds, the resistance is 39 and The transistor 42 is turned on again with a time constant determined by the capacitor 40, so the demagnetization Production stops.

[0006]

[Problem that the idea aims to solve]

By the way, in the degaussing control circuit using alternating current described above, control is performed using one time constant circuit 41. However, in the case of a degaussing control circuit that uses DC, the capacitor is charged using DC. Since this discharge current must be passed through the degaussing coil to demagnetize it, this discharge current must be applied immediately after the power is turned on. Another time constant circuit is required to ensure charging time to the capacitor.

[0007] When using two time constant circuits in this way, the degaussing coil capacitor The time constant circuit that controls charging time is influenced by the time constant circuit that controls demagnetization time. If this is not done, there will be a delay in the charging time of the capacitor each time a demagnetizing operation is performed. become.

[0008] This invention was proposed to solve these problems, and it uses direct current. Automatic degaussing immediately after power-on without any delay time Provides a degaussing control circuit that can perform degaussing and manual degaussing using a degaussing switch. The porpose is to do. [Structure of the idea]

[0009]

[Means to solve the problem]

To achieve this objective, the degaussing control circuit according to the present invention uses a first DC power source. A first capacitor that is charged with Degaussing coil supplied via switching means including a switching transistor and a second capacitor connected between the second DC power supply and the reference potential point. A constant circuit and a third capacitor connected between the second DC power supply and the reference potential point. a time constant circuit including a time constant larger than the time constant of the first time constant circuit; a second time constant circuit having a second time constant circuit, and a voltage generated in the second capacitor is supplied to the base. a first transistor whose conductivity is controlled by controlling the conductivity of the first transistor; a first voltage at the emitter of the capacitor that varies in accordance with the voltage developed across the second capacitor. and means for providing the first voltage to the base of the switching transistor. means for supplying the third capacitor, and a voltage developed across the third capacitor is supplied to the base and its conductor is The voltage is controlled and a voltage is maintained between the base of the switching transistor and the reference potential point. and a second transistor connected with a vector-emitter path. It is.

0010

[Effect]

According to the above-described configuration, the emitter of the first transistor is connected in series between the emitter and the ground. Since the second time constant circuit is connected to the connection point of the resistor, the first time constant circuit is It is no longer affected by the second time constant circuit.

[0011]

【Example】

Below, specific examples of the degaussing control circuit according to the present invention will be explained in detail based on the drawings. do. FIG. 1 shows an embodiment of this degaussing control circuit.

0012 In this figure, input terminal 3 is supplied with DC power supply voltage Vcc, and input terminal 3 is connected to a resistor. Grounded via resistor 2 and capacitor 1. Connection point of resistor 2 and capacitor 1 is connected to one end of contact 4A of relay 4, and the other end of this contact 4A is grounded. The other end of the degaussing coil 5 is connected.

[0013] In addition, a low voltage DC power supply voltage EB is supplied to the power input terminal 6, and this input terminal The terminal 6 is connected via a second time constant circuit 9 consisting of a series circuit of a resistor 7 and a capacitor 8. The connection point of this second time constant circuit 9 is connected to the degaussing switch 10 whose one end is grounded. The other end is connected via a resistor 11. Also, resistors 12 and 13 are directly connected between this connection point and ground. A series circuit is connected and the connection point of this series circuit is connected to the base of transistor 14. Ru. The emitter of this transistor 14 is grounded, and the collector is a switching transistor. Connected to the base of Star 15. The emitter of this transistor 15 is grounded and the collector The relay coil 4B is connected to one end of the relay coil 4B. The other end of this relay coil 4B is powered on. It is connected to the power terminal 6, and there is a back electromotive force at both ends of the relay coil 4B with the power supply side as the cathode. A diode 16 for force prevention is connected.

[0014] In addition, the power input terminal 6 is connected to a time constant circuit consisting of a series circuit of a resistor 17 and a capacitor 18. 19, and the connection point of this time constant circuit 19 is connected to the base of the transistor 20. Continued. The collector of this transistor 20 is connected to the power input terminal 6, and the emitter A series circuit of resistors 21 and 22 is connected between the terminal and ground. The connection point of this series circuit is Connected to the base of transistor 15.

[0015] With this configuration of the degaussing control circuit, for example, when power is applied to a display monitor, Then, the DC power supply voltage Vcc generated on the secondary side of the regulator is supplied to the power input terminal 3. The capacitor 1 is charged via the resistor 2 by the DC power supply Vcc. Koto and the first time constant circuit 19 is an emitter follower connected transistor connected to the base. The emitter voltage of the star 20 rises from the lower side by this time constant circuit 19, so Transistor 15 is off, relay coil 4B is not energized, and contact 4A is closed. It is in an open state. Here, we will control the charging time of capacitor 1 for the degaussing coil. The values of the resistor 17 and capacitor 18 of the first time constant circuit 19 are determined by the DC power supply Vcc. to complete charging of capacitor 1, or for a slightly longer period of time. When the switch transistor 15 is set to turn on, this capacitor 1 becomes the resistor. 2, the emitter of transistor 20 is charged by DC power supply Vcc through The potential rises, switching transistor 15 turns on, and contact 4A of relay 4 opens. closed, a resonant current flows from the capacitor 1 to the degaussing coil 5, and the surface of the cathode ray tube is degaussed. A magnetic action takes place.

[0016] The values of the resistor 7 and capacitor 8 of the second time constant circuit 9 that controls the demagnetization time are the same as those of the first The time constant is set to be longer than the time constant circuit 19 of After a few seconds, transistor 14 turns on and changes the base voltage of switch transistor 15. In order to reduce the voltage to 0.6 V or less, this transistor 15 is turned off and relay 4 becomes an open circuit. The degaussing operation stops. Here, the emitter-follower connected transistor 20 is Since the transistor 14 is connected to the connection point of the resistors 21 and 22 connected to the transmitter, , the first time constant circuit 19 is not affected by the second time constant circuit 9, and the first time constant circuit 19 is not affected by the second time constant circuit 9. Capacitor 18 remains undischarged.

[0017] If you press the degaussing switch 10 when degaussing manually, the second time constant circuit 9 The charge accumulated in capacitor 8 is discharged, transistor 14 is turned off, and capacitor 8 is turned off. Since transistor 18 is not discharged, the base potential of transistor 15 immediately drops to 0.6 V. To overcome this, transistor 15 for this switch turns on, and relay 4 turns on, turning it off. A current flows through the magnetic coil 5, and a manual demagnetization operation is started.

[0018] After the degaussing operation continues for several seconds, the resistor 7 constituting the second time constant circuit 9 Due to the time constant of capacitor 8, the base potential of transistor 14 rises again and the transistor Since the transistor 14 is turned on, the switching transistor 15 is turned off and the degaussing operation is stopped.

[0019] In the degaussing control circuit configured in this way, the display module is turned on after the power is turned on. Connect resistor 2 so that capacitor 1 is charged until the monitor screen is displayed. and the value of capacitor 1, and the values of resistor 17 and capacitor 18 of the first time constant circuit 19. By selecting approximately the same time, the delay in degaussing time can be made less noticeable. Demagnetization operation can be performed effectively.

[0020] In addition, the present invention demagnetizes by passing a resonant current through the degaussing coil 5 as in the above-mentioned embodiment. In addition to the type that uses direct current to charge capacitor 1, this Another direct current method of demagnetization in which the discharge current of the capacitor 1 is passed through the degaussing coil 5 to perform demagnetization. It can also be applied to all circuits.

[0021]

[Effect of the idea]

As explained above, according to the present invention, the charging time of the capacitor for the degaussing coil is The controlling time constant circuit is not affected by the time constant circuit controlling the demagnetization time, so Even with DC degaussing circuits, there is automatic degaussing immediately after power is turned on, and manual switch operation. Manual degaussing can be performed quickly without wasting time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a degaussing control circuit according to the present invention.

FIG. 2 is a circuit diagram showing a conventional degaussing control circuit.

[Explanation of symbols]

1...Capacitor for degaussing coil 4...Relay 5...Degaussing coil 7...Resistor for time constant 8...Capacitor for time constant 9...Second time constant circuit 10...Degaussing switch for manual use 14...Transistor 15...For switch Transistor 17...Resistor for time constant 18...Capacitor for time constant 19...First time constant circuit 20...Transistor with emitter follower connection

Claims (1)

[Scope of utility model registration request] Claim 1: A first battery charged by a first DC power supply.
a degaussing coil to which the voltage charged in the first capacitor is supplied via switching means including a switching transistor, and a second capacitor connected between a second DC power source and a reference potential point. and a third capacitor connected between the second DC power supply and a reference potential point, the time constant circuit being larger than the time constant of the first time constant circuit. a second time constant circuit having a time constant; a first transistor whose conductivity is controlled by supplying the voltage generated in the second capacitor to its base; and an emitter of the first transistor. means for generating a first voltage that varies in accordance with the voltage generated across the second capacitor; means for supplying the first voltage to the base of the switching transistor; and means for supplying the first voltage to the base of the switching transistor; a second transistor whose conductivity is controlled and whose collector-emitter path is connected between the base of the switching transistor and a reference potential point.