CN1073043A - The stray emission preventiong circuit of cathode ray tube - Google Patents

Abstract

Cathode ray tube stray emission preventiong circuit in having the system of cathode ray tube comprises: charge and discharge device, and input system supply voltage when system switches on is so that with a constant-potential charge, then discharge during system cut-off; Switching device, in system when energising, form open circuit between the high voltage unit of cathode ray tube and ground, form closed circuitly during system cut-off between them, and the residual high pressure in the target ray tube discharges.This circuit is installed on the system circuit board.When system cut-off, the residual high pressure in the cathode ray tube is discharged rapidly, therefore the spurious emissions phenomenon can not occur on phosphor screen.

Description

The stray emission preventiong circuit of cathode ray tube

The present invention relates generally to cathode ray tube, particularly the stray emission preventiong circuit of cathode ray tube.

As everyone knows, in television receiver or monitor, cathode ray tube is a basic element of character.

The structure and the operation principle of conventional cathode ray tube are described briefly hereinafter with reference to Fig. 1 and 2.

Fig. 1 represents the structure of conventional cathode ray tube.Cathode ray tube comprises the convergence parts 7 on neck 13 and the neck 13, and its effect is that meticulous convergence adjustment is carried out in the path of three electron beams of red to corresponding respectively to (R), green (G), blue (B) colour signal.Also have an electron gun 10, therefrom send three electron beams, their path is adjusted subtly.

Assemble parts 7 and comprise a static convergence permanent magnet and a dynamic convergence coil, permanent magnet is used for being adjusted at the convergence of the electron beam at phosphor screen center, coil is used for adjusting the convergence of phosphor screen electron beam all around, assemble parts 7 and make three electron beams can pass the corresponding aperture in the shadow mask 3 on the whole phosphor screen simultaneously, shadow mask 3 is fixed on the framework 11.

By being fixed on the effect of the deflecting coil 6 on the pipe awl 2, three electron beams can both required angle of deflection in each direction.According to the signal that applies from the outside, sawtooth signal for example, deflecting coil 6 is determined the yawing moment and the deflection angle of electron beams.By after being fixed on the respective aperture in the shadow mask 3 on the framework 11, the electron beam of deflection is beaten on the fluorescent material of the inner surface that is applied to surface glass 1, produces corresponding color thus.In other words, three electron beams pass corresponding hole in the shadow mask 3 simultaneously with a deflection angle, beat on fluorescent material 4 with different separately angles again then, and this is because three electron beams are to pass corresponding hole with different separately directions.Because the red, green, blue color phosphor constitutes a fluorescent material unit, so according to the direction and the intensity own of three electron beams bumps, in the corresponding fluorescent material of phosphor screen position, three electron beams of bump just produce various color beam.Therefore, shadow mask 3 can be counted as color-dividing electrode.

The top of pipe awl 2 also has an anode cap 12, has added an anode voltage above, as the driving voltage of cathode ray tube.When high pressure that has added an about 30KV on the anode cap 12 or anode voltage, because three electron beams are molecular by negative electricity, so three electronics that the high pressure that applies makes electron gun 10 send to be inhaled to panel glass 1 by very strong power, beat then on fluorescent material 4.

Approximately the high pressure of 30KV is on the graphite of anode cap 12 and the inner surface by being coated on cathode ray tube and anode electrode G4 that getter 8 is applied to electron gun 10.Getter 8 in the cathode ray tube is used for improving its vacuum degree.Getter 8 has the barium of about 300mg, and it absorbs the gas molecule as hydrogen, nitrogen, carbon dioxide, carbon in the cathode ray tube, improves the vacuum degree of cathode ray tube thus.As mentioned above, by getter 8, the 30KV high pressure that is applied on the anode cap 12 is added on the anode electrode G4.

G4 is different with anode electrode, and other electrode in the electron gun 10 applies by corresponding joint respectively as voltage on control grid G1, negative electrode K, screen grid G2 and the focus mask G3 and the voltage on the filament H.

Each electrode required voltage is as follows in the real work:

Negative electrode K:100～180V

Control grid G1:0～100V

Screen grid G2:300～700V

Focus mask G3:4～6KV

Anode G4:20～30KV

On the other hand, also be fixed with an interior guard shield 5 on the framework 11 in the cathode ray tube, so that make scanning beam avoid influence of geomagnetic.5 pairs of earth magnetism of interior guard shield shield, thereby have avoided the reduction of colorimetric purity.

It should be noted that the no related substance that enters sticks on the parts of cathode ray tube in the process of making cathode ray tube, will produce stray electron in the therefore conventional cathode ray tube.In other words, the residual high pressure of the anode electrode G4 that no related substance may exist when turning off television receiver or monitor is had an effect, thereby produces stray electron.The stray electron of Chan Shenging is beaten on fluorescent material 4 then.This causes unnecessary luminous of fluorescent material 4.This phenomenon is called spurious emissions.

Manufacturing process according to the cathode ray tube of routine burnouts no related substance by bump in ageing process.The purpose of doing like this is in order to prevent to produce stray electron, although have residual high pressure on the anode electrode G4 when turning off television receiver or monitor.Ageing process is the thermionic emission for the active electron rifle.That is to say that by applying voltage for filament H it is heated, thereby produce Joule heat, heat is added to the oxide layer of negative electrode K then, makes the oxide layer heat of emission electronics (negatron) of negative electrode K thus.The hot electron of emission is focused, and is quickened by the electrode of electron gun 10, arrives fluorescent material 4 then.

Knockout process is that high pressure is added to cathode ray tube, and no related substance burnouts.

Yet conventional cathode ray tube has following shortcoming, in order to remove the no related substance in the cathode ray tube fully by knockout process, a very high voltage must be added in the cathode ray tube.But, boosted voltage is limited.Be about to voltage and rise between the magnetic pole (not shown) that very high meeting causes electron gun 10 and discharge, at this moment negative electrode K will have a negative impact.Therefore in the manufacture process of cathode ray tube, should consider to remove the no related substance in the cathode ray tube, consider again to set and clash into suitable high voltage.As a result, also remain some no related substances in the cathode ray tube, the residual high pressure that exists when turning off television receiver or monitor is had an effect, and causes the spurious emissions phenomenon on the phosphor screen.

Fig. 2 represents to have the state diagram that the 30KV high pressure on the system of cathode ray tube such as television receiver or monitor be added in cathode ray tube after cutting off the electricity supply the anode cap discharges naturally.As we can see from the figure, the high pressure of 30KV will be used for a long time discharge off naturally.

The present invention is exactly in order to address the above problem.The purpose of this invention is to provide a cathode ray tube stray emission preventiong circuit, it can be when cut-out has the power supply of system of cathode ray tube, the high pressure that remains on the anode electrode in the cathode ray tube is carried out instantaneous discharge, thereby prevented the spurious emissions phenomenon on the phosphor screen, circuit is installed on the circuit board of system.

According to the present invention, in having the system of cathode ray tube, the cathode ray tube stray emission preventiong circuit comprises: charging and electric discharge device, system power supply voltage of input when switching in system, so that charge with a constant voltage, when system cut-off, the voltage that is filled discharged; Switching device, when system switches on, between the high voltage unit of cathode ray tube and ground, form open circuit, when system cut-off, in response to the charging voltage that will be discharged as driving voltage, form closed circuitly between the high voltage unit of cathode ray tube and ground, the residual high pressure in the target ray tube discharges.

From detailed description below in conjunction with accompanying drawing, will more clearly understand above and other objects of the present invention, feature and advantage, wherein:

Fig. 1 represents the structure of conventional cathode ray tube;

The system that Fig. 2 represents to have cathode ray tube according to prior art after cutting off the electricity supply, the state diagram that the residual high pressure in the cathode ray tube discharges naturally;

Fig. 3 is the block diagram of cathode ray tube stray emission preventiong circuit of the present invention;

Fig. 4 is the detailed circuit diagram of the circuit among Fig. 3 of the present invention;

Fig. 5 is the sequential chart of the signal that sends of the parts in Fig. 4 circuit of the present invention; And

Fig. 6 represents system that the present invention has cathode ray tube after cutting off the electricity supply, the state diagram that the residual high pressure in the cathode ray tube discharges naturally.

With reference to Fig. 3, the block diagram of the cathode ray tube stray emission preventiong circuit of the present invention that drawn here.As shown in the figure, have cathode ray tube 20(referring to Fig. 4) system in, cathode ray tube 20 stray emission preventiong circuits comprise a charging that links to each other with system power supply 21 and discharge portion 23, when switching on, system imports a voltage PV from power supply 21, so that charge with a constant voltage CV, when system cut-off with the voltage CV that filled 22 discharges over the ground, also comprise switch sections 25, when system switches on, between the high voltage unit 24 and 22 of cathode ray tube 20, form open circuit, when system cut-off, between the high voltage unit of cathode ray tube and ground, form closed circuit, take the residual height in the cathode ray tube 20 by force HV 22 discharges over the ground, circuit is installed on the circuit board of system.

Switch sections 25 comprises the first switch 25a, when applying driving voltage DV, between the high voltage unit 24 of cathode ray tube 20 and ground 22, form closed circuitly, when not applying driving voltage DV, between them, form open circuit, also comprise second switch 25b, when system switches on, between charging and the discharge portion 23 and the first switch 25a, form open circuit, when system cut-off, between them, form closed circuitly, charging voltage CV is applied on the first switch 25a as driving voltage DV.

With reference to Fig. 4, drawn here according to the detailed circuit diagram of the circuit among Fig. 3 of the present invention.The first switch 25a has a relay coil 25a1 and relay contact 25a2, and relay contact 25a2 is with anode cap 12 or high voltage unit 24(Fig. 3 of cathode ray tube 20) link to each other with ground.Because the residual voltage during system cut-off in the cathode ray tube 20 is very high, thus relay coil 25a1 to grow at the duration of residual high pressure so that to its discharge.

Still as shown in Figure 4, second switch 25b among Fig. 3 has a diode D1, its positive pole links to each other with the power end PT of system, and relay coil 25b1 is connected between the negative pole and ground of diode D1, and relay contact 25b2 is connected DT1 and holds and apply between charging voltage CV and the DT2 end.

Charging and discharge portion 23 comprise a diode D2 and a capacitor C1, and diode D2 is connected between the negative pole and DT2 end of diode D1, and capacitor C1 is connected between the negative pole and ground of diode D2.

Though the relay contact 25a2 in first switch 25 only with cathode ray tube 20 in apply ceiling voltage usually anode cap 12 link to each other, it both can link to each other with anode cap 12, can link to each other with other high voltage unit again, such as focus mask G3.Therefrom as can be seen, though the relay contact 25a2 in first switch 25 only with on being applied to panel glass 1 causes that the anode cap 12 of the high pressure of induced voltage links to each other, the spurious emissions phenomenon on the phosphor screen also can be prevented.

The operation principle of the cathode ray tube 20 among Fig. 4 is identical with power 1 lobe cathode ray tube with structure, so save description of them here.

The operation principle of circuit is described with reference to Fig. 5 among Fig. 4, and Fig. 5 is the sequential chart of the signal that sends according to the parts in Fig. 4 circuit of the present invention.

At first, when system's (for example television receiver or monitor) switched on, relay coil 25b1 was wherein delivered in the diode D1 rectification of signal shown in Fig. 5 A in second switch 25b, and be recharged with discharge portion 23 in diode D2 rectification.Simultaneously, when the voltage that applies through rectification, the relay contact 25b2 among the second switch 25b disconnects (being initial state), and this is owing to it is a Type B.

On the other hand, signal shown in Fig. 5 B be added to the charging and discharge portion 23 in capacitor C1 on, form a constant voltage CV thus capacitor C1 charged.Relay contact 25b2 in second switch 25b disconnects, the not conducting of relay coil 25a1 among the first switch 25a, and relay contact 25a2 wherein disconnects (being open-circuit condition), and this is owing to it is the A type.

When system cut-off under these conditions, signal shown in Fig. 5 c is added on the relay coil 25b1 among the second switch 25b, makes Type B relay contact 25b2 wherein connect (being closed circuit state) thus.At this moment the charging and discharge portion 23 in capacitor C1 on fill voltage CV begin release.In other words, fill voltage CV be applied on the relay coil 25a1 among the first switch 25a as the relay contact 25b2 of driving voltage DV in second switch 25b.

When the relay coil 25a1 among the first switch 5a was driven voltage DV driving, A type relay contact 25a2 wherein connected (being closed circuit state), made thus to be added with anode cap 12 ground connection of about 30KV high pressure.As a result, the residual voltage in the cathode ray tube 20 discharges at a terrific speed, as shown in Figure 6.Compare with Fig. 2, as can be seen from Figure 6, according to the present invention, residual voltage discharges with faster speed.

As previously mentioned, prior art is intended to make in the process of cathode ray tube removes stray electrical component itself, and they are the reasons that cause the spurious emissions phenomenon.Yet because other all factor, the attempt that the stray electrical component is removed in the plan in the prior art fully is restricted.

Therefore as previously mentioned, according to the present invention, a circuit has been installed on the circuit board of system, it can make the residual high pressure in the cathode ray tube discharge in the very short time behind system cut-off, thereby removes the potential difference in the cathode ray tube.As a result, although there is stray electron in cathode ray tube, the spurious emissions phenomenon can not appear yet on phosphor screen.

Though disclose most preferred embodiment of the present invention for the present invention is described, those skilled in the art should understand, under the situation that does not deviate from claim institute's restricted portion of the present invention and spirit, can make various modifications, replenish and replace the present invention.

Claims (5)

1, in having the system of cathode ray tube, the stray emission preventiong circuit of a cathode ray tube is characterised in that and comprises:

Charging and electric discharge device, system power supply voltage of input so that charge with a constant voltage, discharges to the voltage that is filled when system cut-off when switching in system;

Switching device, when system switches on, between the high voltage unit of cathode ray tube and ground, form open circuit, when system cut-off, in response to the charging voltage that will be discharged as driving voltage, form closed circuitly between the high voltage unit of cathode ray tube and ground, the residual high pressure in the target ray tube discharges.

2, circuit as claimed in claim 1, wherein said switching device comprises:

First switch when applying driving voltage, forms closed circuitly between the high voltage unit of cathode ray tube and ground, when not applying driving voltage, forms open circuit between them; And

Second switch when switching in system, forms open circuit between said charging and discharge portion and said first switch, when system cut-off, form closed circuitly between them, and charging voltage is applied on said first switch as driving voltage.

3, circuit as claimed in claim 2, wherein said first switch comprises:

A relay coil; And

Relay contact, when driving voltage is applied on the said relay coil, this contacting, when not having driving voltage to be applied on the said relay coil, this contact disconnects.

4, as circuit as described in the claim 2, wherein said second switch comprises:

A diode when system switches on, carries out rectification to the supply voltage of importing;

A relay coil receives the voltage through rectification as driving voltage that obtains from said diode; And

Relay contact, when driving voltage was applied on the said relay coil, this contact disconnected, when not having driving voltage to be applied on the said relay coil, this contacting.

5, circuit according to claim 1, wherein said charging and electric discharge device comprise:

A diode when system switches on, carries out rectification to the supply voltage of importing;

A capacitor is used from the voltage charging through rectification that it is said that diode obtains.

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