JP2000156790A - Horizontal deflection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably move raster in a horizontal direction. SOLUTION: In a horizontal deflection circuit provided with a centering circuit 50 that moves raster in a horizontal direction by changing the current direction supplied to a deflection yoke 4 so as to adjust a raster position, a connecting point between an S-shaped capacitor 5 and the deflection yoke 4 is provided with a diode 52, a capacitor 55 connected to an anode of the diode 52, a switching element 51 connected in parallel with the diode 52, and a switching element control means 60 that controls the switching state of the switching element 51. The switching element control means 60 controls the switching state of the switching element 51 to control a current supplied from the S-shaped capacitor 5 to the capacitor 55, to control the current supplied to the deflection yoke 4 in the centering circuit 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CRT (cathode-
The present invention relates to a horizontal deflection circuit used in a television display device using a ray tube.

[0002]

2. Description of the Related Art In general, in an image display apparatus using a CRT, the position of a raster, which is the reachable range of an electron beam emitted from an electron gun, varies with respect to a tube surface due to manufacturing variations of the CRT. There are many. For this reason, in the video display device, problems such as the linearity of the displayed image in the vertical direction and the horizontal direction being disturbed, and the lack of the raster from the end of the tube surface and the occurrence of a portion where the image cannot be displayed may occur. There is. Therefore, many video display devices using a CRT are provided with a centering circuit for correcting a raster shift. When moving the raster position, a DC current is superimposed and applied to the deflection yoke. However, the correction in the vertical direction does not pose a problem since the correction is simple due to the circuit configuration. However, in a horizontal deflection circuit mainly configured using a resonance circuit, it is often difficult to superimpose a DC current on the deflection yoke. For example, in television receivers, horizontal centering circuits 100 and 110 as shown in FIGS. 8 and 9 have been widely used. The centering circuit 10 shown in FIGS.
Reference numerals 0 and 110 are used in a so-called diode modulator type horizontal deflection circuit shown in FIG. 10 which has been used in a television receiver which has been widely used in the past.

A centering circuit 110 as shown in FIG.
Although it can be applied to a general horizontal deflection circuit, there is a problem that the circuit scale becomes large and the cost becomes high.

A centering circuit 100 as shown in FIG.
Although it can be configured at a lower cost than other centering circuits proposed in the present application, it is difficult to apply to a horizontal deflection circuit due to the circuit configuration. That is, the centering circuit 100 of FIG.
The switch 1 is connected to the intersection of the capacitor 103, the S-shaped capacitor 104, and the horizontal deflection yoke 105
06 and are connected by a diode 107 and a diode 108 which are selectively connected.

[0005] For example, when the diode 108 is oriented such that the cathode is connected to the S-shaped capacitor 104, the diode 108 conducts when the voltage across the S-shaped capacitor 104 becomes lower than the voltage across the capacitor 103.
In response to this, the voltage across the capacitor 103 decreases with the voltage across the S-shaped capacitor 104, and the DC voltage is applied to the S-shaped capacitor 104 while the diode 108 is conducting without significantly affecting the resonance operation of the horizontal deflection circuit. A current can be supplied. And the centering circuit is
By supplying a DC component current corresponding to the current supplied to the S-shaped capacitor 104 from the power supply 101 to the horizontal deflection yoke 105, the raster is translated in the horizontal direction.

On the other hand, a diode 107 for conducting a current in a direction opposite to that of the diode 108 is connected to a switch 106.
Is selected, the S-shaped capacitor 104
When the voltage between both ends rises above the potential of the capacitor 103, the diode 107 conducts, and current is supplied to the S-shaped capacitor 104 in the opposite direction to that described above without affecting the resonance operation of the horizontal deflection circuit. The raster is translated in a direction opposite to the above.

[0007]

In the centering circuit 100 described above, when the raster is to be stably moved to the left or right in the horizontal direction, the average value of the voltage at the power supply 101 and the voltage across the S-shaped capacitor 104 are equal. Is needed.

Here, in the above-described horizontal deflection circuit, the voltage across the S-shaped capacitor 104 has little relation to the voltage of the power supply 101, and the voltage across the S-shaped capacitor 104 is larger than the voltage of the power supply 101. Often a value. In such a case, in the centering circuit 100, the diode 1 that conducts the current in the direction in which the current is supplied from the S-shaped capacitor 104 to the capacitor 103 is used.
When 07 is selected, current flows in almost all sections,
A large current is supplied to the horizontal deflection yoke 105. That is, in such a centering circuit 100, it cannot be said that the average value of the voltage at the power supply 101 and the voltage across the S-shaped capacitor 104 is equal as described above.
When a large current is supplied to the horizontal deflection yoke 107 in this manner, the raster is often moved more than necessary, and it is often difficult to use the raster.

In order to solve such a problem, the centering circuit 100 does not take the voltage of the power supply 101 connected to the capacitor 103 via the choke coil 102 from the power supply for driving the deflection yoke of the horizontal deflection circuit. Although the above-mentioned problem can be solved by using a power supply having a potential equal to the average potential of the above, it becomes expensive in terms of cost as a centering circuit used in an ordinary television receiver.

Accordingly, the present invention has been proposed in view of the above situation, and has as its object to provide an inexpensive horizontal deflection circuit that can stably move a raster in the horizontal direction. I do.

[0011]

A horizontal deflection circuit according to the present invention for solving the above-mentioned problems adjusts the raster position by moving the raster in the horizontal direction by changing the direction of the current supplied to the deflection yoke. In a horizontal deflection circuit having a centering circuit, the centering circuit includes a diode having a cathode connected to a connection point between the S-shaped capacitor and the deflection yoke, a capacitor connected to an anode of the diode, and a parallel connection with the diode. A switching element connected thereto; and a switching element control means for controlling an open / close state of the switching element. The switching element control means controls the open / close state of the switching element to supply the switching element with the S-shaped capacitor to the capacitor. The magnitude of the current supplied to the deflection yoke by controlling the current And it is characterized in controlling the of can.

In such a horizontal deflection circuit, the magnitude of the current supplied from the S-shaped capacitor to the capacitor is controlled by controlling the switching state of the switching element by the switching element control means, and is supplied to the deflection yoke. Control the current.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A horizontal deflection circuit 1 to which the present invention is applied has, for example, the configuration shown in FIG. The horizontal deflection circuit 1 includes a parallel circuit including a horizontal output switching element 11, a damper diode 12, and a resonance capacitor 13,
A parallel circuit including a switching element 21, a damper diode 22, and a resonance capacitor 23 is connected in series, and power is supplied to the connection point via a primary winding coil of the flyback transformer 6. The other end of the switching element 11 is grounded, the horizontal deflection yoke 4 is connected to the other end of the switching element 21, and an S-shaped capacitor 5 is connected in series to the horizontal deflection yoke 4. The other end is grounded. The resonance capacitor 3 is connected in parallel to both ends of the series connection of the horizontal deflection yoke 4 and the S-shaped capacitor 5. Such a horizontal deflection circuit 1 includes a switching element 1
A pulse reading circuit 1 for reading the voltage between the terminals 21 and 21
7 and 27, and a switching element control circuit 40 that calculates on the basis of the voltage and controls on / off of the switching element 21.

Further, the horizontal deflection circuit 1 has a centering circuit 50 for controlling a voltage applied to both ends of the S-shaped capacitor 5 and supplying a DC current for moving the raster to the horizontal deflection yoke 4. .

Next, the circuit operation of the horizontal deflection circuit 1 will be described. In the horizontal deflection circuit 1 shown in FIG. 1, a horizontal (H) drive signal is input to the horizontal output switching element 11, and the horizontal output switching element 1
1 is turned on, the switching element control circuit 40 is also operated, and the switching element 21 is also turned on.
Is supplied with a deflection current. On the other hand, the switching element 11
Is turned off before the switching element 21,
This starts a retrace section (horizontal flyback section). During this retrace interval, the switching element 21 is turned on / off by the switching element control circuit 40. A series of these operations will be described below using a voltage or current waveform shown in FIG. 2 and an equivalent circuit shown in FIG. 3 by dividing a horizontal deflection section.

<Trace section a> Trace section a is a state in which both of the switching elements 11 and 21 are conducting.
The equivalent circuit has the configuration shown in FIG. 3A, and has the same configuration as the horizontal deflection circuit having one stage of the switching element. At this time, both the deflection current and the flyback transformer current increase at a slope corresponding to the voltage across the S-shaped capacitor 5 and the power supply voltage, respectively. The waveform of the deflection current at this time is shown in FIG.

<Initial of Retrace Section> To enter the retrace section, the switching element 11 is first turned off by a horizontal drive signal. At this time, since the switching element 21 is still conducting, the equivalent circuit has the configuration shown in FIG. At this time, the current supplied to the flyback transformer 6 and the horizontal deflection yoke 4
13 and produce a voltage across the resonant capacitors 3 and 13, whereby the current starts to reverse. That is, the voltage and current waveforms including the resonance operation are in the section b in FIG.

<Off-Period of Switching Element 21 in Retrace Section> In the latter half of the retrace section, after the deflection current reaches 0, even if the switching element 21 is turned off, the equivalent circuit is shown in FIG. )
The equivalent circuit when the switching element 21 is turned off before the deflection current reaches 0 in the first half of retrace is as shown in FIG. 3C, and another equivalent circuit is connected in series with the horizontal deflection yoke 4. This means that the resonance capacitor 23 has been connected. Since the deflection current also flows into the resonance capacitor 23, a voltage is also generated at both ends of the resonance capacitor 23, and a pulse voltage larger than the pulse at both ends of the switching element 11 can be applied to both ends of the horizontal deflection yoke 4. (See FIG. 2A). Here, since the peak value of the retrace pulse voltage at both ends of the switching element 11 is substantially determined by the power supply voltage, the retrace time and the ratio of the trace time, this pulse (see FIG. 2B) is boosted by the flyback transformer 6. , CRT electron gun.

<Latter Half of Retrace Section> In the retrace section, when all the electric charges flowing into the resonance capacitors 3, 13, and 23 flow out and the voltage at both ends becomes 0, the damper diode automatically conducts and ends (the diode is simple). Ideal diode for). Here, since the current flowing into the resonance capacitor 23 is always smaller than the current flowing into the resonance capacitor 13, the resonance capacitor 23 loses its charge earlier, and the damper diode 22 conducts earlier than the damper diode 12. For this reason, the pulse generated at both ends of the switching element 21 has a smaller pulse width than the pulse generated at both ends of the switching element 11 (see section c in FIGS. 2B and 2C). Furthermore, if the off-timing of the switching element 21 is delayed, the current flowing into the resonance capacitor 23 is further reduced, so that the pulse width at both ends of the switching element 21 at this time has a narrower pulse width and a lower pulse height. That is, by controlling the phase of the off timing of the switching element 21, the retrace pulse voltage applied to both ends of the horizontal deflection yoke 4 can be controlled, and as a result, the amplitude of the deflection current is changed. <Trace section e> When the damper diode 22 becomes conductive, the equivalent circuit returns as shown in FIG. 3 (b), and the retrace operation is performed in the same manner as in a normal deflection circuit until the voltage across the resonance capacitors 3 and 13 becomes zero. Figure 3
Returning to the form of the equivalent circuit of FIG.
In the trace section e, a horizontal deflection current flows from the horizontal deflection yoke 4 in the forward direction of the damper diodes 12 and 22 (see FIG. 2D). In the meantime, the switching elements 11 and 21 are kept in a conductive state to prepare for the next trace section a. As described above, the horizontal deflection current forms the horizontal deflection magnetic field in the horizontal deflection yoke 4 by repeating the above-described deflection sections a, b, c, and d.

The horizontal deflection circuit 1 controls the emission direction of the electron beam emitted from the electron gun by forming the horizontal deflection magnetic field as described above. Here, the horizontal deflection circuit 1
A centering circuit 50 is provided for adjusting the position of the raster, which is the range irradiated with the electron beam.

The centering circuit 50 includes a switching element 51 and a diode 5 connected in parallel between the S-shaped capacitor 5 and the horizontal deflection yoke 4, as shown in FIG.
2, a DC power supply 53 for emitting a DC voltage, and a DC power supply 5
3 includes a choke coil 54 to which a DC voltage is applied, and a capacitor 55 connected to the anode of the diode 52. Further, the centering circuit 50 includes a switching element control unit 60 connected to the switching element 51 and controlling on / off of the switching element 51.

In the centering circuit 50 having such a circuit configuration, charges are accumulated in the capacitor 55 and the S-shaped capacitor 5 by the DC voltage from the DC power supply 53,
A current flows through the diode 52 and the switching element 51 according to the potential difference between the S-shaped capacitor 5 and the capacitor 55. That is, when the potential of the S-shaped capacitor 5 is lower than the potential of the capacitor 55, the centering circuit 50 deflects from the S-shaped capacitor 5 by flowing a current in the forward direction of the diode 52, that is, the direction toward the S-shaped capacitor 5. A deflection current is supplied to the horizontal deflection yoke 4 in a direction toward the yoke. On the other hand, the centering circuit 50
When the potential of the S-shaped capacitor 5 is higher than the potential of the capacitor 55, a current flows in a direction toward the capacitor 55, so that a deflection current is supplied to the horizontal deflection yoke 4 from the deflection yoke toward the S-shaped capacitor 5. At this time, the centering circuit 50 controls the switching element 51 to open and close by operating the switching element control unit 60, and limits the amount of current supplied from the S-shaped capacitor 5 to the capacitor 55.

Next, the operation of the centering circuit 50 will be described with reference to FIGS. First, the switching element 51 is turned off in the latter half of the scanning section. The voltage change at both ends of the S-shaped capacitor 5 has a parabolic waveform as shown in FIGS. 5 and 6, but in the latter half of the scanning section after the time t ₁ in FIG. Is lower than the potential of the capacitor 55. When the potential of the S-shaped capacitor 5 becomes lower than the potential of the capacitor 55 in this way, the diode 52 becomes conductive, a current flows in a direction for supplying a current to the S-shaped capacitor 5, and the potential of the capacitor 55 decreases. 5 is reduced while maintaining substantially the same potential. After the capacitor 55 is turned on, the switching element 51 is turned on by the switching element control unit 60 before the potential at both ends of the S-shaped capacitor 5 at time t ₂ has completely dropped.

When the potential at both ends of the S-shaped capacitor 5 starts to rise at time t ₂ , the diode 52 is turned off, and current starts flowing out of the S-shaped capacitor 5 through the switching element 51. This current continues to flow through the switching element control section 60 to the time t ₃ when the switching element 51 turned off.

As a result, a current obtained by subtracting the current flowing from the diode 52 and the current flowing from the switching element 51 flows into the S-shaped capacitor 5. That is, if the time during which the switching element 51 is turned on, that is, the conduction time is shortened, a current flows into the S-shaped capacitor 5 through the diode 52, and conversely, the switching is performed as shown at times t _{4 to} t ₅ in FIG. If the conduction time of the element 51 is lengthened, a larger amount of current than the current flowing from the diode 52 flows out through the switching element 51, so that the current flows out of the S-shaped capacitor 5. Thus, by controlling the conduction time of the switching element 51 by the switching element control unit 60, the direction of the current supplied to the horizontal deflection yoke 4 can be changed, and the shift amount of the raster can be changed.

Next, a specific example of the centering circuit 50 will be described with reference to FIG.

The centering circuit 50 includes an FET switch 61 in place of the switching element 51 described above. The FET switch 61 includes a MOSFET (metal oxide) functioning as the above-described switching element 51.
a semiconductor field-effect transistor) and a diode 52. Since the centering circuit 50 includes a MOSFET as the switching element 51, the centering circuit 50 is turned on and off when a driving voltage is applied by the switching element control unit 60.

The switching element controller 60 receives a horizontal flyback pulse and a control voltage. The switching element control unit 60 is configured as shown in FIG. 7 to slice the sawtooth wave generated by the horizontal flyback pulse in the off-period shown in FIGS. 5 and 6 using a control voltage. And input to the transformer via the push-pull circuit and capacitor. Thereby, the switching element control unit 60
Controls the ON and OFF periods of the MOSFET, and controls the amount of current flowing from the S-shaped capacitor 5 to the capacitor 55.

The horizontal deflection circuit 1 includes a switching element 51 and the switching element 51.
Switching element control unit 60 for controlling the ON / OFF period of the switch
, The S-shaped capacitor 5 to the capacitor 5
5 can be controlled. Therefore, the horizontal deflection circuit 1 can control the amount of current flowing into the horizontal deflection yoke 4, and cannot be adjusted because a large current flows from the S-shaped capacitor 5 to the capacitor 55 when adjusting the raster position. And never. That is, according to the horizontal deflection circuit 1, the amount of current flowing from the S-shaped capacitor 5 to the capacitor 55 is controlled by adjusting the ON / OFF period of the switching element 51 by the switching element control unit 60, and the horizontal deflection yoke 4 The amount of current flowing can be controlled, and the amount of movement of the raster can be changed steplessly. Further, according to the horizontal deflection circuit 1, since the switching element control unit 60 having the above-described configuration is provided, adjustment of the on / off period of the switching element 51 can be performed without using a manual switch or the like. Furthermore,
According to the horizontal deflection circuit 1 described above, since it has the above configuration, it is possible to configure a centering circuit that adjusts the position of the raster in the horizontal direction at low cost.

[0031]

As described above in detail, the horizontal deflection circuit according to the present invention comprises a diode having a cathode connected to a connection point between an S-shaped capacitor and a deflection yoke, and a capacitor connected to an anode of the diode. A switching element connected in parallel with the diode, and switching element control means for controlling the open / close state of the switching element,
The magnitude of the current supplied from the S-shaped capacitor to the capacitor is controlled by controlling the open / close state of the switching element by the switching element control means, thereby controlling the magnitude of the current supplied to the deflection yoke. By controlling the supply of the current, the moving amount of the raster in the horizontal direction can be adjusted steplessly.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a horizontal deflection circuit to which the present invention is applied.

FIG. 2 is a diagram showing voltage and current waveforms at various parts of the horizontal deflection circuit.

FIG. 3 is a diagram showing a basic equivalent circuit for explaining the operation of the horizontal deflection circuit.

FIG. 4 is a diagram showing a configuration of a centering circuit provided in the horizontal deflection circuit.

FIG. 5 is a diagram for explaining an operation of the centering circuit when a current flows from the S-shaped capacitor to the capacitor.

FIG. 6 is a diagram for explaining an operation of a centering circuit when a current flows from a capacitor to an S-shaped capacitor.

FIG. 7 is a diagram illustrating a configuration of a switching element control unit.

FIG. 8 is a diagram showing a configuration of a conventional centering circuit.

FIG. 9 is a diagram showing a configuration of another conventional centering circuit.

FIG. 10 is a diagram illustrating a configuration of a diode modulator type horizontal deflection circuit.

[Explanation of symbols]

Reference Signs List 1 horizontal deflection circuit, 4 horizontal deflection yoke, 5 S-shaped capacitor, 50 centering circuit, 51 switching element, 52 diode, 55 capacitor, 60 switching element control unit

Claims (1)

[Claims] 1. A horizontal deflection circuit having a centering circuit for adjusting a raster position by moving a raster in a horizontal direction by changing a direction of a current supplied to a deflection yoke, wherein the centering circuit includes an S-shaped capacitor and A diode having a cathode connected to a connection point with the deflection yoke,
A capacitor connected to the anode of the diode,
A switching element connected in parallel with the diode,
A switching element control means for controlling an open / close state of the switching element; and a magnitude of a current supplied from the S-shaped capacitor to the capacitor by controlling the open / close state of the switching element by the switching element control means. And controlling the magnitude of the current supplied to the deflection yoke.