JPH01168168A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To attain just focus even at a corner of a CRT display by providing a horizontal deflection circuit in addition to a focus voltage generating circuit so as to modulate a focus voltage in a parabolic wave without deteriorating the linearity of a horizontal deflection current. CONSTITUTION:A large current with excellent linearity is obtained at a horizontal deflection circuit 3 as a horizontal deflection current in a switching pulse generated from a horizontal output circuit 2, a resistor R4 is connected to a sawtooth wave generating circuit 40 in a high voltage generating circuit 4 and a sawtooth wave voltage is obtained across the resistor and the sawtooth wave voltage is fed to a parabolic wave voltage generating circuit 41. Then the generated parabolic wave voltage is fed to a focus voltage generating circuit 5 to give a parabolic wave voltage to a focus electrode B. Thus, the parabolic wave voltage for focus adjustment is generated without deteriorating the linearity of the horizontal deflection current and a picture with matched focus is obtained even at the corner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic focus circuit that generates a focus voltage to be applied to a focus electrode of a display device including a CRT display or the like.

BACKGROUND ART] As is conventionally known, a horizontal deflection circuit used in a display device equipped with a CRT display, such as a television receiver, is generally configured as shown in FIG. .

In FIG. 2, 11 is a horizontal output transistor whose switching is controlled by a horizontal pulse, 12 is a damper diode, and a horizontal deflection coil 13 is outputted in parallel with the transistor 11.

14 is a capacitor for 8-character correction.

Further, 15 indicates a flyback transformer, and a predetermined DC power supply is supplied to the transistor 11 via this primary coil 15a.
is applied to the collector side of

On the secondary coil 15b side of the flyback transformer 15,
A diode 17 for high voltage rectification is connected, and the rectified high voltage can be applied to the anode electrode A of the CRT display 18.

In such a circuit configuration, the rectified high voltage is applied to the variable resistor 19 for voltage division, and the divided voltage obtained from this is applied to the focus voltage w3 as the voltage for focus adjustment.
applied to B.

[Problems to be Solved by the Invention] Incidentally, the CRT display 18 described above often uses a tube whose phosphor screen has a predetermined curvature.

On the other hand, the focus voltage applied to the focus electrode B is a DC voltage at a substantially constant level. Therefore, there is a problem in that although the center of the CRT display 18 is in focus, the closer it gets to the corners, the less the focus is.

Therefore, it has been proposed to apply a parabolic wave-like voltage to the focus voltage tMB, which has a high level at the corners of the CRT display 18 and a low level as it approaches the center.

This parabolic wave voltage can be generated from the deflection current Iy.

That is, by connecting a resistor in series with the horizontal deflection coil 13, a sawtooth wave voltage can be obtained from both ends of the resistor.

A parabolic wave voltage obtained by integrating this sawtooth wave voltage was applied to the focus electrode B.

By the way, as is well known, the horizontal deflection current Iy mentioned above is
It is necessary to have a very large deflection current and excellent linearity.

However, when a parabolic wave voltage is generated from this horizontal deflection current ry, a resistor for forming the parabolic wave voltage is interposed, so there is a problem that the linearity of the horizontal deflection current Iy deteriorates.

Therefore, this invention solves these conventional problems by 11!
This problem is easily solved by proposing a dynamic focus circuit that supplies a parabolic voltage to the focus electrode.

[Technical means for solving the problems] In order to solve the above problems, the present invention provides a horizontal deflection circuit that obtains a horizontal deflection current using a horizontal deflection coil, and a voltage that is supplied to the anode electrode of a CRT display. A focus voltage generation circuit that generates a high voltage generation circuit, a focus voltage generation circuit that generates a focus voltage to be supplied to a focus electrode of a CRT display, and a horizontal output circuit that drives and controls a horizontal deflection circuit, a high voltage generation circuit, and a focus voltage generation circuit, The present invention is characterized in that a parabolic wave voltage generated from the sawtooth wave voltage obtained in the high voltage generating circuit is supplied to a focus voltage generating circuit, thereby applying a parabolic wave voltage to the focus electrode.

[Function] In this configuration, the horizontal deflection circuit 3, the high voltage generation circuit 4, and the focus voltage generation circuit 5 are simultaneously driven in response to the switching pulse generated by the horizontal output circuit 2.

In the horizontal deflection circuit 3, since no resistor is inserted in series with the horizontal deflection coil L3, a large current with excellent linearity can be obtained as a horizontal deflection current.

In the high voltage generation circuit 4, a resistor R4 is connected to the sawtooth wave generation circuit 40.
is connected, and a sawtooth wave voltage is obtained from both ends.

This sawtooth wave voltage is supplied to a parabolic wave voltage generation circuit 41.

The horizontal parabola wave voltage obtained by integration by the parabola wave voltage generation circuit 41 is superimposed on the vertical parabola wave voltage taken out from the integrating capacitor C7, and this is applied to the transistor Tr6 which controls the power supply voltage Vcc3 of the focus voltage generation circuit 5. applied to the base.

As a result, the output voltage of the focus voltage generation circuit 5 (the voltage across the capacitor C6) is modulated into a parabolic wave and is supplied across the focus electrode.

Therefore, the parabolic wave voltage for focus adjustment can be generated relatively easily without deteriorating the linearity of the horizontal deflection current Iy.

This makes it possible to obtain a focused image not only at the center but also at the corners of the CRT display 18.

[Embodiment] Next, a case in which an example of the dynamic focus circuit according to the present invention is applied to a display device equipped with a CRT display will be described in detail with reference to FIG. 1.

FIG. 1 is a diagram showing the configuration of a dynamic focus circuit 1 of the present invention.

In the figure, 1 is a dynamic focus circuit, and this dynamic focus circuit 1 is composed of a horizontal output circuit 2, a horizontal deflection circuit 3, a high voltage generation circuit 4, and a focus voltage generation circuit 5.

As is well known, the horizontal deflection circuit 3 includes a transistor Tr3 that switches a horizontal deflection current (deflection yoke current) Iy.
, a damper diode D3, a horizontal deflection coil L3, a character-of-eight correction capacitor C3, a coil L31, a resistor R3, and a power supply voltage Vccl.

The horizontal deflection coil L3 is an inductance element with very low internal resistance, and the horizontal deflection current flowing through the horizontal deflection coil L3 has a very large current value and excellent linearity.

The high voltage generating circuit 4 is a circuit for supplying high voltage to the anode electrode A of the CRT display 18.

This high voltage generation circuit 4 includes a switching transistor T
r4, diode D4, coil L4, capacitor C4, and resistor R4, as well as a parabolic wave voltage generation circuit 41, resistor R41, flyback transformer T4, resistor R42, and diode D4.
1 and a power supply voltage Vcc2.

The focus voltage generation circuit 5 is connected to the CRT display 18.
This is a circuit for generating a relatively high voltage to be supplied across the focus electrode.

This focus voltage generation circuit 5 includes a switching transistor Tr5, a diode D5, a coil L5, a capacitor C5, a transformer T5, a diode D6, and a capacitor C.
6. Variable resistor R5 for fine adjustment of focus voltage, transistor Tr6 that controls power supply voltage Vcc3, vertical deflection coil L6, integrating capacitor C7 that generates vertical parabolic wave voltage, coupling capacitors C8 and C9, and capacitor CIO. It is configured.

The horizontal output circuit 2 includes transistors Tr3 and Tr4 of each circuit.
．． This is a circuit for simultaneously driving and controlling Tr5, and is composed of a transistor T r 2 , a drive transformer T2, and a resistor R2.

A case will be described in which focus correction of the CRT display 18 is performed using the dynamic focus circuit 1 configured as described above.

In response to the switching pulse generated in the horizontal output circuit 2, each transistor Tr3. T
r4. T r5 is switched at the same time.

As a result, in the horizontal deflection circuit 3, a horizontal deflection current Iy with excellent linearity and a large current value is obtained.

This is because, as described above, a resistor or the like is not interposed in the horizontal deflection coil L3.

In the high voltage generation circuit 4, high voltage is completely supplied to the anode electrode A of the CRT display 18 by the flyback transformer T4, and a sawtooth wave voltage is taken out from both ends of the resistor R4 and supplied to the parabolic wave voltage generation circuit 41.

Parabolic wave voltage generation circuit 41 and sawtooth wave generation circuit 40
The sawtooth wave voltage supplied from the converter is integrated and converted into a parabolic wave voltage.

The parabolic wave voltage obtained by the parabolic wave voltage generating circuit 41 is supplied to the focus voltage generating circuit 5.

In the focus voltage generation circuit 5, this horizontal parabolic voltage is supplied to the base of the transistor Tr6 that controls the power supply voltage Vcc3 via the coupling capacitor C9.

At this time, the sawtooth wave voltage supplied from the upper vertical deflection coil 6 side is integrated by the integrating capacitor C7, and this vertical period parabolic wave voltage is completely supplied to the capacitor CIO via the coupling capacitor C8.

In this capacitor CIO, this vertical period parabola wave voltage is superimposed on the above-mentioned horizontal period parabola wave voltage.

The superimposed synthetic parabolic wave voltage is applied to the base of transistor Tr6.

Here, since the power supply voltage Vcc3 is used as a drive voltage for the transformer T5, this power supply voltage Vcc3 is modulated by the composite parabolic wave voltage.

Therefore, the voltage obtained on the secondary side of the transformer T5 is also a voltage modulated by the combined parabolic wave voltage of horizontal and vertical periods.

This output voltage is applied to a voltage adjusting resistor R5 via a diode D6 and a capacitor C6, and the adjusted parabolic wave voltage is supplied to the focus electrode B as its focus voltage.

Since this focus voltage is a DC voltage modulated in a parabolic wave shape with horizontal and vertical cycles, the focus is dynamically adjusted.

On the other hand, this dynamic focus voltage is a voltage that is minimum at the center of the horizontal and vertical periods.

Therefore, the focus voltage applied to the focus electrode has a higher level at the corner portions of the CRT display 18 than at the center portion. Therefore, in the CRT display 18 having a curvature on the phosphor screen,
Not only the center of the phosphor screen but also the corners can be brought into focus.

8. Since the current flowing through the coil L4 provided in the high voltage generation circuit 4 is a current for generating high voltage, its current value is equal to the horizontal deflection current Iy obtained in the horizontal deflection circuit 3.
The diameter does not need to be large, and the linearity does not need to be very good.

Coil L5 provided in focus voltage generation circuit 5
The current value and linearity of the current flowing through the circuit are the same as those described above.

As a result, the resistor R4 provided in the sawtooth wave generating circuit 40 may have a relatively small resistance value depending on the magnitude of the current flowing through the coil L4.

In the embodiment, a CRT display 18 having a curvature on the phosphor screen was used, but the shape is not limited to this, and any CRT display whose corners are out of focus compared to the center may be used. The dynamic focus circuit 1 according to the present invention can be applied.

[Effects of the Invention] As explained above, the present invention provides a horizontal deflection circuit that obtains a horizontal deflection current using a horizontal deflection coil, a high voltage generation circuit that generates a voltage to be supplied to an anode electrode of a CRT display, and a focus electrode of a CRT display. A focus voltage generation circuit that generates a focus voltage to be supplied to a horizontal deflection circuit, a high voltage generation circuit, and a horizontal output circuit that drives and controls a focus voltage generation circuit. The present invention is characterized in that the generated parabolic wave voltage is supplied to a focus voltage generation circuit to apply the parabolic wave voltage to the focus electrode.

Therefore, according to the configuration of the present invention, by providing the horizontal deflection circuit separately from the focus voltage generating circuit, the focus voltage can be generated in a parabolic waveform with a relatively simple circuit configuration without deteriorating the linearity of the horizontal deflection current. It can be modulated to

As a result, it is possible to focus not only on the center of the CRT display but also on its corners.

Therefore, the dynamic focus circuit according to the present invention is extremely suitable for application to a display device equipped with a CRT display, such as a television receiver.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a dynamic focus circuit according to the present invention, and FIG. 2 is a system diagram showing a conventional horizontal deflection circuit. 1... Dynamic focus circuit 2... Horizontal output circuit 3... Horizontal deflection circuit 4... High voltage generation circuit 5... Focus voltage generation circuit 18... CRT display 41... Parabolic wave voltage generation Circuit A...Anode electrode B...Focus electrode L3...Horizontal deflection coil Fig. 2

Claims (1)

[Claims] (1) A horizontal deflection circuit that obtains a horizontal deflection current using a horizontal deflection coil; a high voltage generation circuit that generates a voltage to be supplied to the anode electrode of the CRT display; and a focus voltage that generates a focus voltage to be supplied to the focus electrode of the CRT display. a parabolic wave voltage generated from the sawtooth wave voltage obtained in the high voltage generation circuit; is supplied to the focus voltage generating circuit to apply a parabolic wave voltage to the focus electrode.