JP3240727B2 - Image distortion correction device for flat cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat type cathode ray tube image distortion correcting apparatus which corrects image distortion by modulating a power supply of a horizontal deflection circuit.

[0002]

2. Description of the Related Art FIG. 3 shows a flat cathode ray tube (flat type CR tube).
T) 1 is shown. In the figure, 1a is a neck portion provided with an electron gun (not shown), 1b is a funnel portion,
c is a screen panel, 1d is a front panel, and 1e is a phosphor screen formed on the screen panel 1c. The screen panel 1c and the front panel 1d are formed of transparent glass. The phosphor screen 1e is inclined at a relatively small angle with respect to the center axis of the electron gun.
Is observed from the front panel 1d side substantially perpendicular to the central axis of the electron gun.

In such a flat cathode ray tube 1, inverted trapezoidal distortion (keystone distortion) is generated due to its structure. That is,
The horizontal deflection scanning is performed from the upper portion to the lower portion of the fluorescent screen 1e. However, since the upper deflection angle θ1 and the lower deflection angle θ2 are different, the horizontal deflection scanning approaches the lower portion when performing horizontal deflection scanning with a constant deflection power (current). As a result, the scanning amplitude becomes smaller, and an inverted trapezoidal distortion occurs (see FIG. 4).

In order to correct the inverted trapezoidal distortion, it is necessary to dynamically increase the deflection current Ipp as the fluorescent screen 1e is scanned from the upper part to the lower part. here,
The power supply voltage eo and the horizontal deflection current Ipp of the horizontal deflection circuit include:
The inductance of the horizontal deflection coil (H · DY) is Ly,
Assuming that the horizontal scanning feedback is Ts, there is a relationship of eo = Ly (Ipp / Ts) = K · Ipp. Here, K = (Ly / Ts). That is, in order to dynamically increase the horizontal deflection current Ipp, it is understood that the power supply voltage eo needs to be dynamically changed. In order to realize this, a so-called power supply modulation method in which a power supply voltage is modulated by a sawtooth signal having a vertical period is generally widely used.

FIG. 5 shows a conventional image distortion correction apparatus for correcting an inverted trapezoidal distortion by modulating a power supply voltage with a sawtooth signal as described above. This example is composed of a SEPP output circuit. In the figure, a terminal 2 is supplied with a vertical period sawtooth signal. The sawtooth signal is amplified by the differential amplifier 3 and supplied to the power supply modulation amplifier 4 as a modulation control signal.

The output side of the power supply modulation amplifier 4 and the differential amplifier 3
And a DC feedback circuit 5 for stabilizing the bias.
And an AC feedback circuit 6 including a resistor R and a capacitor C for shaping the correction waveform. The diode Di and the capacitor Ci of the power supply modulation amplifier 4 constitute a bootstrap circuit often used in a general vertical deflection circuit and the like, and improve the utilization rate of the power supply voltage + B.

A power supply voltage + B is applied to the output side of the power supply modulation amplifier 4.
Is modulated by a sawtooth signal with a vertical period.
This voltage is supplied to the horizontal deflection circuit 7 as power. 8
Is a horizontal deflection coil.

[0008]

The image distortion correction apparatus shown in FIG. 5 has a problem that a correction remains at the bottom of the screen (see FIG. 6). The reason why the uncorrected portion occurs is that although the horizontal deflection current needs to be increased non-linearly due to the magnetic field of the deflection yoke and the curvature of the phosphor screen, the horizontal deflection current is increased linearly in the example of FIG. Because it is.

In view of the above, the present invention provides an image distortion correcting apparatus for a flat-type cathode ray tube which can satisfactorily correct inverted trapezoidal distortion without occurrence of residual correction.

[0010]

According to a first aspect of the present invention, there is provided a flat type cathode ray tube image distortion correcting apparatus for correcting image distortion by modulating a power supply of a horizontal deflection circuit with a power supply modulation circuit. The sawtooth signal and the second half of the vertical period
The sawtooth signal is synthesized at a predetermined ratio and supplied to the power supply modulation circuit as a modulation control signal.

According to a second aspect of the present invention, there is provided a flat type cathode ray tube image distortion correcting apparatus for correcting image distortion by modulating a power supply of a horizontal deflection circuit with a power supply modulation circuit, wherein the power supply modulation circuit comprises a modulation control signal.
Amplifying a vertical period sawtooth signal as a signal
Amplifies the output of the transistor and the first transistor
And the second to supply the output to the horizontal deflection circuit as power.
And a transistor, as a load of the first transistor.
The first CR series circuit is connected and the second transistor
A second C is connected between the output side and the input side of the first transistor.
R series circuit is shall be connected. In addition, the first tiger
Instead of a vertical period sawtooth signal, the transistor
Occurs in the second half of the vertical period and the first sawtooth wave signal in the vertical period
And a second sawtooth signal to be synthesized at a predetermined ratio.
The resulting signal is amplified as a modulation control signal .

[0012]

In the first invention, a modulation control signal is obtained by synthesizing a first sawtooth signal having a vertical cycle and a second sawtooth signal generated in the latter half of the vertical cycle at a predetermined ratio. In the horizontal deflection circuit, the horizontal deflection current in the lower part of the screen is more emphasized, so that it is possible to satisfactorily correct the inverted trapezoidal image distortion without generating the remaining correction in the lower part of the screen.

In the second invention, the first CR serial circuit is provided.
The second half of the vertical period sawtooth signal is emphasized on the road
At the same time, the second CR series circuit works as an AC feedback circuit
To increase the operating efficiency of the first CR series circuit Te, horizontally polarized
Circuit, the horizontal deflection current at the bottom of the screen is emphasized.
Inverted trapezoid without any remaining correction at the bottom of the screen
Image distortion can be satisfactorily corrected .

Further, the first control signal of the vertical period is used as the modulation control signal .
Sawtooth wave signal and the second
A sawtooth signal synthesized at a predetermined ratio is supplied.
The horizontal deflection circuit at the bottom of the screen
The flow is emphasized, causing a residual correction at the bottom of the screen
And the image distortion of the inverted trapezoidal shape can be corrected well. In addition,
Of the first and second sawtooth signals in one CR series circuit.
The joint is smoothed and the second CR
The series circuit works as an AC feedback circuit to
In order to increase the efficiency of road operation, the seams are conspicuous and the image
It can prevent being unsightly .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, portions corresponding to those in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, reference numeral 100 denotes a vertical deflection output circuit. A drive signal is supplied to a base of the vertical output transistor 111 from a drive circuit (not shown). The emitter of this transistor is grounded, and its collector is connected to a power supply terminal 104 via a vertical deflection coil 102 and a resistor 103. The vertical deflection coil 102 has
A series circuit of a resistor 105 and a capacitor 106 is connected in parallel.

In parallel with the resistor 103, a variable resistor 107 for adjusting the vertical amplitude and a variable resistor 108 for adjusting the correction amount of the inverted trapezoidal distortion (keystone distortion) are connected.
The mover of the variable resistor 107 is connected to the power supply terminal 104 via a series circuit of the resistor 109, the capacitor 110, and the resistor 111. A signal obtained at a connection point between the capacitor 110 and the resistor 111 is fed back to a pre-drive circuit (not shown) to correct linearity.

Reference numeral 200 denotes a sawtooth signal generation circuit. The base of the transistor 201 is a capacitor 202
Through the resistor 109 of the vertical deflection output circuit 100 and
Connected to the connection point of the capacitor 110, the transistor 2
The base of 01 is supplied with a sawtooth signal of vertical period (illustrated in FIG. 2A). The base of the transistor 201 is connected to a power supply terminal 204 via a resistor 203, the emitter is connected to the power supply terminal 204 via a resistor 205, and the collector is grounded via a resistor 206.

In the transistor 201, a sawtooth signal having a vertical cycle is clipped at a predetermined threshold level, and its collector has a sawtooth signal corresponding to the latter half of the vertical cycle (hereinafter referred to as a "pulse sawtooth signal").
(Shown in FIG. 2B). In this case, by changing the resistance values of the resistors 203 and 205, the threshold level can be adjusted to adjust the period To of the pulsed sawtooth signal. Further, by changing the resistance values of the resistors 205 and 206, the amplitude Vo of the pulsed sawtooth signal can be adjusted.

Reference numeral 300 denotes a power supply modulation circuit. The base of the transistor 301 constituting the amplifier is the resistor 30
2, and connected to the mover of the variable resistor 108 of the vertical deflection output circuit 100 via the capacitor 303. A sawtooth signal having a vertical period is supplied to the base of the transistor 301. The amplitude of the sawtooth signal is adjusted by moving the mover position of the variable resistor 108.

The emitter of the transistor 301 is a resistor 3
In addition to being grounded via the signal line 04 and connected to the collector of the transistor 201 of the sawtooth signal generating circuit 200 via the resistor 207, a pulsed sawtooth signal is supplied to the emitter of the transistor 301.

The collector of the transistor 301 is a resistor 3
The power supply terminal 306 is connected to a power supply terminal 306 to which a positive DC voltage + B1 (for example, +50 V) is supplied via the power supply terminal 05, and is connected to the base of a transistor 307 constituting an amplifier.
The collector of this transistor 307 is a positive DC voltage + B
2 (for example, +18 V) is connected to the power supply terminal 308 to which power is supplied. A series circuit of a variable resistor 309 and a resistor device for AC feedback and capacitor for emitter DC feedback of the transistor 307 (horizontal amplitude adjustment) (CR series
Circuit) It is connected to the base of the transistor 301 via a parallel circuit of 310.

The collector of transistor 301 is connected to the collector of the transistor 307 through a series circuit (CR series circuit) 311 of the resistor device and the capacitor. Then, a voltage obtained at the emitter of the transistor 307 is supplied to the horizontal deflection circuit 7 as power.

In the above configuration, the transistor 301
The base is supplied with a sawtooth signal having a vertical period, and its emitter is supplied with a pulsed sawtooth signal, so that a composite signal of the two sawtooth signals is obtained at its collector. This composite signal has a signal in which the latter half of the vertical period sawtooth signal is emphasized, and the joint is smoothed by the smoothing process by the CR serial circuit 311. Note that the above-described CR series circuit 310 for AC feedback includes a CR series circuit 3
11 has a role of improving the operation efficiency.

Therefore, the base of the transistor 307 is supplied with a composite signal in which the latter half of the vertical period sawtooth signal is emphasized.
Is modulated and obtained at the emitter of the transistor 307. Then, the modulated voltage is supplied to the horizontal deflection circuit 7 as power. Thereby, in the horizontal deflection circuit 7, the horizontal deflection current Ipp in the lower part of the screen is more emphasized, so that it is possible to satisfactorily correct the inverted trapezoidal image distortion without generating the remaining correction in the lower part of the screen. it can. FIG. 2C shows the horizontal deflection current Ipp.

Note that, in the example of FIG.
In addition to the above, a power supply terminal 308 is provided, and + B2 <+ B1 is set in order to increase the power utilization rate. Further, in the example of FIG. 1, a CR series circuit 311 transistor 30
7 is connected between the base and the collector, but may be connected in parallel with the load resistance (resistor 305) of the transistor 301. In that case, it is necessary to increase the breakdown voltage of the capacitor. In addition, CR series circuit for AC feedback
Road 310, so in order to increase the operating efficiency of the CR series circuit 311, CR series circuit 310 as long as sufficient operating efficiency of the CR series circuit 311 may be omitted.

In the above-described embodiment, the transistor 301 of the power supply modulation circuit 300 combines the vertical sawtooth signal with the pulse-like sawtooth signal, so that the collector of the transistor 301 outputs the vertical sawtooth signal. Although a signal in which the latter half is emphasized is obtained, even if a pulsed sawtooth signal is not supplied to the emitter of the transistor 301, the operation of the CR series circuit 311 causes the collector of the transistor 301 to have a vertical period sawtooth signal. Can be obtained in the latter half of the signal.
This is because a sawtooth signal having a vertical period is obtained at both ends of the resistor constituting the CR series circuit 311 and a parabolic wave signal having a vertical period is obtained at both ends of the capacitor, and these signals are combined. . And such C
The operation efficiency of the R series circuit 311 is also the CR series circuit for AC feedback.
It will be enhanced I'm on the road 310.

As described above, even if a pulsed sawtooth signal is not supplied to the emitter of the transistor 301, the CR
By the operation of the series circuit 311, a signal in which the latter half of the vertical period sawtooth signal is enhanced can be obtained at the collector of the transistor 301, whereby the horizontal deflection current Ipp in the lower part of the screen is enhanced in the horizontal deflection circuit 7. As a result, it is possible to satisfactorily correct the inverted trapezoidal image distortion without causing any remaining correction at the bottom of the screen.

[0029]

According to the first aspect of the present invention, a modulation control signal is obtained by synthesizing a first sawtooth signal having a vertical cycle and a second sawtooth signal generated in the latter half of the vertical cycle at a predetermined ratio. In the horizontal deflection circuit, the horizontal deflection current in the lower part of the screen is more emphasized, so that the inverted trapezoidal image distortion can be satisfactorily corrected without causing the correction remaining in the lower part of the screen.

According to the second invention, the first CR series circuit
When the second half of the vertical period sawtooth signal is emphasized by
In both cases, the second CR series circuit works as an AC feedback circuit
To increase the operation efficiency of the first CR series circuit , horizontal deflection
The circuit emphasizes the horizontal deflection current at the bottom of the screen,
Inverted trapezoidal shape without any remaining correction at the bottom of the screen
Image distortion can be corrected well.

Also, the first control signal of the vertical period is used as the modulation control signal .
Sawtooth wave signal and the second
A sawtooth signal synthesized at a predetermined ratio is supplied.
The horizontal deflection circuit at the bottom of the screen
The flow is emphasized, causing a residual correction at the bottom of the screen
And the image distortion of the inverted trapezoidal shape can be satisfactorily corrected. In addition,
Of the first and second sawtooth signals in one CR series circuit.
The joint is smoothed and the second CR
The series circuit works as an AC feedback circuit to
In order to increase the efficiency of road operation, the seams are conspicuous and the image
It can be prevented from becoming unsightly .

[Brief description of the drawings]

FIG. 1 is a connection diagram showing one embodiment of an image distortion correcting apparatus for a flat type cathode ray tube according to the present invention.

FIG. 2 is a diagram showing waveforms at various points in the example of FIG.

FIG. 3 is a plan view and a side view showing a flat cathode ray tube (flat CRT).

FIG. 4 is a diagram for explaining inverted trapezoidal distortion (keystone distortion).

FIG. 5 is a connection diagram showing an example of a conventional image distortion correcting apparatus for a flat-type cathode ray tube.

FIG. 6 is a diagram for explaining remaining correction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat type cathode ray tube 7 Horizontal deflection circuit 8 Horizontal deflection coil 100 Horizontal deflection output circuit 200 Saw wave signal generation circuit 300 Power supply modulation circuit

Claims (3)

(57) [Claims] An image distortion correcting apparatus for a flat-type cathode ray tube which corrects image distortion by modulating a power supply of a horizontal deflection circuit with a power supply modulation circuit, comprising: a first sawtooth wave signal having a vertical cycle and a second half of the vertical cycle. An image distortion correcting apparatus for a flat-type cathode ray tube, wherein a generated second sawtooth signal is synthesized at a predetermined ratio and supplied to the power modulation circuit as a modulation control signal. 2. A flat cathode ray tube image distortion correction apparatus for correcting image distortion by modulating a power supply of a horizontal deflection circuit with a power supply modulation circuit, wherein the power supply modulation circuit is constituted by an amplifier, and an input terminal of the amplifier is provided. Supplies a modulation control signal, connects a first integrating circuit as a load of the amplifier,
Connecting a second integrating circuit between the input and output terminals of the amplifier,
An image distortion correcting apparatus for a flat type cathode ray tube, wherein a signal obtained at an output terminal of the amplifier is used as a power supply of the horizontal deflection circuit. 3. The amplifier comprises a first transistor for amplifying a voltage, and a second transistor for current amplifying an output of the first transistor, and a load resistor connected to a collector of the first transistor. In parallel with the collector of the second transistor.
3. The circuit according to claim 2, wherein the first integration circuit is connected between bases, and the second integration circuit is connected between an emitter of the second transistor and a base of the first transistor. An image distortion correcting device for a flat-type cathode ray tube according to the above.