JPH0771194B2 - Raster distortion correction circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vertical line distortion correction circuit used in a color television receiver or the like.

[Conventional technology]

As is well known, in a color television receiver, a left and right pincushion distortion as shown in FIG. 3 generally occurs in a raster due to the selection of the curvature of the face plate of the cathode ray tube and the magnetic field distribution of the deflection yoke. To correct this, a circuit as shown in FIG. 4 is used. In the figure, Q ₁ and Q ₂ are vertical output transistors, LD is a vertical deflection coil, and the controlled winding L ₂ is connected in series with a horizontal deflection coil (not shown). R ₁ is a DC bias resistor, and R ₂ and C ₁ are high-pass bypass resistors and capacitors.

In such a configuration, the parabola current having a vertical deflection period is superimposed on the control winding L ₁ of the left and right pincushion distortion correction transformer T, which is a saturable reactor, and the inductance of the controlled winding L ₂ is changed to the vertical period. The pincushion distortion is corrected by means of modulating the horizontal deflection current at the upper and lower parts of the screen and increasing it at the center of the screen.

For the raster distortion of the vertical line, the above-mentioned means is sufficient if the anode voltage (hereinafter referred to as Ea) supplied to the cathode ray tube does not change. However, as shown in FIG. 5 (a), when a signal such as a white window pattern appears on a part of the screen, Ea fluctuates as shown in FIG. 5 (b), and as a result, As shown in FIG. 5C, even if the above-described raster distortion correction is performed, the horizontal amplitude causes the raster width to widen in the white window portion, and the vertical line that should originally be the broken line in FIG. 5A. Is distorted like the solid line. This is an unavoidable phenomenon unless some correction means is used as long as the power source impedance for supplying the anode voltage Ea cannot be lowered.

The above correction is not limited to the above-described vertical period parabolic current in the control winding L ₁ of the left and right pincushion distortion correction transformer T,
This can be corrected by passing a current with the same waveform as the Ea ripple voltage. The conventional circuit for the purpose of correction is
Shown in the figure. Input voltages e ₁ and e ₂ as shown in FIG. 7 are applied to the resistors R ₃ and R ₅ , respectively. e ₁ is, for example, a vertical sawtooth wave signal extracted from a vertical output circuit, integrated by a resistor R ₃ and a capacitor C ₂ to create a parabolic voltage e 1 ′, and
Applied to the base of transistor Q ₃ via R ₄ . Also
E ₂ is a ripple detection signal Ea, for example taken from a cathode ray tube of the attachment lugs or the like, via a resistor R ₅ transistor
Applied to the base of Q ₃ . Therefore, the base voltage waveform of the transistor Q ₃ is added to the above-mentioned combined waveform of the vertical parabolic voltage e 1 ′ and the Ea ripple voltage e ₂ via the bias resistor R ₆ as shown by e ₃ in FIG. The obtained DC voltage is superposed. E ₃ (reference voltage correction) This composite voltage is amplified by the transistors Q ₃ and Q _4, a voltage is applied to the control winding L ₁ of the left and right pincushion distortion correction transformer. resistance
R ₇ is the collector resistance of transistor Q ₃ . Then, the drive voltage of the control winding L ₁ generated at the collector of the transistor Q ₄ is integrated by the integrating circuit composed of the resistors R ₉ and R ₈ and the capacitor C ₃ , and is fed back to the emitter of the transistor Q ₃ which is a comparison amplifier. ing.

The reason for such a configuration is that the control winding L ₁ includes an inductance component and a resistance component, and therefore a phase delay occurs in the control current i ₀ flowing in the control winding L ₁ with respect to the applied drive voltage. Therefore, it is necessary to advance the phase of the drive voltage, and the negative feedback is applied through the integrating circuit composed of the resistors R ₈ and R ₉ and the capacitor C ₃ .

[Problems to be solved by the invention]

However, the circuit having the configuration shown in FIG. 6 has the following drawbacks. That is, even if the ideal correction reference voltage e ₃ corresponding to the current waveform originally intended to flow as i ₀ is applied to the base of the transistor Q ₃ , it is compared with the integrated voltage of the voltage applied to the control winding L _1. Since it takes the form of amplification, i ₀ is directly affected by the variations in the constants of resistors R ₈ and R ₉ , and capacitor C ₃ , and there is no guarantee that an ideal current will be obtained, and therefore the variation in correction will be very large. large. Also, in designing circuit constants, R ₉ , R ₈ , and C ₃ must be selected as optimum constants according to the impedance of L ₁ , so there is little freedom to independently determine the DC bias or AC gain, and It impeded the degree of freedom in design. Further, as an adverse effect of the voltage feedback, the impedance change due to the temperature drift of the transformer T is fed back, and the feedback is performed so that the drive voltage can be kept constant, but i ₀ changes. It was

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional circuit, and a raster distortion correction circuit capable of almost eliminating the variation of i ₀ , that is, the correction variation, improving the degree of freedom in design and also improving the temperature drift characteristic. Aim to get.

[Means for solving problems]

The raster distortion correction circuit according to the present invention is provided with a current detection element in series with a vertical line distortion correction transformer such as a left and right pincushion distortion correction transformer, and the voltage generated in the current detection element is used as a feedback voltage and the correction reference voltage. And compare and amplify
The control winding is driven.

[Action]

According to the present invention, the current waveform flowing in the control winding is detected, and it functions as a so-called current feedback type amplifier which uses it as a feedback voltage. Therefore, the circuit operation is stable, and raster distortion correction independent of variations in component constants can be performed. .

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a raster distortion correction circuit according to an embodiment of the present invention. In the figure, parts having the same functions as those in FIG. 6 are designated by the same reference numerals. The features of the circuit shown in FIG. 1 are:
The current detection resistor R ₁₂ is inserted in series with the control winding L ₁ , and the resistor R ₁₀ is inserted between the collector of the transistor Q _{4 and} the emitter of Q ₃ to detect the emitter of the transistor Q ₃ and the detection resistor R. _The point is that a capacitor C ₄ is inserted between ₁₂ and the other circuit configuration is the same as that of FIG. The same applies to the input signals e ₁ and e ₂ .

Next, the operation will be described.

Similarly to the conventional example, the correction reference voltage e ₃ is the integrated waveform (vertical parabolic voltage) e ₁ ′ of the voltage e ₁ , the Ea ripple detection voltage, and the DC voltage applied from the DC power supply Vcc through the resistor R _6. Given as a composite of and. This combined voltage (reference voltage for correction) e3 is amplified by the transistors Q3 and Q4 and applies a voltage to the control winding L1 of the left and right pincushion distortion correction transformers. Then, in order to faithfully flow the same current waveform as this reference voltage waveform to the control winding L ₁ , the voltage generated in the resistor R ₁₂ which is a current detection resistor (feedback resistor) is applied to the transistor Q ₃ via the capacitor C ₄ . Return to the emitter. The above feedback is the negative feedback of the AC component, and this AC component is the capacitor C4.
Since passing to appear at the hot side of the resistor R12 for controlling current detecting AC component of i0 becomes _{i0 (AC) ≒ e 3 /} R 12. In addition, for the feedback of the DC component, the voltage applied to the control winding L ₁ is R ₁₀ ,
And integrating with C _4, R ₁₂ and so as to apply to the emitter of the transistor Q _3. With such a configuration, the direct current component of i0 is the value obtained by dividing the collector voltage of the transistor Q4 by the sum resistance of the control winding L1 of the left and right pincushion distortion correction transformer and the control current detection resistor R12, that is, a i0 (DC) ≒ / ((DC level) -0.6 V of e ₃₎ ((resistance _{L1) + (R 12))} . This is because the resistor R10 and capacitor C4 inserted in the feedback circuit are the elements that make up the integrating circuit, and their values are sufficiently large that they are hardly affected by them and the emitter voltage of transistor Q3 is the collector voltage of transistor Q4. This is because the emitter voltage of the transistor Q3 does not pass through the capacitor C4. As a result, a very stable control current can be obtained.

Also, in terms of design, the resistance of L ₁ >> R ₁₂ , so
The AC gain can be freely changed by selecting R ₁₂ , and the DC gain can also be freely changed by selecting the DC level of the voltage e ₃ by changing the resistor R ₆ , resulting in a large degree of design freedom.

In the above embodiment, the AC component is stabilized by applying the power source feedback, but the DC component is stabilized by the voltage feedback. Here, if the direct current component is also applied to the current feedback, the stability of the circuit can be further improved.
FIG. 2 shows an example thereof.

Without providing a capacitor in the feedback circuit in the second figure, and a DC amplifier configuration, the DC stability of the transistor Q ₃ Vb
Only affected by the temperature drift of e. In order to eliminate the influence, the diode D ₁ is inserted for temperature compensation as shown in FIG. Needless to say, the diode D ₁ is Vc
It is always turned on by the direct current flowing from c to e ₁ or e ₂ and operates only as temperature compensation.

Further, in each of the above-described embodiments, the reference signal is explained as the combined signal of the vertical parabola voltage and the anode voltage ripple detection voltage, but it goes without saying that either of them may be used.

〔The invention's effect〕

As described above, according to the present invention, the current flowing in the control winding of the vertical line distortion correction transformer is converted into a voltage by the detection element,
Since it is used as a feedback signal for comparison and amplification with the correction reference voltage, circuit operation is extremely stable and the degree of freedom in setting is improved, and ideal raster distortion correction is possible without depending on variations in component constants. There is an effect.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a raster distortion correction circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIG. 3 is a diagram showing left and right pincushion distortion in a conventional circuit. FIG. 4 is a conventional circuit diagram for correcting the distortion, FIG. 5 is a diagram for explaining vertical line bending, FIG. 6 is a circuit diagram of a conventional raster distortion correcting circuit, and FIG. It is a waveform diagram. In the figure, T is a vertical distortion correction transformer, L1 is a control winding, and R1 is
Reference numeral 2 is a current detection resistor, and Q3 is a comparison amplification transistor. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A raster distortion correction transformer is provided, a drive voltage according to a correction reference voltage is applied to a control winding of the transformer, and a deflection current flowing in a deflection coil connected to a controlled winding is applied. A raster distortion correction circuit for controlling and correcting raster distortion, comprising a current detection element connected in series with a control winding of the transformer for detecting a current flowing through the control winding, and a current detection element. A raster distortion correction circuit, comprising: a comparison and amplification unit that compares and amplifies a voltage generated in an element and the correction reference voltage and outputs a drive voltage for driving the control winding. 2. The raster according to claim 1, wherein the correction reference voltage is any one of a parabola voltage having a vertical deflection period and a CRT high voltage ripple detection voltage, or a combined voltage thereof. Distortion correction circuit.