KR800000274B1 - Side pincushion correction circuit - Google Patents

Abstract

In a raster correction circuit, impedance in controlled by a parabolic vertical rate waveform (50) to alter the charging rate of a storage capacitor(42) coupled to the rectifier(39) for supplying the vertical operating current. The parabolically varying rectifier current alters the loading of the horizontal transformer(20) and alters the horizontal scanning current at a vertical rate in a manner to correct for side pincushion distortion.

Description

Side Pincushion Distortion Correction Circuit

Figure is a circuit diagram showing a horizontal deflection device including a raster calibration circuit according to an embodiment of the present invention.

The present invention relates to a side pincushion distortion correction circuit for use in a display device such as a television device. The geometric relationship between the beam of the scanning beam or cathode ray tube and the inner surface of the screen being scanned causes raster distortion, also known as pincushion distortion. This distortion is characterized by enlarging the display in the horizontal direction at the top and bottom of the raster relative to the center of the raster. This distortion can be corrected in most cases by modulating the horizontal scan current to the vertical scan ratio.

This modulation is usually in the form of a parabola and, in relation to the horizontal scan current at the center of the raster, causes a maximum reduction in the horizontal scan current at the top and bottom of the raster corresponding to the beginning and end of the vertical sweep line. .

Vertical ratio modulation is affected by the horizontal scan current in several ways. The reactor may be coupled in the circuit with a horizontal deflection coil and may be controlled to change the impedance from vertical ratio to horizontal scan current. The transformer can also be used to make the necessary modulation in circuits with horizontal deflection coils. Recently, the horizontal ratio energy as obtained from the winding of the horizontal output transformer is rectified and this rectified current is used to supply the vertical deflection output stage. At this time, the vertical stage itself loads the horizontal winding so that the horizontal scanning current is modulated by the vertical deflection ratio. While such a device is satisfactory, it is desirable to have a raster calibration circuit that can control modulation to a significant extent.

According to the invention, the raster calibration circuit comprises a line frequency generator, a line frequency output transformer and a deflection winding coupled to the line frequency generator. A power supply comprising a stop is coupled to the winding of the transformer to rectify the abundance energy obtained from the winding. A field ratio generator is coupled to the power supply to obtain the operating current. The active current conducting device is combined with a circuit having a stop value, and in response to a signal derived from a field frequency oscillator, changes the current in the stop value with the field deflection ratio for the transformer load and corrects the pre-current current in the deflection winding by correcting the raster distortion. It provides a variable impedance pathway to change.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The figure shows a horizontal deflection device including a raster calibration circuit according to the invention. Winding 10a of input reactance 10 is coupled between voltage source B + and one terminal of the two-way conductive switch 11.

Winding 10a is coupled to the rectifying coil 13, which is coupled to capacitor 15, which is coupled to one terminal of the second two-way conductive switch 16. The reporting capacitor 14 is coupled between the contacts of the rectifier coil 13 and the capacitor 15 and ground. Switch 16 is also coupled to ground via horizontal deflection winding 18 and S-shaped capacitor 19, and through primary winding 20a and blocking capacitor 21 of horizontal output transformer 20 to ground. The horizontal oscillator 12 is coupled to the gate electrode of one element of the switch 11. Winding 10b of input reactor 10 feeds a gating signal for one element of switch 16 via waveform circuit 17.

Such a circuit is a retrace drive SCR type horizontal deflection circuit described in US Pat. No. 3,452,244. Since the description of the operation of this circuit is unnecessary for understanding the present invention, only by explaining that the horizontal deflection circuit induces the scan current through the horizontal deflection coil 18 and the horizontal ratio energy into the primary winding 20a of the horizontal output transformer 20. Suffice. The horizontal energy consists of a relatively short retrace section and a minor section section.

The winding 20b of the horizontal output transformer 20 supplies a horizontal winding pulse to the conventional high voltage rectifier and the multiplier 22 to generate a positive voltage of about 25,000V to excite the ultra high voltage terminal of the television receiver tube.

The remainder of the circuit in the figure comprises a circuit according to the invention for correcting pincushion distortion with a horizontal scan current.

Winding 20c of transformer 20 is connected to ground via a series connection of capacitor 23 and resistor 24, diode 25 and capacitor 26 of the polarity shown, and variable inductance 27. The same terminal of winding 20c is coupled through diode 28 and the collector-emitter path of transistor 29 is coupled to ground via a current limiting resistor 30. A bias circuit consisting of resistor 3l and potentiometer 32 is coupled between the collector of transistor 29 and the base electrode.

The other terminal of winding 20c is coupled via a series connected collector-emitter path of transistors 43 and 44. Transistors 43 and 44 constitute the output stage of the vertical deflection amplifier. The complementary symmetrical output stage is driven by a vertical deflection generator and driver 5. The vertical ratio deflection current is routed through the DC blocking capacitor 46 to the vertical deflection coils 47 and 48, where it is connected to ground via a current sampling feedback resistor 49.

The upper terminal of the winding 20c is connected to one terminal of the accumulation capacitor 42, and the other terminal is grounded through the parallel coupling of the diode 39, the capacitor 40 and the resistor 41. This terminal of capacitor 42 is also grounded through the parallel coupling of resistor 38, potentiometer 36, and capacitor 37.

The tab of the variable resistor 6 is connected to the base electrode of the transistor 29 through the resistor 33. A phase transfer circuit composed of a capacitor 34 and a potentiometer 35 connected in series is coupled between the base electrode of the transistor 29 and the junction of the feedback resistor 49 and the vertical deflection winding 48.

In operation, diode 25, inductance 27, capacitor 42 and diode 39 operate as rectifiers and accumulators for horizontal ratio energy in winding 20c. The aspect ratio energy is represented by waveform 54. Diode 25 is polarized to rectify the sweep line portion of waveform 54.

The rectified current is charged and accumulated in the capacitor 42. Diode 39 prevents the accumulation of positive charge on the lower terminal of capacitor 42.

Capacitor 26 acts as an RF bypass capacitor for rectifier 25. Capacitor 23 and resistor 24 act as damping elements to prevent oscillation in the circuit. Diode 28 acts to block the constant voltage from the collector of PNP transistor 29. Capacitor 34 and resistor 35 form a phase transition circuit that acts to differentiate the waveform 51 appearing across sampling resistor 49 for the following description. Waveform 53 at the vertical deflection ratio appears at the junction of capacitor 42 and diode 39. This waveform indicates that the vertical output transistor 43 is in a conductive state during the later half period of each vertical sweep line interval. The circuit consisting of capacitor 37, resistor 38, capacitor 40 and resistor 41 constitutes an integrated circuit for forming a parabolic 50 from waveform 53. This parabolic waveform is coupled to the base of transistor 29 via a resistor 33. Adjustment of rheostat 36 determines the amplitude of parabolic waveform 50 applied to the base of transistor 29.

Transistor 29 and its associated control circuit act as a variable impedance by shunting rectifier 25 and inductance 27 to shunt some rectifier current, so the rectifier 25 current changes parabolic at the vertical deflection ratio. Parabolic 50 coupled to the base of transistor 29 can very strongly challenge the transistor at the beginning and end of the vertical sweep line segment, indicated by the negative portion of the waveform. During the vertical section, when the conduction state of transistor 29 is most active, low impedance appears in the horizontal specific current, such as inductance 27, which represents a relatively high impedance in the bypassed horizontal ratio energy.

This causes a faster charge current to flow into capacitor 42 to charge capacitor 42. This fast charge flow is above and below the raster, resulting in a horizontal scan current envelope such as waveform 52. It can be seen that the modulation envelope of waveform 52 is in the vertical deflection ratio and the amplitude of the horizontal scan current is smaller in the portions appearing at the top and bottom than the center of the scanned raster. Therefore, the side pincushion distortion is corrected by varying the horizontal scanning current parabolic with the vertical deflection ratio. Inductance 27 adjusts the vertical supply voltage.

The purpose of the phase shift circuit, which consists of a resistor 35 and a capacitor 34, is to vary the correction amount for the upper portion of the raster by differentiating the by-pass portion of the vertical ratio sawtooth waveform 51 and adding it to the parabolic waveform 50. The change in potentiometer 35 performs an abnormality and a variable calibration function.

It should be noted that in the absence of transistor 29 and its subsidiary circuits, the parabolic vertical ratio to horizontal energy is slightly corrected by the charge and discharge of the accumulation capacitor 42. However, by adding a shunt transistor 29 and its subcircuits to effectively shunt the relatively high impedance 27, the vertical ratio modulation of the horizontal energy is made larger. Moreover, by adding a shunt passage including transistor 29, this becomes the effective amount of the rectifier current controlled in a parabolic manner. At the vertical deflection ratio, the load of winding 20c is reflected to winding 20a so that more rectified current is converted in transformer 20 instead of through deflection winding l8 to S-type and accumulating capacitor 19 during the rectifying portion of each horizontal deflection period.

Although specific apparatus have been described above, the above-described embodiments can be easily modified in various ways. For example, a ghost rectification can be obtained by inverting winding 20c instead of the subline rectification. Moreover, other deflection circuits other than the SCR type may be used, and the vertical deflection circuit may be any other suitable type rather than complementary symmetry.

As another embodiment, the cathode of diode 28 may be connected to the anode of diode 25 instead of the cathode of diode 25, or may control the current via rectifier diode 25 by shunting inductance 27.

The following are values of circuit elements in the raster calibration circuit portion of the drawing.

Claims (1)

As described herein and shown in the figures, a vertical deflection generator, a horizontal deflection generator for generating a horizontal ratio current, and a horizontal deflection generator coupled to the horizontal deflection generator to receive a horizontal specific current from the horizontal deflection generator for scanning. In a side pincushion distortion correction circuit comprising a horizontal deflection winding, an impedance device, and a semiconductor impedance device having a control electrode, the main conductive paths of the semiconductor impedance device are forward and reverse in particular during each horizontal deflection period. A coupling device for coupling the semiconductor impedance device and the impedance device to the deflection winding to bias and provide a horizontal ratio current through the horizontal current path, and a main conduction of the semiconductor impedance device forward biased; Has a passageway and the conduction alters the pincushion distortion To the male and vertical deflection generators to represent control signals in response to the horizontal and vertical ratio signals for controlling the semiconductor impedance device to conduct during a portion of each deflection period in case of a change in the vertical deflection ratio. And a control device coupled to the horizontal and vertical ratio signal sources guided from the control electrode to the side pincushion distortion correction circuit.

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