DE1273572B - Raster output circuit for correcting the pincushion distortion in the vertical deflection - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H04n

German class: 21 al - 35/20

Number: 1273 572

File number: P 12 73 572.7-31 (N 26178)

Filing date: February 6, 1965

Opening day: July 25, 1968

The invention relates to a raster output circuit for correcting the pincushion distortion component the vertical deflection which includes amplifiers fed with sawtooth raster deflection input signals and means in which these raster deflection signals are mixed with the line frequency by mixing be modulated by line frequency input signals with line frequency.

Such a circuit is known from German patent specification 1023 078. There, the so-called potentiometer principle is used to correct the vertical pincushion distortion (north-south pincushion distortion), ie a coil that changes its inductive impedance with the line frequency is connected in parallel to the raster deflection coils . However, this principle cannot be implemented in practice. Due to the low frequency of 50 or 60 Hz of the vertical deflection, the raster deflection coils have an ohmic resistance value R which is of the same order of magnitude or more often than the effective inductive impedance (L) of these deflection coils. If a changing coil is now connected in parallel to the raster deflection coils, this has hardly any influence if R is large compared to L , or an undesirable phase shift results if R is of the same order of magnitude as L.

These disadvantages are avoided if it is ensured that the correction current is at line frequency is already added to the sawtooth-shaped raster deflection before this total current is fed to the raster deflection coils. This is achieved if, according to the invention, two raster deflection output amplifiers are connected in series and form a B push-pull stage and if the deflection coils are connected to an output terminal of the mentioned push-pull circuit via a tuning capacitor, which has such a value that it, together with the inductance of the deflection coils mentioned forms a series resonant circuit practically matched to the line frequency and the is bridged by shunt means for the sawtooth grid currents.

It should be noted that arranging the tuning capacitor in series with the Rasterablenkspulen the The advantage is that the shape of the supplied signals with the line frequency is practically irrelevant will. The series resonant circuit formed in this way and tuned to the line frequency ensures that a sinusoidal current with line frequency is formed, which is sufficient for the desired parabolic current is approximated.

Raster output circuit for correcting the
Pincushion distortion in the vertical deflection

Applicant:

N. V. Philips' Gloeilampenfabrieken,

Eindhoven (Netherlands)

Representative:

Dipl.-Ing. E.-E. Walther, patent attorney,

2000 Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Briand Ernest Attwood,

South Croydon, Surrey (UK)

Claimed priority:
Great Britain 10 February 1964 (5465),
dated October 30, 1964

as The invention is based on the drawings for example explained in more detail. It shows

F i g. 1 the distorted horizontal grid lines as well as the line-frequency components that lead to Corrections to these distorted lines are needed, F i g. 2 the total raster deflection current resulting from the addition (mixture) of a sawtooth-shaped raster deflection current and parabolic-shaped Line streams is composed,

F i g. 3 shows a first embodiment with two Tube modulators,

F i g. 4 shows a second embodiment with an in Series push-pull output stage, being a combination of a pnp-type transistor and a npn type transistor is used,

F i g. 5 a first variety and

F i g. 6 shows a second variant of the embodiment according to FIG. 4th

Suitable deflection coils for a 90 ° masked color display tube usually give about 8% pincushion distortion of the horizontal scan lines. Devices for the necessary correction of vertical deflection make use of a symmetrical curved waveform, their Amplitude decreases to zero and its phase reverses in the middle of a raster image period. this is illustrated in more detail in FIGS. 1 and 2 of the schematic drawings.

809 587/391

3 4

Fig. 1, (6) shows the distorted horizontal raster. of an npn transistor T ₁ with a pnp-type transil lines. To correct the same, the raster interference T _{2 is used} in the push-pull circuit. The deflection current shown is a curved (preferably parabo control stage is an emitter follower in which an internal) line frequency component [F i g. 1, (α) and transistor T ₀ and a charging circuit R ₇ , C ₉ with a (c)] introduced, the phase of the parabola of the 5 auxiliary resistor R _{8 being} used. The schema distortion is opposite. This phase must act in table with S designated means as a switch in the middle of a raster image period change by 180 °, parallel to the charging capacitor C ₉ , and this because the distortion in the lower half of the image in the mean z. B. from a blocking oscillator beder the upper half of the picture is opposite. By standing (in this case it can be coupled for direct current via measurement of the degree of distortion via the io a diode, as it is described in the British whole image scanning the required degree of patent specification 935 722), parabolic correction i _m , and the resul- Die at the base electrodes of the transistors T ₁

The modulation envelope is shown in FIG. 2 with and T ₂ applied bias can be referred to as usual E _m . Although parabolic correction is ideally removed from a tapped resistance, it has been shown by experiment that a sinusoidal correction can be applied, which correction between the collector electrode can also be satisfactory. and the emitter feeder HT lies. When a

A first embodiment is given in FIG. 3. DC coupling with control transistor T ₀ present-In this figure the tubes F _{& 1} and F ₀₂ are in the, this means that if the capacitors C _{10 are} series connected amplifiers, the push-pull B and C _{11 are} omitted to form the mentioned level. L _y is the vertical deflection coil of a 20 base electrode no special bias magnetic deflection system. Needs to be for the sake of convenience.

it was assumed that the grid and the row C ₉ are connected to the positive supply voltage line

frequencies are 50 Hz or 15 kHz. (Earth) connected via the resistor R ₈ , the one

When looking at the first half of a very fast pulse during the setback, maximum correction is required at the beginning and at 35 should testify in order _{to block T 2} quickly, and no correction is necessary at the end of this half-period either. acts as a current feedback path from the output. A sawtooth-shaped control voltage is applied to the linearity of the generated sawtooth-shaped input terminals t _{f ±} and t _{f2 of} the tubes F ₆₁ and current.

F _{& 2} created. A parabolic or more or The capacitor C ₁₃ is a large, equally impulsive waveform with a line current blocking capacitor, which the same radio frequency is met at the input terminals of this tion as the corresponding capacitor placed in tubes. F i g. 3. A diode D ₁ and a capacitor C ₂ are

From the example according to FIG. 3 it can be seen that added to the circle to allow a quick return with only two output tubes F ₆₁ and F ₆₂ one blow. These additional parts are not essential to the circuit for raster correction of the pillow register, since a quick setback is also achieved. can be achieved by other methods; you can z. B.

As shown, a direct current blocking supply voltage _{value can be applied to a suitable level capacitor C 0 in} order to increase the need.

A quick setback results from the fact that

however, this is not essential. 40 on the one hand (a) the deflection coils L ₁ , during the

The tuned series circuit consists of deflection kickback to a frequency equal to the rewinding L _y and a tuning capacitor C _ys beating period, z. B. about 1 kHz, tuned; in connection with a shunt coil L _by . this is done with the aid of a capacitor C ₁₂ : this is provided because the capacitor C _ys one end of the scan is C ₁₂ too large to noticeably represent the impedance that is too high for the raster frequency component of the coils to the line frequency .), but a diode D _{1 is also available.}

The use of pentodes offers the advantage of being able to bypass C ₁₂ and therefore _{allowing g 3} electrodes to pass through for the pulse-shaped or para- sawtooth component, and other bole input signals are available simply multiply mixing the line and 50 is high enough to ensure that the reverse raster frequency signals are possible. This switching of the coil current is completed in less than 1 ms, however, has the disadvantage that the oscillation per tube is relatively high after the first half sinusoidal peak current is required.

(eg 300mA), and in the case of the upper tube F ₆₁ The deflection coils L _y usually consist of

is only half of the _{two parts for the screen or g 2} grid 55. Can be used for a color receiver with an available supply voltage. 90 ° deflection angle can convert these two parts into

These problems can be connected by using series, with their total Transistors instead of tubes are overcome, and the ohmic resistance is about 50 ohms. In the FIG. 4 shows one of the deflection values taken up by the load in the circuit according to FIG. 3 A transistor circuit in connection with a 60 output (e.g. 1.73 watts) would require a simple control stage. Supply voltage of z. B. 70 volts and a peak

The control stage, which has other shapes or to use breakaway kickback voltage of 120 volts. It can be left with, if transistors are used with high regard to the amplification during the kickback, supplies a single relatively high peak voltage input control terminal t _f a single sawtooth 65 it is therefore preferable to parallel the coils L _y to a shaped control pulse, since levels are switched off, whereby the necessary supply voltage to the opposite sign (as with t _fl and t _f2 in about 36VoIt and the peak voltage from T ₂ to Fig. 3) is not necessary because of the use of only 60 volts (the Transistor T ₁

5 6

only needs the voltage of the supply voltage from a raster image period is conductive. The gal-

hold, d. H. in this example, ends of the diodes connected to one another up to a maximum

mum of 36 volts). are via a single terminal t _L with a line

The line pulses are connected via a line frequency frequency source; such a source can

Input terminals t _L the emitter electrodes of the 5 be a coil, like the coil L ₁₀ and L ₁₁ after

Transistors T ₁ and T ₂ from the flyback transformer F i g. 4th

windings L ₁₀ and L ₁₁ supplied. Exactly as in the previous examples, the desired modulus is not necessary to apply lation envelopes in a very simple and too parabolic or sinusoidal line frequency manner, regardless of the input input signals. However, it would be possible to determine the characteristics of the transistors T ₁ and T ₂ .
A parabolic input signal to the booster. It will be noted that the line frequency capacitor of a conventional line deflection circuit can be taken from input terminal t _x for the two diodes, but because, as here, two inputs have the same sign, so that a single verse signals of opposite phase are necessary Connection with the booster capacitor is sufficient if such a solution is more expensive because the booster 15 uses a parabolic input signal instead of an impulse capacitor in two series-connected condenser-shaped line input signals with one for alternating current to earth should be laid. R ₁₅ and R ₁₆ are attached in such a way that the connection would have to be divided. line signal voltages are developed for them

In the circuit according to FIG. 4 will be as a result of the can. R _{16 also} has a second function,

Non-linearity of the transistor input characters - 20 because the voltages developed across R ₁₆ and A ₁₃

ristiken the line frequency input signals from L ₁₀ (in the case of D ₃ ) and to R ₈ (in the case of D ₂ )

and L _{11 are} mixed multiplicatively (used with the sawtooth on, the diodes D ₂ and D _{3 are}

the base electrodes). Below is a sentence that line signals with the correct

practical values of individual parts suitable for an amplitude are available at any time.

Circuit according to FIG. 4 when used in a 25 It has been found that the diode type is not

625-line television receiver. is critical because in the choice of the necessary shape

_. _m , »", _m , ".. ,," every characteristic freedom exists.

Transistor T ₀ Mullard-Type AC127 _Another circuit allows two

transistor I ₁ Ub.-lyp 2 JN I486 line frequency input signals opposite

Transistor T ₂ .. Mullard type OC 28 _{3o use} sign, which z. B. one in two

High voltage HT -36 volt _{parts split} booster capacitor, as mentioned above,

^{Dl0de D} i Mullard type OA10 _{or z} ⁵ _{wd windings5 like the} coils L ₁₀ and L ₁₁

These elements form (j _er Fig. 4, can be seen. In this

Raster deflection coils L _y

Inductance L _by

Capacitor C

ys

together form a case on the required mixture can by means of the line frequency ₃₅ off two carried out with R ₈ connected diodes, as in tuned row F i g. 6, the sliding contact of R kei ld k

only effective as modulation amplitude control

Resistance R _{6 is} 3.3 Ω. In this case, line signal voltages

Resistance R ₇ 15 kΩ (applied to tL _a and tL _b ) developed at R ₁₈ and JR ₁₉ ,

Resistance R ₈ about 4 Ω 4o and the voltage developed at R ₈ is used to

Resistor R ₉ about 680 Ω voltage used by diodes D ₂ and D ₃ , so that

Resistors R ₁₀ and A ₁₁ ... each 5 Ω line signals with the correct amplitude for each

Resistors R ₁₂ and i? ₁₃ ... each 2.2 Ω time are available.

Resistance R _u 2.7 Ω Compared to F i g. 5 this circuit offers the

Capacitor C ₉ 8 μΡ 45 advantage of a slightly better symmetry, however

Capacitors C ₁₀ and C ₁₁ each 500 μΡ with two line frequency input signals opposing _{capacitor C 12} 2 μΡ set sign required.

Capacitor C ₁₃ 1000 μΡ With the circuit according to F i g. 6, the buffer windings L ₁₀ and L ₁₁ 1 turn at row level T ₀ , R _{9 can be} omitted and

transformer 50 binding of the connection point of R ₇ and C ₉ with

Kickback time 800 μβ C ₁₀ and C _{11 are} replaced. In this case it will be

the line input signals via C _{9 to} the basic electrical

Modifications of the circuit according to FIG. 4 are fed to the transistors T ₁ and T ₂ ,
obtained when the non-linear characteristics in the circuits of FIGS. 5 and 6, the necessary modulation envelope will be used by diodes in order to achieve the necessary mixture 55, instead of being based on the fact that the opposite of the multiplicative mixture, which in the input characteristics of the output transistors in the circuits according to FIGS. 3 and 4 applied over the desired operating range the correct one is achieved by additive mixing,
have nonlinear shape. In the circuits according to FIGS. 5 and 6 (and

The F i g. 5 and 6 show such circuits, at 60 also in the circuit according to FIG. 4) means the

where the same reference numerals for corresponding parts presence of a coil L _by for bridging the

be used. For the sake of simplicity, the 50-period sawtooths are used as

Line input circles labeled _{T 1.} Primary winding of a transformer can serve,

In the circuit according to FIG. 5 is the waveform of its secondary winding to the base electrode of the voltage at R ₈ such that the diode D ₂ would be fed back to the transistor T _0. The first half is rend a raster image period current use of such a feedback to Erleitend, and the voltages at R ₁₃ and R ₁₆ are livering a good scan linearity is quite useful, such that the diode D ₃ during the second half as simple correction networks due from the-

Essence of the usual grid output choke coil used in Α operation or the corresponding one Transformer is difficult to use.

Claims (7)

Patent claims: 1. Raster output circuit for correcting the pincushion distortion component of the vertical deflection, which contains amplifiers to which sawtooth-shaped raster deflection input signals are fed, and means in which these raster deflection signals are modulated with the line frequency by admixing line frequency input signals with line frequency, characterized in that two raster deflection Power amplifiers (F ₀₁ , F ₀₂ or T ₁ , T ₂ ) are connected in series and form a B push-pull stage and that the deflection coils (L _y ) with an output terminal of the mentioned push-pull circuit (F ₀₁ , F ₆₂ or T ₁ , T ₂ ) are connected via a tuning capacitor (C _ys ), which has such a value that, together with the inductance of the deflection coils (L _y ) mentioned, it forms a series resonant circuit (L ₃ ,, C _ys ) practically tuned to the line frequency, and which is bridged by shunt means (L _by ) for the sawtooth-shaped grid currents. 2. A circuit according to claim 1, characterized in that the shunt means (L _by ) consist of a shunt coil, such that it _{forms a combination with the deflection coils (L y} ) and the tuning capacitor (C _ys ) , which forms both parallel resonance and series resonance and the shunt coil (L _by ) and the tuning capacitor (C _ys ) together form one element and the deflection coils form the other element of the series resonant circuit which is tuned to the line frequency. 3. A circuit according to claim 1 or 2, characterized in that the push-pull output stage (T ₁ , T ₀ ) consists of the combination of an npn transistor (T ₁ ) and a pnp transistor (T ₂ ). 4. Circuit according to one of the preceding claims, characterized in that the mixing takes place additively with the aid of a pair of diodes (D ₂ , D ₃ ) added to the output amplifier devices _{(T 1} , T ₂ ). 5. A circuit according to claim 4, characterized by a transistor control stage (T ₀ ) as emitter follower, with the base electrode of the control transistor (T ₀ ) connected ÄC charging network (R ₇ , C ₉ ) and means (t _L ) for supplying a single line frequency Input signal via one (D ₂ ) of the mentioned diodes and the capacitor (C ₉ ) of the mentioned network (R ₇ , C ₉ ) to the base electrode of the control transistor (T ₀ ) and via the other of the mentioned diodes (D ₃ ) to the emitter electrode that end transistor (T ₂ ), which is located on the grounded side of the push-pull stage (T ₁ , T ₂ ) . 6. A circuit according to claim 4, characterized by an ÄC charging network (R ₇ , C ₉ ) and means (tL _b , tL _a ) for supplying two line frequency input signals with opposite phase via the capacitor (C ₉ ) of said network (R ₇ , C ₉ ) to the base electrodes of the output transistors, each input signal being fed to the aforementioned network (R ₇ , C ₉ ) via one of the aforementioned diodes (D ₂ , D ₃ ) and these diodes (D ₂ , D ₃ ) with regard to their Forward direction are switched in opposite directions. 7. Circuit according to one of claims 4 to 6, characterized in that the two push-pull output amplifiers (T ₁ , T ₂ ) are connected to one another via the parallel connection of a capacitor (C ₂ ) and a diode (D _{1), the capacitor (C 2} ) has such a value that it practically tunes the deflection coils (L _y ) to a frequency equal to the raster throwback period during the raster throwback. Considered publications:
German Auslegeschriften No. 1023078,1051996. 1 sheet of drawings 809 587/391 7.68 © Bundesdruckerei Berlin