DE1462901C3 - Circuit arrangement for correcting the switching phase of a line switch for PAL color television receivers - Google Patents

Description

Correction signal to be used if necessary is lost. ■. .

A significant improvement is achieved if the circuit arrangement mentioned at the beginning According to the invention, the correction signal 5 is taken from that color signal component, in which the amplitude of the correction signal if the switching status of the line switch is incorrect is practically maximum. .

In the correct switching state, the amplitude of the correction signal is not at all effective needs to be minimal; on the other hand, however, this takes away for a correction of the wrong switching state required signal to a maximum value and can therefore be a blocking in the correct state to overcome the threshold without difficulty. .

The invention is explained in more detail below with reference to the drawing, for example.

F i g. 1 shows a block diagram of an arrangement for obtaining the correction signal according to the invention in a color television receiver;

F i g. 2 is a phasor diagram showing the mutual phase relationships of the various signals occurring in a circuit according to FIG. 1; "..

F i g. 3 shows a simple circuit diagram of a part the arrangement according to FIG. 1, in which the demodulated color sync signal according to a further development of the invention is processed.

For the sake of clarity, non-essential details are not shown in the figures.

A (G-Y) output 1 of a synchronous demodulation device 3. in the color part of a television receiver is via a gate circuit 5, an integration and threshold value circuit 7 and a correction signal generator 9 with an input 11 of a Line sequence switching device 13 connected.

The line sequence switching device 13 is via a connection 15 to a local reference signal generator 17 connected. Through the connection 15, a reference signal of the row sequencer 13 are supplied. The phase of the supplied reference signal can be adjusted in the line sequence switching device 13 can be rotated from line to line over 180 ° each time. The reference signal thus obtained with a phase changing by 180 ° from line to line can be achieved by a connection 19 of the line sequence switching device 13 are removed and fed to the synchronous demodulation device 3.

By a connection 21 between the reference signal generator 17 and the synchronous demodulation device 3 can be a reference signal with a phase of the synchronous demodulation device which is the same from line to line 3 are fed.

The line sequence switching device 13 consists of an electronically controlled switch, e.g. B. a bistable multivibrator 23 which receives line-frequency actuation pulses through a connection 25, and a phase switch 27, in which the phase rotation of the supplied through the connection 15 Reference signal takes place.

The synchronous demodulation device 3 also has an input 29 for the supply of a chrominance signal F to be demodulated and two outputs 31 and 33 for the extraction of the demodulated color difference signals (RY) and (BY). The input 29 is connected to a color signal separator 35, in which the chrominance signal F supplied through the input 29 is delayed by one line period and combined with the non-delayed chrominance signal in such a way that the connections 36 and 37 connected to the color signal separator 35 a chrominance signal component with a constant phase is available.

With the now usual PAL color television signal these are the red and blue color difference signal components that occur during the line trace. ■■ · .- ■ .- ..

With such a PAL signal, a color sync signal (B) occurs during the return line, which can also be broken down into two components, of which the first (U) has a constant phase that is opposite to the phase of the blue color difference component, and the second (F) is always in phase with a red color difference signal component and thus changes its phase by 180 ° from line to line.

Component (V) with the changing phase of the color sync signal is also available via connection 36 and component (U) with a constant phase is available via connection 37.

The components (U) and (V) of the color burst signal have the same amplitudes in the usual PAL color television signal.

The synchronous demodulator 39 receives a reference signal through the connection 19, the phase of which changes by 180 ° from line to line. In the correct switching state of the line sequence switching device 13, the signals fed to the synchronous demodulator 39 are always practically in phase, but in an incorrect switching state they are alternately out of phase. At an output of the synchronous demodulator 39 then occurs an in-phase or anti-phase demodulated color difference signal component (RY) and a component (V) of the color synchronous signal (B) also demodulated in phase or anti-phase. These demodulated signals are fed to a matrix circuit 45 via a connection 43.

The synchronous demodulator 41 receives the blue color difference signal component and the component (U) with a constant phase of the color synchronous signal (B) via the connection 37. These signals are demodulated synchronously by means of the reference signal supplied through connection 21, which is practically in phase with a blue color difference signal component. A blue color difference signal (BY) always demodulated in the same phase and the component (C /) of the color synchronization signal (B) also always demodulated in the same phase then appear at an output of the synchronous demodulator 41, regardless of the switching state of the line follower circuit 13. These demodulated signals are fed to the matrix circuit 45 via a connection 47.

^: In the matrix circuit 45, a green color difference signal (GY) is put together from the signals fed through the connections 43 and 47 and appears at the output 1 during the line trace.

While the line is being rewinded, one appears at output 1 that is demodulated in the same way from two Identification signal composed of components of the color sync signal, which is transmitted via a connection

application 49 of the gate circuit 5 is supplied. The gate circuit, which has a connection 51 blanking pulses receives only the composite burst signal transmitted over the link 53 of the integration and threshold value circuit 7 is supplied.

The composite demodulated color burst signal available in connection 53 is equal to one, after one with the demodulation

for the sake of clarity, this is not illustrated in the figure. Only the position of the demodulation axes is significant here with respect to the modulation axes. This mutual position determines the demodulation method a signal fed to the demodulators. This mutual position depends on the switching state the line sequence switching device 13 dependent. If the switching status is correct, the demodulation axes fall always together with the modulation axes.

axis of the green color difference signal collapses If the switching status is incorrect, each demodulation

The axis of the modulation is the mirror image of the corresponding axis of the modulation in relation to the (BY) axis. _{The latter state is 2} ge for the demodulation axis of the green color difference signal (GY)

Lenden phase synchronously demodulated color sync signal. According to the invention, this results in the incorrect switching state of the line sequential switching device
13 shows a practically maximum amplitude of the demodulated color sync signal, which is indicated by dashed lines in FIG.
F i g. 2 will be explained in more detail. The in the color synchronous In F i g. 2, the full pointer gives a color sync signal, the information contained in this incorrect signal B _n with components V _n or F _{n + 1} in the term switching state is practically completely used, negative (BY) direction, which occurs during the lines η im a Correction signal to correct this un- and (n + l) occur and are equal, and to achieve a correct switching state.

The good effect of the circuit arrangement is very little of any noise or of Interference dependent and therefore still very reliable even with weak signals.

Component V _n during the line η and with a

Component V _n phase-shifted by 180 ° during line η + 1.

This color sync signal is thus a mirror image of the (B-Y) axis from line to line.

In a further embodiment of the invention, for the sake of clarity, this is shown in FIG. 2 not integration and. Threshold value - further shown.

circuit 7, which is based on FIG. 3 explains in more detail only the mutual phase relationship of the

is, from the train via the connection 53 color sync signal and the demodulation axis is led demodulated color sync signal only with synchronous demodulation of the color sync signal which are important for identifying the switching status of the 3 °.

Line sequence circuit 13 meaningful information In the case of synchronous demodulation of a color synchronous

separated from signals that are not significant for this, signals according to the (G-Y) demodulation axis can be a and in the form of a correction signal via a connec- tor or an incorrect demodulation state tion 55 is supplied to the correction signal generator 9. according to the correct or incorrect switching

If the correction signal state of the line sequence circuit 13 according to FIG. 1 prayer a color identification signal corresponding to the step.

Incorrect switching status of the line sequence switching in the correct switching status occurs synchronous

direction 14 receives, he delivers a z. B. in known demodulation of the burst signal B _n along the way generated change signal that the input (GY), - axis, whereby a small negative ampli-11 of the line sequence switching device 13 is supplied 40 tude (ß _nl ) of the demodulated burst signal. As a result, z. B. the bistable multivibrator 23 switched once in addition, or as a result
of the line pulses fed in via connection 45, the switchover is prevented once.

Then the correct switching state of the line sequence 45 color sync signal occurs. The amplitude B _{n 2} is restored circuit, whereby the color identification according to the invention is practically the same as the maximum achievement signal in the connection 55 and the
correct switching state is maintained until z. Legs
any fault changes the switching state back to a
incorrect state changes, whereupon the described 5 °
Correction process occurs again.

On the basis of FIG. 2 it is explained that actually in the incorrect switching state due to the synchronous demodulation of a color sync signal in _

to apply a demodulation phase of the synchronous demodulation 55 chronsignal, the incorrect lators for the green color difference signal demodulates a prak- switching state in a phase that is practical maximum amplitude of the demodulated color sync signal arises.

In the phasor diagram according to FIG. 2 are through
full lines the modulation axes (BY) and (RY) 6 ° order according to the invention can also be used for processing and the resulting modulation axis (GY) for a PAL signal in which the blue, red and green modulation axes on the color carrier wave are chosen differently,
modulated color difference signal F indicated. A circuit arrangement according to the invention

The modulation axis (RY) changes its phase can still be used successfully in a receiver of the more than 180 ° from line to line, and all of the so-called »Simple PAL« type can be used,

occurs.

In the correct switching state, synchronous chromium demodulation takes place along the (GY) ₂ axis, resulting in a large positive amplitude B _{n 2 of} the demodulated

ble amplitude B _n that would occur due to synchronous demodulation in the phase of the color sync signal.

In the embodiment described above, the burst demodulated in the (G-Y) phase is taken from a (G-Y) output of a matrix circuit. However, it is also possible to use a separate synchronous demodulator for the color syn-

table coincides with the phase of the color sync signal or is practically 180 ° different from this. It will also be evident that the circuit connection

Carrier wave modulated signals are therefore mirror images in the diagram from line to line with respect to the (ß-Y) axis, which has a constant phase. German

which does not include a signal separator 35 with a delay device.

Instead, the phase of the dem (/? - Y) demo

is switched from line to line, the phase of the to be demodulated, the signal supplied to the demodulator by means of the line sequence switching device from line to Row can be rotated over 180 °.

F i g. 3 shows an advantageous embodiment of FIG Gate circuit 5 and the integration and threshold value circuit 7 according to FIG. 1.

At terminal 61, the green Color difference signal (G-F) supplied, its peak value about + 6 V to earth and its internal resistance 62 is about 1500 ohms. This signal is by means of the capacitor 63 of 1000 pF in the

impulse is not opened; the small control pulses that occur with the correct phase position then result no output voltage changes. Between the terminal 61 and the base of the transistor 70 is a

5 Diode 78 (OA 91) switched on, which lets the control pulses through, but prevents the transistor due to the strongly negative potential of terminal 61 in relation to the emitter in the blocking intervals can be damaged.

ίο If, however, the phase position between the PAL switch and the signal is incorrect, demodulated color sync pulses with a larger, positive amplitude appear in the green color difference signal (GY) at terminal 61. Through this the Tran

art that smoking disorders can also make themselves less noticeable. The frequency range allowed to pass is sufficient to obtain correction pulses of sufficient amplitude.

The demodulated color sync signals contained in the supplied signal are used to form the Correction signal taken by means of a key circuit. For this purpose, one is on the other hand grounded

Bandwidth limited; So the partial ^{speed 1} S sistor70 are strongly opened in the sampling interval, so that at higher frequencies, large negatively directed impulses appear largely filtered off its collector. These pulses can be used to change the phase of the PAL switch.

However, it is necessary to prevent 20 individual, e.g. B. through on the signal transmission path interspersed interference caused impulses to simulate a wrong phase position and the phase position of the PAL switch. A certain integration effect should therefore be achieved in such a way that

Winding 64 of the flyback transformer Rückschlag- ² 5 that a correction signal is only passed on to the PAL-Umimpulse 65 with positive polarity and about 75 V switch when several, z. B. peak voltage an integration element 'supplied, more than 5 or more than 10, correction signals also from a series resistance 67 of 4.7 kOhm and rather polarity occurred one after the other. This a shunt capacitor 68 to earth of 1000 pF is achieved according to the figure in that the collector exists. Due to the integration effect of this element 3o gate signal of the transistor 70 via a longitudinal resistance, the supplied pulses were slightly shifted 80 of 1 kOhm of the cathode of a diode 81 in such a way that it is supplied in the area of the color sync signals (OA 91), the anode of which occurs via the par and therefore are suitable for sampling these from the general circuit of a capacitor 82 of 0.1 μΡ and a guided signal. By means of which, according to a resistor 83 of 100 kOhm, at the positive positive pole of a supply voltage pole which is grounded on the other hand, there is a supply voltage pole.

source of + 30V switched diode 69 is the idle state, even with correct phase position

The amplitude of the probe pulses at this voltage value between the changeover switch and the signal is the capacitor limited and cut off. 82 practically discharged. If an incorrect phase

The signal from terminal 57 becomes the base of a location and occurs at the collector of transistor 70 npn transistor 70 (BC 107) supplied, whose emit 4o negatively directed pulses appear, these are A positive bias voltage of + 8.7 V is applied to the capacitor 82 via the diode 81 in that it on the one hand via an adjustable such that this via the internal resistance of the Im resistance 71 of 1 kOhm and a fixed pulse is charged. This internal resistance is stood 72 of 1.8 kOhm with the mentioned positive in any case when the transistor 70 is very wide open Supply voltage pole is connected and on the other hand 45 is, essentially through the resistor 80 beüber a resistor 73 of 1 kOhm is connected to earth. true, so that a charging time constant of The resistor 73 is 100 μβεΰ or more through a capacitor 74. As the duration of a Korvov 40 μΡ decoupled for alternating voltages and correction pulse is only about 2 μβεσ, are for the further through a resistor 75 of 18 kOhm with charging of the capacitor 78 many pulses required Base of transistor 70 connected. The collective. The supplied pulses are so through gate of the transistor 70, the voltage of the capacitor 82 is limited via a resistor 76; on arrival Its amplitude is therefore 2.2 kOhm at the same positive supply voltage of a charging interval terminal connected. negligibly low, and it increases with the span

Due to the positive emitter bias, the voltage on capacitor 82 is. These pulses are generated by Transistor 70 normally blocked. From the condenser 55 to the terminal 84 fed to the PAL switch, Sator 68 are over a resistor 77 of If they exceeded a certain limit amplitude -10 kOhm of the terminal 61 pulse pulses supplied. The phase position of this switch will have data by correcting the potential of the base to + 9V, so that the correction is so that the transistor becomes weakly conductive. no impulses; the capacitor 82 discharges In the case of the correct phase position of the PAL line reversal, then again.

switch in relation to the switchover in the signal to achieve demodulated color synchromeshes and the correction circuit in the scanning interval, Chronic signals smaller negative (for smaller positive ones it can be useful to use the separated correction voltage values) directional polarity that is transmitted to the KoI signal from terminal 84 of the switching stage lektor of the transistor 70 small positive direction im- 65 to feed another diode 85, which only impulses pulse appear. If necessary, the one that lets through negative polarity here The bias of the transistor 70 is also so high that a change and correction of the switching position is selected be that the transistor 70 is to be added by the tactile.

Af \ O COT / ICO

Claims (8)

1 . 2. Patent claims resistor (80) and the diode (81) is taken. 1. Circuit arrangement in a color television 8. Circuit arrangement after one of the preceding receivers for correcting the switching phase of a previous claim, characterized in that a line switch in which a first color signal - 5 that the separated correction signal of the Um component is fed with constant phase and a switching stage via a diode, the second color signal component with from line to only pulses of that polarity through Line of changing phase orthogonally to one change and correction of the switching position Color carriers are modulated and a color is to be brought about. Synchronous signal is transmitted, the phase of which is io differs from the modulated first color signal component by a value whose The invention relates to a circuit. Sign changes from line to line, with arrangement in a color television receiver for cords Demodulator part by means of a key circuit rectification of the switching phase of a line switch, at from a demodulated color signal a correction or a first color signal component with a constant signal is taken, by means of which at the phase and a second color signal component Incorrect phase position of the line switch corresponds to the orthogonal phase changing from line to line is yawed, characterized in that they are modulated onto a color carrier and where a that the correction signal of that chrominance signal is transmitted whose phase Component is removed, in which at incorrect 20 compared to the modulated first color signal Komtigem Switching status of the line switch the component deviates by a value, the sign of which Amplitude of the correction signal practically maxi- changes from line to line, with the demodule ^. times is. latorteil by means of a push button circuit from a demo y 2. A circuit arrangement according to claim 1 for the modulated color signal, a correction signal taken from j reception of a PAL color television signal, in which 25, by means of which the blue color difference signal (BY) is constantly corrected in the wrong phase position of the j the blue color difference signal (BY) line switch. Such switch ^: remains and the axis of the red color difference for signals that are alternately and incessantly stir alternately via different path signals (RY) , z. B. is switched over with PAL color television, the axis of the color synchronous wear method is switched once over a direct channel signal between + 45 ° and -45 ° periodically 30 and on the other hand via a delay line, characterized in that are known. A signal (GY) is taken to identify the position of the image information signal part switched to the green color difference signal. The color sync signal is also transmitted, the phase of which 3. Circuit arrangement according to claim 2, there also changes. In the case of demodulation, characterized in that the demodulated 35 is a characteristic of the burst signal Remove color sync signals to form the correction size, which provides information about the darsignals taken by means of a pushbutton circuit over whether the switch present in the receiver will. has the correct phase position and thus the output 4. Circuit arrangement according to one of the signals is correct or whether the switch is wrong Claims 1 to 3, characterized in that 40 works. the sampled impulses via a threshold You can also separate the color sync signal value arrangement are performed in such a way that the NEN and in a phase-sensitive rectifier with the correct phase position occurring small Im- win the desired square wave signal, the one pulse does not control output voltage changes. That requires a considerable amount give. 45 Effort for the separation and reinforcement of the 5. Circuit arrangement according to one of the preceding color sync signals. going claims, characterized in that the correction signal can also be used that the extracted signal can be extracted from a cradle color component on which the the output of the correction pulse amplitude from periodically performed switching has an effect; at Reaching frequency range is limited. 50 a PAL process with a compared to the 6. Circuit arrangement according to one of the pre-axis of the blue color difference signal (BY) on previous claims, characterized in that + 45 ° or -45 ° switched color synchro that the correction signal received is a time signal, this is the red color difference signal (RY). Constant element (81, 82, 83) is fed, which then receives an output signal that consists of a line type that only a correction signal to the synchronized pulses of the same size, whose chronizing switching stage is passed on, polarity of the correct or wrong phase position if several, z. B. more than five correction depends. Any correction is therefore solely dependent on signals of the same polarity one behind the other depending on the polarity of the pulses. are kicking. Since the color sync signal only lasts a short time 7. Circuit arrangement according to claim 6, that 60 span occurs for a long time and its amplitude is not too great characterized in that the correction signal is large, is the information content of the correction Form of negatively directed impulses of the cathode signal low. In addition, the right one a diode (81) is fed, the anode and the wrong phase position only through the Poiiber the parallel connection of a capacitor differs larity, so this is the right one (82) and a resistor (83) at the positive 65 phase position indicating signal not used at all Supply voltage pole lies, and that the signal for and further for which the polarity is fixed Correction of the phase position of a downstream arrangement,;:. B. a semiconductor component, ended switch to the connection point of the that has a threshold value, another part of the