WO1990003079A1

WO1990003079A1 - Process and circuit arrangement for eliminating variations in picture size caused by the loudness level, in particular for colour television receivers with 110° deflection picture tubes

Info

Publication number: WO1990003079A1
Application number: PCT/HU1989/000045
Authority: WO
Inventors: János SEBO^'K; Miklós HALASSY
Original assignee: Videoton Elektronikai Vállalat
Priority date: 1988-09-02
Filing date: 1989-09-01
Publication date: 1990-03-22
Also published as: DD284322A5; HU200049B; CS509989A2; EP0386217A1

Abstract

Said process is suitable in particular for television receivers with a high sound output. The circuits of the television receiver are fed with supply voltages which are stabilized through a mains supply unit and the pillow distortion of the 110° picture tube is adjusted by means of active east-west screen correction. Said process is essentially characterized in that the variations in image width caused by the variations in supply voltage of the horizontal deflection circuit (2) are compensated by regulating the image width via an east-west correction circuit (4) by means of a signal generated by the variations in supply voltage of the horizontal deflection circuit (2). The present invention also relates to a circuit arrangement for implementing said process, which includes a stabilized mains supply circuit (1), a horizontal deflection circuit (2) and a vertical deflection circuit (3), an east-west correction circuit (4) including an amplifier (41) being connected to the horizontal deflection circuit (2). The circuit arrangement is essentially characterized in that a compensating unit (5) is connected, possibly over an inserted diode (46), between the supply voltage terminal (21) of the horizontal deflection circuit (2) and the input (41a) of the amplifier (41) of the east-west correction circuit (4).

Description

METHOD AND CIRCUIT ARRANGEMENT FOR ELIMINATING

VOLUME-DEPENDENT IMAGE SIZE CHANGES, ESPECIALLY COLOR TELEVISIONS WITH 110 ° DEFLECTION PIPES

The invention relates to a method for eliminating volume-dependent changes in image size, in particular of color television sets with I10 ° deflection picture tubes, preferably for use in devices with high sound power, the circuits of the device being operated with supply voltages stabilized via switching power supplies, the pillow distortion of the 110 ° deflection The picture tube, on the other hand, is set by active east-west raster correction.

The invention further relates to a circuit arrangement for performing the method, with stabilized switching power supply, horizontal switching circuit and Ver tikal deflection circuit, wherein an east-west correction circuit is connected to the horizontal deflection circuit, which has an amplifier. In modern color television sets, the demand for sound is spreading more and more

2-channel or stereo version with a power that exceeds the previous 2-3 W by orders of magnitude, and in hi-fi quality. The sound power of such devices can even reach a value of 2 x 30 W. As a result of the reception possibilities via satellites and the increasingly widespread video devices, in which the sound is assured in stereo quality, there is a rapidly increasing demand for such TV sets even where the conventional transmitter network does not yet broadcast two-channel programs.

When increasing the sound power, the problem arises of the internal resistance of the power supply unit of the device, which is no longer negligible and which affects the significant changes in the load of the supply voltage due to "crosstalk" on the other supply voltages, i.e. in the cycle of the tone in the other supply voltages also causes changes.

As a result, there is the extremely disturbing phenomenon for the viewer that the image size changes in particular in the horizontal direction in time with the sound, since the deflection circuits react most sensitively to changes in the supply voltage.

In order to eliminate this disturbing phenomenon, the stability of the power supply unit of the device and thus those of its supply voltages are improved compared to the changing sound load. It would be desirable to keep the approximately 150 V supply voltage of the horizontal deflection circuit stable within 0.1 V, while the tone stage receives a load that changes from zero to 2-3 amperes at a supply voltage of 20 V, for example.

In addition, the load on the horizontal deflection circuit changes, depending on the brightness of the picture tube, namely a change in load of practically 25 W occurs. These numerical details make it clear which strict stability requirements the power supply unit of a device with increased sound power should meet. The solution to the problem is made more difficult by the fact that the devices would have to be manufactured in a version separate from the mains because of the connections (SCART, headphones, speakers, etc.) on the device chassis.

With the current state of the art, the switching power supply that secures the separation and is based on the integrated circuit of the TDA 4600 type from the manufacturer SIEMENS has proven and spread best in terms of efficiency, reliability and economy, according to information from SIEMENS, this switching power supply has so far found in more than 20 million telecommunications devices.

This switching power supply is described in detail in "Funk-Technik" issue 37, No. 1 on pages 21-25 with explanations of its advantages. The past time and the extremely wide distribution of this switching power supply have confirmed these advantages. The 47 pages, from the company SIEMENS in August 1987 published brochure "Switching power supplies with the component of the TDA 4600 family" gives a detailed summary of the results achieved with this switching power supply. The power supply circuit specified on page 29 is recommended as a solution with low "crosstalk values" for color television sets. From FIG. 22 on page 31 it can be seen that changes in sound load from 0.6 to 1 amp, ie changes in load of a total of 0.4 amperes in the supply voltage, already changes from 0.12

Cause volts. This example clearly shows that this circuit is not able to ensure the required stability with load changes of 2-3 amperes.

Substantially better stability parameters are characteristic of the circuit arrangement shown in the above-mentioned edition on page 32, which realizes the required voltage stability by monitoring the secondary voltage and by using further active and passive components by separate feedback control on the primary side.

Because of the problems caused by the sound, attention has been paid to such, so-called

MASTER-SLAVE circuits directed. This solution is also used in the ITT 3878 Hi-Fi-H stereo, an integrated circuit being used in both the primary circuit and the secondary circuit of the power supply, while the feedback control in the primary circuit by inserting an additional protective transformer for safety purposes he follows. The disadvantage of the above solutions is that. that the more costly service support compared to the popular Siemens circuit is very cumbersome, for back regulation from the separated secondary side to the primary side connected to the network, further components with double insulation for safety purposes, such as an optocoupler or a transformer, are claimed.

A solution described in DE-PS 2 749 847 has also set itself the goal of eliminating the crosstalk caused by the changes in volume. The essence of this solution is that in the transformer of the power supply, the coupling of the winding feeding the sound output stage with the control winding is designed as a fixed coupling, while the winding feeding the horizontal deflection circuit is designed as a loose coupling.

A disadvantage of this solution is that it requires a specially constructed transformer, the uniform production of which is associated with difficulties and an optimal effect which dampens the crosstalk values can only be achieved with a predetermined load and mains voltage.

In addition, the supply voltage is no longer sufficiently stable due to the loose coupling of the supply voltage winding of the horizontal deflection circuit to the control winding, as a result of which high-voltage and image size stability problems can also occur.

Another simple solution is from the DE-OS

3 026 604 recommended, the essence of which is that in the power supply between the winding generating the supply voltage of the tone stage and the rectifier a resistor is inserted, which reduces the crosstalk values to approximately a quarter.

However, it is unfavorable that the damping factor of the crosstalk values is also insufficient in this solution and is still dependent on the load, since an optimal effect can also be seen with this solution only with a certain beam current and a certain mains voltage.

However, since in practice the beam current in color television sets is constantly changing - the extent of these changes can even reach a value of 20-25 W - it has so far not been possible to eliminate the crosstalk interference to a sufficient extent using the known methods and circuit arrangements.

The aim of the invention is to develop a method and a circuit arrangement used to carry out this method, which make it possible, using the well-proven stabilized switching power supplies in any range of the beam current and volume, to keep the changes in image size caused by volume changes within permitted limits .

The inventive concept is based on the knowledge that instead of improving the crosstalk values, the

Power supply units of the television sets - which are already at the limit of the technical possibilities - there is the possibility of making the horizontal picture width independent of the supply voltage of the horizontal deflection circuit in such a way that by changing the supply voltage of the horizontal deflection circuit via the amplifier the east -West correction circuit too an image width change with the opposite sign can be triggered and thus the change in image width can be compensated for by adjusting the size of the supply voltage supplied to the input of the amplifier.

In this way it can be achieved that the image width remains stable despite the change in the supply voltage of the horizontal deflection circuit by several volts.

In accordance with the stated aim, the method according to the invention for eliminating volume-dependent changes in picture size, in particular of color television sets with 110 ° deflection picture tubes, preferably for use in devices with high sound power, - in the course of which the circuits of the device are operated by supply voltages stabilized by means of switching power supplies, the pillow distortion 110 ° deflection picture tube, on the other hand, is set via an active east-west raster correction - on the fact that the change in picture width occurring as a result of the change in the supply voltage of the horizontal deflection circuit by means of a signal obtained from the change in supply voltage of the horizontal deflection circuit via the

East-west correction circuit is compensated by regulating the horizontal size.

The circuit arrangement according to the invention for eliminating volume-dependent changes in image size. especially of color television sets with 110 ° deflection picture tubes, preferably for use in devices with high sound power, - which is provided with a stabilized switching power supply, horizontal deflection circuit, United tical deflection circuit, with the horizontal deflection Circuit an east-west correction circuit has an amplifier - is designed such that a compensation network is inserted via a diode between the supply voltage terminal of the horizontal deflection circuit and the input of the amplifier of the east-west correction circuit.

Another feature of the invention can consist in that the compensation network is formed by a passive compensation network which has at least one Zener diode and resistor connected in series with one another.

In a preferred embodiment of the invention, an NTC resistor suitable for compensating for the change in temperature is connected in series and / or in parallel with the Zener diode.

In another embodiment of the invention, the compensation network is formed by an active compensation network provided with a primary power source, between the input and the earth of which a primary power source connected in series with a resistor, and optionally a resistor connected in parallel with the primary power source, are connected, while the common switching point of the Resistor and the primary power source is connected via an inserted impedance converter to the output of the active compensation network provided with primary power source (current generator).

In a further embodiment of the invention, the compensation network is formed by an active compensation network provided with an operational amplifier, between the input and the earth of which a resistance divider is connected, while between the center of the resistance divider and the output of the compensation network provided with an operational amplifier, an operational amplifier with preferably variable amplification is connected.

In any embodiment of the invention, the supply voltage terminal of the vertical deflection circuit, or at least that of its vertical position adjustment circuit, can be connected to the rectifier, which is connected to the line transformer winding of the horizontal deflection circuit.

The most important advantage of the method according to the invention and the circuit arrangement according to the invention is that their use can reduce the volume-dependent change in image size to a minimum dimension that is no longer perceptible to the viewer. Another advantage is that the invention does not require any major intervention in the circuits of the device, but can be implemented by installing only a few simple components. The invention is explained in more detail below by means of examples with reference to the accompanying drawing.

The drawing shows:

1 shows a general block diagram of the circuit arrangement according to the invention,

2 shows a possible embodiment of the circuit arrangement according to the invention in an east-west correction circuit constructed from discrete components, 3 shows another embodiment of the circuit arrangement according to the invention in an east-west correction circuit constructed with an integrated circuit,

Fig. 4 shows a possible embodiment of an active

Compensation network,

5 shows a further embodiment of the active compensation network. 1 shows a general block diagram of the circuit arrangement according to the invention, according to which a supply voltage terminal 21 of a horizontal deflection circuit 2 is connected to a stabilized switching power supply 1. An east-west correction circuit 4 is connected to the horizontal deflection circuit 2.

The east-west correction circuit 4 has an amplifier 41, a compensation circuit 5 being inserted between the input 41a of the amplifier 41 and the supply voltage terminal 21 of the horizontal deflection circuit 2. The supply voltage terminal 31 of a vertical deflection circuit 3 is connected to a rectifier 23 of the horizontal deflection circuit 2, the rectifier 23 being connected to a line transformer winding 22 of the horizontal deflection circuit 2. Instead of the vertical deflection circuit 3, it may be sufficient to connect a vertical image position adjustment circuit 32 to the rectifier 23.

FIG. 2 illustrates a possible embodiment of the circuit arrangement according to the invention, in which the east-west correction circuit 4 is constructed from discrete components. The east-west correction circuit 4 is provided with the amplifier 41, the input 41a of which is connected via a potentiometer 4b for image width and a potentiometer 4a to a deforming circuit 54 for vertical parabola correction.

The raster correction circuit is a known circuit, its design according to the invention essentially consists in the insertion of a passive compensation network 51. The supply voltage terminal 21 of the horizontal deflection circuit 2 is connected via a resistor 51b, Zener diodes 51a and a potentiometer 4a, ei which regulates the size of the parabola signal A potentiometer 4b for picture width and a divider 4c is connected to earth, the input 41a of the amplifier 41 being connected to the center tap of the potentiometer 4b for picture width. The passive compensation network 51 of the embodiment shown in FIG. 2 has two Zener diodes 51a and the resistor 51b connected in series.

FIG. 3 illustrates another possible embodiment of the circuit arrangement according to the invention, in which the east-west correction circuit 4 is constructed from an integrated circuit 42, for example of the type TDA 4950 or TDA 8145, the eighth connection (8th pin) of the input 41a of the amplifier 41 forms. Since the integrated circuit 42 operates in switching mode, line frequency pulses are also required, which are supplied by the line transformer winding 24.

The size of the pulses is determined by a network formed from a resistor 45, a potentiometer 44 and a limiter zener diode 43. The one with Telabgriff of the potentiometer 44 is connected to the input 41 a of the amplifier 41 via a rectifier element, which consists of a diode 46 and a capacitor 47. The compensation network 5 is formed by a passive compensation network 51, which is connected between the supply voltage terminal 21 and the common switching point of the center tap of the potentiometer 44 and the diode 46. The passive compensation network 51 contains a Zener diode 51a and a resistor 51b, which are connected in series with one another. An NTC resistor 51c is connected in parallel with the Zener diode 51a.

FIG. 4 shows a further embodiment of the invention, in which the compensation network 5 is formed by an active compensation network 52 with a primary power source, a resistor 52a and primary power source 52b connected in series with one another between the input of the active compensation network 52 and the earth, and one with the primary power source 52b connected in parallel resistor 52d.

An impedance converter 52c is connected between the common switching point of the resistor 52a and the primary current source 52b and the output of the active compensation network 52 provided with the primary current source

FIG. 5 illustrates a further embodiment of the invention, in which the compensation network 5 is formed by an active compensation network 53 with an operational amplifier. The active compensation network 53 with operational amplifier is provided with a resistance divider 53a connected between its input and the ground. At the common

The switching point of the resistor divider 53a is the Input of an operational amplifier 53b connected with a preferably variable gain. The operational amplifier 53b is provided with resistors 53c and 53d for adjusting the amplifier. The

The output of the active compensation network 53 provided with an operational amplifier is formed by the output of the operational amplifier 53b.

The circuit arrangement described above realizes the method according to the invention as follows:

The supply voltage supplied by the stabilized switching power supply 1 changes at the supply voltage terminal 21 of the horizontal deflection circuit 2 in time with the volume changes. A decreasing supply voltage causes an image size reduction.

The amplifier 41 of the east-west correction circuit 4 has a structure such that a voltage reduction at its input 41a causes the image size to be enlarged. However, if this effect is reversed in the case of a circuit with a different structure, then a corresponding phase reversal must be provided in this case. The compensation network 5 forwards the signal obtained from the decreasing supply voltage occurring at the supply voltage terminal 21 to the input 41a of the amplifier 41 of the east-west correction circuit 4, as a result of which the image width is increased. The compensation network 5 is to be dimensioned in such a way that the picture width reducing effect of the supply voltage decreasing at the supply voltage terminal 21 is compensated (compensated) by the picture width increasing effect of the amplifier 41. Measurements of the east-west correction circuit 4 shown in FIG. 2, made up of discrete components, have shown that an image width reduction, which occurs as a result of a voltage change of 1 V at the supply voltage terminal 21, at the input 41a of the amplifier 41 with a voltage reduction of 0.5 V can be compensated. It follows from this that the value of the resistances above the sliding contact of the potentiometer 4b for image width essentially corresponds to the value of the resistors below the sliding contact.

In one embodiment of the circuit arrangement according to the invention, the first Zener diode 51a connected to the potentiometer 4a was formed by a preferably 12V-Z diode, while the second Zener diode 51a connected to the resistor 51b was formed below the Zener diodes 51a was formed by a 110V Z diode, the value of resistor 51b being 330 ohms. Furthermore, a 680nF capacitor was used as a coupling capacitor 4d, a 100nF capacitor as a filter capacitor 4s, a 4.7 k0hm potentiometer as a potentiometer 4a, a 100 k0hm potentiometer as an image width potentiometer and 4c sin as a resistor

33 k0hm resistance. Satisfactory compensation was achieved with these values. With the help of this compensation, a horizontal change in image size caused by a change in the supply voltage of the horizontal deflection circuit of 150 V was reduced from 10 mm to 1 mm.

In the case of the east-west correction circuit 4 illustrated in FIG. 3 and constructed by means of integrated circuits TDA 4950 or TDA 8145, tests have shown that the reduction in image width caused by the reduction in the supply voltage can be compensated for with a fifth-sixth of the change in supply voltage at the input 41a of the amplifier 41, ie at the eighth connection (8th pin) of the integrated circuit 42. Thus, in this circuit arrangement for the value of the potentiometer 44, the value of the resistor 51b is to be selected such that the change in supply voltage weakens to a fifth-sixth at the input 41a of the amplifier 41. Care must also be taken to ensure that the limiter zener diode 43 parallel to the potentiometer 44 - the presence of which is required independently of the invention - does not prevent the compensation from being implemented. In such a circuit, perfect compensation was achieved with the following dimensioning of the components:

the potentiometer 44 had a value of 10 k0hm, the resistor 45 connected in series with it had a value of 1.5 k0hm, the Zener diode 51a was a diode of the ZY-120 type and the resistor 51b had a value of 8.2 k0hm.

Since the input 41a of the amplifier 41 is in direct current coupling via the resistor 51b and the Zener diode 51a with the supply voltage terminal 21, the temperature dependence of the Zener diode / the Zener diodes 51a must also be taken into account. The temperature coefficient of the 110V Zener diode used in the circuit according to FIG. 2 is 0.1% / ° C. If the circuit arrangement according to the invention with such a Zener diode is now installed in a device and the device is exposed to a temperature change of 15 ° C. the image size change is less than 2%, which is an acceptable value. Of course, with other types of devices, temperature compensation may be required, which can be achieved with the aid of an NTC resistor 51c connected in series with the Zener diode 51a or in parallel therewith.

Instead of the Zener diode, it is also possible to use a plurality of Zener diodes connected in series with a lower voltage or a circuit which couples the changes in the supply voltage of the supply voltage terminal 21 into the input 41a of the amplifier. Such a circuit is, for example, the solution illustrated in FIG. 5, in which a resistance divider 53a connected to the supply voltage terminal 21 attenuates the change in the supply voltage and the operational amplifier 53b connected to it amplifies the attenuated signal at the input 41a of the amplifier 41 back to the required level.

In a similar way, this object can also be achieved with the aid of such a divider according to FIG. 4, the lower link of which is a primary current source 52b consisting of an active element, to the divider an impedance converter 52c, which also contains an active element and is provided with an emitter follower, is connected. The attenuation required for compensation can be set with the help of resistors 52a and 52d.

The method according to the invention and the circuit arrangement according to the invention can preferably be used to eliminate the image size changes caused by changes in volume in all such colors visual devices are used, which are provided with an active east-west raster correction.

Claims

1. A method for eliminating volume-dependent image size changes, in particular of color television sets with 110 ° deflection picture tubes, preferably for devices with high sound power, the circuits of the device being operated by supply voltages stabilized via a switching power supply, the pillow distortion of the 110 ° deflection picture tube by means of a active east-west grid correction is set, characterized in that the image width change occurring as a result of the change in the supply voltage of the horizontal deflection circuit (2) is carried out by means of a signal obtained from the change in supply voltage of the horizontal deflection circuit (2) via an east-west correction circuit (4) Rules of the image width is compensated.

2. Circuit arrangement for eliminating volume-dependent changes in picture size, in particular of color television sets with 110 ° deflection picture tubes, preferably for devices with high sound power, which has a stabilized switching power supply, a horizontal deflection circuit and a vertical deflection circuit, an east-west correction circuit being connected to the horizontal deflection circuit , and the east-west correction circuit contains an amplifier, characterized in that between the supply voltage terminal (21) of the horizontal deflection circuit (2) and the input (41a) of the amplifier (41) of the east-west correction circuit (4) - if appropriate A compensation network (5) is inserted via an inserted diode (46).

3. Circuit arrangement according to claim 2,

characterized in that the compensation network (5) is a passive compensation network

(51) is formed, which has at least one Zener diode (51a) and resistor (51b) connected in series with one another.

4. Circuit arrangement according to claim 2 or 3, characterized in that with the Zener diode (51a) in series and / or to the Zener diode

(51a) an NTC resistor (51c) suitable for compensating for the temperature changes is connected in parallel.

5. Circuit arrangement according to claim 2,

characterized in that the compensation network (5) is formed by an active compensation network (52) provided with a primary power source, between the input and the earth of which a primary power source (52b) connected in series with a resistor (52a), and optionally a primary power source ( 52b) connected in parallel resistor (52b), the common switching point of the resistor (52a) and the primary current source (52b) via an inserted impedance converter (52c) at the output of the active compensation network provided with primary current source

(52) is connected.

6. Circuit arrangement according to claim 2,

characterized in that the compensation network is formed by an active compensation network (53) with an operational amplifier, a resistance divider (53a) being connected between the input of the active compensation network (53) with an operational amplifier and the earth, that between the center of the resistance divider (53a) and the exit of the with In contrast, an active amplifier (53a) provided with an operational amplifier is connected to an operational amplifier (53b) with a preferably variable gain.

7. Circuit arrangement according to one of claims 2 to 6, characterized in that the supply voltage terminal (31) of the vertical deflection circuit (3) or at least one vertical image position setting circuit (32) on a rectifier (23) connected to the line transformer winding (22) of the horizontal deflection circuit (2) connected.

reference numeral

1 stabilized switching power supply

2 horizontal deflection circuit

21 supply voltage terminal

22 Line transformer winding

23 rectifiers

24 line transformer winding

3 vertical deflection circuit

31 Supply voltage terminal for vertical deflection 32 Vertical image adjustment circuit

4 East-west correction circuit

41 amplifiers

41a input of the amplifier

42 Integrated circuit

43 limiter diode

44 potentiometers

45 resistance

46 diode

47 capacitor

4a potentiometer

4b potentiometer for image width

4c resistance

4d coupling capacitor

4e filter capacitor

5 compensation network

51 passive compensation network

51a Zener diode

51b resistance

51c NTC resistor

52 active compensation network with primary power source

52a resistance

52b Urstromquelle

52c impedance converter

52d resistance

52e current limiter resistor for impedance converter 53 active compensation network with operational amplifier 53a resistance divider

53c, 53d resistors for setting the amplifiers 54 Vermermerkreis for vertical parabola correction