DE1279074B - Circuit arrangement for line deflection of the electron beam in a television receiver - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN 4WWWt PATENT OFFICE

EDITORIAL

Int. Cl .:

H04n

German class: 21 al - 35/20

Number:
File number:
Registration date:
Display day:

P 12 79 074.8-31 (N 28741)

June 25, 1966

3rd October 1968

The invention relates to a circuit arrangement for line deflection of the electron beam in a television receiver, in particular a color television receiver, which has a first stage that is with a periodically conductive switch and a first transformer is provided with the a capacitor a sawtooth-shaped current can be generated, and which contains a second stage, which is provided with a periodically conductive switch and a second transformer in which Secondary winding during the flyback time of the aforementioned sawtooth-shaped current has a high pulsed voltage is generated, which secondary winding via a rectifier of the output anode supplies a high DC voltage to a display tube.

In projection television receivers is known to generate the in relation to the deflection power relatively large high-voltage power applied a separate transformer. This is in In contrast to the practice with black and white television receivers, in which the deflection power and the relatively low high voltage power can be generated with the aid of a single transformer.

For obtaining sharp lines on the display tube screen in, among other things, a color television receiver a high focus voltage is still required. But then it is necessary that there must be a clear relationship between the focus voltage and the high voltage.

The invention has the purpose, in particular in color television receivers with separate Ablerikstrom- and high voltage generation, a unique relationship between the focus voltage and the To achieve high voltage, and the circuit arrangement according to the invention is characterized in that a first tap on the first transformer via a rectifier with a focusing electrode the display tube is connected and that a second tap via a control circuit with the second transformer is connected, which control loop the size of the pulse-shaped high voltage of the second transformer in a nearly fixed ratio to the size of the focusing electrode supplied voltage regulates.

It should be noted that the design of a control loop which can be used in the invention is known per se and that the problem of a coupling of sharpness and brightness has already been pointed out became.

The invention is based on the knowledge that although the high voltage, but almost not the

Circuit arrangement for the line deflection of the
Electron beam in a television receiver

Applicant:

N. V. Philips' Gloeilampenf abrieken,

Eindhoven (Netherlands)

Representative:

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

2000 Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Antonius Boekhorst, Eindhoven (Netherlands)

Claimed priority:

Netherlands 22 February 1966 (02 234)

Focusing voltage is loaded by changes in the intensity of the electron beam. For a color remote

However, it is absolutely necessary that the high voltage remains constant when the intensity of the electron beam changes, otherwise color errors will result. A control loop for the circuit arrangement connected to the high-voltage transformer is therefore indispensable. Since the focusing voltage, as mentioned, is almost independent of the intensity changes of the electron beam, overcompensation of the focusing voltage would occur if the focusing voltage were taken from a tap on the second transformer of the mentioned control circuit. Therefore, according to the invention, the focusing voltage is taken from a tap on the first transformer (possibly only regulated for mains voltage changes). To further specify the unique relationship between the high voltage and the focusing voltage also a coupling between the second tap on the first transformer and the control circuit ¹ of the second transformer is then prepared. This is also necessary because it must be possible to set both the image width (change in the amplitude of the deflection current) and the high voltage.

The principle of the invention is explained in more detail below with reference to the drawing, in which, for example a circuit arrangement for use in a color television receiver is shown.

809 619/372

3 4

The circuit arrangement 19 shown in the figure contains a rectified pulse-shaped voltage at the pentode 1, the cathode of which is connected to earth. Coupling capacitor 2 an almost sawtooth The value of the focus voltage V _f can be adjusted by means of the shaped pulses interrupted by blocking 5 control potentiometer 21, voltage-3 is supplied. The control voltage 3 The secondary winding part 8 of the first transformer

is the line oscillator in the color television receiver mators 6 supplies the pulse-shaped induced in it taken. Voltage to a series connection of a condenser

The anode of the pentode 1 is with one end of a generator 23 and a winding part 4 grounded at the other end of the two winding parts 4 io leakage resistor 24. The voltage generated across the leakage resistor and 5 existing primary side of a transfer 24 is via a parallel mator 6 connected, the secondary winding of the circuit of a coil 25 and a resistor 26 the winding parts 7 and 8 consists. An existing tap 9 on the winding part 4, which widens the pulse duration, is fed to the grid of a triode 27 with the cathode of a plant. The series saving diode 10 is connected, the anode of which is connected to the 15 anode of the triode 27, the cathode of which is grounded, positive terminal + V _{b of} a DC voltage source (not shown) via a resistor 28 to the positive terminal DC voltage source F ₆ , the + F _{6 of} which is connected to the DC voltage source V. _b and is grounded via a negative terminal. The other end 11 of the series connection of a coupling capacitor 29 and winding part 4 is connected via a savings capacitor 12 of a resistor 30 to the control grid of a (booster) with the series connection of the winding pentode 31. The control voltage for the parts 5 and 7 connected, whereby the connection point grid of the pentode 31 has as a result more or the winding parts 5 and 7 directly and the other less the same shape as the control voltage 3. End of the winding part 7 via a resistor 13 As from the The description below is due to the earth. The resistor 13 is in the form of a potentiometer which is given by the feedback circuit via the resistor, the tap of which is connected to a non-25 32 the connection point of the capacitor 29 and linear resistor, a varistor 14 (VDR), ver of the resistor 30 a bias voltage for determination. The other terminal of the varistor 14 is the measurement of the amplitude of the anode current of the pentode 31 via a resistor 15 to the control grid.

the pentode 1 as well as via a separating capacitor The anode of the pentode 31 is connected via a series

16 connected to the connection point of the savings capacitor 30 circuit of the primary winding 33 of a second 12 and the winding part 5. To the transformer 34 and a savings capacitor 35 with series connection of the winding parts 5 and 7, one of the positive terminals + V _{b of} a deflection coil 17 in the drawing is connected in parallel, in which a current (not shown) direct voltage source F ₆ 'is used to deflect the electron beam in the line. bonded, the negative terminal of which is grounded. A tube must be generated with the direction on the screen of a color television _{display 35 its anode to the positive terminal + F 6 '.} closed series saving diode 36 is with its cathode

With the previously described known circuit with a tap on the primary winding 33 verbuntungsanordmmg flows under the control of the den. The secondary winding 37 of the transformer 34 Control voltage 3 is a sawtooth-shaped current flowing through it with one end both via a parallel circuit Winding parts 4, 5 and 7 and those with these 40 tion of a variable resistor 38 and one bonded deflection coil 17. During the flyback time capacitor 39 galvanically with the connection of the The sawtooth-shaped current passes through this winding point of the primary winding 33 and the savings capacitor part and the inductively coupled winder 35 as well as via a resistor 40 to earth treatment part 8 on a pulse-shaped voltage. The connected. The other end of the secondary winding Duration of the pulsed voltage can be given by the 45 37 is connected to the anode of a diode 41, Choice of the value of the effect of the stray cathode over the inner conductor of a coaxial capacitance the winding parts of the transformer 6 cable 42 with the output anode, not shown promoting capacitor 18 are determined. a color television display tube is connected.

To obtain a certain constant of the elements mentioned generate in the primary

Mains voltage changes almost independent 50 winding 33 a more or less sawtooth amplitude of the sawtooth current through the deflecting-shaped current, with the return by blocking coil 17 is the pulse-shaped voltage above which the conductive pentode 31 is brought about. In Capacitor 16 is fed to the varistor 14 and this flyback time is over the windings of the rectified with the latter. With the help of the varistor 14 transformer 34 a pulse-shaped voltage a negative bias voltage is thus generated across the 55. The peak of this voltage is below Resistance 15 to the control grid of the pentode 1 draws other things from the size of the amplitude of the leads, the potentiometer 13 for setting pentode 31 depending on the interrupted current. the a certain value of this bias voltage is used, high pulse-shaped voltage on the secondary der the desired amplitude of the sawtooth current winding 37 has the consequence that the diode 41 indicates. So the output anode in the playback

According to a first measure according to the invention tube certain capacitance to ground a high one is obtained from the tap point 9 at the first DC transfer voltage V _EHT , mator 6 a first tap to the anode of a to achieve sufficiently sharp lines on the

Diode 19 led. The cathode of the diode 19 is connected via the screen of the color television display tube, which has a capacitor 20 with the tap on a 65 line under the influence of the sawtooth current in the deflection coil 17 connected in parallel with the deflection coil 17 and the high voltage V _EHT from the meter 21. The electron beam recorded during the flyback time should occur between the sawtooth current and the diode of the focusing voltage V _f and the high voltage

V _EHT exist a clear relationship. According to a second measure according to the invention, this relationship is obtained in that a control loop is provided which in itself ensures that the high voltage V _{EHT is} kept constant in the event of changes in load (change in the intensity of the electron beam) and changes in the mains voltage. This control loop contains a triode 43, the grid of which is connected to the tap on the resistor 40 in the form of a potentiometer and to the outer conductor of the coaxial cable 42. A series connection of a second secondary winding 44 of the transformer 34 and a resistor 45 is attached between the anode and the cathode of this triode. The connection point 46 of the winding 44 and the resistor 45 is connected to the connection point of the capacitor 29 and the resistor 30 via the aforementioned resistor 32.

This connection creates a coupling between the control loop with the triode 43 and the control grid of the pentode 31. A capacitor 47 is accommodated between the grid and the cathode of the triode 43, while the cathode is connected both via a capacitor 48 to the positive terminal + V _b and via a series circuit of resistors 49 and 50 to earth.

The mentioned second measure according to the invention is further that by means of a second Tapping on the first transformer 6 of the connection point 11 via the resistor 51 with the Cathode of the triode 43 is connected.

In order to achieve that the voltage across the savings capacitor 12 can be changed without changing the voltage at the cathode of the triode 43 also changes, there is a high resistance across the savings capacitor 12 Voltage divider 42 connected, the tapping of which is connected via a variable resistor 53 the connection point of the resistors 49 and 50 is connected. The mode of action is in the explained in more detail below.

To explain the mode of operation of the control loop under various circumstances, let mentioned the following:

The secondary winding 44 supplies the anode of the triode 43 with a positive pulse-shaped voltage which is proportional to the rectified pulse-shaped voltage V _{EHT generated in the winding 37.} A part of the voltage on the savings capacitor 35 is fed to the grid of the triode 43 by means of the potentiometer 40 with positive polarity. A voltage at the savings capacitor 12 with positive polarity is fed to the cathode of the triode 43 with the aid of the voltage divider consisting of the resistors 51 and 49, 50. The setting of the triode 43 is thus such that the control loop is in equilibrium and that the aforementioned clear relationship exists between the values of the focusing voltage V _f and the high voltage _{V EHT.}

If, for whatever reason, the value of the high voltage V _EHT decreases, the voltage on the saving capacitor 35 also decreasing, both the voltage on the anode and that on the grid of the triode 43 decrease, so that the current in the element 43, 44 and 45 existing circle becomes lower. The voltage drop across resistor 45 is thus lower, as a result of which the voltage at point 46 increases. The bias on the control grid of the pentode 31 is then less negative. It has already been mentioned that the triode 27 supplies the control grid of the pentode 31 with a voltage which has more or less the same shape as the voltage 3. The pentode 1 or 31 is blocked by the pulse-shaped part of the voltage 3 going in the negative direction and, depending on the bias voltage applied to the control grid, becomes conductive at a certain point of the pulse-shaped part going in the positive direction. Depending on the size of the bias voltage, a certain amplitude of the sawtooth current in the winding 33 occurs at the time of the blocking time of the pentode 31. If, in this case, the bias voltage at the control grid of the pentode 31 becomes less negative, the amplitude of the sawtooth current in the primary winding 33 increases so that a higher pulse-shaped voltage is generated in the transformer 34 when the pentode 31 is blocked. The control loop thus counteracts the decrease in the high voltage V _EHT .

Changes in the supply voltage V _b , which directly influence the voltage on the savings capacitor 35 and thus also the high voltage V _EHT , are also eliminated by the control loop. Namely, when the voltage on the saving capacitor 35 increases, the grid voltage of the triode 43 increases proportionally. As a result, a larger current flows through resistor 45 and the voltage at point 46 decreases. As already described above, as a result of the larger negative value of the bias voltage at the control grid of the pentode 31, the value of the high voltage V _{EHT is} reduced until the desired value of V _EHT is reached again. If the voltage at the savings capacitor 12 of the deflection stage changes as a result of the fact that the stabilization circuit with the varistor 14 does not work ideally when the mains voltage changes, the focusing voltage V ₁ follows this change. If the voltage at the savings capacitor 12 decreases, the voltage at the cathode of the triode 43 is lower as a result of the voltage division via the resistors 51 and 49, 50. The resulting greater current through resistor 45 and the decrease in voltage at the cathode of triode 43 together result in a low voltage at point 46. The bias on the control grid of the pentode 31 then becomes more negative. This has the consequence that the value of the high voltage V _EHT decreases. It can be seen from this discussion that as the focus voltage V _{f increases, so} does the high voltage _{V EHT} . With the aid of the circuit arrangement according to the invention, it is thus possible to obtain an almost fixed ratio between the value of the focusing voltage Vf and that of the high voltage V _EHT.

In order to obtain a possibility of regulating the bias voltage of the control grid of the pentode 31 as a function of the beam current drawn from the output anode in the color television display tube, the resistor 38 is included. The low voltage end of the secondary winding 37 of the transformer 34 is grounded in two ways for alternating current, namely via the resistor 40 and in parallel with this via the parallel connection of the resistor 38 and the capacitor 39 in series with the savings capacitor 35 and the supply source V _b ', whose not negative terminal shown is connected to earth. Since the resistor 38 is chosen to be much lower than the resistor 40, changes in the beam current are expressed in the high-voltage

Part of the secondary winding 37 and in the output anode of the display tube for the most part via the supply source F ₆ 'and the resistor 38 at the low-voltage end of the winding 37.

The voltage drop brought about by the change in beam current across the resistor 38 is influenced the voltage at the savings capacitor 35. If the beam current increases, the voltage drop takes over the resistor 38 also to so that the potentiometer 40 fed to the control grid of the triode 45 Part of the savings capacitor voltage becomes lower.

As already described above, a decrease in the grid voltage of the triode 43 results in an increase in the amplitude of the current interrupted by the pentode 31. It should therefore be evident that with an increase in the beam current and a resulting decrease in the high voltage V _EHT due to the internal resistance of the high voltage generator, this decrease can be eliminated by the control loop.

To obtain a very rapid stabilization control of the high voltage V _EHT , a connection is established between the outer conductor of the coaxial cable 42 and the grid of the triode 43. If the value of V _EhT decreases, the voltage at the control grid of the triode 43 also decreases as a result of the capacitive voltage divider built up from the capacitance between the inner and outer conductors of the coaxial cable 42 and the capacitor 47. It has already been demonstrated that the control loop will increase the voltage V _EHT so that the change in V _EHT can be eliminated. To achieve a change in the voltage across the saving capacitor 12 (since in this way the length of the lines on the screen of the display tube can be changed) with a nearly constant voltage at the cathode of the triode 43, a voltage divider 52 is arranged across the saving capacitor 12. To explain the mode of operation, consider the circuit made up of resistors 49 to 53. By reducing the value of the resistor 53, the current flowing from the savings capacitor 12 via a resistor of the voltage divider 52 and the resistors 53 and 50 to earth increases. The voltage on the savings capacitor 12 and thus also the voltage supplied to the cathode of the triode 43 via the resistor 51 decrease as a result. However, the increase in the current in resistor 50 leads to an increase in the voltage at the junction of resistors 49 and 50. A favorable dimensioning of the resistors has the consequence that the decreasing voltage supplied to the cathode of the triode 43 via the resistor 51 is compensated for by the increasing voltage supplied via the resistor 49. This also applies to the case when the value of the resistor 53 is increased. With the aid of the resistor 53, the voltage across the savings capacitor 12 can thus be changed without the high voltage V _{EHT being} changed.

An amplitude of the sawtooth current in the transformer 6 for the line deflection that is as constant as possible is obtained by smoothing the supply voltage F ₆ and by the effect of the varistor 14. The focusing voltage V _f taken from the transformer 6 is thus well stabilized even in the event of changes in the line voltage. The high voltage V _EHT has a tendency to vary greatly due to large changes in the beam current in the color television display tube and in the internal resistance of the high voltage generator. The control loop now counteracts a change in V _EHT . To prevent the line deflection stage from being influenced by the high-voltage stage, two separate DC voltage sources F ₆ and V _{b are} used. Due to the presence of the strong control loop according to the invention, the voltage F ₆ 'need not be well smoothed. The control loop has a sufficiently high speed to eliminate the effect of mains voltage changes in the circuit arrangement.

If a line voltage change occurs, which _{cannot be completely eliminated by the smoothing circuit (not shown) near the supply source F 6} and the varistor 14, the line voltage change as a result of the change in the amplitude of the sawtooth-shaped deflection current in the coil 17 is expressed in the change in the length of the Lines on the display tube screen. However, if the high voltage V _{EHT also} changes, the influence of the line voltage change on the length of the lines on the screen is less clearly expressed. In order to ensure that changes in the value of F _{6 act} both on the line deflection stage and on the high-voltage stage, a capacitor 48 is attached to couple the supply source F _{6 of} the deflection stage with the high-voltage stage.

It should be understood that the problems described above not only apply to color television receivers, but also apply to receivers for stereoscopic reproduction of television images. Also in the latter In this case, a display tube provided with two electron beam systems is often used, see above that this tube also consumes a large amount of high-voltage power.

Claims (7)

Patent claims: 1. Circuit arrangement for line deflection of the electron beam in a television receiver, in particular a color television receiver that has a first stage that is periodically conductive switch and a first transformer is provided with which with a capacitor a sawtooth-shaped current can be generated and which contains a second stage, which is provided with a periodically conductive switch and a second transformer, in its secondary winding during the flyback time of the aforementioned sawtooth-shaped current a high pulsed voltage is generated, which secondary winding via a rectifier supplies a high DC voltage to the output anode of a display tube, thereby characterized in that a first tap on the first transformer (6) via a rectifier (19) is connected to a focusing electrode of the display tube and that one second tap is connected to the second transformer (34) via a control circuit, which Control loop the size of the pulsed high voltage of the second transformer (34) in an almost fixed proportion to the magnitude of the voltage applied to the focusing electrode regulates. 2. Circuit arrangement according to claim 1, characterized in that the second tap from the connection point (11) of the first transformer (6) and a positive voltage leading side of the capacitor (12) of the first stage to a grounded at the other end Ohms see voltage divider (49,50,51) leads, from which a tap with the cathode of an im Control loop recorded triode (43) is connected, between the anode and the The cathode of this triode is a series circuit of one mounted on the second transformer (34) Winding (44) in which a pulse-shaped voltage proportional to the high voltage is more positive Polarity is generated for this anode, and a resistor (45) is added while the control grid of the triode (43) via a grounded voltage divider (40) a part of the positive Voltage is supplied across the capacitor (35) installed in the second stage, in this control loop between the connection point of the winding (44) and the resistor (45) in the aforementioned anode-cathode circuit and the control grid of a switching pentode (31) at least one further resistor (32) is switched on in the second stage. 3. Circuit arrangement according to claim 1 or 2, characterized in that said first and second stages are each fed by a separate direct voltage source (V _b or F ₆ '). 4. Circuit arrangement according to claim 3, characterized in that the positive terminal (+ F ₆ ) of the DC voltage source (F ₆ ) of the first stage is connected to the cathode of the triode (43) in the control circuit of the second stage via an isolating capacitor (48), so that mains voltage pulses act on the two stages. 5. Circuit arrangement according to claim 2, characterized in that to achieve one fast regulation, a capacitive voltage divider is included in the control loop, which is from the Series connection of the capacitance (42) of the inner conductor with respect to that of the outer conductor of a die High voltage to the output anode leading coaxial cable and one between the grid and the cathode of the triode (43) attached capacitor (47) is built. 6. Circuit arrangement according to claim 2, characterized in that between the mentioned second tap of the first stage and the cathode of the triode (43) in the control loop of the second Stage a first resistor (51) is arranged, to which a series circuit at least two resistors (49, 53) is connected in parallel, of which the one (53) whose end with the mentioned tap is connected, is made variable, while the connection point of the last two resistors is grounded via a fourth resistor (50). 7. Circuit arrangement according to claim 2, characterized in that between one end the primary winding (33) and one end of the high voltage secondary winding (37) of the second Transformer (34) a parallel connection of a capacitor (39) and an adjustable one Resistance (38) is attached. Considered publications:
German exposition No. 1090 278,
538; German interpretation document T10346 VIII a / 21 a ¹ (published on May 9, 1956);
U.S. Patent Nos. 2,888,607, 2906918. 1 sheet of drawings 809 619/372 9.68 © Bundesdruckerei Berlin