DE2263101A1 - CATHODE TUBE FEEDING - Google Patents

Description

Cathode ray tube supply

The invention relates to a cathode ray tube feed. - ■ - ■. .

In a cathode ray tube for use in one Television receivers must generally have the ratio between the anode voltage and the focus voltage essentially at one given value to satisfactorily focus the electron beam. This tension ratio changes slightly depending on the Beam current, and especially in a color picture tube of the type with bipotential electron sources, the beam current exerts a great influence on this tension. So there will be a strict relationship between the anode voltage and the focusing voltage required.

With a known voltage supply for a cathode ray tube, in which the anode voltage is, for example, one of a plurality of diodes and capacitors

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Voltage multiplier and rectifier circuit won becomes, the focus voltage becomes from a lower level the voltage multiplier and rectifier circuit removed. Here, however, it is difficult to always find the optimal one Relationship between the anode voltage and the focus voltage upright over the entire range of variation of the jet current- ' to obtain.

It is also known that the focusing voltage can be obtained by dividing the anode voltage directly with the aid of a resistor. In this embodiment, however, there is a danger of overheating and fire because of the large amount of heat generated in the resistor, which has a high resistance value. >

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In contrast, the invention creates a supply of the

Cathode ray tube that avoids these disadvantages and the J ratio between the anode voltage and that applied to the tube applied focus voltage varies in a suitable manner so that that this voltage ratio can follow changes in the beam current. In addition, according to the invention, a safe and reliable feeding of the cathode ray tube can be achieved with no risk of resistances for deriving the focus voltage consists of direct division of the anode voltage.

A feed according to the invention of the cathode ray tube includes a high-voltage rectifier means to direct, align the rear generated by a flyback transformer <drive pulses, the rectified high voltage output! this high-voltage rectifying device is supplied to the anode of the cathode ray tube; furthermore a beam current: variation detector for detecting changes in the beam + · current and emitting an output signal which is variable as a function of: j and a j depending on the changes in the beam current

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8253101.

Device for combining the output signal of the detector with the rectified output high voltage of the rectifier device or - if the high voltage rectifier device has the form of an η-fold voltage multiplier and rectifier circuit - with the output voltage of an m-fold spam multiplier and rectifier circuit, those in η times the voltage multiplication and rectifier; circuit. is contained, where m and η are positive integers:. are and m ^e n;, whereby a resulting DC voltage er; will hold, the reduction ratio is less than or equal to the _t Eeduktionsverhältnis the rectified output Hochspannunig due to the variation of the beam current, in which case the re-; resulting DC voltage is applied to the focusing electrode of the cathode ray tube. _;

In summary, the invention is implemented in a system for feeding a 'cathode ray tube j einerjFernsehempfänger od Voltage is obtained, and means for applying the resultant voltage to the focusing electrode of the cathode ray tube. As a result, when the beam current is increased, the voltage applied to the focusing electrode: is reduced in a higher ratio than that; Reduction ratio corresponds to the high voltage applied to the anode of the cathode ray tube , so that the television picture can be displayed satisfactorily. ■

Further details, advantages and Merkaale to the invention provide verifiable from the following description, "On the drawing the invention is shown, for example and show namely

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■ ■ " ⁴ " ■

Fig. 1 is a circuit diagram of a known cathode ray tube feed system;

Fig. 2a is a circuit diagram of a η-fold savings multiplier ^ Fachungs- and rectifier circuit, which is similar to the circuit used in the system of Figure 1;

2b shows the voltage profile at the input terminal of the circuit according to Fig. 2a;

Fig. 3 is a graph showing the operating characteristics of the system of Fig. 1;

Fig. 4 is a circuit diagram of an embodiment of the invention; and

FIGS. 5 to 16 show further embodiments of the invention.

Before describing the invention, referring to Figs. 1-3, a prior art cathode ray tube power supply is considered ■ described having a triple voltage multiplier and Rectifier circuit used. According to Fig. 1 is a switching transistor 1 connected with its collector to the cathode of a damping diode 2, the anode of which is grounded. To the collector of the Switching transistor 1 is also a terminal of an S-curve characteristic compensation capacitor 3, which gives a deflection current an S-curve characteristic and which has its other terminal connected to one terminal of a horizontal deflection coil 4, the other terminal of which is grounded I is. Furthermore, one is at the collector of the switching transistor 1 Terminal of a return time determining capacitor 5 connected ; sen whose other terminal is grounded. With a power source 6 iis one terminal of a flyback transformer 7 connected, whose ' j other terminal to the input terminal M of a triple voltage multiplier and rectifier circuit 8, which consists of a plurality of capacitors C and diodes D, is connected.

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A series circuit of resistors 10 and 11 and a variable resistor 12 is connected to an output terminal F of the first stage of the voltage multiplication and rectifier circuit 8 for obtaining a focus voltage Vj ₁ ^1; the variable resistor 12 is grounded to a terminal.

When a suitable control signal is applied to the base of the switching transistor 1, a sawtooth current flows through the deflection coil 4 and a flyback pulse occurs during the flyback time. This flyback pulse is applied to the flyback transformer 7, the output voltage of which is fed to the! Input terminal M of the triple voltage multiplier and ^; Rectifier circuit 8 is applied. Their input voltage is multiplied and rectified and at an output terminal A of the circuit 8, a direct high voltage V ^ occurs, which corresponds to approximately three times the input voltage. This DC high voltage is applied to the anode of a cathode ray tube 9. _{A voltage Vj 1} occurs at terminal F.

On the other hand, the 'focus voltage V ™' is taken from the junction between resistors 10 and 11 in the series circuit of resistors 10, 11 and 12 which is connected between the output terminal F of the first 'stage of the voltage multiplier and rectifier circuit 8 and ground VJT '/ VA between the focus si ER-; voltage Vj ₁ ¹ and the anode voltage J \ is generally in' selected a range from 0.18 to 0.2, the focusing ■ V, / can be obtained by suitable adjustment of the variable resistors j.

stand 12 can be selected.

According to Fig. 2a, a plurality of sections'

each consist of two diodes D and two capacitors C, connected in cascade to a high voltage rectifier circuit to meet. The output voltage Yj-. the first stage;

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in this circuit and the output voltage Va of the last one Section are given by the equations

Vj, = V ₁ + V ₂

where η = number of diodes or capacitors; V-j and Vp = maximum positive or maximum negative value of a voltage according to FIG. 2b. This voltage form corresponds to that of the transformer 7 output voltage output according to FIG. 1 and thus the input voltage at terminal M.

In the case of the voltage multiplier and rectifier circuit 8 according to FIG. 1, η = 6 results, since three stages are combined to form a cascade. In the ideal case, therefore, the voltage ratio VlVVa between the output voltage Vp of the first stage and the output voltage Va of the last stage or the voltage ratio Vp ¹ / Vα between the focus voltage Vj / and the anode voltage Va is determined by the number η of diodes or capacitors. Actually, however, the voltage ratio Vt, / Va thus changes V _p ^f / Va depending on the beam current due to the internal resistance of the diodes, due to changes in the shape of the input voltage, etc. Fig. 3 shows the relationship between the voltage ratio Vn ¹ / Va and the jet current. A solid curve a in Fig. Shows the operating characteristics of the known system according to Fig.1 · From this it can be seen that the voltage ratio vV / V ,, around + 0.6? Beam current of 1.5mA compared to the ratio of the beam; current zero increases.

In order to optimally focus the electron beam; To obtain, it is generally desirable to use the Spanriungsvahältnis ¹ Vi ,. ¹ / Va to hold essentially constant or to lower the voltage ratio with the increase in the beam current, namely preferably by about 0.5% relative to the changes

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of the beam current from 0 to 1 mA »However, the familiar is sick System because the voltage ratio vV / va is with the increase in the jet current / increases, so. that the desired best beam focusing cannot be obtained even if the variable resistor 12 is set so that it has the best beam focusing at a certain value of the beam current results.

In Fig. 4, an embodiment of the invention is shown which avoids these disadvantages. In FIG. 4, the same reference numerals are used for the same parts as they also appear in FIG. 1, and a detailed description! the mode of operation of these parts is not required. The cathode ray tube feed according to FIG. 4 differs from the system of FIG. 1 in that a parallel connection of a! Resistor 13 and a capacitor 14, each grounded to a terminal, are connected in series with a common ground terminal G of the triple voltage multiplier and rectifier circuit 8 and that the series connection of the resistors 10, 11 and the variable resistor 12 between the common terminal G. and the output terminal F of the single rectifier circuit for deriving the focus voltage "V ™ ¹ from the connection point between the resistors 10 and 11 is connected.

Fig. 5 shows an equivalent circuit for the circuit ^ part for deriving the focus voltage V ™ ¹ . In Fig. 5, resistors B ₁ Q, B ₁₁ , E ₁ ^ and B ₁ * correspond to resistors 10, 11, 12 and 13, respectively, of Fig. 4. In Fig. 5, the focus voltage "VV is given by the relationship

^{Έ S} E ₁₀ - + E ₁₁ + E ₁₂ - ^K 10 + ' ^Κ 11 ^{+ M} 12 ^b

where E -] ^ as E ₁ Q, B ₁₁ , E ₁ Ot ^un ^ Iu = mean value of the dur.oh the common ground terminal G flowing current that leads to

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is proportional to the beam current flowing in the cathode ray tube. If, therefore, it is assumed that the output voltage Vp of the simple voltage multiplier and equalizer circuit is constant, then it follows from the above equation that the focusing voltage V, -, ^{1 is} reduced as the beam current increases. The reduction ratio of the focused voltage Vp ¹ can be freely set by appropriately selecting the resistance value of the resistor 13. More precisely; represents, the voltage ratio V ^ ¹ / V ^ can be selected by appropriately selecting the resistance value of the resistor R ^, although the output voltage Va and the focus voltage Vj ₁ ¹ change with the increase of the beam current during normal operation, and thus an optimal beam focusing can be achieved over the entire range of variation of the beam current. The dashed curve b in FIG. 3 shows the relationship between the voltage ratio Vp ¹ / V. and the jet current, as it is with the inventive system according to fig. 4 can be observed.

The sizes of the elements according to FIG. 4 can, for example, have the following values:

C = 1000 pF; D «diodes H 435; Ii ₁₀ = 20 mils; B ₁₁ = 28MU-; R ₁₂ * TO MJL; R ₁₅ = 220 kilograms; C ₁₄ = 0.01 μ ¥,

The previous description related to the application of the invention to a triple voltage multiplication and a rectifier circuit in which the number η of the diodes or capacitors is six. The invention can, however also to a double voltage multiplier and rectifier circuit apply, where η = 4, to a quadruple voltage multiplier and rectifier circuit with η β or to any multiplication circuit with a different multiplication factor, where η is greater than 8.

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Fig. 6 shows the application of the invention to a ' dual voltage multiplier and rectifier circuit. The same reference numerals denote the same parts as in FIG. 4. The operating principle of the circuit according to FIG. 6 is the same that of the circuit according to FIG. 4 and does not need a detailed description.

Fig. 7 shows a modification of the system of Fig. 4 in which one of the capacitors in the first stage is omitted.

Fig. 8 shows another modification in which one of the capacitors in the third stage is omitted. the The mode of operation and the technical quality of these modifications correspond to the embodiment according to FIG. 4. The omission of the capacitors is also possible with other voltage multiplier and rectifier circuits where η = and where η ^ -6. In a further modification, which is shown in Fig. is shown, the capacitor which is directly connected to the flyback transformer 7 is omitted. Also here. Correspond the method of operation and the technical quality of the execution are those according to FIG. 4.

Fig.-10 shows a further embodiment in which instead of the series connection of resistors 10, 11 and 12, the series connection of resistors 15, 16 and a variable resistor 17 is used to derive the focus si he voltage Vj ₁ ¹ , by the output voltage , that is, the anode voltage V ^ supplied by the triple voltage multiplier and rectifier circuit 8 is divided. Here, one terminal of the variable resistor 17 is connected to the common basic terminal G and the parallel connection of the resistor 13 and the capacitor 14 is connected between the terminal G and earth ", as in FIG. 4. This Embodiment results in better beam focusing over the entire range of change

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of the jet stream. The voltage ratio Vp ¹ / V * is constant when the resistance value of the resistor 13 in the parallel circuit is zero. However, when the resistor 13 has a given resistance value, the voltage ratio Vp '/ V increases. with the increase in the beam current, and the desired optimal beam focusing can be obtained.

Fig. 11 shows a further embodiment of the invention * Here, the same reference symbols denote the same parts as in FIG. 1. The feed according to FIG. 11 differs from that of Fig. 1 in that a diode 21 with its anode at a central tap of the flyback transformer 7 and with: its cathode is connected to earth via a parallel circuit of a capacitor 22 with a resistor 23. The terminal voltage of the resistor 23 is applied to the terminal of the series circuit 10, 11, 12, which is grounded according to FIG.

In the system according to FIG. 11, the horizontal eye pulse is rectified by the diode 21 and then smoothed by the capacitor 22 so that it is applied as a direct voltage to a terminal of the resistor 23, namely to a point H. An increase in the beam current leads to a larger pulse width of the horizontal output pulse. The pulse voltage is therefore lowered and the voltage appearing at point H is also lower. At the same time, the focus ^{voltage Vp 1} is also reduced due to the lowering of the output voltage Vp of the first section of the triple voltage multiplier and rectifier circuit 8. In this way the Spannungaverhältnis Vp ¹ / Va can si between the focus he voltage Vp ¹ and the anode voltage V ^l "with the increase of the beam current, the load is reduced so with [the rise, so that the ge ™ | The characteristic drawn in dashed lines at b in FIG. 3 is obtained. In this case, the anode span Va is also reduced, but the reduction ratio of the anode

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voltage V * small compared to the reduction ratio of the focus voltage Vp ¹ . The voltage ratio "VV / V" is thus reduced in the manner described.

Between the resistance values R ₁ Q, R ₁₁ , R ₁₂ and B ₂ * of the resistors 10, 11, 12 and 23, the condition must be fulfilled B ₂ * ^ as R-1Q »R-] ι» Rio · - ^ ^er The reason for this is that if the resistance value B ₀ * of the resistor 23 is greater than that of the resistors 10, 11 and 12, a correspondingly higher voltage occurs at the point H and the smoothing capacitor 22 must have a higher capacitance. In addition, this condition is required insofar as the occurrence of a voltage higher than the pulse voltage at point H leads to the diode 21 being blocked. · '

Good results are obtained when, for example, the resistance _{values E 1} Q, E ₁₁ , B ₁₂ and B ₉ * of the resistors 10, 11, 12 and 23 as well as the capacitance C _{22 of} the capacitor / are measured with the following values:

E ₁₀ = 50 MJl-; R ₁₁ = 28 MAj R ₁₂ = 10 MiL; R ₂₅ = 270 kIL; C ₂₂ = 0.1; iF.

By applying the horizontal output signal of the flyback transformer 7 to the diode 21 and the capacitor 22 DC voltage obtained can be used as a screen voltage for conventional television receivers. The system according to FIG. 11 ι can therefore not only be used to control the focus voltage} but also as a means for maintaining a screen voltage. ,

Fig. 12 shows a partial modification of the feed according to 11. According to FIG. 12, the transformer 7 has a tertiary transformer 7a, so that the voltage induced in this tertiary winding for obtaining the voltage for adjusting the focus voltage can be rectified. 'The tertiary winding 7a proves to be beneficial in that even if the Horizontal output pulse supplied by the flyback transformer vu.i of negative polarity is that. Polarity of the pulse in positive polarity can be converted. - 12 -

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FIG. 13 shows a further modification of the system according to FIG. 11. Here, instead of the three-fold voltage multiplication and rectifier circuit 8 according to FIG. 11 a double voltage multiplication and rectifier circuit used; the mode of operation and the technical advances of the feed system according to FIG. 13 correspond to those according to FIG. 14 shows a further modification of the feed system according to FIG Fig. 11, in which the voltage multiplier and rectifier circuit 8 is replaced by a single rectifying high-voltage diode 24 and the resistor 10 is connected to the output side is, i.e. to the side of the diode 24 that supplies the anode voltage. ■ '·

Fig. 13 shows a further embodiment, the same Reference numerals denote the same parts as in FIG. A detailed description of the nasty way of working Parts is not required.

15 is a parallel circuit of a resistor 31 and a capacitor 32 connected in series with the secondary winding of the flyback transformer 7, and to the Connection point J between the secondary winding of the flyback transformer 7 and the terminal of this parallel connection closes the one terminal of the variable resistor 12 from the Reil'Beschaltung the resistors 10, 11 and 12 on. The parallel connection the resistor 31 and the capacitor 32 are grounded on their opposite side.

When the load current flows to the cathode ray tube 9, a negative voltage occurs at point J through the high-voltage winding of the flyback transformer 7. This negative voltage increases with the increase of the load or beam current and the focus si er voltage Vr ₁ ¹ decreases with the reduction of the output voltage Vt ₁ , the first section of the triple voltage multiplier and rectifier circuit.

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The iinode voltage V. also decreases in this case, but the reduction ratio of the anode voltage Va is small compared to the reduction ratio of the focusing voltage Vji ¹ . The voltage ratio Vj <'/ V »between the focusing ^{voltage Vp 1} and the anode voltage V / thus decreases with the increase in the load current and the relationship between the voltage ratio V-p' / Va and the load current changes in the dashed line at b in Fig 3 way shown. Between the resistance values R ^, R-.q, R ₁ -, and R ^ der

Resistors 31, 10, 11 and 12 must have the relationship R ^^ jq IL-j, 1 (^ 2 must be fulfilled. Good results are obtained if these resistance values and the capacitance C ^ o of the capacitor are set to the following values:

R ₁₀ = 50 VI SL; JLt ₁₁ = 28 mils; R ₁₁ = 10 mils; K ₃₁ = 270 UI; C ₃₂ = 0.1 µF.

Mn the same result can be achieved if the triple voltage multiplier and rectifier circuit 15 is replaced by another voltage multiplication and rectifier circuit in which the factor 2 or is greater than 3, or by a direct rectifying circuit.

Fig. 16 shows such a modification using a direct rectifying circuit. Here, a rectifying Iloch voltage diode 33 is connected with its anode to the secondary winding of the flyback transformer 7 and with its cathode to the anode of the cathode ray tube 9 and to one terminal of the resistor 10. The mode of operation and the technical quality of this modification correspond to those of the systems according to Fi; -. Previous year

- 14 ORIGINAL BATHROOM

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Claims (6)

- 14 patent claims: ΓΟCathode ray tube supply with a high-voltage rectifier device for rectifying the flyback pulses supplied by a flyback transformer, the rectified output high voltage of this high-voltage rectifier device being applied to the anode of a cathode ray tube, characterized by a beam current change detector (13, 14; 22, 23 ; 31, 32) for detecting changes in the beam current and for providing an output signal which, as a function of the changes in the beam current ^: changes; by a device (10, 11, 12) for combining the output signal of the detector with a rectified output high voltage of a high voltage rectifier device (24, 33) or - if the high voltage rectifier device is an n-fold voltage multiplier and rectifier, Richter circuit is - the output voltage of an m-fold voltage multiplier and rectifier circuit in the η-fold voltage multiplier and rectifier circuit, where m and η are positive integers and m «n, to obtain a resulting DC voltage whose reduction ratio is less than or equal to the reduction ratio of the rectified output Iow voltage due to a change in beam current; and by means for applying the resultant DC voltage to the focusing electrode of the cathode ray tube (9). 2. Cathode ray tube power supply according to claim 1, characterized characterized in that the high-voltage rectifier device is in the form of the η-fold voltage multiplier and rectifier circuit (8) is constructed and that the detector consists of a parallel connection of a resistor (13) and a capacitor (14) exists between earth and a common Ürundklemme (G) of the m-fold voltage multiplier and rectifier. 309827/0848 circuit are connected, and that the means for combining the voltages from a series circuit of a plurality γόη resistors (10 ,, It, 12) exist between the parallel connection and the output terminal of the m-fold voltage multiplication and rectifier circuit exists within the n-fold voltage multiplier and rectifier circuit and the Focusing voltage from the connection point between two resistors (10, 11) of the resistors forming the series circuit are tapped is. 3. Cathode ray tube supply according to claim 2, characterized in that fixed resistors in the series connection (10, 11) and a variable resistor (12) one behind the other- ' are connected and that the resistance value of the variable resistor can be adjusted to select the focusing voltage. 4. cathode ray tube supply according to claim 1 _t, characterized in that the detector comprises a diode (21) for rectifying the flyback pulse occurring at the flyback transformer and a capacitor (22) for smoothing the rectified voltage supplied by the diode. 5. Cathode ray tube supply according to claim 4, characterized in that the flyback pulse transformer (7) has a tertiary winding (7a) which is connected to the diode (21) (Fig. 12). _: 6. cathode ray tube supply according to claim 1, dadurcq characterized in that the detector consists of a parallel circuit einjes Resistor (31) and a capacitor (32), which are shown in Row with the high voltage winding of the flyback transformer (7) are connected, and that the voltage is applied to this parallel connection serves as the detector voltage (Fig. 15, 16). 309 8 27/0 8 48