DE1151546B - Circuit arrangement for generating a saw tooth current in a coil and a high voltage - Google Patents

Description

The invention relates to a circuit arrangement for the simultaneous generation of a sawtooth-shaped Current through a coil and a high voltage by means of an amplifier stage, whose Input an at least approximately sawtooth-shaped control signal which periodically blocks this stage is supplied and the output of which is connected to a primary winding of a transformer with the further a saving diode and the mentioned coil are coupled, wherein the rectifier circuit for Generating the high voltage is connected to a secondary winding of the transformer and wherein there is also a stabilization circle.

Such arrangements are used, inter alia, in television receivers, the sawtooth current the deflection coil flows through to the electron beam in the with the magnetic field generated in this way Deflect playback tube. The high voltage generated is used to feed the display tube used.

In modern receivers, this circuit arrangement is always provided with a stabilization circuit, by to some extent the effects of load changes on the sawtooth Deflection current and / or to be balanced on the high voltage.

If for any reason, e.g. B. as a result of a change in the supplied video signal, the beam current increases through the display tube, it means that at almost the same high voltage the current load on the high-voltage circuit increases. Through the stabilization circuit of the deflection circuit together with the transformer, the high voltage remains almost constant; however, must be an increase in the beam current through the display tube of the circuit is correspondingly greater Power can be supplied.

In the conventional circuit arrangements of this type, this condition was met by that the bias voltage for the amplifier element feeding the primary winding through the stabilization circuit was changed. If a penthode was used in this amplifier stage, it was found that the Anode peak current could increase considerably, especially more than for the necessary enlargement the value of the deflection current at the end of the outward run would have been necessary. A A larger anode peak current also requires a correspondingly larger lattice voltage, so that as a result, the screen grid power dissipation increases. In addition, the exposure to the high peak current to generate the service life of the cathode circuit arrangement

a sawtooth current in a coil

and. a high voltage

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative: Dipl.-Ing. E. E. Walther, patent attorney, Hamburg 1, Mönckebergstr. 7th

Claimed priority:
Netherlands of December 30, 1958 (No. 234 707)

Hendrik Heijligers, Eindhoven (Netherlands),
has been named as the inventor

and thus the whole tube is considerably reduced.

In a circuit arrangement of the type mentioned at the outset, this can be avoided if according to of the invention as a function of the change in a load connected to the high voltage Inclination of the sawtooth-shaped control signal is changed and / or the apex of the sawtooth is flattened such that the control signal together with a bias voltage taken from the stabilization circuit den Peak value of the current supplied by the amplifier stage with a variable high voltage load only changes so much that the current through the saving diode at the outgoing end is zero.

Some possible embodiments of a circuit arrangement according to the invention are given below described on the basis of the drawing.

Fig. 1 shows a simplified current diagram of the known and improved according to the invention Circuit;

Fig. 2 shows the control signal for the amplifier tube, via which the circuit is supplied with the required current will;

3 shows a circuit arrangement according to the invention;

Fig. 4 shows a current diagram similar to FIG. 1 in a circuit in which another control signal of the Amplifier tube is supplied as shown in Fig. 5;

309 647/111

FIG. 6 shows a modification of the circuit arrangement according to FIG. 3, with a control signal according to Fig. 5 is obtained.

Fig. 1 shows the course of some currents of the circuit over time / during a period T of the sawtooth current, which consists of a forward interval Tu and a return interval Δ Τ . The diagram contains the anode current i _{a of} the amplifier tube 2 according to FIG. 3, which the primary winding of the transformer because the high voltage or the deflection amplitude is kept essentially constant by the stabilization circuit, this additional power from the amplifier tube of the circuit during the trace Tj _{1 are} supplied.

The high voltage is obtained from the high voltage pulse occurring in the return interval Δ Τ , which results when the deflection current i _s stored in the coil at the end of the trace

mators 4 between the tapping point 3 and the anio cherte magnetic (reactive) energy to the parallel The end point of the spar capacitance, which is earthed on the other side, swings over to the coil effective.

As the load increases by reducing the size of the resistor 10, the circuit must have more Energy are supplied, which is then available in the coil at the end of the forward run; it must

thus the reduced deflection current - be greater at time U; In the diagram there is therefore a difference

diode capacitor (booster capacitor) 1 flows through, as well as the reduced deflection current, transformed into the same primary winding - - and the saving diode current reduced in the same way - - . It is

n _a

Tl ₁ = - ■
Ks

and η, = -,

where n _a , na and n _s denote the number of turns of the transformer 4 through which the anode current ia, the diode current u and the deflection current i _{s flow.}

Taking into account the directions indicated in Fig. 3 for _a and i ia is in every moment bung from B to G. Because the slope of the sawtooth is to remain unchanged, the result is the same displacement at Hinlaufanfang from A to D,

and the deflection current - takes the dashed line in Fig. 1 -

H ₁

Is

= la -

Tl ₁

(2) the dotted course from D to G. In the current-time diagram according to FIG. 1, the areas between the curves and the abscissa indicate current integrals which, taking into account the associated voltages, correspond to amounts of energy and, taking into account the time or the re-

M ₂ 30 recovery frequency also indicate the power. So far

when the deflection current i _s is concerned, it is a question of reactive energy or reactive power; the anode current that flows in from the supply source F & indicates the active power supplied.

In FIG. 1, the surface O _{1 of} the triangle B, t _x , t ₂ corresponds to the reactive energy which is supplied to the total inductance formed by the transformer 4 and the deflection coil 7 when the beam current is low.

The area O _{2 of} the triangle A, O, t _x corresponds to the inclination of the deflection current is 40 reactive energy, which is kept constant at a low beam current, that during the outward Tn termination of the return and thus after energy the difference in the voltage across the capacitor 1 and the output to the rectifier circuit back again battery voltage Vb via the conductive diode 5 is obtained, preferably by charging the winding n _a . Thus, since the voltage booster capacitor 1. The difference between the constant, results in a linear confining surfaces with time 45 O ₁ and O ₂ corresponds to the extracted increasing current i _s in the deflection coil 7. The high-voltage power control, thereby excluding occurring voltage 6 is chosen so that by the
Battery Fb incoming anode current i _a the losses
of the circuit and that at the end of the

The reduced deflection current running between points A and B - is therefore the difference of the

H ₁

extending between the points O and B anode current ia and extending between the point A and the abscissa at t ₂ reduced the diode current -.

Trace at time t _{2 of} the be losses in the circuit according to formula (2).
When the high voltage circuit is heavily loaded

of the reduced deflection current -

and increase

areas O ₁ result in accordance with the curve DG

conditional diode current reaches zero.

If the efficiency of the circuit changes,
the energy supply must also be changed. One
such a change in load occurs when the
Current through the display tube and thus the 55th
Resistance 10 changes. The resistor 10 is on that
the high voltage supplying rectifier circuit is connected, the one from the one with the secondary winding
(which is formed by the part of the transformer 4
which contains the turns n _a + nn ) connected 60
Rectifier and the smoothing capacitor9. In the case of a television display tube
the jet stream z. B. change from 50 to 500 μΑ; the
means that if the high voltage remains almost the same, the value of the resistor 10 in the ratio 65 does not find any further path, the mean 10: 1 must change. If the high voltage is 16 kV, the anode current i _{a will be} equal to the mean diode current i & will be at the mentioned increase in the beam current. The mean anode current is proportional to the increase in the power to be applied from 0.8 to 8 W. Area between the current curve i _a in Fig. 1 and the

and O ₂ ' corresponding to the triangles G, / ₂ , I ₁ and D, O, ti, the difference of which corresponds to the greater high-voltage energy; so this energy is proportional to

(O ₁ '- O ₁ ) - (O ₂ - O ₂ ').

This amount of energy is just proportional to the

Surface ABGD between the lines - and -.

> h "1

If the high voltage load is greater, the line of the reduced deflection current shifts.

Since the current from the battery F & is on both the Diode 5 as well as through the tube 2 flows and normal-

Abscissa, while the mean diode current is proportional to « ₂ times the surface area between

the curve of the reduced diode current - and

the abscissa.

For the function of the circuit at a higher load it results under the effect of the stabilization circuit, by which the inclination and thus the amplitude of the deflection current 4 is largely constant is held, the following:

as it corresponds to the increase in the reduced deflection current, so that the diode current is just zero at the end of the trace. As a result of the lower inclination of the control voltage, the curve H ″ - G results for the anode current VJ , during the

reduced anode current

from D " to the

The current i _s must change into a current W in such a way that the required additional energy or power for the high-voltage circuit can be supplied, as has been described above.

The mean values of the anode current i _a and of the diode current ia must increase so that their mean values are again almost equal to one another.

In order to obtain the required linear deflection current, according to formula (2) in at every moment during the outward run:

W ₁ " «2 '

In the circuit arrangements customary up to now, this was achieved in that the negative bias voltage runs on the abscissa at t ₂ by means of the stabilizing device. The mean values of the currents meet the existing conditions, in particular for the delivery of the required energy, but the increase in the anode current is relocated more to the start of the incoming flow, which is at low values, and thus an inadmissible increase at the end of the flow is avoided.

In order to obtain the required change in the control voltage, that of the tube 12 delivered, pulsed current integrated by means of a network, which consists of a capacitor 13 and the parallel connection of a resistor 14 and a discharge tube 15 consists. At the anode of the tube 2 and the capacitor 13 creates a voltage 6 which gradually increases during the run-out and assumes a high negative value during retrace, as shown in FIG. Dependent on of the extent to which the tube 15 is open and, by virtue of its internal resistance, the value of the parallel connection changes with the resistor 14, the trailing of the voltage will show different tendencies between lines 16 and 17 in Fig. 2. The

Control grid of the tube 2 was reduced when the 30 held control voltage 6 is via a condenser

High voltage load increased. Since on the one hand the mean anode current and the mean diode current must be the same, while on the other hand via the formulas (2) and (4) also via the transmission ratio between the one connected to the tube 2 Winding and the winding part connected to the diode 5 are linked to one another, the result is that with unchanged, z. B. linearly increasing control voltage 6 for the during the trace Sator 18 is fed to the control grid of the tube 2.

The stabilization device, which consists of a voltage-dependent resistor 19 and a potentiometer circuit 20, 21, 22 and 23 as well as from the capacitor 24, provides a negative bias voltage, which is also fed to the control grid of the tube 2 via the resistor 25. The DC setting this stabilization circuit takes place by means of the potentiometer circuit mentioned, the

Tube 2 the anode current at the outgoing end / ₂ essentially 40 is parallel to the booster capacitor 1. This potential

Lich increases more than it corresponds to the increase in the deflection current (Z ₅ or i _s '). In itself, it would be sufficient if the anode current, which enttiometerschaltung around the curve OB at the lowest high voltage load, loads the booster voltage only slightly, so that the above-mentioned condition that the mean anode current and the mean diode current must be the same, practically does not change Ü

pgg g p

speaks, at time t " until the value G increases, 45 becomes. About the capacitor 24 of the

so that at this point the diode current would just be zero. As a result of the aforementioned bias tapping 26 of the transformer 4 the stabilization circuit, in particular the resistor 19, the Return pulses supplied and result in rectification at resistor 19, the desired

change, however, shifts the anode current curve to the curve H'-G ', while at the same time the

Diode current shifts to curve /) '- P. As a result, 50 preload. This is due to the amplitude of the disadvantages mentioned at the beginning of a guided pulse and the DC voltage at the undesirably high load on the tube 2, in particular

especially with regard to the cathode peak current and with regard to the screen grid power loss.

Capacitor 1 dependent; in the case of small changes in these voltages, which result from changes in the load in the high-voltage circuit, the bias voltage for the tube 2 then also increases in practice as a result of the non-linear curve, along the anode current-grid voltage characteristic curve, which results in the required change in the voltage across the with the control voltage unchanged, the current at the end of the tube 2 to the transformer 4, the energy of the outgoing flow, which is fed to the transformer 4, becomes even stronger in such a way that it occurs and stabilization is achieved.
Curve H'-G 'is noticeably steeper than the curve If, for example, the high voltage load increases,

OG, so that the peak peak current is even greater 60, the negative value generated by the resistor 19 is. Bias for the tube 2 less, so that the

According to the invention, these disadvantages are thereby increased the mean current through the tube 2. then avoided that the shape of the Sieuers voltage increases, the voltage drop across the through the changes as a function of the exposure fluctuation. Capacitor 27 for alternating current bridged Ka-thereby it can be achieved that in combination resistance 28 on. With the cathode of tube 2

act with the changing negative bias voltage supplied by the stabilization circuit, the anode peak current at time U only increases to the extent that the cathode of the tube 15 is connected; the tube 15 is set in such a way that with a small or very small beam current through the display tube a certain

7 8

Current flows in the tube 15 and this therefore causes an anodic change in the slope of the control voltage 6 side has a small internal resistance. increases. If the capacitor 18 were not present,

If the voltage at the cathode of tube 2 would have to change the negative grid voltage, rises, then the current through the tube 15 supplied by the stabilization circuit becomes as above less, their internal resistance is greater, and thus 5 must be taken into account.

the time constant of the integration element 13, 14 increases, the change in the resistance part of the

15 such that the voltage grationsnetzwerkes 13, 14, 15 does not necessarily need in the trace interval rises less and thus the slope becomes less. made by means of a discharge tube 15 to If they are at the slightest high voltage load. The elements 14 and 15 can, for. B. by Control voltage 6 corresponds to line 16 in Fig. 2, io a non-linear resistance element, such as a spanso decreases - with the voltage-dependent resistance (VDR resistance) remaining the same Tube 12 supplied pulse-shaped current - are set to which a voltage is supplied, with increasing high voltage load the control which is taken directly from the high voltage circuit. voltage 6 more and more by the curve 17 This can, for. B. can be achieved in that the indicated course. The anode of the diode 8 also changes via a capacitive voltage mean Value of the control voltage, which is connected to earth in the curve 16 divider and a rectifier the line 29 and at the curve 17 on the line 30 circuit to the tap of this voltage divider lies. Since the capacitor 18 direct current is not over-connected. That of the rectifier circuit carries, the control voltage 6 is increased by the voltage taken from the voltage line 29 given mean value oscillate, while 20 dependent resistance (14, 15) for setting the this mean value in the course of the curve 17 are fed to the operating point. Is the burden is on line 30. If the stabilization circuit is low, the amplitude is that supplied to diode 8, negative bias and voltage-controlled kickback pulses high. The one from the drop across the resistor 28 determine the potential further rectifier circuit supplied DC-voltage, the voltage corresponding to lines 29 and 30 is thus also high, and as a result of this pre-mean value In the grid control area of the tube 2 clamped is the resistance value of the voltage decreases. dependent resistance for the tube 12

The stabilization circuit causes the supplied alternating current to be low; the inclination of the jj · _t ALI 1 ^ h ' τ- jj TT- sawtooth part that occurs on the integration link

the reduced deflection - ± - at the end of HM _{3o Ste} ^ö _{uerspannung is thus} relatively steep. Takes

run the point Gerreich. The control of the tube5 increases the load, so the amplitude of the return is reduced adjusted so that taking into account the impact pulse and thus the preload on the spanderen Voltages in the control circuit and the slope-dependent resistance, so that its resistance changes of the tube 2, the inclination just increases and the inclination of the sawtooth changes is that the anode current is corresponding to the 35 parts less steep. The resistance value is Line // - G in Fig. 1 runs. Admittedly, neither have they actually suffered from the high voltage load Control voltage according to FIG. 2 still dependent on the currents.

Fig. 1 actually shows an exactly time-linear course, although the linearity of the trailing part of the

but have certain curvatures. This is control voltage through the effect of the voltage

to be taken into account in the practical assessment; 40 dependent resistance decreased. However, this is

in principle, the above considerations are not essential, since the inclination of the deflection current i _s

valid, only the ease of illustration, and i and _s' by the control voltage, but

Explain because of linear changes. by the during the run over the saving period

Also, line 29 in FIG. 2 does not need a constant circuit located on the transformer

to go through the point at which the trailing edge 45 DC voltage is caused and largely un-

of the negatively directed pulse in the sawtooth is over-dependent on the course of the anode current i _a .

goes; the line 29 can in particular also be lower. A change in the course of the anode current causes

lie, in particular in that the amplitude only shows a corresponding change in the course of the

of the negative-going pulse-shaped part is greater than the diode current u such that the formula (2) is satisfied

is. In this case too, correct input 50 can be used.

position of the negative bias the time A second embodiment is shown in Fig. 6 dardes Unlocking the tube 2 can be determined. When asked, and that of this circuit arrangement for the setting of the tube 15, it should be noted that the associated, reduced current diagram is shown in FIG it lies in a circle of positive feedback. At and the control voltage supplied to the tubes 2 increasing mean flow through tube 2 55 is illustrated in FIG.

namely, the inclination of the sawtooth becomes less steep. In this embodiment, the shape of the As a result, if the output voltage remained unchanged, the control voltage would be changed by the fact that the anode potential corresponding to the line 29 - the voltage of a one-sided conductive element 32 with the Kon while of the trail in all points higher positive capacitor 13 is connected, being connected to the cathode so that the mean current becomes even more positive and variable as a function of the load would take, whereby the voltage 28 is in turn supplied voltage. This is achieved by increase and the tendency of the outward flow of the control that this cathode on the one hand via a resistor 33 tension would be further flattened; this back to the anode of the video output tube 34 and on the other hand The coupling process could increase the stability of the arrangement via the resistor 35 with the variable arrangement endanger. In that the control voltage 6 65 tap of the resistor 36 is connected. This passed The capacitor 18 is fed, the variable tap is mechanically shifted with that of the However, the output potential is such that the resistor 37 is coupled while the resistors mean flow through the tube 2 not connected crosswise and as a result of the 36 and 37

9 10

between the plus terminal of a supply voltage signal 40 to be caused. Will the source and earth are connected. The variable tap 37 is shifted to the right, so the tap of the resistor 37 increases via a resistance beam current through the tube 39, but at the same time the potential at the cathode of the element 32 tube 39 was connected to the Wehnelt cylinder of the display. 5 as a result of the tapping of the resistor 37. The mode of operation is as follows: The tapping of the resistor 36 coupled to the anode. The signal 40 taken from the video output tube 34 is also flattened. Both the changes in the video signal and the change resistance 33 of the cathode of the element 32 for the brightness setting have thus shaped the cathode of the display tube 39. If the signal 40 becomes less positive, then the result is changes in the control signal, this with a fixed position of the variable connection Display tube 39 increases. At the same time will lead. However, if care is taken to make the change the cathode of element 32 less positive. the negative grid voltage to the change in shape The setting of the element 32 is chosen so that 15 of the control signal is adapted, so the signal 6 that, if the two taps of the resistors 36 are fed directly to the control grid of the tube 2, and 37 in the extreme left It is also not necessary to always use a pentode as a switching tube, the potential of the signal 40 always corresponds to the black level. The potential at the cathode of the element 32 of the straight transistor can also be used for the present purpose at the apex P of the control 20 shown in FIG. If the cathode thus achieves the most favorable modulation when the control current is applied, the effect of the signal 40 becomes less positive. This control current can, in principle, make the element 32 conductive, and the peak P of the signal 6 can be achieved by flattening the aforementioned generator. This is generated, for example, in FIG. 5 by the control voltage according to FIG. 2 or 5, the broken line 41 indicated. 25 via a high resistance to the control electrode. If the mean value of the transistor is connected without flattening, so that the generator signal 6 is again indicated by the line 29, so it assumes the nature of a current source. This value can also be desired after flattening by the line 42, the stabilization device being indicated in this way. If the negative grid voltage remains to be measured so that the peak value of the deflection current U of the tube 2 is constant, the control voltage, 30 is not kept completely constant, but because in this case too the signal 6 across the condenser decreases to some extent. If i _si which is fed to a sator 18 is called the negative amplitude of the oscillating around the same mean value beam current zero, so that in the lattice space of the tube 2 deflection current 4 and i _S2 the maximum value given by the line 41 under the same conditions occurring positive amplitude, then it is shifted in the direction of the apex P. The 35th

Stabilization circle reduces the negative grid voltage i _si + z _S2 = i _s , to the extent that the line 41

passes above the apex P , whereby the anode, ie the peak value of the deflection current. Vu is the peak current of the tube 2 to a value i _a ' ent. Supply voltage for the display tube 39. It can increase according to the line section Lt ₂ in FIG. Be detected 40 that the image dimensions of this peak current increase must remain constant as much straight as applies with some approximation: amount that the reduced deflection indicating line - from the lowest layer (corresponds -r-- = - = _r - ; -

«1 z _s 2 Vu

speaking no beam current through tube 39) 45

according to the position indicated by the line * '^ ^{obei Δί} ° ^ηαά _Α ^ÄV * f changes in the deflection

H ₁ ° ^ba current or the high voltage when changing the

shifts, corresponding to denote by the signal 40 beam current. It follows from this that if the beam current increases, with the beam current increasing, the voltage Vi ₁ need not be zero through 5 at the end of the trace time. 50 needs to remain constant, so that since the negative bias of the tube 2 abgenom- of the high voltage output has less men, the flattened control voltage 6 will also increase than if this would otherwise be the case, in a steeper part of the z _a - «srKennrinie lie, In addition, i _{s can} decrease, so that the line i _a ' in so that the line section L"L' of the current W is somewhat canted in relation to the reduced current diagram around the point B compared to the line which the current i . _a. the adapter may edges 55 Focus This means that the top indicates the flattening and the edges of the sawtooth area of triangle f _1; B, t ₂ with respect to the surface-shaped part of the control voltage must be such of the triangle O, I ₁ , A will increase, which already shows that the mean anode current is almost the same again, that there is a certain decrease in the mean diode current; in other words, the degree of efficiency can be partially absorbed without that of the Line sections OL ", L" L ', L ¹ L, Lt ₂ 60 that the anode peak current needs to increase, and t ₂ O enclosed surface must be equal to « ₂ times by the decrease in the high voltage and by that of the line sections O t ₂ , t ₂ M, M, M ' and decrease in the peak value of the deflection current can be MO trapped surface. In this case, too, the increase in the anode peak current, the currents will not be reduced to a minimum from the pure linear ones, despite the increase in the course according to FIG. 4, but rather to some extent in the beam current.

be curved. If desired, the measures

The potential changes at the cathode of FIGS. 3 and 6 are combined so that

Element 32 need not only from the video and a change in the inclination of the sawtooth

'309 647/111

shaped control signal as well as a flattening of the same occurs.

Claims (7)

PATENT CLAIMS: 1. Circuit arrangement for the simultaneous generation of a sawtooth-shaped current through a Coil and a high voltage by means of an amplifier stage, the input of which a this stage periodically, blocking, at least approximately sawtooth-shaped control signal is supplied and their Output is connected to a primary winding of a transformer, with which further a saving diode and said coil are coupled, the rectifier circuit for generating the high voltage is connected to a secondary winding of the transformer and further a Stabilization circuit is present, characterized in that depending on the change a load (10) connected to the high voltage (9) the inclination of the sawtooth-shaped Control signal (6) changed and / or the vertex of the sawtooth is flattened in such a way that the Control signal together with a bias voltage taken from the stabilization circuit Peak value of the current supplied by the amplifier stage with a variable high voltage load only changes so much that the current through the saving diode at the outgoing end is zero. 2. Circuit arrangement according to claim 1, in which the amplifier stage consists of a discharge tube exists, to which a negative bias voltage taken from the stabilization circuit is fed, characterized in that the control signal is transmitted to the control grid via a blocking capacitor Discharge tube is supplied. 3. Circuit arrangement according to claim 2, in which the sawtooth-shaped part of the control signal is achieved by means of an integrating network, which consists of a resistor and a capacitor consists, to which a pulse-shaped signal is fed, characterized in that the value of the Resistance is changed by means of the control loop depending on the change in load. 4. Circuit arrangement according to claim 3, characterized in that the resistance element of the integrating network through a voltage-dependent resistor (VDR resistor) is formed, to which a voltage originating from the rectifier circuit is supplied, which rectifier circuit preferably via a capacitive voltage divider with the secondary winding of the transformer is coupled. 5. Circuit arrangement according to claim 2, characterized in that the resistance element of the integrating network from the parallel connection of an ohmic resistor and a There is another discharge tube whose anode is connected to the connection point of the ohmic resistance and the capacitor and its control grid to the other end of the ohmic resistor is connected, while the cathode of the latter discharge tube to the cathode of the first called tube is connected, which cathodes via a through a smoothing capacitor bridged resistor with the remaining end of the ohmic resistor as well are connected. 6. Circuit arrangement according to claim 2 in a television receiver, wherein the sawtooth-shaped Part of the control signal is achieved by means of an integrating network, which consists of a There is a resistor and a capacitor to which a pulse-shaped signal is fed, thereby characterized in that the anode of a unilaterally conductive element with the integrating network is connected, the cathode of which is coupled via a resistor to the cathode of a display tube which is fed by the generated high voltage, the latter being the cathode the video signal is supplied. 7. Circuit arrangement according to claim 6, wherein the Wehnelt cylinder with the display tube a variable tap of a resistor connected to the terminal of a voltage source which provides the required Provides bias for the Wehnelt cylinder, characterized in that a second, also with a variable tap resistance crossed with the first mentioned resistance is connected, the two variable taps mechanically coupled to one another are while tapping the second resistor using another resistor the cathode of the unilaterally conductive element is connected. Considered publications:
German patent specifications No. 598 600, 606 709, 967 777; Swiss Patent No. 274 398;
"Philips' Technische Rundschau", July 1952, p. 8 until 1 sheet of drawings © 309 647/111 7.63