US2096982A - Deflecting voltage generator, more particularly for television receivers - Google Patents

Description

Gd, 3, 13? lg. SCHLESING ER ,0 2

DEFLECTING VOLTAGE GENERATOR, MORE PARTICULARLY FOR TELEVISION RECEIVERS Filed Aug. 24, 1953 E 3 3:5 K. z I I 17/1 uenfor:

Patented 4 Oct. 26, 1937 PATENT OFFICES 2,090,982 .narmc'rme von'raos cssnna'ron, MORE PARTICULARLY FOB TELEVISION BE-' Kurt Schieslnlcn'Berlin, Germany Application August 24,

' In Germany lplaim.

This invention relates to deflecting voltage generators, more particularly for the purpose of pro 'ducing, by cathode ray deflection, a, line screen in television receiving arrangements, and, gen-=- 5 erally spoken, has for its object to provide apparatus improved and simplified to such a degree as to be highly capable of use in commercial television receivers.

In particular, one object of the inventionis v a suitable arrangement and dimensioning of the 26' ments is such that the natural curvature of the charging characteristic of a condenser being ciharged by an ohmic resistance is kept ineflec-' t ve,

(3) That preferably means are provided to decrease retroactions of the load (the consumer) on the deflecting voltages.

As the requirement (2) is to be complied with by utilizing but a small portion of the available voltage supply, another object of the invention at) is to provide means for obtaining the necessary deflecting voltage amplitudes with a reasonable voltage supply. I

According to a further feature of the invention, the natural curvature of the charging tuneas tion of a condenser being charged through a resistance may to a certain degree be corrected by connecting a choke in series with said resistance or by even altogether replacing said resistance by a'more complicated network.

% According to still a further feature of the invention, means are provided for obtaining variation of the frequency of the deflecting voltages not only to any desired value, but also in a quasi automatic way to certain preferred frequencies.

The invention will be more'fully understood from. the followingdetailed description, if taken in connection with the accompanying drawing.

Herein I is the D. C. voltage supply, shown by way of example as a battery, which, though, may

be replaced by a main supply, including, if necessary, a rectifying device, and which need not be absolutely constant. The D. C. voltage turnished by the device I is applied through the.

medium of a current limiting series resistance adjustable, too. If the condenser .1933, saw No. 680,494. August, 1932 I (preferably one of the known modern ferric-hydrogen resistances devised for the passage of weak currents) to a glow discharge device 3, which, 'with the assistance of the resistors 4, 5, and 6, ma manner wellknown in the art, is Ii caused to ignite. It is well known that the voltages which may be taken from the electrodes terminating, or subdividing, .the discharge space of a glow discharge device as shown, are by far less subject to fluctuations than the original supply 10 voltages. The discharge device 3 thus acts as a "voltage stabilizer. With the use of. such a stabilizer voltages may be obtained which are constant within a few tenths per cent, and the constancy may be still improved by means of 15 connections known per se, for instance by the use of two'stabflizers. The voltage between two' electrodes of the stabilizer is utilized for charging the maincondenser 9 of the deflecting volt-' age generator, a further glow lamp I 0 serving 20 for the periodic discharge of the condenser 9 by becoming conductive as soon as the condenser is charged up to its ignition voltage. The charging of the condenser 9 takes place through an ohmic resistance I, which may be variable for 25 the purpose of frequency adjustment, and may, according to the invention, be furnished with a plurality of marked tapping points whereby certain preferred frequencies (for instance 60, and lines per image in the case of the gen- 3( erator being devised for generating line deflection voltages) may be obtained in an as it were quasi automatic way. The condenser 9 may be 9 is charged through a. purely ohmic resistance, the requisite 3: linear nature of the increase of voltage between the poles of 9' cannot be obtained but at the expense of utilizing, as well known, merely a small portion of the exponential chargin curve, that is, the maximum condenser voltage, upon the 4' reaching of which the discharge device I0 is actuated, is but a small fraction of the stabilizer voltage available. Let the admissible deviation of the charging function, from linearity amount to 5%. In this case one tenth of the available volt- 4 age may be utilized as maximum voltage between. the poles of the condenser 9. Accordingly, the time constant of the charging circuit determined by the values of the charging condenser and the resistance connectedin series therewith, 5 must be chosen to be considerably greater than the period of the relaxation oscillations to be generated, for instance 10-100 times this period. In'the case of a deviation of only 1% being adunited, the useful voltage is even-reduced to one 5 fiftieth of the available voltage. As according to the invention the arrangement is so devised that a voltage of 30 volts between the poles of the condenser 9 is sufficient, as will be explained below, and as a deviation of the charging function from linearity amounting to practically causes no disturbing effects, the available voltage is to be chosen at about 300 volts.

The above figures merely apply in the event of the condenser being charged through a purelyohmic resistance. By the use of suitably dimensioned inductances as shown at 8, a larger portion of the charging function may be made to be approximately linear. This effect is brought about by the fact that an inductance connected into the charging circuit, as it tends to level out all variations in the charging current first causes a delay in the charging action, and afterwards counteracts to the delay in said action which corresponds to the exponential curvature of the charging characteristic present with pure resistance charging. Similar effects may be brought about by the use of more complicated networks consisting of ohmic, capacitative, and inductive resistances.

By using connection systems of this sort, the useful fraction of the available voltage may be increased, so that in the case that, moreover, a voltage of say 500-1000 volts is available, special means for causing the apparatus to work with small maximum condenser charges, may be dispensed'with.

As to the glow discharge device I 0, it is preferably represented by a gas filled grid controlled thermionic valve. The maximum condenser voltage admitted by this glow lamp then regulates itself in a simple way by the grid bias of the glow lamp. This negative bias. may be taken from two electrodes terminating apart of the total discharge space of the stabilizer 3, as this bias is an essential factor in determining the fre-- quency of the periodic discharges, and consequently should be very constant, too. The said bias may be obtained by connecting the cathode of the glow tube Hi to an intermediate electrode of the stabilizer 3, and by connecting the cathode of the stabilizer 3 through a high value grid leak resistance 22 to the grid of the glow tube Ill. The synchronizing signals are fed in by the terminal l9 and are applied to the grid of the glow tube "I through a blocking condenser 20 and a series resistance 2|, having preferably about the same value as the grid leak resistance 22.

' The oscillating voltages of the condenser 3 are coupled by means of a; condenser l4 and a potentiometer l3 having a very high resistance so as to reduce the load to the condenser .8 to am amplifier valve 23. acting at the. same time as a voltage amplifier and as a power amplifier. The

combination of the coupling condenser [4, the

resistance 13 and the natural capacities of the amplifier grid circuit should be, in a manner well known in the art, so adjusted as to obtain frequency independency, so that amplification takes -place without distortion of the wave form of the terminals P1 and P2, from exerting a detrimental retroaction on the deflecting voltages. The combination of both of the mentioned functions of the valve 23 is satisfactorily succeeded in by the use of a pentode. The control grid bias of the valve 23 may be taken from a potentiometer I5, which may be connected across a partial discharge space of the stabilizer 3. The bias of the screen grid of the valve 23, applied to said grid through a series resistor l1 shunted by a by-pass condenser I8, is so chosen as to allow adjustment of the correct working point on the control-grid voltage-plate current characteristic, though the control grid bev biased relatively far into the negative. The resulting amplitude, and consequently the size of the line screen produced by the cathode ray deflection is adjusted by means of a variable tap on the potentiometer l3. The position of the whole line screen may be varied by adjusting a tap on the grid bias potentiometer I5, whereby the internal resistance of the valve 23 is varied asdesired and consequently the equilibrium of the bridge formed by the valve 23 and its anode resistance on the one hand, two parts of the total discharge space of the stabilizer '3 on the other hand.

For producing those voltages necessary for deflecting the cathode ray in a direction vertical to the deflection caused bythe voltages produced in the shown device, a second circuit is employed, which resembles that shown but for the dimensioning of its elements (the ratio between the frequencies of the voltages to be generated in the two circuits in question being equal to the num ber of lines the line screen is to be composed of-for instance equal to 60 or 90 or 120), and which is preferably fed from the same stabilizer 3 through connections as indicated by arrows on the top of the drawing. As to the dimensioning of the circuit elements, an essential requirement is that the time constants of the charging circuits are from ten to one hundred times greater than the periods of the oscillations to be generated in the respective circuits. I

The essential elements of the frame frequency deflecting circuit may, for example, be chosen as follows:

Resistance 1 about 50,000 ohms.

Condenser 9 from '7 to 10 mf. (the corresponding condenser in the line frequency deflecting circuit being in the order of 0,1 mf.)

Resistance l6 about 20,000 ohms.

Resistances 22, 2| in the order of 1 -3 megohms.

Potentiometer l3 preferably not below 1 megohm.

Because of the high value of I3 the grid lead connection of the valve 23 should be as short as possible and carefully screened off against any capacitative disturbances. The valve 23 may be so chosen as to enable an amplification in the order of 10-15 times to be obtained.

The heating of the cathodes throughout the apparatus may, without any difllculties, be supplied from the A. C. mains.

I claini; An arrangement for producing oscillations of saw tooth wave form, comprising a direct current source. having fluctuations in potential, a

glow discharge device, electrodes in said glow dischargedevice, means to cause said glow discharge device to be energized from said direct current source-means to take from said electrodes potentials steadied as compared with the potential ofsaid direct. current source by the working of said glow discharge device, an adjustable condenser and a resistance connected in series, means for applying a voltage taken from a pair of said electrodes to said series connection .to charge said condenser, means for periodically discharging said condenser. said discharging means including a second glow discharge device connected across said condenser, said discharging means being so dimensioned in relation to the dimensioning of said condenser and of said series connection and-in relation to the voltage available between said pair of electrodes as to allow said condenser to be charged to at most one tenth of said voltage only before the discharge 5

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