US2890382A - Magnetic field generating system - Google Patents

Magnetic field generating system Download PDF

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Publication number
US2890382A
US2890382A US622478A US62247856A US2890382A US 2890382 A US2890382 A US 2890382A US 622478 A US622478 A US 622478A US 62247856 A US62247856 A US 62247856A US 2890382 A US2890382 A US 2890382A
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Prior art keywords
resistor
magnetic field
coil system
capacitor
circuit
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Expired - Lifetime
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US622478A
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English (en)
Inventor
Baldwin John Lewis Edwin
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Rank Cintel Ltd
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Rank Cintel Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K4/00—Generating pulses having essentially a finite slope or stepped portions
    • H03K4/06—Generating pulses having essentially a finite slope or stepped portions having triangular shape
    • H03K4/08—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape
    • H03K4/10—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only
    • H03K4/26—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth current is produced through an inductor
    • H03K4/39—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth current is produced through an inductor using a tube operating as an amplifier
    • H03K4/43—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements vacuum tubes only in which a sawtooth current is produced through an inductor using a tube operating as an amplifier combined with means for generating the driving pulses

Definitions

  • This invention relates to circuit arrangements for producing varying magnetic fields, such as are used for example to deflect the electron beam of a cathode ray tube, and is especially concerned to provide a circuit arrangement such that the magnetic field produced shall be accurately proportional to the integral of an applied controlling voltage.
  • a known arrangement for producing a magnetic field of which the magnitude varies as a function of an applied controlling voltage comprises an amplifier, usually a thermionic valve having as load a coil system for producing the magnetic field. Signals applied to the amplifier are integrated in the inductive load to provide the desired temporal variation of'the magnetic field.
  • Such an arrangement is satisfactory only if the resistance of the coil system is negligible compared with its inductance, but this is not usually true in practice. It therefore becomes necessary to introduce a correction for the resistance of the coil system and a wide varietyof proposals for this purpose are known.
  • the present invention seeks to provide a particularly advantageous arrangement for introducing this correction.
  • lt is another object of the invention to provide animproved scan generator apparatus suitable for employment in a television system.
  • 1 .An additional object'of the invention is to provide apparatus for generating a focus correcting field for controlling an electron beam tube.
  • Figure 1 is a block schematic diagram of one form of apparatus :for carrying out the present invention
  • Figure-2 is a circuit diagram of a preferredembodiment of apparatus according to the present invention.
  • Figure-3 comprises a series of waveform diagrams illustrativeof the operation of the circuit described in relation to Figure 2, J t 1 Figure 4 shows. an equivalent circuit of'a transformer,
  • the amplifier gain is infinite. in practice an appropriate reduction in the time-constant ice 'be either a sum or difference circuit as will be discussed below, to a voltage-controlled generator 3.
  • the output current from this generator is fed to a coil system comprising two coils 4, 5 arranged to produce a magnetic field in a desired space.
  • the voltage appearing across resistor 7 is fed back to the combining circuit 2 where it is combined with the controlling voltages receivedat terminal 1 'in such a manner as to compensate for the effective resistance of the coil system 4, 5, that is, so that the feedback voltage derived across resistor 7 will be subtracted from the voltage received at terminal 1 to provide the desired compensation.
  • the connections ofthe time-constant circuit to the amplifier must be chosen to produce a voltage of the same polarity as the controlling voltage, whereas when the two signals are added, the feedback voltage must be of opposite polarity to the controlling voltage.
  • the correctvalue for this resistor is readily determined by employing a variable resistor which is adjusted until a linear deflection of an electron beam passing through the generated magnetic field is obtained and then replacing the variable resistor by a fixed component of ohmic value equal to that thus found.
  • the controlling signal voltage applied to the amplifier means must be the time derivative of the magnetic field which it is sought to generate.
  • resistor 7 to the network of which it forms a part by way of a transmission line having a characteristic impedance of which the modulus has the same value as the ohmic value of the resistor.
  • This arrangement permits the physical separation of the resistor from the network without alteration of its value.
  • the resistor may then conveniently be placed within the combining circuit 2 and connected to coil system 4, 5, by the transmission line. When this is done it may befound advantageous to divide capacitor 6 into two portions, one on.either side .of resistor 7 so thatthe transmission line may be completely isolated from the coil system as regards direct voltages.
  • FIG. 2 illustrates a preferred embodiment of a circuit arrangement for carrying out the present invention.
  • the elements of this circuit-corresponding to those of Figure 1 are similarlynumbered.
  • the coil system 4 is fed with current from a compensated cathode follower valve 8 which has as cathode load a further valve 9.
  • the .coilsystem 4, 5 is fed from the cathode of valve 8 by way of an isolating capacitor 10.
  • Signals appearing at the anode of valve 8 byreason of a resistor 11 included in the anode circuit are fed by way of capacitor 12 to the grid of valve 9, which-is returned to the negative h.t. line through a resistor 13.
  • the appropriate bias conditions for valve '9 are ensured by a bias resistor 14 in its cathode lead.
  • the controlling voltages applied to terminal 1 are applied to the grid of valve 17 by-Way of a capacitor 20 and the grid is returned to bias source V through a resistor 21.
  • Signalsproportionalto the difference between the voltages applied to the grids of valves 16 and.17 are generated in theanode load resistor 22 of valve 16 and are applied by way of a capacitor 23 to the grid of valve 8, which is returned to a bias source W through a resistor 24.
  • Figure 3 shows at A, B and C the waveforms of the voltages arising at the grids of valves 17, 16 and 8 respectively when this circuitarrangement is used to generate a magnetic field varying cyclically in a sawtooth fashion.
  • the feedback voltage (B) developed across resistor 7 is of a form which, when subtracted from the input pulse signal (A) gives a combination of pulse and sawtooth voltage waveform (C) which when applied to the resistive inductance of the coil system, 4, 5 is integrated to generate a linearly rising current and hence a linearly increasing. magnetic field.
  • Figure 4 shows a circuit which may be considered as the equivalent circuit of a practical transformer when stray capacities are negligible.
  • the circuit components have the following values:
  • L' inductance of deflector coils'referred to transformer primary
  • R' resistance of deflector coils referred to transformer primary.
  • C3 and C4 may of course be replaced by a single capacitor of equivalent value.
  • Apparatus for producinga magnetic field of which the magnitude is proportional to'the integral ofa controlling signal voltage including means for generating said controlling signal voltage, voltage controlled amplifier means fed with said controlling signal voltage and providing current to a coil system including inductance and resistance and arranged to produce a magnetic field proportional in magnitude to the current therein; means for compensating for the effect of the resistance of said coil system comprising a circuit network including only capacitance and resistance connected effectively in shunt with said .coil system and having a time-constant at least approximately equal to that of said coil system and means for combining a voltage appearing across a resistive component of said network with said controlling signal voltage in such manner as to tend to generate across said coil system a potential having a polarity opposite to that of the potential resulting from said controlling signal voltage.
  • Apparatus for producing a magnetic field of which the magnitude is proportional to the integral of a controlling signal voltage including means for generating said controlling signal voltage, voltage controlled amplifier means fed with said controlling signal voltage and providing current to a coil system including inductance and resistance and arranged to produce a magnetic field proportional in magnitude to the current therein; including a transformer having its primary winding connected in an output circuit of said amplifier and having said coil system connected in its secondary circuit; means for compensating for the effect of the resistance of said coil system comprising a network of resistors and capacitors, said network consisting of a first combination consisting of a first capacitor in series with a first resistor, a second combination consisting of a second capacitor in shunt with a first resistor, said first and second combinations being connected in series effectively in shunt with said coil system, a third combination consisting of a third resistor in series with a third capacitor and a fourth combination consisting of a fourth capacitor in series with a fourth resistor, said third and fourth combinations being connected in series and shunted across
  • Apparatus for producing a magnetic field of which the magnitude is proportional to the integral of a controlling signal voltage including means for generating said controlling signal voltage, voltage controlled amplifier means fed with said controlling signal voltage and providing current to a coil system including inductance and resistance and arranged to produce a magnetic field proportional to the current therein including a transformer having its primary winding connected in an output circuit of said amplifier and having said coil system connected in its secondary circuit; means for compensating for the effect of the resistance of said coil system and for losses in said transformer, comprising a network of resistors and capacitors said network consisting of a first combination consisting of a first capacitor in series with a first resistor, a second combination consisting of a second capacitor in shunt with a second resistor, said first and second combinations being connected in series effectively in shunt with said coil system, a third combination consisting of a third resistor in series with a third capacitor and a fourth combination consisting of a fourth capacitor in series with a fourth resistor, said third and fourth combinations being connected in series and sh

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  • Amplifiers (AREA)
  • Details Of Television Scanning (AREA)
US622478A 1955-11-18 1956-11-15 Magnetic field generating system Expired - Lifetime US2890382A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB33056/55A GB801852A (en) 1955-11-18 1955-11-18 Improvements in or relating to circuit arrangements for producing temporally varyingmagnetic fields

Publications (1)

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US2890382A true US2890382A (en) 1959-06-09

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US622478A Expired - Lifetime US2890382A (en) 1955-11-18 1956-11-15 Magnetic field generating system

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US (1) US2890382A (de)
DE (1) DE1068398B (de)
FR (1) FR1163164A (de)
GB (1) GB801852A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3427498A (en) * 1965-10-24 1969-02-11 Motorola Inc Vertical deflection system for television
EP3168773A4 (de) * 2014-07-08 2018-05-30 Nidec Sankyo Corporation Kartenleser

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2093177A (en) * 1937-09-14 Cathode ray tube deflecting cir
US2574365A (en) * 1946-05-10 1951-11-06 Cossor Ltd A C Time base circuits
US2713651A (en) * 1951-03-23 1955-07-19 Gen Electric Amplifier circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2093177A (en) * 1937-09-14 Cathode ray tube deflecting cir
US2574365A (en) * 1946-05-10 1951-11-06 Cossor Ltd A C Time base circuits
US2713651A (en) * 1951-03-23 1955-07-19 Gen Electric Amplifier circuit

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3427498A (en) * 1965-10-24 1969-02-11 Motorola Inc Vertical deflection system for television
EP3168773A4 (de) * 2014-07-08 2018-05-30 Nidec Sankyo Corporation Kartenleser

Also Published As

Publication number Publication date
GB801852A (en) 1958-09-24
FR1163164A (fr) 1958-09-23
DE1068398B (de) 1959-11-05

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