US2596590A - Television time base circuit - Google Patents

Television time base circuit Download PDF

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Publication number
US2596590A
US2596590A US113118A US11311849A US2596590A US 2596590 A US2596590 A US 2596590A US 113118 A US113118 A US 113118A US 11311849 A US11311849 A US 11311849A US 2596590 A US2596590 A US 2596590A
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United States
Prior art keywords
resistance
coils
deflection
temperature
output
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Expired - Lifetime
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US113118A
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English (en)
Inventor
Overton Bryan Richard
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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Publication of US2596590A publication Critical patent/US2596590A/en
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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 arrangements for producing a sawtooth shaped current waveform in cathoderay tube deflector coils such as are employed in television transmitting and receiving equipment and, more particularly, to systems in which the deflector coils are fed through a transformer or a resistance-capacitance coupling from a thermionic valve of the triode type or other low impedance source.
  • thermionic valves having a high impedance for example, pentode output stages have been widely used. With these arrangements the output is practically independent of the load. Thus any increase in the resistance of the deflector coils due to temperature rise does not affect the amplitude of the sawtooth current waveform.
  • Such high impedance output stages either directly feed (resistancecapacitance coupling) the deflector coils or employ transformer coupling. With transformer coupling the inductance of the primary winding shunts the reflected impedance of the deflector coils and the output valve has to supply the extra current which flows in this primary winding.
  • the anode current of the output valve is then not a sawtooth waveform; the rate of change of current during the scan increases instead of remaining constant.
  • the drive for the output valve is normally obtained from a resistance, capacitance network which gives an exponential increase of potential during the scan so that the rate of change of potential decreases during this period.
  • the input potential (grid) waveform and the output (anode) current waveform are substantially identical and this presents the problem of changing the curvature of the input waveform to obtain a linear scanning current.
  • triodes has further advantages as two triode valves are frequently contained in one envelope so saving space and the cost of certain accessories such as valveholders, etc., besides cheapening the valves complement of an apparatus. All these low impedance output stages sufi'er from one serious disadvantage which arises from the fact that the output potential waveform tends to remain constant independent of the load. This is distinct from a constant output current waveform as in the case of high impedance output stages.
  • the scan amplitude is affected by temperature changes as the deflector coil resistance changes. In television equipment in enclosed cabinets the temperature rise of the coils may be as much as 30 C. and the scan reduced by 8% (leaving a 4" gap at the top and bottom of a 6" high picture).
  • valve 26 functions as a blocking oscillator with transformer 20. Incoming synchronising pulses being fed for example onto the grid.
  • the free-running frequency of the blocking oscillator is determined by the time constant of the resistor 2
  • the capacitor 6, which is discharged by the The form of the raster blocking oscillator and charges through the resistor 4 has one end connected through the R. C. coupling components I and 8 to the grid of the output valve I I and its other end to the junction of a capacitor I9 and a potentiometer I8.
  • the components IE, IS, IT, I8 and I9 form a negativefeedback network to maintain the linearity of the current waveform in the deflector coils. I l.
  • These deflector coils are connected in the anode circuit of the valve II by a transformer I3.
  • the network to affect automatic maintenance of raster height comprises the components I and 2.
  • the resistor I is of a type which exhibits a negative temperature coeficient i. e.- the resistance decreases with rise in temperature.
  • the resistor potentiometer 25 is the n o rmal "pro-set amplitude control which operates by changing the potential to which the capacitor 6 is charging.
  • the capacitor ⁇ has a largevalue (e. g, 1/,uf.) so that the point 3 -is substantially at asteadypotential while the correct input waveform appears at point 5.
  • the value of resistor I will also affect the potential ;to which the capacitor 6 is charging due to the potential drop in the resistor I.
  • the material composing. the resistor I and its spacial relationship to'hot, parts of the instrument embodying the invention are so adjusted that as the deflector coils I4 rise in temperature the resistor I drops in resistance value, increasing the input to the output valve i I and so substantially compensating for the increase in resistance of the coils and the consequent reduction in scan would otherwise occur.
  • Thearemainderof the circuit in F i g. 1 is a known arrangement for frame time base and illustrates the incorporation of; the invention in a practicaldevice.
  • A'time base circuit for a cathode ray tube comprising a magnetic deflection coil for said tubehaving a given resistance-temperature coefficient, means coupled to said coil to generate therein a deflection current having an-amplitude proportional to the voltage across-said coil and to. the resistance thereof, and a thermally responsive variable impedance element coupled to said generating means to vary the amplitude of said voltage proportional to Variations of said resistance produced by ambient temperature variations.
  • a time base circuit for a cathode ray tube comprising a magnetic deflection coil for said tubehaving a given resistance-temperature coefficient, means coupled to said coil to generate therein a deflection current having an amplitude proportional to the voltage across said coil and tothe resistance thereof, and a thermally responsive variable resistance element having a resistance-temperature coefficient opposite in sign to the resistance-temperature coefiicient of said coil and being coupled-to said generating means to vary the amplitude of said voltage proportional to variations of the resistance of said coil produced by ambient temperature variations.
  • a deflection current generator comprising a capacitive element, means including a thermally responsive impedance element to charge said capacitive element, means periodically to discharge said capacitive -element, and an electron discharge tube having an input circuit coupled to said capacitive element and having an output circuit coupled to said deflection coils, said thermaily responsive impedance element having a resistance-temperature coefiicient opposite in sign to the resistance-temperature coefficient of said deflection coils thereby to maintain the maximum amplitude of the deflection current substantially constant despite variations in resistance of said deflection coils with ambient temperature variations.
  • a deflection current generator comprising acapacitive element, means including a thermally responsive resistance element to charge said ca.- pacitive element, meansperiodically to discharge said capacitive element, an electron discharge tube. having an input circuit coupled to said capacitive element and having an output circuit coupled to said deflection coils, said thermally responsive resistance element having a resistance-temperature coefficient opposite in sign to the. resistance-temperature coeiflcient of said deflection coils thereby to maintain the maximum amplitude of the deflection current substantially constant despite variations in resistance of said deflection. coils with ambient temperature variations.
  • a deflection current generator comprising a capacitive element, means including a thermally responsive resistance element to charge said capacitive element, means including a blocking oscillator periodically to discharge said capacitive element, an electron discharge tube having an input circuit coupled to said capacitive element and having a low impedance output circuit coupled to said deflection coils, said thermally responsive resistance element having a resistance-temperature coefflcient opposite in sign to the resistance temperaturecoefiicient of said deflection coils thereby to maintain the maximum amplitude of the deflection current substantially constant despite variations. in resistance of said deflection coils with ambient temperature variations.
  • a deflection current generator comprising a capacitive element, means including a thermally responsive resistance element coupled in series with said capacitive element to charge said capacitive element, means periodically to discharge said capacitive element, an electron dis charge tube-having an input circuit coupled to said capacitive element and having an output circuit coupled to said deflection coils, said thermally responsive resistance element havinga negative resistance-temperature coeflicient thereby to maintain the maximum amplitude of the deflection current substantially constant despite variations in resistance of said deflection coils with ambient temperature variations.
  • a deflection current generator comprising a capacitive element, means including a thermally responsive resistive element to charge said capacitive element, means periodically to discharge said capacitive element, an electron discharge tube having an input circuit coupled to said capacitive element and having an output circuit coupled to said deflection coils, said thermally responsive resistive element being positioned adjacent to said deflection coils and having a negative resistance-temperature coefficient thereby to maintain the maximum amplitude of Lil the deflection current substantially constant despite variations in resistance of said deflection coils with ambient temperature variations.

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  • Details Of Television Scanning (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
US113118A 1948-09-02 1949-08-30 Television time base circuit Expired - Lifetime US2596590A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB23153/48A GB650856A (en) 1948-09-02 1948-09-02 Improvements in or relating to television time base circuits

Publications (1)

Publication Number Publication Date
US2596590A true US2596590A (en) 1952-05-13

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ID=10191020

Family Applications (1)

Application Number Title Priority Date Filing Date
US113118A Expired - Lifetime US2596590A (en) 1948-09-02 1949-08-30 Television time base circuit

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US (1) US2596590A (is")
BE (1) BE490931A (is")
DE (1) DE845213C (is")
FR (1) FR994239A (is")
GB (1) GB650856A (is")

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2743392A (en) * 1953-11-25 1956-04-24 Rca Corp Impulse excited magnetic deflection system
US2768324A (en) * 1953-09-25 1956-10-23 Joseph M Jarema Push-pull synchroscope sweep circuit
DE1052593B (de) * 1956-04-28 1959-03-12 Philips Patentverwaltung Anordnung zur Erzeugung eines saegezahnfoermigen Stromes von wenigstens nahezu konstanter Amplitude in den Ablenkspulen einer Elektronenstrahlroehre
US2879448A (en) * 1954-03-08 1959-03-24 Rca Corp Television display sweep linearization
US2939088A (en) * 1955-04-11 1960-05-31 Gen Electric Electronic relay
US3007079A (en) * 1958-01-20 1961-10-31 Sylvania Electric Prod Deflection circuitry

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1098992B (de) * 1958-06-28 1961-02-09 Standard Elektrik Lorenz Ag Schaltungsanordnung zum Ausgleich der Amplitudenschrumpfung in Fernseh-Geraeten

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2097334A (en) * 1932-05-26 1937-10-26 Emi Ltd Control circuits for cathode ray devices
US2212217A (en) * 1936-08-27 1940-08-20 Emi Ltd Oscillatory electric circuits
US2280990A (en) * 1939-05-15 1942-04-28 Emi Ltd Thermionic valve circuits for the generation of saw tooth currents

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE497817C (de) * 1929-08-17 1930-05-14 Landis & Gyr Ag Verfahren und Einrichtung zur Kompensation des durch die Stromspulenwaerme hervorgerufenen Temperaturfehlers bei Gleichstrom-Wattstundenzaehlern mit Shunt
US2213085A (en) * 1936-05-21 1940-08-27 Gen Electric Temperature-compensated electrical device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2097334A (en) * 1932-05-26 1937-10-26 Emi Ltd Control circuits for cathode ray devices
US2212217A (en) * 1936-08-27 1940-08-20 Emi Ltd Oscillatory electric circuits
US2280990A (en) * 1939-05-15 1942-04-28 Emi Ltd Thermionic valve circuits for the generation of saw tooth currents

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768324A (en) * 1953-09-25 1956-10-23 Joseph M Jarema Push-pull synchroscope sweep circuit
US2743392A (en) * 1953-11-25 1956-04-24 Rca Corp Impulse excited magnetic deflection system
US2879448A (en) * 1954-03-08 1959-03-24 Rca Corp Television display sweep linearization
US2939088A (en) * 1955-04-11 1960-05-31 Gen Electric Electronic relay
DE1052593B (de) * 1956-04-28 1959-03-12 Philips Patentverwaltung Anordnung zur Erzeugung eines saegezahnfoermigen Stromes von wenigstens nahezu konstanter Amplitude in den Ablenkspulen einer Elektronenstrahlroehre
US3007079A (en) * 1958-01-20 1961-10-31 Sylvania Electric Prod Deflection circuitry

Also Published As

Publication number Publication date
BE490931A (is")
DE845213C (de) 1952-07-28
FR994239A (fr) 1951-11-14
GB650856A (en) 1951-03-07

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