US3195009A - Time-base circuit for cathode-ray tube - Google Patents

Time-base circuit for cathode-ray tube Download PDF

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US3195009A
US3195009A US209982A US20998262A US3195009A US 3195009 A US3195009 A US 3195009A US 209982 A US209982 A US 209982A US 20998262 A US20998262 A US 20998262A US 3195009 A US3195009 A US 3195009A
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winding
current
capacitor
transformer
diode
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US209982A
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English (en)
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Poorter Teunis
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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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
    • H03K4/83—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements semiconductor devices with more than two PN junctions or with more than three electrodes or more than one electrode connected to the same conductivity region
    • H03K4/84—Generators in which the semiconductor device is conducting during the fly-back part of the cycle

Definitions

  • This invention relates to time-base circuit arrangements of the kind employing a semi-conductor switching device wherein a sawtooth current is generated in a cathode-ray tube deflection coil during the non-conductive state of said switching device and wherein energy isfed back to the supply source during the said non-conductive state.
  • Such so-c-alled flyback-driven circuit arrangements produce a sawtooth currentth-rough a coil and comprise a DC. voltage source, a supply impedance, a capacitor, a transformer to which the deflection coil is coupled, a switching device and a recovery diode.
  • a charging current supplied from the DC. voltage source via the supply impedance to the capacitor, accumulates electrical energy in the capacitor.
  • the switching device is rendered conductive by means of a control signal during the flyback period of the sawtooth current, as a result of which the electrical energy accumulated in the capacitor is converted, in the form of a current through the switching device, into magnetic energy accumulated in the field of the transformer and the coil coupled to it.
  • the diode coupled to the transformer is automatically rendered conductive during the stroke period of the sawtooth current and means are present to cut off the switching device as a result of which the magnetic energy accumulated in the field can flow back to the DC. voltage source in the form of a current through the recovery diode.
  • the known circuit arrangement has the drawback that the core material of the transformer is subject to considerable premagnetisation. This is due to the fact that the energy derived from the D.C. voltage source is first accumulated in the capacitor, then flows during the flyback, into the field of the transformer and the coil coupled to it, and, during the stroke, flows back into the source of direct voltage via the diode, so that the supply of energy occurs via a first path and the recovery via a second path. Since in the known circuit the return of the energy accumulated in the field of the transformer takes place exclusively via the diode connected to the said transformer, it will be clear that the current which is produced by this recovery of energy only flows in one direction and will therefore contain a considerable D.C. component, as a result of which the core material of the transformer will be premagnetized.
  • the coil through which the saw-tooth current produced is flowing is the horizontal deflection coil in a television receiver
  • it is normal to step up the pokes produced across the transformer winding during the 3,195,0fi9 Patented July 13, 1965 fiyback period of the sawtooth current and to rectify and use them for supplying EHT to the final anode of the picture tube and/or for supplying the focusing voltage for said tube.
  • this requires increased energy, resulting in a further increase in the size of the transformer because in the known circuit the current through the transformer which flows back to the DC. voltage source through the diode is responsible for the energy recovery. If the recovered energy becomes less (greater beam cur rent in the picture tube) the current through the transformer winding and through the diode will be less.
  • the object of the invention is to provide a flybackdriven circuit arrangemet of the kind referred to hereinbefore in which no premagnetization of the core material occurs or if such a premagnetisation is permitted so that the arrangement delivers additional energy to a varying additional load the premagnetisation is counteracted by this additional energy.
  • the flyback-driven circuit arrangement according to the invention is characterised in that at least three windings are provided on the transformer core.
  • the first winding having a number of turns n is traversed by the current which supplies electrical energy to the capacitor and is traversed in the opposite sense by the current which recovers the magnetic energy accumulated in the field to the DC. voltage source.
  • the second winding having a number of turns n is exclusively traversed by the charge current of the capacitor
  • the third winding having a number of turns n is traversed by the discharge current of the capacitor or by the discharge current of the capacitor plus the current which returns the magnetic energy to the DC. voltage source.
  • FIG. 1 shows a somewhat modified form of the known circuit employing a silicon rectifier as the possible switch ing device.
  • the said rectifier will be hereinafter referred to as an S.C.R.
  • FIG. la is the symbol for a n-p-n-p S.C.R. and FIG. 1b shows the symbol for a p-n-p-n S.C.R.
  • FIG. 2 is a first embodiment of a circuit according to the invention
  • FIGS. 3, 4, 5 and '6 are the stages to come from the known circuit arrangement according to the invention.
  • FIG. 7 shows the magnetic flux density magnetic field strength (B-i-D- characteristic to indicate the variation of the premagnetization of the circuit arrangement as shown in FIG. 2 is also used for producing the E.H.T. for a picture tube in a television receiver,
  • FIG. 8 is a similar embodiment as shown in FIG. 2 but includes a recovery capacitor as the auxiliary D.C. voltage source,
  • FIG. 9 shows a second embodiment of a circuit arrangement according to the invention.
  • FIG. 10 is a modified embodiment of the invention with respect to FIG. 9.
  • FIG. 1 shows a somewhat modified circuit as that known from the US. Patent 2,995,679.
  • the circuit is provided with an auto-transformer and with an overswing coil L so as to cut oh the SCR marked T, used in this circuit as the switching device, after termination of the flyback.
  • the purpose of the overswing coil L which may also be used if alternatively a transistor is employed as the switching device, which purpose is of no significance for the present invention. Therefore, the object of the coil L will not be further described.
  • the S.C.R. marked T shown in FIG. 1 is of the n-p-n-p type the emitter e of which consists of n-material, the base b of p-material and the collector 0 also of p-rnaterial, while a layer consisting of n-material is provided between the base and the collector.
  • the current in such a S.C.R. is directed from the collector c to the emitter e. Its symbol is shown in FIG. 1a.
  • a p-n-p-n S.C.R. may be used.
  • the current flows from the emitter e to the collector c.
  • the symbol for this latter S.C.R. is shown in FIG. 1b. It will be clear that if a p-n-p-n S.C.R. is used instead of a n-p-n-p S.C.R. the polarity of the source of supply voltage and of the diode D must be reversed.
  • L is the supply coil, 1 a DC. voltage source capable of supplying a direct voltage of V volts, 2 an autotransformer to the tapping 3 of which one terminal of a capacitor C is connected, the other terminal being connected to the junction point of the supply coil L and the overswing coil L
  • the defiection coil L is connected to the secondary 4 of the transformer 2.
  • the sawtooth current to be produced flows through the coil L and this coil may consequently be provided around the neck of a television picture tube, if the circuit is used in a television receiver, or around the neck of a camera tube, if the circuit is used in a television camera.
  • the coil L in this case serves as a deflection coil for the horizontal deflection of the electron beam of the tube.
  • the transformer winding 8 must be divided into at least three windings which have to be traversed by the various currents in a particular manner. This is shown in FIG. 2, in which the winding 8 is divided into windings 8 and 8" which are magnetically coupled together and to the winding 4. The winding 8 is again divided into two windings 11 and n so that a total of three windings are present, namely the windings n n and 8".
  • FIG. 3 In order to explain the operation of the circuit shown in FIG. 2, reference is made to FIG. 3 in which the known circuit of FIG. 1 is shown in a somewhat modified manner and in which the S.C.R. marked T and the diode D are represented as switches T and D, while the source 1 is omitted and the equivalent direct voltage of V, volts produced by this source is shown instead.
  • the capacitor C is charged during the stroke period of the sawtooth current 3 by a current i which during the stroke period which the switch T is opened is equal to the current i supplied via the supply coil L
  • the switch T is closed and the direction of i is reversed so that the capacitor C discharges and its electrical energy is accumulated as magnetic energy in the field of the transformer 2 and the deflection coil L coupled thereto.
  • the switch D is opened so that the current i flows as a current i through the overswing coil L and the switch T to the part of the winding 8 between the tapping 3 and earth.
  • FIG. 4 A first stage in the process of arriving at the circuit arrangement of the invention is shown in FIG. 4.
  • the winding 8 of the transformer 2 is divided into two windings 8' and 8" which are magnetically coupled together. Between these two windings the switch D is provided, while the terminal of the capacitor C connected to the transformer 2 is connected to the junction point of switch D with winding 8".
  • the operation of the circuit as shown in FIG. 4 is the same as that shown in FIG. 3, but this first stage is necessary in order to understand the second stage shown in FIG. 5, in which the end A of the supply coil L is shifted from the positive supply terminal to the junction point of the switch D with winding 8".
  • the premagnetisation has already considerably been improved.
  • the paths for the energy supplied and returned are partially combined in the winding 8', so that the current I namely the mean current through the winding 8, equals zero if no losses occur in the circuit.
  • the circuit as shown in FIG. 2 which with the exception of the part for producing the high voltage V is identical to that shown in FIG. 6, is a deflection circuit in a television receiver for the horizontal deflection of the electron beam in the picture tube
  • the EHT supply V for the picture tube is to be derived from the circuit shown in FIG. 2; an additional winding 10 should be provided on the transformer 2 to which a rectifier 11 is connected which rectifies the pulses which are produced during the fiyback period AT and are stepped up by the winding 10, so that an EHT V is obtained which is supplied to the final anode of the picture tube.
  • the adjustment may be chosen so that holds, likewise with n n if no high voltage load is present, that is to say with beam current zero.
  • the adjustment of the transformer 2 will change into in the case of a beam current greater than the average current, so that the core material is premagnetised to the other side of the (3-H) characteristic.
  • FIG. 8 Another embodiment of the circuit arrangement shown in FIG. 2 is shown in FIG. 8.
  • This circuit operates in exactly the same manner as that shown in FIG. 2.
  • a recovery capacitor 1" is provided across which a voltage V is developed so that the total supply voltage for the circuit is equal to V +V where V is the voltage supplied by the actual DC. voltage source 1'.
  • the capacitor 1" which has such a large capacitance value that the voltage V developed across it does substantially not vary as a result of the charge and dis charge currents flowing through it, takes the place of the source 1 of FIG. 2 and the source 1' serves exclusively for compensation of the losses occuring in the circuit. This is easy to see. For, if no-losses occur, the source 1 may be omitted and the junction point of the capacitor 1" with the winding 8" must be connected to earth. Then, again the circuit shown in FIG. 6 is obtained, in which the DC. voltage source 1 is replaced by a recovery capacitor 1" to be considered as an auxiliary D.C. voltage source. In this latter case, the number of turns n 11 and 11 of the arrangement shown in FIG. 8 are equal to those shown in FIGS. 2 and 6. If losses do occur, the source 1 is strictly necessary and also the number of turns n 11 and 11 will differ from those of FIGS. 2 and 6.
  • FIG. 9 shows another embodiment of a circuit according to the invention.
  • the winding 13 is the first winding which is traversed by the current which supplies the electrical energy to the capacitor C and is traversed in opposite sense by the current which returns the magnetic energy accumulated in the field of the transformer 2 and the coil L via the diode D into the source 1.
  • the current i' flowing through the winding 13 with number of turns n' consequently has a mean valve 5 which will be zero if no losses occur and will have a value deviating from zero in the event of losses.
  • the winding 14 is coupled magnetically to the winding 13 so that it may be assumed that these windings belong to the transformer 2.
  • the Winding 14 is again divided into two windings with number of turns n' and It'
  • transformer 2 in FIG. 9 again comprises three windings, in which the winding 13 is the first winding, the winding with number of turns n' is the second winding and the winding with number of turns n';, is the third winding.
  • the second winding is traversed by the charge current i' for the capacitor C and the third winding by the disformer 2 with number of turns n' and the winding 14" is the third winding with number of turns n
  • the current i' in FIGS. 9 and 10 will deviate from current i in FIGS.
  • the high Voltage V for the picture tube can, in a simple manner, be produced by providing an extended winding to which the rectifier 11 is connected.
  • the number of ampere turns of the transformer 2 may be chosen according to the equation T It' +T' n' -T' n O likewise with n' n' in a manner such, that for the average beam current through the picture tube the adjustment according to Equation 40 changes over into that according to the Equation 4 in a corresponding manner as described for the circuit shown in FIG. 2.
  • the transformer used comprises at least three windings which are wound on the core in the same sense.
  • the three winding feature is quite apart from other windings, such as for example, the windings 4, 10 and 1t) which are provided on the transformer 2 for coupling purposes.
  • the transformer 2 is first of all required to establish an exact equilibrium condition between charge and discharge time of the capacitor C in connection with the ratio between stroke and flyback period. This is eifected by the transformer ratio n /(n -i-n for FIGS. 2 and 8 and n' /n' for the circuit of FIGS. 9 and 10 respectively. Owing to the presence of three windings the choice of the number of turns 11 and n respectively is free so as to satisfy at will the Equations 3, 3a, 4 or 4a.
  • the first winding with the number of turns n n respectively need not always be one winding. It may be divided into two windings with the same number of turns and the same winding sense, in which the current which charges the capacitor C flows through one winding and the current returned via the diode D flows through the other of those divided windings.
  • the supply coil L an inductance value which is as large as possible. In that case a substantially constant charge current i or 1" respectively is obtained, which, in connection with the energy passed round is the most favourable situation since in this case the fewest losses occur.
  • a deflection circuit for producing a sawtooth current in a deflection coil, said sawtooth current having a stroke period and a fiyback period comprising a source of direct voltage, a transformer having a core and first, second and third windings wound thereon in the same sense, the number of turns of said first and third windings being determined by the ratio between the flyback period and the total period of said sawtooth current, means coupling said defiection coil to a portion of said transformer, switching means having a control terminal for controlling conduction thereof, a capacitor, an impedance element and a diode, means connecting said first and second windings, said impedance element and said capacitor to said voltage source thereby establishing a charge current path from said source to said capacitor by means of said first and second windings, means for coupling a control signal to said control terminal of said switching means to render said switching means conductive during said fiyback period, means connecting said switching means in circuit with said capacitor and said third winding so as to provide a discharge path for said capacitor
  • said deflection coil is adapted for use with a television picture tube for deflecting the electron beam, and further comprising a rectifier coupled to said transformer for deriving the high direct voltage for said picture tube whereby energy losses in said circuit increase with an increasing beam current, said first, second and third windings being arranged such that the sum of the ampere turns produced by the mean current 1 flowing in winding one and the mean current 1 flowing in winding 2 is less than the ampere turns produced by the mean current 1 flowing in Winding 3 at low values of electron beam current and wherein said mean current I in winding one is equal to the difference in the mean currents l and i flowing in windings 2 and 3, respectively, and wherein the number of turns of Winding 3 is greater than the number of turns of winding 2.
  • Apparatus as described in claim 3 wherein the number of turns of windings one, two and three are arranged to produce a net bias ma netization of the transformer core in a first direction at zero electron beam current and a net bias magnetization of said core in the opposite direction for the maximum value of eiectron beam current.
  • a deflection circuit for producing a sawtooth current in a deflection coil, said sawtooth current having a stroke period and a fiyback period comprising a source of direct voltage, a transformer having a magnetic core and first, second and third windings wound thereon in the same sense, means coupling said deflection coil to a portion of said transformer, a diode, means connecting said first winding, said diode and said third winding in series, in the order named, across said voltage source, an impedance element and a capacitor, means connecting said second winding, said impedance element and said capacitor in series circuit in the order named, said connecting means further comprising means for connecting said series circuit in parallel with said diode, said first and second windings and said impedance element forming a charge current path for said capacitor thereby to accumulate an electric charge thereon, switching means having a control terminal for a control signal, means connecting said switching means in circuit with said capacitor and said third Winding so as to provide a discharge path for said capacitor through said switching means and
  • a deflection circuit for producing a sawtooth current in a deflection coil, said sawtooth current having a stroke period and a fiyback period comprising a source of direct voltage, a transformer having a magnetic core and first, second and third windings Wound thereon in the same sense, means coupling said deflection coil to a portion of said transformer, a diode, means connecting said first winding and said diode in series circuit across said voltage source, an impedance element and a capacitor, means connecting said impedance element, said second winding and said capacitor in series circuit, in the order named, and further connecting said series circuit in paraiiel with said diode, one terminal of said capacitor and diode forming a junction and means connecting said junction point to one terminal of said voltage source, said first and second windings and said impedance element forming a charge current path for said capacitor thereby to accumulate an electric charge thereon, switching means having a control terminal for a control signal, means connecting said switching means in a closed circuit with said capacitor

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  • Video Image Reproduction Devices For Color Tv Systems (AREA)
US209982A 1961-08-17 1962-07-16 Time-base circuit for cathode-ray tube Expired - Lifetime US3195009A (en)

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NL268352 1961-08-17

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US3195009A true US3195009A (en) 1965-07-13

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US (1) US3195009A (de)
BE (1) BE621464A (de)
CH (1) CH422869A (de)
DE (1) DE1201867B (de)
ES (1) ES280025A1 (de)
GB (1) GB957882A (de)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3365608A (en) * 1964-11-16 1968-01-23 Rca Corp Electron beam deflection circuit
US3395313A (en) * 1965-11-15 1968-07-30 Rca Corp Television deflection power recovery circuit
US3436591A (en) * 1965-08-06 1969-04-01 Rca Corp Electron beam deflection and low voltage supply circuit
US4118657A (en) * 1976-04-07 1978-10-03 Attilio Farina Circuit arrangement for providing a saw-tooth current in a coil
US4156834A (en) * 1976-02-26 1979-05-29 Indesit S.p.A. Circuit arrangement for providing a saw-tooth current in a coil

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2924745A (en) * 1956-02-15 1960-02-09 Philips Corp Line deflection circuit in television receivers

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2924745A (en) * 1956-02-15 1960-02-09 Philips Corp Line deflection circuit in television receivers

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3365608A (en) * 1964-11-16 1968-01-23 Rca Corp Electron beam deflection circuit
US3436591A (en) * 1965-08-06 1969-04-01 Rca Corp Electron beam deflection and low voltage supply circuit
US3395313A (en) * 1965-11-15 1968-07-30 Rca Corp Television deflection power recovery circuit
US4156834A (en) * 1976-02-26 1979-05-29 Indesit S.p.A. Circuit arrangement for providing a saw-tooth current in a coil
US4118657A (en) * 1976-04-07 1978-10-03 Attilio Farina Circuit arrangement for providing a saw-tooth current in a coil

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NL268352A (de)
DE1201867B (de) 1965-09-30
GB957882A (en) 1964-05-13
CH422869A (de) 1966-10-31
BE621464A (de)
ES280025A1 (es) 1962-11-01

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