US3793555A - Flyback eht and sawtooth current generator - Google Patents

Flyback eht and sawtooth current generator Download PDF

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Publication number
US3793555A
US3793555A US00310346A US3793555DA US3793555A US 3793555 A US3793555 A US 3793555A US 00310346 A US00310346 A US 00310346A US 3793555D A US3793555D A US 3793555DA US 3793555 A US3793555 A US 3793555A
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United States
Prior art keywords
network
scan period
period
flyback
circuit
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Expired - Lifetime
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US00310346A
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English (en)
Inventor
Gils C Van
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US Philips Corp
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US Philips Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
    • H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
    • H04N3/18—Generation of supply voltages, in combination with electron beam deflecting
    • 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
    • H03K4/48—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements semiconductor devices
    • H03K4/60—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements semiconductor devices in which a sawtooth current is produced through an inductor
    • H03K4/62—Generating pulses having essentially a finite slope or stepped portions having triangular shape having sawtooth shape using as active elements semiconductor devices in which a sawtooth current is produced through an inductor using a semiconductor device operating as a switching device

Definitions

  • the generator has at least two resonant frequencies so chosen that a substantially oscillationfree scan is produced and during the scan it has at least one resonant frequency which is approximately equal to an integral multiple of the reciprocal value of the duration of the scan period.
  • the invention relates to a flyback EHT- and sawtooth current generator particularly for television display apparatus, including switching means which are periodically non-conducting during a flyback period 1' are conducting during a scan period T 1- and a network having input terminals connected to the switching means, said network comprising a transformer having at least one primary winding and possibly one or more coils connected thereto through which said sawtooth current flows during the scan period, and a secondary winding to which a rectifier circuit is connected for generating said EHT from the voltage pulses occurring during the flyback period at the secondary winding, said network, due to the leakage inductance present between the transformer windings having a first resonant frequency fa during the flyback period which frequency is substantially equal to the expression:
  • K l and S is a correction factor which is equal to the relative reduction of the slope of the sawtooth current at the end of the scan period relative to this slope at the centre of the scan period, and a second resonant frequency f which is substantially equal to the said expression for K is equal to an odd integer of more than 1.
  • An object of the invention is to provide a proportioning measure with which in spite of the said interfering influences the occurring scan oscillations can be maintained very small and to this end the flyback EHT and sawtooth current generator according to the invention gral multiple of the reciprocal value of the duration of the scan period.
  • the said network has a certain resonant frequency 7 f9 located between the two parallel resonant frequencies fa and f, at which the impedance of the network at the input terminals is at a minimum (equal to zero in cases of a network which is completely without losses).
  • This is actually the resonant frequency of the generator during the scan period, hence with conducting switching means. It is known that for an exact tuning of the flyback EHT generator to a scan which is without oscillations only the parallel resonant frequencies f and f, are important and that the series resonant frequency f is irrelevant. The location off has only influence on the shape of the flyback pulse occurring across the input terminals of the network.
  • the invention is based on the recognition of the fact that the value of the frequencyf has also a very great influence on the amplitude of the scan oscillations still remaining as a result of the said interfering influences and that this amplitude is at a minimum if the value of f is substantially equal to an integral multiple of the reciprocal value of the duration of the scan period.
  • a generator of this kind is preferably designed in such a manner that the quality of the generator during thescan period is more than 25 at the said frequency fa-
  • the Applicant's pending Patent application No. 245,144, filed Apr. 18, 1972 describes flyback EHT- and sawtoothcurrent-generators in which the flyback equal to the given expression:
  • the network has a first series resonant frequency f5, between fa and f at which the input impedance of the network is at a minimum and a second series resonant frequency f between )2 and f at which one of the frequency f and one of the frequency fg It is found that independent of each other for a minimum amplitude of the fig, component the frequency f3, is to be chosen optimum, that is to say, approximately equal to an integral multiple of the reciprocal value of the duration of the scanperio dand for a minimum amplitude of the f,;, component the frequency f must be approximately equal to an integral multia ple of the reciprocal value of the duration of the scan period.
  • the component of the lowest frequency generally has a considerably larger amplitude than the component of the higher frequency.
  • the said network has a third resonant frequency f between f and f during the flyback period which resonant frequency is at least substantially equal to the given expression for K being equal to an odd integer, a considerable reduction of the scan oscillations thus already achieved if the frequency fig between f,, and f at which the impedance of the network at the input terminals is at a minimum is substantially equal to an integral multiple of the reciprocal value of the duration of the scan period.
  • FIG. 1 shows a first embodiment of a flyback EI-IT- and sawtoothcurrent-generator for which the invention can be used.
  • FIG. 2 shows the equivalent circuit diagram of the embodiment of FIG. 1.
  • FIG. 3 shows a diagram to explain the present invention.
  • FIG. 4 shows a second embodiment of a flyback EHT- and sawtoothcurrent-generator for which the invention can be used and
  • FIG. 5 shows the equivalent circuit diagram of the embodiment of FIG. 4.
  • FIG. 1 shows a transformer 1 having a primary winding 2, one or more auxiliary windings 3 rigidly coupled to the primary winding, and a secondary winding 4.
  • a tap 6 on the primary winding A transistor 12 operating as a switch is provided between the upper end of the primary winding and ground and a capacitor 13 is connected in parallel with this transistor.
  • Said secondary winding 4 is connected to ground at one end and at the other end to a rectifier circuit consisting of a rectifier l4 and a smoothing capacitor 15; the EHT generated by the rectifier is applied to the acceleration anode of a television display tube not further shown.
  • Switching pulses which periodically cut off the transistor 12 at the end of each scan period are applied between the base and emitter of transistor 12 through a separating transformer 18, a series inductance l9 and a parallel diode 20.
  • the transistor 12 is a so-called slow switching transistor and the elements 19 and 20 are included so as to accelerate the switching off of the transistor at the end of the scan period.
  • FIG. 2 shows the simplified equivalent circuit diagram of the circuit of FIG. 1.
  • E denotes 0 the voltage source 7
  • SW denotes the switch constiis connected to the positive terminal ofa voltage supply tuted by transistor 12 and diode 20.
  • C is the capacitance of the capacitor 13 increased by the collector emitter capacitance of the transistor and the transformed parasitic capacitances of the primary winding, the auxiliary windings, the deflection coils and the linearity corrector.
  • L is the inductance of the primary winding and the deflection coils and the linearity corrector connected thereto, all transformed to the terminals to which the switch is connected.
  • L is the leakage inductance between secondary and primary windings and C is the parasitic capacitance, of the secondary winding and the input capacitance of the rectifier circuit likewise transformed to the terminals to which the switch is connected.
  • switch SW is closed.
  • the voltage E from the voltage supply source 7 is therefore present across capacitor C1 and also across inductor Ll.
  • a (sawtooth) current linearly varying with time will flow through the inductor Ll.
  • switch SW is rendered non-conducting, free oscillations will occur in the network as a result of the magnetic energy present in L1. These oscillations produce pulsatory voltages V1 and V2, the so-called flyback pulses across capacitors Cl and C2, respectively.
  • the sawtooth current in the circuit diagram of FIG. 1 flows during the first part of the scan period through the diode 20, the base-collector junction of the transistor and subsequently through the transformer and the deflection coils to the'voltage supply source and thus feeds back energy to the voltage supply source.
  • the base-emitter junction of the transistor is rendered conducting by means of the pulses applied to the base electrode of the transistor so that during the second part of the flyback period the sawtooth current now reversed in polarity can flow from the voltage supply source through the transformer and the deflection coils and subsequently through the collector electrode and the emitter electrode of the transistor to ground; then the voltage supply source supplies energy to the network.
  • the network of FIG. 2 has two resonant frequencies a 2 1r f and y 2 rr f during the flyback period namely:
  • the network is proportioned in such a manner that f satisfies equation (III) for K l and also f,, satisfied equation (III), for example, K 3 or K 5, etc.
  • the network has a third characteristic frequency f i.e. the frequency located between f and f at which the input impedance of the network is at a minimum (zero).
  • f the frequency located between f and f at which the input impedance of the network is at a minimum (zero).
  • the values off and f are laid down by the condition given in equation (III).
  • the value f may however, be freely chosen between f, and 2.
  • f is generally chosen to be sufficiently large and particularlyf is located in the region Vf f, ffl It will be evident that it is chosen to be in the region f f f f, switching means are to be used in the flyback EHT and sawtooth current generator in such a manner that they do not conduct before the termination of the previously determined flyback period 1-.
  • FIG. 3 shows the values of n associated with the various minimum values. It is found that in order to obtain both The curve of FIG. 3 is determined for a flyback EI-IT 1 and sawtooth current generator in which fa satisfies a satisfactory shape of the primary flyback pulse and a minimum amplitude of the scan oscillations, n is preferably chosen to be equal to 7 in this case.
  • the curve denoted by ER in FIG. 3 is determined for a network which in case of a closed switch has a given quantity of resistive losses in the oscillatory circuit constituted by E, SW, L2, C2 (quality factor Q is approximately equal to 20). It is found that when reducing these losses the maximum values of the ER-curve increase and the minimum values decrease.
  • a further reduction of the scan oscillations can be obtained for the above-mentioned optimum proportioning off In case of an f not proportioned in an optimum manner such a step results in an increase of the scan oscillation.
  • the quality factor Q of the scan circuit is therefore preferably chosen to be larger than 25.
  • an oscillation energy ratio (ER) of only approximately /2 percent is found for a relatively large (5 percent) deviation of the ratio f lf relative to the optimum value of this ratio.
  • This quality factor can be simply determined from the expotential decrease of the scan oscillations during the scan period.
  • FIG. 3 shows that f must deviate not more than approximately 4; 1/(T -1') from the optimum n/(T-r) so as to be located to a sufficient extent in a minimum value of the ER curve.
  • FIG. 4 shows an additional transformer winding 5 which is connected with one side to the positive terminal of the voltage supply source 7 and with the other side through a parallel LC circuit 16, 17 to the collector electrode of transistor 12.
  • the equivalent circuit diagram is shown in FIG. 5. in this diagram L3 and C3 mainly represent the inductance of coil 16 and the capacitance of capacitor 17 while L4 is the leakage inductance between the windings 4 and 5.
  • the network has two frequencies f,;, and f at which the input impedance of the network is at a minimum (zero) and the first (f of which is located between fa and f; and the second (f of which is located between fe and f7. Due to the interfering influences referred to in the preamble some oscillations will also occur during the scan period in this case.
  • These osciflatio ns will consist of a first compo- Rein of the frequency f;;, and a second component of the frequency f By choosing f within the given limits [i /s.
  • the amplitude of the said first component can be adjusted at a minimum and likewise the amplitude of the said second component can be adjusted at a minimum by choosing f within the given limits [iVsH/T- 1-)] to be equal to an integral multiple of the reciprocal value of the duration of the scan period (m/T- r with m an integer).

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Details Of Television Scanning (AREA)
US00310346A 1971-12-17 1972-11-29 Flyback eht and sawtooth current generator Expired - Lifetime US3793555A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7117322A NL7117322A (de) 1971-12-17 1971-12-17

Publications (1)

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US3793555A true US3793555A (en) 1974-02-19

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US00310346A Expired - Lifetime US3793555A (en) 1971-12-17 1972-11-29 Flyback eht and sawtooth current generator

Country Status (13)

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US (1) US3793555A (de)
JP (1) JPS5948592B2 (de)
AT (1) AT318025B (de)
AU (1) AU473373B2 (de)
BE (1) BE792866A (de)
CA (1) CA983161A (de)
DE (1) DE2258132C2 (de)
ES (1) ES409649A1 (de)
FR (1) FR2165534A5 (de)
GB (1) GB1416879A (de)
IT (1) IT998083B (de)
NL (1) NL7117322A (de)
ZA (1) ZA728234B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2547163A1 (de) * 1974-10-21 1976-04-22 Sony Corp Hochspannungsgenerator

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5435731B2 (de) * 1973-09-19 1979-11-05
DE3036573C2 (de) * 1980-09-27 1982-10-21 Norddeutsche Mende Rundfunk Kg, 2800 Bremen Schaltungsanordnung zur Erzeugung eines sägezahnförmigen Stromes

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2854592A (en) * 1953-04-27 1958-09-30 Hoffman Electronics Corp High voltage regulation circuit
US3500116A (en) * 1967-10-31 1970-03-10 Philips Corp Deflection circuit for regulating the high voltage load
US3546630A (en) * 1968-09-18 1970-12-08 Gen Electric Self-oscillating sweep circuit having a ringing circuit connected in series with a feedback winding
US3546629A (en) * 1968-09-18 1970-12-08 Gen Electric Self-oscillating sweep circuit using harmonic ringing in feedback winding

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE516320A (de) * 1951-12-19

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2854592A (en) * 1953-04-27 1958-09-30 Hoffman Electronics Corp High voltage regulation circuit
US3500116A (en) * 1967-10-31 1970-03-10 Philips Corp Deflection circuit for regulating the high voltage load
US3546630A (en) * 1968-09-18 1970-12-08 Gen Electric Self-oscillating sweep circuit having a ringing circuit connected in series with a feedback winding
US3546629A (en) * 1968-09-18 1970-12-08 Gen Electric Self-oscillating sweep circuit using harmonic ringing in feedback winding

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2547163A1 (de) * 1974-10-21 1976-04-22 Sony Corp Hochspannungsgenerator

Also Published As

Publication number Publication date
AU4994472A (en) 1974-06-13
JPS4869419A (de) 1973-09-20
BE792866A (fr) 1973-06-15
CA983161A (en) 1976-02-03
ES409649A1 (es) 1976-01-01
AT318025B (de) 1974-09-25
DE2258132A1 (de) 1973-06-20
NL7117322A (de) 1973-06-19
AU473373B2 (en) 1976-06-17
DE2258132C2 (de) 1981-12-03
JPS5948592B2 (ja) 1984-11-27
FR2165534A5 (de) 1973-08-03
ZA728234B (en) 1974-06-26
GB1416879A (en) 1975-12-10
IT998083B (it) 1976-01-20

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