US3758821A - Saturable-core square wave oscillator circuit - Google Patents

Saturable-core square wave oscillator circuit Download PDF

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Publication number
US3758821A
US3758821A US00190638A US3758821DA US3758821A US 3758821 A US3758821 A US 3758821A US 00190638 A US00190638 A US 00190638A US 3758821D A US3758821D A US 3758821DA US 3758821 A US3758821 A US 3758821A
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United States
Prior art keywords
saturable
transformer
load
oscillator
core
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Expired - Lifetime
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US00190638A
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English (en)
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R Canup
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Texaco Inc
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Texaco Inc
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/01—Electric spark ignition installations without subsequent energy storage, i.e. energy supplied by an electrical oscillator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
    • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
    • H03K3/45—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of non-linear magnetic or dielectric devices

Definitions

  • This invention relates to an oscillator circuit in general, and more specifically concerns an improvement for a saturable-core square wave transistor oscillator.
  • the invention also is particularly applicable to an ignition system, for use with an an internal combustion engine.
  • the invention concerns the improvement which comprises means for tuning said output transformer to resonance at'no load. And it also comprises means for determining the magnetic properties of said saturable core transformer to cause an increase in the frequency of said oscillator, as the load on said output transformer increases.
  • the entire arrangement is such that a very high starting voltage is applied to said load, and it is reduced to a relatively low voltage for maintaining the load at a relatively low power.
  • the invention concerns a saturablecore square wave oscillator circuit that comprises in combination a pair of transistor means and a saturablecore transformer. It also comprises a high turns ratio output transformer, and circuit means for connecting said transistors with said saturable core transformer and said output transformer.
  • the said circuit means includes a feedback winding on said saturable core transformer, and the said output transformer is resonant at a whole multiple of the fundamental frequency of said oscillator.
  • the said saturable-core transformer is unsaturated at increased load on said output transformer whereby said fundamental frequency increases.
  • the invention is applicable to an ignition system for use with an internal combustion cngine having breaker points associated therewith for mechanically determining the timing of initiation of an ignition spark for a cylinder of said engine.
  • the said system comprises a saturable-core square wave oscillator that employs electro-magnetic feedback coupling and provides relatively high frequency electrical energy having continuing duration during oscillation thereof. It also comprises means under control of said breaker points for saturating said feedback coupling with steady state magnetic flux to stop said oscillator and for cutting off such flux to cause rapid starting of said high frequency energy. Also, it comprises an output transformer having a high turns ratio for supplying energy to said ignition spark, and a pair of transistors plus circuit means for connecting said transistors to said electromagnetic feedback coupling and to said output transformer.
  • the invention concerns the improvement which comprises means for tuning said output transformer to resonance at no load, and means for determing the magnetic properties of said electro-magnetic feedback coupling to cause an increase in the frequency of said oscillator as the load on said output transformer increases.
  • FIG. 1 is a schematic circuit diagram illustrating a system that embodies the invention.
  • FIG. 2 is a schematic illustration indicating the type of transformer that is used in the output circuit of FIG. 1.
  • This invention may have general utility in other applications, but it is particularly applicable to an ignition system for internal combustion engines, such as the type described in US. Pat. No. 3,407,795 dated Oct. 29, 1968 wherein the applicant was a joint inventor. That patent illustrates one of a general type of ignition supply systems which provide a continuous energy supply, during the entire duration of a given spark. The spark duration is determined by the engine cam angle degrees instead of mere time.
  • this invention provides a system that can produce a high voltage output initially (under no load) so that the spark may be createdin'a positive manner. At the same time it provides an automatic reduction of the output voltage, to a much lower amplitude as the load on the system builds up clue to the spark.
  • FIG. 1 system is similar to that illustrated and described in the abovementioned Aiken et al US. Pat. No. 3,407,795.
  • the system illustrated in FIGS. 1 and 2 is one that employs a saturable' core square wave transistor oscillator 10.
  • Such oscillator includes a saturable-core transformer 11 that has a pair of windings l2 and 13 thereon. These windings supply base drive to each of a pair of transistors 16 and 17 respectively.
  • the transistors have emitters that are connected to a common circuit point 18 that is directly connected via wires 19 and 20 to ground as illustrated.
  • DC supply 23 for the. oscillator 10. This may be any feasible low voltage power supply, and is preferably a battery or other ignition system source of DC power, e.g. a 24 volt battery.
  • the negative terminal of battery 23 is connected to ground, as illustrated.
  • the positive terminal is connected when the system is energized, via a wire 24 that leads to the center tap of a primary winding 25 on an output transformer 26.
  • Part of the oscillator circuit is completed by having the ends of the winding 25 connected directly to the collector terminals of the transistors 16 and 17.
  • the collectors are connected to the ends of a feedback circuit via connections 29 and 30.
  • the feedback power is taken directly from the primary winding 25 across which is also connected a feedback winding 31 that is located on the transformer 11 and has-a resistor '33 in series therewith.
  • the oscillator arrangement is basically well known. it is the type known as a Jensen oscillator. in adapting such Jensen type oscillator toan ignition supply system, there is employed a saturation control winding 32 that is also located on the transformer 11.
  • the saturation control is the determining factor in timing, the output spark energy. This is accomplished by having a switch or breaker points 35 connected (along with a shunting capacitor 36) in series with a power source, e.g., the battery 23, to cause current flow throughthe saturation winding-32.
  • a power source e.g., the battery 23
  • Such circuit may be traced beginning at a ground connection 39 and proceeding via connection 40 to one side of the breaker points 35, and the capacitor 36 connected in parallel.
  • connection 41 It continues from the other side of the breaker points via a connection 41 to one side of a resistor 42.
  • Resistor 42 is, of course, used to determine the current flow through the circuit.
  • the circuit continues via a connection 45 to one end of the saturation winding 32.
  • the other end of winding 32 is connected via a wire or other connection 46, to one side of an ignition switch 47, and the other side of the switch is connected via a connection 48 to the positive side of the DC supply battery 23.
  • the circuit is completed, of course, by having the negative side of the battery 23'connected to ground (as indicated) by'a ground connection 51.
  • the output transformer 26 is used to step up the battery voltage of DC supply 23 to a high voltage necessary for firing the spark plugs, i.e., in the range of 20,000 to 30,000 volts. Consequently, this transformer must have a high turns ratio with a large number of secondary turns. This results in a large secondary interwinding capacitance.
  • FIG. 2 An output transformer of the type employed is schematically illustrated in FIG. 2. It is purposely constructed to have a high leakage inductance in order that such leakage inductance will limit the current which can be drawn from the transformer, since the leakage inductance is effectively in series with the load.
  • Such high leakage inductance is obtained by winding the primary, i.e., winding 25, on one leg of the transformer while the secondary winding, i.e., winding 54, is wound on another leg of the transformer core, e.g.,as illustrated in FIG. 2. Now at some frequency, the reactance of the interwinding capacitance and the leakage inductance will be equal.. This is the condition for resonance and the transformer is said to be self resonant at that frequency.
  • the unloaded output voltage will be very much larger than would be indicated from the turns ratio of the transformer.
  • the parameters of the physical structure may be predetermined.
  • the parameters relating to the physical shape of the transformer core and the placement of the windings upon it are adjusted to predetermined values and there is an air gap 55 (FIG. 2) to aid in providing leakage inductance of a preselected value.
  • the number of secondary turns of winding 54 and the manner in which they are wound determines the interwinding capacitance of the transformer 26.
  • the foregoing parameters including the interwinding capacitance and the leakage inductance are adjusted to resonate at a frequency which is twice the fundamental frequency of the Jensen type oscillator being employed. Consequently, as the transistors 16 and 17 switch at the fundamental frequency, the secondary winding 54 of the output transformer 26 will oscillate or ring at twice the fundamental frequency.
  • the peak voltage of the transformer secondary can easily be as high as twice or more than the peak voltage of the square wave output under conditions for a conventional square wave oscillator in which the fundamental oscillating frequency is far below the resonant frequency of the secondary coil.
  • the peak voltage may be 30,000 volts rather than l2,720 volts which would be obtained with a conventional system.
  • Such a peak voltage at the output of transformer 26 is quite adequate to initiate the initial breakdown of the spark plug gap.
  • Another aspect of this invention concerns the reduction of the amplitude of output voltage from transfonner 26 with accompanying reduction in the energy demand on the system. Such reduction occurs as the load on the transformer rises when the spark discharge takes place. This reduction will help avoid rapid erosion of the spark plug electrodes without reducing the voltage below that required to maintain the spark.
  • the transformer l 1 is a saturable transformer, the saturation point of which determines the operating frequency of the oscillator under no load and light load conditions.
  • the transformer By determining and/or adjusting parameters in construction of the transformer 11, it is made so that when the load on the output circuit reaches a certain level, the transformer will no longer saturate because of reduced feedback.
  • the oscillation switchings of the circuit will be precipitated by the saturation of the transistors 16 and 17 alone, and they will therefore occur at a smaller value of flux which thus increases the frequency of oscillation.
  • the higher operating frequency (which is created under the conditions described above, i.e., an increase in the load on the oscillator circuit) will cause an increase in the impedance of the output transformer 26.
  • Zener diodes 56 and 57 are provided in order to prevent transient peaks of voltage that accompany the oscillator switching, from damaging the transistors 16 and 17, there are provided a pair of Zener diodes 56 and 57. These diodes are connected across each of the transistors 16 and 17 respectively, as
  • the improvement comprising means for tuning said output transformer to resonance at no load, and
  • said saturable-core transformer having the magnetic properties thereof determined so as to cause an increase in the frequency of said oscillator as the load on said output transformer increases
  • said oscillator circuit further includes a pair of transistors connected in a Jensen type oscillator.
  • the invention according to claim 2 further including means connectedacross said transistors for shunting high voltage switching transients.
  • a saturable-core square wave oscillator circuit comprising in combination a pair of transistor means,
  • circuit means for connecting said transistors with said saturable-core transformer and said output transformer
  • circuit means including a feedback winding on said saturable-core transformer
  • said output transformer being self resonant at a whole multiple of the fundamental frequency of said oscillator
  • said saturable-core transformer being unsaturated at increased load on said output transformer whereby said fundamental frequency increases.
  • An oscillator circuit according to claim 5 further including a pair of Zener diodes connected across said transistor means for limiting switching transients.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)
  • Dc-Dc Converters (AREA)
US00190638A 1970-05-18 1971-10-19 Saturable-core square wave oscillator circuit Expired - Lifetime US3758821A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US3827970A 1970-05-18 1970-05-18
US19063871A 1971-10-19 1971-10-19
US00337509A US3847129A (en) 1970-05-18 1973-03-02 Ignition system utilizing a saturable-core square wave oscillator circuit

Publications (1)

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US3758821A true US3758821A (en) 1973-09-11

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US00190638A Expired - Lifetime US3758821A (en) 1970-05-18 1971-10-19 Saturable-core square wave oscillator circuit
US00337509A Expired - Lifetime US3847129A (en) 1970-05-18 1973-03-02 Ignition system utilizing a saturable-core square wave oscillator circuit

Family Applications After (1)

Application Number Title Priority Date Filing Date
US00337509A Expired - Lifetime US3847129A (en) 1970-05-18 1973-03-02 Ignition system utilizing a saturable-core square wave oscillator circuit

Country Status (8)

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US (2) US3758821A (de)
CA (1) CA941441A (de)
CH (1) CH541905A (de)
DE (1) DE2124183A1 (de)
FR (1) FR2090101B1 (de)
GB (1) GB1314157A (de)
NL (1) NL7106707A (de)
SE (1) SE381493B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4042855A (en) * 1975-06-12 1977-08-16 Armstrong Cork Company High frequency transistor ballast
US5179928A (en) * 1989-07-13 1993-01-19 Siemens Aktiengesellschaft Internal combustion engine ignition device
EP2141352A1 (de) * 2008-07-02 2010-01-06 Delphi Technologies, Inc. Zündsystem
ITPD20120362A1 (it) * 2012-11-30 2014-05-31 Brahma S P A Dispositivo e metodo di accensione a scarica per carburanti liquidi o gassosi

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5888468A (ja) * 1981-11-24 1983-05-26 Nissan Motor Co Ltd 内燃機関の点火装置
US5548471A (en) * 1994-07-25 1996-08-20 Webster Heating And Specialty Products, Inc. Circuit and method for spark-igniting fuel
JP2003333861A (ja) * 2002-05-10 2003-11-21 Canon Inc 電源装置およびその設計方法、並びに、発電装置
CN104393769B (zh) * 2014-11-26 2017-02-22 广州金升阳科技有限公司 一种井森电路变换器的准软开关方法与电路

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260299A (en) * 1966-07-12 Transistor ignition system
US3373370A (en) * 1965-05-20 1968-03-12 Navy Usa Transistor circuit arrangement

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3035108A (en) * 1959-04-09 1962-05-15 Economy Engine Co Oscillator circuit
US3018413A (en) * 1960-01-21 1962-01-23 Shurhit Products Inc Transistorized ignition system
US3268833A (en) * 1961-08-15 1966-08-23 Martin Marietta Corp Inverter with tuned circuit frequency control
GB1091451A (en) * 1964-04-06 1967-11-15 Charles Bowden Improvements in ignition systems for internal combustion engines
US3381172A (en) * 1965-08-23 1968-04-30 Phillip J. Weiner Solid state silicon control rectifier ignition system for internal combustion engines
US3407795A (en) * 1966-06-02 1968-10-29 Texaco Inc Ignition system for internal combustion engines
US3417313A (en) * 1966-09-21 1968-12-17 Motorola Inc Two-core solid state voltage inverter systems
US3504230A (en) * 1966-12-22 1970-03-31 Edward D Gaddes Solid-state ionizing ignition system
FR1557717A (de) * 1967-03-21 1969-02-21
US3493895A (en) * 1968-01-05 1970-02-03 Us Army Current ffedback oscillator with initial overdrive
US3706052A (en) * 1971-03-01 1972-12-12 Texaco Inc Saturable core square wave oscillator with switching transient reducing means

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260299A (en) * 1966-07-12 Transistor ignition system
US3373370A (en) * 1965-05-20 1968-03-12 Navy Usa Transistor circuit arrangement

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4042855A (en) * 1975-06-12 1977-08-16 Armstrong Cork Company High frequency transistor ballast
US5179928A (en) * 1989-07-13 1993-01-19 Siemens Aktiengesellschaft Internal combustion engine ignition device
EP2141352A1 (de) * 2008-07-02 2010-01-06 Delphi Technologies, Inc. Zündsystem
ITPD20120362A1 (it) * 2012-11-30 2014-05-31 Brahma S P A Dispositivo e metodo di accensione a scarica per carburanti liquidi o gassosi

Also Published As

Publication number Publication date
US3847129A (en) 1974-11-12
NL7106707A (de) 1971-11-22
FR2090101A1 (de) 1972-01-14
FR2090101B1 (de) 1976-07-09
SE381493B (sv) 1975-12-08
DE2124183A1 (de) 1971-12-02
GB1314157A (en) 1973-04-18
CH541905A (de) 1973-10-31
CA941441A (en) 1974-02-05

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