US2981865A - Transistorized oscillatory system - Google Patents

Description

April 2 1961 E. A. FERNBACH 2,981,865

TRANSISTORIZED OSCILLATORY SYSTEM Filed June 8, 1959 2 Sheets-Sheet 1 iia- INVENTOR. fizz/1'77 A, WerWZJa Z,

United States Patent 2,981,865 TRANSISTORIZED OSCILLATORY SYSTEM Filed June 8, 1959, Ser. No. 818,637 18 Claims. (Cl. 315-206 This invention relates to transiston'zed oscillatory systems and more particularly to transistor blocking oscillators suitable for producing high voltages, and to voltage supply and automotive ignition systems embodying transistor blocking oscillators.

An object of this invention is to improve automatic ignition systems.

Another object of this invention is' to increase the transfer of energy from a transistor blocking oscillator circuit to an output device.

Another object of this invention is to increase the output of a transistor blocking oscillator without overheating the transistor.

Another object of this invention is to establish im-' proved electrostatic shielding between a collector transformer winding in a transistor blocking oscillator and the high voltage transformer winding.

A feature of this invention is an improved automotive ignition system in which a plurality of abrupt high amplitude voltage spikes are appliedto each spark plug at each ignition thereof through the use of a transistor blocking oscillator circuit.

Another feature of this invention is a transistor blocking oscillator circuit in which the collector is coupled both to the base and to the emitter. 7

Another feature of this invention is the provision of a transformer winding for the emitter of a vtransistor in a blocking oscillator circuit both to couple the emitter to the collector and to electrostatically shield the collector winding from the output high voltage winding of the transformer.

Another feature of this invention is the provision of a creasing the base drive in a transistor blocking oscillator and for fusing the base circuit of the transistor.

Another feature of this invention'is an improved igni-' tion system. including a transistor blocking oscillator and a pulse generator.

The manner of accomplishing the foregoing objects and the detailed nature of the foregoing features, and other objects and features of the invention, will become apparent from the following detailed description of embodiments of the invention when read with reference to the accompanying drawings in which:

' Fig. l is a schematic representation of an ignition system embodying certain of the principles of the present invention;

. Fig. 2 is a schematic representation of modification of the ignition system of Fig. 1;

Fig. 3 is a schematic representation of a blocking oscillator type of high voltage supply;

Fig. 4 is a fragmentary schematic representation of a modification of the circuitry of Fig. 3;

Fig. 5 is a schematic representation of a pulse generating system suitable for use as a part of an ignition system; 1

Fig. 6 is a diagram of certain time-versus-voltage relations existing, for example, in the circuits of Figs. 1, and 2; and

ice

Fig. 7 is a schematic representation of a system for producing a high direct voltage and embodying certain principles of the invention. 7

The ignition system of Fig. 2 is intended to supply timed bursts of energy to each of a plurality of spark plugs, such as spark plug 10, in a predetermined sequence, the sequential distribution to the spark plugs being accomplished by means of a distributor 12, and the timing being accomplished by means of an interrupter 14, distributor 12 and interrupter 14 being operated in synchronized relationship as by being mechanically driven by common rotating means synchronized with the engine. In practice, for example, the distributor 12 and the interrupter 14 may take the form of the conventional distributor and contacts in modern automobiles modified only in the removal of the capacitor which normally shunts the each successive spark plug is fired. Each such closure of the contacts results in a burst of high voltage pulses being applied through the distributor to the appropriate one of the spark plugs. The contacts of interrupter 14 then open and the distributor advances to establish a' connection to the next succeeding spark plug in the sequence, whereupon, at the appropriate time, the contacts of in-. terrupter 14 again close to apply a burst of pulses to that spark plug, and so on through the sequence.

The closure of the contacts of interrupter 14 initiates the operation of a type of blocking oscillator circuit including a transistor 16 (herein assumed to be a p.n.p. transistor) and a transformer 18 having a plurality of magnetically linked windings 20, 22, 24, 26, 23 and 30. The system is energized from a source of directvoltage 32 which may, for example, be a twelve-volt automobile battery.

The base of the transistor 16 is connected through winding 20, resistor 34, variable resistor 36, and interrupter 14 to the negative terminal of source 32, and the base is also connected to one terminal of capacitor 38 to the positive terminal of source 32. The collector of transistor 16 is connectedthrough Winding 16 and variable resistor 40 to the negative terminal of source 32. The emitter of transistor 16 is connected'through winding 24 and variable resistor 42 to the positive terminal of source 32. A capacitor .44 is connected fromthe junction of winding 22 and resistor 40 to the emitter of transistor such as spark plug 10 and the other terminal, which is grounded.

When the contacts of interrupter 14 close, transistor 14 becomes conductive, the emitter current flowingthrough winding 24, the collector current flowing through Winding 22, and the base current flowing through winding 20. The primary blocking oscillator coupling is between the collector and the base circuits (with a common emitter) by means of transformer windings 22 and 20. The collector current in winding 22 induces a cur- 5 rent in and a voltage across winding 20 which is in a direction (negative in the assumed case) to increase the base drive and to increase the flow of collector current.- The increased collector current through winding 22 fur ther increases the base drive, and this regenerative action continues until saturation is reached and no more collecmenses t. tor current increase occurs. When this condition is reached, the collector current begins to diminish, which reduces the base drive to further reduce the collector current, and so forth in a regenerative sense until the transistor is at cut'off, that is, the collector current is substan tially zero. Thereafter, the cycle of increasing and decreasing conduction is repeated.

The rate of reduction of collector current is high and,

the resultant rapid collapse of flux in the collector winding 22 induces a high voltage in secondaries 23 and 30, which is applied to the spark plugs.

A representation of an oscillograph of the output voltage of the system is illustrated in Fig. 6 of the drawings. The initial pulse is of relatively long duration and of negative polarity, but thereafter a plurality of high-frequency, high amplitude voltage spikes are applied across the spark gap to produce ignition of the combustible mixture in the cylinder.

The frequency of the spikes is determined primarily by the characteristics of the transformer 18 and preferably a high quality grain-oriented, high permeability core should be employed. Desirably, the frequency is in the order of six kilocycles per second to forty kilocycles per second, allowing in the order of eight to thirty-two firing pulses per spark plug per sequence instead of the conventional single pulse.

The number of pulses per burst may be determined solely by the period of closure of the contacts of interrupter 14 if desired, or the termination of the oscillation may be achieved by selecting the system parameters to produce self blocking after a preselected number of cycles. However, in view of the magnitude of the energy requirements of the spark plugs, either a relatively expensive power transistor must be employed or the time duration of operation of the transistor for each pulse burst must be limited. If the interrupter contacts control the duration of oscillation, the oscillatory period at low engine speeds is relatively long so that the outputof the system must be reduced to prevent overheating or destruction of the transistor, and this adversely affects the operation of the system at high engine speeds when the duration of the pulse bursts is short and when losses in the transfer of energy tend to be more serious. Accordingly, it is preferred that the closure time of the interrupter contacts control the duration of the pulse burst at high engine speeds and that the self blocking of the circuit terminate the oscillatory action at low engine speeds. This arrangement has the further advantage that the transistor will not oscillate for a destructive period if, while the interrupter contacts are closed, the automobiles ignition switch is turned on but the engine is not started.

The circuit of Fig. 1 also includes means for permitting the transfer of adequate energy to the output without excessive heating of the transistor, that is, meansfor increasing the current in secondaries 28 and 30 without increasing the base current to the point of destruction of the transistor, and, in fact, without any increase in the base current. This means includes emitter Winding 24. Winding 24 is wound and connected so that the emitter current, at any instant, will result in the induction of a voltage across those windings 28 and 30 in a direction to aid or increase the voltage developed across those windings as a result of the flow collector current through winding 22 at that instant. In a practical embodiment of the unit the addition of winding 24 resulted in a doubling of the current and doubling of the output high voltage without changing the base current. In this way, a transistor designed to provide, for example, thirty-five times current amplification will handle currents as much as seventy times the base current without effectively increasing the function temperature. In a practical embodiment, at base currents of 30 milliamperes, thecollector and emitter currents were 1.5 amperes and 1.53 amperes, respectively, while at a base current of 100 milliamperes, those values were 2.00 amperes and 2.20 amperes, respectively. It will be noted that if, in lieu of providing emitter winding 24, an effort is made to increase the output voltage by increasing the turns of winding 22, the effective inductance of winding 22 will increase to the point where operation of the equipment is adversely affected since it affects the impedance of the collector circuit and the collector to base coupling.

The provision of winding 24 has another significant advantage. By physically disposing winding 24 between winding 22 and winding 28-30, winding 24 serves as an electrostatic shield between the high voltage windings and the collector winding to avoid electrostatic interaction which would be harmful to the collector.

The provision of an emitter winding is, of course, not imperative to the practise of all of the principles of the invention, and Fig. 3 illustrates a blocking oscillator circuit with transformer-coupled collector and base and common emitter which does not utilize an emitter winding. In that circuit, the collector of transistor 50 is con, nected to the negative terminal of source 52 via winding 54 of transformer 56 and resistor 58, the base is connected to that terminal via winding 60, resistor 62, variable resistor 64 and the contacts of interrupter 66, and the emitter is connected to the positive terminal of source 52 solely through resistor 68. Capacitor 70 is connected from the junction of resistor 58 and winding 54 to the positive terminal of source 52, while capacitor 72 is connected from the junction of resistor 62 and winding 69 to that positive terminal. While the output is taken across secondary winding 74 in the circuit of Fig. 3, it will be appreciated that an auto-transformer feature can be incorporated by connecting one end of the secondary winding to a tap on the collector winding, as is illustrated in the fragmentary showing of Fig. 4 in which corresponding parts have been given corresponding reference characters, with the addition of a prime.

Fig. 2 of the drawings illlustrates a modification of the Fig. l circuitry to establish a primary blocking oscillator transformer coupling between the emitter and the collector, with no such transformer coupling between the collector and the base. In that circuit, the collector of transistor is connected to the negative terminal of source 82 through winding 84 of transformer 86 and through resistor 88, and the base is connected to that terminal through resistors 90 and 92 and interrupter 94. Capacitor 96 is connected between the base and the positive terminal of source 82. The emitter of transistor 89 is connected through winding 98 of transformer 86 and resistor 100 to the positive terminal of source 82, and capacitor 102 is connected from the junction of resistor 88 and winding 84 to the emitter. Pulse winding 104 may also be provided, and the output is taken across series aiding secondaries 106 and 108, that output voltage being applied through distributor 110 and across, for example. spark plug 112. i

In the circuit of Fig. 2, the current build up to saturation and reduction to effective cut-off occurs as a result of the collector-emitter transformer coupling, and that same coupling results in the production of a greater output voltage and can result in electrostatic shielding of the col- The use of a resistor of this type not only advantageously,

controls the base drive of the transistor to insure adequate drive of they base but also can be employed to fuse the; base circuit by selecting a lamp having a current carrying;

capability (to the point of rupture of the filament) less than the maximum current carrying capability of the base circuit.

It will be appreciated that the initiation of conductivity 1 of the transistor can be accomplished by means other than the conventional automotive breaker points,including means for varying the impedance of the control circuit 1 riphery. Cooperating with element 120 is an incomplete toroidal core 124, both elements 120 and 124 being formed, for example, of soft iron. The resultant magnetic circuit has a reluctance which is less when two of the protuberances on rotor 120 are aligned with the tips of core 124 than otherwise. upon core 124. One end of coil 126 is connected through winding 128 of transformer 130 to the junction between resistor 132 and transformer winding 134, the other end of resistor 132 being connected to the negative terminal of source 136, and the other end of winding 134 being connectedto the collector of transistor 138. The other end of coil 126 is connected to the base of transistor 138 through resistor 140. The center tap of coil 126 is connected to the positive terminal of source 136.

The emitter of transistor 138 is connected through Winding 142 of transformer 130 and through resistor 144 to the positive terminal of source 136. Again, the output is taken across series aiding secondaries 146 and 148, and an auxiliary pulse may be derived by winding 150 and applied between terminals 152 to initiate the performance of an auxiliary function. v g

It will be perceived that the system of Fig. 5 acts as a collector-base coupled oscillator with variable coupling. When the teeth or protuberances on rotor 120 are out of.

alignment withthe core 124, the degree of coupling is insufficient to produce regeneration When the teeth become aligned with the core, the flow of collector current in winding 134 will induce a current in winding 128 which will flow through the upper half of winding 126 in view of the series interconnection of that winding half and winding 128. The flow of current through the upper half of winding 126 will, due to the close coupling of the two halves of winding 126 with the core magnetic circuit in a low-reluctance state, induce a voltage. across the lower half ofwinding 126 of a polarity tending to drive the base negative (assuming a pup transistor), which is a regenerative coupling action. This action results in current increase to saturation, followed by current decrease to cutoff, and so on. a e

The circuit of Fig. 7 illustrates the applicability of the principles of the present invention to the derivation of a high-amplitude direct voltage for use in, for example, television receivers. In that circuit, the collector of transistor 156 is connected directly to the nega-' tive terminal of source 158 (which is here assumed to have a higher voltage than in the other described circuits, as, for example, 45 volts) through Winding 160 of transformer 162, the base of transistor 156 is connected through winding 164 of transformer 162 and through a network comprising variable resistor 1 66 and capacitor 168 to the positive terminal of source 158, and the emitter is connected through windings 170 and 172 oftransformer 162 to the positive terminal (ground) of source 158. The synchronizing pulses (sync. output) are applied through capacitor 174, one terminal of which is connected to the base of transistor 156, and the gating pulses are applied through capacitor 176, one terminal of A- center-tapped coil 126 is wound which isconnected to the junction of windings 170 and 172 of transformer 162.

The synchronizing pulses are applied through capacitor 174 to the base to initiate conductivity of the transistor. An increase in the collector circuit through winding 160 induces a voltage across winding 164 of a polarity tending to drive the base in a direction to increase the conduc-' tivity, and this regenerative action continues to saturation and thence to cut-ofi. The gating pulses output is taken across winding 172. e

The oscillatory output, as it appears across secondary winding 17 8 of transformer 162 is rectified and filtered in the normal fashion to produce an output direct voltage between conductors 180 and 182 for application, for example, to the high voltage electrodes of the kinescope.

Other utilization of the principles of this invention will be apparent to those skilled in the art. apparent that the embodiments of the invention herein disclosed are well calculated to fulfill the objects of the.

means for "applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having a primary and a secondary winding, generating means effective 'inre-' sponse to each triggering signal applied thereto to apply to said primarywinding a plurality of generally saw-tooth pulses each having a rise time which is long relative to.

the fall time thereof, signal means driven by the rotating means for applying a plurality of triggering signals to said generating means, and distributing means driven by said rotating means for connecting said secondary winding to said spark plugs in a preselected sequence.

2. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having a primary and a secondary winding, transistor blocking oscillator circuit means effective in response to each triggering signal applied thereto to apply to said primary winding a plurality of generally saw-tooth'pulses each having a rise'time which is'long relative to the fall time thereof,

signal means driven by the rotating means for applying a plurality of triggering signals to said generating means, and distributing means driven by said rotating means for plugs, means for applying a burst'of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising transistor blocking oscillator means elfective'in response to each short duration triggering signal applied thereto to oscillate for a preselected period following the termination of said signal and to produce a plurality of generally saw-tooth pulses each having a'rise time which is long relative to the fall time thereof, said transistor blocking oscillator means comprising a transformer having a secondary Winding and a first primary winding, a transistor having an emitter, a collector and a base, means connecting said collector in series with said first primary winding, means including said first primary winding and an additional winding on said transformer connected in series with said base and magnetically coupled to said first primary winding for coupling said collectorto said base to provide blocking oscillator action, and means for increasing the current in said secondary. winding without substantially increasing the base cur- While it will be or fairmeaning of the sub-' rent comprising a second primary winding for said transformer connected in series with said emitter, signal means driven by the rotating means for applying a plurality of short duration triggering signals to said transistor blocking oscillator means, and distributing means driven by said rotating means for connecting said secondary winding to said spark plugs in a preselected sequence, said signal means applying a triggering signal to said transistor blocking oscillator means each time that said secondary winding is connected to a spark plug.

4. The combination of claim 2 in which the duration of each burst of high frequency votlage spikes and the number of generally saw-tooth pulses which are generated in response to each triggering signal is efiectively independent of the duration of the individual triggering signals and eifectively independent of the duration of the interval between triggering.

5. The combination of claim 2 in which the duration of each burst of high frequency voltage spikes at relatively high engine speeds is controlled by said signal means and in which the duration of each burst of high frequency voltage spikes at relatively low engine speeds is contorlled by the blocking action of said blocking oscillator means.

6. The combination of claim 2 inwhich the duration of each of said bursts of high frequency voltage spikes is effectively constant over a substantail range of relatively low engine speeds and in which the duration of each of said bursts of high frequency voltage spikes varies inversely with engine speed over a range of. relatively high engine speeds.

7. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having primary, secondary and tertiary windings, transistor blocking oscillator means including a transistor and said primary and tertiary windings effective in response to each triggering signal applied thereto to apply to said primary winding a plurality of generally saw-tooth pulses each having a rise time which is long relative to the fall time thereof, signal means driven by the rotating means for applying a plurality of triggering signals to said generating means, and distributing means driven by said rotating means for connecting said secondary winding to said spark plugs in a preslected sequence.

8. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of highfrequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having primary, secondary and tertiary windings, transistor blocking oscillator means including a transistor and said primary and tertiary windings effective in response to each short duration triggering signal applied thereto to oscillate for a'preselected period following the termination of said signal and to apply to said primary winding a plurality of generally saw-tooth pulses each having a rise time which is long relative to the fall time thereof, signal means driven by the rotating means for applying a plurality of short duration triggering signals to said transistor blocking oscillator means, and distributing means driven by said rotating means for connecting said secondary winding to said spark plugs in a preselected sequence.

9. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having primary, secondary andtertiary windings, transistor blocking oscillator means including a transistor and said primary and tertiary windings effective in response to each short duration triggering signal applied thereto to oscillate for a preselected period following the termination of said signal and to apply to said primary winding a plurality of generallysaw-tooth pulses each having a rise 7 time which-is long relative to the fall time thereof, signal means driven by the rotating means for applying a plurality of short duration triggering signals to said transistor blocking oscillator means, and distributingrneans driven by said rotating means for connecting said secondary winding to said spark plugs in a preselected sequence, said signal means applying a triggering signal to said transistor blocking oscillator means each time that said secondary winding is connected to a spark plug.

10. The combination of claim 9 in which said primary Winding is connected in series with said collector and said tertiary winding is connected in series with said base so that said collector is transformer-coupled to said base.

11. The combination of claim 10 further including an additional winding on said transformer connected in series with said emitter.

12. The combination of claim 10 further including additional winding means on said transformer connected in series with said emitter and physically disposed between said primary and said secondary windings for electrostatically shielding said primary winding from said secondary winding.

13. The combination of claim 9 in which said primary winding is connected in series with said collector and said tertiary winding is connected in series with said emitter so that said collector is transformer-coupled to said, emitter. v

14. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having a first and a second primary winding and a secondary winding, transistor blocking oscillator circuit means effective in response to each short duration triggering signal applied thereto to oscillate for a preselected period following the termination of said signal and to apply to said primary winding a plurality of generally. saw-tooth pulses each having a rise time which is long relative to the fall time thereof, signal means driven by the rotating means for applying a plurality of short duration triggering signals to said transistor blocking oscillator means, and distributing means driven by said rotating means, for connecting said secondary winding to said spark plugs in a preselected sequence, said signal means applying a triggering signal to said transistor blocking oscillator means each time that said secondary winding is connected'to any spark plug, said transistor blocking oscillator means comprising a transistor having an emitter, a collector and a base, means connecting said first primary winding in series with said collector, and means connecting said second primary winding in series with said emitter.

15. The combination of claim 14 in which said second primary winding is physically disposed between said first primary winding and said secondary winding for electrostatically shielding said primary from said secondary winding.

16. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having first and second primary windings and a secondary winding, a transistor having an emitter, a collector and a base, a pulse generator comprising a tapped coil disposed upon a magnetic circuit element and means driven by said rotating means for periodically varying the reluctance of said magnetic circuit, a source of potential having first and second terminals, means connecting the tap of said coil to said second terminal, means connecting said base to one end of said coil, a resistor, means connecting said first primary winding and said resistor in series between said collector and said first terminal, means connecting said second primary winding from the junction of said first primary winding and said resistor to the other end of said coil, and means for connecting said emitter to said second terminal.

17. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising a transformer having first, second and third primary windings and a secondary winding, a transistor having an emitter, a collector and a base, a pulse generator comprising a tapped coil disposed upon a magnetic circuit element and means driven by said rotating means for periodically varying the reluctance of said magnetic circuit, a source of potential having first and second terminals, means connecting the tap of said coil to said second terminal, means connecting said base to one end of said coil) a resistor, means connecting said first primary winding and said resistor in series between said collector and said first terminal, means connecting said second primary Winding from the junction of said first primary winding and said resistor to the other end of said coil, and means including said third primary winding for connecting said emitter to said second terminal.

18. In an automotive ignition system including rotating means driven by the engine and a plurality of spark plugs, means for applying a burst of high frequency voltage spikes to each of said spark plugs in a predetermined sequence comprising transistor blocking oscillator circuit means effective in response to each triggering signal ap- 10 plied thereto to produce a plurality of generally sawtooth pulses each having a rise time which is long relative to the fall time thereof and comprising a transformer having a secondary winding and a first primary Winding, a transistor having an emitter, a collector, and a base, means connecting said collector in series with said first primary winding, means including said first primary winding for coupling said collector to said base to provide blocking oscillator action, and means for increasing the current in saidsecondary Winding without substantially increasing the base current comprising a second 'primary Winding for said transformer connected in References Cited in the file of this patent UNITED STATES PATENTS 1,589,489 Snook June 22, 1926 1,968,930 Cotter et al. Aug. 7, 1934 2,347,286 Sandretto Apr. 25, 1944 2,475,995 Short July 12, 1949 2,780,767 ,Janssen Feb. 5, 1957 2,816,230 Lindsay Dec. 10, 1957 2,849,615 Gustafson Aug. 26, 1958 2,878,298 Giacoletto Mar. 17, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,981,;865 April 25, 1961 I Erwin A. Fernbach It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patentv should read as corrected below.

Column l line 20, for "automatic" read automotive line 45 for "the provision of a" read a means for in' --g Column 3 line 63, after "flow" insert of Column 7 line 23 for"contorlled" read controlled line 27 for "substantail" read --substantial line 47, for "preslected" read preselected Signed and sealed this 14th day of November 19 1.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC

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