Breakerless Ignition System

Abstract

A breakerless ignition system for a spark ignition internal combustion engine is described. The system utilizes an alternating signal having a frequency proportional to the rate at which sparks are to be generated. The alternating signal is applied to the control electrode of a first transistor. The control electrode normally is biased to a point close to conduction. A second transistor has its control electrode connected to one side of a capacitor, the other side of which is connected to the output of the first transistor. A third transistor has its output circuit coupled to the primary of an ignition coil. Means are provided for coupling the output circuit of the second transistor to the control electrode of the third transistor. The circuitry of the third transistor operates at voltage levels determined by the source of electrical energy utilized, such as a storage battery or alternator. The first and second transistors operate at a reduced voltage level determined by a circuit comprising a resistor and a zener diode. Transient protection is provided throughout.

Description

BACKGROUND OF THE INVENTION

This invention relates to a breakerless ignition system for a spark ignition internal combustion engine.

A breakerless ignition system that could replace conventional breaker contact points and its associated condenser has been sought for many years. The ignition system conventionally used is electromechanical and employs an ignition coil for generating a high voltage capable of producing a spark across a spark gap. The primary winding of this ignition coil is connected to the vehicle battery. When current flows through the primary winding, energy is stored in the magnetic field produced by such current. The interruption of the primary winding current produces a high voltage across the secondary side of the ignition coil.

The secondary of the ignition coil is connected to one or more spark plugs. When the interruption of the primary current causes a high voltage to appear on the coil secondary, a spark occurs in the spark plug gap, thus, permitting the coil magnetic field energy to dissipate. Where multi-cylinder engines are involved, a distributor is utilized to connect the secondary of the coil to the various spark plugs for the engine cylinders at appropriate intervals of time.

In conventional electromechanical ignition systems of the type described above, a set of electrical contact points having a condenser connected in parallel with them in the engine distributor are closed, for a period of time dependent upon engine speed, to permit battery current to flow through the primary of the ignition coil. When the primary current is interrupted by the opening of the contact points, a spark occurs across the gap of a spark plug.

The electromechanical system has had a number of faults. It has been difficult to precisely control and maintain ignition timing, and the use of contact points and a condenser in the engine distributor has necessitated frequent repair or replacement of these components. One of the greatest problems associated with the conventional electromechanical ignition system has been the deterioration of engine control and performance over the useful life of the electrical contact points and condenser.

The use of solid-state components has been proposed in the past to replace the circuitry of the conventional electromechanical ignition system. Most of the proposed solid-state ignition systems have been of the capacitive discharge type in which conventional electrical contact points are used to discharge a capacitor through the ignition coil. Other solid-state ignition systems have been proposed in which the electrical contact points are eliminated and replaced by a solid-state switching device. The present invention concerns a solid-state ignition system of the latter variety.

SUMMARY OF THE INVENTION

In accordance with the present invention, a breakerless ignition system of much improved design utilizes an alternating signal obtained from a distributor to initiate or trigger a solid-state circuit which, through the application of an appropriate signal to the control electrode of a transistor, interrupts the current path in the circuit of the primary winding of an ignition coil to produce a collapse of its magnetic field, thereby, to generate a spark in the gap of a spark plug.

The breakerless ignition system of the invention includes a first transistor having an output circuit and a control electrode. The control electrode is biased to a point near that required for its conduction. The alternating signal from the distributor is also applied to this control electrode. A second transistor having an output circuit and a control electrode is also employed. This second transistor has its control electrode connected to one side of a capacitor, and the other side of the capacitor is connected to the output circuit of the first transistor. The output circuit of the second transistor is coupled through suitable circuit means to the control electrode of a third transistor. The output circuit of the third transistor is connected to and controls current in the primary winding of an ignition coil.

Electrical energy to the system is supplied by a DC source, such as a storage battery or an alternator with rectified output. The ignition coil primary winding and the output circuit of the third transistor are connected across this DC source of electrical energy.

A circuit including a resistor and a zener diode is used to reduce the level of the DC voltage applied to the circuits in which the first and second transistors are located. The operation of this first transistor and the second transistor at reduced voltage levels is especially advantageous because low battery voltages are frequently encountered in motor vehicles, particularly, prior to startup of the engine in low ambient temperature circumstances.

The invention will be better understood by reference to the detailed description which follows and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an ignition system in accordance with the inventoin; and

FIG. 2 illustrates various voltage waveforms at points in the circuitry of FIG. 1.

DETAILED DESCRIPTION

With particular reference now to FIG. 1 of the drawings, there is shown a schematic diagram of a breakerless ignition system in accordance with the invention. The breakerless ignition system is generally designated by the numeral 10.

The breakerless ignition system 10 includes a DC source of electrical energy, preferably 12 to 15 volts, such as a storage battery 12 having its negative terminal 14 connected by a common line 16 to ground at 18. The positive terminal 20 of the DC source 12 is connected by a line 22 to an ignition switch 24.

The ignition switch 24 may be of conventional design and preferably has a pole 26 to which the line 22 is connected during normal running conditions of the internal combustion engine. The ignition switch 24 also has a pole 28 used only during starting or cranking of the internal combustion engine. The pole 26 is connected to a line 30 and the pole 28 is connected to a line 32. The ignition switch 24 bridges both of the poles 26 and 28 during the engine starting mode. Thus, when the engine is running in a normal manner, electrical energy is supplied to the breakerless ignition circuit 10 only through the line 30. However, during the engine's starting mode, electrical energy is supplied to both the line 30 and the line 32.

When the ignition switch 24 connects the line 22 to the switch pole 28 and line 32, electrical energy is supplied to a relay coil 34. Energization of the relay coil 34 closes a relay contact mechanism 36, thereby, to bridge electrical poles 38, 40 and 42. When this occurs, electrical current may flow from the positive line or terminal 20 of the DC source 12, through a line 44 and the contact mechanism 36, to an engine starting motor 46 via a line 48.

The pole 40 of the magnetic relay 34 is connected by lines 50 and 52 to a junction 54. Thus, during engine starting, the DC source 12 is connected by lines 44, 50 and 52 directly to junction 54. This bypasses a ballast resistor 55.

An ignition coil 56 is provided. It has a primary winding 58 and a secondary winding 60. The primary winding 58 is connected at its terminal 62 to the junction 54. The terminal 64 of the secondary winding 60 is connected to the spark gap 66 of a spark plug (not shown). In an engine having a plurality of combustion chambers and/or spark plugs, the terminal 64 of the secondary winding 60 would be connected to the various spark gaps through a suitable distributor mechanism. A line 68 interconnects the opposite ends of the primary winding 58 and secondary winding 60 of ignition coil 56.

The breakerless ignition system 10 includes means for generating an alternating signal having a frequency proportional to the rate at which sparks are to be generated. Preferably, this means comprises a magnetic pickup mechanism generally designated by the numeral 70. The signal generating mechanism 70 includes a permanent magnet 72, a rotating toothed wheel 74, and a pickup coil 76. The toothed wheel 74 is driven by the engine and has a number of teeth corresponding to the number of sparks to be generated. The toothed wheel 74 is rotated by the engine and produces an alternating voltage across the terminals 78 and 80 of the pickup coil 76. This signal has a frequency equal to the rate at which sparks are to be generated. Signal generating mechanisms 70 are commercially available. However, preferred is a signal generating mechanism similar to that described in U.S. patent application Ser. No. 316,945, filed Dec. 20, 1972, in the name of Charles C. Kostan for a "Signal Generating Mechanism" and assigned to the assignee of the present invention.

A portion 82 of the breakerless ignition system 10 operates at a voltage supply level reduced from that of the DC source of electrical energy 12. This is accomplished with a resistor 84 that has its terminal 86 connected to the line 30 and has its other terminal connected by a line 88 to the cathode of a zener diode 90. The anode of the zener diode 90 is connected by a lead 92 to the grounded common line 16. The zener diode 90 has a breakdown voltage substantially less, for example 5.1 volts, than that of the DC source of electrical energy 12. Thus, the line 88 becomes a low voltage supply line.

A resistor 92 is connected at one of its ends to the low voltage supply line 88 and at its other end to the anode of a biasing diode 94, the cathode of which is connected to common line 16. A protection diode 96 has its cathode connected to the junction 98 formed between the resistor 92 and the biasing diode 94. The anode of the diode 96 is connected to the common line 16.

The alternating signal generating mechanism 70 is coupled between the anode of the biasing diode 94 and the base or control electrode 100 of a first transistor Q.sub.1. The coupling is accomplished through a current limiting resistor 102 connecting the junction 98 with the terminal 78 of the magnetic coil 76 and by a base drive resistor 104 connected by a line 106 to the terminal 80 of the pickup coil 76. A capacitor 108 has one of its terminals connected to the line 106 and has its other terminal connected to the common line 16. A protective diode 109 has its cathode connected to the base 100 of the transistor Q.sub.1 and has its anode connected to the common line 16.

The output circuit of the first transistor Q.sub.1 comprises its emitter 110 connected by a line 112 to the common line 16 and its collector 114 connected to the cathode of a thermal tracking diode 116. The anode of the thermal tracking diode 116 is connected to one terminal of a resistor 118, the other terminal of which is connected to the low voltage supply line 88.

A second transistor Q.sub.2 has its base or control electrode 120 connected to one terminal of a resistor 122, the other terminal of which is connected to the low voltage supply line 88. A capacitor 124 has a lead 126 thereof connected to the junction formed between the thermal tracking diode 116 and the resistor 118. The other lead from the capacitor 124 is connected by a lead 128 to the base or control electrode of the second transistor Q.sub.2. The output circuit of the second transistor Q.sub.2 comprises its emitter 130, which is connected to the common line 16 by a line 132 and the line 112, and its collector 134 connected through a resistor 136 to the low voltage supply line 88.

A transistor Q.sub.6 has its collector connected to the collector 114 of the first transistor Q.sub.1, has its emitter connected through line 112 to the common line 16, and has its base electrode connected through a base drive resistor 138 to the junction formed between the collector 134 of the transistor Q.sub.2 and the resistor 136.

The output circuit comprising the collector and emitter electrodes of the second transistor Q.sub.2 is coupled through transistors Q.sub.4 and Q.sub.5 to a base or control electrode 140 of a third transistor Q.sub.3. The output circuit of the third transistor Q.sub.3 comprises its emitter 142 connected to the common line 16 by a line 144 and its collector 146 connected by lines 148 and 150 to the low voltage side, line 68, of the primary winding 58 of the ignition coil 56. A capacitor 152 is connected by its lead 154 to the low voltage terminal of the primary winding 58 and by its other terminal 156 to the common line 16. Series connected zener diodes 158 and 160 are connected between the base or control electrode 140 and the collector 146 of the third transistor Q.sub.3. Also, the anode of a diode 162 is connected by a line 164 and the line 52 to the junction 54 at the high voltage terminal of the primary winding 58. The cathode of the diode 162 is connected to the cathode of a zener diode 166, the anode of which is connected to the common line 16.

The transistor Q.sub.3 performs a switching function with respect to the current path for the primary winding 58 of the ignition coil 56. The transistors Q.sub.4 and Q.sub.5 couple the output circuit of the second transistor Q.sub.2 to the base or control electrode 140 of the third transistor Q.sub.3. Transistors Q.sub.4 and Q.sub.5 also have the important function of current and power amplification.

The transistor Q.sub.4 has its base connected through a resistor 168 to the collector 134 of the second transistor Q.sub.2. The emitter of the transistor Q.sub.4 is connected by a line 170 to the common line 16. Its collector is connected through a diode 172 and a resistor 174 to the low voltage supply line 88.

The transistor Q.sub.5 is a Darlington configuration and comprises two transistors Q.sub.5a and Q.sub.5b. The emitter of the transistor Q.sub.5b is connected to the base or control electrode 140 of the third transistor Q.sub.3. The collectors of transistors Q.sub.5a and Q.sub.5b are connected together at a junction 176, the emitter of transistor Q.sub.5a is connected to the base electrode of transistor Q.sub.5b, and the base electrode of transistor Q.sub.5a is connected by a line 178 to the junction formed between the resistor 174 and the anode of the diode 172. The junction 176 of the collectors of the transistors Q.sub.5a and Q.sub.5b is connected through a resistor 180 and a resistor 182 to the DC source voltage suply line 30. The junction 184 formed between the resistors 180 and 182 is connected by a line 186, a diode 188, and a line 190 to the DC source voltage supply line 32 that is used only in the engine start mode. A resistor 192 is connected between the anode of the diode 188 and the common line 16. Also, a zener diode 194 has its cathode connected to the cathode of the diode 188 and has its anode connected to the common line 16.

With reference now to FIG. 2, there are shown two full cycles of voltage signals, plotted against time, that occur at various points in the breakerless ignition circuit 10. FIG. 2a shows the waveform produced by the alternating signal generating apparatus 70. FIG. 2b shows the voltage signal occurring at the terminal 80 of the pickup coil 76. FIG. 2c shows the waveform occurring at the base electrode of the first transistor Q.sub.1. FIG. 2d is the signal at the collector of the first transistor Q.sub.1. FIG. 2e is the voltage at the lefthand end (line 126) of the capacitor 124. FIG. 2f is the voltage occurring at the righthand end (line 128) of the capacitor 124, and FIG. 2g is the voltage across the capacitor 124. With the exception of FIGS. 2a and 2g, all of the waveforms of FIG. 2 are voltages taken with respect to the common line 16.

In the operation of the breakerless ignition system 10, the circuit causes a spark to be produced at the spark gap 66 at the positive-going zero-crossing points of the alternating signal of FIG. 2a, which is the signal produced by the signal generating mechanism 70. These positive-going zero-crossing points occur at times t=0, t=P, and t=2P.

Let it be assumed that just prior to the positive-going zero-crossing point of the alternating signal produced by the signal generating mechanism 70 the second transistor Q.sub.2 is fully conductive. In such case, current flows from the low voltage supply line 88, through the resistor 122 and the base-emitter junction of the second transistor Q.sub.2, to the common line 16. Current also flows through the resistor 136, the collector 134 and the emitter 130 of the transistor Q.sub.2 to the common line 16. At this time, the collector of the transistor Q.sub.2 is at about 0.2 volts, and as a result, the base-emitter junction of the transistor Q.sub.4 is reverse-biased and transistor Q.sub.4 is nonconductive. This causes the voltage on the line 178 to be very close to the voltage on the low voltage supply line 88. Consequently, the transistor Q.sub.5 is forward-biased and is conductive. This supplies base-emitter current for the third transistor Q.sub.3 which therefore conducts between its collector 146 and emitter 142.

With the ignition switch 24 in the run position and with the third transistor Q.sub.3 conductive, current flows from the DC source of electrical energy 12 through lines 20, 22, 30 and through the ballast resistor 55 to the junction 54 at the high voltage terminal of the primary winding 58 of the ignition coil 56. From the junction 54, the current flows through the primary winding 58, the line 150, and the output circuit of the transistor Q.sub.3, comprising its collector 146 and emitter 142, to the common line 16. This permits a magnetic field to build up the ignition coil 56. The time during which the third transistor Q.sub.3 is conductive to permit current to flow through the primary winding 58 is referred to as the dwell time. If transistor switching times are ignored, the dwell time also is equal to the time during which the second transistor Q.sub.2 is conductive.

When the ignition switch 24 is in the start position and contacts 26 and 28 are both connected by the line 22 to the DC source of electrical energy 12, current flows through both the lines 30 and 32. The current through the line 32 energizes the magnetic relay 34 which causes the contact 36 to bridge the poles 38, 40 and 42 to supply current to the engine starting motor 46. Current also flows from line 32 through the path including line 190, diode 188, and line 186 to the junction 184. This current path supplies the DC source potential less the voltage dropacross the diode 188, to the junction 184. Thus, during engine cranking, the DC source voltage is applied directly to the junction 184 rather than to the upper terminal of the resistor 182, as is the case when the ignition switch is in the run position. During engine cranking, this increases the current through the output circuit of the transistor Q.sub.5 and therefore increases the current drive for the transistor Q.sub.3. This helps assure the presence of an adequate current in the primary winding 58 of the ignition coil 56 during engine cranking. Also, it should be noted that when the ignition switch is in the start position and the magnetic relay 34 is energized, current flows from the DC source 12 through the line 44 and relay pole 40 and through the lines 50 and 52 to the junction 54 of the primary winding 58 of the ignition coil 56. This means that the ballast resistor 55 is short-circuited during the engine starting mode.

In summary, when the transistor Q.sub.2 is conductive, the transistor Q.sub.4 is nonconductive and the transistors Q.sub.5 and Q.sub.3 are conductive so that current flows through the primary winding 58 of the ignition coil 56.

With the second transistor Q.sub.2 conductive, the base-emitter voltage drop of this transistor causes the voltage at the right-hand end (line 128) of the capacitor 124 to be at a potential of about 0.7 volts. Also, the capacitor 124 is being or will have been charged, with the polarity indicated in FIG. 1, through the resistor 118 and the base-emitter circuit of the transistor Q.sub.2. Thus, the left-hand end (line 126) of the capacitor 124 will have attained a voltage level approaching that of the low voltage supply line 88.

At all times, current flows from the low voltage supply line 88 through the resistor 92 and the biasing diode 94 to the common line 16. This places the junction 98 at the anode of the biasing diode 94 at a potential of about 0.7 volts. As the toothed wheel 74 of the alternating signal generating mechanism 70 rotates, the voltage across the terminals 80 and 78 varies as shown in FIG. 2a. When the alternating signal becomes such that the terminal 80 is positive with respect to the terminal 78, this signal voltage together with the voltage drop across the biasing diode 94 are additive and become sufficient to cause a base-emitter current to flow through the first transistor Q.sub.1. This renders the transistor Q.sub.1 conductive and current flows through the resistor 118, the thermal tracking diode 116, the collector 114 and emitter 110 of the first transistor Q.sub.1, and the line 112 to the common line 16. The transistor Q.sub.1 becomes saturated, its collector being at a voltage of about 0.2 volts and the anode of the tracking diode being then at a voltage of about 0.9 volts. Because it is connected to the anode of the tracking diode 116, the left-hand end of the capacitor 124 must drop to a voltage level of about 0.9 volts.

As a consequence of the charge accumulated on the capacitor 124, its right-hand end, line 128, must fall to a voltage level below ground potential. This voltage on the line 128 is applied to the base or control electrode 120 of the second transistor Q.sub.2 rendering it nonconductive. As a result, the collector 134 of the second transistor Q.sub.2 rises to a voltage level near that of the low voltage supply line 88, and this voltage is applied through the resistor 138 to the base of the transistor Q.sub.6 rendering it conductive. With the transistor Q.sub.6 conductive, spurious voltages or transients that may occur at the base or control electrode 100 of the first transistor Q.sub.1 do not affect the conductivity of the circuit between the cathode of the diode 116 and the common line 16. Thus, the transistor Q.sub.6 is a device used to insure that the transistor Q.sub.2 will remain nonconductive once the transistor Q.sub.1 has been triggered by the zero-crossing signal produced by the signal generating mechanism 70.

When the transistor Q.sub.2 is rendered nonconductive, the potential on its collector 134 is applied to the base of the transistor Q.sub.4 causing it to have a forward-biased base-emitter junction and rendering it fully conductive. This in turn applies a low potential to the line 178 connected to the base of the transistor Q.sub.5 rendering it nonconductive. With the transistor Q.sub.5 nonconductive, the third transistor Q.sub.3 has no base drive and it also becomes nonconductive. When the transistor Q.sub.3 becomes nonconductive, the current in the primary winding 58 of the ignition coil 56 is interrupted, and the magnetic field in the ignition coil must collapse. This produces an EMF in the secondary winding 60 of the ignition coil and causes a spark to occur in the spark gap 66. The secondary current flows through the capacitor 152 to ground.

As long as the transistor Q.sub.2 is nonconductive, the third transistor Q.sub.3 remains nonconductive. However, when the transistor Q.sub.1 becomes conductive, the capacitor 124 discharges in a current path including the resistor 122, the capacitor 124, the diode 116, and the collector-emitter circuits of the transistors Q.sub.1 and Q.sub.6. This causes the voltage at the right-hand end, line 128, of the capacitor 124 to rise in value. When the voltage at this end of the capacitor 124 exceeds ground potential, the second transistor Q.sub.2 begins to conduct once again and eventually becomes saturated. This reduces the voltage at the collector 134 of the transistor Q.sub.2 to a low value, and because this signal is applied to the base of the transistor Q.sub.6, through resistor 138, the transistor Q.sub.6 is rendered nonconductive. The transistor Q.sub.1, however, remains conductive until the signal produced by the alternating signal generating mechanism 70 goes negative, that is, until the terminal 80 of the pickup coil 76 becomes negative with respect to the terminal 78. When the terminal 80 becomes negative with respect to the terminal 78, the transistor Q.sub.1 becomes nonconductive. This prepares it to receive the next trigger signal. The nonconductivity of the transistor Q.sub.1 permits the capacitor 124 to once again charge to the polarity indicated in FIG. 1.

At the moment that the second transistor Q.sub.2 becomes conductive, the transistor Q.sub.4 becomes nonconductive, the transistor Q.sub.5 becomes conductive, and the third transistor Q.sub.3 becomes conductive. The conduction of the transistor Q.sub.3 closes the current path for the primary winding 58 permitting its magnetic flux to build up once again. This is the onset of the next period of dwell time.

The breakerless ignition system 10 includes various protective devices. The diode 96, along with the resistor 102, provides protection of the diode 94 from arc-over that might occur from the high voltage side of the ignition coil secondary to the terminal 78 of the alternating signal generating mechanism 70. This might occur because of the proximity of the ignition coil secondary circuit to the signal generating mechanism when these are included in a single distributor housing.

The diode 109, along with the resistor 104, provides protection of the base-emitter junction of the first transistor Q.sub.1 from high voltage arc-over from the ignition coil secondary circuit to the terminal 80 of the alternating signal generating mechanism 70.

The capacitor 108 prevents ignition system oscillation when the alternating signal input from the pickup coil 76 is a low voltage, such as would occur at low engine speeds.

The diode 116 is used for thermal tracking and its forward voltage drop tracks the base-emitter voltage drop of the second transistor Q.sub.2 to provide thermal stability in the circuitry. This helps insure the proper generation of dwell time required by the primary winding 58 of the ignition coil 56.

The diode 172 prevents damage to the transistor Q.sub.4 that might be caused as a result of negative transients, such as a negative magnetic-field-decay transient, that might occur on the line 30.

The resistor 192 reduces transient levels produced by the magnetic relay 34, and therefore reduces the voltage requirement of the diode 188.

The diode 188 provides extra drive during engine cranking as previously described. It also prevents voltage feedback through lines 186 and 190 to the magnetic relay 34 when the ignition switch 24 is in the run position.

The zener diode 194, along with the resistor 182, provides protection of the transistor Q.sub.5 from load-dump transients. Load dump transients occur when an alternator is supplying a current load that is suddenly dumped. This is a large, positive transient.

Zener diodes 158 and 160, connected in series, render the transistor Q.sub.3 conductive if its collector line 148 rises above a voltage of, for example, 360 volts. This prevents excess voltage at the collector junction.

The zener diode 166, along with the ballast resistor 55, provides protection of the transistor Q.sub.3 from a load dump transient. The diode 162 is connected in series with the zener diode 166 to protect it in the event of a reversal of the polarity of the direct current source of electrical energy 12. The diode 162 preferably is of the avalanche type to prevent damage to it in the event of a high voltage arc-over from the secondary winding line 64 to the junction 54 of the primary winding.

By way of example and not limitation, the various components of the breakerless ignition system 10 may be of the following types or have the following values:

Transistor Q.sub.1 2N3859A Transistor Q.sub.2 2N3859A Transistor Q.sub.3 2N6306 or Texas Instruments T1P535 Transistor Q.sub.4 2N3859A Transistor Q.sub.5 RCA 2N6055, Motorola MJ1000 or Texas Instruments T1P640 Transistor Q.sub.6 2N3859A Resistor 92 8.2 kilohms Resistor 102 120 ohms Resistor 104 6.8 kilohms Resistor 118 150 kilohms Resistor 122 110 kilohms Resistor 138 15 kilohms Resistor 136 10 kilohms Resistor 168 2.2 kilohms Resistor 84 180 ohms, 2 watts Resistor 174 560 ohms Resistor 192 470 ohms, 1 watt Resistor 182 6.8 ohms, 10 watts Resistor 180 3.0 ohms, 10 watts Resistor 141 27 ohms, 2 watts Resistor 55 1.35 ohms Capacitor 124 0.22 microfarad Capacitor 152 0.3 microfarad Capacitor 108 0.01 microfarad Zener diode 90 5.1 volts, 1N5231A Zener diode 194 27 volts, 5 watts, 1N5361A Zener diodes 158 180 volts each, 1N5279 and 160 Zener diode 166 27 volts, 75 watts Diode 94 1N4451 Diodes 96 1N4152 Diode 109 1N4152 Diode 116 1N4152 Diode 172 1N4152 Diode 188 1N5625 Diode 162 1N5625

Claims

Based upon the foregoing description of the invention, what is claimed is:

1. A breakerless ignition system for a spark ignition internal combustion engine, which comprises:

a DC source of electrical energy having positive and negative terminals;

means for generating an alternating signal having a frequency proportional to the rate at which sparks are to be generated;

a first resistor having first and second terminals, said first terminal being connected to said positive terminal of said DC source of electrical energy;

a zener diode having its cathode connected to said second terminal of said first resistor and having its anode connected to said negative terminal of said DC source of electrical energy;

a second resistor having first and second terminals, said first terminal being connected to said cathode of said zener diode;

a third resistor having first and second terminals, said first terminal being connected to said cathode of said zener diode;

a capacitor having a first terminal connected to said second terminal of said second resistor and having a second terminal connected to said second terminal of said third resistor;

a first transistor having a control electrode and having an output circuit, said first transistor output circuit being coupled to said second terminal of said second resistor;

a second transistor having a control electrode and having an output circuit, said second transistor output circuit being coupled to said second terminal of said third resistor;

a biasing diode having its cathode connected to said negative terminal of said DC source of electrical energy;

a fourth resistor having first and second terminals, said first terminal being connected to the cathode of said zener diode and said second terminal being connected to the anode of said biasing diode;

circuit means, connected to said anode of said biasing diode and to said control electrode of said first transistor, for coupling said alternating signal having a frequency proportional to the rate at which sparks are to be generated to said control electrode of said first transistor and for coupling thereto a biasing voltage generated by a current in said biasing diode;

an ignition coil having a primary winding, said primary winding having first and second terminals, said first terminal therof being connected to said positive terminal of said DC source of electrical energy;

a third transistor having a control electrode and having an output circuit, said output circuit of said third transistor being coupled to said second terminal of said ignition coil primary winding and to said negative terminal of said DC source of electrical energy;

circuit means for coupling said output circuit of said second transistor to said control electrode of said third transistor; and

a fourth transistor having a control electrode and an output circuit, said fourth transistor control electrode being coupled to said second transistor and said fourth transistor output circuit being connected in parallel with said first transistor output circuit.

2. A breakerless ignition system in accordance with claim 1, wherein said fourth transistor is conductive when said second transistor is nonconductive.