US3340861A

US3340861A - Transistorized ignition circuit

Info

Publication number: US3340861A
Application number: US396834A
Authority: US
Inventors: Schiff Peter
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1964-09-16
Filing date: 1964-09-16
Publication date: 1967-09-12
Anticipated expiration: 1984-09-12
Also published as: DE1464064B2; DE1464064A1; GB1061827A

Description

Sept. l2, 1,967 P. scHlFF 3,340,861

- TRANSISTORIZED IGNITION CIRCUIT Filed Sept. 16, 1964 United States Patent O 3,340,861 'IRANSISTORIZED IGNITION CIRCUIT Peter Schilf, Somerville, NJ., assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 16, 1964, Ser. No. 396,834 12 Claims. (Cl. 12S- 148) the primary winding of the ignition coil to a safe value,

especially under stall or idle conditions. This ballast -resistance may be built into the coil or may be in the form of a separate ballast resistor. During starting, when a good spark is particularly desirable, the battery voltage available for ignition may be substantially reduced due to the large amount of current required by the starting motor, and this voltage is reduced still further by the previously mentioned ballast resistance. This reduction in voltage results in a proportional decrease in the primary winding current. Since the spark energy is a function of the second power of primary winding current value, the energy per spark is greatly reduced by a small reduction in primary winding current. Switch means may be provided to short -circuit the ballast resistor during starting to provide higher ignition coil current at that time. During high speed operation, when the ignition points are closed only for a short time, the ballast resistance may so lengthen the time constant of the circuit including the ignition coil and, therefore, the time required for sucient current to build up in the coil, that suicient energy may not be stored in the primary `winding of the ignition coil, during the short time that the points are closed between sparks, to insure good ignition. Therefore, the provision of a series resistance in the ignition circuit of an internal combustion engine, while providing necessary current limiting during stall and low speed operation, is detrimental to starting and high speed operation of internal combustion engines using spark ignition.

Furthermore, in many ignition systems, the ignition points are burned or pitted during operation thereof due to the making and breaking of high currents by the ignition points and due to the high voltage induced across them (called inductive kick back) as the result of the highly inductive ignition circuit. In such circuits, the ignition points must be adjusted or replaced periodically. Circuits including vacuum tubes and transistors are known in which ignition points are unnecessary or in which the current flowing through the points is minimized and in which the inductance of the ignition coil is isolated from the ignition points, whereby ignition troubles due to point burning and pitting are avoided. In many of these electronic ignition systems, a transistor or vacuum tube acts as a switch in the series circuit including the primary winding of the ignition coil. In such circuits using transistors, excessive current ilow in the ignition coil during stall and slow speed operation of the engine may cause the Voltage induced across the series switching transistor, when the ignition points are subsequently opened, to ybuild up to a point where the inductive kick back may cause failure of the switching transistor. The transistor may be protected Iby limiting the effect of this kick back -by connecting a Zener diode or a capacitor across the primary winding of the coil, or across the switching transistor itself. By limiting the primary winding current, the protective components may be reduced to a minimum size and the overall eciency of the circuit may be increased.

It is an object of this invention to provide an improved transistorized internal combustion engine ignition system.

It is a further object of this invention to provide an improved transistorized ignition system in which ballast resistance is not required. I

Another object of this invention is to provide an improved transistorized ignition system for internal combustion engines which reduces the time in which increased current through the ignition Icoil is attained compared to that required in such ignition systems known heretofore.

An additional object of this invention is to provide an improved transistorized ignition system presenting improved high speed engine performance coupled with good starting characteristics.

In accordance with this invention, the switching transistor of a tr-ansistorized ignition system is operated at saturation to initiate current flow therethrough and through the ignition coil, and this current ow is limited by suitable means to a desired maximum value regardless of the voltage of the supply source (above a certain low value thereof) and independently of the time the ignition points are closed and the switching transistor is conductive.

The novel features of this invention, both as to its organization and method of operation, as well as additional objects and -advantages thereof, will be understood more readily from the following description, when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of an internal combustion engine ignition circuit according to this invention in which the battery positive terminal and one of the ignition points are grounded;

FIG. 2 is a circuit diagram of another embodiment of this invention in which the battery negative terminal and one of the ignition points are grounded;

FIG. 3 is a circuit diagram of a further embodiment in :accordance with this invention.

In FIG. 1, the negative terminal 10 of a potential source as indicated, such as the battery of an automobile, is connected to the emitter of an NPN switching transistor 12 through a small emitter resistor 14. The collector of the switching transistor 12 is connected to the other terminal 16 of the potential source, which may be grounded, through the primary winding of an ignition transformer'or coil 18. A voltage limiting Zener diode 20 may be connected between the emitter and the collector of the switching transistor 12 for a purpose to be explained. The secondary or high voltage winding of the ignition transformer or coil 18 is connected between the terminal 16 and the distributor of a multi-cylinder internal combustion engine. The negative terminal 10 of the potential source is also connected to the terminal 16 through a resistor 22, and through the emitter to collector path of an NPN driver transistor 24 and a further resistor 26, all in series. The emitter of the driver transistor 24 is also connected to the base of the switching transistor 12. A fourth resistor 28 is connected `between the terminal 10 and the base of the transistor 24. A fth resistor 30 and a switch 32, which represents the engine ignition points, are connected in series between the base of the driver transistor 24 and the terminal 16. A plurality of diodes 34 in series are connected in parallel with the resistor 28. The diodes 34 are poled to be conductive with respect to the potential source, i.e., cathode to anode, and final cathode directly to the-negative terminal 10. In the normal operation of the internal combustion engine of which the circuit described above is the ignition circuit, the normally closed points 32 are opened, when an ignition sparkis needed, by a cam (not shown) that is rotated 'by the engine. The circuit of FIG. 1 is adapted to be used with an engine Where the positive terminal of the battery is grounded and where it is advantageous to ground one of the ignition points.

VConsidering the operation of the circuit of FIG. l, when the points 32 are opened, no voltage is applied to the base of the driver transistor 24 with respect to the emitter thereof, whereby substantially no current flows between the collector and the emitter of the driving transistor 24, and no current tlows into the base of the switching transistor 12. The switching transistor 12 is opened circuited and substantially no current ows through the primary winding of the coil 18. When the points 32 are in contact or closed, a positive voltage is applied to the base of the NPN driving transistor 24 with respect to its emitter throu-gh resistor 30. The voltage drop across the resistor 28 is limited by the forward conduction voltage drop of the diodes 34 in series. By suitably choosing the number and types of these diodes 34, the voltage applied thereby between the negative side of the battery and the base of the driving transistor 24 may be predetermined. The driving transistor 24, which acts as a current ampliier, becomes conductive and current flows through the resistors 22 and 26. Due to the connection of the emitter of the driving transistor 24 and the base of the switching transistor 12, a voltage which is positive with respect to the emitter of the switching transistor 12 appears on the base thereof. The diodes 34, due to the described circuit, 'are effectively connected from the base of the transistor 12 to the terminal 10. The switching transistor 12 immediately becomes fully conductive or saturated and current builds up in the primary winding of the coil 18 and in the resistor 14 during a period of time depending on the time constant of the circuit including the primary winding of the ignition coil 18. As the current builds up in the emitter resistor 14, the voltage drop across this resistor builds up at the same rate. This voltage is in a direction to reduce the positive voltage on the base of the `switching transistor 12 with respect to its emitter. This voltage builds up to the point where the voltage between the base and emitter of the switching transistor 12 is at some value such that the switching transistor 12 operates below saturation thereof and at a safe operational value. The switching transistor current is limited to the safe operational value by the voltage developed in its emitter to base circuit. As pointed out above, the switchingr transistor operates in saturation during the early part of the current build-up period of the ignition coil. Therefore, current builds up to this limited value as fast as the time constant of the ignition coil primary winding circuit permits. The resistance value of the emitter resistor 14 is so chosen that the voltage between the emitter and the base of the transistor 12 is equal to about the threshold voltage of the base emitter path of the transistor at the maximum desired current through the transistor 12. The resistor 14 which, in one particular embodiment of this invention, has a value of one-tenth to two-tenths of an ohm does not act as a ballast resistor since the voltage drop thereacross at maximum current flow may be only 1 to 2 volts. The current through the switching transistor 12 is limited by the operation of the circuit described to nearly the same value for widely varying supply voltages (from about three and a half volts to about 14 volts) and for widely varying periods of ignition point closure, whereby no current limiting resistance need be built into the ignition coil and no ballast resistor or any switch for disconnecting a ballast resistor from the ignition system is necessary, and yet this described circuit provi-des quick build-up of current ow to a maximum value which provides a hot ignition spark when the ignition coil circuit is broken. Therefore, the described ignition circuit causes operatori in an improved manner of engines of which it is a part, during starting, stall, idling, and high speed operation thereof, and independently of available battery voltage, within a wide range, as compared to engines having known ignition systems.

The Zener diode 20 across the collector and emitter of the switching transistor 12 protects the transistor 12 from the high voltage kick back induced in the primary winding of the ignition coil 18 during operation of the above dcscribed circuit by providing a shunt between the emitter and collector for kick back voltages.

FIG. 2 shows a circuit of an embodiment of this invention in which additional current limiting is provided and in which the negative terminal of the supply source (not shown) and one of the ignition points may be grounded. In this gure, the positive terminal 36 of the supply source is connected to the collector of an NPN switching transistor 38 through the primary winding of an ignition coil 40. A capacitor 42 may be connected across this primary Winding for a purpose to be disclosed. One terminal of the secondary winding of the ignition coil 40 is connected to the positive terminal 36, and the other terminal of the secondary winding may go to the distributor (not shown) of a multi-cylinder internal combustion engine. The emitter of the switching transistor 38 is connected to the other terminal 44 of the source, which other terminal may be connected to ground, through a small emitter resistor 46, A pair of diodes 48 in series, shunted by a resistor 50, are connected between the base of the switching transistor 38 and the terminal 44. The diodes 48 are poled so that the low resistance direction of current -flow therethrough is from the base of the transistor 38 to the terminal 44. The emitter of a PNP driving transistor 52 is connected to the positive terminal 36 through a small emitter resistor 54. The collector of the driving transistor 52 is connected to the terminal 44 through the resistor 50. A diode 56 and a resistor 58 in parallel are connected between the positive terminal 36 and the base of the driving transistor 52. The diode 56 is poled so that its low resistance direction of current ow is from the terminal 36 to the base of the driving transistor 52. The base of the driving transistor 52 is also connected to the terminal 44 through a resistor 60 and a switch 62 which rrepresents the engine ignition points. These points 62, as noted above, are normally closed and are opened momentarily by a cam (not shown) to produce an ignition spark.

The operation of FIG. 2 is as follows: When the ignition points 62 are opened, the emitter and base of the driving transistor 52 are at zero potential with respect to each other, whereby the driving transistor 52 is nonconductive and no current ows through the resistors 50 and 54. The base and the emitter of the switching transistor 38 are also at zero potential with respect to each other and no current ows through the switching transistor 38 0r through the primary winding of the ignition coil 40, which is in series therewith. When the ignition points 62 are closed, current 4flows through the resistors 58 and 60 in series and the voltage on the base of the driving transistor 52 becomes negative with respect to the voltage on its emitter. The driving transistor 52 conducts and current flows from the positive terminal 36 through the resistor 54, through the emitter to collector path of the driving transistor 52 and through the resistor 50 to the terminal 44. The voltage drop between the emitter and base of the driving transistor 52 is limited to the voltage drop of the diode 56 in its forward direction, less the voltage drop developed `across the small emitter resistor 54. 'Ihe effect of the voltage across the diode 56 and resistor 54 is to limit the current through the driving transistor 52 to a value less than that at saturation thereof. The voltage across the resistor 50 is applied across the diodes 48 in the forward direction, and also between the base and emitter of the switching transistor 38 in series with the emitter resistor 46 in a direction to render the transistor 38 conductive. The voltage developed across the resistor 50 is limited to the drop across the diodes 48 in series in their forward direction, and the voltage applied between the emitter and the base of the transistor 38 is the voltage developed across the diodes 48 in series less the voltage developed across the resistor 46 which may have a resistance of 0.1 to 0.2 ohm. When no current is owing in the resistor 46, this voltage is sucient to drive the switching transistor 38 into saturation. Current builds up in the collector-to-emitter path of the switching transistor 38 and in the primary winding of the ignition coil 40 at a rate determined by the time constant of the ignition coil circuit. The voltage across the resistor 46, which builds up at the same rate, opposes the Voltage across the diodes 48 in series, thereby limiting the current through the switching transistor 38 to a value less than the saturation value. The limited current flow through the collector of the transistor 52 provides a substantially constant current in the parallel circuit comprising the resistor 50 and the diodes 48. The Voltage drop across the diodes 48 is more nearly constant than if the current therethrough were not so limited by operation of the circuit of the transistor 52. Since the voltage across the diodes 48 is stabilized, the maximum current ow through the transistor 38, which depends on the dilerence of voltage developed across resistor 46 and the diodes 48 in series is more nearly independent of the voltage of the source than if the transistor 52 had no current limiting function. The result is that the current through the primary of the coil 40 rises very quickly to a safe and suflicient operating value for high speed operation, and the current is limited to a safe operative value for a wide range of supply voltages and periods of closure of the points ranging from stall to high speed operation. A condenser 42 may be provided across the coil 40 to limit the voltage developed across the transistor 38 by the inductive kick back when the points 62 are opened by the engine cam. By choice of the number and types of

diodes

56 and 48 and the size of the resistors 54 and 46, the limited Value of the current which ows through the ignition coil 40 may be selected to provide a desired maximum current through the transistor thereby to produce a good ignition spark .at all conditions of engine operation. The

diodes

56 and 48 provide a temperature compensating elfect for their associated transistors in a known manner. Therefore, if silicon transistors are used, it is preferable to use silicon diodes, since the temperature resistance characteristics of the silicon diodes 48 `and of the silicon transistor 38 are similar.

In the embodiment of FIG. 3, an ignition circuit is shown that requires no driving transistor. The positive terminal 36 of a source (not shown) is connected through the primary winding of an ignition coil 40 and through the collector to emitter path of an NPN switching transistor 38 and through a small emitter resistor 46 to the other terminal 44. One terminal of the secondary winding of the ignition coil 40 is connected to this positive termin-al 36 and the other terminal of the secondary winding is connected to the distributor (not shown). The positive terminal 36 is also connected through the ignition points 66 and a resistor 64 and two diodes 48 in series to the other terminal 44. The two diodes 48 are connected in their forward direction between the base of transistor 38 and the other terminal 44. The base of the transistor 38 is connected to a point between the diodes 48 and the resistor 64.

Operation of the circuit of FIG. 3 is like that of the circuit of FIG. 2 described hereinabove. When the points 66 are opened, the Voltage on the emitter and the base of the transistor 38 is practically the same whereby the transistor is substantially non-conductive. Upon closing the points 66, a voltage is applied to the base of the transistor 38 that is positive with respect to its emitter, causing the transistor 38 to become saturated. This voltage on the base with respect to the emitter is limited by the voltage drop of the diodes 48 in their forward direction and is equal to the drop across these diodes 48 less the voltage drop across the resistor 46. The current 'through the circuit including the coil primary winding and the transistor 38 rises at a rate determined by the time constant of the circuit including the coil primary winding, -and the voltage across the'resistor 46 rises at the same rate. The transistor 38 operates at saturation for the Alirst part of the period of conductivity thereof. The current continues to rise in value to its maximum. The maximum current through the transistor 38 is limited by the voltage applied between the emitter and 'base thereof. This voltage is less than the xed drop across the series diodes 48 by the voltage drop across the resistor 46. When the points 66 are closed, the current through the coil 40 rises quickly to a maximum value which is determined by the voltage between the emitter and the base of the transistor 38. Thus the ignition systern produces a hot spark and requires no ballast resistance, -and yet operates in an improved manner in a Wide range of speeds. The transistor 38 in FIG. 3 may be such that kick back protection therefor is not necessary.

In each of FIGS. 2 and 3 the resistance Value of the emitter resistors 46 and 54 are so chosen that the voltage across each emitter resistor at m-aximum desired current through th-e transistor to which it is connected, plus the threshold voltage of the base-emitter path of said transistor, is equal to the forward threshold voltage of the diode, or diodes in series, connected to the base of said transistor.

While three ignition circuits according to the present invention have been shown and described, it will undoubtedly be `apparent to those skilled in the art that variations thereof are possible within the spirit of this invention. For example, by reversing the voltages and the connections of the diodes, PNP transistors may be substituted for the NPN transistors in the several figures and an NPN may be substituted for the PNP transistor shown in FIG. 2. Other changes will, no doubt, also suggest themselves readily. Hence, it should be understood that the foregoing description is to be considered as illustrative and not in a limiting sense.

What is claimed is:

1. A transistor circuit comprising (a) a pair of terminals for connection to a source of potential,

(b) a switching transistor having an emitter and a collector,

(c) an inductive load connected between one of said terminals and said collector,

(d) an emitter resistor connected between said emitter and the other of said terminals,

(e) means to render said transistor alternately nonconductive and conductive, and

(f) means including said emitter resistor to cause said transistor to conduct in a saturated manner during the early part of 'current build up through the transistor and tolimit the maximum current ow therethrough to -a predetermined operating value.

2. A transistor circuit comprising (a) a pair of terminals for connection to a source of potential,

(b) a switching transistor having an emitter, a collector and a base electrode,

(e) at least one diode connected between said base and said emitter through said emitter resistor, said diode being poled in the current conductive direction from said terminal connected to said collector through the internal collector-to-base path of said transistor to the other terminal of said source, and

(f) means to render said transistor alternately conductive and non-conductive, said diode and said emitter resistor acting to cause conduction saturation of said switching transistor during the early part of current buildup therethrough when conductive, and to limit the maximum current flow therethrough to a predetermined operating value.

3. A tra'nsistorized ignition system comprising (a) an ignition coil having primary and secondary windings,

(b) a pair of terminals for connection to a source of potential,

(c) a switching transistor having an emitter and a collector,

(d) an inductive load comprising said primary winding connected between one of said terminals and said collector,

(e) an emitter resistor connected between said emitter and the other of said terminals,

() a pair of openable and closeable ignition points,

(g) means responsive to the opening and closing of said points to render said transistor respectively non-conductive and conductive, and

(h) means including said emitter resistor to cause said transistor to conduct in a saturated manner during the early part of current build up therethrough when said points are closed and to limit the maximum current ow therethrough to a predetermined operating value.

4. A transistorized ignition system comprising (a) an ignition coil having primary and secondary windings,

(b) a pair of terminals for connection to a source of potential,

(c) a switching transistor having an emitter and a collector,

(d) a small emitter resistor connected between one of said terminals and said emitter,

(e) said primary winding of said coil being connected between said collector and the other of said terminals,

(f) a second transistor having main electrodes and a control electrode, said main electrodes being connected between said terminals,

(g) means including a pair of openable and closable ignition points to render said second transistor nonconductive and conductive respectively in response to opening and closing of said points,

(h) voltage limiting means connected between one of said main electrodes and said control electrode of said second transistor, and

(i) means responsive to the flow of current in said second transistor to cause said switching transistor to conduct, said voltage limiting means and said emitter resistor acting to permit conduction of said switching transistor in a saturated manner during the early part of current build-up therethrough and to limit the maximum current therethrough to a predetermined operating value.

5. A transistorized ignition system comprising (a) an ignition coil having primary and secondary windings,

(b) a pair of terminals for connection to a potential source,

(c) a switching transistor having an emitter, a -collector, and a base electrode,

(d) said primary winding being connected between said collector of said transistor and one of said terminals,

(f) voltage limiting means effectively connected between said base of said switching transistor and said other terminal7 (g) a pair of openable and closable ignition points connected in a circuit between said terminals, and

(h) means responsive to opening and closing of said points for rendering said switching transistor, alternately non-conductive and conductive, said voltage limiting means and said resistor acting to permit conduction of said switching transistor in a saturated manner during the early part of current build-up therethrough and to limit the maximum current therethrough to a predetermined operating value.

6. A transistorized ignition system comprising (a) a pair of terminals for connection to a source of potential,

(b) a switching transistor having an emitter, a collector and a base electrode,

(c) an ignition coil having primary and secondary windings, said primary winding being connected between one of said terminals and said collector,

(e) at least one diode connected between said base and said emitter through said emitter resistor, said diode -being poled in current conductive direction from said terminal connected to said collector through the internal collector-to-base path of said transistor to the other of said terminals,

(f) a pair of openable and closable ignition points, and

(g) means responsive to the closing of said ignition points to apply a current to the base of said transistor to render it conductive, said diode and said emitter resistor acting to permit conduction of said switching transistor in a saturated manner during the early part of current build-up therethrough, and to limit the maximum current flow therethrough to a predetermined operating value.

7. A transistorized ignition system comprising (a) a pair of terminals for connection to a source of potential,

(b) a switching transistor having an emitter, a collector, and a base electrode7 (c) an ignition coil having primary and secondary windings, said primary winding being connected between one of said terminals and said collector,

(d) a first emitter resistor connected between said emitter and the other of said terminals,

(e) at least one diode connected between said base and said emitter through said first emitter resistor, said diode being poled in current conduction direction from said terminal connected to said collector through the internal collector-to-base path of said transistor to the other of said terminals,

(f) a second transistor having an emitter, a collector and a base,

(g) a second emitter resistor and a collector resistor,

(h) said second transistor emitter being connected to said one terminal of said source through said second emitter resistor,

(i) said second transistor collector being connected to said other terminal of said source through said collector resistor and said diode in parallel,

(j) an additional diode connected between said one terminal of said source and the base of said second transistor and poled in its current conductive direction, with respect to said source,

(k) a pair of openable and closable ignition points, and

(l) means responsive to the closing of said ignition points to apply a current to the base of said second transistor to'cause it to conduct, said second diode `and said second emitter resistor acting to cause limite-d current ow through said collector resistor,

said limited current flow causing said switching transistor to conduct, said iirst diode and said rst emitter resistor acting to cause said switching transistor to begin to conduct in a saturated manner and to limit the maximum current ow through said switching transistor to a predetermined maximum value. 8. A transistorized ignition system comprising (a) a circuit having (1) a pair of terminals for connection to a current Supply, (2) an ignition coil including a primary winding, (3) a switching transistor having an emitter-tocollector path, and (4) a small emitter resistor,

said emitter-to-collector path, said primary -winding and said resistor being connected in series between said pair of terminals, and said emitter being connected to one terminal of said emitter resistor,

(b) openable and closable ignition points,

(c) circuit means including said points for rendering said switching transistor alternately non-conducting and conducting at saturation in response to opening and closing of said points, respectively, and

(d) means including said emitter resistor for limiting the maximum current flow through said transistor to less than the saturation value thereof.

9. A transistorized ignition system comprising (a) a circuit having (l) a pair of terminals for connection to a current Supply, (2) an ignition coil including a primary winding, (3) a switching transistor having an emitter-tocollector path, and (4) a small emitter resistor;

said emitter-to-collector path, said primary winding and said emitter resistor being connected in series between said pair of terminals, and said emitter being connected to one terminal of said emitter resistor,

(b) openable and closable ignition points,

(c) circuit means including said points for rendering said switching transistor alternately non-conductive and conductive at saturation in response to opening and closing of said points, and

(d) at least one diode effectively connected in its forward conductive polarity from the base to the emitter of said transistor through said emitter resistor, said diode and said emitter resistor acting to limit the maximum current through said transistor to a value less than the saturation value thereof.

10. A transistorized ignition system comprising (a) a pair of terminals for connection to a current source,

(b) a switching transistor having an emitter, a collector, and a base electrode,

(c) a iirst emitter resistor connected between a rst one of said terminals and said emitter,

(d) an ignition transformer having a primary winding connected between said collector and the other of said terminals,

(e) at least one diode connected between said base and said first terminal poled for current conduction from said source,

(f) at least one other resistor,

(g) a pair of ignition points,

(h) one of said points being connected to said irst terminal,

(i) the other of said points being connected to said other terminal through said other resistor,

(j) an additional diode connected across said other resistor,

(k) a driving transistor having an emitter, a collector,

and a base,

(l) a second emitter resistor connected between aterminal of other resistor and the emitter of said driving transistor, A

(m) the base of said driving transistor being connected to the other terminal of said other resistor,

(n) said additional diode being poled for current conduction therethrough from said source,

(o) a connection between said collector of said driving transistor and said base of said switching transistor, and

(p) a further resistor connected across Said first named diode.

11. A transistorized ignition system comprising (a) a pair of terminals for connection to a current source,

(b) a switching transistor having an emitter, collector,

and a base,

(c) an emitter resistor connected between a first one of said terminals and said emitter,

(d) an ignition transformer having a primary winding connected between said collector and the other terminal of said source,

(e) a resistor connected between said base and said first terminal,

(f) a driving transistor having main electrodes and a control electrode,

(g) a connection from one of said main electrodes to the base of said switching transistor,

(h) a resistive connection from the other of said main electrodes to said other terminal of said source, (i) a resistor connected from said rst terminal to said control electrode,

(j) at least one diode connected across said last named resistor, said diode being poled for current conduction from said source, and

(k) a pair of ignition points,

(l) one of said points being connected to said other source terminal and the other of said points being connected to said control electrode.

12. A transistorized ignition system comprising (a) a pair of terminals for connection to a source of current,

(b) a switching transistor having an emitter, a collector and a base,

(c) an ignition coil having a primary winding connected between said collector and one of said terminals,

(d) a small emitter resistor,

(e) said emitter being connected through said small emitter resistor to the other terminal of said source,

(f) a pair of ignition points,

(g) an additional resistor connected through said pair of ignition points to said one terminal,

(h) at least one diode,

(i) said last named resistor being connected through said diode to the other terminal of said source, and

(j) -a connection between the junction of said last named resistor and said diode to said base, said diode being poled for current conduction between said terminals with respect to said source.

References Cited UNITED STATES PATENTS 3,016,476 1/1962 Bataille 123-148 3,016,477 1/ 1962 Naborowski 123-148 3,219,876 11/1965 Bays et al. 123-148 3,249,808 5/1966 Short 123-148 3,259,798 7/1966 Yonge 123-148 3,288,125 11/1966 Guyton et al. 123-148 LAURENCE M. GooDRIDGE, Primary Examiner.

Claims

1. A TRANSISTOR CIRCUIT COMPRISING (A) A PAIR OF TERMINALS FOR CONNECTION TO A SOURCE OF POTENTIAL, (B) A SWITCHING TRANSISTOR HAVING AN EMITTER AND A COLLECTOR, (C) AN INDUCTIVE LOAD CONNECTED BETWEEN ONE OF SAID TERMINALS AND SAID COLLECTOR, (D) AN EMITTER RESISTOR CONNECTED BETWEEN SAID EMITTER AND THE OTHER OF SAID TERMINALS, (E) MEANS TO RENDER SAID TRANSISTOR ALTERNATELY NONCONDUCTIVE AND CONDUCTIVE, AND (F) MEANS INCLUDING SAID EMITTER RESISTOR TO CAUSE SAID TRANSISTOR TO CONDUCT IN A SATURATED MANNER DURING THE EARLY PART OF CURRENT BUILD UP THROUGH THE TRANSISTOR AND TO LIMIT THE MAXIMUM CURRENT FLOW THERETHROUGH TO A PREDETERMINED OPERATING VALUE.