Patent GB-1459164-A (GB)
Title: Electronic ignition system
IPC: F02P5/155
Filed: 1975-02-21
Abstract: 1459164 Ignition systems MOTOROLA Inc 21 Feb 1975 [7 March 1974] 7377/75 Heading FIB An ignition system includes ignition circuit means connected to an ignition coil 60 and generator means 16 having first and second output terminals 20, 28 and operable to provide an output voltage varying in amplitude from some positive to some negative voltage, the generator means being connected to the ignition circuit means for initiation of the operation thereof. The ignition circuit means includes a first transistor 11 having input output and common electrodes the input of the transistor being connected to the first output terminal 20 of the generator means and biasing means connected to the first transistor to determine the switching voltage at the input of the first transistor, the transistor being rendered conductive upon application at the input electrode of the switching voltage by the generator means to produce an output between the output and common electrodes of the first transistor for operating the ignition circuit means. The ignition circuit means detects substantially the zero crossing point of the generator means and the biasing means establishes in the first transistor 11 a first predetermined current density. The biasing means includes a second transistor 30 having operating characteristics similar to those of the first transistor and having input, output and common electrodes, the input and output electrodes being coupled together causing the transistor to operate effectively as a diode and being coupled to the second output terminal 28 of the generator means, the common electrode of the second transistor being connected to the reference potential (earth) and the biasing means biasing the second transistor into conduction to establish therein a second predetermined current density substantially equal to the first predetermined current density in order to maintain the second output terminal of the generator means at a voltage level substantially the same as the switching voltage needed at the input of the first transistor 11 to maintain the first transistor in a partial state of conduction when the output voltage of the generator means at the first terminal thereof is zero. The switching voltage at the input 18 of the first transistor changes with temperature or supply voltage variations and the second transistor 30 compensates for temperature changes in the first transistor or supply voltage variations to maintain the time of switching of the first transistor at the zero voltage crossing point of the output voltage at the first output terminal of the generator means when the generator is going from a negative to a positive output to ensure operation of the first transistor 11 upon the generator means reaching its zero crossing point despite the temperature changes and the supply voltage variations. The second 30 transistor has a lower dynamic impedance than a conventional diode to maintain a low impedance at the input of the first transistor. Fig.1 (not shown), is a simple schematic diagram of the temperature controlled portion of an ignition circuit of the invention.