Capacitor discharge ignition system with microprocessor timing control

Abstract

Capacitor charge ignition system includes a computer chip programmed to control ignition timing of the system. The system has a generator coil and primary and secondary windings of an ignition coil disposed on one leg portion of a ferromagnetic core. The generator coil is wound with respect to ground potential to provide positive pulses, one preceding and one following, in sequence, an intermediate pulse of negative polarity induced in the generator coil in response to rotation of permanent magnet poles past the one core leg. The positive pulses are supplied to a microprocessor which is programmed to determine the elapsed time between the pair of positive pulses and to provide an output signal which is a multiple function of the elapsed time. A capacitor is charged by the intermediate pulse so that its grounded side is changed to a positive polarity voltage which is connected in circuit with the primary winding of the ignition coil and with the anode/cathode path of a silicon controlled rectifier (SCR). An opto-coupler switch is connected to the output signal of the microprocessor, to the control electrode of the SCR and to the capacitor. A minor portion of the positive voltage charge on the capacitor is used to trigger the SCR to its conductive state based on the output generated by the microprocessor. The capacitor is connected to discharge the remainder of its positive charge through the primary winding and the SCR to generate an ignition pulse in the secondary winding of the ignition coil.