TIMING CIRCUIT FOR PROVIDING AN OUTPUT SIGNAL THE DURATION OF WHICH REMAINS A FIXED PERCENTAGE OF THE PERIOD OF AN INPUT SIGNAL

摘要

1533093 Ignition systems MOTOROLA Inc 17 Jan 1977 [27 Feb 1976] 01784/77 Heading F1B [Also in Division H3] A solid state ignition system has sinusoidal signals derived from an engine are applied to the comparator 84, and then to a timing circuit 86 which produces an output pulse which has a constant mark-to-space ratio as the input frequency varies. This pulse which goes high to low as the sine signals cross zero in a positive direction is applied to integrators 88, 90, and thence to a comparator 92. In operation the gate 94 is inhibited during the mark period thus preventing ignition if noise is present. The output of integrator 90 falls and eventually passes through the level at the output of 88, NOR gate 94 is then enabled and current starts to flow through the saturated amplifier 96 into the ignition coil 100 and this results in a rising voltage across sensing resistor 98 which applied to a comparator 102, and so to the NOR gate, stops the current and resets the integrator 88. The output of integrator 88 is varied in response to the engine r.p.m. to regulate the dwell time to be a fixed percentage of the total firing cycle.