Breakerless ignition system with electronic advance

摘要

A magneto ignition system includes a rotating magnet driven past a primary winding for firing the engine. The magneto generates a speed dependent signal having a following current pulse and a leading current pulse of a smaller amplitude than the following pulse. A Darlington power transistor has a collector connected in series with a voltage dropping resistor or diode to the winding. A resistor bias circuit connects the primary winding to the input of the power transistor. A cut-off transistor is connected to by-pass the bias circuit of the Darlington power transistor and thereby generate a pulse in the primary winding. A timing capacitor is connected to the primary winding in series with a diode and charging resistor. A control transistor has its input circuit connected between the timing capacitor and the resistors of the bias circuit. The control transistor responds to the differential of the bias circuit voltage and the capacitor voltage, whereby the control transistor drives the cut-off transistor to turn off the power transistor during the decreasing side of the winding circuit after it peaks at starting and low speeds and progressively increases with a gradual advance during the starting speed range, and includes a maximum advance established prior to the peak current value.