| 摘要 |
An ignition timing control circuit for an internal combustion engine of a ring gear tooth counting type includes a throttle sensor for sensing the load condition of the engine and generating an output voltage representative of the sensed load condition, a reference-signal generator for generating a reference signal, a clock pulse generator in the form of a gear-signal pick-up coil for generating clock pulses based on the rotational position of a ring gear, a counter operable to start the counting of the clock pulses generated by the clock pulse generator when the reference-signal generator generates a reference signal, the counter outputting a digitalized output representative of the number of the counted clock pulses, a D/A converter for converting the digitalized output of the counter into an analog voltage having a stepped form, an integrator for integrating and smoothing out the stepped output voltage of the D/A converter, and a comparator for comparing the output voltage of the integrator and the output voltage of the throttle sensor and generating an output signal for controlling the ignition timing of the engine in accordance with the result of comparison. In one embodiment, the integrator has a fixed time constant and comprises a capacitor. In another embodiment, the integrator has a variable time constant and comprises a plurality of capacitors connected to the D/A converter through a switch for changing the total capacitance of the integrator in response to the output of the counter.
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