| 摘要 |
An ignition apparatus for an engine reduces the duty cycle of a power transistor circuit for controlling the primary winding current of an ignition coil over the entire operating range of the engine including low and high speeds. In one embodiment, a signal generator generates an alternating output signal which is fed through a resistor to a wave form shaper for comparison with a threshold voltage. As long as the signal generator output is higher than the threshold voltage, the wave form shaper generates an output pulse for controlling a conduction time of the power transistor circuit. When the engine is operating at low speeds, the pulse width of the wave form shaper output is reduced by partially absorbing the signal generator output by a current absorbing circuit which is disabled at high engine speeds. In another embodiment, at high engine speeds, a DC current is supplied from a DC power source to a signal generator via a resistor through a current supply circuit which is disabled by a switching transistor at low enging speeds. In both of the embodiments, the signal generator has one end connected to ground and the other end connected at a single external connection point with the wave form shaper through the resistor.
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