| 摘要 |
A damping circuit for a DC motor. Driving the motor is a half-wave rectified current from an AC power source. A transistor and isolating diode are connected across the motor terminals. The base of the transistor is connected through a resistor to the output of the AC power source so that during the half cycles the motor is not driven the transistor is turned on to short-circuit the back voltage from the motor due to armature rotation. The drag produced on the armature is proportional to its rotational velocity and therefore equivalent to hydraulic damping but less expensive and simpler. One such transistor circuit is used for each of the two directions of motor travel in a servo system such as used in automatic focusing projectors.
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