| 摘要 |
In a device (1) having a variable-speed motor (2), a single switching device (9) has been provided for influencing the speed of the motor and for generating turn-off voltage transients (SP) on a coil terminal (3b) of the motor. The turn-off voltage transients can be applied to a voltage boosting circuit (14) for generating a d.c. control voltage required for driving a control electrode of the single switching device. This d.c. control voltage is supplied to the control electrode of the switching device with the aid of a control pulse generator (10). The d.c. control voltage reaches a higher value than the d.c. supply voltage (V) applied to the device (1). Preferably, the device includes a starting circuit (20), by which a minimum d.c. control voltage, required for the control electrode of the single switching device, can be generated for the first time in order to drive the single switching device into its conductive state.
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