| 摘要 |
A device for controlling variable speed electric motors, particularly for hand held power tools and other miniaturised electrically powered apparatuses, comprises an electronic driver unit ( 5 ) connectable to the terminals ( 2, 3 ) of an electric power source for supplying electric current to at least one electric motor (M) and an optical switch device ( 7 ) for triggering the electronic driver unit ( 5 ). The optical switch device ( 7 ) comprises light emitting means ( 8 ) and light transducer means ( 9 ) for detecting and converting light into an electric variable signal. The light transducer means ( 9 ) are operatively connected to the electronic driver unit ( 5 ) for controlling the electric motor (M). The light emitter means ( 8 ) comprise at least one white light, high brightness LED (D 1 , D 2 ) connected in parallel to the electric power line terminals ( 2, 3 ) by means of a miniaturised power circuit. The miniaturised power circuit comprises at least one resistor (R 2 ) when said at least one electric motor (M) is a DC motor, and a capacitive phase displacement power supply (C, R 2 ) when said electric motor is an AC motor. The capacitive phase displacement power supply (C, R 2 ) comprises at least one capacitor (C) and an input resistor (R 2 ) adapted to supply said diodes (D 1 , D 2 ) with a threshold voltage.
|
