BATTERY-DRIVEN VARIABLE SPEED MACHINE TOOL

摘要

PURPOSE:To obtain a battery-driven variable speed machine tool producing no beat noise by using MOSFET as a power controlling element and Schottky barrier diode as a flyback diode. CONSTITUTION:A motor 4 and a power controlling element 2 composed of MOSFET are connected in series with a battery 3. Also, a flyback circuit 5 constituted from a resistance 21 and a flyback diode 22 composed of Schottky barrier diode is connected in parallel with said motor 4. A voltage comparison circuit 7 of a duty ratio control circuit 1 compares an output voltage of a triangular wave generator circuit 6 with a feedback voltage of the motor 4 from a feedback circuit 8 to control an ON-OFF time of the power controlling element 2. In this manner, it is possible to obtain a small-sized battery-driven variable speed machine tool producing no beat noise.