Patent ID: 7518837
Filing Date: 2009-04-14
Classification: H02H,H02P

Abstract:
1. A control device for soft starting and protecting overload of a motor in a power tool, comprising: a power switch; a varistor; a motor; a microcontroller; a transistor; a triac; a relay; a diode; a Zener diode; multiple resistors; and multiple capacitors, wherein when the power switch is turned on, the varistor restrains instantaneous surge generated by a main power, a sine wave signal of main power passes through the diode to generate rectified half-wave signal, the resistors restrain current, and the zener diode restrains voltage such that voltage is reduced and supplied to the microcontroller, the microcontroller sends a control signal through triac to soft start a voltage supply and increase a value of the voltage supply smoothly such that the motor rotates evenly from a low speed to a high speed.