US 7,518,837 B2
Control device for soft starting and protecting overload of motor
Tai-Yuan Tseng, Taipei (Taiwan); and Mu-Hsien Huang, Taipei (Taiwan)
Assigned to Uan Chung Enterprises Co., Ltd, Taipei (Taiwan)
Filed on Sep. 21, 2006, as Appl. No. 11/533,875.
Prior Publication US 2008/0074811 A1, Mar. 27, 2008
Int. Cl. H02H 7/08 (2006.01)
U.S. Cl. 361—29  [361/23; 361/30; 361/31; 318/430; 318/751; 318/775; 318/778] 19 Claims
OG exemplary drawing
 
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.