Abstract: A duty ratio control device includes a duty ratio calculation unit and a parameter setting unit. The duty ratio calculation unit, when an acceleration manipulation is performed, calculates a control duty ratio per predetermined timing based on a value of at least one parameter so that a rotation speed of a motor mounted on an electric power tool reaches a target rotation speed corresponding to the acceleration manipulation. The control duty ratio is calculated to be larger as the value of the at least one parameter is larger. The parameter setting unit sets the value of the at least one parameter. The value of the at least one parameter set for a reacceleration manipulation is larger than the value of the at least one parameter set for an initial acceleration manipulation.

Abstract: A power tool comprises a housing, a direct current motor arranged in the housing, a speed reduction mechanism coupled to a shaft of the motor, a tool head driven by the speed reduction mechanism, a first direct current power source, and a switching device. The motor comprises a common brush, a high speed brush and a low speed brush which are in sliding contact with a commutator. The switching device is configured to selectively connect the common brush and the high speed brush with the power source to operate the motor in a high speed mode and to connect the common brush and the low speed brush with the power source to operate the motor in a low speed mode.

Abstract: A driving apparatus for a DC brushless motor of a ceiling fan is provided. By setting at least one coder and one sensor outside the DC brushless motor, the driving apparatus can sense the position of magnetic poles of the motor for driving the motor. Meanwhile, a controller set with the motor stores the rotation speed of the motor before being turned off by detecting the turn-off time of a turn-on/off signal.