Power tool and control method thereof

A control method of a power tool comprising a functional element, an electric motor, comprising a stator and a rotor, configured to drive the functional element to rotate, a power supply module configured to supply power to the electric motor, a driver circuit, electrically connected to the electric motor and the power supply module, configured to apply a voltage of the power supply module to the electric motor, a temperature detection device configured to detect a temperature inside the power tool, and a controller, electrically connected to the driver circuit, configured to output a control signal to the driver circuit, the control method comprising:

• when the temperature is higher than or equal to a temperature threshold, controlling the driver circuit in a first control mode so as to cause a voltage of the electric motor to vary in a first wave with a rotor position of the electric motor;
• and
• when the temperature is lower than the temperature threshold, controlling the driver circuit in a second control mode so as to cause the voltage of the electric motor to vary in a second wave with the rotor position of the electric motor;
• wherein the second wave comprises a square wave and a quasi-sine wave that appear alternately.