Power tool and control method thereof
A power tool includes: a functional element; an electric motor including a stator and a rotor and 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 and configured to apply a voltage of the power supply module to the electric motor; and a controller electrically connected to the driver circuit and configured to output a control signal to the driver circuit. The controller is configured to, when the electric motor is overloaded, adjust a current limit value supplied to the electric motor and control the driver circuit in a first control mode, so as to cause a voltage of the electric motor to vary in a quasi-sine wave with a rotor position of the electric motor.
1 . 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, when the temperature is higher than or equal to a temperature threshold, control 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, control 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.
2 . The power tool according to claim 1 , wherein the quasi-sine wave comprises at least one of a sine wave and a saddle wave.
3 . The power tool according to claim 1 , wherein the controller is further configured to, when the temperature is lower than the temperature threshold and a duty cycle of the control signal is less than a duty cycle threshold, control the driver circuit in the first control mode.
4 . The power tool according to claim 1 , wherein the controller is further configured to, when the temperature is lower than the temperature threshold and a duty cycle of the control signal is greater than or equal to a duty cycle threshold, control the driver circuit in a third control mode so as to cause the voltage of the electric motor to vary in the quasi-sine wave with the position of the rotor of the electric motor.
5 . The power tool according to claim 1 , wherein the electric motor is a sensorless motor.
6 . 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.
7 . The control method according to claim 6 , wherein the quasi-sine wave comprises at least one of a sine wave and a saddle wave.
8 . The control method according to claim 6 , further comprising: when the temperature is lower than the temperature threshold and a duty cycle of the control signal is less than a duty cycle threshold, controlling the driver circuit in the first control mode.
9 . The control method according to claim 6 , further comprising: when the temperature is lower than the temperature threshold and a duty cycle of the control signal is greater than or equal to a duty cycle threshold, controlling the driver circuit in a third control mode so as to cause the voltage of the electric motor to vary in the quasi-sine wave with the position of the rotor of the electric motor.