Power tool, detection circuit and detection method of load state of power tool

A detection method of a load state of a power tool, comprising:

• obtaining a load current of the power tool by detecting a voltage across a sampling resistor,
• determining the load state of the power tool according to an obtained magnitude of the load current of the power tool, and
• determining duration time of a current load state of the power tool, when the duration time of the current load state of the power tool is greater than or equal to a preset time, controlling an alarm display unit to execute a preset display state corresponding to the current load state of the power tool;
• wherein, the power tool comprises a main control unit, an RC filter circuit and a bias circuit connected with the main control unit, an operational feedback amplifier circuit, connected with the RC filter circuit, and a capacitor C3 arranged between the bias circuit and the operational feedback amplifier circuit, a generated voltage is amplified by the main control unit and the operational feedback amplifier circuit, then is connected to an I/O port of the main control unit via the RC filter circuit to be processed.

A power tool, comprising:

• a body;
• a motor and a motor driving unit, arranged on the body;
• and
• a detection circuit of a load state of the power tool, arranged on the body, wherein
• the detection circuit of the load state of the power tool comprises:
• a main control unit, comprising an operational amplifier,
• a sampling resistor, arranged on a driving loop of the motor,
• a voltage sampling unit, configured to sample a voltage across the sampling resistor,
• an alarm display unit, connected with the main control unit,
• an RC filter circuit, one end of the RC filter circuit being connected with an I/O port of the main control unit,
• a bias circuit, connected with the main control unit, a first end of the bias circuit being connected with a positive end of the operational amplifier, and a second end of the bias circuit being connected with the sampling resistor,
• an operational feedback amplifier circuit, connected with the RC filter circuit, and
• a capacitor C3, connected between the bias circuit and the operational feedback amplifier circuit and connected with a negative end of the operational amplifier, wherein
• one end of the sampling resistor is connected with the operational feedback amplifier circuit, and the operational amplifier in sequence,
• the main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor collected by the voltage sampling unit.