Electric tool and power management circuit

An electric tool is powered by a battery. An electric tool includes a motor, a charging and discharging control circuit and a motor control circuit. Charging and discharging control circuit is configured to couple to a power adapter. Charging and discharging control circuit includes a direct power supply path connected to the power adapter and battery, and is configured to detect an input current from power adapter and a first load current flowing to battery and to calculate an upper limit of a second load current that can be provided to motor according to a difference between the input current and the first load current. Motor control circuit is coupled between charging and discharging control circuit and motor, and is configured to control a speed or a torque of motor according to the upper limit of second load current.