Electric tool and motor drive system

1. A motor drive system comprising:

an inverter coupled to a power supply comprising a plurality of semiconductor switch elements and configured to convert a voltage provided by the power supply into alternating current power to power an electric motor;

a motor drive control circuit configured to output a drive signal to control a power mode of the semiconductor switch elements in the inverter;

a trigger switch;

a first electronic switch connected between the power supply and the motor drive control circuit, when the first electronic switch is turned on, the power supply supplies power to the motor drive control circuit to drive the electric motor; and

a switch control circuit comprising a second electronic switch, a control terminal of the second electronic switch coupled to the trigger switch and a first terminal of the second electronic switch coupled to a control terminal of the first electronic switch, the switch control circuit configured to turn on or turn off the first electronic switch based on a state of the trigger switch.

2. The motor drive system according to claim 1 , wherein the switch control circuit further comprises a delay unit connected between a control terminal of the second electronic switch and the trigger switch and configured to delay to turn off the first electronic switch for a delay time since the trigger switch is turned off.

3. The motor drive system according to claim 2 , wherein the motor drive control circuit comprises a microcontroller configured to detect the state of the trigger switch and control the motor to brake during the delay time.

4. The motor drive system according to claim 2 , wherein the switch control circuit further comprises a diode, a cathode of the diode is coupled to the control terminal of the second electronic switch through the delay unit, an anode of the diode is coupled to the power supply through the trigger switch, the first terminal of the second electronic switch is coupled to the control terminal of the first electronic switch through a first resistor, the control terminal of the first electronic switch is coupled to the power supply through a second resistor, a first terminal of the first electronic switch is coupled to the power supply, a second terminal of the first electronic switch is coupled to the motor drive control circuit, and the control terminal of the second electronic switch is coupled to the second terminal of the second electronic switch through a third resistor.

5. The motor drive system according to claim 4 , wherein the delay unit comprises a capacitor and a fourth resistor, the fourth resistor is connected between the cathode of the diode and the control terminal of the second electronic switch, and the capacitor is connected between the cathode of the diode and ground.

6. The motor drive system according to claim 1 , wherein a rated current of the trigger switch is lower than 100 milliamperes.

7. A motor drive system comprising a trigger switch, a first electronic switch, and a switch control circuit, wherein

the trigger switch is connected in series to a power supply;

the first electronic switch is configured to control a motor to be powered on or powered off; and

the switch control circuit comprises a second electronic switch, a control terminal of the second electronic switch coupled to the trigger switch and a first terminal of the second electronic switch coupled to a control terminal of the first electronic switch, the switch control circuit is configured to control the first electronic switch based on a state of the trigger switch, wherein the first electronic switch is delayed to be turned off after the trigger switch is turned off to control the motor to be powered off later than a time that the trigger switch is turned off.

8. The motor drive system according to claim 7 , wherein the trigger switch and the motor are arranged in two different current branches respectively, and a current flowing through the trigger switch is lower than an operating current of the motor while the motor drive system is powered to operate.

9. The motor drive system according to claim 8 , wherein the current flowing through the trigger switch is lower than one percent of the operating current of the motor while the motor drive system is powered to operate.

10. The motor drive system according to claim 9 , wherein the motor drive system further comprises a microcontroller, and the first electronic switch is connected in series between the power supply and the microcontroller.

11. The motor drive system according to claim 7 , wherein the trigger switch is a switch operable by a user manually.

12. An electric tool, comprising a housing, a working head extending out from the housing, a motor for driving the working head, and the motor drive system according to claim 1 .

13. The electric tool according to claim 12 , wherein the electric tool is one of an electric drill, an electric screwdriver, a hand mill and an electric saw.

14. The motor drive system according to claim 1 , wherein the switch control circuit further comprises a delay unit, the delay unit comprises a capacitor and a resistor, the resistor is connected between the trigger switch and the control terminal of the second electronic switch, the control terminal of the second electronic switch is connected to the ground through the resistor and the capacitor in series.

15. The motor drive system according to claim 7 , wherein the switch control circuit further comprises a capacitor and a resistor, the resistor is connected between the trigger switch and the control terminal of the second electronic switch, the control terminal of the second electronic switch is connected to the ground through the resistor and the capacitor in series.