Power tool

Patent metadata

Field	Value
Publication number	US-12334845-B2
Application number	US-202318189507-A
Country	US
Kind code	B2
Filing date	Mar 24, 2023
Priority date	Oct 20, 2020
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

A power tool includes a motor, a speed regulation mechanism, a driver circuit, and a control module. The motor includes a stator winding and a rotor. The speed regulation mechanism is at least used for setting a target rotational speed of the motor. The driver circuit is used for delivering electrical energy provided by a power supply device from a direct current bus to the motor, where the driver circuit includes multiple electronic switches connected between the power supply device and the motor. The control module is configured to calculate a voltage vector according to a measured rotational speed of the motor, a phase current of the stator winding, and the target rotational speed and overmodulate the voltage vector to output a pulse-width modulation (PWM) signal to the driver circuit. A per-unit value of an amplitude of the voltage vector ranges from 0 to 1.15.

First claim

What is claimed is:

1. A power tool, comprising:
a motor comprising a stator winding and a rotor rotating around a stator;
a speed regulation mechanism at least used for setting a target rotational speed of the motor;
a driver circuit for delivering electrical energy provided by a power supply device from a direct current bus to the motor, wherein the driver circuit comprises a plurality of electronic switches connected between the power supply device and the motor; and
a control module;
wherein the control module is configured to calculate a voltage vector according to a measured rotational speed of the motor, a phase current of the stator winding, and the target rotational speed and overmodulate the voltage vector to obtain a modulated voltage vector to output a pulse-width modulation (PWM) signal to the driver circuit and a per-unit value of an amplitude of the modulated voltage vector ranges from 0 to 1.15,
wherein the control module comprises a first rotational speed loop for generating a target current of the motor according to the target rotational speed of the motor and an actual rotational speed of the motor,
wherein the control module comprises:
a current distribution unit for distributing a direct-axis target current and a quadrature-axis target current according to the target current of the motor generated by the first rotational speed loop;
a current conversion unit for generating a direct-axis actual current and a quadrature-axis actual current according to an actual current of the motor;
a first current loop for generating a first regulation voltage according to the direct-axis target current and the direct-axis actual current;
a second current loop for generating a second regulation voltage according to the quadrature-axis target current and the quadrature-axis actual current;
a voltage conversion unit for generating a first voltage control quantity and a second voltage control quantity according to the first regulation voltage and the second regulation voltage;
an overmodulation unit configured to perform overmodulation according to the first voltage control quantity and the second voltage control quantity to output a first overmodulated voltage and a second overmodulated voltage; and
a control signal unit for generating control signals according to the first overmodulated voltage and the second overmodulated voltage, and

wherein the control signals are used for controlling switching operations of the plurality of electronic switches of the driver circuit.

2. The power tool of claim 1 , wherein the control module is configured to overmodulate part of the voltage vector exceeding a linear modulation region to obtain the modulated voltage vector to output the PWM signal to the driver circuit, and the per-unit value of the amplitude of the modulated voltage vector ranges from 1 to 1.15.

3. The power tool of claim 1 , further comprising:
a rotational speed detection module for detecting at least one of the measured rotational speed of the motor or a position of the rotor; and
a current detection module for detecting the phase current of each phase of the stator winding.

4. The power tool of claim 3 , wherein the current detection module is configured to acquire internal resistance of an electronic switch turned on and calculate a bus current or the phase current according to the internal resistance of the electronic switch and a voltage value across the electronic switch.

5. The power tool of claim 3 , further comprising a detection resistor connected in series between the driver circuit and the stator winding; wherein the current detection module is configured to calculate a bus current or the phase current according to a voltage across the detection resistor.

6. The power tool of claim 1 , wherein the motor is a three-phase motor, and three-phase input voltages of the motor are at a phase angle of 120° to each other.

7. The power tool of claim 1 , wherein the PWM signal is a discontinuous PWM signal.

8. The power tool of claim 1 , further comprising a temperature detection module for detecting a temperature of the power tool before the motor is started and wherein the control module is configured to overmodulate the voltage vector to obtain the modulated voltage vector to output a first PWM signal to the driver circuit so that the driver circuit drives the motor to start when the temperature is lower than a first temperature threshold.

9. The power tool of claim 8 , wherein the control module is configured to perform common modulation on the voltage vector to obtain the modulated voltage vector to output a second PWM signal to the driver circuit so that the driver circuit drives the motor to start when the temperature is higher than a second temperature threshold.

10. The power tool of claim 9 , wherein the first temperature threshold is less than the second temperature threshold.

11. The power tool of claim 1 , wherein the control module is configured to control switching operations of the plurality of electronic switches at a preset frequency, and the preset frequency ranges from 5 kHz to 40 kHz.

12. The power tool of claim 1 , wherein a voltage waveform of a filtered terminal voltage of the motor comprises at least two peaks in one cycle.

13. A power tool, comprising:
a motor comprising a stator winding and a rotor rotating around a stator;
a speed regulation mechanism at least used for setting a target rotational speed of the motor;
a driver circuit comprising a plurality of electronic switches connected between a power supply device and the motor; and
a control module;
wherein the control module is configured to calculate a voltage vector according to a measured rotational speed of the motor, a phase current of the stator winding, and the target rotational speed and overmodulate the voltage vector to output a pulse-width modulation (PWM) signal to the driver circuit to maintain a phase voltage of the motor at a constant value for a preset time in one electrical cycle,
further comprising a temperature detection module for detecting a temperature of the power tool before the motor is started and wherein the control module is configured to overmodulate the voltage vector to obtain a modulation of the voltage vector to output a first PWM signal to the driver circuit so that the driver circuit drives the motor to start when the temperature is lower than a first temperature threshold.

Assignees

• Nanjing Chervon Ind Co Ltd

Inventors

• Xie Aihua
• Xu Yanqing
• Li Guang
• Li Shuang

Classifications

• H02P29/60

  Controlling or determining the temperature of the motor or of the drive (H02P29/02 takes precedence) · CPC title

• H02P27/085

  wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P21/22 Primary

  Current control, e.g. using a current control loop · CPC title

• H02P27/08 Primary

  with pulse width modulation · CPC title