A power modulation system, a brushless power tool and its control method, and a brushless motor control system and its control method.

Abstract

This invention proposes a power modulation system, comprising: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first input terminal and the second input terminal are used to connect to an AC power grid, and the rectifier unit is used to convert AC power into DC power; a power factor correction unit connected in parallel between the first output terminal and the second output terminal; the power factor correction unit having a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element, wherein the first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal; and the first diode element is connected in series between the first capacitor element and the second capacitor element. The power modulation system proposed in this invention effectively improves the power factor when the brushless motor is running at high speed, and ensures output torque and reduces motor copper losses when the brushless motor is running at low speed.

Description

Technical Field

[0001] This invention relates to a power modulation method, and more particularly to a power modulation method for a brushless power tool and a control method for a brushless motor. Background Technology

[0002] The power supply system of high-voltage brushless power tools uses a rectifier bridge to rectify and filter the AC power before supplying it to the permanent magnet brushless motor. The rectifier bridge converts one cycle of sinusoidal AC power into two half-wave DC power, and then the filter capacitor filters the half-wave DC power into DC power of approximately equal amplitude, which is then transmitted to the brushless motor as the power supply voltage.

[0003] Currently, traditional high-voltage brushless power tool power supply systems use a filter capacitor connected in parallel at the rear end of the rectifier bridge to filter the two half-wave DC currents into near-equal amplitude DC currents. However, the design of the filter capacitor at the rear end of the rectifier bridge is one of the challenges in power modulation systems. If the capacitance of the filter capacitor at the rear end of the rectifier bridge is very large, although the motor can run at full load at any time, with high output and efficiency, this large capacitor causes the current output by the rectifier bridge to be a large spike current injected into the capacitor. This results in a very low power factor for the entire high-voltage brushless power tool's power system, adversely affecting the power grid and making it difficult for the tool to meet electromagnetic compatibility safety requirements. If the capacitance of the filter capacitor at the rear end of the rectifier bridge is very small, the voltage input to the motor is close to the two half-waves, with large amplitude oscillations. That is, when the half-wave voltage is high, the motor runs at full load, but when the half-wave voltage is low, the motor output is low and the efficiency is low. In fact, when the back EMF at the current operating speed of the motor is higher than the half-wave voltage, the motor stops outputting power.

[0004] In a circuit, a capacitor acts as an energy storage device. Connecting a capacitor alters the phase difference between voltage and current, thus affecting the circuit's power factor. A lower power factor results in reactive power being generated. A higher power factor indicates higher energy utilization and better power quality. This is because a higher power factor means greater actual power and relatively smaller apparent power, i.e., less useless power (such as reactive power) in the circuit. This allows circuits and equipment to operate more efficiently, reducing energy waste and improving energy efficiency. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to improve the power factor of high-voltage brushless power tools in a low-cost and effective manner.

[0006] To address the aforementioned problems, this invention proposes a power modulation system, comprising: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first input terminal and the second input terminal are connected to an AC power grid, and the rectifier unit is used to convert AC power into DC power; a power factor correction unit connected in parallel between the first output terminal and the second output terminal; the power factor correction unit having a first capacitor element, a second capacitor element, a first diode element, a first switching element, and a second switching element, wherein the first capacitor element and the first switching element are connected in series and in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switching element are connected in series and in parallel between the first output terminal and the second output terminal; and the first diode element is connected in series between the first capacitor element and the second capacitor element. The power modulation system proposed in this invention effectively improves the power factor when the brushless motor is running at high speed, and ensures output torque and reduces motor copper losses when the brushless motor is running at low speed.

[0007] Furthermore, the capacitance value of the first capacitor element is equal to the capacitance value of the second capacitor element.

[0008] Furthermore, the power correction unit also has a second diode element, the first switching element has a first terminal and a second terminal, and the second diode element is connected in parallel between the first terminal and the second terminal of the first switching element.

[0009] Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the off state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the on state.

[0010] Furthermore, the first capacitor element has a positive terminal and a negative terminal, the second capacitor element has a positive terminal and a negative terminal, the first diode element has a positive terminal and a negative terminal, the positive terminal of the first capacitor element is connected to the first output terminal, the negative terminal of the first capacitor element is connected to one end of the first switching element, the other end of the first switching element is connected to the second output terminal, the negative terminal of the second capacitor element is connected to the second output terminal, the positive terminal of the second capacitor element is connected to one end of the second switching element, the other end of the second switching element is connected to the first output terminal, the positive terminal of the first diode element is connected to the negative terminal of the first capacitor element, and the negative terminal of the first diode element is connected to the positive terminal of the first capacitor element.

[0011] Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in an open or closed state based on the sinusoidal power grid angle. When the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

[0012] Furthermore, it also includes a third capacitor element, which is connected in parallel between the first output terminal and the second output terminal.

[0013] This invention also proposes a brushless power tool, comprising: a brushless motor with a position sensing unit; a power modulation system for providing DC power to the brushless motor; a control unit for providing control signals to control the brushless motor; a motor drive unit for receiving control signals from the control unit and sending drive signals to drive the brushless motor based on the control signals; and a motor switching unit for receiving drive signals from the motor drive unit and switching the connection between the power modulation system and the brushless motor. The power modulation system includes: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first input terminal and the second input terminal are used for... The rectifier unit, connected to the AC power grid, converts AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal. The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element. The first capacitor element and the first switch element are connected in series and in parallel between the first output terminal and the second output terminal. The second capacitor element and the second switch element are connected in series and in parallel between the first output terminal and the second output terminal. The first diode element is connected in series between the first capacitor element and the second capacitor element.

[0014] Furthermore, the power correction unit also has a second diode element, the first switching element has a first terminal and a second terminal, and the second diode element is connected in parallel between the first terminal and the second terminal of the first switching element.

[0015] Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the on state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the off state.

[0016] Furthermore, the brushless motor has a first operating state and a second operating state. When the brushless motor is in the first operating state, the power factor correction unit is in a first connected state; when the brushless motor is in the second operating state, the power factor correction unit is in a second connected state. The operating mode of the power modulation system is switched based on the operating state of the brushless motor, resulting in smaller phase current glitches during low-speed, high-torque operation to ensure output torque and reduce motor copper losses, and a high power factor during high-speed, high-power operation.

[0017] Furthermore, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0018] Furthermore, the first capacitor element has a positive terminal and a negative terminal, the second capacitor element has a positive terminal and a negative terminal, the first diode element has a positive terminal and a negative terminal, the positive terminal of the first capacitor element is connected to the first output terminal, the negative terminal of the first capacitor element is connected to one end of the first switching element, the other end of the first switching element is connected to the second output terminal, the negative terminal of the second capacitor element is connected to the second output terminal, the positive terminal of the second capacitor element is connected to one end of the second switching element, the other end of the second switching element is connected to the first output terminal, the positive terminal of the first diode element is connected to the negative terminal of the first capacitor element, and the negative terminal of the first diode element is connected to the positive terminal of the first capacitor element.

[0019] Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in an open or closed state based on the sinusoidal power grid angle. When the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

[0020] Furthermore, the capacitance value of the first capacitor element is equal to the capacitance value of the second capacitor element.

[0021] Furthermore, the control unit is also used to control the first switching element and the second switching element.

[0022] This invention also proposes a control method for a brushless power tool. The brushless power tool includes: a brushless motor and a power modulation system for providing DC power to the brushless motor; the power modulation system includes: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, the first input terminal and the second input terminal being used to connect to an AC power grid, the rectifier unit being used to convert AC power into DC power; a power factor correction unit connected in parallel between the first output terminal and the second output terminal; the power factor correction unit having a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element, the first capacitor element and the first switch element being connected in series and connected in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switch element being connected in series and connected in parallel between the first output terminal and the second output terminal; the first diode element being connected in series between the first capacitor element and the second capacitor element; the control method for the brushless power tool includes: when the brushless motor is in a first operating state, the first switch element and the second switch element can be disconnected; when the brushless motor is in a second operating state, the first switch element and the second switch element are turned on. The operating mode of the power modulation system based on the operating state switching of the brushless motor enables the brushless motor to have smaller phase current glitch when running at low speed and high torque, thereby ensuring output torque and reducing motor copper loss, and to have a high power factor when running at high speed and high power.

[0023] Furthermore, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0024] This invention also proposes a brushless motor control system, comprising: a power modulation system for providing DC power to the brushless motor; a control unit for providing control signals to control the brushless motor; a motor drive unit for receiving control signals from the control unit and sending drive signals to drive the brushless motor based on the control signals; and a motor switching unit for receiving drive signals from the motor drive unit and switching the connection between the power modulation system and the brushless motor. The power modulation system includes: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, the first input terminal and the second input terminal being connected to an AC power grid, the rectifier unit being used to convert AC power into DC power; and a power factor correction unit connected in parallel between the first output terminal and the second output terminal. The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element, the first capacitor element and the first switch element being connected in series and in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switch element being connected in series and in parallel between the first output terminal and the second output terminal; and the first diode element being connected in series between the first capacitor element and the second capacitor element.

[0025] Furthermore, the power correction unit also includes a second diode element, and the first switching element has a first terminal and a second terminal, with the second diode element connected in parallel between the first terminal and the second terminal of the first switching element. Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are either in an open or closed state based on the sinusoidal power grid angle; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

[0026] Furthermore, the power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the on state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the off state.

[0027] Furthermore, the first capacitor element has a positive terminal and a negative terminal, the second capacitor element has a positive terminal and a negative terminal, the first diode element has a positive terminal and a negative terminal, the positive terminal of the first capacitor element is connected to the first output terminal, the negative terminal of the first capacitor element is connected to one end of the first switching element, the other end of the first switching element is connected to the second output terminal, the negative terminal of the second capacitor element is connected to the second output terminal, the positive terminal of the second capacitor element is connected to one end of the second switching element, the other end of the second switching element is connected to the first output terminal, the positive terminal of the first diode element is connected to the negative terminal of the first capacitor element, and the negative terminal of the first diode element is connected to the positive terminal of the first capacitor element.

[0028] Furthermore, the control unit is also used to control the first switching element and the second switching element.

[0029] This invention also proposes a control method for a brushless motor control system. The brushless motor control system includes: a power modulation system for providing DC power to the brushless motor; the power modulation system includes: a rectifier unit having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, the first input terminal and the second input terminal being connected to an AC power grid, the rectifier unit being used to convert AC power into DC power; a power factor correction unit connected in parallel between the first output terminal and the second output terminal; the power factor correction unit having a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element, the first capacitor element and the first switch element being connected in series and connected in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switch element being connected in series and connected in parallel between the first output terminal and the second output terminal; the first diode element being connected in series between the first capacitor element and the second capacitor element; the control method includes: when the brushless motor is in a first operating state, the first switch element and the second switch element can be disconnected; when the brushless motor is in a second operating state, the first switch element and the second switch element are turned on. The operating mode of the power modulation system based on the operating state switching of the brushless motor enables the brushless motor to have smaller phase current glitch when running at low speed and high torque, thereby ensuring output torque and reducing motor copper loss, and to have a high power factor when running at high speed and high power.

[0030] Furthermore, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0031] The power modulation system, brushless power tool and its control method, and brushless motor control system and its control method proposed in this invention not only effectively improve the power factor, but also further improve the power modulation system's working mode by switching the operating mode of the brushless motor based on the operating state of the brushless motor. This allows the brushless motor to have smaller phase current glitches when running at low speed, thereby ensuring output torque, reducing motor copper losses, and having a high power factor when running at high speed. Attached Figure Description

[0032] The invention will now be further described and explained with reference to the accompanying drawings.

[0033] Figure 1 This is a system circuit block diagram of a high-voltage brushless electric tool according to one embodiment of the present invention.

[0034] Figure 2 This is a system circuit block diagram of a high-voltage brushless electric tool according to one embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a power modulation system circuit according to one embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of a power modulation system circuit according to another embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of a power modulation system circuit according to another embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of a power modulation system circuit according to another embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of a brushless motor according to one embodiment of the present invention.

[0040] Figure 8 This is a schematic diagram of the back electromotive force of a brushless motor according to one embodiment of the present invention.

[0041] Figure 9 yes Figure 7 The diagram shows a comparison of current when the brushless motor is running at low speed and high torque.

[0042] Figure 10 yes Figure 7 The diagram shows a voltage comparison of a brushless motor operating at low speed and high torque.

[0043] Figure 11 yes Figure 7 The diagram shows a comparison of phase currents when the brushless motor is running at high speed and high power.

[0044] Figure 12 yes Figure 7The diagram shows a comparison of the output current of the rectifier unit when the brushless motor is running at high speed and high power.

[0045] Figure 13 yes Figure 7 The diagram shows a comparison of the power factor of the power modulation system for the brushless motor.

[0046] Figure 14 yes Figure 7 The diagram shows a comparison of the copper losses of a brushless motor. Detailed Implementation

[0047] The technical solution of the present invention will be more clearly and completely explained below with reference to the accompanying drawings and through the description of preferred embodiments of the present invention.

[0048] Some embodiments of the present invention are as follows: Figures 1-2 As shown, the power modulation system 10 includes: a rectifier unit 11 having a first input terminal 11A, a second input terminal 11B, a first output terminal 11C, and a second output terminal 11D; the first input terminal 11A and the second input terminal 11B are used to connect to the AC power grid, and the rectifier unit 11 is used to convert AC power into DC power; a power factor correction unit 12 connected in parallel between the first output terminal 11C and the second output terminal 11D; the power factor correction unit 12 has a first capacitor element 121, a second capacitor element 122, a first diode element 123, a first switch element 124, and a second switch element 125; the first capacitor element 121 and the first switch element 124 are connected in series and connected in parallel between the first output terminal 11C and the second output terminal 11D; the second capacitor element 122 and the second switch element 125 are connected in series and connected in parallel between the first output terminal 11C and the second output terminal 11D; the first diode element 123 is connected in series between the first capacitor element 121 and the second capacitor element 122. The power modulation system proposed in this invention effectively improves the power factor and has low cost.

[0049] In some of these implementations, such as Figure 2 As shown, the power factor correction unit 12 has a first connection state and a second connection state. When the power factor correction unit 12 is in the first connection state, the first switching element 124 and the second switching element 125 are in the off state; when the power factor correction unit 12 is in the second connection state, the first switching element 124 and the second switching element 125 are in the on state. This allows the connection state of the power factor correction unit 12 to be selected based on different operating states of the brushless motor, thereby improving the power factor when the brushless motor is running at high speed and reducing torque ripple when the brushless motor is running at low speed, thus ensuring output torque and reducing motor copper losses.

[0050] In some implementations such as Figures 5-6As shown, the first capacitor element 121 has a positive terminal and a negative terminal, the second capacitor element 122 has a positive terminal and a negative terminal, the first diode element 123 has a positive terminal and a negative terminal, the positive terminal of the first capacitor element 121 is connected to the first output terminal 11C, the negative terminal of the first capacitor element 121 is connected to one end of the first switching element 124, the other end of the first switching element 124 is connected to the second output terminal 11D, the negative terminal of the second capacitor element 122 is connected to the second output terminal 11D, the positive terminal of the second capacitor element 122 is connected to one end of the second switching element 125, the other end of the second switching element 125 is connected to the first output terminal 11C, the positive terminal of the first diode element 123 is connected to the negative terminal of the first capacitor element 121, and the negative terminal of the first diode element 123 is connected to the positive terminal of the first capacitor element 121.

[0051] In some alternative embodiments, the first switching element 124 has a control terminal 124A and the second switching element 125 has a control terminal 125A. The first switching element 124 and the second switching element 125 are turned on and off respectively by inputting a high level or a low level to the control terminal 124A or the control terminal 125A respectively.

[0052] In some alternative embodiments, the first switching element 124 or the second switching element 125 may also be driven by a switch driving unit. For example... Figure 5 In some of the embodiments shown, the second switching element 125 is driven and controlled to be turned on or off by the switch driving unit 126.

[0053] In the above embodiments, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 may be equal or unequal. Preferably, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 are similar or equal.

[0054] In some of these implementations, such as Figure 2 , Figures 3-4 As shown, the power correction unit 12 also includes a second diode element 127, and the first switching element 124 has a first terminal and a second terminal. The second diode element 127 is connected in parallel between the first terminal and the second terminal of the second switching element 125. Furthermore, this achieves control optimization of the power modulation system. In this case, it is not necessary to control the first switching element 124 and the second switching element 125 to be in a conducting or disconnected state according to the angle of the sinusoidal power grid; it is only necessary to control the first switching element 124 and the second switching element 125 to always be disconnected.

[0055] In some embodiments, the power modulation system 10 further includes a third capacitor element 13, which is connected in parallel between the first output terminal 11C and the second output terminal 11D to achieve high-frequency filtering.

[0056] In one specific implementation, such as Figure 1 , Figure 5 or Figure 6 As shown, when the brushless motor is running at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the on state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, which can effectively increase the torque output of the power supply load. When the brushless motor is running at high speed, when the angle of the sine wave grid is 150 degrees and 330 degrees, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the on state, and the first capacitor element 121 and the second capacitor element 122 are discharged in parallel. When the angle of the sine wave grid is 180 degrees and 360 degrees, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the off state, and the first capacitor element 121 and the second capacitor element 122 are charged in series. The power modulation system operates in power factor compensation mode, and the power factor of the power modulation system is improved. In this embodiment, the first capacitor element 121 and the second capacitor element 122 are selected as capacitors of the same specification, with a capacitance value of 22uF to 440uF. In some optional embodiments, the first capacitor element 121 and the second capacitor element 122 are 47uF, 68uF, 82uF, or 150uF, etc., with a withstand voltage of 400V / 450V. The third capacitor is a CBB capacitor with a capacitance value of less than 10uF. In some optional embodiments, the third capacitor has a capacitance value of 2.2uF and a withstand voltage of 450V. Of course, for those skilled in the art, other capacitance values ​​or withstand voltage values ​​that meet the requirements are also possible, and will not be elaborated here.

[0057] In another specific implementation, such as Figures 2-4As shown, when the brushless motor operates at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the ON state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, effectively increasing the torque output of the powered load. When the brushless motor operates at high speed, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the OFF state, and the first capacitor element 121 and the second capacitor element 122 are charged in series and discharged in parallel. The power modulation system operates in power factor compensation mode, improving the power factor of the power modulation system. Specifically, the first capacitor element 121 and the second capacitor element 122 are selected with the same specifications, with a capacitance value of 22uF to 440uF. In some optional embodiments, the first capacitor element 121 and the second capacitor element 122 are 47uF, 68uF, 82uF, or 150uF, etc., with a withstand voltage of 400V / 450V. The third capacitor is a CBB capacitor with a capacitance less than 10uF. In some optional embodiments, the third capacitor has a capacitance of 2.2uF and a voltage rating of 450V. Of course, other capacitance values ​​or voltage ratings that meet the requirements will be available to those skilled in the art, and will not be elaborated upon here.

[0058] Other embodiments of the present invention are as follows: Figures 1-2As shown, a brushless power tool includes: a brushless motor 20 with a position sensing unit 21; a power modulation system 10 for providing DC power to the brushless motor 20; a control unit 30 for providing control signals to control the brushless motor 10; a motor drive unit 22 for receiving control signals from the control unit 30 and sending drive signals to drive the brushless motor 20 based on the control signals; and a motor switching unit 23 for receiving drive signals from the motor drive unit 22 and switching the connection between the power modulation system 10 and the brushless motor 20. The power modulation system 10 includes: a rectifier unit 11 having a first input terminal 11A, a second input terminal 11B, a first output terminal 11C, and a second output terminal 11D, wherein the first input terminal 11A and the second input terminal 11B are used to connect to... An AC power grid is used, and a rectifier unit 11 converts AC power into DC power. A power factor correction unit 12 is connected in parallel between a first output terminal 11C and a second output terminal 11D. The power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, a first switch element 124, and a second switch element 125. The first capacitor element 121 and the first switch element 124 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D. The second capacitor element 122 and the second switch element 124 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D. The first diode element 123 is connected in series between the first capacitor element 121 and the second capacitor element 122. The brushless motor power modulation system in this embodiment effectively improves the power factor and has low cost.

[0059] In some implementations, such as Figure 2 As shown, the power factor correction unit 12 has a first connection state and a second connection state. When the power factor correction unit 12 is in the first connection state, the first switching element 124 and the second switching element 125 are in the off state; when the power factor correction unit 12 is in the second connection state, the first switching element 124 and the second switching element 125 are in the on state. This allows the connection state of the power factor correction unit 12 to be selected based on different operating states of the brushless motor, thereby improving the power factor when the brushless motor is running at high speed and reducing torque ripple when the brushless motor is running at low speed, thus ensuring output torque and reducing motor copper losses.

[0060] In some implementations such as Figure 1 , Figures 5-6As shown, the first capacitor element 121 has a positive terminal and a negative terminal, the second capacitor element 122 has a positive terminal and a negative terminal, the first diode element 123 has a positive terminal and a negative terminal, the positive terminal of the first capacitor element 121 is connected to the first output terminal 11C, the negative terminal of the first capacitor element 121 is connected to one end of the first switching element 124, the other end of the first switching element 124 is connected to the second output terminal 11D, the negative terminal of the second capacitor element 122 is connected to the second output terminal 11D, the positive terminal of the second capacitor element 122 is connected to one end of the second switching element 125, the other end of the second switching element 125 is connected to the first output terminal 11C, the positive terminal of the first diode element 123 is connected to the negative terminal of the first capacitor element 121, and the negative terminal of the first diode element 123 is connected to the positive terminal of the first capacitor element 121.

[0061] In some alternative embodiments, the first switching element 124 has a control terminal 124A and the second switching element 125 has a control terminal 125A. The first switching element 124 and the second switching element 125 are turned on and off respectively by inputting a high level or a low level to the control terminal 124A or the control terminal 125A respectively.

[0062] In some alternative embodiments, the first switching element 124 or the second switching element 125 may also be driven by a switch driving unit. For example... Figure 5 In some of the embodiments shown, the second switching element 125 is driven and controlled to be turned on or off by the switch driving unit 126.

[0063] In the above embodiments, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 may be equal or unequal. Preferably, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 are similar or equal.

[0064] In some of these implementations, such as Figures 2-4 As shown, the power correction unit 12 also includes a second diode element 127, and a second switching element 125 having a first terminal and a second terminal. The second diode element 127 is connected in parallel between the first terminal and the second terminal of the second switching element 125. This further optimizes the control of the power modulation system.

[0065] In some embodiments, the power modulation system 10 further includes a third capacitor element 13, which is connected in parallel between the first output terminal 11C and the second output terminal 11D to achieve high-frequency filtering.

[0066] In some embodiments, the control unit 30 is also used to control the first switching element 124 and the second switching element 125.

[0067] In the above embodiments proposed in this invention, the control unit 30 can be a microcontroller or other integrated control circuit; the motor drive unit 22 can be an independent drive control circuit or can share an integrated control circuit with the control unit 30; the motor switching unit 23 is an inverter integrated circuit; the position sensing unit 21 can be a sensing element, or a module that implements position detection by a software program stored in a hardware element, or a module that implements position detection by a software program stored in a hardware element in conjunction with electronic components. The above are all readily apparent to those skilled in the art and will not be elaborated further here.

[0068] In one specific implementation, such as Figure 7 The brushless motor 20 shown has a stator outer diameter of 135mm and a stator stack thickness of 13mm. It has an 8-pole, 12-slot structure. The phase resistance of the brushless motor 20 is 0.48mΩ, the d-axis inductance is 3.25mH, and the q-axis inductance is 4.77mH. Its line back electromotive force at 10000 rpm is as follows: Figure 8 As shown. Configuration as follows. Figure 3 In the power modulation circuit shown, both the first capacitor element 121 and the second capacitor element 122 are 220uF electrolytic capacitors. When both the first switching element 124 and the second switching element 125 are disconnected, the first capacitor element 121 and the second capacitor element 122 are in series when charging and in parallel when discharging. That is, the power modulation system 10 is in power factor compensation mode. The brushless motor 20 is controlled at a low constant speed of 2600rpm, with a current of 20A and a torque angle of 10°, resulting in an output speed of 5Nm. The current of the brushless motor during operation is as follows: Figure 9 As shown by the solid line, the bus voltage is as follows: Figure 10 As shown by the solid line; when both the first switching element 124 and the second switching element 125 are turned on, the first capacitor element 121 and the second capacitor element 122 are in parallel, that is, the power modulation system 10 is in large capacitor mode. When the brushless motor 20 is controlled at a low constant speed of 2600 rpm, the current is 20A and the torque angle is 10°, the output speed is also 5Nm. The current of the brushless motor during operation is as follows: Figure 9 As shown by the dashed line, the bus voltage is as follows: Figure 10 As shown by the dashed line. Figure 9 and Figure 10 As shown, when the power modulation system 10 is in large capacitor mode, the bus voltage fluctuation is small during low-speed, high-torque operation of the motor, resulting in smaller motor phase current fluctuations and a smaller effective current value. This not only improves the stability of the motor output torque but also reduces motor copper losses and current stress on the power transistors. The same configuration is used as follows... Figure 3In the power modulation circuit shown, both the first capacitor element 121 and the second capacitor element 122 are 220uF electrolytic capacitors. When both the first switching element 124 and the second switching element 125 are disconnected, the first capacitor element 121 and the second capacitor element 122 are in series when charging and in parallel when discharging. That is, the power modulation system 10 is in power factor compensation mode. The brushless motor 20 is controlled at a high-speed constant speed of 18000rpm, the d-axis current is negative 12A, the q-axis current is 2A, and the resulting input power is 1500W. The phase current of the brushless motor during operation is as follows: Figure 11 As shown by the solid line, the output current of rectifier unit 11 is as follows: Figure 12 As shown by the solid line; when both the first switching element 124 and the second switching element 125 are turned on, the first capacitor element 121 and the second capacitor element 122 are in parallel, that is, the power modulation system 10 is in large capacitor mode, the brushless motor 20 is controlled at a high speed constant speed of 18000 rpm, the motor d-axis current is negative 12A, the q-axis current is 2A, and the obtained input power is 1500W. The phase current of the brushless motor during operation is as follows: Figure 11 As shown by the dashed line, the output current of rectifier unit 11 is as follows: Figure 12 As shown by the solid line. Figure 11 and Figure 12 As shown, when the power modulation system 10 is in power factor compensation mode, the phase current of the brushless motor 20 at high speed is not much different from that when the power modulation system 10 is in large capacitor mode, but the output current amplitude of the rectifier unit 11 is much smaller. That is to say, the power factor of the brushless motor power modulation system 10 can be significantly improved when the motor is at high speed. Figure 13 Power factor comparison chart of brushless motor 20 and Figure 14 As shown in the comparison diagram of copper losses in the brushless motor 20, when the power modulation system 10 is in power factor compensation mode, it can significantly improve the power factor of the brushless motor during high-speed operation. When the power modulation system 10 is in large capacitor mode, it can significantly reduce the copper losses of the brushless motor during low-speed operation. In other words, as described above, the power modulation system 10 switches to power factor compensation mode when the brushless motor is at high speed and switches to large capacitor mode when it is at low speed. This not only ensures a high power factor for the brushless motor during high-speed operation but also reduces phase current spikes during low-speed operation, thereby guaranteeing output torque.

[0069] In other embodiments of the present invention, such as Figures 1-2The illustrated brushless power tool control method includes a brushless motor 20 and a power modulation system 10 for providing DC power to the brushless motor 20. The power modulation system 10 includes a rectifier unit 11 with a first input terminal 11A, a second input terminal 11B, a first output terminal 11C, and a second output terminal 11D. The first input terminal 11A and the second input terminal 11B are connected to an AC power grid, and the rectifier unit 11 converts AC power into DC power. A power factor correction unit 12 is connected in parallel between the first output terminal 11C and the second output terminal 11D. The power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, and a first switch element. The brushless power tool control method includes: when the brushless motor 20 is in a first operating state, the first switch element 124 and the second switch element 125 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the second capacitor element 122 and the second switch element 125 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the first diode element 123 is connected in series between the first capacitor element 121 and the second capacitor element 122. The method allows the connection state of the power factor correction unit 12 to be selected based on different operating states of the brushless motor. This enables the brushless motor to operate in a power factor compensation mode at high speeds to improve the power factor, and simultaneously enables the brushless motor to operate in a large capacitor mode at low speeds to reduce torque pulsation, thereby ensuring output torque and reducing motor copper losses.

[0070] In some alternative implementations, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0071] In one specific implementation, such as Figure 1As shown, when the brushless motor is running at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the conducting state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, effectively increasing the torque output of the power supply load. When the brushless motor is running at high speed, when the sinusoidal grid angle is 150 degrees and 330 degrees, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the conducting state, and the first capacitor element 121 and the second capacitor element 122 are discharged in parallel. When the sinusoidal grid angle is 180 degrees and 360 degrees, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the open state, and the first capacitor element 121 and the second capacitor element 122 are charged in series. The power modulation system operates in power factor compensation mode, improving the power factor of the power modulation system.

[0072] In another specific implementation, such as Figure 2 As shown, when the brushless motor is running at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the on state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, which can effectively increase the torque output of the power supply load. When the brushless motor is running at high speed, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the off state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in series. The power modulation system operates in power factor compensation mode, and the power factor of the power modulation system is improved.

[0073] Other embodiments of the present invention are as follows: Figures 1-2As shown, a brushless motor control system includes: a power modulation system 10 for providing DC power to a brushless motor 20; a control unit 30 for providing control signals to control the brushless motor 10; a motor drive unit 22 for receiving control signals from the control unit 30 and sending drive signals to drive the brushless motor 20 based on the control signals; and a motor switching unit 23 for receiving drive signals from the motor drive unit 22 and switching the connection between the power modulation system 10 and the brushless motor 20. The power modulation system 10 includes: a rectifier unit 11 having a first input terminal 11A, a second input terminal 11B, a first output terminal 11C, and a second output terminal 11D. The first input terminal 11A and the second input terminal 11B are used to connect to the AC power grid. Unit 11 is used to convert AC power into DC power; power factor correction unit 12 is connected in parallel between the first output terminal 11C and the second output terminal 11D; power factor correction unit 12 has a first capacitor element 121, a second capacitor element 122, a first diode element 123, a first switch element 124, and a second switch element 125. The first capacitor element 121 and the first switch element 124 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the second capacitor element 122 and the second switch element 124 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the first diode element 123 is connected in series between the first capacitor element 121 and the second capacitor element 122. The brushless motor power modulation system in this embodiment effectively improves the power factor and has low cost.

[0074] In some implementations, such as Figure 2 As shown, the power factor correction unit 12 has a first connection state and a second connection state. When the power factor correction unit 12 is in the first connection state, the first switching element 124 and the second switching element 125 are in the off state; when the power factor correction unit 12 is in the second connection state, the first switching element 124 and the second switching element 125 are in the on state. This allows the connection state of the power factor correction unit 12 to be selected based on different operating states of the brushless motor, thereby improving the power factor when the brushless motor is running at high speed and reducing torque ripple when the brushless motor is running at low speed, thus ensuring output torque and reducing motor copper losses.

[0075] In some embodiments, the brushless motor 20 has a first operating state and a second operating state. When the brushless motor 20 is in the first operating state, the power factor correction unit 12 is in a first connected state; when the brushless motor 20 is in the second operating state, the power factor correction unit 12 is in a second connected state. The operating mode of the power modulation system is switched based on the operating state of the brushless motor, resulting in smaller phase current glitches during low-speed, high-torque operation to ensure output torque and reduce motor copper losses, and a higher power factor during high-speed, high-power operation.

[0076] In some preferred embodiments, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0077] In some implementations such as Figure 1 , Figures 5-6 As shown, the first capacitor element 121 has a positive terminal and a negative terminal, the second capacitor element 122 has a positive terminal and a negative terminal, the first diode element 123 has a positive terminal and a negative terminal, the positive terminal of the first capacitor element 121 is connected to the first output terminal 11C, the negative terminal of the first capacitor element 121 is connected to one end of the first switching element 124, the other end of the first switching element 124 is connected to the second output terminal 11D, the negative terminal of the second capacitor element 122 is connected to the second output terminal 11D, the positive terminal of the second capacitor element 122 is connected to one end of the second switching element 125, the other end of the second switching element 125 is connected to the first output terminal 11C, the positive terminal of the first diode element 123 is connected to the negative terminal of the first capacitor element 121, and the negative terminal of the first diode element 123 is connected to the positive terminal of the first capacitor element 121.

[0078] In some optional embodiments, the first switching element 124 has a control terminal 124A, and the second switching element 125 has a control terminal 125A. The first switching element 124 and the second switching element 125 are controlled to turn on and off respectively by inputting a high-level or low-level signal to the control terminal 124A or the control terminal 125A. Figure 1 , Figures 5-6 In the embodiment shown, when the power tool is in a high-speed operating state, the first switching element 124 and the second switch 125 are either in a conducting state or a closed state. The angle control based on the sinusoidal power grid is not described in detail here. When the power tool is in a high-speed operating state, the first switching element 124 and the second switch 125 are in a conducting state, realizing the working mode of the power modulation system based on the operating state switching of the brushless motor. This allows the brushless motor to have smaller phase current glitches when running at low speed and high torque, thereby ensuring output torque and reducing motor copper loss. It also allows the brushless motor to have a high power factor when running at high speed and high power.

[0079] In some alternative embodiments, the first switching element 124 or the second switching element 125 may also be driven by a switch driving unit. For example... Figure 5 In some of the embodiments shown, the second switching element 125 is driven and controlled to be turned on or off by the switch driving unit 126.

[0080] In the above embodiments, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 may be equal or unequal. Preferably, the capacitance values ​​of the first capacitor element 121 and the second capacitor element 122 are similar or equal.

[0081] In some of these implementations, such as Figures 2-4 As shown, the power correction unit 12 also includes a second diode element 127, and a second switching element 125 having a first terminal and a second terminal. The second diode element 127 is connected in parallel between the first terminal and the second terminal of the second switching element 125. This further optimizes the control of the power modulation system.

[0082] In some embodiments, the power modulation system 10 further includes a third capacitor element 13, which is connected in parallel between the first output terminal 11C and the second output terminal 11D to achieve high-frequency filtering.

[0083] In some embodiments, the control unit 30 is also used to control the first switching element 124 and the second switching element 125.

[0084] In other embodiments of the present invention, such as Figures 1-2 The control method of the brushless motor control system shown includes: a power modulation system 10 for providing DC power to the brushless motor 20; the power modulation system 10 includes: a rectifier unit 11 having a first input terminal 11A, a second input terminal 11B, a first output terminal 11C, and a second output terminal 11D, the first input terminal 11A and the second input terminal 11B being connected to the AC power grid, and the rectifier unit 11 being used to convert AC power into DC power; a power factor correction unit 12 connected in parallel between the first output terminal 11C and the second output terminal 11D; the power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, and a first switch element. The brushless power tool control method includes: when the brushless motor 20 is in a first operating state, the first switch element 124 and the second switch element 125 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the second capacitor element 122 and the second switch element 125 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D; the first diode element 123 is connected in series between the first capacitor element 121 and the second capacitor element 122. The method allows the connection state of the power factor correction unit 12 to be selected based on different operating states of the brushless motor, thereby improving the power factor when the brushless motor is running at high speed and reducing torque pulsation when the brushless motor is running at low speed, thus ensuring output torque and reducing motor copper loss.

[0085] In one specific implementation, such as Figure 1As shown, when the brushless motor is running at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the conducting state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, effectively increasing the torque output of the power supply load. When the brushless motor is running at high speed, when the sinusoidal grid angle is 150 degrees and 330 degrees, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the conducting state, and the first capacitor element 121 and the second capacitor element 122 are discharged in parallel. When the sinusoidal grid angle is 180 degrees and 360 degrees, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the open state, and the first capacitor element 121 and the second capacitor element 122 are charged in series. The power modulation system operates in power factor compensation mode, improving the power factor of the power modulation system.

[0086] In another specific implementation, such as Figure 2 As shown, when the brushless motor is running at low speed, a high-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the on state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in parallel. The power modulation system operates in large capacitor mode, which can effectively increase the torque output of the power supply load. When the brushless motor is running at high speed, a low-level signal is input to control terminals 126A and 124A. The first switching element 124 and the second switching element 125 are in the off state, and the first capacitor element 121 and the second capacitor element 122 are charged and discharged in series. The power modulation system operates in power factor compensation mode, and the power factor of the power modulation system is improved.

[0087] In some alternative implementations, the first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

[0088] In some of the above optional embodiments, the control unit 30 can directly control the first switching element 121 and the second switching element 122. In other optional embodiments, the control unit 30 can also control the first switching element 121 and the second switching element 122 through the switch driving unit 133. This is easy for those skilled in the art to conceive of, and will not be elaborated here.

[0089] In some of the preferred embodiments described above, the low-speed operating state refers to a speed 20% to 30% below the maximum speed of the brushless motor, and the high-speed operating state refers to a speed 20% to 30% above the maximum speed of the brushless motor. Of course, for those skilled in the art, the low-speed and high-speed states can be set as other judgment criteria depending on the load characteristics of different brushless power tools. At the same time, the speed can also be judged by judging the current, voltage, or other electrical signals, which will not be limited here.

[0090] In the above embodiments, the first switching element 124 or the second switching element 125 can be a thyristor, a MOSFET, an IGBT, or a gallium nitride, and there are no limitations on this. Of course, it can also be other switching elements known to those skilled in the art, which will not be described in detail here. Figures 5-6 As shown, when the first switching element 124 and the second switching element 125 are disconnected, the second switching element 125 is equivalent to a diode with its positive terminal connected to the first output terminal 11C and its negative terminal connected to the second output terminal 11D. The first switching element 124 is equivalent to a diode with its positive terminal connected to the negative terminal of the first capacitor element 121 and its negative terminal connected to the second output terminal 11D, thereby enabling the power factor correction unit to operate in power factor compensation mode. Therefore, in some other optional embodiments, if the element selected by the first switching element 124 or the second switching element 125 cannot be equivalent to a diode connected in series in the circuit when disconnected, the first switching element 124 or the second switching element 125 needs to be connected in parallel with a diode.

[0091] In the above embodiments, the brushless power tool is a high-pressure brushless power tool, which can be a high-pressure brushless angle grinder, a high-pressure brushless electric drill, a high-pressure brushless circular saw, etc., or a high-pressure brushless household appliance such as a juicer, blender, or bread maker, or a household or industrial high-pressure brushless power tool such as a vacuum cleaner, sweeper, or high-pressure washer, etc., without limitation.

[0092] The above-described specific embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications, substitutions, and improvements made by those skilled in the art to the technical solutions of the present invention based on the provided textual description and drawings, without departing from the design concept and spirit of the present invention, should all fall within the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

Claims

1. A power modulation system, comprising: A rectifier unit has a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal and the second input terminal are used to connect to an AC power grid. The rectifier unit is used to convert AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal; The power factor correction unit is characterized in that it comprises a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element; the first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal; the second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal; and the first diode element is connected in series between the first capacitor element and the second capacitor element.

2. The power modulation system according to claim 1, characterized in that, The capacitance of the first capacitor element is equal to the capacitance of the second capacitor element.

3. The power modulation system according to claim 1, characterized in that, The power correction unit also has a second diode element, the first switching element has a first terminal and a second terminal, and the second diode element is connected in parallel between the first terminal and the second terminal of the second switching element.

4. The power modulation system according to claim 3, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the off state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the on state.

5. The power modulation system according to claim 1, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in an open or closed state based on the sinusoidal power grid angle. When the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

6. A brushless power tool, comprising: The brushless motor is equipped with a position sensing unit. A power modulation system is used to provide DC power to the brushless motor; A control unit is used to provide control signals to control the brushless motor; A motor drive unit is used to receive control signals from the control unit and send drive signals to drive the brushless motor based on the control signals. A motor switching unit is used to receive the drive signal from the motor drive unit and switch the connection between the power modulation system and the brushless motor. The power modulation system is characterized by comprising: A rectifier unit has a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal and the second input terminal are used to connect to an AC power grid. The rectifier unit is used to convert AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal; The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element. The first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The first diode element is connected in series between the first capacitor element and the second capacitor element.

7. The power modulation system according to claim 6, characterized in that, The power correction unit also has a second diode element, the first switching element has a first terminal and a second terminal, and the second diode element is connected in parallel between the first terminal and the second terminal of the first switching element.

8. The power modulation system according to claim 7, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the off state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the on state.

9. The power modulation system according to claim 6, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in an open or closed state based on the sinusoidal power grid angle. When the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

10. The brushless power tool according to claim 6, characterized in that, The control unit is also used to control the first switching element and the second switching element.

11. A control method for a brushless power tool, the brushless power tool comprising: A brushless motor and a power modulation system for providing DC power to the brushless motor; The power modulation system includes: A rectifier unit has a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal and the second input terminal are used to connect to an AC power grid. The rectifier unit is used to convert AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal; The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element. The first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The first diode element is connected in series between the first capacitor element and the second capacitor element. The brushless power tool control method is characterized by comprising: When the brushless motor is in the first operating state, the first switching element and the second switching element can be disconnected; When the brushless motor is in the second operating state, the first switching element and the second switching element are turned on.

12. The brushless power tool control method according to claim 11, characterized in that, The first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

13. A brushless motor control system, comprising: A power modulation system is used to provide DC power to the brushless motor; A control unit is used to provide control signals to control the brushless motor; A motor drive unit is used to receive control signals from the control unit and send drive signals to drive the brushless motor based on the control signals. A motor switching unit is used to receive the drive signal from the motor drive unit and switch the connection between the power modulation system and the brushless motor. The power modulation system is characterized by comprising: A rectifier unit has a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal and the second input terminal are used to connect to an AC power grid. The rectifier unit is used to convert AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal; The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element. The first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The first diode element is connected in series between the first capacitor element and the second capacitor element.

14. The brushless motor control system according to claim 13, characterized in that, The power correction unit also has a second diode element, the first switching element has a first terminal and a second terminal, and the second diode element is connected in parallel between the first terminal and the second terminal of the first switching element.

15. The brushless motor control system according to claim 14, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in the off state; when the power factor correction unit is in the second connection state, the first switching element and the second switching element are in the on state.

16. The brushless motor control system according to claim 13, characterized in that, The power factor correction unit has a first connection state and a second connection state. When the power factor correction unit is in the first connection state, the first switching element and the second switching element are in an open or closed state based on the sinusoidal power grid angle. When the power factor correction unit is in the second connection state, the first switching element and the second switching element are in a closed state.

17. The brushless motor control system according to claim 13, characterized in that, The control unit is also used to control the first switching element and the second switching element.

18. A control method for a brushless motor control system, the brushless motor control system comprising: A power modulation system for providing DC power to a brushless motor; The power modulation system includes: A rectifier unit has a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal and the second input terminal are used to connect to an AC power grid. The rectifier unit is used to convert AC power into DC power. A power factor correction unit is connected in parallel between the first output terminal and the second output terminal; The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a first switch element, and a second switch element. The first capacitor element and the first switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The second capacitor element and the second switch element are connected in series and connected in parallel between the first output terminal and the second output terminal. The first diode element is connected in series between the first capacitor element and the second capacitor element. The control method is characterized by comprising: When the brushless motor is in the first operating state, the first switching element and the second switching element can be disconnected; When the brushless motor is in the second operating state, the first switching element and the second switching element are turned on.

19. The control method according to claim 18, characterized in that, The first operating state is a high-speed operating state, and the second operating state is a low-speed operating state.

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