Power supply modulation system, brushless electric tool and control method therefor, and brushless-electric-motor control system and control method therefor
By introducing a power modulation system into high-voltage brushless power tools and switching the connection methods of capacitor and switching elements, the design problem of the filter capacitor at the back end of the rectifier bridge is solved, achieving torque output at low speeds and high power factor at high speeds, thereby improving the operating efficiency of the motor and the power factor of the power grid.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NANJING MAGTEK POWER SYSTEM CO LTD
- Filing Date
- 2025-03-31
- Publication Date
- 2026-07-16
Smart Images
Figure CN2025086205_16072026_PF_FP_ABST
Abstract
Description
A power modulation system, a brushless power tool and its control method, and a brushless motor control system and its control method.
[0001] Cross-references to related applications
[0002] This application claims priority to Chinese Patent Application No. 2025100310665, filed January 9, 2025, entitled “A power modulation system, a brushless power tool and a control method thereof”, and to Chinese Patent Application No. 2025103464557, filed March 24, 2025, entitled “A power modulation system, a brushless power tool and a control method thereof, and a brushless motor control system and a control method thereof”, the entire contents of which are incorporated herein by reference. Technical Field
[0003] This application 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
[0004] 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.
[0005] 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.
[0006] 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
[0007] The technical problem this application aims to solve is how to improve the power factor of high-voltage brushless power tools in a low-cost and effective manner.
[0008] To address the aforementioned problems, this application 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 modulation system further includes a filter unit having a third capacitor element and a switching element, and connected in parallel between the first output terminal and the second output terminal. The power modulation system proposed in this application 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. Further, the power factor correction unit has a first capacitor element, a second capacitor element, a first diode element, a second diode element, and a third diode element; the first capacitor element and the first diode 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 diode element are connected in series and connected in parallel between the first output terminal and the second output terminal; the third diode element is connected in series between the first capacitor element and the second capacitor element.
[0009] Furthermore, the filtering unit also includes a switch driving unit, which is used to drive the switching element to conduct in a first operating state, thereby connecting the third capacitor element in parallel between the first output terminal and the second output terminal, and to drive the switching element to disconnect in a second operating state, thereby putting the third capacitor element in a non-operating state. Based on the operating state switching power modulation system of the brushless motor, the brushless motor exhibits smaller phase current glitches during low-speed, high-torque operation, thus ensuring output torque and reducing motor copper losses, while maintaining a high power factor during high-speed, high-power operation.
[0010] Furthermore, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.
[0011] Furthermore, the filtering unit also includes a switch driving unit and an inductor. The inductor is connected in series with the third capacitor. The switch driving unit is used to drive the switch to conduct in a first operating state, so that the third capacitor and the inductor are connected in parallel between the first output terminal and the second output terminal. It is also used to drive the switch to disconnect in a second operating state, so that the third capacitor and the inductor are in a non-operating state.
[0012] Furthermore, the capacitance of the third capacitor element is greater than or equal to the capacitance of the first capacitor element and the second capacitor element connected in series.
[0013] Furthermore, the capacitance of the third capacitor element is greater than the capacitance of the first capacitor element, and the capacitance of the third capacitor element is greater than the capacitance of the second capacitor element.
[0014] Furthermore, the power modulation system also includes a fourth capacitor element, which is connected in parallel between the first output terminal and the second output terminal.
[0015] This application 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, the first and second input terminals being connected to an AC power grid, and the rectifier unit converting AC power into DC power; a power factor correction unit connected in parallel between the first and second output terminals; and a filter unit having a third capacitor element and a switching element, connected in parallel between the first and second output terminals. The brushless power tool proposed in this application effectively improves the power factor when the brushless motor is running at high speed and ensures output torque while reducing motor copper losses when the brushless motor is running at low speed.
[0016] Furthermore, the power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a second diode element, and a third diode element. The first capacitor element and the first diode 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 diode element are connected in series and connected in parallel between the first output terminal and the second output terminal. The third diode element is connected in series between the first capacitor element and the second capacitor element.
[0017] Furthermore, the filtering unit also has a switch driving unit, which is used to drive the switch element to conduct in a first operating state, so that the third capacitor element is connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switch element to disconnect in a second operating state, so that the third capacitor element is in a non-operating state.
[0018] Furthermore, the filtering unit also includes a switch driving unit and an inductor. The inductor is connected in series with the third capacitor. The switch driving unit is used to drive the switch to conduct in a first operating state, thereby connecting the third capacitor and the inductor in parallel between the first output terminal and the second output terminal. It is also used to drive the switch to disconnect in a second operating state, thereby placing the third capacitor and the inductor in a non-operating state. The brushless power tool proposed in this application effectively improves the power factor when the brushless motor is running at high speed and ensures output torque while reducing motor copper losses when the brushless motor is running at low speed. Further, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.
[0019] Furthermore, the capacitance of the third capacitor element is greater than or equal to the capacitance of the first capacitor element and the second capacitor element connected in series.
[0020] Furthermore, the capacitance of the third capacitor element is greater than the capacitance of the first capacitor element, and the capacitance of the third capacitor element is greater than the capacitance of the second capacitor element.
[0021] Furthermore, the control unit is also used to control the switch drive unit.
[0022] This application also proposes 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 comprising: 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 modulation system further comprising a filter unit having a third capacitor element and a switching element, and connected in parallel between the first output terminal and the second output terminal; the control method for the brushless power tool comprising: when the brushless motor is in a first operating state, the control unit controls the switching element to be turned on, thereby connecting the third capacitor element in parallel between the first output terminal and the second output terminal; when the brushless motor is in a second operating state, the control unit controls the switching element to be turned off, thereby putting the third capacitor element in a non-operating state.
[0023] Furthermore, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state. Based on the operating state switching power modulation system of the brushless motor, the brushless motor exhibits smaller phase current glitches during low-speed, high-torque operation, thus ensuring output torque and reducing motor copper losses, while maintaining a high power factor during high-speed, high-power operation.
[0024] This application 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 the 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 the 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 and second input terminals being connected to an AC power grid, the rectifier unit converting AC power into DC power; a power factor correction unit connected in parallel between the first and second output terminals; and a filter unit having a third capacitor element and a switching element, connected in parallel between the first and second output terminals. The brushless motor control system proposed in this application effectively improves the power factor when the brushless motor is running at high speed, while simultaneously reducing torque ripple when the brushless motor is running at low speed, thereby ensuring output torque and reducing motor copper losses.
[0025] Furthermore, the power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a second diode element, and a third diode element. The first capacitor element and the first diode 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 diode element are connected in series and connected in parallel between the first output terminal and the second output terminal. The third diode element is connected in series between the first capacitor element and the second capacitor element.
[0026] Furthermore, the filtering unit also has a switch driving unit, which is used to drive the switch element to conduct in a first operating state, so that the third capacitor element is connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switch element to disconnect in a second operating state, so that the third capacitor element is in a non-operating state.
[0027] Furthermore, the filtering unit also includes a switch driving unit and an inductor. The inductor is connected in series with the third capacitor. The switch driving unit is used to drive the switch to conduct in a first operating state, so that the third capacitor and the inductor are connected in parallel between the first output terminal and the second output terminal. It is also used to drive the switch to disconnect in a second operating state, so that the third capacitor and the inductor are in a non-operating state.
[0028] Furthermore, the capacitance of the third capacitor element is greater than or equal to the capacitance of the first capacitor element and the second capacitor element connected in series.
[0029] Furthermore, the control unit is also used to control the switch drive unit.
[0030] This application also proposes a control method for a brushless motor control system, the brushless motor control system comprising: a power modulation system for providing DC power to the brushless motor; the 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, 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 modulation system further comprising a filter unit having a third capacitor element and a switching element, and connected in parallel between the first output terminal and the second output terminal; the control method of the brushless motor control system comprising: when the brushless motor is in a first operating state, the control unit controls the switching element to be turned on, thereby connecting the third capacitor element in parallel between the first output terminal and the second output terminal; when the brushless motor is in a second operating state, the control unit controls the switching element to be turned off, thereby putting the third capacitor element in a non-operating state.
[0031] Furthermore, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state. Based on the operating state switching power modulation system of the brushless motor, the brushless motor exhibits smaller phase current glitches during low-speed operation, thereby ensuring output torque and reducing motor copper losses, while maintaining a high power factor during high-speed operation.
[0032] The power modulation system, brushless power tool and its control method, and brushless motor control system and its control method proposed in this application 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
[0033] The present application will be further described and explained below with reference to the accompanying drawings.
[0034] Figure 1 is a system circuit block diagram of a high-voltage brushless power tool according to one embodiment of this application.
[0035] Figure 2 is a schematic diagram of a power modulation system circuit according to one embodiment of this application.
[0036] Figure 3 is a schematic diagram of a power modulation system circuit according to another embodiment of this application.
[0037] Figure 4 is an equivalent circuit diagram of the first operating state in one embodiment of this application.
[0038] Figure 5 is an equivalent circuit diagram of the second operating state in one embodiment of this application.
[0039] Figure 6 is a schematic diagram of a brushless motor according to one embodiment of this application.
[0040] Figure 7 is a schematic diagram of the back electromotive force of a brushless motor according to one embodiment of this application.
[0041] Figure 8 is a schematic diagram comparing the current of the equivalent circuits in Figures 4 and 5 when the brushless motor is running at low speed and high torque.
[0042] Figure 9 is a schematic diagram comparing the voltage of the equivalent circuits in Figures 4 and 5 when the brushless motor is running at low speed and high torque.
[0043] Figure 10 is a schematic diagram comparing the phase currents of the equivalent circuits in Figures 4 and 5 when the brushless motor is running at high speed and high power.
[0044] Figure 11 is a schematic diagram comparing the output current of the rectifier unit in the equivalent circuits shown in Figures 4 and 5 when the brushless motor is running at high speed and high power.
[0045] Figure 12 is a schematic diagram comparing the power factor of the equivalent circuits in Figures 4 and 5.
[0046] Figure 13 is a schematic diagram comparing the copper losses of the brushless motor shown in Figure 6.
[0047] Figure 14 is a schematic diagram of a power modulation system circuit according to another embodiment of this application. Detailed Implementation
[0048] The technical solution of this application will be explained more clearly and completely below with reference to the accompanying drawings and through the description of the preferred embodiments of this application.
[0049] Some embodiments of this application are shown in Figure 1. 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 connected to the 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 11A and the second output terminal 11B; the power modulation system 10 also includes a filter unit 13, which has a third capacitor element 131 and a switching element 132, and is connected in parallel between the first output terminal 11A and the second output terminal 11B. The power modulation system in this embodiment effectively improves the power factor when the brushless motor is running at high speed, while simultaneously reducing torque ripple when the brushless motor is running at low speed, thereby ensuring output torque and reducing motor copper losses.
[0050] In some preferred embodiments, as shown in FIG14, the power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, a second diode element 124, and a third diode element 125. The first capacitor element 121 and the first diode element 123 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 diode element 124 are connected in series and connected in parallel between the first output terminal 11C and the second output terminal 11D; the third diode element 125 is connected in series between the first capacitor element 121 and the second capacitor element 122. When the first input terminal 11A and the second input terminal 11B are connected to the AC power grid, the first capacitor element 121 and the second capacitor element 122 are charged in series. When the voltage value between the first output terminal 11C and the second output terminal 11D is less than half of the voltage value of the first capacitor element 121 and the second capacitor element 122 connected in series, the first capacitor element 121 and the second capacitor element 122 are discharged in parallel, effectively improving the power factor.
[0051] In some other optional embodiments, as shown in FIG14, the filter unit 13 also has a switch driving unit 133. The switch driving unit 133 is used to drive the switch element 132 to conduct in the first operating state, so that the third capacitor element 131 is connected in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in the second operating state, so that the third capacitor element 131 is in a non-working state. This realizes the selection of operating conditions based on different power supply loads, so that the power factor is improved when the brushless motor runs at high speed, while the torque pulsation is reduced when the brushless motor runs at low speed, thereby ensuring the output torque and reducing the copper loss of the motor. In some optional embodiments, as shown in Figures 2-3, the filter unit 13 has a switch driving unit 133 and an inductor 134. The inductor 134 is connected in series with the third capacitor 131. The switch driving unit 133 is used to drive the switch element 132 to conduct in a first operating state, so that the third capacitor 131 and the inductor 134 are connected in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in a second operating state, so that the third capacitor 131 and the inductor 134 are in a non-operating state. As shown in Figure 2, in one specific embodiment, in the second operating state, a low level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is disconnected, that is, the third capacitor 131 is disconnected from the first output terminal 11C. The first capacitor element 121 and the second capacitor element 122 are connected in series during charging and in parallel during discharging. The power modulation system operates in power factor compensation mode, and the system power factor is improved. The third capacitor value is chosen to be relatively large, such as 220uf, 330uf, 470uf, 560uf, etc., with a withstand voltage of 400V / 450V. Of course, other capacitor values or withstand voltage values that meet the requirements can also be used by those skilled in the art. In the second operating state, a high level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is turned on, that is, the third capacitor 131 and the inductor element 134 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D. At this time, the power modulation system is in large capacitor mode, which can effectively increase the torque output of the power supply load.
[0052] In some optional implementations, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state. The operating mode of the power modulation system based on the brushless motor's operating state switching allows the brushless motor to have smaller phase current glitches during low-speed operation, thereby ensuring output torque and reducing motor copper losses, while maintaining a high power factor during high-speed operation.
[0053] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than or equal to the capacitance of the first capacitor element 121 and the second capacitor element 122 connected in series. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0054] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than the capacitance of the first capacitor element 121, and the capacitance of the third capacitor element 131 is greater than the capacitance of the second capacitor element 122. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0055] In some preferred embodiments, when the rectifier unit is connected to an AC240V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 22uF to 330uF; when the rectifier unit is connected to an AC120V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 44uF to 560uF, effectively reducing the cost of the power modulation system.
[0056] In some preferred embodiments, the capacitance of the first capacitor element 121 is equal to that of the second capacitor element 122, and can be 47uF, 68uF, 82uF, 150uF, etc., with a voltage rating of 250V / 400V / 450V. Of course, other capacitance values or voltage ratings that meet the requirements are also acceptable to those skilled in the art. In some other optional embodiments, as shown in Figures 2-3, the modulation circuit 10 further includes a fourth capacitor element 14, which is connected in parallel between the first output terminal 11C and the second output terminal 11D. In some preferred embodiments, the capacitance of the fourth capacitor element 14 is less than 10uF. In some preferred embodiments, the fourth capacitor element 14 is a CBB capacitor with a capacitance of 2.2uF and a voltage rating of 450V. Of course, other capacitance values or voltage ratings that meet the requirements are also acceptable to those skilled in the art.
[0057] In other embodiments of this application, as shown in FIG1, the brushless power tool includes: a brushless motor 20, equipped with a position sensing unit 21; a power modulation system 10 for providing DC power to the brushless motor; a control unit 30 for providing control signals to control the brushless motor 20; 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 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 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 is connected in parallel between the first output terminal 11C and the second output terminal 11D; the power modulation system 10 also includes a filter unit 13, which has a third capacitor element 131 and a switching element 132, and is connected in parallel between the first output terminal 11C and the second output terminal 11D. In this embodiment, the brushless motor power modulation system effectively improves the power factor when the brushless motor is running at high speed, while simultaneously reducing torque ripple when the brushless motor is running at low speed, thereby ensuring output torque and reducing motor copper losses.
[0058] In some preferred embodiments, the power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, a second diode element 124, and a third diode element 125. The first capacitor element 121 and the first diode element 123 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 diode element 124 are connected in series and connected in parallel between the first output terminal 11C and the second output terminal 11D. The third diode element 125 is connected in series between the first capacitor element 121 and the second capacitor element 122. When one input terminal 11A and the second input terminal 11B are connected to the AC power grid, the first capacitor element 121 and the second capacitor element 122 are charged in series. When the voltage value between the first output terminal 11C and the second output terminal 11D is less than half of the voltage value of the first capacitor element 121 and the second capacitor element 122 connected in series, the first capacitor element 121 and the second capacitor element 122 are discharged in parallel, effectively improving the power factor.
[0059] In some other alternative embodiments, the filter unit 13 also has a switch driving unit 133, which is used to drive the switch element 132 to conduct in a first operating state, so that the third capacitor element 131 is connected in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in a second operating state, so that the third capacitor element 131 is in a non-working state. This realizes the selection of different operating states based on the brushless motor, effectively 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, thereby ensuring output torque and reducing motor copper loss.
[0060] In some optional embodiments, the filter unit 13 also includes a switch driving unit 133 and an inductor 134, the inductor 134 being connected in series with the third capacitor 131. The switch driving unit 133 is used to drive the switch element 132 to conduct in a first operating state, thereby connecting the third capacitor 131 and the inductor 134 in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in a second operating state, thereby putting the third capacitor 131 and the inductor 134 in a non-operating state.
[0061] In one specific implementation, during the second operating state, a low level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is disconnected, that is, the third capacitor 131 is disconnected from the first output terminal 11C. The first capacitor element 121 and the second capacitor element 122 are connected in series during charging and in parallel during discharging. The equivalent circuit diagram is shown in Figure 5. The power modulation system 10 operates in power factor compensation mode, and the power factor of the power modulation system is improved. Among them, the capacitance value of the third capacitor is relatively large, such as 220uF, 330uF, 470uF, 560uF, etc., with a withstand voltage of 400V / 450V. Of course, for those skilled in the art, other capacitance values or withstand voltage values that meet the requirements are also possible. In the second operating state, a high level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is turned on, that is, the third capacitor 131 and the inductor element 134 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D. The equivalent circuit diagram is shown in Figure 4. At this time, the power modulation system is in the large capacitor mode, which can effectively increase the torque output of the power supply load.
[0062] In some optional implementations, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state. The operating mode of the power modulation system based on the brushless motor's operating state switching allows the brushless motor to have smaller phase current glitches during low-speed operation, thereby ensuring output torque and reducing motor copper losses, while maintaining a high power factor during high-speed operation.
[0063] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than or equal to the capacitance of the first capacitor element 121 and the second capacitor element 122 connected in series. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0064] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than the capacitance of the first capacitor element 121, and the capacitance of the third capacitor element 131 is greater than the capacitance of the second capacitor element 122. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0065] In some preferred embodiments, when the rectifier unit is connected to an AC240V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 22uF to 330uF; when the rectifier unit is connected to an AC120V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 44uF to 560uF, effectively reducing the cost of the power modulation system.
[0066] In some preferred embodiments, the capacitance value of the first capacitor element 121 is equal to the capacitance value of the second capacitor element 122, and can be 47uf, 68uf, 82uf, 150uf, etc., with a withstand voltage of 250V / 400V / 450V. Of course, other capacitance values or withstand voltage values that meet the requirements can also be used by those skilled in the art. In the above embodiments proposed in this application, 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 software programs stored in hardware components, or a module that implements position detection by software programs stored in hardware components in conjunction with electronic components. The above are all readily apparent to those skilled in the art and will not be elaborated further here.
[0067] In one specific implementation, as shown in Figure 6, the brushless motor 20 has a stator outer diameter of 135mm, a stator stack thickness of 13mm, and 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 10000rpm is shown in Figure 7. When the power modulation system 10 is in power factor compensation mode, that is, when only the power factor correction unit 12 with a 150uF electrolytic capacitor is connected after the rectifier unit 11, the output speed is 5Nm when the low-speed constant speed control is 1200rpm, the brushless motor current is 20A, and the torque angle is 10°. When a power factor correction unit 12 with a 150uF electrolytic capacitor and a filter unit 13 with a 440uF electrolytic capacitor are simultaneously connected after the rectifier unit 11, the output torque obtained at a low-speed constant speed of 1200rpm, a motor current of 20A, and a torque angle of 10° is also 5Nm. The current comparison of the brushless motor 20 under the above two equivalent circuits (as shown in Figures 4 and 5) during low-speed, high-torque operation is shown in Figure 8, and the voltage comparison is shown in Figure 9. When the power factor correction unit 12 with two 150uF electrolytic capacitors and the filter unit 13 with a 440uF electrolytic capacitor are simultaneously connected after the rectifier unit 11, the bus voltage fluctuation of the brushless motor 20 during low-speed, high-torque operation is small, resulting in smaller phase current fluctuations and a smaller effective current value. This not only helps improve the stability of the motor's output torque and ensures the output torque, but also reduces the motor's copper losses and the current stress on the power transistors. When the power modulation system 10 is in power factor compensation mode, that is, when only the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, the high-speed constant speed is controlled at 18000rpm, the brushless motor d-axis current is negative 12A, the q-axis current is 2A, and the resulting input power is 1500W. When the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, along with the filter unit 13 with a 440uF electrolytic capacitor, the high-speed constant speed is controlled at 18000rpm, the brushless motor d-axis current is negative 12A, the q-axis current is 2A, and the resulting input power is also 1500W. Figure 10 shows a comparison of the phase currents of the brushless motor under the two equivalent circuits described above (as shown in Figures 4 and 5) during high-speed, high-power operation. Figure 11 also shows a comparison of the output currents of the rectifier unit 11. It can be seen that when only the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, the phase currents of the brushless motor during high-speed, high-power operation are not significantly different from those when the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, compared to the phase current of the filter unit 13 with a 440uF electrolytic capacitor. However, the output current amplitude of the rectifier unit 11 is much smaller. Therefore, connecting only the power factor correction unit 12 with two 150uF electrolytic capacitors after the rectifier unit 11 can significantly improve the power factor of the motor control system.Figure 12 shows the power factor comparison of the brushless motor under the two equivalent circuits mentioned above (as shown in Figures 4 and 5), and Figure 13 shows the copper loss comparison of the brushless motor. When only the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, the power factor of the brushless motor during high-speed and high-power operation can be greatly improved. When the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, along with the filter unit 13 with a 440uF electrolytic capacitor, the copper loss of the brushless motor during low-speed and high-torque operation can be greatly reduced.
[0068] Therefore, in some of the above embodiments, when the brushless power tool is in its first operating state, that is, low speed and high torque, the control switch element 132 is turned on, and the power factor correction unit 12 with two 150uF electrolytic capacitors and the filter unit 13 with a 440uF electrolytic capacitor are simultaneously connected after the rectifier unit 11, so that the motor has smaller phase current glitches and lower motor copper losses when running at low speed and high torque; when the brushless power tool is in its first operating state, that is, high speed and high power, only the power factor correction unit 12 with two 150uF electrolytic capacitors is connected after the rectifier unit 11, so that the brushless motor has a high power factor when running at high speed and high power.
[0069] In other embodiments of this application, as shown in FIG1, the brushless power tool control method includes: a brushless motor 20 and a power modulation system 10 for providing DC power to the brushless motor; 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 used to connect to the AC power grid, and the rectifier unit 11 being used to convert AC power into DC power; and a power factor correction unit 12 connected in parallel between the first output terminal 11A and the second output terminal 11B. The power modulation system 10 also includes a filtering unit 13, which has a third capacitor element 131 and a switching element 132, and is connected in parallel between the first output terminal 11C and the second output terminal 11D. The brushless power tool control method includes: when the brushless motor 20 is in a first operating state, the control unit 30 controls the switching element 132 to be turned on, thereby connecting the third capacitor element 131 in parallel between the first output terminal 11C and the second output terminal 11D; when the brushless motor 20 is in a second operating state, the control unit 30 controls the switching element 132 to be turned off, thereby putting the third capacitor element 131 in a non-operating state. This achieves the brushless power tool improving the power factor while ensuring torque output and reducing motor copper losses. In some optional embodiments, the control unit 30 can directly control the switching element 132; in other optional embodiments, the control unit 30 can also control it through a switch drive unit 133. This is readily apparent to those skilled in the art and will not be elaborated further here.
[0070] In some alternative implementations, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.
[0071] In other embodiments of this application, as shown in FIG1, the brushless motor control system includes: a power modulation system 10 for providing DC power to the brushless motor; a control unit 30 for providing control signals to control the brushless motor 20; 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 1... The system comprises 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 the AC power grid. 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 modulation system 10 also includes a filter unit 13, which has a third capacitor element 131 and a switching element 132, and is connected in parallel between the first output terminal 11C and the second output terminal 11D. In this embodiment, the brushless motor control system effectively improves the power factor when the brushless motor is running at high speed, while simultaneously reducing torque ripple to ensure output torque and reducing motor copper losses when the brushless motor is running at low speed.
[0072] In some preferred embodiments, the power factor correction unit 12 includes a first capacitor element 121, a second capacitor element 122, a first diode element 123, a second diode element 124, and a third diode element 125. The first capacitor element 121 and the first diode element 123 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 diode element 124 are connected in series and connected in parallel between the first output terminal 11C and the second output terminal 11D. The third diode element 125 is connected in series between the first capacitor element 121 and the second capacitor element 122. When one input terminal 11A and the second input terminal 11B are connected to the AC power grid, the first capacitor element 121 and the second capacitor element 122 are charged in series. When the voltage value between the first output terminal 11C and the second output terminal 11D is less than half of the voltage value of the first capacitor element 121 and the second capacitor element 122 connected in series, the first capacitor element 121 and the second capacitor element 122 are discharged in parallel, effectively improving the power factor.
[0073] In some other optional embodiments, the filter unit 13 also has a switch driving unit 133, which is used to drive the switch element 132 to conduct in the first operating state, so that the third capacitor element 131 is connected in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in the second operating state, so that the third capacitor element 131 is in a non-working state. This realizes the selection based on the operating state of the brushless motor, so that the power factor can be improved when the brushless motor runs at high speed, while ensuring the output torque of the brushless motor when running at low speed and reducing the copper loss of the motor.
[0074] In some optional embodiments, the filter unit 13 also includes a switch driving unit 133 and an inductor 134, the inductor 134 being connected in series with the third capacitor 131. The switch driving unit 133 is used to drive the switch element 132 to conduct in a first operating state, thereby connecting the third capacitor 131 and the inductor 134 in parallel between the first output terminal 11C and the second output terminal 11D. It is also used to drive the switch element 132 to disconnect in a second operating state, thereby putting the third capacitor 131 and the inductor 134 in a non-operating state.
[0075] In one specific implementation, during the second operating state, a low level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is disconnected, that is, the third capacitor 131 is disconnected from the first output terminal 11C. The first capacitor element 121 and the second capacitor element 122 are connected in series during charging and in parallel during discharging. The equivalent circuit diagram is shown in Figure 5. The power modulation system 10 operates in power factor compensation mode, and the power factor of the power modulation system is improved. Among them, the capacitance value of the third capacitor is relatively large, such as 220uF, 330uF, 470uF, 560uF, etc., with a withstand voltage of 400V / 450V. Of course, for those skilled in the art, other capacitance values or withstand voltage values that meet the requirements are also possible. In the second operating state, a high level is provided to the control terminal 133A of the switch drive unit 133. At this time, the switch element 132 is turned on, that is, the third capacitor 131 and the inductor element 134 are connected in series and in parallel between the first output terminal 11C and the second output terminal 11D. The equivalent circuit diagram is shown in Figure 4. At this time, the power modulation system is in the large capacitor mode, which can effectively increase the torque output of the power supply load.
[0076] In some optional implementations, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state. The operating mode of the power modulation system based on the brushless motor's operating state switching allows the brushless motor to have smaller phase current glitches during low-speed operation, thus ensuring torque output and reducing motor copper losses, while maintaining a high power factor during high-speed operation.
[0077] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than or equal to the capacitance of the first capacitor element 121 and the second capacitor element 122 connected in series. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0078] In some preferred embodiments, the capacitance of the third capacitor element 131 is greater than the capacitance of the first capacitor element 121, and the capacitance of the third capacitor element 131 is greater than the capacitance of the second capacitor element 122. The capacitance of the first capacitor element 121 may be equal to or different from the capacitance of the second capacitor element 122.
[0079] In some preferred embodiments, when the rectifier unit is connected to an AC240V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 22uF to 330uF; when the rectifier unit is connected to an AC120V system, the capacitance of the first capacitor element 121 and the capacitance of the second capacitor element 122 are 44uF to 560uF, effectively reducing the cost of the power modulation system.
[0080] In some preferred embodiments, the capacitance of the first capacitor element 121 is equal to the capacitance of the second capacitor element 122, and can be 47uF, 68uF, 82uF, 150uF, etc., with a voltage rating of 250V / 400V / 450V. Of course, other capacitance values or voltage ratings that meet the requirements can also be used by those skilled in the art.
[0081] In other embodiments of this application, as shown in FIG1, the control method of the brushless motor control system includes: a power modulation system 10 for providing DC power to the brushless motor; 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; and a power factor correction unit 12 connected in parallel between the first output terminal 11A and the second output terminal 11B. The power modulation system 10 also includes a filtering unit 13, which has a third capacitor element 131 and a switching element 132, and is connected in parallel between the first output terminal 11C and the second output terminal 11D. The brushless power tool control method includes: when the brushless motor 20 is in a first operating state, the control unit 30 controls the switching element 132 to be turned on, thereby connecting the third capacitor element 131 in parallel between the first output terminal 11C and the second output terminal 11D; when the brushless motor 20 is in a second operating state, the control unit 30 controls the switching element 132 to be turned off, thereby putting the third capacitor element 131 in a non-operating state. This achieves improved power factor during high-speed operation of the brushless power tool while ensuring torque output during low-speed operation of the brushless motor, thus reducing motor copper losses.
[0082] In some alternative implementations, the control unit 30 can directly control the switching element 132. In other alternative implementations, the control unit 30 can also be controlled by the switch driving unit 133. This is readily apparent to those skilled in the art and will not be elaborated upon here.
[0083] In some alternative implementations, the first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.
[0084] In the above embodiments proposed in this application, the switching element 132 can be a thyristor, a MOSFET, an IGBT, or a gallium nitride, and there is no limitation. Of course, it can also be other switching elements known to those skilled in the art, which will not be described in detail here.
[0085] In the embodiments proposed in this application, the switch driving unit can be a switch driving integrated circuit or a microcontroller control unit. For those skilled in the art, it is easy to conceive of selecting the corresponding switch driving unit based on different types of switching elements, and will not be elaborated here.
[0086] 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.
[0087] 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.
[0088] The above-described specific embodiments are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications, substitutions, and improvements made by those skilled in the art to the technical solutions of this application based on the textual description and drawings provided herein, without departing from the design concept and spirit of this application, should all fall within the scope of protection of this application. The scope of protection of this application is determined by the claims.
Claims
1. A power modulation system, comprising: A rectification 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 rectification unit is used to convert AC electrical energy into DC electrical energy; A power factor correction unit connected in parallel between the first output terminal and the second output terminal; Wherein, the power modulation system further includes a filtering unit having a third capacitive element and a switching element, and is connected in parallel between the first output terminal and the second output terminal.
2. The power modulation system according to claim 1, wherein, The power factor correction unit has a first capacitive element, a second capacitive element, a first diode element, a second diode element and a third diode element. The first capacitive element and the first diode element are connected in series and are connected in parallel between the first output terminal and the second output terminal; the second capacitive element and the second diode element are connected in series and are connected in parallel between the first output terminal and the second output terminal; the third diode element is connected in series between the first capacitive element and the second capacitive element.
3. The power modulation system according to claim 2, wherein, The filtering unit further has a switching drive unit, which is used to drive the switching element to conduct in a first operating state, so that the third capacitive element is connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switching element to disconnect in a second operating state, so that the third capacitive element is in a non-operating state.
4. The power modulation system according to claim 2, wherein, The filtering unit further has a switching drive unit and an inductive element. The inductive element is connected in series with the third capacitive element. The switching drive unit is used to drive the switching element to conduct in a first operating state, so that the third capacitive element and the inductive element are connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switching element to disconnect in a second operating state, so that the third capacitive element and the inductive element are in a non-operating state.
5. The power modulation system according to claim 3 or 4, wherein, The capacitance value of the third capacitive element is greater than or equal to the capacitance value of the first capacitive element and the second capacitive element connected in series.
6. A brushless power tool, comprising: A brushless motor provided with a position sensing unit; A power modulation system for providing DC electrical energy to the brushless motor; A control unit for providing a control signal to control the brushless motor; A motor drive unit for receiving the control signal of the control unit and sending a drive signal based on the control signal to drive the brushless motor; A motor switching unit for receiving the drive signal of the motor drive unit and switching the connection between the power modulation system and the brushless motor; Wherein, the power modulation system includes: A rectification 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 rectification unit is used to convert AC electrical energy into DC electrical energy; A power factor correction unit connected in parallel between the first output terminal and the second output terminal; The power modulation system further includes a filtering unit, which has a third capacitor element and a switching element, and is connected in parallel between the first output terminal and the second output terminal.
7. The brushless power tool according to claim 6, wherein, The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a second diode element, and a third diode element. The first capacitor element and the first diode 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 diode element are connected in series and connected in parallel between the first output terminal and the second output terminal. The third diode element is connected in series between the first capacitor element and the second capacitor element.
8. The brushless power tool according to claim 7, wherein, The filtering unit also has a switch driving unit, which is used to drive the switch element to conduct in a first operating state, so that the third capacitor element is connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switch element to disconnect in a second operating state, so that the third capacitor element is in a non-operating state.
9. 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 modulation system further includes a filtering unit, which has a third capacitor element and a switching element, and is connected in parallel between the first output terminal and the second output terminal; The brushless power tool control method includes: When the brushless motor is in the first operating state, the control unit controls the switching element to be turned on, thereby connecting the third capacitor element in parallel between the first output terminal and the second output terminal. When the brushless motor is in the second operating state, the control unit controls the switching element to open, thereby putting the third capacitor element in a non-operating state.
10. The brushless power tool control method according to claim 9, wherein, The first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.
11. 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 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 modulation system further includes a filtering unit, which has a third capacitor element and a switching element, and is connected in parallel between the first output terminal and the second output terminal.
12. The brushless motor control system according to claim 11, wherein, The power factor correction unit includes a first capacitor element, a second capacitor element, a first diode element, a second diode element, and a third diode element. The first capacitor element and the first diode 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 diode element are connected in series and connected in parallel between the first output terminal and the second output terminal. The third diode element is connected in series between the first capacitor element and the second capacitor element.
13. The brushless motor control system according to claim 12, wherein, The filtering unit also has a switch driving unit, which is used to drive the switch element to conduct in a first operating state, so that the third capacitor element is connected in parallel between the first output terminal and the second output terminal, and is also used to drive the switch element to disconnect in a second operating state, so that the third capacitor element is in a non-operating state.
14. The brushless motor control system according to claim 12, wherein, The filtering unit also includes a switch driving unit and an inductor. The inductor is connected in series with the third capacitor. The switch driving unit is used to drive the switch to conduct in a first operating state, so that the third capacitor and the inductor are connected in parallel between the first output terminal and the second output terminal. It is also used to drive the switch to disconnect in a second operating state, so that the third capacitor and the inductor are in a non-operating state.
15. The brushless motor control system according to claim 13 or 14, wherein, The capacitance of the third capacitor element is greater than or equal to the capacitance of the first capacitor element and the second capacitor element connected in series.
16. The brushless motor control system according to claim 11, wherein, The control unit is also used to control the switch drive unit.
17. 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 modulation system further includes a filtering unit, which has a third capacitor element and a switching element, and is connected in parallel between the first output terminal and the second output terminal; The control method of the brushless motor control system includes: When the brushless motor is in the first operating state, the control unit controls the switching element to be turned on, thereby connecting the third capacitor element in parallel between the first output terminal and the second output terminal. When the brushless motor is in the second operating state, the control unit controls the switching element to open, thereby putting the third capacitor element in a non-operating state.
18. The control method of the brushless motor control system according to claim 17, wherein, The first operating state is a low-speed operating state, and the second operating state is a high-speed operating state.