Power tool and three-phase motor control device and method thereof

Abstract

The present invention provides an electric tool (100) and a control device and method for a three-phase motor (10). The control device (20) includes: a switch unit (21) configured to include a first switch unit and a second switch unit, wherein the first switch unit and the second switch unit respectively include a plurality of switch elements corresponding to each phase of a motor drive circuit, and each switch element of the first switch unit is connected in series with a corresponding switch element of the second switch unit; and a control unit (22) configured to be electrically connected to the switch unit and generate a first control signal for controlling the switching state of each switch element to realize a first braking mode of the three-phase motor, wherein, under the control of the first control signal, each switch element of the first switch unit is turned off, and in each sub-period interval of an electrical cycle, the switch element in the second switch unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switch elements in the second switch unit are turned on.

Description

Technical Field

[0001] The present application generally relates to the technical field of motor control, and more particularly to a control device for a motor for a power tool, a power tool including the control device, and a corresponding control method. Background Art

[0002] Three-phase motors are widely used in power tools, converting electrical energy into mechanical energy to provide driving force. As a three-phase motor transitions from running to braking and then to a stop, the motor's operating energy needs to be dissipated. This is achieved through a motor braking solution. Existing motor braking solutions typically utilize power switching devices and capacitors to dissipate the motor's energy. However, existing motor braking solutions present the problem of energy returning to the power tool's battery or power supply.

[0003] According to existing motor braking solutions, a typical power tool, a DC-EC cordless power tool, uses a battery as its power source. DC-EC cordless power tools often start and stop frequently, requiring the motor to be frequently started and stopped. Frequent motor braking, and the resulting high energy return to the battery during braking, significantly shortens battery life.

[0004] According to the aforementioned existing motor braking solutions, another typical power tool, AC-EC corded power tools, is typically implemented in a compact size, which limits the use of larger capacitors. When using smaller capacitors, the capacitors typically have a smaller capacitance, thus only dissipating a limited amount of motor energy. A significant amount of energy can still be returned to the power tool's power supply, potentially damaging the power tool or its power switch.

[0005] Therefore, a technical solution to overcome the above-mentioned defects is urgently needed. Summary of the Invention

[0006] The following summary is provided to introduce selected concepts in a simplified form that are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0007] According to a first aspect of the present invention, a control device for a three-phase motor for an electric tool is provided, comprising: a switching unit configured to include a first switching unit and a second switching unit, the first switching unit and the second switching unit respectively including a plurality of switching elements corresponding to each phase of the three-phase motor drive circuit, each switching element of the first switching unit being connected in series with a corresponding switching element of the second switching unit, and both being electrically connected to one phase of the three-phase motor drive circuit respectively; and a control unit configured to be electrically connected to the switching unit and to generate a first control signal for controlling the switching state of each switching element to realize a first braking mode of the three-phase motor, wherein, under the control of the first control signal, each switching element of the first switching unit is turned off, and in each sub-period interval of the electrical cycle, the switching element in the second switching unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switching elements in the second switching unit are turned on.

[0008] According to a feasible embodiment, each electrical cycle includes six sub-cycles, and in each electrical cycle in the first braking mode, under the control of the first control signal: in the first and sixth sub-cycle intervals, the switching element corresponding to U in the second switching unit is turned off, and the switching element corresponding to V phase and W is turned on; in the second and third sub-cycle intervals, the switching element corresponding to V in the second switching unit is turned off, and the switching element corresponding to U phase and W is turned on; in the fourth and fifth sub-cycle intervals, the switching element corresponding to W in the second switching unit is turned off, and the switching element corresponding to U phase and V is turned on.

[0009] According to a feasible implementation manner, each of the six sub-periods is a 60° interval.

[0010] According to a feasible embodiment, the control unit is further configured to: from the moment when the first braking mode is executed for a certain period of time so that the operating energy of the three-phase motor is consumed by a predetermined percentage, until the three-phase motor is braked, generate a second control signal for controlling the switching state of each switching element to realize the second braking mode of the three-phase motor, wherein, under the control of the second control signal, each switching element of the first switching unit is turned off, and each switching element of the second switching unit is periodically turned on or is always turned on.

[0011] According to a feasible embodiment, the control unit is also configured to generate a third control signal for controlling the switching state of each switching element before the first braking mode is executed to realize the third braking mode of the three-phase motor, and execute the first braking mode again after the third braking mode is executed for a certain period of time so that the current returning to the bus is reduced to a predetermined threshold, wherein, under the control of the third control signal, each switching element of the first switching unit is turned off, and in each sub-cycle interval of the electrical cycle, the switching element in the second switching unit corresponding to one of the motors is turned on, and the switching elements in the second switching unit corresponding to the other two are turned off.

[0012] According to a feasible embodiment, the control unit is further configured to set an advanced conduction angle for the switching element to be turned on in the second switching unit, and the advanced conduction angle is greater than 0° and less than or equal to 60°.

[0013] According to a feasible implementation manner, the control unit is configured to determine one or more of the first to third braking modes based on the braking requirements of the three-phase motor in actual application, and determine the execution duration and execution order of the adopted braking modes; the braking requirements include one or more of the braking current, the return bus current and the braking duration; and the first braking mode is a dual downtube braking mode, the second braking mode is a maximum braking current mode, and the third braking mode is a single downtube braking mode.

[0014] According to a possible embodiment, the switching elements of the switching units constitute a bridge inverter, the switching elements of the first switching unit constitute an upper arm of the bridge inverter, and the switching elements of the second switching unit constitute a lower arm of the bridge inverter.

[0015] According to a second aspect of the present invention, a control device for a three-phase motor for an electric tool is provided, comprising: a switch unit, configured to include a first switch unit and a second switch unit, the first switch unit and the second switch unit respectively including a plurality of switch elements corresponding to each phase of a three-phase motor drive circuit, each switch element of the first switch unit being connected in series with a corresponding switch element of the second switch unit, and both being electrically connected to one phase of the three-phase motor drive circuit; and a control unit (22), configured to be electrically connected to the switch unit and to generate a first control signal for controlling the switching state of each switch element to realize a first control of the three-phase motor. In the first braking mode, each electrical cycle includes six sub-cycles, and in each electrical cycle in the first braking mode, under the control of the first control signal: the switching elements of the first switching unit are turned off; in the first and sixth sub-cycle intervals, the switching elements corresponding to U in the second switching unit are turned off, and the switching elements corresponding to V phase and W are turned on; in the second and third sub-cycle intervals, the switching elements corresponding to V in the second switching unit are turned off, and the switching elements corresponding to U phase and W are turned on; in the fourth and fifth sub-cycle intervals, the switching elements corresponding to W in the second switching unit are turned off, and the switching elements corresponding to U phase and V are turned on.

[0016] According to a possible implementation manner, each of the six sub-periods is a 60° interval.

[0017] According to a third aspect of the present invention, there is provided an electric tool comprising: a three-phase motor; and a braking device as described in the first or second aspect above, which is electrically connected to the three-phase motor and comprises a switch and a control unit, the control unit generating a control signal for controlling each switching element of the switching unit so that the three-phase motor realizes one or more of the first to third braking modes, wherein the first braking mode is a dual downtube braking mode, the second mode is a maximum braking current mode or a PWM chopping braking mode, and the third braking mode is a single downtube braking mode.

[0018] According to a fourth aspect of the present invention, a control method for a three-phase motor for an electric tool is provided. Optionally, the method is implemented in a control device as described in the first aspect and / or an electric tool as described in the third aspect. The electric tool includes a three-phase motor and a switch unit, the switch unit is electrically connected to the motor to supply current to it, the switch unit includes a first switch unit and a second switch unit, the first switch unit and the second switch unit respectively include a plurality of switch elements corresponding to each phase of the three-phase motor drive circuit, each switch element of the first switch unit is respectively connected in series with a corresponding switch element of the second switch unit, and both are respectively electrically connected to a phase of the three-phase motor drive circuit, the method includes: generating a first control signal for controlling the switching state of each switch element to realize a first braking mode of the three-phase motor, wherein, under the control of the first control signal, each switch element of the first switch unit is turned off, and in each sub-period interval of the electrical cycle, the switch element in the second switch unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switch elements in the second switch unit are turned on.

[0019] According to a fifth aspect of the present invention, a control method for a three-phase motor for an electric tool is provided. Optionally, the method is implemented in the control device as described in the second aspect and / or the electric tool as described in the third aspect. The electric tool includes a three-phase motor and a switch unit. The switch unit is electrically connected to the motor to supply current to it. The switch unit includes a first switch unit and a second switch unit. The first switch unit and the second switch unit respectively include a plurality of switch elements corresponding to each phase of the three-phase motor drive circuit. Each switch element of the first switch unit is respectively connected in series with a corresponding switch element of the second switch unit, and both are respectively electrically connected to a phase of the three-phase motor drive circuit. The method includes: generating a control circuit for controlling A first control signal for the switching state of each switching element is used to realize a first braking mode of the three-phase motor, wherein each electrical cycle includes six sub-cycles, and in each electrical cycle in the first braking mode, under the control of the first control signal: each switching element of the first switching unit is turned off; in the first and sixth sub-cycle intervals, the switching element corresponding to U in the second switching unit is turned off, and the switching element corresponding to V phase and W is turned on; in the second and third sub-cycle intervals, the switching element corresponding to V in the second switching unit is turned off, and the switching element corresponding to U phase and W is turned on; in the fourth and fifth sub-cycle intervals, the switching element corresponding to W in the second switching unit is turned off, and the switching element corresponding to U phase and V is turned on. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of an electric tool according to a possible embodiment of the present invention is shown.

[0021] Figure 2 Shown Figure 1 An implementation of a control device for an electric tool.

[0022] Figure 3 shows different braking modes according to an embodiment of the present invention, Figure 2 The switching status diagram of each switching element of the control device.

[0023] Figure 4 A flow chart of a control method according to a possible embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] Considering that the existing technical solutions cannot prevent the electric motor of the power tool from returning energy to the battery / power supply of the power tool during the braking process, an embodiment of the present invention proposes an improved motor braking control scheme, which has good performance in both expected higher braking efficiency (for example, larger braking current and shorter braking time) and expected current returned to the power supply / battery of the power tool is almost zero.

[0025] The braking control scheme according to the embodiment of the present invention is applicable to various types of three-phase motors. For example, the back electromotive force waveform of the three-phase motor can be a sine wave, a triangle wave, a trapezoidal wave, and so on.

[0026] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0027] Figure 1 A power tool 100 according to a possible embodiment of the present invention is schematically shown, which mainly includes a three-phase motor 10 and a control device 20 .

[0028] The three-phase motor 10 is disposed inside the housing of the power tool 100. The three-phase motor 10 serves as a driving component of the power tool 100 and provides power to the power tool 100 when powered on. The three-phase motor 10 is, for example, a three-phase brushless DC motor.

[0029] The control device 20 is disposed inside the housing of the power tool 100 and is electrically connected to the three-phase motor 10. The control device 20 mainly includes a switch unit 21 and a control unit 22.

[0030] See also Figure 2The switch unit 21 is connected between the power supply of the motor 10 and the motor to enable or disable the power supply current from being output to the motor. The switch unit 21 may include multiple switching elements, which may form a bridge inverter. The switch unit 21 may be part of the drive circuit of the three-phase motor 10. For example, the drive circuit of the motor 10 may include the multiple switching elements of the switch unit forming an inverter circuit, as well as a boost circuit, a filter circuit, and the like.

[0031] In one embodiment, the switching unit 21 includes six switching elements T1-T6, forming a three-phase bridge inverter. Every two switching elements T1 and T2, T3 and T4, and T5 and T6 are connected in series. The connection points between the switching elements T1 and T2, T3 and T4, and T5 and T6 are each electrically connected to a phase of the three-phase motor 10. For example, the connection point between the switching elements T1 and T2 is electrically connected to the U phase; the connection point between the switching elements T3 and T4 is electrically connected to the V phase; and the connection point between the switching elements T5 and T6 is electrically connected to the W phase.

[0032] In this embodiment, switching elements T1, T3, and T5 constitute a first switching unit, i.e., the upper arm of the bridge inverter; switching elements T2, T4, and T6 constitute a second switching unit, i.e., the lower arm of the bridge inverter. Switching elements T1-T6 can each be implemented as a power transistor and a diode connected in parallel therewith.

[0033] The control unit 22 generates control signals for controlling the switching states of the switching elements. For example, the control unit 22 generates control signals X1 to X6 for controlling the switching states (on and off) of the switching elements T1 to T6, respectively, and outputs the control signals X1 to X6 to the control terminals of the switching elements T1 to T6, respectively.

[0034] In one embodiment, the control unit 22 may be provided in a microcontroller of a drive control system of the motor 10. The drive control system may include the aforementioned drive circuit and microcontroller.

[0035] The control unit 22 can be implemented in hardware, software, or a combination of software and hardware. For hardware-implemented portions, these can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic units designed to perform their functions, or combinations thereof. For software-implemented portions, these can be implemented with the aid of microcode, program code, or code segments, and can also be stored in a machine-readable storage medium such as a storage component.

[0036] In one embodiment, the control unit 22 is implemented as a unit including a memory and a processor. The memory contains instructions, which, when executed by the processor, enable the processor to perform the brake control logic / brake control method according to an embodiment of the present invention.

[0037] The control unit 22 can generate control signals X1 to X6 for controlling the switch units T1 to T6, respectively, and different combinations of the control signals X1 to X6 can implement different braking modes of the three-phase motor 10. For example, the first to third control signals are used to implement the first to third braking modes, respectively. For example, the control signal can be implemented to have a high level and a low level, and the switch element is turned on under the control of the high-level control signal and turned off under the control of the low-level control signal. Of course, the correspondence between the control signal and the switch state can also be other ways, and is not limited to this.

[0038] Below, reference Figure 3 Introduce these control signals and braking modes.

[0039] First, it should be noted that, in the embodiment of the present invention, one electrical cycle is divided into six sub-cycles each having a duration of T / 6 (see Figure 3 (intervals demarcated by dashed lines in the figure), that is, each sub-period of an electrical cycle (0-360°) corresponds to a 60° interval. In other words, an electrical cycle includes the following six sub-periods: 0°-60° interval, 60°-120°, 120°-180°, 180°-240°, 240°-300°, and 300°-360°. In one embodiment, the 0°-360° electrical cycle can be divided into six 60° intervals using a signal containing back electromotive force (BEMF) information, such as the motor's rotor position signal (Hall signal).

[0040] It can be understood that the time period from the start of braking to the complete stop (brake stop) of the three-phase motor 10 may include several complete electrical cycles, or may include several complete electrical cycles and one incomplete electrical cycle, that is, the last electrical cycle before the motor stops may be incomplete.

[0041] Figure 3(a) shows the state diagram of the switching elements T1 to T6 when the motor 10 is in a continuous rotation state. This switching state can be understood as a six-step commutation operation state. Specifically, under the control of the control signals X1 to X6, in the range of 0°-60°, the switching elements T1 and T4 are turned on (working); in the range of 60°-120°, the switching elements T4 and T5 are turned on; in the range of 120°-180°, the switching elements T2 and T5 are turned on; in the range of 180°-240°, the switching elements T2 and T3 are turned on; in the range of 240°-300°, the switching elements T3 and T6 are turned on; in the range of 300°-360°, the switching elements T1 and T6 are turned on. The phases are commutated in this way to achieve continuous rotation of the motor 10.

[0042] Figure 3 (b) shows an embodiment of the switching states of the switching elements T1 to T6 for realizing the first braking mode.

[0043] In the first braking mode, under the control of the first control signal, each switching element is configured so that the lower-arm switch corresponding to the phase with the highest back EMF during motor braking is always off. That is, during each sub-cycle, the lower-arm switch corresponding to the phase with the highest back EMF is off, while the other two lower-arm switches corresponding to the phase with the highest back EMF are on. Therefore, the first braking mode can be understood as a dual-lower-arm braking mode.

[0044] See also Figure 3 (b) takes an electrical cycle of 0°-360° as an example to illustrate the on and off logic of each switch in the first braking mode.

[0045] During the 0-360° period, the switching elements of the upper bridge arm, namely, switching elements T1, T3, and T5, are turned off (stopped working). In the 0-60° range, switching elements T4 and T6 are turned on (working), and switching element T2 is turned off (not working); in the 60-120° range, switching elements T2 and T4 are turned on, and switching element T6 is turned off; in the 120-180° range, switching elements T2 and T4 are turned on, and switching element T6 is turned off; in the 180-240° range, switching elements T2 and T6 are turned on, and switching element T4 is turned off; in the 240-300° range, switching elements T2 and T6 are turned on, and switching element T4 is turned off; in the 300-360° range, switching elements T4 and T6 are turned on, and switching element T2 is turned off. This commutation is repeated to achieve continuous braking of the motor 10.

[0046] In the first braking mode, the lower-arm switch corresponding to the maximum forward back EMF is always inactive. Specifically, in the 0°-60° range, the maximum back EMF (BEMF) of the U phase is avoided; in the 60°-120° range, the maximum back EMF of the V phase is avoided; in the 120°-180° range, the maximum back EMF of the V phase is avoided; in the 180°-240° range, the maximum back EMF of the W phase is avoided; in the 240°-300° range, the maximum back EMF of the W phase is avoided; and in the 300°-360° range, the maximum back EMF of the U phase is avoided.

[0047] In the first braking mode, since the switch of the upper bridge arm is always turned off (Off) during the braking process, the power supply of the power tool is isolated from the upper bridge arm switch of the motor 10 that is turned off, and the braking current is only caused by the back electromotive force acting on the three-phase winding of the motor, and the maximum back electromotive force in the corresponding sub-cycle interval is avoided.

[0048] Figure 3 (c) and (d) respectively show embodiments of the switching states of the switching elements T1 to T6 for implementing the second braking mode. In the second braking mode, under the control of the second control signal, the switching elements of the lower bridge arm are periodically turned on or always turned on.

[0049] In one embodiment of the second braking mode, see Figure 3 (c) , taking an electrical cycle of 0°-360° as an example, the on and off logic of each switch is explained.

[0050] During the period of 0°-360°, the switching elements of the upper bridge arm, that is, the switching elements T1, T3 and T5 are turned off (stop working). During the period of 0°-360°, the switching elements of the lower bridge arm, that is, the switching elements T2, T4 and T6 operate in PWM chopping mode. Therefore, the second braking mode of this embodiment can be understood as a PWM chopping braking mode. Specifically, under the control of the second control signal, the On-Off states of the switching elements T2, T4 and T6 are alternated. During the On state of the switching elements T2, T4 and T6, the back electromotive force acts on the three-phase winding of the motor to cause a braking current; during the Off state of the switching elements T2, T4 and T6, the three-phase winding current is fed back to the DC side through the reverse freewheeling diodes of the switching elements T1, T3 and T5, causing the DC side voltage to increase.

[0051] In another embodiment of the second braking mode, see Figure 3 (d) takes an electrical cycle of 0°-360° as an example to illustrate the on and off logic of each switch.

[0052] Under the control of the second control signal, during the period of 0°-360°, the switching elements of the upper bridge arm, that is, switching elements T1, T3 and T5, are turned off (stop working). During the period of 0°-360°, the switching elements of the lower bridge arm, that is, switching elements T2, T4 and T6, are always on (working), and the three-phase back electromotive force acts on the three-phase winding of the motor and generates a braking current. In this case, the braking current is the largest and the braking speed is the fastest, but there is a risk of burning the power switching device due to excessive braking current. Therefore, the second braking mode of this embodiment can be understood as the maximum braking current mode.

[0053] Figure 3 (e) and (f) respectively show embodiments of the switching states of the switching elements T1 to T6 for implementing the third braking mode. In the third braking mode, each switching element of the lower bridge arm is turned on in sequence, so the third braking mode can be understood as a single lower tube braking mode.

[0054] In one embodiment of the third braking mode, see Figure 3 (e) , taking an electrical cycle of 0°-360° as an example, the on and off logic of each switch is explained.

[0055] Under the control of the third control signal, during the period from 0° to 360°, the switching elements of the upper bridge arm, i.e., the switching elements T1, T3, and T5, are turned off (stop working). During the period from 0° to 360°, the conduction state and order of the switching elements of the lower bridge arm, i.e., the switching elements T2, T4, and T6, are the same as those during normal operation of the motor (i.e., the same as the conduction state of the lower bridge arm). Figure 3 (a)). Specifically, in the range of 0°-120°, switch element T4 is on (operating); in the range of 120°-240°, switch element T2 is on; and in the range of 240°-360°, switch element T6 is on. In this embodiment, the conduction state and sequence of the switching elements in the lower bridge arm are the same as during normal operation. Because the switching elements in the upper bridge arm are off (not operating), the motor is in a coasting state, and the three-way back electromotive force of the winding does not generate a braking current.

[0056] In another embodiment of the third braking mode, see Figure 3 (f) This embodiment differs from the above embodiment of the third braking mode in that the control unit 22 sets an advance conduction angle for each switching element of the lower bridge arm, and the range of the advance conduction angle is between 0° and 60°, for example, greater than 0° and less than or equal to 60°. After the advance conduction angle is set, the three-phase back electromotive force of the winding acts on the winding through the switching elements of the lower bridge arm within the advance conduction interval, generating a braking current. Since the advance conduction angle is in the range of 0°-60°, it can be ensured that before the next commutation state arrives, the above embodiment ( Figure 3(e) embodiment), at this time, the three-phase back electromotive force of the winding does not generate a braking current, thereby ensuring that the winding current will not be fed back to the power supply of the power tool through the reverse freewheeling diode of the switching element of the upper bridge arm during phase change.

[0057] See also Figure 3 (f) , taking an electrical cycle of 0°-360° as an example to illustrate the on and off logic of each switch.

[0058] The advanced conduction angle is set to 60 degrees. Under the control of the third control signal, the switching elements of the upper bridge arm, namely, switching elements T1, T3, and T5, are turned off (stopped working) during the period of 0°-360°. Switching element T4 is turned on (working) during the period of 0°-60°; switching element T2 is turned on during the period of 60°-180°; switching element T6 is turned on during the period of 180°-300°; and switching element T4 is turned on during the period of 300°-360°.

[0059] According to an embodiment of the present invention, the control unit 22 may determine to adopt one or more of the above braking modes based on the actual application requirements for motor braking, and determine the execution duration and execution order of the adopted braking modes.

[0060] Requirements for motor braking may include the following aspects: (1) Bus return current. For example, the current returning to the power supply / battery side of the power tool during braking cannot exceed a predetermined threshold (for example, monitoring and detecting the returned bus current). (2) Braking current. For example, the braking current cannot be less than a predetermined threshold (for example, detecting the returned phase line current). (3) Braking duration. For example, the braking time cannot be too long.

[0061] Below, reference Figure 4 The control method according to an embodiment of the present invention is described below. The control method can be executed in the control device 20, for example, by the control unit 22. Therefore, the above description is also applicable here and will not be repeated.

[0062] In one embodiment, in box 402, the control unit 22 generates a first control signal for controlling the switching state of each switching element to realize the first braking mode of the three-phase motor 10, wherein, under the control of the first control signal, each switching element of the first switching unit is turned off, and in each sub-period interval of the electrical cycle, the switching element in the second switching unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switching elements in the second switching unit are turned on.

[0063] In this embodiment, each electrical cycle includes six equal sub-cycles, and in each electrical cycle in the first braking mode, under the control of the first control signal: in the first and sixth sub-cycle intervals, the switching element corresponding to U in the second switching unit is turned off, and the switching element corresponding to V phase and W is turned on; in the second and third sub-cycle intervals, the switching element corresponding to V in the second switching unit is turned off, and the switching element corresponding to U phase and W is turned on; in the fourth and fifth sub-cycle intervals, the switching element corresponding to W in the second switching unit is turned off, and the switching element corresponding to U phase and V is turned on.

[0064] In another embodiment, it is desired to shorten the braking time relative to the above embodiment, that is, to stop the motor faster, and the second braking mode may be executed after executing the first braking mode, that is, box 403 may be executed after box 402, because the braking current in the second braking mode is larger, thereby shortening the braking time.

[0065] In this embodiment, one of the above two embodiments of the second braking mode can be selectively adopted according to actual application conditions and requirements for braking time, that is, one of the PWM chopping braking mode and the maximum braking current mode.

[0066] In this embodiment, from the moment after box 402 (i.e., the first braking mode) is executed for a certain period of time so that the operating energy of the three-phase motor is consumed by a predetermined percentage (e.g., 60%) (i.e., most of the operating energy of the motor has been consumed), until the stage when the motor is braked, a second control signal is generated for controlling the switching state of each switching element to realize the second braking mode of the three-phase motor, wherein, under the control of the second control signal, each switching element of the first switching unit is turned off, and each switching element of the second switching unit is periodically turned on or is always turned on.

[0067] In another embodiment, it is hoped that the returned bus current will never be too large, that is, it is hoped that the energy returned to the battery / power supply of the power tool will be limited to a smaller range in the initial stage when the motor starts braking. The third braking mode can be executed before executing the first braking mode, that is, box 403 is executed before executing box 402, because the returned bus current in the first braking mode is extremely small (almost zero).

[0068] In this embodiment, before the first braking mode is executed, a third control signal is generated for controlling the switching state of each switching element to realize the third braking mode of the three-phase motor, and the first braking mode is executed after the third braking mode is executed for a certain period of time so that the current returning to the bus is reduced to a predetermined threshold value, wherein, under the control of the third control signal, each switching element of the first switching unit is turned off, and in each sub-cycle interval of the electrical cycle, the switching element in the second switching unit corresponding to one of the motors is turned on, and the switching elements in the second switching unit corresponding to the other two are turned off.

[0069] It will be appreciated that the above description of a possible braking process is merely illustrative, and that the braking process according to embodiments of the present invention may also be implemented as other combinations of the first, second, and third braking modes. For example, the third braking mode may be executed in the initial stages of motor braking, the first braking mode may be executed when the return bus current is nearly zero, and the second braking mode may be executed after most of the motor's operating energy has been consumed, thereby enabling the motor to quickly stop after most of its operating energy has been consumed.

[0070] It is understandable that the three-phase motor control device / control method according to the embodiment of the present invention can also be applied to other devices or systems that require both braking efficiency and almost zero current returned to the power supply / battery.

[0071] The present invention also provides a machine-readable storage medium storing executable instructions, which, when executed, enable one or more processors to perform the above control method.

[0072] It is understandable that although Figure 1 The power tool 100 shown in the example may be a machine tool such as a drill or a hammer, but the power tool according to an embodiment of the present invention may also be other types of machine tools, for example, the above-mentioned other devices or systems suitable for adopting the control device / method according to an embodiment of the present invention.

[0073] Although some embodiments have been described above, these embodiments are given by way of example only and are not intended to limit the scope of the present application. The appended claims and their equivalents are intended to cover all modifications, substitutions and changes made within the scope and spirit of the present application.

Claims

1. A control device (20) for a three-phase motor (10) for an electric tool (100), comprising: A switch unit (21) is configured to include a first switch unit and a second switch unit, wherein the first switch unit and the second switch unit respectively include a plurality of switch elements corresponding to each phase of a three-phase motor drive circuit, each switch element of the first switch unit is connected in series with a corresponding switch element of the second switch unit, and both are electrically connected to one phase of the three-phase motor drive circuit; as well as a control unit (22) configured to be electrically connected to the switch unit and to generate a first control signal for controlling the switching state of each switch element to achieve a first braking mode of the three-phase motor (10); In which, under the control of the first control signal, each switching element of the first switching unit is turned off, and in each sub-cycle interval of the electrical cycle, the switching element in the second switching unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switching elements in the second switching unit are turned on.

2. The control device (20) according to claim 1, wherein: Each electrical cycle includes six sub-cycles, and in each electrical cycle in the first braking mode, under the control of the first control signal: During the first and sixth sub-periods, the switching element corresponding to phase U in the second switching unit is turned off, and the switching elements corresponding to phase V and phase W are turned on; During the second and third sub-periods, the switching element corresponding to V in the second switching unit is turned off, and the switching elements corresponding to U phase and W are turned on; In the fourth and fifth sub-periods, the switch element corresponding to W in the second switch unit is turned off, and the switch elements corresponding to U phase and V are turned on. Optionally, each of the six sub-periods is a 60° interval.

3. The control device (20) according to claim 1, wherein: The control unit (22) is further configured to: generate a second control signal for controlling the switching state of each switching element from the moment the first braking mode is executed for a certain period of time so that the operating energy of the three-phase motor (10) is consumed by a predetermined percentage until the three-phase motor (10) is braked to a stop, so as to realize the second braking mode of the three-phase motor (10); Wherein, under the control of the second control signal, each switching element of the first switching unit is turned off, and each switching element of the second switching unit is periodically turned on or is always turned on.

4. The control device (20) according to claim 1, wherein: The control unit (22) is further configured to generate a third control signal for controlling the switching state of each switching element before the first braking mode is executed to implement a third braking mode of the three-phase motor (10), and to execute the first braking mode after the third braking mode is executed for a certain period of time so that the current returning to the busbar is reduced to a predetermined threshold value. In which, under the control of the third control signal, each switching element of the first switching unit is turned off, and in each sub-period interval of the electrical cycle, the switching element in the second switching unit corresponding to one of the motors is turned on, and the switching elements in the second switching unit corresponding to the other two are turned off.

5. The control device (20) according to claim 4, wherein: The control unit (22) is further configured to set an advanced conduction angle for the switch element to be turned on in the second switch unit, wherein the advanced conduction angle is greater than 0° and less than or equal to 60°.

6. The control device (20) according to claim 1, wherein: The control unit (22) is configured to determine one or more of the first to third braking modes according to actual application braking requirements for the three-phase motor (10), and to determine the execution duration and execution order of the adopted braking modes; The braking requirement includes one or more of a braking current, a return bus current, and a braking duration; and The first braking mode is a dual downtube braking mode, the second braking mode is a maximum braking current mode, and the third braking mode is a single downtube braking mode.

7. The control device (20) according to claim 1, wherein: The switching elements of the switching unit (21) constitute a bridge inverter, the switching elements of the first switching unit constitute an upper arm of the bridge inverter, and the switching elements of the second switching unit constitute a lower arm of the bridge inverter.

8. An electric tool (100), comprising: Three-phase electric motor (10); as well as The control device (20) according to any one of claims 1 to 7 is electrically connected to the three-phase motor (10), and comprises a switch unit and a control unit, wherein the control unit generates a control signal for controlling each switching element of the switch unit.

9. A method for controlling a three-phase motor for an electric tool, the method being implemented in a control device according to any one of claims 1 to 7 and / or an electric tool according to claim 8, the electric tool comprising a three-phase motor and a switch unit, the switch unit being electrically connected to the motor to supply current thereto, the switch unit comprising a first switch unit and a second switch unit, the first switch unit and the second switch unit respectively comprising a plurality of switch elements corresponding to respective phases of a three-phase motor drive circuit, each switch element of the first switch unit being connected in series with a corresponding switch element of the second switch unit, and both being electrically connected to one phase of the three-phase motor drive circuit, The method comprises: A first control signal is generated for controlling the switching state of each switching element to realize a first braking mode of the three-phase motor, wherein, under the control of the first control signal, each switching element of the first switching unit is turned off, and in each sub-period interval of the electrical cycle, the switching element in the second switching unit corresponding to the largest back electromotive force of the three-phase motor is turned off, and the other switching elements in the second switching unit are turned on.

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