Wide bandgap motor drive with field oriented control for power tools

Abstract

A power tool includes a motor and a power input. The power tool also includes a power switching network electrically connected between the power input and the motor, and a controller electrically connected to the power switching network. The power switching network includes a plurality of wide bandgap semiconductor (WBS) field effect transistors (FETs). The controller is configured to determine a motor speed of the motor; and based on the motor speed, generate a pulse width modulation (PWM) signal for the power switching network using field oriented control (FOC). A switching frequency of the PWM signal is greater than or equal to 50 kHz.

Description

[0001] Cross-reference to related applications This application claims priority to U.S. Provisional Application No. 63 / 762,871, filed February 25, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to motor drives for power tools. Background Technology

[0003] Unlike brushed motors, the rotor position can be determined to control the operation of a brushless direct current (BLDC) motor or a permanent magnet synchronous motor (PMSM). For example, the system can use sensors (e.g., Hall effect sensors), encoders (e.g., rotary encoders), or sensorless technology to detect the position of magnets in the rotor, thereby controlling the timing of the drive signals supplied to the power switching elements. BLDC and PMSM motor controllers use the motor's position to generate PWM schemes to drive the power switching network and the motor. The PWM schemes used to drive the motor vary based on techniques such as block commutation, field-oriented control, etc.

[0004] Metal-oxide-semiconductor field-effect transistors (MOSFETs) have been used as switches to form the power switching networks for power tools. MOSFETs operate at low frequencies, such as 20 kHz and similar frequencies within the range of human hearing. MOSFETs also have other drawbacks, such as slow response time and power loss due to high on-resistance. The high on-resistance of MOSFETs can also generate heat when current flows through the MOSFET during power tool operation. Larger heat sinks may be needed to dissipate this heat, leading to larger power tool sizes and increasing the challenges of power tool design.

[0005] Unlike MOSFETs, wide-bandgap semiconductor (WBS) field-effect transistors (FETs) (e.g., gallium nitride (GaN FETs), silicon carbide (SiC FETs), etc.) can operate at high switching frequencies, such as 100 kHz, 200 kHz, 400 kHz, etc., due to their construction. Compared to MOSFETs, WBS FETs have faster response times and reduced power losses due to low on-resistance. Therefore, WBS FETs can operate at frequencies beyond the range of human hearing. Furthermore, compared to MOSFETs, WBS FETs generate less heat during operation due to their low on-resistance. Using WBS FETs also allows for smoother motor control using field-oriented control (FOC) schemes, compared to MOSFETs. Summary of the Invention

[0006] In some aspects, the technology described in this invention relates to a power tool comprising: a motor; a power input; a power switching network electrically connected between the power input and the motor, the power switching network including a plurality of wide-bandgap semiconductor (WBS) field-effect transistors (FETs); and a controller electrically connected to the power switching network and configured to: determine the speed of the motor; and, based on the speed of the motor, generate a pulse width modulation (PWM) signal for the power switching network using field-oriented control (FOC), wherein the PWM signal includes a switching frequency of at least 50 kHz.

[0007] In some aspects, the technology described in this invention relates to a method for controlling a motor of a power tool, the method comprising: determining the speed of the motor using a controller of the power tool; and using the controller, generating a pulse width modulation (PWM) signal for a power switching network based on the speed of the motor from a field-oriented control (FOC), the power switching network being electrically connected between a power input of the power tool and the motor, the power switching network including a plurality of wide-bandgap semiconductor (WBS) field-effect transistors (FETs), wherein the PWM signal includes a switching frequency greater than 50 kHz.

[0008] In some aspects, the technology described in this invention relates to a power tool comprising: a power input unit; a speed change trigger; a motor including a speed sensor; a power switching network electrically connected between the power input unit and a power output unit and including a plurality of gallium nitride (GaN) high electron mobility transistors (HEMTs); and a controller electrically connected to the power switching network and configured to: receive a speed command via the speed change trigger; determine the speed of the motor using the speed sensor; and generate a pulse width modulation (PWM) signal for the power switching network from field-oriented control (FOC) based on a speed error between the speed command and the motor speed, wherein the PWM signal includes a switching frequency of at least 50 kHz.

[0009] Other aspects of the invention will become clear from the detailed description and accompanying drawings. Attached Figure Description

[0010] Figure 1 It is a perspective view of a power tool according to some implementation methods.

[0011] Figure 2 A battery pack according to some embodiments is shown.

[0012] Figure 3 It is based on some implementation methods Figure 1 A simplified block diagram of a power tool.

[0013] Figure 4 It is based on some implementation methods for Figure 1A block diagram of the control system for the power switch network of a power tool.

[0014] Figure 5 The following are examples of implementations according to some embodiments. Figure 1 A simplified block diagram of the controller topology for field-oriented control motor drive technology in power tools.

[0015] Figure 6 It is for control according to some implementation methods Figure 1 A flowchart illustrating an example method for using a motor in a power tool. Detailed Implementation

[0016] Before explaining any implementation in detail, it should be understood that the application of the implementation is not limited to the construction details and component arrangements described in the following description or shown in the following drawings. The implementation can be practiced or implemented in various ways. It should also be understood that the wording and terminology used in this invention are for illustrative purposes and should not be considered limiting. The invention uses "comprising," "including," or "having," and variations thereof to cover the items listed thereafter and their equivalents, as well as additional items. The terms "installation," "connection," and "coupling" are used broadly and cover direct and indirect installation, connection, and coupling. Furthermore, "connection" and "coupling" are not limited to physical or mechanical connections or couplings and may include direct or indirect electrical connections or couplings. Additionally, unless otherwise stated, approximate terms such as "about," "approximately," and "generally," at least when used with numerical values, may refer to within 1%, 2.5%, 5%, or 10% of the stated value.

[0017] Unless the context clearly indicates otherwise, the articles "a," "an," and "the" should not be interpreted as meaning "one" or "only one." Instead, these articles should be interpreted as meaning "at least one" or "one or more." Similarly, when the terms "the" or "said" are used to refer to a noun previously introduced by the indefinite articles "a" or "an," "the" or "said" means "at least one" or "one or more," unless the usage clearly indicates otherwise.

[0018] Furthermore, it should be understood that implementations may include hardware, software, and electronic components or modules, which may be illustrated and described as if most components were implemented solely in hardware for the purposes of discussion. However, those skilled in the art will recognize, based on reading this detailed description, that in at least one implementation, the electronic aspects may be implemented using software executable by one or more processing units (e.g., microprocessors and / or application-specific integrated circuits ("ASICs"), stored on a non-transitory computer-readable medium. Therefore, it should be noted that implementations may be implemented using a plurality of hardware and software-based devices and a plurality of different structural components. For example, "server," "computing device," "controller," "processor," etc., described in the specification may include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connectors (e.g., system buses) connecting the components.

[0019] Relative terms, such as "about," "approximately," "generally," etc., used in conjunction with quantity or condition, will be understood by those skilled in the art to include the stated value and have a meaning determined by the context (e.g., the term includes at least the degree of error associated with measurement accuracy, tolerance (e.g., tolerances related to a particular value in manufacturing, assembly, use, etc.)). Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the statement "from about 2 to about 4" also discloses a range "from 2 to 4." Relative terms can refer to a percentage added to or subtracted from an indicated value (e.g., 1%, 5%, 10%).

[0020] It should be understood that although some of the accompanying drawings show hardware and software located within a particular device, these depictions are for illustrative purposes only. The invention is described as having a function performed by one component that can be performed by multiple components in a distributed manner. Similarly, a function performed by multiple components can be combined and performed by a single component. In some embodiments, the components shown can be combined or divided into separate software, firmware, and / or hardware. For example, logic and processing can be distributed across multiple electronic processors, rather than residing within and being performed by a single electronic processor. Regardless of how they are combined or divided, hardware and software components can reside on the same computing device or be distributed among different computing devices connected via one or more networks or other suitable communication links. Similarly, components described as performing specific functions can also perform additional functions not described in this invention. For example, a device or structure "configured" in a certain way is at least configured in this manner, but can also be configured in a manner not explicitly listed.

[0021] Therefore, in a claim, if, for example, protection is sought for a device, method, or system comprising a controller, control unit, electronic processor, computing device, logic element, module, storage module, communication channel, network, or other element configured in a certain way (e.g., for performing multiple functions), then the claim or claim element should be interpreted as referring to one or more such elements, wherein any one of the one or more elements is configured as claimed, for example, to implement any one or more of the multiple functions, such that the one or more elements together perform the multiple functions as a set.

[0022] Figure 1 An example embodiment of a power tool 100 is shown. The power tool 100 is, for example, an impact actuator, which includes an upper body 110, a handle 120, a battery pack receiving portion 130, an output drive 140, and an actuator 150. The housing of the power tool 100 (e.g., the body 110 and handle 120) is constructed of a durable and lightweight plastic material. The output drive 140 is constructed of a metal (e.g., steel) output spindle. The battery pack receiving portion 130 is configured to receive and couple to a battery pack, such as a battery pack 200 that supplies power to the power tool 100. Figure 2 The battery pack receiving portion 130 includes a connection structure for engaging and securing a mechanism for fixing the battery pack 200, and includes a terminal block for electrically connecting the battery pack 200 to the power tool 100.

[0023] Figure 1 An impact actuator is shown; however, the power tool 100 may include an electric drill, circular saw, jigsaw, band saw, reciprocating saw, screwdriver, angle grinder, straight grinder, hammer drill, multi-tool, rotary hammer, angle drill, electric ratchet, electric torque wrench, hydraulic pulse tool, hydraulic tensioning tool, bolt tightening tool, reaction arm tool, riveting tool, nail gun, stapler, TC bolt gun, and portable power supply that uses an inverter to convert battery power into AC output, etc.

[0024] Figure 2A battery pack 200 according to some embodiments is shown. Battery pack 200 is a power tool battery pack typically used to power power tools such as power tool 100. Battery pack 200 includes a housing 210 and an interface portion 220 for connecting battery pack 200 to a device (e.g., power tool 100). In some embodiments, battery pack 200 includes lithium-ion battery cells. In other embodiments, battery pack 200 can be a different chemical system, such as nickel-cadmium, nickel metal hydride, etc. In the illustrated embodiment, battery pack 200 is an 18-volt battery pack. In other embodiments, the output voltage level of battery pack 200 can be different. For example, battery pack 200 can be a 4-volt battery pack, a 28-volt battery pack, a 36-volt battery pack, a 72-volt battery pack, or another voltage (the voltage here can be referred to as voltage). Battery pack 200 can also have various capacities (e.g., 3, 4, 5, 6, 8, or 12 ampere-hours).

[0025] The battery pack 200 also includes terminals for connection to the power tool 100. The terminals for the battery pack 200 include positive and negative terminals for supplying and receiving power from the battery pack 200. In some embodiments, the battery pack 200 also includes data terminals for communication with the power tool 100. For example, the battery pack 200 may include a microcontroller for monitoring one or more characteristics of the battery pack 200, and the data terminals can communicate with the power tool 100 regarding the monitored characteristics.

[0026] Figure 3 It is based on some implementation methods Figure 1 A simplified block diagram of the control system of the power tool 100 is shown. The control system includes a controller 300. The controller 300 is electrically and / or communicatively connected to various modules or components of the power tool 100. For example, the controller 300 shown is electrically connected to a position sensor 345, a power supply 310, a trigger switch 315 (connected to a trigger 320—e.g., a gear shift trigger), one or more sensors or sensing circuits 325, one or more indicators 330, a user input module 335, a power input unit 340, and a power switch network 350. The controller 300 includes a combination of hardware and software that can be operated, particularly for controlling the operation of the power tool 100, monitoring the operation of the power tool 100 using, for example, the position sensor 345 and one or more sensors or sensing circuits, activating one or more indicators 330 (e.g., LEDs), and / or similar functions.

[0027] The controller 300 includes a plurality of electrical and electronic components that provide power, operation control, and protection for components and modules within the controller 300 and / or the power tool 100. For example, the controller 300 particularly includes a processing unit 355 (e.g., a microprocessor, microcontroller, or other suitable programmable device), a memory 360, an input unit 365, and an output unit 370. The processing unit 355 particularly includes a control unit 375, an ALU 380, and a plurality of registers 385 (in... Figure 3 The controller 300 is represented as a set of registers and implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 355, memory 360, input unit 365, and output unit 370, along with various modules or circuits connected to the controller 300, are connected via one or more control and / or data buses (e.g., a common bus 390). The control and / or data buses are... Figure 3 The figures are shown in a general manner for illustrative purposes. It will be known to those skilled in the art that one or more control and / or data buses are used for interconnection and communication between various modules, circuits and components.

[0028] Memory 360 is a non-transitory computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and data storage area may include combinations of different types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, hard disk, SD card, or other suitable magnetic, optical, physical, or electronic storage devices. Processing unit 355 is connected to memory 360 and executes software instructions that can be stored in the RAM of memory 360 (e.g., during execution), the ROM of memory 360 (e.g., on a substantially permanent basis), or another non-transitory computer-readable medium (e.g., another memory or disk). Software included in an implementation of power tool 100 may be stored in memory 360 of controller 300. This software includes, for example, firmware, one or more application programs, program data, filters, rules, one or more program modules, and other executable instructions. Controller 300 is configured to retrieve from memory 360 and execute, among other things, instructions related to the control processes and methods described in this invention. In other configurations, controller 300 includes additional, fewer, or different components.

[0029] In some embodiments, the power tool 100 includes a battery pack interface (not shown) comprising a combination of mechanical components (e.g., rails, grooves, latches, etc.) and electrical components (e.g., one or more terminals), configured and usable for interfacing the power tool 100 with a power source 310 (e.g., battery pack 200) (e.g., mechanical, electrical, and communication connections). For example, power supplied to the power tool 100 by the battery pack 200 is provided to a power input 340 via the battery pack interface. The power input 340 includes a combination of active and passive components for regulating or controlling the power received from the battery pack 200 before power is supplied to the controller 300. The battery pack interface also supplies power to a power switching network 350 via the power input 340 to provide power to a motor 305. The battery pack interface also includes, for example, a communication line 395 for providing a communication line or link between the controller 300 and the battery pack 200.

[0030] Indicator 330 includes, for example, one or more light-emitting diodes ("LEDs"). Indicator 330 may be configured to display the status of power tool 100 or information associated with power tool 100. For example, indicator 330 may be configured to indicate measured electrical characteristics of power tool 100, the status of power tool 100, etc. User input module 335 is operatively coupled to controller 300 to, for example, select forward or reverse operating modes, select torque and / or speed settings for power tool 100 (e.g., using torque and / or speed switches), etc. In some embodiments, user input module 335 includes a combination of digital and analog input or output devices required to achieve a desired operating level of power tool 100, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc. Although shown separately, trigger switches 315 and / or triggers 320 may be components of user input module 335.

[0031] The power switching network 350 provides operating power to the motor 305 based on control signals from a motor controller (e.g., controller 300). The power switching network 350 includes a plurality of electronic switches (e.g., FETs, bipolar junction transistors, etc.) connected to form a network that controls the activation of the motor 305 based on pulse width modulation (PWM) signals. The power switching network 350 can be implemented as an inverter (e.g., as...). Figure 4(Examples include three-phase bridge circuits, two-phase bridge circuits such as H-bridge, etc.). For example, the power switching network 350 can receive PWM signals from the controller 300 to drive the motor 305. Typically, when the trigger 320 is pressed, current is supplied to the motor 305 from the power supply 310 through the power switching network 350. When the trigger 320 is not pressed, current is not supplied to the motor 305 from the power supply 310. For example, a trigger pull sensor senses the amount by which the trigger 320 is pulled. In some examples, the output of the power switching network 350 is supplied to an AC outlet to power AC devices.

[0032] Motor 305 can be energized based on the state of trigger 320. Typically, motor 305 is energized when trigger 320 is activated and de-energized when trigger 320 is deactivated. In the illustrated embodiment, trigger 320 can be biased (e.g., with a biasing member such as a spring) such that when the user releases trigger 320, trigger 320 moves in a second direction away from the handle of power tool 100. In some embodiments, controller 300 determines the off-state of power tool 100 based on a trigger pull sensor. For example, controller 300 can determine that power tool 100 is no longer operated based on the absence of input from the trigger pull sensor within a predetermined time period and / or the release of the trigger pull sensor. In some examples, trigger 320 is a variable-speed trigger, such that trigger switch 315 provides controller 300 with a signal corresponding to the amount of trigger pull (e.g., the distance the trigger is pulled). This signal from trigger switch 315 can be generated using, for example, a potentiometer, an inductive sensor, etc., and provides a speed command (e.g., as a percentage of maximum speed).

[0033] The power switching network 350 is electrically connected to the motor 305. In some embodiments, the motor 305 is a brushless direct current (BLDC) motor. In some embodiments, the motor 305 is a permanent magnet synchronous motor (PMSM). In some embodiments, the power supply 310 is a battery pack, such as battery pack 200. The power switching network 350 is also electrically and communicatively connected to the controller 300. One or more gate drivers 450 may also be disposed between the controller 300 and the power switching network 350. In one example, the gate driver 450 may be integrated with the FET of the power switching network 350. The one or more gate drivers 450 receive a supply voltage from the power input and control signals from the controller 300.

[0034] Figure 4This is a simplified block diagram of a motor drive 400 of a power tool 100 according to some embodiments. In the illustrated example, the motor drive 400 includes a power switch network 350 connected between a power supply 310 and a motor 305 in a three-phase inverter bridge configuration. The power supply 310 supplies power to the power switch network 350. The power switch network 350 includes three half-bridges. Each half-bridge includes at least two wide-bandgap semiconductor FETs (WBS FETs). In the illustrated example, the power switch network 350 includes Qa+ first high-side WBS FET 410, Qb+ second high-side WBS FET 415, Qc+ third high-side WBS FET 420, Qa- first low-side WBS FET 425, Qb- second low-side WBS FET 430, and Qc- third low-side WBS FET 435. In some examples, the high side consists of at least two WBS FETs connected in parallel. For example, the first high side may include three WBS FETs placed in parallel, which results in the on-resistance being reduced to one-third of the on-resistance of a single WBS FET.

[0035] In one example, WBS FETs include gallium nitride FETs (GaN FETs), silicon carbide FETs (SiC FETs), etc. In another example, a WBS FET is a high electron mobility transistor (HEMT), such as an enhancement-mode HEMT (E-HEMT), particularly a GaNHEMT or GaN E-HEMT. The bandgap of a WBS FET is, for example, in the range of about 3-4 electron volts (eV). WBS FETs exhibit several characteristics that offer advantages over conventional field-effect transistors (FETs) (e.g., MOSFETs).

[0036] A WBS FET is a three-terminal device, for example, having a source (S), drain (D), and gate (G). The structure of a WBS FET can consist of a thin GaN layer sandwiched between two AlGaN (aluminum gallium nitride) layers. For example, the GaN layer acts as a channel for electrons to flow from the source (S) to the drain (D). The AlGaN layer acts as a barrier, reducing the electron density in the channel and allowing for better control of the electron flow. A GaNHEMT can be an enhancement-mode transistor, where applying a gate voltage (or current) to the device creates a conductive channel in the GaN layer for current to flow from the source to the drain. A switching transistor is one in which a voltage (or current) is applied to the gate to activate or deactivate the conductive channel. GaN HEMTs have high electron mobility, meaning electrons can move faster in the channel, resulting in higher current densities than conventional silicon MOSFET devices.

[0037] The switching frequency of a WBS FET refers to the rate at which the transistor can be activated and deactivated. Specifically, a WBS FET can be operated at high frequencies, such as 100 kHz, 200 kHz, 400 kHz, or even higher, while losing less energy as heat than a MOSFET operating at lower frequencies. Compared to conventional FETs, WBS FETs have faster response times. In some implementations, GaN E-HEMTs can be used and operated at a switching frequency of at least 50 kHz. In one example, a WBS FET is operated at a switching frequency between 20 kHz and 100 kHz. In some examples, a WBS FET can be operated at switching frequencies up to 250 kHz, 400 kHz, or similar frequencies. Furthermore, WBS FETs can be used with low dead times, for example, less than 100 nanoseconds. Dead time can refer to the time interval between deactivating a first WBS FET in the power switching network 350 and activating a second WBS FET.

[0038] Operating the WBS FET at high frequencies provides a higher resolution signal at the input of motor 305. Compared to MOSFETs, the wide-bandgap semiconductor increases frequency during operation, allowing for a reduction in energy storage capacity for the same total output power rating. Furthermore, because the WBS FET operates more efficiently than MOSFETs, it generates less heat during operation, enabling the use of smaller heatsinks and fans. Therefore, by replacing the MOSFETs within the power switching network 350 and controller 300 with WBS FETs, the size and weight of components within the power tool 100 can be reduced, and the efficiency of the power tool 100 can be improved.

[0039] The motor drive 400 includes a DC link capacitor network 405 (e.g., one or more DC link capacitors, or multiple DC link capacitors) connected across the DC bus (i.e., between the positive and negative inputs to the power switching network 350). Using a WBS FET instead of a MOSFET in the power switching network 350 allows for a reduction in the capacitance of the DC link capacitor network 405, resulting in a smaller size. In some examples, electrolytic capacitors, typically used with MOSFETs, are replaced by ceramic capacitors. Ceramic capacitors have higher temperature ratings and lower losses compared to electrolytic capacitors. In one example, the ceramic capacitor is a multilayer ceramic capacitor (MLCC). Using ceramic capacitors with WBS FETs in the power tool 100 allows for higher power density hardware designs. When used in the power tool 100, the motor drive 400 achieves significant size savings and better thermal management.

[0040] Half-bridge WBS FETs are electrically connected to different phases of motor 305. For example, WBS FETs 410 and 425 are connected to the W phase of motor 305, WBS FETs 415 and 430 are connected to the V phase of motor 305, and WBS FETs 420 and 435 are connected to the U phase of motor 305. As the motor rotates, position sensor 345 communicates with controller 300, allowing controller 300 to determine the rotational position of motor 305. Position sensor 345 outputs position signals Ha, Hb, and Hc to controller 300. In some embodiments, position sensor 345 is a digital Hall effect sensor. In other embodiments, motor 305 is a sensorless motor, and the rotor position can be detected using various sensorless motor sensing techniques (e.g., BEMF detectors, etc.). In some embodiments, position sensor 345 is an encoder, position sensing integrated circuit, etc.

[0041] One or more current sensors 445 are connected in the power path to detect the current in the power path. Figure 4 In the example shown, the power tool 100 includes a first current sensor 445A and a second current sensor 445B, which are connected between the power switching network 350 and the motor 305 on the two phase lines connecting the power switching network 350 to the motor 305 (e.g., phase line sensing). In other examples, more or fewer current sensors 445 may be provided, and they may be connected at different locations in the power path. For example, current sensors 445 may be provided on all three phase lines connecting the power switching network 350 to the motor 305. One or more current sensors 445 may be connected between one or more of the low-side FETs 425, 430, 435 and the negative DC bus (e.g., single or triple low-side shunt sensing). The current sensors 445 may be located on one or both of the negative and positive DC buses. In the example shown, the current sensor 445 is a shunt resistor connected in the power path. The voltage drop across the shunt resistor (i.e., current sensor 445) is processed by electronics and then sampled by a current-sensing analog-to-digital converter (ADC) 455. The analog signal is converted into a digital signal and provided to the controller 300 for implementing motor control as further described below.

[0042] Controller 300 can implement field-oriented control (FOC) technology to control the firmware of motor 305. Controller 300 performs FOC of motor 305 based on position signals Ha, Hb, and Hc. Controller 300 uses FOC to generate a PWM output signal. Controller 300 sends the PWM control signal to gate driver 450. Gate driver 450 interprets the PWM control signal as six individual voltage switching signals (Sa+, Sa-, Sb+, Sb-, Sc+, and Sc-). The switching signals are pulse-width modulated (PWM) signals provided to each WBSFET at a switching frequency. Each voltage switching signal is provided to a different half-bridge WBSFET in the power switching network 350. Switching signal Sa+ corresponds to WBS FET 410. Switching signal Sa- corresponds to WBS FET 425. Switching signal Sb+ corresponds to WBS FET 415. Switching signal Sb- corresponds to WBS FET 430. Switching signal Sc+ corresponds to WBS FET 420. The switching signal Sc corresponds to the WBS FET 435. Possible switching signal states are high and low. For one state of the corresponding switching signal, the WBS FET conducts current from the power supply 310 to the motor 305; for the complementary switching states of the switching signal, the WBS FET does not conduct current from the power supply 310 to the motor 305.

[0043] Controller 300 can be used as follows Figure 5 The controller topology 500 shown implements FOC motor drive. The power tool 100 includes a power supply 310, a gate driver 450, a power switch network 350, a motor 305, and a position sensor 345. The controller 300 receives position signals and current signals (e.g., combined with...) from the power tool. Figure 4 As described above), and provides the corresponding PWM control signal to the gate driver 450. Position sensor 345 is configured to sense the angular position of the rotor relative to the stator. Position sensor 345 outputs a position signal to sensor decoder 575. Sensor decoder 575 generates a mechanical motor angle (θ) based on the position signal. m The sensor decoder 575 will determine the mechanical motor angle (θ). m The timing measurement values ​​are output to the speed measurement block 590. The speed measurement block 590 calculates the rotor speed of the motor 305. The speed measurement block 590 is based on the mechanical motor angle (θ). m The motor speed signal (ω) is calculated from the timing measurements. fb The speed measuring block 590 transmits the motor speed signal (ω). fb The output is sent to the speed control block 510. The speed control block 510 calculates the motor speed feedback signal (ω). fb ) and desired speed (ω) refThe speed error (e.g., difference) between the desired speed (ω) and the expected speed (ω). ref For example, a speed command received from the transmission trigger 320. The speed control block 510 calculates the speed error signal and generates a torque command (e.g., a torque control signal (T)) based on this speed error. ref ))).

[0044] Speed ​​control block 510 transmits torque control signal (T) ref The output is sent to the dq-axis control reference generator block 515. In some implementations, the dq-axis control reference generator can implement maximum torque-to-current ratio (MTPA) control, field weakening control, and / or similar control. The dq-axis control reference generator block 515 calculates the d-axis and q-axis currents that generate the desired torque and speed. The d-axis is the direct axis, corresponding to the direction of the rotor flux. The q-axis is the quadrature axis, corresponding to the axis that leads the d-axis by 90 degrees in electrical angle. The q-axis corresponds to the torque generation component of motor 305. The dq-axis control reference generator block 515 uses the torque control signal (T... ref )) and desired velocity (ω) ref Generate q-axis control current (I) q ref ) and d-axis control current (I d ref For example, the dq-axis control reference generator block 515 calculates the d-axis and q-axis control currents based on the desired speed, torque control signal, and motor base speed. The dq-axis control reference generator block 515 then calculates the q-axis control current (Iq). q ref The output is sent to the q-axis regulator 525. The dq-axis control reference generator block 515 outputs the d-axis control current (I) to the q-axis regulator 525. d ref The output is sent to the d-axis adjuster 520. The speed control block 510, the dq-axis control reference generator block 515, the q-axis adjuster 525, and the d-axis adjuster 520 together achieve independent torque and speed control of the motor 305, which is different from other motor drive technologies (such as trapezoidal wave commutation motor drives).

[0045] The sensor decoder 575 will determine the mechanical motor angle (θ). m The output is sent to the mechanical-to-electrical converter 570. The mechanical-to-electrical converter 570 converts the mechanical rotor motor angle (θ) to an electrical-to-electrical angle. m ) transformed into electric rotor motor angle (θ) e The mechanical-to-electric converter block 570 will change the angle (θ) of the electric rotor motor. e The output is sent to the sine / cosine lookup block 585. The sine / cosine lookup block 585 calculates the electric rotor motor angle (θ). e The sine value of ) and the angle of the electric rotor motor (θ) eThe cosine value of θ. Electric rotor motor angle (θ) e The sine and cosine values ​​of the result are output to Park transform block 565 and inverse Park transform block 530, respectively.

[0046] In the example shown, controller 300 receives two instantaneous line currents (I0, I ...) from power switching network 350. a and I b In other embodiments, different sets of line currents can be received. Two phases of the three-phase motor 305 generate these two line currents (I...). a and I b Clarke converter block 560 converts line current (I) a and I b Transformed into α-β coordinate system line current (I) α and I β The α-β coordinate system is a simplified two-phase system used to represent the three-phase motor 305. The Clarke transform block 560 converts the orthogonal currents (I...) α and I β The output is sent to the Park converter block 565. The Park converter block 565 receives the quadrature line current (I0). α and I β ) and sine and cosine signals from sine and cosine lookup block 585. Park transform block 565 is based on orthogonal line current (I α and I β ) and sinusoidal and cosine signals generate orthogonal d-axis and q-axis currents (I ) d and I q Park converter block 565 converts the q-axis current (I). q ) and d-axis current (I d The outputs are respectively sent to the q-axis adjuster 525 and the d-axis adjuster 520.

[0047] The q-axis regulator 525 calculates the error between the desired q-axis current and the actual q-axis current. The q-axis regulator 525 receives the q-axis control current (Iq) from the dq-axis control reference generator block 515. q ref The q-axis regulator 525 also receives q-axis current (I) from the Park converter block 565. q The q-axis adjuster 525 uses the q-axis control current (I). q ref ) and q-axis current (I q The q-axis regulator 525 calculates the current error. It uses a proportional-integral (PI) controller to correct the calculated error. The q-axis regulator 525 then applies the q-axis voltage control signal (V...) to the... q refThe output is sent to the inverse Park transform block 530. The d-axis regulator 520 operates similarly to the q-axis regulator 525, except it operates on the d-axis. The d-axis regulator 520 receives the d-axis control current (Iq) from the dq-axis control reference generator block 515. d ref The d-axis adjuster 520 receives the d-axis current (I) from the Park converter block 565. d The d-axis adjuster 520 uses d-axis control current (I). d ref ) and d-axis current (I d The d-axis regulator 520 calculates the current error. It uses a PI controller to correct the calculated error. The d-axis regulator 520 then applies the d-axis voltage control signal (V...) to the... d ref The output is sent to the inverse Park converter block 530. The inverse Park converter block 530 converts the q-axis voltage control signal (V) into a signal that is then sent to the inverse Park converter block 530. q ref ) and d-axis voltage control signal (V d ref ) is converted into a simplified α-β quadrature voltage (V α and V β The inverse Park transform block 530 will simplify the α-β quadrature voltage (V). α and V β The output is sent to the PWM generator 535. The PWM generator 535 is based on the input quadrature voltage (V). α and V β The PWM generator 535 generates a PWM control signal. The PWM generator 535 outputs the PWM control signal to the gate driver 450. The gate driver 450 converts the PWM control signal into six separate voltage switching signals, i.e., PWM gate signals. The frequency of the PWM signals is at least 50 kHz. In some embodiments, the frequency of the PWM signals is less than 250 kHz.

[0048] Figure 6 This is a flowchart of an example method 600 for controlling motor 305. Method 600 can be implemented by controller 300 using controller topology 500, and in conjunction with... Figure 5 An explanation is needed. However, method 600 can be interpreted differently. Figure 5Other implementations are shown. In the illustrated example, method 600 includes receiving a speed command (in block 605). The speed command may be provided by user input, for example, via a speed change trigger 320 or other speed setting mechanism. In some examples, the speed command may be provided by the controller 300 based on the operating parameters and conditions of the power tool. When a speed command is received using trigger 320, trigger switch 315 converts the trigger pull amount into a speed command and provides the speed command to the controller 300, for example, as a speed reference.

[0049] Method 600 includes generating an FOC control reference signal based on a speed command (in block 610). See also Figure 5 The speed control block 510 receives the speed command and generates the FOC torque reference signal (T) based on the speed command. ref The speed control block 510 receives the current speed of the motor (e.g., current speed) from the speed measurement block 590 and generates an FOC torque reference signal to reduce the error between the speed command and the current motor speed. The dq axis control reference generator block 515 receives the FOC torque reference signal and generates an FOC current reference signal (I) based on the FOC torque reference signal. q ref and I d ref The dq axis control reference generator block 515 receives the speed command and generates the FOC current reference signal based on the speed command and the FOC torque reference signal.

[0050] In some examples, controller 300 determines whether a speed command is higher than (e.g., equal to or greater than) the base speed of motor 305. The base speed of a motor is defined as the maximum speed at which the motor can operate with its rated torque. Above the motor's base speed, torque can be reduced to maintain the motor speed. Controller 300 compares the speed command to the base speed to determine if the speed command is higher than the base speed. The base speed may be pre-stored in the controller 300's memory.

[0051] The control method used to generate the FOC control reference signal can depend on whether the speed command is higher or lower than the base speed of motor 305. For example, when the speed command is lower than the base speed of motor 305, the dq axis control reference generator block 515 uses MTPA control to generate the FOC control reference signal. The motor torque can be reduced to maintain a motor speed higher than the base speed of motor 305. When the speed command is higher than the base speed of motor 305, the dq axis control reference generator block 515 can use field weakening control to generate the FOC control reference signal.

[0052] Method 600 includes generating a PWM control signal based on an FOC control reference signal (in block 615). The FOC current reference signal is provided to regulators 520, 525 to calculate the error between the FOC current reference signal and a measured current flowing between the power switching network 350 and the motor 305. A PWM generator 535 receives the error signal and generates the PWM control signal based on it. Specifically, the PWM control signal is generated to reduce the error to zero or near zero. The PWM control signal based on the error signal can be generated with a higher or lower duty cycle compared to a previous PWM control signal.

[0053] Method 600 includes switching WBS FETs 410-435 (in block 620) at a switching frequency of at least 50 kHz based on a PWM signal. The WBS FETs are switched between an on state (where the selected WBS FET conducts current between the power supply and motor 305) and a non-on state (where the selected WBS FET does not conduct current between the power supply and motor 305 (e.g., blocks current)). A PWM signal pin from controller 300 (or PWM generator 535) is connected to an input pin of gate driver 450. Gate driver 450 receives a PWM control signal and converts the PWM control signal into a gate drive signal for each FET (or a pair of FETs depending on the GaN FET configuration). The gate drive signals are provided to WBS FETs 410-435. As described above, the WBS FETs are switched at a switching frequency of at least 50 kHz (e.g., equal to or greater than 50 kHz).

[0054] Therefore, the various embodiments described in this invention provide wide-clearance motor drives with FOC for power tools. Various features and advantages are set forth in the appended claims.

Claims

1. A power tool, comprising: motor; Power input section; A power switch network electrically connected between the power input section and the motor, the power switch network including a plurality of wide bandgap semiconductor (WBS) field-effect transistors (FETs). as well as A controller, electrically connected to the power switch network and configured to, Receive speed command; Based on the speed command, a field orientation control (FOC) reference signal is generated; and A pulse width modulation (PWM) signal is generated based on the FOC control reference signal, wherein the plurality of WBS FETs switch between an on state and an off state based on the PWM signal, with a switching frequency of at least 50 kHz.

2. The power tool according to claim 1, wherein, The plurality of WBS FETs include gallium nitride (GaN) high electron mobility transistors (HEMTs).

3. The power tool according to claim 1, wherein, The switching frequency is less than 250 kHz.

4. The power tool according to claim 1, wherein, The controller is further configured as follows: Determine the speed of the motor; Generate an FOC torque reference signal based on the speed command and the motor speed; and An FOC current reference signal is generated based on the FOC torque reference signal and the speed command, wherein the FOC control reference signal includes the FOC current reference signal.

5. The power tool according to claim 4, wherein, The controller generates the FOC torque reference signal to reduce the error between the speed command and the speed of the motor.

6. The power tool according to claim 1, wherein, When the speed command is lower than the base speed of the motor, the FOC control reference signal is generated based on the maximum torque-to-current ratio control, and when the speed command is higher than the base speed of the motor, the FOC control reference signal is generated based on field weakening control.

7. The power tool according to claim 1, wherein, The dead time between the on-state and the off-state of the plurality of WBS FETs is less than 100 nanoseconds.

8. The power tool according to claim 1, further comprising a DC ceramic capacitor network connected across the DC bus of the power switching network.

9. A method for controlling a motor in a power tool, the method comprising: The controller of the power tool receives speed commands; The controller is used to generate a field orientation control (FOC) reference signal based on the speed command; The controller is used to generate a pulse width modulation (PWM) signal based on the FOC control reference signal; as well as A plurality of wide-bandgap semiconductor (WBS) field-effect transistors (FETs) of a power switching network are electrically connected between the power input section of the power tool and the motor of the power tool. The plurality of WBS FETs switch between an on state and an off state based on the PWM signal, and the switching frequency is at least 50 kHz.

10. The method according to claim 9, wherein, The switching frequency is less than 250 kHz.

11. The method of claim 9, further comprising: Determine the speed of the motor; The controller generates an FOC torque reference signal based on the speed command and the speed of the motor. as well as The controller generates an FOC current reference signal based on the FOC torque reference signal and the speed command, wherein the FOC control reference signal includes the FOC current reference signal.

12. The method according to claim 11, wherein, The FOC torque reference signal is generated to reduce the error between the speed command and the motor speed.

13. The method according to claim 9, wherein, The dead time between the on-state and the off-state of the plurality of WBS FETs is less than 100 nanoseconds.

14. The method according to claim 9, wherein, The plurality of WBS FETs include gallium nitride (GaN) high electron mobility transistors (HEMTs).

15. The method according to claim 9, wherein, When the speed command is lower than the base speed of the motor, the FOC control reference signal is generated based on the maximum torque-to-current ratio control, and when the speed command is higher than the base speed of the motor, the FOC control reference signal is generated based on field weakening control.

16. A power tool, comprising: Power input section; Speed ​​change trigger; A motor, the motor including a speed sensor; A power switching network electrically connected between the power input section and the motor, and including a plurality of gallium nitride (GaN) high electron mobility transistors (HEMTs). as well as A controller, which is electronically connected to the power switch network and configured to... The speed command is received via the speed trigger. The speed sensor is used to determine the motor speed; Based on the speed command and the motor speed, an FOC control reference signal is generated; as well as A pulse width modulation (PWM) signal is generated based on the FOC control reference signal, wherein the plurality of GaN HEMTs switch between an on state and a non-on state based on the PWM signal, with a switching frequency of at least 50 kHz.

17. The power tool according to claim 16, wherein, The switching frequency is less than 250 kHz.

18. The power tool according to claim 16, wherein, When the speed command is lower than the base speed of the motor, the FOC control reference signal is generated based on the maximum torque-to-current ratio control, and when the speed command is higher than the base speed of the motor, the FOC control reference signal is generated based on field weakening control.

19. The power tool according to claim 16, wherein, The dead time between the on-state and the off-state of the plurality of GaN HEMTs is less than 100 nanoseconds.

20. The power tool of claim 16, further comprising a DC ceramic capacitor network connected across the DC bus of the power switching network.

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