Electric tool

Abstract

The power tool includes a motor, a power interface configured to connect to a power source, and a printed circuit board ("PCB") electrically connected to the motor and the power interface. The PCB includes a three-level or higher-level inverter configured to control power supplied by the power source to the motor.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 288,285, filed December 10, 2021, and U.S. Provisional Patent Application No. 63 / 292,587, filed December 22, 2021, which are incorporated by reference in their entirety. TECHNICAL FIELD

[0003] The detailed description of the application described herein relates to inverters for power tools. Utility Content

[0004] An inverter is a power electronic device or circuit that converts a direct current (DC) voltage to an alternating current (AC) voltage or an approximate AC voltage. The AC frequency obtained thereby depends on the particular device employed. An inverter includes or is connected to semiconductor switches, filter components (e.g., capacitors and inductors), control circuitry, etc. In some embodiments, the semiconductor switches are modulated at a high frequency to reproduce an approximate AC waveform. However, when the semiconductor switches change state (e.g., from high to low), the switches generate power losses. The higher the voltage that a semiconductor switch is subjected to, the greater the losses typically are. Moreover, switches made from silicon (Si) have much slower switching speeds than switches made from gallium nitride (GaN) or silicon carbide (SiC). Also, high voltage semiconductor switches typically have a large on-resistance and generate power losses (i.e., switching and conduction losses). In some embodiments, to minimize switching losses in Si, the modulation frequency is kept at a moderate value (e.g., 10 kHz to 30 kHz).

[0005] GaN and SiC are wide bandgap (WBG) semiconductors. These devices can be switched at much higher frequencies due to the much lower characteristic capacitance. Typically, the bandgap of silicon is about 1.1 electron volts (eV). WBG semiconductors can have a bandgap of about 3 eV or more. However, in some embodiments, the bandgap of a WBG semiconductor is less than 3 eV. Generally, the wider the bandgap, the higher the critical electric field, which means that a device formed from a wide bandgap semiconductor of the same size can have a higher breakdown voltage relative to a silicon-based device. The higher frequencies result in a reduction in the electrical (i.e., capacitance or inductance) and physical size of passive components such as capacitors and inductors. This reduction in size, while increasing power density, also reduces the weight and size of the product.

[0006] The detailed description of the application described herein provides a power tool including a motor, a power interface configured to be connected to a power source, and a printed circuit board (“PCB”) electrically connected to the motor and the power interface. The PCB includes a three-level or higher level inverter configured to control power supplied to the motor by the power source.

[0007] In some aspects, the three-level or higher-level inverter is a flying capacitor multilevel (“FCML”) inverter.

[0008] In some aspects, a switching frequency of the three-level or higher-level inverter is a multiple of a fundamental switching frequency of the three-level or higher-level inverter, and a level of the three-level or higher-level inverter is a multiple of the fundamental switching frequency.

[0009] In some aspects, the three-level or higher-level inverter is a three-level inverter, a five-level inverter, a seven-level inverter, a nine-level inverter, or an eleven-level inverter.

[0010] In some aspects, a modulated voltage between two levels during operation of the three-level or higher-level inverter is given by V 总线 / (N-1), where N is the number of levels.

[0011] In some aspects, the power tool includes an inductor and a capacitor at an output of the three-level or higher-level inverter.

[0012] In some aspects, a pulse frequency seen through the inductor is given by (N-1)f sw , where f sw is a switching frequency of at least one switch in the three-level or higher-level inverter.

[0013] In some aspects, an inductor ripple current of the three-level or higher-level inverter is limited according to Δi L = 0.25V 总线 / (N-1) 2 f sw L, where L is an inductance of the inductor, V 总线 is a bus voltage of the power tool.

[0014] In some aspects, the PCB includes a wide bandgap (“WBG”) semiconductor.

[0015] In some aspects, the WBG semiconductor includes gallium nitride (“GaN”) and / or silicon carbide (“SiC”).

[0016] In some aspects, the three-level or higher-level inverter is a cascaded H-bridge inverter or a diode clamped inverter.

[0017] In some aspects, the power source is a battery pack.

[0018] In some aspects, a nominal voltage of the battery pack is greater than 50 V DC.

[0019] The detailed description provided in the present application provides an electric power tool including a motor, a battery pack interface configured to receive a battery pack, and a three-level or higher-level inverter for controlling power supplied to the motor from the battery pack. A switching frequency of the three-level or higher-level inverter is a multiple of a fundamental switching frequency of the three-level or higher-level inverter. A level of the three-level or higher-level inverter is a multiple of the fundamental switching frequency.

[0020] In some aspects, the three-level or higher-level inverter is a three-level inverter, a five-level inverter, a seven-level inverter, a nine-level inverter, or an eleven-level inverter.

[0021] In some aspects, a modulated voltage between two levels during operation of the three-level or higher-level inverter is given by V 总线 / (N-1), where N is the number of levels.

[0022] In some aspects, the electric power tool includes an inductor and a capacitor at an output of the three-level or higher-level inverter, and a pulse frequency seen through the inductor is given by (N-1)f sw , where f sw is a switching frequency of at least one switch in the three-level or higher-level inverter.

[0023] In some aspects, the three-level or higher-level inverter is defined by Δi L = 0.25V 总线 / (N-1) 2 f sw L, where L is an inductance of the inductor, V 总线 is a bus voltage of the electric power tool.

[0024] In some aspects, the three-level or higher-level inverter is a cascaded H-bridge inverter or a diode-clamped inverter.

[0025] The electric power tool described in the present application includes a motor, a power source interface configured to connect to a power source, and a printed circuit board (“PCB”) electrically connected to the motor and the power source interface. The PCB includes a wide bandgap (“WBG”) semiconductor and a three-level or higher-level inverter configured to control power supplied to the motor from the power source. A topology of the three-level or higher-level inverter is one of a flying capacitor multilevel (“FCML”) inverter, a cascaded H-bridge inverter, or a diode-clamped inverter.

[0026] Before any particular embodiment is explained in detail, it is to be understood that the embodiments are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The embodiments are capable of implementation in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.

[0027] Moreover, it is to be understood that the specific embodiments can be comprised of hardware, software, and electronic components or modules, and that the embodiments can be implemented in any of the forms of hardware, software, or a combination of hardware and software suitable for the intended application. Furthermore, the disclosure can be practiced in the absence of an article of manufacture comprising all the features, components, or steps described in the specification. For the purposes of this application, the term "article of manufacture" includes hardware, software, and any combination of hardware and software suitable for the intended application. The software can include, but is not limited to, firmware, routines, computer programs, instructions, operation

[0028] Relative terms such as "about," "approximately," "substantially" and variations thereof as used herein refer to a value that is acceptable (e.g., within manufacturing, assembly, use, etc. tolerances) to one of ordinary skill in the art given the benefit of the disclosure, and the meaning of the term will be understood by those of ordinary skill in the art given the context in which the term is used (e.g., the term includes at least the degree of error associated with the measurement accuracy, tolerances associated with the particular value, etc.). Such terms are also to be taken as disclosing a range that is defined by the absolute values of the two endpoints. For example, the expression "from about 2 to about 4" also discloses the range "from 2 to 4." Relative terms can refer to a percentage of the indicated value (e.g., 1%, 5%, 10% or more).

[0029] It should be understood that, although certain embodiments are illustrated as including particular components, software, and / or hardware, these depictions are merely illustrative and not limiting of the scope of the application. Functional aspects of the application that are illustrated as being performed by one component can be performed by multiple components in distributed fashion. Likewise, aspects of the application that are illustrated as being performed by multiple components can be performed by a single component. In some embodiments, the components can be combined or divided into separate software, firmware, and / or hardware. For example, the logic operations and processes can be distributed among multiple electronic processors, rather than being within a single electronic processor. Hardware and software components can be located within the same computing device or can be distributed among different computing devices connected through one or more networks or other suitable communication links. Aspects of the components that are described as being configured to perform particular functions can also perform additional functions that are not described in the present disclosure. For example, a device or structure that is configured in a certain way can be configured in that way at least to perform the functions described in this disclosure, but can also be configured to perform additional functions that are not expressly listed.

[0030] Other aspects of the detailed description will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 An electric power tool is shown in accordance with the detailed description described herein.

[0032] Figure 2 A control system for an electric power tool is shown in accordance with the detailed description described herein. Figure 1

[0033] Figure 3A , 3B and 3D each show an exemplary embodiment of a multi-level inverter in accordance with the detailed description described herein.

[0034] Figure 3C A table is shown that includes switch states for a five-level inverter as depicted in Figure 3B

[0035] Figure 4A , 4B 4C shows an exemplary layout of a PCB configured as a wide bandgap inverter in accordance with the detailed description described herein.

[0036] Figure 5 An inverter circuit is shown that includes a wide bandgap semiconductor device. DETAILED DESCRIPTION

[0037] ​​The detailed description of the application described herein relates to electrical equipment such as power tools that include a motor, a power source, and a printed circuit board (PCB) electrically connected to the motor and the power source. In some embodiments, the PCB is configured as a multi-level inverter that controls the voltage and frequency of the power supplied by the power source to the motor. In some embodiments, the topology of the multi-level inverter includes a flying capacitor multi-level (FCML) inverter. In some embodiments, the switching frequency presented to passive filter components of the inverter is a multiple of the fundamental switching frequency of the inverter, and where the level of the inverter is a multiple of the fundamental switching frequency. In some embodiments, the multi-level inverter is a three-level, five-level, seven-level, nine-level, or eleven-level inverter. In some embodiments, the modulation between levels is defined according to V 总线 / (N-1) where N is the number of levels while the multi-level inverter is operating. In some embodiments, the passive filter components include an inductor and a capacitor. In some embodiments, the pulse frequency seen through the inductor is defined according to (N-1)f sw where f sw is the switching frequency of each switch of the multi-level inverter. In some embodiments, the modulation between levels is defined according to Δi L = 0.25V 总线 / (N-1) 2 f sw L. In some embodiments, the PCB includes a wide bandgap (WBG) semiconductor. In some embodiments, the WBG semiconductor includes GaN and / or SiC. In some embodiments, the topology of the multi-level inverter is a cascaded H-bridge inverter or a diode clamped inverter. In some embodiments, the motor is an AC motor. In some embodiments, the power source produces a direct current (DC) voltage.

[0038] Figure 1 A power tool 100 is shown. The power tool 100 can be, for example, an impact wrench, a drill, a ratchet, a saw, a hammer drill, an impact drill, a rotary hammer, a grinder, a blower, an edger, etc. The power tool 100 includes a housing or motor housing 105 that houses a motor (see Figure 2 ) within the power tool 100. The power tool is configured to receive a power source 110 that provides direct current (DC) power to various components of the power tool 100, including the motor. The power source 110 can be a rechargeable power tool battery pack that uses, for example, lithium-ion battery cells.

[0039] Figure 2A control system 200 for the power tool 100 is shown. The control system 200 includes a controller 205. The controller 205 is electrically and / or communicatively connected to various modules or components of the power tool 100. For example, the illustrated controller 205 is electrically connected to the motor 202, the battery pack interface 210, the trigger switch 215 (connected to the trigger 220), one or more sensors or sensing circuits 225, one or more indicators 230, a user input module 235, a power input module 240, and an inverter or FET switch module 245. The controller 205 includes a combination of hardware and software, which among other things, can be operative to control operation of the power tool 100, monitor operation of the power tool 100, activate one or more indicators 230 (e.g., LEDs), etc.

[0040] The controller 205 includes a plurality of electrical and electronic components that provide power, operational control, and protection for the components and modules within the controller 205 and / or the power tool 100. For example, the controller 205 includes, among other things, a processing unit 250 (e.g., a microprocessor, microcontroller, electronic processor, electronic controller, or another suitable programmable device), a memory 260, an input unit 265, and an output unit 270. The processing unit 250 includes, among other things, a control unit 275, an ALU 280, and a plurality of registers 285, and is implemented using a known computer architecture (e.g., a modified Harvard and / or Von Neumann architecture). The processing unit 250, the memory 260, the input unit 265, the output unit 270, and various modules or circuits connected to the controller 205 are connected by one or more control and / or data buses (e.g., a common bus 290). Figure 2 The control and / or data buses are shown generally for illustration.

[0041] In some implementations, the memory 260 is a non-transitory computer- readable medium and includes program storage and data storage, among others. In some implementations, the program storage and data storage include a combination of different types of memory, such as read-only memory (ROM), random access memory (RAM) (such as dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and the like), electrically erasable programmable read-only memory (EEPROM), flash memory, a hard disk, a secure digital (SD) card, or other suitable magnetic, optical, physical, or electronic memory devices. The processing unit 250 is connected to the memory 260 and executes software instructions that can be stored in the RAM of the memory 260 (e.g., during execution), the ROM of the memory 260 (e.g., generally permanently stored), or another non-transitory computer-readable medium (such as another memory or an optical disc). In some implementations, software included in the implementation of the power tool 100 is stored in the memory 260 of the controller 205. For example, the software includes firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. In some implementations, the controller 205 is configured to retrieve and execute instructions related to the control processes and methods described herein from the memory 260, among others. In other configurations, the controller 205 includes additional, fewer, or different components.

[0042] In some implementations, the battery pack interface 210 includes a combination of mechanical components (such as rails, slots, latches, and the like) and electrical components (such as one or more terminals) that are configured and operable to couple (e.g., mechanically, electrically, and communicatively) the power tool 100 with the battery pack 110. For example, power provided by the battery pack 110 to the power tool 100 is provided to the power input module 240 through the battery pack interface 210. In some implementations, the power input module 240 includes a combination of active and passive elements to regulate or control the power received from the battery pack 110 before providing power to the controller 205. In some implementations, the battery pack interface 210 also supplies power to the inverter 245 for selective supply of power to the motor 202 by switching by the inverter. The battery pack interface 210 also includes, for example, the communication line 295 for establishing a communication line or link between the controller 205 and the battery pack 110.

[0043] In some embodiments, the inverter 245 is configured on a printed circuit board ("PCB") electrically connected to the motor 202 and the battery pack 110. In some embodiments, the motor 202 is an alternating current ("AC") motor. In some embodiments, the inverter 245 is configured to control the voltage and frequency of the power supplied by the battery pack 110 to the motor 202. In some embodiments, the PCB includes logic decision devices or gate drivers, such as a microcontroller (MCU), a central processing unit (CPU), a field programmable gate array (FPGA), etc., coupled with power electronic devices such as transistors. In some embodiments, the PCB includes WBG semiconductors to form a WBG inverter. In this application, "WBG semiconductors" refer to semiconductors with wider bandgaps than silicon. Typically, the bandgap of silicon is about 1.1 electron volts (eV). WBG semiconductors can have a bandgap of about 3 eV or more. However, in some embodiments, the WBG semiconductors employed have a bandgap less than 3 eV. Generally, the wider the bandgap, the higher the critical electric field, which means that a device formed from a wide bandgap semiconductor of the same size can have a higher breakdown voltage relative to a silicon-based device.

[0044] By using WBG semiconductors, the WBG inverter 245 can be installed on a smaller machine because the semiconductors are smaller in size, and WBG semiconductors enable higher operating frequencies and allow higher operating temperatures. In some embodiments, employing a WBG inverter 245 enables higher motor operating speeds (e.g., 75,000 to 100,000 revolutions per minute [RPM] or more, rather than, for example, 30,000 RPM). In addition, the WBG inverter 245 is smaller in size, has lower switching and conduction losses, is more thermally conductive, and allows for higher operating temperatures relative to inverters formed with silicon-based semiconductors. As a result, the WBG inverter 245 can be installed directly to the motor 202 without incurring too many, if any, adverse effects (see Figure 5 ). In some embodiments, the PCB includes ceramic chip capacitors, which are smaller, can operate at higher temperatures, and are more reliable than aluminum electrolytic capacitors, for example. The WBG inverter 245 can enable higher power for a given motor package or the same power in a smaller motor package.

[0045] In some embodiments, the WBG inverter 245 is constructed using a topology of a multi-level (e.g., three-level or higher) inverter. In some embodiments, the topology of the multi-level inverter generates a desired output voltage through several DC voltage levels at its input. Exemplary multi-level inverter topologies include cascaded h-bridge inverters, diode clamped inverters, and FCML inverters.

[0046] In some embodiments, when using a multi-level inverter topology, the switching frequency presented to passive filter components such as inductors and capacitors is a multiple of the fundamental switching frequency of the inverter. In some embodiments, the level of the inverter is a multiple of this frequency. For example, for a five-level inverter with a fundamental switching frequency of 100 kilohertz (kHz), the effective ripple frequency presented to the passive element filter network is 4*100 kHz or 400 kHz. The increase in switching frequency helps to reduce the size of the passive elements. This is illustrated by considering an FCML inverter. During operation, the modulated voltage between two levels is V 总线 / (N-1), where N is the number of levels. The bus voltage V 总线 corresponds to the battery pack voltage of, for example, a battery pack connected to the power tool 100 (i.e., the battery pack 110). The nominal voltage of the battery pack 110 is, for example, 50 V DC or more (e.g., 50 V DC - 80 V DC). In some embodiments, the nominal voltage of the battery pack 110 is 72 V DC - 120 V DC. In some embodiments, the nominal voltage of the battery pack 110 is greater than 100 V DC, greater than 200 V DC, or greater than 300 V DC. By increasing the voltage of the battery pack 110 and thereby the bus voltage of the power tool 100, the voltage step between the levels of the multi-level inverter 245 is also increased. The multi-level inverter 245 can be used with a lower voltage battery pack 110, such as a battery pack with a nominal voltage of 12 V DC - 48 V DC. However, the multi-level inverter 245 is preferably used with a battery pack with a voltage of at least 50 V DC.

[0047] Furthermore, the pulse frequency seen through the inductor is (N-1)f sw , where f sw is the switching frequency of each switch. In some embodiments, the inductor ripple current of an N-level inverter (e.g., an FCML inverter) is given by the following equation: Δi L = 0.25V 总线 / (N-1) 2 f sw L. For a given value of inductor ripple current, an FCML inverter can employ an inductor that is (N-1) 2The output inductors of the multi-level inverter can be shared among the plurality of WBG semiconductor switches. By using WBG semiconductors in a multi-level inverter, the size (e.g., volume) and weight of the inverter can be significantly reduced while increasing the power density (increasing the power per unit volume). In addition, lower voltage rated semiconductors can be used in the multi-level inverter to support higher system voltages. For example, lower voltage rated metal oxide semiconductor field effect transistors (MOSFETs) typically have lower on-resistance, which in turn reduces the switching and conduction losses of the switches.

[0048] The indicator 230 includes one or more light emitting diodes ("LEDs") or the like. In some embodiments, the indicator 230 is configured to display a condition of the power tool 100 or information associated with the power tool 100. For example, the indicator 230 can be configured to indicate a measured electrical characteristic of the power tool 100, a device status, or the like. The user input module 235 is operably coupled to the controller 205, for example, to select a forward or reverse mode of operation, a torque and / or speed setting for the power tool 100 (e.g., using a torque and / or speed switch), or the like. In some embodiments, the user input module 235 includes a combination of digital and analog input or output devices required to achieve a desired level of control of the power tool 100, such as one or more knobs, one or more dials, one or more switches, one or more buttons, or the like.

[0049] The sensors 225 include one or more current sensors, one or more speed sensors, one or more Hall effect sensors, one or more temperature sensors, or the like. Within the memory 260, the controller 205 calculates or includes predetermined operating thresholds and limits for operation of the power tool 100. For example, when the controller 205 detects or predicts a potential thermal failure (e.g., of the FETs, the motor 202, or the like), power to the motor 202 can be limited or interrupted until the likelihood of the thermal failure is reduced.

[0050] Figure 3A 、 3B Each of FIGS. 1-3 illustrates a multi-level inverter for the power tool 100. Figure 3A A three-level FCML inverter 300 is illustrated. Figure 3B A five-level FCML inverter 310 is illustrated. Figure 3D A nine-level FCML inverter 320 is illustrated. Although several multi-level FCML inverters are illustrated, another type of multi-level inverter can be used in the power tool 100. Figure 3CThe table shown includes the switching states of the five-level FCML inverter 310 used to drive motor 202. Similar tables can also be used to drive motor 202 with three-level inverters, nine-level inverters, eleven-level inverters, etc., and can be adjusted according to the required number of switches. Each switch in inverter 245 includes its own gate driver for driving the switch to the appropriate on state (i.e., on or off).

[0051] Figure 4A , 4B Examples 400, 410, and 420 of a PCB configured as a WBG inverter 245 are shown in Figures 4C and 4C, respectively. Exemplary layouts 400, 410, and 420 describe power flow to manage the paths of current flow and return. Exemplary layout 400 is a lateral power loop 405 for a WBG half-bridge configuration (i.e., the input capacitor and power input are located on the same side of the PCB). Power loop 405 generates a magnetic field that induces a current in the shielding layer of the PCB, and this current flows in the opposite direction to power loop 405. The current in the shielding layer generates a magnetic field that counteracts the magnetic field of the original power loop, resulting in magnetic field cancellation. The shielding layer is positioned immediately adjacent to power loop 405 (e.g., as a second layer of the PCB) to minimize power loop inductance in the lateral power loop configuration.

[0052] Exemplary layout 410 is a vertical power loop 415 for a WBG half-bridge configuration (i.e., the input capacitor and power input are located on opposite sides of the PCB). As the PCB thickness decreases, the area of ​​the power loop 415 also decreases. The current flowing in opposite directions on the top and bottom layers of the PCB achieves magnetic self-cancellation.

[0053] Exemplary layout 420 is an optimized power loop 425 for a WBG half-bridge configuration (i.e., the input capacitor and power input are located on the same side of the PCB). The optimized power loop 425 uses a first inner layer ( Figure 4C (On the right) serves as the return path for the power circuit. The return path is located in power circuit 425 on the PCB. Figure 4C (Left side) Directly below the top layer. This positioning achieves a minimum physical loop area while also benefiting from magnetic self-cancellation.

[0054] Figure 5 An inverter circuit 500 for a power tool 100 is shown. The inverter circuit 500 includes a multi-level inverter 245 and an output filter, which includes an inductor 505 and a capacitor 510. Compared to that used in a two-level inverter, the inductor 505 and capacitor 510 have lower inductance and capacitance values, respectively. In some embodiments, the capacitor 510 is a ceramic chip capacitor, which is smaller, can operate at higher temperatures, and has higher reliability compared to aluminum electrolytic capacitors, etc.

[0055] Thus, among other things, the detailed description of the application provides an electric power tool comprising a multi-level inverter for driving a motor. The following claims set forth various features and advantages.

Claims

1. A power tool characterized by comprising: comprising: a motor; a power interface configured to be connected to a power source; and a printed circuit board electrically connected to the motor and the power interface, the printed circuit board comprising a three-level or higher-level inverter configured to control power supplied by the power source to the motor. The three-level or higher-level inverter is a flying capacitor multi-level inverter.

2. The power tool of claim 1, wherein, 3. The power tool of claim 1, wherein: a switching frequency of the three-level or higher-level inverter is a multiple of a base switching frequency of the three-level or higher-level inverter; and a level of the three-level or higher-level inverter is a multiple of the base switching frequency. The three-level or higher-level inverter is a three-level inverter, a five-level inverter, a seven-level inverter, a nine-level inverter, or an eleven-level inverter. Further comprising an inductor and a capacitor at an output of the three-level or higher-level inverter.

4. The power tool of claim 3, wherein, The printed circuit board comprises a wide bandgap semiconductor.

5. The power tool of claim 4, wherein, During operation of the three-level or higher-level inverter, the modulation voltage between two levels is given by V 总线 / (N-1), where N is the number of levels of the three-level or higher-level inverter.

6. The power tool of claim 5, wherein, The wide bandgap semiconductor comprises gallium nitride and / or silicon carbide.

7. The power tool of claim 6, wherein, The pulse frequency seen by the inductor is (N-1)f sw is given by f sw is the switching frequency of at least one switch in the three-level or higher level inverter.

8. The power tool of claim 7, wherein, According to Δi L = 0.25V 总线 / (N-1) 2 f sw L to limit an inductor ripple current of the three-level or higher-level inverter, wherein L is the inductance of the inductor, V 总线 is a bus voltage of the power tool.

9. The power tool of claim 1, wherein, The three-level or higher-level inverter is a cascaded H-bridge inverter or a diode clamped inverter.

10. The power tool of claim 9, wherein, The power source is a battery pack.

11. The power tool of claim 1, wherein, A nominal voltage of the battery pack is greater than 50 VDC.

12. The power tool of claim 1, wherein, comprising:

13. The power tool of claim 12, wherein, a motor; 14. A power tool characterized by comprising: a battery pack interface configured to receive a battery pack; a three-level or higher-level inverter for controlling power supplied by the battery pack to the motor, wherein a switching frequency of the three-level or higher-level inverter is a multiple of a base switching frequency of the three-level or higher-level inverter, and a level of the three-level or higher-level inverter is a multiple of the base switching frequency. The three-level or higher-level inverter is a three-level inverter, a five-level inverter, a seven-level inverter, a nine-level inverter, or an eleven-level inverter. Further comprising:

15. The power tool of claim 14, wherein, an inductor and a capacitor at an output of the three-level or higher-level inverter, 16. The power tool of claim 15, wherein, During operation of the three-level or higher-level inverter, the modulation voltage between two levels is given by V 总线 (N-1) where N is the number of levels.

17. The power tool of claim 16, wherein, the three-level or higher-level inverter is a cascaded H-bridge inverter or a diode clamped inverter. comprising: where the pulse frequency seen through the inductor is (N-1)f sw is given by f sw is the switching frequency of at least one switch in the three-level or higher level inverter.

18. The power tool of claim 17, wherein, According to Δi L = 0.25V 总线 / (N-1) 2 f sw L to limit an inductor ripple current of the three-level or higher-level inverter, where L is the inductance of the inductor, V 总线 is a bus voltage of the power tool.

19. The power tool of claim 14, wherein, a motor; 20. A power tool, characterized by a power interface configured to be connected to a power source; and a printed circuit board electrically connected to the motor and the power interface, wherein the printed circuit board comprises: a wide bandgap semiconductor, and a three-level or higher-level inverter configured to control power supplied by the power source to the motor, wherein a topology of the three-level or higher-level inverter is one of a flying capacitor multi-level inverter, a cascaded H-bridge inverter, or a diode clamped inverter. ​ ​ ​

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