Short circuit mitigation in power tools

Abstract

The power tool includes: a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack including a plurality of battery cells; an inverter positioned between the battery pack interface and the motor and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter and configured to control a current in the inverter; a controller configured to control the gate driver; and a short circuit detection circuit. The short circuit detection circuit is configured to monitor a current in the inverter, compare the current in the inverter to a short circuit threshold, and control a switch of the short circuit detection circuit to disable the gate driver when the current in the inverter is greater than or equal to the short circuit threshold.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 289,428 filed on December 14, 2021 and U.S. Provisional Patent Application No. 63 / 325,339 filed on March 30, 2022, the entire contents of each of which are hereby incorporated by reference herein. Technical Field

[0003] The embodiments described herein relate to controlling a motor of a power tool. Utility Model Content

[0004] The power tool includes circuitry configured to control the motor of the power tool. To prevent damage to the motor and power electronics and extend the life of the power tool, circuitry for detecting and preventing harmful conditions such as short circuits may be incorporated into the power tool.

[0005] The power tool described herein includes: a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack including a plurality of battery cells; an inverter positioned between the battery pack interface and the motor and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter and configured to control the current in the inverter; a controller configured to control the gate driver; and a short circuit detection circuit. The short circuit detection circuit is configured to monitor the current in the inverter, compare the current in the inverter with a short circuit threshold, and control a switch of the short circuit detection circuit to disable the gate driver when the current in the inverter is greater than or equal to the short circuit threshold.

[0006] In some aspects, the short circuit detection circuit includes a threshold adjuster for adjusting the short circuit threshold.

[0007] In some aspects, the battery pack interface is configured to receive a first power tool battery pack and a second power tool battery pack.

[0008] In some aspects, the first power tool battery pack and the second power tool battery pack are configured to be connected in series.

[0009] In some aspects, the short circuit detection circuit further includes an over-current condition comparator and an under-voltage condition comparator.

[0010] In some aspects, the short circuit detection circuit is further configured to provide a signal to the controller when the current in the inverter is greater than or equal to the short circuit threshold.

[0011] In some aspects, the short circuit detection circuit is further configured to monitor a voltage of the power tool, compare the voltage to an undervoltage threshold, and control a switch of the short circuit detection circuit to disable a gate driver when the voltage is less than or equal to the undervoltage threshold.

[0012] In some aspects, the short circuit detection circuit is further configured to disable the gate driver for a period of time after the current in the inverter is greater than or equal to the short circuit threshold.

[0013] In some aspects, the short circuit detection circuit is further configured to latch the gate driver into an active state and unlock the gate driver to disable the gate driver.

[0014] In some aspects, the short circuit detection circuit is further configured to monitor a second current associated with the battery pack, monitor a third current associated with the battery pack, control a switch of the short circuit detection circuit to disable the gate driver when the second current is greater than or equal to a short circuit threshold, and control a switch of the short circuit detection circuit to disable the gate driver when the third current is greater than or equal to the short circuit threshold.

[0015] The method for short circuit detection in a power tool described herein includes: measuring the current in an inverter through a current sensor; receiving a fault signal related to a fault condition (e.g., a short circuit condition) of a gate driver or inverter of the power tool; adjusting a fault threshold based on the fault signal through a threshold adjuster to generate a short circuit fault threshold; comparing the current in the inverter with the short circuit fault threshold to identify a short circuit condition of the power tool; and disabling the gate driver of the power tool in response to identifying the short circuit condition.

[0016] In some aspects, the methods further include disabling a trigger signal of the power tool in response to identifying a short circuit condition of the power tool.

[0017] In some aspects, the methods further include disabling a gate driver of the power tool for a period of time after identifying the short circuit condition.

[0018] In some aspects, the methods further include latching the gate driver into an active state, and unlocking the gate driver to disable the gate driver.

[0019] The method for short circuit detection in a power tool described herein includes: receiving a first signal related to the current in the inverter at a first comparator; comparing the first signal with a first fault threshold through the first comparator; receiving a second signal related to the voltage of the power tool at a second comparator; comparing the second signal with a second fault threshold through the second comparator; and in response to the first signal being greater than or equal to the first fault threshold or the second signal being less than or equal to the second fault threshold, using a switch to disable the gate driver of the power tool.

[0020] In some aspects, the first threshold is a hardware over-current threshold.

[0021] In some aspects, the second threshold is an undervoltage threshold.

[0022] In some aspects, the methods further include disabling a trigger signal of the power tool in response to the first signal being greater than or equal to the first fault threshold or the second signal being less than or equal to the second fault threshold.

[0023] The power tool described herein includes a housing, a motor supported by the housing, and a battery pack interface configured to receive a battery pack. The battery pack includes a plurality of battery cells. The power tool further includes an inverter positioned between the battery pack interface and the motor and electrically connected to the battery pack interface and the motor, a gate driver connected to the inverter, and a controller. The gate driver is configured to control the current in the inverter. The controller is configured to control the gate driver. The short circuit detection circuit is configured to determine a voltage associated with the battery pack, determine a short circuit overcurrent threshold based on the voltage associated with the battery pack, monitor the current in the inverter, compare the current in the inverter with the short circuit overcurrent threshold, and control the switch to disable the motor when the current in the inverter is greater than or equal to the short circuit overcurrent threshold.

[0024] In some aspects, the battery pack interface is configured to receive a first power tool battery pack and a second power tool battery pack.

[0025] In some aspects, the first power tool battery pack and the second power tool battery pack are configured to be connected in series.

[0026] In some aspects, the short circuit over-current threshold is selected from a plurality of hierarchical short circuit over-current thresholds based on the voltage associated with the battery pack.

[0027] In some aspects, the voltage associated with the battery pack is a direct current ("DC") link bus voltage.

[0028] In some aspects, the short circuit detection circuit is further configured to start a timer after the current in the inverter is greater than or equal to the short circuit overcurrent threshold, compare the timer to the timer threshold, and control a switch of the short circuit detection circuit to disable the motor when the current in the inverter is greater than or equal to the short circuit overcurrent threshold and the timer is greater than or equal to the timer threshold.

[0029] The method described herein for short circuit detection in a power tool includes: determining a voltage associated with a battery pack connected to a battery pack interface of the power tool; determining a short circuit overcurrent threshold based on the voltage associated with the battery pack; monitoring the current in an inverter of the power tool; comparing the current in the inverter to the short circuit overcurrent threshold; and controlling a switch to disable the motor of the power tool when the current in the inverter is greater than or equal to the short circuit overcurrent threshold.

[0030] In some aspects, the methods further include receiving a first power tool battery pack and a second power tool battery pack at a battery pack interface of the power tool.

[0031] In some aspects, the methods further include connecting the first power tool battery pack and the second power tool battery pack in series.

[0032] In some aspects, the methods further include selecting the short circuit over-current threshold from a plurality of hierarchical short circuit over-current thresholds based on a voltage associated with the battery pack.

[0033] In some aspects, the voltage associated with the battery pack is a direct current ("DC") link bus voltage.

[0034] In some aspects, the methods further include: starting a timer after the current in the inverter is greater than or equal to a short circuit overcurrent threshold; comparing the timer to a timer threshold; and controlling a switch to disable the motor when the current in the inverter is greater than or equal to the short circuit overcurrent threshold and the timer is greater than or equal to the timer threshold.

[0035] Before explaining any embodiment in detail, it should be understood that the embodiments are not limited to the configuration and arrangement details of the components set forth in the following description or shown in the accompanying drawings. The embodiments can be practiced or executed in various ways. In addition, it should be understood that the words and terms used herein are for illustrative purposes and should not be considered restrictive. The use of "including", "comprising" or "having" and variations thereof is intended to cover the items listed thereafter and their equivalents, as well as additional items. Unless otherwise specified or limited, the terms "mount", "connect", "support" and "couple" and variations thereof are widely used and cover both direct mounting, connection, support and coupling and indirect mounting, connection, support and coupling.

[0036] In addition, it should be understood that embodiments may include hardware, software, and electronic components or modules, which, for the purpose of discussion, may be shown and described as if most components are implemented only in hardware. However, those of ordinary skill in the art will recognize based on reading this detailed description that, in at least one embodiment, electronic-based aspects may be implemented in software (e.g., stored on a non-transient computer-readable medium) that may be executed by one or more processing units (e.g., microprocessors and / or application-specific integrated circuits ("ASICs")). Thus, it should be noted that embodiments may be implemented using a plurality of hardware- and software-based devices and a plurality of different structural components. For example, the "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 these components.

[0037] Relative terms used in conjunction with quantities or conditions, such as "about", "approximately", "substantially", etc., will be understood by those of ordinary skill in the art to include the stated value and have the meaning dictated by the context (e.g., the term includes at least the degree of error associated with measurement accuracy, the tolerance associated with a particular value [e.g., manufacturing, assembly, use, etc.], etc.). Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression "from about 2 to about 4" also discloses a range "from 2 to 4". Relative terms can refer to positive and negative percentages (e.g., 1%, 5%, 10%, or more) of the indicated value.

[0038] It should be understood that although some drawings show the hardware and software in a particular device, these depictions are for illustrative purposes only. The function described herein as being performed by a component can be performed in a distributed manner by multiple components. Likewise, the function performed by multiple components can be merged 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 between multiple electronic processors, rather than being located in a single electronic processor and performed by it. Regardless of how hardware components and software components are combined or divided, these hardware components and software components can be located on the same computing device or can be distributed between different computing devices connected by one or more networks or other suitable communication links. Similarly, the components described as performing a specific function can also perform additional functions not described herein. For example, a device or structure that is "configured" in a certain way is configured at least in this way, but can also be configured in a way that is not explicitly listed.

[0039] Other aspects of the embodiments will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1A A side view of a power tool according to some embodiments is shown.

[0041] Figure 1B A front view of a power tool according to some embodiments is shown.

[0042] Figure 2 A block diagram of a control system for a power tool according to some embodiments is shown.

[0043] Figure 3 A battery pack for use in a power tool is shown according to some embodiments.

[0044] Figure 4 A block diagram of a control system for a battery pack is shown according to some embodiments.

[0045] Figure 5 A block diagram of a short circuit detection system is shown in accordance with some embodiments.

[0046] Figure 6 A block diagram of a short circuit detection system is shown in accordance with some embodiments.

[0047] Figure 7 Circuitry for a short circuit detection system according to some embodiments is presented.

[0048] Figure 8 A process for performing short circuit mitigation using a short circuit detection system according to some embodiments is presented.

[0049] Fig. 9 A block diagram of a short circuit detection system is shown in accordance with some embodiments.

[0050] Fig. 10A and Fig. 10B Circuitry for a short circuit detection system according to some embodiments is presented.

[0051] Fig.11A and Fig. 11B A process for performing short circuit mitigation using a short circuit detection system according to some embodiments is presented.

[0052] Fig.12 A short circuit detection circuit according to some embodiments is presented.

[0053] Fig.13 Short circuit thresholds according to some embodiments are shown.

[0054] Fig.14 A process for implementing short circuit mitigation in a power tool according to some embodiments is presented.

[0055] Fig.15 A process for implementing short circuit mitigation in a power tool according to some embodiments is presented. DETAILED DESCRIPTION

[0056] Figure 1A A power tool 100 including a brushless direct current ("BLDC") motor is shown. The power tool 100 is, for example, a brushless hammer drill including a housing 102. The housing 102 includes a handle portion 104 and a motor housing portion 106. The power tool 100 further includes an output driver 108 (shown as a chuck), a trigger 110, and a battery pack interface 112. The battery pack interface 112 is configured to mechanically and electrically connect to a power tool battery pack. Although Figure 1A A hammer drill is shown, but in some embodiments, the components described herein are incorporated into other types of power tools, including drill bits, impact drivers, impact wrenches, angle grinders, circular saws, reciprocating saws, string trimmers, leaf blowers, vacuum cleaners, etc. In a brushless motor power tool such as power tool 100, the switching element is selectively enabled and disabled by a control signal from a controller to selectively apply power from a power source (e.g., a battery pack) to drive the brushless motor.

[0057] Figure 1B A power tool 150 including a BLDC motor is shown. The power tool 150 is, for example, a brushless hammer drill including a housing 152. The housing 152 includes a handle portion 154 and a motor housing portion 156. The power tool 150 further includes an output driver 158 (shown as a chuck), a trigger 160, and a battery pack interface 162. The battery pack interface 162 is configured to receive a plurality of battery packs, such as battery pack 164 and battery pack 166. Although Figure 1B A hammer drill is shown, but in some embodiments, the components described herein are incorporated into other types of power tools, including drill bits, impact drivers, impact wrenches, angle grinders, circular saws, reciprocating saws, string trimmers, leaf blowers, vacuum cleaners, and the like.

[0058] Figure 2A control system 200 of a power tool 100, 150 including a short circuit detection system is shown. The control system 200 includes a controller 202. The controller 202 is electrically and / or communicatively connected to various modules or components of the power tool 100, 150. For example, the controller 202 shown is electrically connected to a motor 204, a battery pack interface 206, a trigger switch 208 (connected to a trigger 210), one or more sensors 212 (also referred to as a sensing circuit), one or more indicators 214, a user input module 216, a power input module 218, an inverter or FET switch module 220 (e.g., including a plurality of switching FETs), and a gate driver 224 for driving the FET switch module 220. The controller 202 includes a combination of hardware and software that is operable to, among other things, control the operation of the power tool 100, 150, monitor the operation of the power tool 100, 150, activate one or more indicators 214 (e.g., LEDs), etc. A short circuit detection system or circuit 222 is connected to the controller 202 and the gate driver 224. In some embodiments, the sensor 212 measures or detects current in the inverter or FET switch module 220 (eg, current in one or more phases of the inverter).

[0059] The controller 202 includes a plurality of electrical and electronic components that provide power, operational control, and protection to the components and modules within the controller 202 and / or the power tool 100, 150. For example, the controller 202 includes, among other things, a processing unit 226 (e.g., a microprocessor, a microcontroller, an electronic controller, an electronic processor, or another suitable programmable device), a memory 228, an input unit 230, and an output unit 232. The processing unit 226 includes, among other things, a control unit 234, an arithmetic logic unit ("ALU") 236, and a plurality of registers 238, and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 226, the memory 228, the input unit 230, and the output unit 232, as well as the various modules or circuits connected to the controller 202 are connected via one or more control buses and / or data buses (e.g., a common bus 240). For purposes of illustration, the control buses and / or data buses are generally referred to as common bus 240. Figure 2 In view of the invention described herein, it is known to those skilled in the art to use one or more control buses and / or data buses for interconnection and communication between various modules, circuits and components.

[0060] The memory 228 is a non-transient computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include a combination 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 storage device, optical storage device, physical storage device or electronic storage device. The processing unit 226 is connected to the memory 228 and executes software instructions, which can be stored in the RAM of the memory 228 (e.g., during execution), the ROM of the memory 228 (e.g., on a generally permanent basis) or another non-transient computer-readable medium such as another memory or disk. The software included in the embodiments of the power tool 100, 150 can be stored in the memory 228 of the controller 400. The software includes, for example, firmware, one or more application programs, program data, filters, rules, one or more program modules and other executable instructions. The controller 202 is configured to obtain from the memory 228 and execute instructions related to the control process and method described herein, in particular. In other configurations, the controller 202 includes additional components, fewer components or different components.

[0061] The battery pack interface 206 includes a combination of mechanical components (e.g., tracks, grooves, latches, etc.) and electrical components (e.g., one or more terminals) that are configured and operable to interface (e.g., mechanically, electrically, and communicatively connect) with the battery pack. For example, the power provided by the battery pack 164, 300 to the power tool 100, 150 is provided to the power input module 218 through the battery pack interface 206. The power input module 218 includes a combination of active and passive components to adjust or control the power received from the battery pack 164, 300 before providing the power to the controller 202. The battery pack interface 206 also provides power to the FET switch module 220 switched by the switch FET to selectively provide power to the motor 204. The battery pack interface 206 also includes, for example, a communication line 242, which is used to provide a communication line or link between the controller 202 and the battery pack 164, 300. In some embodiments, the controller 202 is also electrically and / or communicatively connected to the short circuit detection circuit 222 via signal lines.

[0062] The sensor 212 includes one or more current sensors, one or more speed sensors, one or more Hall effect sensors, one or more temperature sensors, etc. The indicator 214 includes, for example, one or more light emitting diodes ("LEDs"). The indicator 214 can be configured to display the condition of the power tool 100, 150 or information associated with the power tool. For example, the indicator 214 is configured to indicate the measured electrical characteristics of the power tool 100, 150, the state of the power tool, the state of the circuit 222, etc. The user input module 216 is operably connected to the controller 202 to, for example, select a forward operating mode or a reverse operating mode for the power tool 100, 150, a torque and / or speed setting (for example, using a torque and / or speed switch to set), etc. In some embodiments, the user input module 216 includes a combination of digital and analog input or output devices required to achieve the desired operating level of the power tool 100, 150, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc.

[0063] The circuit 222 is configured to monitor one or more electrical characteristics of the power tool 100, 150 for a condition indicative of a short circuit fault condition. For example, in some embodiments, the circuit 222 monitors one or more electrical characteristics of a plurality of switching FETs of the FET switch module 220 for a condition indicative of a shoot-through. For example, in some embodiments, the circuit 222 monitors one or more electrical characteristics of the motor 204 for a condition indicative of a locked rotor. In some embodiments, when the circuit 222 determines that the one or more electrical characteristics indicate a short circuit fault condition, the circuit 222 commands the gate driver 224 to prevent the FET switch module 220 from providing power to the motor 204. In some embodiments, the circuit 222 determines that the one or more electrical characteristics indicate an undesirable current, an uncontrolled current, a destructive current, a dangerous current, etc.

[0064] Figure 3 A battery pack 300 is shown. The battery pack 300 includes a housing 302 and an interface portion 304 for connecting the battery pack 300 to a power tool, such as power tools 100, 150. In some embodiments, the battery pack 300 has a rated nominal voltage of 18 volts.

[0065] Figure 4 A control system for a battery pack 300 is shown. The control system includes a controller 400. The controller 400 is electrically and / or communicatively connected to various modules or components of the battery pack 300. For example, the controller 400 is shown connected to one or more battery cells 402 and an interface 404 (e.g., Figure 34). The controller 400 is also connected to one or more voltage sensors or voltage sensing circuits 406, one or more current sensors or current sensing circuits 408, and one or more temperature sensors or temperature sensing circuits 410. The controller 400 includes a combination of hardware and software that are operable to, among other things, control the operation of the battery pack 300, monitor the condition of the battery pack 300, enable or disable charging of the battery pack 300, enable or disable discharging of the battery pack 300, etc.

[0066] The controller 400 includes a plurality of electrical and electronic components that provide power, operational control, and protection for the components and modules within the controller 400 and / or the battery pack 300. For example, the controller 400 includes, among other things, a processing unit 412 (e.g., a microprocessor, a microcontroller, an electronic processor, an electronic controller, or another suitable programmable device), a memory 414, an input unit 416, and an output unit 418. The processing unit 412 includes, among other things, a control unit 420, an ALU 422, and a plurality of registers 424, and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 412, the memory 414, the input unit 416, and the output unit 418, as well as the various modules or circuits connected to the controller 400, are connected via one or more control buses and / or data buses (e.g., a common bus 426). For illustrative purposes, the common bus 426 is used to represent the control unit 412. Figure 4 The control bus and / or data bus are generally shown in FIG. In view of the utility model described herein, it is known to those skilled in the art to use one or more control buses and / or data buses for interconnection and communication between various modules, circuits and components.

[0067] The memory 414 is a non-transient computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include a combination 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 storage device, optical storage device, physical storage device or electronic storage device. The processing unit 412 is connected to the memory 414 and executes software instructions, which can be stored in the RAM of the memory 414 (e.g., during execution), the ROM of the memory 414 (e.g., on a generally permanent basis) or another non-transient computer-readable medium such as another memory or disk. The software included in the embodiment of the battery pack 300 can be stored in the memory 414 of the controller 400. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules and other executable instructions. The controller 400 is configured to obtain from the memory 414 and execute instructions related to the control process and method described herein in particular. In other configurations, the controller 400 includes additional components, fewer components or different components.

[0068] The interface 404 includes a combination of mechanical components (e.g., tracks, grooves, latches, etc.) and electrical components (e.g., one or more terminals) that are configured and operable to interface (e.g., mechanically, electrically, and communicatively connect) the battery pack 300 with another device (e.g., a power tool, a battery pack charger, etc.). For example, the interface 404 is configured to be communicatively connected to the controller 400 via a communication line 428.

[0069] Figure 5 A short circuit detection system or circuit 222 is shown. The circuit 222 is configured to determine whether one or more fault conditions exist in the power tool 100, 150, and to generate one or more control signals associated with the presence of the one or more fault conditions. For example, the circuit 222 is configured to detect an undervoltage condition of one or more battery cells 402 or the battery pack 300, and an overcurrent condition (e.g., run-through, rotor locked) of the motor 204. The circuit 222 includes a short circuit detection circuit 500 electrically coupled to a switch 502. An interlock signal trigger 504 provides electrical signals to gate drivers 506, which control FET switch modules 508 (e.g., including multiple switch FETs). A power input 510 (such as a power input provided by the battery pack 300) is electrically coupled to the FET switch module 508. In some embodiments, the interlock signal trigger 504 commands the gate driver 506 to drive the FET switch module 508 to allow current to flow from the power input 510 to the motor 204.

[0070] If the circuit 222 detects one or more fault conditions of the power tool 100, 150, the circuit 222 disables the operation of the device. For example, when the short circuit detection circuit 500 detects a fault condition, the short circuit detection circuit opens the switch 502, thereby triggering the gate disable driver 512. The gate disable driver 512 interrupts the interlock signal trigger 504 and prevents the gate driver 506 from driving the motor 204. In some embodiments, the one or more fault conditions are undesirable current, uncontrolled current, destructive current, dangerous current, etc. In some embodiments, the circuit disables the device for a predetermined period of time. In some embodiments, the switch 502 is latched in an active state and is unlocked to open the switch 502 (e.g., to disable the gate driver 506).

[0071] Figure 6An exemplary embodiment of a short circuit detection system 222 as a short circuit detection system or circuit 600 is shown. The circuit 600 shown does not require firmware (e.g., the circuit 600 can run independently of the controller 202). The circuit 600 includes a shunt and an amplifier 602, which is configured to receive an electrical signal. In some embodiments, the electrical signal is a back electromotive force signal. In some embodiments, the electrical signal is a current sensing signal associated with the current through the motor 204. In an exemplary embodiment, the shunt and amplifier 602 are coupled to the inverter 604 (e.g., electrically, communicatively), and receive an electrical signal (such as an inverter signal 606) from the inverter 604, and amplify the inverter signal to determine a current measurement value. In some embodiments, the inverter 604 includes a plurality of inverter phases, and the short circuit detection system or circuit 222 is configured to monitor the plurality of inverter phases. In some embodiments, the short circuit detection system or circuit 222 is configured to monitor one inverter phase among the plurality of inverter phases. In some embodiments, the short circuit detection system or circuit 222 is configured to monitor more than one inverter phase in a plurality of inverter phases. In some embodiments, the circuit 222 is configured to monitor the current from the battery pack, the current returning to the battery pack, or the current from and returning to the battery. The filter 608 filters the current measurement of the inverter signal 606 to have a time (e.g., hysteresis) such as a fast rise and a slow decay. In addition, the circuit 600 includes a first buffer and hold stage 610 for receiving a fault signal 612. In some embodiments, the fault signal 612 is a digital fault signal from the gate driver 224 or the FET switch module 220. The fault signal indicates a short circuit condition of the motor 204, for example. The first buffer and hold stage 610 provides an electrical impedance between the fault signal 612 and the threshold adjuster 614. The fault condition persistence (e.g., the duration of the fault activity) can be set to, for example, a time delay in the first buffer and hold stage 610 or can be set using a latch. In some embodiments, the threshold adjuster 614 changes the overcurrent threshold in response to the fault signal 612. In some embodiments, the threshold adjuster 614 changes the overcurrent threshold by a configurable amount of time (e.g., 1 ms, 1 s, etc.). In some embodiments, the threshold adjuster 614 changes the overcurrent threshold by a configurable magnitude (e.g., 1 mA, 1 A, etc.). By changing the overcurrent threshold, a short circuit can be more reliably detected and can be distinguished from other high current conditions that the power tool 100, 150 may encounter.

[0072] The circuit 600 includes a comparator 616. In some embodiments, the comparator 616 is an operational amplifier. In some embodiments, the comparator 616 is a differential amplifier. The comparator 616 is coupled to the threshold adjuster 614 and the filter 608 (e.g., electrically, communicatively). The comparator 616 is configured to compare the current measurement of the inverter signal 606 with the overcurrent threshold. For example, if the comparator 616 determines that the electrical signal has exceeded the overcurrent threshold set by the threshold adjuster 614, the comparator 616 generates a fault condition signal 618 and outputs the fault condition signal 618 to the second buffer holding stage 620. In some embodiments, the second buffer and holding stage 620 provides an electrical impedance between the comparator 616 and the locking stage 622. In some embodiments, the locking stage 622 prevents the gate driver 506 from driving the motor 204. In some embodiments, the locking stage 622 disables the trigger signal. After the lockout stage 622, the gate driver 506 and / or the trigger signal can be re-enabled at the re-enable stage 624 (e.g., after the short circuit condition has ended), and the power tool can operate normally again. In some embodiments, the circuit 600 provides a non-functional signal to the controller 202 to notify the controller 202 that the fault condition is active. In some embodiments, the fault condition is one or more of an undesirable current, an uncontrolled current, a destructive current, a dangerous current, etc.

[0073] Figure 7An exemplary embodiment of a short circuit detection system or circuit 222, 600 is shown. The circuit 222, 600 includes a circuit system 700. In the illustrated exemplary embodiment of the circuit 222, 600, the circuit system 700 includes a comparator 702. In some embodiments, the comparator 702 performs a function similar to the comparator 616. The circuit system 700 includes an electrical signal input, such as an inverter signal 704. The circuit system 700 includes a shunt 706 and a filter 708. In some embodiments, the shunt 706 and the filter 708 perform functions similar to the shunt and amplifier 602 and the filter 608, respectively. For example, the shunt 706 provides a current measurement of the inverter signal 704, and the filter 708 provides filtering of the inverter signal 704. In some embodiments, the filter 708 is a low pass filter configured to bias the inverter signal 704 to have, for example, a fast rise time and a slow decay time. The circuit system 700 includes a fault signal 710. In some embodiments, the fault signal 710 is a digital signal. The circuit system 700 includes a first buffer and hold stage 712 for receiving a fault signal 710. The first buffer and hold stage 712 provides an electrical impedance between the fault signal 710 and a threshold adjuster 714. In some embodiments, the threshold adjuster 714 performs a function similar to the threshold adjuster 614. In some embodiments, the threshold adjuster 714 changes the overcurrent threshold in response to the fault signal 710. In some embodiments, the threshold adjuster 714 changes the overcurrent threshold by a configurable amount of time (e.g., 1 ms, 1 s, etc.). In some embodiments, the threshold adjuster 714 changes the overcurrent threshold by a configurable magnitude (e.g., 1 mA, 1 A, etc.).

[0074] In some embodiments of the circuit system 700 of the circuit 222, 600, the comparator 702 is an operational amplifier. In some embodiments, the comparator 616 is a differential amplifier. The comparator 702 is coupled to the threshold adjuster 714 and the filter 708 (e.g., electrically, communicatively) and is configured to compare the current measurement of the inverter signal 704 with the overcurrent threshold. For example, if the comparator 702 determines that the electrical signal has exceeded the overcurrent threshold set by the threshold adjuster 714, the comparator 702 generates a fault condition signal 716. The comparator 702 outputs the fault condition signal 716 to the second buffer and hold stage 718. In some embodiments, the second buffer and hold stage 718 provides an electrical impedance between the comparator 702 and the lock stage 720. In some embodiments, the lock stage 720 prevents the gate driver 506 from driving the motor 204. In some embodiments, the lock stage 720 disables the trigger signal.

[0075] Figure 8A process 800 for detecting a short circuit in a power tool is shown. In some embodiments, the process 800 is implemented by the circuit 600. In some embodiments, the process 800 is implemented by the circuit system 700 of the circuit 600. The process 800 begins at step 802, i.e., measuring an electrical signal of the power tool 100, 150, such as an inverter signal 606, 704. In some embodiments, the measured electrical signal of the power tool corresponds to one of a plurality of inverter phases. In some embodiments, the short circuit detection system is configured to monitor the current from the battery pack, the current returned from the battery pack, or the current from and returned to the battery pack. The process 800 then proceeds to step 804, in which the inverter signal 606, 704 is amplified, for example, by the amplifier 602. The process 800 then proceeds to step 806, in which the inverter signal 606, 704 is filtered, for example, by the filter 608, 708. The process 800 then proceeds to step 808, where the fault signal (e.g., the fault signal 612, 710) is received by a buffer (e.g., the first buffer and hold stage 610, 712). The process 800 then proceeds to step 810, where the fault signal is adjusted, such as by a threshold adjuster 614, 714, to generate an overcurrent threshold. The process 800 then proceeds to step 812, where a comparator (e.g., comparator 616, 702) compares the signal (e.g., the inverter signal 606, 704) to the overcurrent threshold generated in step 810. If, at step 814, the measured electrical signal does not indicate a fault condition, for example, if the inverter signal 606, 704 does not exceed the overcurrent threshold, the process 800 proceeds to step 802. If at step 814, the measured electrical signal indicates a fault condition, for example, if the inverter signal 606, 704 exceeds an overcurrent threshold, the process 800 proceeds to step 816, in which the fault condition is output, for example, by the comparator 616, 702. The process 800 then proceeds to step 818, in which the fault condition signal is buffered, for example, by the second buffer and hold stage 620, 718. The process 800 then proceeds to step 820, in which the short circuit detection system 600 disables the power tool 100, 150. In some embodiments, the short circuit detection system 600 disables the power tool 100, 150 by preventing the gate driver 506 from driving the motor 204. In some embodiments, the short circuit detection system 600 disables the power tool 100, 150, disabling the trigger signal.

[0076] Fig. 9An exemplary embodiment of a short circuit detection system or circuit 900 is shown. The circuit 900 shown does not require firmware (e.g., the circuit 900 can run independently of the controller 202). The circuit 900 includes a first comparator 902. In some embodiments, the comparator 902 is an overcurrent comparator. The circuit 900 also includes a second comparator 904. In some embodiments, the comparator 904 is an undervoltage comparator. In other embodiments, different signals are used, and short circuits can be detected using back electromotive force, Hall effect sensors, sensed three-phase currents, etc. In some embodiments, the comparators 902, 904 are operational amplifiers. In some embodiments, the comparators 902, 904 are differential amplifiers. In some embodiments, the comparators 902, 904 are a combination of differential amplifiers, operational amplifiers, and / or any other type of suitable amplifiers. In an exemplary embodiment, the first comparator 902 is coupled to the inverter 906 (e.g., electrically, communicatively) and receives an electrical signal from the inverter 906, such as an inverter signal 908. In some embodiments, the inverter 906 includes a plurality of inverter phases, and the short circuit detection system or circuit 900 is configured to monitor the plurality of inverter phases. In some embodiments, the short circuit detection system or circuit 900 is configured to monitor one inverter phase in the plurality of inverter phases. In some embodiments, the short circuit detection system or circuit 900 is configured to monitor more than one inverter phase in the plurality of inverter phases. In some embodiments, the circuit 900 is configured to monitor the current from the battery pack, the current returned to the battery pack, or the current from and returned to the battery pack. The comparator 902 is configured to receive a first fault threshold or overcurrent threshold 910 from a hardware overcurrent threshold adjuster 912 (also referred to as a threshold adjuster or overcurrent threshold adjuster). The comparator 902 is configured to compare the current measurement of the inverter signal 908 with the overcurrent threshold 910. For example, if the comparator 902 determines that the electrical signal has exceeded the overcurrent threshold set by the threshold adjuster 912, the comparator 902 generates a fault condition signal 914 and outputs the fault condition signal 914. In some embodiments, the comparator 902 may determine that the electrical signal indicates one or more fault conditions, such as undesirable current flow, uncontrolled current flow, destructive current flow, hazardous current flow, and the like.

[0077] In an exemplary embodiment, the second comparator 904 is coupled to the DC link voltage 916 (e.g., electrically, communicatively) and receives an electrical signal, such as a voltage measurement 918, from the DC link voltage 916. The comparator 904 is configured to receive a second fault threshold or undervoltage threshold 920 from an undervoltage threshold adjuster 922. The comparator 904 is configured to compare the voltage measurement 918 to the undervoltage threshold 920. For example, if the comparator 904 determines that the electrical signal is less than or equal to the undervoltage threshold set by the undervoltage threshold adjuster 922, the comparator 904 generates a fault condition signal 914 and outputs the fault condition signal 914.

[0078] When comparator 902 or comparator 904 or a combination of comparators 902, 904 (i.e., AND-OR logic configuration) has generated a fault condition, a fault condition signal 914 is output to a first filter 924. In some embodiments, filter 924 is a low pass filter. The fault condition signal 914 is then sent to a first threshold and buffer stage 926. In some embodiments, threshold and buffer stage 926 adjusts the fault condition signal 914 and provides a high input electrical impedance for the outputs of comparator 902 and comparator 904. The first threshold and buffer stage 926 then sends the fault condition signal 914 to a second filter 928. The fault condition persistence (e.g., fault activity duration) can be set, for example, to a time delay in the first threshold and buffer stage 926 or can be set using a latch. In some embodiments, filter 928 is a low pass filter. The fault condition signal 914 is then sent to a second threshold and buffer stage 930. In some embodiments, the first buffer 926 delays the fault condition signal 914 by a configurable amount of time (e.g., 0s, 1ms, 1s, etc.). In some embodiments, the second buffer 930 also delays the fault condition signal 914 by a configurable amount of time. The fault condition signal 914 is then provided to a switch 932. In some embodiments, the switch 932 is coupled (e.g., electrically, communicatively) to the gate driver 224, 506. In some embodiments, the switch 932 controls the interlock signal trigger 504, which provides an electrical signal to the gate driver 224, 506 to control the FET switch module 220, 508 (e.g., including a plurality of switching FETs). In some embodiments, the switch 932 is configured to prevent the gate driver 224, 506 from controlling the FET switch module 508, thereby disabling the power tool 100, 150. In some embodiments, the circuit 900 provides a non-functional signal to the controller 202 to notify the controller 202 that the fault condition is active.

[0079] Fig. 10A and Fig. 10B An exemplary embodiment of a short circuit detection system or circuit 222, 900 is shown. The circuit 222, 900 includes a circuit system 1000. Fig. 10A A portion of an embodiment of a circuit system 1000 is shown, including one or more comparators 1002. In some embodiments, comparator 1002 performs functions similar to comparator 902 and comparator 904. Comparator 1002 is configured to receive a first electrical signal, such as a current measurement 1004 of an inverter signal. In some embodiments, current measurement 1004 of inverter signal 908 is similar to current measurement. Comparator 1002 is configured to receive overcurrent threshold 1006 from overcurrent threshold adjuster 1008. In some embodiments, overcurrent threshold 1006 is similar to overcurrent threshold 910, and overcurrent threshold adjuster 1008 is similar to overcurrent threshold adjuster 912. Comparator 1002 is configured to compare current measurement 1004 with overcurrent threshold 1006 to determine whether a fault condition has occurred. For example, if the comparator 1002 determines that the current measurement 1004 is greater than or equal to the overcurrent threshold set by the threshold adjuster 1008, the comparator 1002 generates a fault condition signal 1010 and outputs the fault condition signal 1010. In some embodiments, the comparator 1002 is configured to receive a second electrical signal, such as a voltage measurement 1012. In some embodiments, the voltage measurement 1012 is similar to the voltage measurement 918. The comparator 1002 is configured to receive an undervoltage threshold 1014 from an undervoltage threshold adjuster 1016. In some embodiments, the undervoltage threshold 1014 is similar to the undervoltage threshold 920, and the overcurrent threshold adjuster 1008 is similar to the overcurrent threshold adjuster 912. The comparator 1002 is configured to compare the voltage measurement 1012 with the undervoltage threshold 1014 to determine whether a fault condition has occurred. For example, if the comparator 1002 determines that the voltage measurement 1012 is greater than or equal to the undervoltage threshold 1014 set by the threshold adjuster 1016 , the comparator 1002 generates a fault condition signal 1010 and outputs the fault condition signal 1010 .

[0080] Fig. 10BAnother portion of the circuit system 1000 is shown. The fault condition signal 1010 is provided from the comparator 1002 to the first filter 1018. In some embodiments, the filter 1018 is similar to the filter 924. The fault condition signal 1010 is then provided to the first threshold and buffer stage 1020. In some embodiments, the first threshold and buffer stage 1020 is similar to the threshold and buffer stage 926. The fault condition signal 1010 then passes through the second filter stage 1024. In some embodiments, the second filter 1024 is similar to the filter 928. In some embodiments, more or fewer filters are included. In some embodiments, more or fewer threshold and buffer stages are included, such as the threshold and buffer stages 1020, 1022. The fault condition signal 1010 is then provided to the second threshold and buffer stage 1026. In some embodiments, the second threshold and buffer stage 1026 is similar to the threshold and buffer stage 930. The second threshold and buffer stage 1026 outputs a disable signal 1028. In some embodiments, the disable signal 1028 is configured to prevent the gate driver 224, 506 from controlling the FET switch module 220, 508, thereby disabling the power tool 100, 150. In some embodiments, a latch circuit 1030 is provided to prevent the disable signal 1028 from being incorrectly output. The latch circuit includes a diode 1032, 1034 (e.g., a Zener diode).

[0081] Fig.11A and Fig. 11B A process 1100 of detecting a short circuit in a power tool is shown. In some embodiments, the process 1100 is implemented by the short circuit detection system 900. In some embodiments, the process 1100 is implemented by the circuitry 1000 of the short circuit detection system 900. Fig.11A A portion of process 1100 is shown and begins at step 1102. At step 1102, the comparator 902, 1002 receives an electrical signal from the power tool 100, 150, such as a current measurement of an inverter signal. In some embodiments, the measured electrical signal of the power tool corresponds to one or more inverter phases of a plurality of inverter phases. In some embodiments, the short circuit detection system is configured to monitor current from the battery pack, current returning to the battery pack, or current from and returning to the battery pack. Process 1100 then proceeds to step 1104, where an overcurrent threshold 910, 1006 is received by the comparator 902, 1002. Process 1100 then proceeds to step 1106, where the comparator compares the current measurement to the overcurrent threshold of step 1104. At step 1108, if the measured electrical signal indicates a fault condition, for example, if the current measurement exceeds the overcurrent threshold, process 1100 proceeds to step 1118 (see Fig. 11B ).

[0082] At step 1108, if the current measurement does not indicate a fault condition, the process 1100 proceeds to step 1110. The process 1100 continues to step 1110 by receiving the voltage measurement 918, 1012 by the comparator 904, 1002. The process 1100 then proceeds to step 1112 by receiving a voltage threshold, such as an undervoltage threshold 920, 1014, by the comparator 904, 1002. The process 1100 then proceeds to step 1114, in which the comparator 904, 1002 compares the voltage measurement 918, 1012 to the undervoltage threshold. At step 1116, if the voltage measurement 918, 1012 does not indicate a fault condition, the process 1100 returns to step 1102. At step 1116, if the voltage measurement 918, 1012 indicates a fault condition, the process 1100 proceeds to step 1118 (see Fig. 11B ).

[0083] Fig. 11B Another portion of the process 1100 is shown, and continues to step 1118, in which the comparator 902, 904, 1002 determines that a fault condition has occurred. At step 1118, if the comparator 902, 904, 1002 determines that a fault condition has not occurred, the process 1100 returns to step 1102. If the comparator 902, 904, 1002 determines that a fault condition has occurred, such as an overcurrent condition or an undervoltage condition, the comparator 902, 904, 1002 generates a fault condition signal 914, 1010. The process 1100 then proceeds to step 1120, in which the comparator 902, 904, 1002 outputs the fault condition signal 914, 1010 to the filter 924, 1018. The process 1100 then proceeds to step 1122, where the filter 924, 1018 receives and filters the fault condition signal 914, 1010. The process 1100 then proceeds to step 1124, where the buffer 926, 1020 buffers the fault condition signal 914, 1010. The process 1100 then proceeds to step 1126, where the filter 928, 1024 filters the fault condition signal 914, 1010. The process 1100 then proceeds to step 1128, where the buffer 930, 1022 buffers the fault condition signal 914, 1010. The process 1100 then proceeds to step 1130, where the switch 932 disables the power tool 100, 150. In some embodiments, the short circuit detection system 900 disables the power tool 100, 150 by disabling the trigger signal. In some embodiments, the short circuit detection system 900 disables the power tool 100 , 150 by preventing the gate driver 506 from driving the motor 204 .

[0084] Fig.12 Another embodiment of a short circuit detection circuit 1200 is shown. The short circuit detection circuit 1200 includes a programmable integrated circuit 1205 configured to monitor a short circuit condition of a power tool 100, 150. The circuit 1205 (e.g., the short circuit detection system 222) is powered by a supply voltage (e.g., 3.3V, 5V, etc.). The circuit 1205 receives an input voltage signal related to the battery pack voltage. In some embodiments, the input voltage signal corresponds to the voltage of the battery pack. In other embodiments, the input voltage signal corresponds to a DC link bus voltage (e.g., a system bus voltage) that may have a value different from the battery pack voltage. The circuit 1205 also receives one or more input current signals (e.g., phase A, phase B, phase C, etc.). The one or more input current signals correspond to the current through the inverter or FET switch module 220 and the motor 204. If a multi-phase current is provided to the motor 204, a current sensor can be used to detect the current in each phase. If the circuit 1205 detects a short circuit condition, the circuit 1205 provides an output 1210 to a switch 1215 to disable the motor 204 (e.g., disable the gate driver driving the switch 1215). Although only one switch is shown, multiple switches (e.g., in an inverter or FET switch module 220) are similarly controlled to disable the motor 204. The power 1220 from the battery pack is then prevented from driving the motor 204.

[0085] Circuit 1205 is programmed to include multiple different short-circuit overcurrent thresholds. In some embodiments, a specific short-circuit overcurrent threshold is preselected for a specific power tool application (e.g., based on the platform voltage). In some embodiments, circuit 1205 is configured to dynamically adjust the short-circuit overcurrent threshold based on a voltage associated with the power tool (e.g., a battery pack voltage or a DC link bus voltage). The higher the voltage value, the higher the short-circuit overcurrent threshold can be set. For example, a larger battery pack including a higher voltage and capacity can have a lower DC internal resistance than other battery packs. For such a battery pack capable of outputting a higher current, the short-circuit overcurrent threshold can be increased.

[0086] Fig.13 Graph 1300 illustrates short circuit overcurrent thresholds according to some embodiments. Fig.13The values ​​shown in are merely exemplary and are provided for the purpose of description. Different thresholds can be used for different power tool applications. As the voltage associated with the battery pack or DC link voltage increases, the short circuit overcurrent threshold 1305 also increases. In some embodiments, the short circuit overcurrent threshold 1305 is based on the voltage of one or more battery packs connected to the power tool 100, 150. When one or more battery packs are exhausted, the short circuit overcurrent threshold 1305 can be modified. In other embodiments, the short circuit overcurrent threshold 1305 is based on the DC link bus voltage (for example, in the case where multiple battery packs can be attached to the power tool 100, 150). The area below the short circuit overcurrent threshold 1305 corresponds to the operating range of the power tool 100, 150. In some embodiments, the time aspect of the short circuit overcurrent threshold can be implemented, rather than the short circuit overcurrent threshold being only the current value for disabling the motor when exceeded. For example, before disabling the motor, it is necessary to exceed the short circuit overcurrent threshold for a period of time. By including time as a condition for disabling the motor, different time thresholds can be set. For example, a relatively high current value can be allowed to last for a short period of time, and a relatively low current value can be allowed to last for a longer period of time. Configuring the short circuit overcurrent threshold in this manner provides greater flexibility to extract as much power as possible from the battery pack(s).

[0087] Fig.14 A process 1400 for controlling a power tool 100, 150 is shown. At step 1405, the circuit 1205 determines a voltage associated with the battery pack(s) of the power tool 100, 150. As described above, the voltage may be the voltage of one or more battery packs or a DC link bus voltage. Based on the determined voltage, the circuit 1205 determines or selects a short circuit overcurrent threshold (step 1410). The circuit 1205 then monitors the current through the inverter or FET switch module 220 and the motor 204 (step 1415). In some embodiments, the current is monitored by one or more current sensors (e.g., shunt resistors) that detect the current through the motor 204. The circuit 1205 compares the measured current with the short circuit overcurrent threshold (step 1420). If the measured current is not greater than or equal to the short circuit overcurrent threshold, the process 1400 returns to step 1415, where the current is continuously monitored. At step 1420, if the measured current is greater than the short circuit overcurrent threshold, the power tool 100, 150 is disabled (step 1425). The power tool 100, 150 is disabled by controlling the gate driver of the switch to disable the switch (e.g., in the FET switch module 220) and thereby preventing current from passing through the motor 204.

[0088] Fig.15A process 1500 for controlling a power tool 100, 150 is shown. At step 1505, the circuit 1205 determines a voltage associated with the battery pack(s) of the power tool 100, 150. As described above, the voltage may be the voltage of one or more battery packs or a DC link bus voltage. Based on the determined voltage, the circuit 1205 determines or selects a short circuit overcurrent threshold (step 1510). The circuit 1205 then monitors the current through the inverter or FET switch module 220 and the motor 204 (step 1515). In some embodiments, the current is monitored by one or more current sensors (e.g., shunt resistors) that detect the current through the motor 204. The circuit 1205 compares the measured current with the short circuit overcurrent threshold (step 1520). If the measured current is not greater than or equal to the short circuit overcurrent threshold, the process 1500 returns to step 1515, where the current is continuously monitored.

[0089] At step 1520, if the measured current is greater than the short circuit overcurrent threshold, the circuit starts a timer or counter (step 1525). The timer or counter is implemented to determine whether the short circuit condition that may exist persists for a period of time (e.g., rather than just a transient current spike). In some embodiments, the circuit 1205 includes an internal clock (e.g., a real-time clock) for recording time, and a separate dedicated timer or counter is not required. However, for the purpose of explanation, the timer is generally described as a way to record the elapsed time. At step 1530, if the timer is equal to or greater than the timer threshold (i.e., a specified amount of time has passed), the power tool 100, 150 is disabled (step 1535). The power tool 100, 150 is disabled by controlling the gate driver of the switch to disable the switch (e.g., in the FET switch module 220) and thereby prevent current from passing through the motor 204. At step 1530, if the timer is less than the timer threshold, the process 1500 returns to step 1515 to continue monitoring the current and step 1525 to increment the timer. If the measured current drops back below the short circuit overcurrent threshold before the timer reaches the timer threshold, the timer is stopped or reset and the power tool 100 , 150 will continue to operate normally.

[0090] Thus, the embodiments described herein provide short circuit mitigation for power tools. Various features and advantages are set forth in the following claims.

Claims

1. A power tool, characterized in that: include: case; a motor supported by the housing; a battery pack interface configured to receive a battery pack including a plurality of battery cells; an inverter positioned between and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter, the gate driver configured to control current in the inverter; a controller configured to control the gate driver; as well as A short circuit detection circuit is configured to: Monitor the current in the inverter, comparing the current in the inverter to a short circuit threshold, and When the current in the inverter is greater than or equal to the short-circuit threshold, the switch of the short-circuit detection circuit is controlled to disable the gate driver.

2. The power tool according to claim 1, wherein: The short circuit detection circuit includes a threshold adjuster for adjusting the short circuit threshold.

3. The power tool according to claim 1, wherein: The battery pack interface is configured to receive a first power tool battery pack and a second power tool battery pack.

4. The power tool according to claim 3, wherein: The first power tool battery pack and the second power tool battery pack are configured to be connected in series.

5. The power tool according to claim 1, wherein: The short circuit detection circuit further includes an over-current condition comparator and an under-voltage condition comparator.

6. The power tool according to claim 1, wherein: The short circuit detection circuit is further configured to provide a signal to the controller when the current in the inverter is greater than or equal to the short circuit threshold.

7. The power tool according to claim 1, wherein: The short circuit detection circuit is further configured to: Monitor the voltage of the power tool, This voltage is compared to the undervoltage threshold, and When the voltage is less than or equal to the under-voltage threshold, a switch of the short-circuit detection circuit is controlled to disable the gate driver.

8. The power tool according to claim 1, wherein: The short circuit detection circuit is further configured to disable the gate driver for a period of time after the current in the inverter is greater than or equal to the short circuit threshold.

9. The power tool according to claim 1, wherein: The short circuit detection circuit is further configured to: latches the gate driver as active, and The gate driver is unlocked to disable the gate driver.

10. The power tool according to claim 1, wherein: The short circuit detection circuit is further configured to: monitoring a second current associated with the battery pack; monitoring a third current associated with the battery pack; When the second current is greater than or equal to the short-circuit threshold, controlling a switch of the short-circuit detection circuit to disable the gate driver, and When the third current is greater than or equal to the short-circuit threshold, a switch of the short-circuit detection circuit is controlled to disable the gate driver.

11. A power tool, characterized in that: include: case; a motor supported by the housing; a battery pack interface configured to receive a battery pack including a plurality of battery cells; an inverter positioned between and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter, the gate driver configured to control current in the inverter; a controller configured to control the gate driver; as well as A short circuit detection circuit is configured to: Determine the voltage associated with the battery pack, determining a short circuit overcurrent threshold based on the voltage associated with the battery pack, Monitor the current in the inverter, comparing the current in the inverter with the short circuit overcurrent threshold, and When the current in the inverter is greater than or equal to the short circuit overcurrent threshold, the switch is controlled to disable the motor.

12. The power tool according to claim 11, wherein: The battery pack interface is configured to receive a first power tool battery pack and a second power tool battery pack.

13. The power tool according to claim 12, wherein: The first power tool battery pack and the second power tool battery pack are configured to be connected in series.

14. The power tool according to claim 11, wherein: The short circuit over-current threshold is selected from a plurality of hierarchical short circuit over-current thresholds based on the voltage associated with the battery pack.

15. The power tool according to claim 14, wherein: The voltage associated with the battery pack is the DC link bus voltage.

16. The power tool according to claim 11, wherein: The short circuit detection circuit is further configured to: starting a timer after the current in the inverter is greater than or equal to the short-circuit overcurrent threshold; comparing the timer to a timer threshold; as well as When the current in the inverter is greater than or equal to the short circuit overcurrent threshold and the timer is greater than or equal to the timer threshold, the switch of the short circuit detection circuit is controlled to disable the motor.

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