Electric tool

Abstract

A power tool includes a housing, a motor supported by the housing, an inverter located between and electrically connected to a battery pack interface and the motor, a gate driver connected to the inverter, a rotational position detector configured to detect a position of the motor, a controller configured to control the gate driver, and a short circuit detection circuit. And a short-circuit detection circuit configured to monitor a current in the inverter, compare the current in the inverter with a first current threshold, determine whether a position of the motor is changed according to a signal from the rotation position detector when the current in the inverter is greater than or equal to the first current threshold, and determine whether the position of the motor is changed according to the signal from the rotation position detector when the current in the inverter is greater than or equal to the first current threshold. And controlling a switch of the short circuit detection circuit to disable the gate driver when the position of the motor is not changed.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 584,706, filed on September 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments described in this utility model relate to short circuit detection and short circuit protection for power tools. Background Technology

[0004] Power tools include circuitry for controlling the power tool motor. To prevent damage to the motor and power electronics and to extend the lifespan of the power tool, circuitry can be installed in the power tool to detect and prevent harmful conditions such as short circuits. Utility Model Content

[0005] 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 includes multiple battery cells), an inverter located between and electrically connected to the battery pack interface and the motor, a gate driver connected to the inverter (the gate driver is configured to control current in the inverter), a rotary position detector configured to detect the position of the motor, 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 the first current threshold, determine whether the position of the motor has changed based on a signal from the rotary position detector when the current in the inverter is greater than or equal to the first current threshold, and control the switch of the short-circuit detection circuit to disable the gate driver when the position of the motor has not changed.

[0006] In some respects, the power tool includes an indicator for indicating the status of the short-circuit detection circuit.

[0007] In some respects, the rotary position detector includes a plurality of Hall effect sensors, each configured to provide a Hall effect sensor signal corresponding to the position of the motor rotor.

[0008] In some respects, the short-circuit detection circuit is further configured to select a first current threshold based on the voltage supplied by the battery pack to the battery pack interface.

[0009] In some respects, the short-circuit detection circuit is further configured to adjust the first current threshold according to changes in the current in the inverter.

[0010] In certain aspects, the short circuit detection circuit is further configured to: determine whether an expected braking time has elapsed; compare the current in the inverter to the first current threshold when the expected braking time has elapsed; 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 first current threshold and the expected braking time has elapsed.

[0011] In certain aspects, the short circuit detection circuit is further configured to: determine whether a stall time has elapsed when the position of the motor has not changed; and control a switch of the short circuit detection circuit to disable the gate driver when the stall time has elapsed.

[0012] In certain aspects, the power tool includes a trigger configured to be actuated. The short circuit detection circuit is further configured to: detect actuation of the trigger; drive the motor when the trigger is actuated; and compare the current in the inverter to the first current threshold when the trigger is released while driving the motor.

[0013] In certain aspects, the short circuit detection circuit is further configured to enable the gate driver when the trigger is actuated and the current in the inverter is less than the first current threshold.

[0014] The method includes a method of controlling a power tool. The method includes monitoring, with a short circuit detection circuit, a current in an inverter, the inverter being located between and electrically connected to a battery pack interface and a motor; and comparing, with the short circuit detection circuit, the current in the inverter to a first current threshold. The method includes: determining, with the short circuit detection circuit, whether a position of the motor has changed based on a signal from a rotational position detector when the current in the inverter is greater than or equal to the first current threshold; and controlling, with the short circuit detection circuit, a switch of the short circuit detection circuit to disable a gate driver when the position of the motor has not changed, the gate driver being configured to control the current in the inverter.

[0015] In certain aspects, the method includes providing an indication of a status of the short circuit detection circuit with an indicator.

[0016] In certain aspects, the method includes receiving a battery pack through the battery pack interface and selecting the first current threshold based on a voltage provided to the battery pack interface by the battery pack.

[0017] In certain aspects, the method includes adjusting the first current threshold based on a change in the current in the inverter.

[0018] In certain aspects, the method includes determining whether a brake time has expired; comparing the current in the inverter to the first current threshold when the brake time has expired; and controlling a switch of the short circuit detection circuit to disable the gate drive when the current in the inverter is greater than or equal to the first current threshold and when the brake time has expired.

[0019] In certain aspects, the method includes determining whether a stop time has expired when the position of the motor has not changed; and controlling a switch of the short circuit detection circuit to disable the gate drive when the stop time has expired.

[0020] 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 and electrically connected to the battery pack interface and the motor, a gate drive connected to the inverter (the gate drive configured to control current in the inverter), a controller configured to control the gate drive, and a short circuit detection circuit. The short circuit detection circuit is configured to monitor current in the inverter, compare the current in the inverter to a first current threshold, compare the current in the inverter to a second current threshold when the current in the inverter is greater than or equal to the first current threshold, wherein the second current threshold has a value based on a timer, increase the timer when the current in the inverter is greater than or equal to the second current threshold, and control a switch of the short circuit detection circuit to disable the gate drive when the timer is greater than or equal to a timer threshold.

[0021] In certain aspects, the short circuit detection circuit is further configured to increase the second current threshold as the timer is increased.

[0022] In certain aspects, the short circuit detection circuit is further configured to compare the current in the inverter to the increased second current threshold when the current in the inverter is greater than or equal to the first current threshold, and increase the timer when the current in the inverter is greater than or equal to the increased second current threshold.

[0023] In certain aspects, the power tool includes a rotational position detector configured to detect a position of the motor. The short circuit detection circuit is further configured to determine whether the position of the motor has changed based on a signal from the rotational position detector when the current in the inverter is greater than or equal to the second current threshold, and increase the timer when the position of the motor has not changed.

[0024] In certain aspects, the short circuit detection circuit is further configured to: determine whether an expected braking time has elapsed when the current in the inverter is less than the first current threshold; compare the current in the inverter to the first current threshold when the expected braking time has elapsed; 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 first current threshold and when the expected braking time has elapsed.

[0025] Before any embodiments are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. Embodiments of the application are capable of implementation in various other ways or being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising" or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless otherwise specified, the use of the terms "mounted," "connected," "supported," and "coupled" and variations thereof is meant to include both direct and indirect mountings, connections, supports, and couplings.

[0026] Unless the context clearly indicates otherwise, the articles "a," "an," and "the" are not limited to mean "one" or "only one." Rather, the articles "a," "an," and "the" are meant to encompass both one and more than one. Also, the terms "plurality" and "a plurality" are meant to encompass both two or more and more than two or more. Similarly, the term "at least one" is meant to encompass both one and more than one. Further, the term "comprising" is meant not to be limiting when used in connection with a listed element or elements with which it is associated. Rather, the term "comprising" encompasses both a recitation that the associated element or elements are present and a recitation that the associated element or elements can be present.

[0027] Further, it should be appreciated that embodiments of the present application can include hardware, software, and electronic components or modules that, for purposes of discussion, can be illustrated and described as if each were a self-contained unit. However, these devices, and components thereof, can be implemented as hardware, software, firmware or any combination thereof. Moreover, they can be implemented in stages or in different ways. For example, the "server," "computing device," "controller," "processor," and like can include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connections (e.g., a system bus) that connect the components. Furthermore, any combination of these or other components, or other known components that can be beneficial for computer implementations, can also be used. For example, the components described above can be implemented using hardware-only (i.e., non-software based) circuitry, using software-only (i.e., non- hardware based) implementations, or using a combination of hardware and software.

[0028] Relative terms, such as "approximately," "about," "substantially," "essentially," and the like, are used herein to describe applicable quantitative or qualitative values, and are understood to encompass values that are within the range of values defined by the term, in one or both directions, up to a contextually defined limit (e.g., an error margin in connection with a measurement, a tolerance in connection with a particular value, etc.). Such terms are also to be taken to disclose a range defined by the absolute values of the two endpoints. For example, a recitation of "from about 2 to about 4" also discloses a range "from 2 to 4." Relative terms can refer to a percentage (e.g., 1%, 5%, 10%, or more) around a value.

[0029] It should be understood that, although certain embodiments are explained in terms of hardware and software in a particular device, these descriptions are for illustrative purposes only. Functions described as being performed by one component can be performed by multiple components in a distributed manner. Likewise, functions performed by multiple components can be consolidated into a single component. In some embodiments, illustrated components can be consolidated or divided into separate software, firmware, and / or hardware. For example, logic and processing can be distributed across multiple electronic processors rather than residing in a single electronic processor and being executed by it. Regardless of how components are combined or divided, hardware and software components can reside on the same computing device or be distributed among different computing devices connected through one or more networks or other suitable transmission links. Likewise, components described as performing particular functionality can perform other functionality not described herein. For example, a device or structure "configured" in a certain way is at least so configured, but can also be configured in ways not explicitly listed.

[0030] Accordingly, in the claims, if an apparatus, method or system is described in terms of comprising or including certain components, means, or steps, such language is used in the sense of specifying the presence of the specified component, means, or step, but not to the exclusion of the presence of others. For example, if a device is described as including a controller, a control unit, an electronic processor, a computing device, a logic element, a module, a storage module, a communication channel or network, or other element configured in a certain way to perform a certain function, then the claim or claims should be interpreted as referring to one or more such elements, where any one of the one or more elements is configured in the manner specified in the claim or claims to perform any one or more of the functions specified.

[0031] Other aspects of the embodiments will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1A A side view of a power tool is shown in accordance with some embodiments.

[0033] Figure 1B A front view of a power tool is shown in accordance with some embodiments.

[0034] Figure 2 A block diagram of a power tool control system according to some embodiments is shown.

[0035] Figure 3 A battery pack for power tools is shown according to some embodiments.

[0036] Figure 4 This is a block diagram of a battery pack control system according to some embodiments.

[0037] Figure 5 A short-circuit detection circuit according to some embodiments is shown.

[0038] Figure 6 Short-circuit thresholds are shown in some embodiments.

[0039] Figure 7 Another short-circuit threshold determined according to some embodiments is shown.

[0040] Figure 8 A block diagram of a short-circuit detection system according to some embodiments is shown.

[0041] Figure 9 It shows Figure 8 Example circuit diagram of an overcurrent comparator circuit in a short-circuit detection system.

[0042] Figure 10 It shows Figure 8 Example circuit diagram of the counter reset circuit in a short-circuit detection system.

[0043] Figure 11 It shows Figure 8 Example circuit diagram of the shutdown circuit in a short-circuit detection system.

[0044] Figure 12 It shows Figure 8 Example circuit diagram of a counter delay overcurrent detection circuit in a short-circuit detection system.

[0045] Figure 13 It shows Figure 8 Example circuit diagram of the gate disable circuit in a short-circuit detection system.

[0046] Figure 14 This is an example circuit diagram of a power tool control system according to some embodiments.

[0047] Figure 15 The process of implementing short-circuit mitigation in power tools according to some embodiments is shown.

[0048] Figure 16 The process of implementing short-circuit mitigation in power tools according to some embodiments is shown. Detailed Implementation

[0049] Figure 1A An electric power tool 100 including a brushless direct current ("BLDC") motor is shown. For example, the electric power tool 100 is a brushless hammer drill including a housing 102. The housing 102 includes a handle portion 104 and a motor housing portion 106. The electric power tool 100 also includes an output driver 108 (illustrated as a chuck), a trigger 110, and a battery pack interface 112. The battery pack interface 112 is configured to make mechanical and electrical connections with an electric power tool battery pack. Although Figure 1A A hammer drill is shown, but in some embodiments, the components described herein can be integrated into other types of electric power tools, including a drill driver, an impact driver, an impact wrench, an angle grinder, a circular saw, a jigsaw, a wire shear, a blower, a vacuum, etc. In a brushless motor electric power tool, such as the electric power tool 100, the switching elements are selectively enabled and disabled by control signals issued by a controller to selectively power the brushless motor from a power source, such as a battery pack.

[0050] Figure 1B An electric power tool 150 including a brushless direct current motor is shown. For example, the electric power tool 150 is a brushless hammer drill including a housing 152. The housing 152 includes a handle portion 154 and a motor housing portion 156. The electric power tool 150 also includes an output driver 158 (illustrated 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 a battery pack 164 and a battery pack 166. Although Figure 1B A hammer drill is shown, but in some embodiments, the components described herein can be used in other types of electric power tools, including a drill driver, an impact driver, an impact wrench, an angle grinder, a circular saw, a jigsaw, a wire shear, a blower, a vacuum, etc.

[0051] Figure 2A control system 200 of the power tools 100, 150 is shown, including a short circuit detection system. The control system 200 includes a controller 202. The controller 202 is electrically and / or communicatively coupled to various modules or components of the power tools 100, 150. For example, the illustrated controller 202 is electrically coupled to a motor 204, a battery pack interface 206, a trigger switch 208 (coupled to a trigger 210), one or more sensors 212 (also referred to as sensing circuitry), 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 can be used to control operation of the power tools 100, 150, monitor operation of the power tools 100, 150, activate one or more indicators 214 (e.g., LEDs), etc. A short circuit detection system or circuit 222 is coupled to the controller 202 and the gate driver 224. In some embodiments, the sensors 212 can measure or detect current in the inverter or FET switch module 220 (e.g., current in one or more phases of the inverter).

[0052] The controller 202 includes a plurality of electrical and electronic elements that provide power, operational control, and protection for the controller 202 and / or elements and modules within the power tools 100, 150. For example, the controller 202 includes, among other things, a processing unit 226 (e.g., a microprocessor, microcontroller, electronic controller, electronic processor, or other 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 various modules or circuits coupled to the controller 202, are connected by one or more control and / or data buses (e.g., a common bus 240). Figure 2 The control and / or data buses are generally shown for illustrative purposes. The use of one or more control and / or data buses to interconnect and communicate between modules, circuits, and components is well known to those skilled in the art, in accordance with the embodiments described herein.

[0053] The memory 228 is a non-transitory computer-readable medium including, for example, a program storage area and a data storage area. The program storage area and the data storage area can include a combination of different types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic storage device. The processing unit 226 is connected to the memory 228 and executes software instructions that can be stored in the RAM of the memory 228 (e.g., during execution), the ROM of the memory 228 (e.g., generally permanently stored), or another non-transitory computer-readable medium, such as another memory or an optical disc. Software included in the implementation 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 applications programs, program data, filters, rules, one or more program modules, and other executable instructions. The controller 202 is configured, among other things, to retrieve and execute instructions related to the control processes and methods described herein from the memory 228. In other configurations, the controller 202 includes additional, fewer, or different components.

[0054] The battery pack interface 206 includes a combination of mechanical components (e.g., rails, grooves, latches, etc.) and electrical components (e.g., one or more terminals) that are configured and operable to connect (e.g., mechanically, electrically, and communicatively) with a battery pack. For example, power provided to the power tool 100, 150 by the battery pack 164, 166, 300 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 elements to regulate or control the power received from the battery pack 164, 166, 300 before providing the power to the controller 202. The battery pack interface 206 also provides power to the FET switch module 220, which is switched by the switching FETs, to selectively provide power to the motor 204. The battery pack interface 206 also includes, for example, the communication lines 242 to provide a communication line or link between the controller 202 and the battery pack 164, 166, 300. In some embodiments, the controller 202 is also electrically and / or communicatively connected to the short circuit detection circuit 222 through a signal line.

[0055] The sensors 212 include one or more current sensors, one or more speed sensors, one or more Hall effect sensors, one or more temperature sensors, etc. The indicators 214 include one or more light emitting diodes ("LEDs"), etc. The indicators 214 can be configured to display a status or related information of the power tool 100, 150. For example, the indicators 214 are configured to indicate a measured electrical characteristic of the power tool 100, 150, a status of the power tool, a status of the short circuit detection circuit 222, etc. The user input module 216 is operably coupled to the controller 202 to, for example, select a forward or reverse mode of operation, a torque and / or speed setting of the power tool 100, 150 (e.g., using a torque and / or speed switch), etc. In some embodiments, the user input module 216 includes a combination of digital and analog input or output devices required to implement the desired level of operation 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.

[0056] The short circuit detection circuit 222 is configured to monitor one or more electrical characteristics of the power tool 100, 150 to detect a condition indicative of a short circuit fault condition. For example, in some embodiments, the short circuit detection circuit 222 monitors one or more electrical characteristics of the plurality of switching FETs of the FET switching module 220 to detect a condition indicative of a short circuit. For example, in some embodiments, the short circuit detection circuit 222 monitors one or more electrical characteristics of the motor 204 to detect a condition indicative of a locked rotor. In some embodiments, when the short circuit detection circuit 222 determines that the one or more electrical characteristics are indicative of a short circuit fault condition, the short circuit detection circuit 222 commands the gate driver 224 to prevent the FET switching module 220 from supplying power to the motor 204. In some embodiments, the short circuit detection circuit 222 determines that the one or more electrical characteristics are indicative of an unwanted current, an uncontrolled current, a destructive current, a dangerous current, etc.

[0057] 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 the power tool 100, 150. In some embodiments, the battery pack 300 has a nominal voltage of 18 volts.

[0058] Figure 4 A control system of the battery pack 300 is shown. The control system includes a controller 400. The controller 400 is electrically and / or communicatively coupled to various modules or components of the battery pack 300. For example, the illustrated controller 400 is coupled to one or more battery cells 402 and an interface 404 (e.g., Figure 3The controller 400 is connected to the interface 304 of the battery pack 300 (e.g., via the interface 304 shown in FIG. 3). 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 can be used to control the operation of the battery pack 300, monitor the status of the battery pack 300, enable or disable charging of the battery pack 300, enable or disable discharging of the battery pack 300, etc.

[0059] The controller 400 includes a number of electrical and electronic components that provide power, operational control, and protection for the components and modules of the controller 400 and / or the battery pack 300. For example, the controller 400 includes a processing unit 412 (e.g., a microprocessor, microcontroller, electronic processor, electronic controller, or other 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 number 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 various modules or circuits connected to the controller 400, are connected by one or more control and / or data buses (e.g., a common bus 426). Figure 4 The control and / or data buses are generally shown for illustrative purposes. The use of one or more control and / or data buses to implement the interconnection and communication between the various modules, circuits, and components according to embodiments of the present disclosure will be apparent to those skilled in the art.

[0060] The memory 414 is a non-transitory computer-readable medium, such as including a program storage area and a data storage area. The program storage area and the data storage area can include a combination of different types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic storage device. The processing unit 412 is connected to the memory 414 and executes software instructions that can be stored in the RAM of the memory 414 (e.g., during execution), the ROM of the memory 414 (e.g., generally permanently), or another non-transitory computer-readable medium, such as another memory or an optical disc. Software included in the implementation 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. Among other things, the controller 400 is configured to retrieve and execute instructions from the memory 414 related to the control processes and methods described herein. In other configurations, the controller 202 includes additional, fewer, or different components.

[0061] The interface 404 includes a combination of mechanical components (e.g., rails, grooves, latches, etc.) and electrical components (e.g., one or more terminals) that are configured to and operable to connect (e.g., mechanically, electrically, and communicatively) 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 with the controller 400 via the communication line 428.

[0062] Figure 5 One embodiment of a short circuit detection circuit 500 is shown. The short circuit detection circuit 500 includes a programmable integrated circuit 505 that is configured to monitor the battery pack 300 for short circuit conditions. The circuit 505 (e.g., the short circuit detection system 222) is powered by a supply voltage (e.g., 3.3V, 5V, etc.). The circuit 505 receives an input voltage signal related to a sensed battery pack current. The circuit 505 also receives one or more Hall effect sensor signals (e.g., A-phase position, B-phase position, C-phase position, etc.). The one or more input Hall effect sensor signals correspond to a position of a rotor of the motor 204. The circuit 505 can use the one or more input Hall sensor signals to determine a current flowing through the motor 204. If the circuit 505 detects a short circuit condition, the circuit 505 provides an output 510 to a switch 515 to disable the motor 204 (e.g., disable a gate driver driving the switch 515). Although only one switch is shown, multiple switches (e.g., switches in an inverter or FET switch module 220) are controlled in a similar manner to disable the motor 204. In this way, the battery pack power 520 is unable to drive the motor 204.

[0063] Circuit 505 can be programmed to include a plurality of different short circuit over current thresholds. In some embodiments, a particular short circuit over current threshold is selected for a particular power tool application (e.g., based on platform voltage). In some embodiments, circuit 505 is configured to dynamically adjust the short circuit over current threshold based on a voltage associated with the power tool (e.g., battery pack voltage or DC bus voltage). The higher the voltage value, the higher the short circuit over current threshold can be set. For example, a larger battery pack that includes a higher voltage and capacity can have a lower internal resistance than other battery packs. For such battery packs that are capable of outputting a larger current, the short circuit over current threshold can be increased. In other embodiments, circuit 505 is configured to dynamically adjust the short circuit over current threshold based on a current value over time.

[0064] Figure 6 A graph of short circuit over current thresholds is shown in accordance with some embodiments. Figure 6 The values shown are merely exemplary values for illustrative purposes only. Different thresholds can be used for different power tool applications. As the voltage associated with the battery pack or DC bus voltage increases, the short circuit over current threshold 605 also increases. In some embodiments, the short circuit over current threshold 605 is based on the voltage of one or more battery packs connected to power tool 100, 150. The short circuit over current threshold 605 can be modified as the one or more battery packs are depleted. In other embodiments, the short circuit over current threshold 605 is based on the DC bus voltage (e.g., multiple battery packs can be connected to power tool 100, 150). The region below the short circuit over current threshold 605 corresponds to the operating range of power tool 100, 150. In some embodiments, the short circuit over current threshold is not only a current value at which to disable the motor, but also a time aspect of the short circuit over current threshold can be implemented. For example, the short circuit over current threshold can need to be exceeded for a period of time before the motor is disabled. By including time as a condition for disabling the motor, different time thresholds can be set. For example, a relatively higher current value can be allowed for a shorter period of time and a relatively lower current value can be allowed for a longer period of time. Configuring the short circuit over current threshold in this manner can provide greater flexibility in extracting as much power as possible from the battery pack.

[0065] Figure 7 A graph of short circuit over current thresholds is shown. Figure 8 The values shown are merely exemplary values for illustrative purposes only. Different thresholds can be used for different power tool applications. Figure 7A stepped short circuit over current threshold 705 is provided that decreases over time. The stepped short circuit over current threshold 705 can be based on a measured current value 710 that keeps temperature variations (e.g., motor temperature, gate driver temperature, FET switch temperature, etc.) below a threshold (e.g., 15°C). The stepped short circuit over current threshold 705 can provide greater current during initial start-up of the power tool 100, 150.

[0066] Figure 8 An example circuit diagram of the programmable integrated circuit 505 (e.g., short circuit detection system 222) is shown. The programmable integrated circuit 505 includes an over current comparator 805, a counter reset circuit 810, a shutdown disable circuit 815, a counter delay over current detection circuit 820, a fault status decision circuit 825, and a gate disable circuit 830.

[0067] Figure 9 An example of the over current comparator 805 is shown. The over current comparator 805 receives a current signal 905 indicative of current through the motor 204 and receives an over current set point 910 as an input. The over current comparator 805 sets the maximum current value that can pass through the FET switch module 220. Although Figure 9 The over current comparator 805 is shown in hardware form, but the same functionality can be implemented in software rather than necessarily requiring this hardware configuration.

[0068] Figure 10 An example of the counter reset circuit 810 is shown. The counter reset circuit 810 receives the current signal 905 and a Hall effect sensor input 1005 as inputs. The counter reset circuit 810 includes a Hall effect state reset circuit 1010 that receives the Hall effect sensor input 1005 and resets all counters during a Hall state transition (e.g., motor phase transition) because the Hall state transition indicates that the motor 204 is rotating and functioning normally. The counter reset circuit 810 includes a minimum current detection comparator 1015 that receives the current signal 905. The minimum current detection comparator 1015 compares the current signal 905 to a minimum current value. The current signal 905 must be continuously above the minimum current value to trigger a fault. A zero state of the current signal 905 (resulting from freewheeling of the FET switch module 220) resets the counters. The counter reset circuit 810 includes an OR gate 1020 that receives outputs of the Hall effect state reset circuit 1010 and the minimum current detection comparator 1015. The counters are reset upon a Hall effect state transition or a "zero state" of the current signal 905. Although Figure 10 The counter reset circuit 810 is shown in hardware form, but the same functionality can be implemented in software rather than necessarily requiring this hardware configuration.

[0069] Figure 11 An example of a stall shutdown circuit 815 is shown. The stall shutdown circuit 815 receives the output from the minimum current detection comparator 1015. When the motor 204 is fully stalled, if the stall shutdown circuit 815 detects that current is still present (based on the output of the minimum current detection comparator 1015), a fault is flagged.

[0070] The stall shutdown circuit 815 includes a hardware stall timer 1105 that has a first output (e.g., a high output) when the time since the last signal from the edge hall sensor is greater than or equal to the stall counter, and the time since the last signal from the edge hall effect sensor is less than the stall timer check window. The hardware stall timer 1105 has a second output (e.g., a low output) when the time since the last signal from the edge hall effect sensor is less than the stall counter, and the time since the last signal from the edge hall effect sensor is greater than the stall timer check window.

[0071] During a pull-up trigger, the stall shutdown circuit 815 is reset each time a hall effect edge is sensed, indicating rotation of the motor 204. If the motor 204 does not rotate after the pull-up trigger, and motor current is detected after the stall counter has met the requirements, a fault is detected and flagged. Although Figure 11 The stall shutdown circuit 815 is shown in hardware, but the same functionality can be implemented in software, rather than necessarily requiring this hardware configuration.

[0072] Figure 12 An example of a counter delayed overcurrent detection circuit 820 is shown. The counter delayed overcurrent detection circuit 820 includes, for example, a plurality of comparators 1205 that receive the current signal 905 and associated overcurrent setpoint values. Although Figure 12 The counter delayed overcurrent detection circuit 820 is shown in hardware, but the same functionality can be implemented in software, rather than necessarily requiring this hardware configuration. The overcurrent setpoint values and their timing margins are determined by the transient thermal impedance of the inverter contained in the FET switching module 220 and the power generated by the fault event current pulse. The timing constraints are set by the predetermined allowable temperature rise in the inverter FETs during a fault event.

[0073] The counter delay overcurrent detection circuit 820 also includes a plurality of AND gates 1210. The plurality of AND gates 1210 AND the output of the respective comparator 1205 with the NOT of the counter reset condition from the counter reset circuit 810. If the output of the counter reset circuit 810 is 0, then the output of the AND gate 1210 will be 1. However, a zero state of the Hall XOR output edge and current signal 905 will result in a 0 input to the AND gate 1210, thereby resetting the plurality of counters 1215. The counters are also reset when the current signal 905 is below the overcurrent setpoint value. The counter values from the plurality of counters 1215 are provided to an OR gate 1220.

[0074] The fault condition determination circuit 825 receives the outputs from the overcurrent comparator 805, the shutdown circuit 815, and the counter delay overcurrent detection circuit 820 and determines whether a fault condition has occurred based on the outputs. In some embodiments, the fault condition determination circuit 825 is an OR gate.

[0075] Figure 13 One example of a gate disable circuit 830 is shown. The gate disable circuit 830 enables or disables the gate driver 224 based on the fault condition. In some embodiments, the gate driver 224 will be enabled when all of the following conditions are met: there is a trigger signal (e.g., the trigger 210 is actuated), no fault is detected, and the controller 202 is providing a gate enable signal. If any of the conditions are not met, then the gate driver 224 is disabled. The gate enable is controlled by a drain open circuit output of a MOSFET 1305. Although Figure 13 The gate disable circuit 830 is shown in hardware aspects, but the same functionality can be implemented in software instead of necessarily requiring this hardware configuration.

[0076] Figure 14 A circuit diagram of the control system 1400 of the power tool 100, 150 is shown. As Figure 14 The controller 202 is connected to the gate driver 224 and the short circuit detection system 222. The controller 202 sends a gate signal to the gate driver 224 to control the gate driver 224. If the controller 202 does not independently detect any faults, then a fault clear signal is sent to the short circuit detection system 222. In Figure 14 In the example, the short circuit detection system 222 detects actuation of the trigger switch 10 and controls the gate driver 224 (e.g., enables, disables, etc.) based on the actuation of the trigger switch 10.

[0077] The short-circuit detection system 222 receives a signal S6, i.e. a supply current detection signal, from the current detector 24. The short-circuit detection system 222 also receives a signal S7, i.e. a rotational position signal (e.g. a Hall effect sensor providing a rotor position signal), from the rotational position detector 23. The gate driver 224 transmits drive control signals S8-S13 to the FET switch module 220. The rotational position signal S7 can be used to calculate a rotational speed (e.g. a rotational velocity) and / or a rotational acceleration. Likewise, the supply current detection signal S6 can be used to calculate a related supply current rate of change. The motor 204 in this embodiment is a three-phase brushless motor. The battery supply provided by the battery pack 300 is converted into a three-phase supply by the FET switch module 220 and supplied to the motor 204.

[0078] The motor 204 comprises three windings 31, 32 and 33. In this embodiment, the three windings 31, 32 and 33 are connected in a delta configuration. However, in other embodiments, the windings can be connected in other configurations. Furthermore, the motor 204 comprises three terminals 20a, 20b and 20c as supply input terminals.

[0079] The rotational position detector 23 is configured to output a signal corresponding to a rotational position of the motor 204, or in particular a rotational position signal corresponding to a rotational position of a rotor of the motor 204. For example, the rotational position detector 23 comprises three Hall effect sensors. The Hall effect sensors are arranged at intervals of, for example, 120 degrees around the rotor of the motor 204. The signals output by the three Hall effect sensors are input to the short-circuit detection system 222. The short-circuit detection system 222 detects the rotational position and rotational speed of the motor 20 from the signals input by the rotational position detector 23, i.e. from the signals output by the three Hall effect sensors. A rotational acceleration can also be calculated from these signals.

[0080] Figure 15A flow 1500 for controlling the power tool 100, 150 is shown. While the flow 1500 is described as being performed by the short circuit detection system 222, in some cases the flow 1500 is performed jointly by the short circuit detection system 222 and the controller 202. At step 1505, the short circuit detection system 222 detects actuation of the trigger 210. At step 1510, the short circuit detection system 222 determines whether the trigger 210 is released. When the trigger 210 is released (YES at step 1510), the short circuit detection system 222 determines whether the expected brake time has elapsed (step 1515). When the expected brake time has not elapsed (NO at step 1515), the flow 1500 returns to step 1510. When the expected brake time has elapsed (YES at step 1515), the short circuit detection system 222 determines whether the current is greater than or equal to a first current threshold (e.g., a minimum current threshold) (step 1520). The short circuit detection system 222 monitors the current through the inverter or FET switch module 220 and the motor 204. 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. When the current is not greater than or equal to the first current threshold (NO at step 1520), the flow 1500 returns to step 1505. When the current is greater than or equal to the first threshold, the short circuit detection system 222 will disable the power tool 100, 150 (step 1540). In this case, a fault has occurred because current is still present after the motor 204 has been braked.

[0081] Returning to step 1510, while the trigger 210 is not released (NO at step 1510), the short detection system 222 monitors the current (step 1523) and determines whether the current is greater than or equal to a first threshold (e.g., a minimum current threshold) (step 1525). While the current is not greater than or equal to the first threshold (NO at step 1525), the flow 1500 returns to step 1505. While the current is greater than or equal to the first threshold (YES at step 1525), the short detection system 222 determines whether the Hall effect state has changed (step 1530). While the Hall effect state has changed (YES at step 1530), the short detection system 222 returns to step 1505. While the Hall effect state has not changed (NO at step 1530), the short detection system 222 determines whether the shutdown time has elapsed (step 1535). While the shutdown time has not elapsed (NO at step 1535), the short detection system 222 returns to step 1530. While the shutdown time has elapsed (YES at step 1535), the short detection system 222 disables the power tool 100, 150 (step 1540) and detects a fault condition. The short detection system 222 disables the power tool 100, 150 by controlling the gate drivers of the switches, thereby preventing current from passing through the motor 204, thereby disabling the power tool 100, 150.

[0082] Figure 16 A flow 1600 for controlling the power tool 100, 150 is shown. While the flow 1600 is described as being performed by the short detection system 222, in some cases, the flow 1600 is performed by the short detection system 222 and the controller 202 in conjunction. The flow 1600 can be performed in combination with and / or in parallel with the flow 1500, such that the two flows are combined and / or performed in parallel. In step 1605, the short detection system 222 monitors the current. The current monitoring of step 1605 can be the same current monitoring as step 1523. In some embodiments, the short detection system 222 monitors the current through the inverter or FET switch module 220 and the motor 204. In some embodiments, the current is monitored by one or more current sensors, such as shunt resistors, that detect the current through the motor 204.

[0083] At step 1610, the short circuit detection system 222 determines whether the current is greater than or equal to a first current threshold (e.g., a minimum current threshold). When the current is less than the first current threshold (NO at step 1610), the short circuit detection system 222 returns to step 1515 of flowchart 1500. When the current is greater than or equal to the first current threshold (YES at step 1610), the short circuit detection system 222 proceeds to step 1615. At step 1615, the short circuit detection system 222 determines whether the current is greater than an increasing threshold (e.g., an Nth threshold of a plurality of thresholds). In particular, as the timer increases, the current threshold also increases. When the current is less than the increasing threshold (NO at step 1615), the short circuit detection system 222 returns to step 1610. When the current is greater than or equal to the increasing threshold (YES at step 1615), the short circuit detection system 222 starts a timer or counter (step 1620). The purpose of the timer or counter is to determine whether a short circuit condition, if present, persists for a period of time (e.g., and is not merely a transient current spike). In some embodiments, the short circuit detection system 222 includes an internal clock (e.g., a real-time clock) for recording time, and thus a separate dedicated timer or counter is not needed. However, for ease of explanation, the timer is generally described as a method of tracking elapsed time. With the counter set, the short circuit detection system 222 proceeds to step 1625. At step 1625, the short circuit detection system 222 determines whether the Hall effect state has changed. When the Hall effect state has changed (YES at step 1625), the short circuit detection system 222 returns to step 1610. When the Hall effect state has not changed (NO at step 1625), the short circuit detection system 222 determines whether the timer or counter is greater than or equal to a timer threshold (step 1630). When the timer is less than the timer threshold (NO at step 1630), the short circuit detection system 222 returns to step 1610. When the timer is greater than or equal to the timer threshold (YES at step 1630), the short circuit detection system 222 proceeds to step 1635, which disables the power tool 100, 150 and detects a fault condition. The switches (e.g., the switches in the FET switch module 220) are disabled by controlling the gate drivers of the switches, thereby preventing current from passing through the motor 204 and thereby disabling the power tool 100, 150.

[0084] At step 1640, the short circuit detection system 222 determines whether the current is greater than or equal to a second current threshold (e.g., a maximum current threshold). When the current is less than the second current threshold (NO at step 1640), the short circuit detection system 222 returns to step 1605 and continues to monitor the current. When the current is greater than or equal to the second current threshold (YES at step 1640), the short circuit detection system 222 proceeds to step 1635 and disables the power tool 100, 150. In this way, the current is continuously monitored during steps 1625, 1630, and 1635.

[0085] In some embodiments, if the measured current falls below the first threshold before the timer reaches the timer threshold, the timer is stopped or reset, and the power tool 100, 150 continues to operate normally while monitoring the current (at step 1605).

[0086] Thus, the embodiments described herein provide a short circuit detection system that is independent of the main controller. The short circuit detection system can monitor the characteristics of the MOSFET and monitor the stall condition of the motor.

[0087] Representative Features

[0088] The following clauses recite representative features, which can exist alone or in any combination with one or more features disclosed in the text and / or drawings of this specification.

[0089] Clause 1. A power tool, comprising: a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack comprising a plurality of battery cells; an inverter disposed 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 rotational position detector configured to detect a position of the motor; a controller configured to control the gate driver; and a short circuit detection circuit configured to: monitor the current in the inverter, compare the current in the inverter to a first current threshold, determine whether the position of the motor changes based on a signal from the rotational position detector when the current in the inverter is greater than or equal to the first current threshold, and control a switch of the short circuit detection circuit to disable the gate driver when the position of the motor does not change.

[0090] Clause 2: The power tool of clause 1, further comprising: an indicator to indicate a status of the short circuit detection circuit.

[0091] Clause 3: The power tool of any preceding clause, wherein the rotational position detector comprises a plurality of Hall effect sensors, each Hall effect sensor configured to provide a Hall effect sensor signal corresponding to the motor rotor position.

[0092] Clause 4: The power tool of any preceding clause, wherein the short circuit detection circuit is further configured to select a first current threshold value based on a voltage provided to the battery pack interface by the battery pack.

[0093] Clause 5: The power tool of any preceding clause, wherein the short circuit detection circuit is further configured to adjust the first current threshold value based on a change in current in the inverter.

[0094] Clause 6: The power tool of any preceding clause, wherein the short circuit detection circuit is further configured to: determine whether an expected braking time has elapsed; compare the current in the inverter to the first current threshold value when the expected braking time has elapsed; 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 first current threshold value and the expected braking time has elapsed.

[0095] Clause 7: The power tool of any preceding clause, wherein the short circuit detection circuit is further configured to: determine whether a stall time has elapsed when a position of the motor has not changed; and control a switch of the short circuit detection circuit to disable the gate driver when the stall time has elapsed.

[0096] Clause 8: The power tool of any preceding clause, further comprising a trigger configured to be actuated, wherein the short circuit detection circuit is further configured to: detect actuation of the trigger; drive the motor when the trigger is actuated; and compare the current in the inverter to the first current threshold value when the trigger is released while driving the motor.

[0097] Clause 9: The power tool of clause 8, wherein the short circuit detection circuit is further configured to enable the gate driver when the trigger is actuated and the current in the inverter is less than the first current threshold value.

[0098] Clause 10: A method of controlling a power tool, the method comprising monitoring, with a short circuit detection circuit, current in an inverter, the inverter being located between and electrically connected to a battery pack interface and a motor; comparing, with the short circuit detection circuit, the current in the inverter to a first current threshold; determining, with the short circuit detection circuit, whether a position of the motor changes in response to a signal from a rotary position detector, and controlling, with the short circuit detection circuit, a switch of the short circuit detection circuit to disable a gate driver when the position of the motor does not change, wherein the gate driver is configured to control the current in the inverter.

[0099] Clause 11 : The method of clause 10, further comprising providing, with an indicator, an indication of a status of the short circuit detection circuit.

[0100] Clause 12: The method of any of clauses 10-11, further comprising receiving a battery pack through the battery pack interface and selecting the first current threshold in response to a voltage provided to the battery pack interface by the battery pack.

[0101] Clause 13: The method of any of clauses 10-12, further comprising adjusting the first current threshold in response to a change in the current in the inverter.

[0102] Clause 14: The method of any of clauses 10-13, further comprising determining whether an expected braking time has elapsed; comparing the current in the inverter to the first current threshold when the expected braking time has elapsed; and controlling the 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 first current threshold and the expected braking time has elapsed.

[0103] Clause 15: The method of any of clauses 10-14, further comprising determining whether a shutdown time has elapsed when the position of the motor does not change; and controlling the switch of the short circuit detection circuit to disable the gate driver when the shutdown time has elapsed.

[0104] Clause 16: A power tool, comprising: a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack comprising a plurality of battery cells; an inverter disposed 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; and a short circuit detection circuit configured to monitor current in the inverter, compare the current in the inverter to a first current threshold, when the current in the inverter is greater than or equal to the first current threshold, compare the current in the inverter to a second current threshold, wherein a value of the second current threshold is based on a timer, when the current in the inverter is greater than or equal to the second current threshold, increase the timer, and when the timer is greater than or equal to a timer threshold, control a switch of the short circuit detection circuit to disable the gate driver.

[0105] Clause 17: The power tool of clause 16, wherein the short circuit detection circuit is further configured to: increase the second current threshold as the timer increases.

[0106] Clause 18: The power tool of clause 17, wherein the short circuit detection circuit is further configured to: when the current in the inverter is greater than or equal to the first current threshold, compare the current in the inverter to the increased second current threshold; and when the current in the inverter is greater than or equal to the increased second current threshold, increase the timer.

[0107] Clause 19: The power tool of any of clauses 16-18, further comprising: a rotational position detector configured to detect a position of the motor, wherein the short circuit detection circuit is further configured to: when the current in the inverter is greater than or equal to the second current threshold, determine whether the position of the motor has changed based on a signal from the rotational position detector, and increase the timer when the position of the motor has not changed.

[0108] Clause 20: The power tool of any of clauses 16-19, wherein the short circuit detection circuit is further configured to: when the current in the inverter is less than the first current threshold, determine whether an expected braking time has elapsed; when the expected braking time has elapsed, compare the current in the inverter to the first current threshold; and when the current in the inverter is greater than or equal to the first current threshold and the expected braking time has elapsed, control the switch of the short circuit detection circuit to disable the gate driver.

[0109] Thus, the embodiments of the present application provide a short circuit mitigation function for a power tool. Various features and advantages are described in the following claims.

Claims

1. A power tool characterized by comprising: Comprising a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack comprising a plurality of battery cells; an inverter disposed between and in electrical connection with 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 rotary position detector configured to detect a position of the motor, wherein the rotary position detector comprises a plurality of Hall effect sensors, each Hall effect sensor configured to provide a Hall effect sensor signal corresponding to the motor rotor position; a controller configured to control the gate driver; and a short circuit detection circuit comprising: a programmable integrated circuit configured to monitor for a short circuit condition of the power tool, the programmable integrated circuit configured to use one or more input Hall effect sensor signals to determine a current flowing through the motor, wherein the programmable integrated circuit is configured to control a switch of the short circuit detection circuit to disable the gate driver when the programmable integrated circuit detects the short circuit condition. a status indicator configured to indicate a status of the short circuit detection circuit.

2. The power tool of claim 1, wherein, The short circuit detection circuit is configured to monitor one or more electrical characteristics of the power tool to detect a condition indicative of a short circuit condition.

3. The power tool of claim 1, wherein, The short circuit detection circuit is configured to monitor the short circuit condition based on the current in the inverter, a first current threshold, and the motor rotor position.

4. The power tool of claim 3, wherein, The short circuit detection circuit is further configured to select the first current threshold based on a voltage provided by the battery pack to the battery pack interface.

5. The power tool of claim 4, wherein, The short circuit detection circuit is further configured to adjust the first current threshold based on a change in the current in the inverter.

6. The power tool of claim 4, wherein, Comprising 7. A power tool characterized by comprising: a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack comprising a plurality of battery cells; an inverter disposed between and in electrical connection with 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; and a short circuit detection circuit configured to monitor for a short circuit condition of the power tool, wherein the short circuit detection circuit is configured to control a switch of the short circuit detection circuit to disable the gate driver when a possible short circuit condition determined by a timer persists for a period of time. The short circuit detection circuit is configured to monitor one or more electrical characteristics of the power tool to detect a condition indicative of a short circuit condition.

8. The power tool of claim 7, wherein, The short circuit detection circuit is configured to monitor the short circuit condition based on the current in the inverter, a first current threshold, a second current threshold, and a timer threshold.

9. The power tool of claim 8, wherein, The short circuit detection circuit is further configured to increase the second current threshold as the timer increases.

10. The power tool of claim 9, wherein, ​

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