Short circuit protection for brushless dc motors

Abstract

The invention relates to switch element protection for brushless DC motors used, for example, with power tools. The invention separately checks each switch element of a power stage for a short when the tool's trigger is actuated. Each switch element is turned on for a period of time (e.g., 1-5 microseconds), the current through the half-bridge or full power stage is measured, and the switch element is turned off. When the current is greater than or equal to a threshold (e.g., 5A), the controller stops and indicates a fault condition. By sequentially testing each switch element, the controller is able to determine whether the shorted switch element is the opposite one in the half-bridge being tested.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 164,696, filed March 23, 2021, and U.S. Patent Application No. 17 / 694,249, filed March 14, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates generally to brushless direct current (BLDC) motors, and more specifically to short-circuit protection for BLDC motors. Background Technology

[0004] Electric hand tools (such as electric ratchet wrenches, impact wrenches, and other screwdrivers) are commonly used in automotive, industrial, and household applications to install and remove threaded fasteners and to apply torque and / or angular displacement to workpieces (such as threaded fasteners). Electric hand tools typically include an output component (such as a drive lug or chuck), a user-actuable trigger switch, a motor housed in a housing, a motor controller, and other components (such as switches, light-emitting diodes (LEDs), and batteries).

[0005] Power tools with brushless motors typically implement a triple half-bridge power stage consisting of six switching elements. However, there is a risk that one of the two switching elements in each half-bridge may fail due to a short circuit. If a short circuit occurs and is not detected, the entire half-bridge will short-circuit, causing the battery to short-circuit when the other switching element in the half-bridge is turned on. This can lead to damage to the motor controller, battery, and end user. Summary of the Invention

[0006] This invention broadly relates to short-circuit protection for switching elements (e.g., MOSFETs) in BLDC motors (e.g., in power tools). The tool includes a tool housing, an output assembly (e.g., a ratchet head assembly) adapted to provide torque to a workpiece, a trigger, a motor housed within the housing, an indicator, a controller, and a power supply. The controller may implement and include a triple half-bridge power stage comprising six (or any multiple of six) switching elements (e.g., MOSFETs).

[0007] When the trigger is actuated, the controller performs a bootstrap capacitor charging process before commutating the motor. The controller charges the bootstrap capacitor by individually, all at once, all at once with a specific duty cycle (e.g., 50%), or individually with a specific duty cycle. During this operation, there is a possibility that one of the high-side switching elements may short-circuit. Therefore, the controller turns on the low-side switching element for a short period (e.g., 10-100 microseconds) and measures the current flowing through the half-bridge or full-power stage. When the current is greater than or equal to a first threshold (e.g., 10A), one of the high-side switching elements short-circuits, and the controller stops or aborts the bootstrap capacitor charging process and can indicate a fault condition. When the current is less than the first threshold, the controller continues the bootstrap capacitor charging process by keeping the low-side switching element on.

[0008] Following the short-circuit check of the switching elements during the bootstrap capacitor charging process, the controller individually checks each switching element for short circuits. This is performed by turning each switching element on for a period of time (e.g., 1-5 microseconds), measuring the current flowing through the half-bridge or full-power stage, and then disconnecting the switching element. When the current is greater than or equal to a second threshold (e.g., 5A), the controller stops or aborts and indicates a fault condition. When the current is less than the second threshold, the controller continues the process and checks each of the switching elements. If no fault is detected, the controller continues normal operation of the BLDC motor.

[0009] By testing each switching element individually, the controller can determine whether a short-circuited switching element is the opposite of the half-bridge under test. For example, if the high-side switching element is on and the current is greater than or equal to a second threshold (e.g., 5A), then the low-side switching element in that half-bridge is short-circuited. This two-step switching element short-circuit detection can be performed every time the controller is powered on (as an initial diagnostic check) and every time a trigger is actuated, ensuring that short circuits are not introduced or reintroduced into the controller circuitry. This reduces the risk of damage to the controller, power supply, and other components of the tool due to short-circuit events. Attached Figure Description

[0010] To facilitate understanding of the subject matter sought, embodiments thereof are illustrated in the accompanying drawings. When considered in conjunction with the following description, the subject matter sought, its construction and operation, and its many advantages should be readily understood and appreciated from an examination of its embodiments.

[0011] Figure 1 This is a perspective view of an exemplary tool incorporated in an embodiment of the present invention.

[0012] Figure 2 and Figure 3 This is a component block diagram of an electronic component incorporating an exemplary tool according to an embodiment of the present invention.

[0013] Figure 4 This is an exemplary switch diagram of an exemplary tool with a brushless DC motor, incorporating embodiments of the present invention.

[0014] Figure 5 This is a block diagram of a short-circuit protection method incorporating exemplary tools from embodiments of the present invention.

[0015] Figures 6 to 8 This is a block diagram of another method for short-circuit protection incorporating exemplary tools from embodiments of the present invention. Detailed Implementation

[0016] While the invention is permissible in many different forms, preferred embodiments of the invention are shown in the accompanying drawings and will be described in detail herein. It should be understood that the invention should be considered as an example of the principles of the invention and is not intended to limit the broad aspects of the invention to the illustrated embodiments. As used herein, the term "invention" is not intended to limit the scope of the claimed invention, but is a term used only for purposes of explanation to discuss exemplary embodiments of the invention.

[0017] This invention broadly relates to short-circuit protection of switching elements (e.g., MOSFETs) in BLDC converters used, for example, in power tools. The tool includes a tool housing, an output assembly (e.g., a ratchet head assembly) adapted to provide torque to a workpiece, a trigger, a motor housed within the housing, an indicator, a controller, and a power supply. The controller may implement and include a triple half-bridge power stage comprising six (or any multiple of six) switching elements (e.g., MOSFETs).

[0018] When the trigger is actuated, the controller performs a bootstrap capacitor charging process before commutating the motor. The controller charges the bootstrap capacitor by individually, all at once, all at once with a specific duty cycle (e.g., 50%), or individually with a specific duty cycle. During this operation, there is a possibility that one of the high-side switching elements is short-circuited. Therefore, the controller turns on the low-side switching element for a short period (e.g., 10-100 microseconds) and measures the current flowing through the half-bridge or full-power stage. When the current is greater than or equal to a first threshold (e.g., 10A), one of the high-side switching elements is short-circuited, and the controller stops or aborts the bootstrap capacitor charging process and indicates a fault condition. When the current is less than the first threshold, the controller continues the bootstrap capacitor charging process by keeping the low-side switching element on.

[0019] Following the short-circuit check of the switching elements during the bootstrap capacitor charging process, the controller individually checks each switching element for short circuits. This is performed by turning each switching element on for a period of time (e.g., 1-5 microseconds), measuring the current flowing through the half-bridge or full-power stage, and then disconnecting the switching element. When the current is greater than or equal to a second threshold (e.g., 5A), the controller stops or aborts and indicates a fault condition. When the current is less than the second threshold, the controller continues the process and checks each of the switching elements. If no fault is detected, the controller continues normal operation of the BLDC motor.

[0020] By testing each switching element individually, the controller can determine whether a short-circuited switching element is the opposite of the half-bridge under test. For example, if the high-side switching element is on and the current is greater than or equal to a second threshold (e.g., 5A), then the low-side switching element in that half-bridge is short-circuited. This two-step switching element short-circuit detection can be performed every time the controller is powered on (as an initial diagnostic check) and every time a trigger is actuated, ensuring that short circuits are not introduced or reintroduced into the controller circuitry. This reduces the risk of damage to the controller, power supply, and other components of the tool due to short-circuit events.

[0021] refer to Figures 1 to 3 An exemplary tool 100 (e.g., a cordless ratchet tool) that can be used with the present invention includes a main tool housing 102 and an output assembly 104 (e.g., a ratchet head assembly). The tool housing 102 may include a first housing portion and a second housing portion connected together in a flip-top manner and securely coupled to the output assembly 104. For example, the tool housing 102 may enclose or house a motor 114 ( Figure 2 and Figure 3 (shown in the image), controller 116 ( Figure 2 and Figure 3 (shown in the image), switch assembly 118 ( Figure 2 and Figure 3 The tool housing 102 may include a display with buttons for configuring and setting the tool, one or more indicators 122 (e.g., light-emitting diodes), and other components for operating the tool. The tool housing 102 may also include a textured or knurled handle to improve the user's grip on the tool 100 during use.

[0022] Output assembly 104 includes a drive unit 106, which includes, for example, a drive protrusion 108. The drive protrusion 108 is adapted to apply torque to a workpiece (e.g., a fastener) via an adapter, drill bit, or sleeve coupled to the drive protrusion 108 (e.g., a two-way ratchet square or hexagonal actuator). As illustrated, the drive protrusion 108 is a "male" connector designed to mate with or mat with a female pair. However, the drive unit 106 may alternatively include a "female" connector designed to mat with a male pair. The drive unit 106 may also be structured to directly engage a workpiece without requiring coupling to an adapter, drill bit, or sleeve. The rotation direction of the drive unit 106 / drive protrusion 108 can be selected as a first rotation direction or a second rotation direction (e.g., clockwise or counterclockwise) by rotating a selector switch.

[0023] Tool 100 also includes a trigger 110, which can be actuated by a user to selectively operate tool 100. For example, a user can press the trigger 110 inward to selectively draw power from power source 120, causing motor 114 to supply torque to output assembly 104 and causing drive protrusion 108 to rotate in a desired direction of rotation. Trigger 110 can also be operatively coupled to a switching mechanism 118 adapted to supply power from power source 120 to motor 114 when trigger 110 is actuated. Any suitable trigger 110 or switch can be implemented without departing from the spirit and scope of the invention. For example, trigger 110 can also be biased such that trigger 110 can be pressed inward relative to tool 100 to operate tool 100, and released to move trigger 110 outward relative to tool 100 to stop operation of tool 100 via the biasing nature of trigger 110. Trigger 110 and switching mechanism 118 can also be variable speed mechanisms. In this respect, the further the trigger 110 is pressed down, the faster the motor operates due to the actuation or pressing of the trigger 110.

[0024] Motor 114 may be disposed within tool housing 102 and adapted to operatively engage output assembly 104 and provide torque to tool 100, which in turn provides torque to drive portion 106 / drive protrusion 108. Motor 114 may be a brushless or brushed motor, or any other suitable motor. In one example, motor 114 is a brushless DC motor. Power supply 120 may be associated with tool 100 to provide electronic or other forms of power (e.g., electric, hydraulic, or pneumatic) to tool 100 to operate the motor. In one embodiment, power supply 120 may be housed in the end 112 of tool housing 102 opposite output assembly 104, in the middle portion of tool 100, or in any other portion of tool 100 / tool ​​housing 102. Power supply 120 may also be an external component not housed in tool 100, but operatively coupled to tool 100 via, for example, wired or wireless means. In one embodiment, the power source 120 is a removable and rechargeable battery adapted to be disposed in the end of the tool housing 102 and electrically connected to a corresponding terminal of the tool 100.

[0025] The controller 116 may be operatively coupled to one or more of the power supply 120, switching mechanism 118, indicator 122, and motor 114. The controller 116 may include a central processing unit (CPU) for processing data and computer-readable instructions, and a memory 406 for storing data and instructions. The memory may include volatile random access memory (RAM), non-volatile read-only memory (ROM), and / or other types of memory. It may also include data storage components for storing data and controller / processor-executable instructions (e.g., instructions for the operation and function of tool 100). The data storage components may include one or more types of non-volatile solid-state memory, such as flash memory, read-only memory (ROM), magnetoresistive RAM (MRAM), ferroelectric RAM (FRAM), phase-change memory, etc.

[0026] Computer instructions for operating tool 100 and its various components can be executed by controller 116, which uses memory as a temporary "working" storage during operation. The computer instructions can be stored in a non-transient manner in non-volatile memory, storage, or external devices. Alternatively, in addition to or instead of software, some executable instructions can be embedded in hardware or firmware.

[0027] The controller 116 implements and includes a power stage (e.g., a triple half-bridge power stage) that includes six (or any multiple of six) switching elements. Figure 4A schematic diagram of an example switch is illustrated. In this example, a power stage with a switch array 124 includes high-side switching elements H1, H2, and H3, and low-side switching elements L1, L2, and L3, each having an actuated state (e.g., ON) and a non-actuated state (e.g., OFF). In one embodiment, the switching elements are field-effect transistors (FETs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). The switch array 124 is controlled by a controller 116 to selectively apply power from a power source 120 (e.g., a battery) to the motor 114 to achieve a desired commutation scheme. In other words, the switching elements are actuated in a specific sequence between the actuated and non-actuated states, determined by the motor design, to rotate the motor. The speed of motor rotation can be controlled by open-loop or closed-loop control of the pulse-width modulation (PWM) duty cycle of the switching elements.

[0028] The controller 116 also monitors, analyzes, and processes electrical signals from sensors, such as one or more current sensors, one or more speed sensors, one or more Hall effect sensors, one or more temperature sensors, etc. For example, the speed of the motor 114 can be determined or calculated by the controller in a known manner using a Hall effect sensor that senses the rotational position of the rotor.

[0029] Tool 100 and / or controller 116 may also include one or more bootstrap capacitors, and controller 116 may perform a bootstrap capacitor charging process before commutating motor 114 when trigger 110 is actuated. Controller 116 may also implement the methods described herein.

[0030] For example, when trigger 110 is actuated, controller 116 performs a short-circuit check on the switching elements during the bootstrap capacitor charging process before commutating motor 114. (Reference) Figure 5 A method 200 for performing a short-circuit check on switching elements during the charging process of a bootstrap capacitor is described. The method begins when trigger 110 is actuated, as illustrated in block 202. Once the trigger is actuated, the tool (e.g., via controller 116) charges the bootstrap capacitor by individually, all at once, all at once with a specific duty cycle (e.g., 50%), or individually with a specific duty cycle, turning on the low-side switching elements (L1, L2, and L3), as illustrated in block 204. During this operation, there is a possibility that one of the high-side switching elements (H1, H2, and H3) is short-circuited. Therefore, controller 116 turns on the low-side switching elements (L1, L2, and L3) for a short period (e.g., 10-100 microseconds) and measures the current flowing through the half-bridge or full-power stage, as illustrated in block 206.

[0031] The controller 116 then determines whether the measured current is greater than or equal to a first threshold (e.g., 10A), as illustrated in block 208. When the measured current is less than the first threshold, the controller 116 continues the bootstrap capacitor charging process by keeping the low-side switching elements (L1, L2, and L3) on, as illustrated in block 210. However, when the measured current is greater than or equal to the first threshold, one of the high-side switching elements (H1, H2, and H3) is short-circuited, and the controller 116 de-energizes the power supply to itself and terminates the bootstrap capacitor charging process, as illustrated in block 212, and indicates the fault condition, for example, by activating indicator 122, as illustrated in block 214. The controller 116 can also deactivate indicator 122 after a predetermined period of time to save power.

[0032] refer to Figures 6 to 8 Another method 300 for performing a short-circuit check on a switching element is described. Method 300 may be performed before, after, or substantially simultaneously with method 200. In one example, method 300 is performed after method 200. The controller 116 is energized and / or the trigger 110 is actuated, as illustrated in block 302. The controller 116 activates or turns on a first switching element (e.g., H1) for a period of time (e.g., 1-5 microseconds), as illustrated in block 304. The controller 116 measures the current flowing through the half-bridge or full-power stage of the first switching element, as illustrated in block 306, and deactivates or deactivates the first switching element (e.g., H1), as illustrated in block 308. The controller 116 determines whether the measured current is greater than or equal to a second threshold (e.g., 5A), as illustrated in block 310. When the measured current is greater than or equal to a second threshold, controller 116 deactivates power to itself, as illustrated in block 312, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 314. However, when the measured current is less than the second threshold, controller 116 continues the process and checks the next switching element. Even if a short circuit is detected, controller 116 can continue the process and check the next switching element. Controller 116 can also deactivate indicator 122 after a predetermined time period to conserve power.

[0033] Controller 116 activates or activates a second switching element (e.g., L1) for a period of time (e.g., 1-5 microseconds), as illustrated in block 316. Controller 116 measures the current flowing through the half-bridge or full-power stage of the second switching element, as illustrated in block 318, and deactivates or deactivates the second switching element (e.g., L1), as illustrated in block 320. Controller 116 determines whether the measured current is greater than or equal to a second threshold, as illustrated in block 322. When the measured current is greater than or equal to the second threshold, controller 116 deactivates power to controller 116, as illustrated in block 312, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 314. When the measured current is less than the second threshold, controller 116 continues the process and checks the next switching element. Controller 116 can continue the process and check the next switching element even if a short circuit is detected. Controller 116 can also deactivate indicator 122 after a predetermined period of time to save power.

[0034] Controller 116 activates or activates a third switching element (e.g., H2) for a period of time (e.g., 1-5 microseconds), as illustrated in block 324. Controller 116 measures the current flowing through the half-bridge or full-power stage of the third switching element, as illustrated in block 326, and deactivates or deactivates the third switching element (e.g., H2), as illustrated in block 328. Controller 116 determines whether the measured current is greater than or equal to a second threshold, as illustrated in block 330. When the measured current is greater than or equal to the second threshold, controller 116 deactivates power to controller 116, as illustrated in block 332, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 334. When the measured current is less than the second threshold, controller 116 continues the process and checks the next switching element. Controller 116 can continue the process and check the next switching element even if a short circuit is detected. Controller 116 can also deactivate indicator 122 after a predetermined time period to save power.

[0035] Controller 116 activates or activates a fourth switching element (e.g., L2) for a period of time (e.g., 1-5 microseconds), as illustrated in block 336. Controller 116 measures the current flowing through the half-bridge or full-power stage of the fourth switching element, as illustrated in block 338, and deactivates or deactivates the fourth switching element (e.g., L2), as illustrated in block 340. Controller 116 determines whether the measured current is greater than or equal to a second threshold, as illustrated in block 342. When the measured current is greater than or equal to the second threshold, controller 116 deactivates power to controller 116, as illustrated in block 332, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 334. When the measured current is less than the second threshold, controller 116 continues the process and checks the next switching element. Controller 116 can continue the process and check the next switching element even if a short circuit is detected. Controller 116 can also deactivate indicator 122 after a predetermined period of time to save power.

[0036] Controller 116 activates or activates the fifth switching element (e.g., H3) for a period of time (e.g., 1-5 microseconds), as illustrated in block 344. Controller 116 measures the current flowing through the half-bridge or full-power stage of the fifth switching element, as illustrated in block 346, and deactivates or deactivates the fifth switching element (e.g., H3), as illustrated in block 348. Controller 116 determines whether the measured current is greater than or equal to a second threshold, as illustrated in block 350. When the measured current is greater than or equal to the second threshold, controller 116 deactivates power to controller 116, as illustrated in block 352, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 354. When the measured current is less than the second threshold, controller 116 continues the process and checks the next switching element. Controller 116 can continue the process and check the next switching element even if a short circuit is detected. Controller 116 can also deactivate indicator 122 after a predetermined time period to save power.

[0037] Controller 116 activates or activates the sixth switching element (e.g., L3) for a period of time (e.g., 1-5 microseconds), as illustrated in block 356. Controller 116 measures the current flowing through the half-bridge or full-power stage of the sixth switching element, as illustrated in block 358, and deactivates or deactivates the sixth switching element (e.g., L3), as illustrated in block 360. Controller 116 determines whether the measured current is greater than or equal to a second threshold, as illustrated in block 362. When the measured current is greater than or equal to the second threshold, controller 116 deactivates power to controller 116, as illustrated in block 352, and indicates a fault condition, for example, by activating indicator 122, as illustrated in block 354. When the measured current is less than the second threshold, no fault is detected, and controller 116 continues normal operation of tool 100, as illustrated in block 364. Even if a short circuit is detected, controller 116 can continue the process and check the next switching element. The controller 116 can also deactivate the indicator 122 after a predetermined period of time to save power.

[0038] It should be recognized that the switching elements (L1, L2, L3, H1, H2, and H3) can be checked individually in any order via method 300. By testing each switching element individually, the controller 116 can determine whether the short-circuited switching element is the opposite of the half-bridge under test. For example, if the high-side switching element (H1) is on and the current is greater than or equal to a second threshold (e.g., 5A), then the low-side switching element (L1) in that half-bridge is short-circuited. This two-step switching element short-circuit detection can be performed each time the controller 116 is powered on (as an initial diagnostic check) and each time the trigger 110 is actuated, so that a short circuit is not introduced or reintroduced into the controller circuitry. This reduces the risk of damage to the controller 116, power supply 120, and other components of tool 100 due to a short-circuit event.

[0039] As discussed herein, tool 100 is a ratchet wrench. However, tool 100 can be any type of handheld power tool, including but not limited to electrically driven or power tools such as drills, routers, or impact wrenches, ratchet wrenches, screwdrivers, or other power tools powered by an external power source (e.g., a wall outlet and / or generator outlet) or battery. Furthermore, it should be understood that the invention is not limited to use with power tools, but can be used with any device utilizing a BLDC motor.

[0040] As used herein, the term "connecting" and its functional equivalents are not intended to be limited to a direct mechanical connection of two or more components. Rather, the term "connecting" and its functional equivalents are intended to mean any direct or indirect mechanical, electrical, or chemical connection between two or more objects, features, workpieces, and / or environmental substances. In some examples, "connecting" is also intended to mean the integration of one object with another. As used herein, the term "a" or "an" may include one or more items unless otherwise specified.

[0041] The contents set forth in the foregoing specification and drawings are provided by way of illustration only and not as limitation. Although specific embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications can be made without departing from the broader aspects of the inventors' contributions. The actual scope of protection sought is intended to be defined by the appended claims when viewed from a suitable perspective based on the prior art.

Claims

1. A power tool comprising a motor, a power supply, and a switching element, the tool including: A controller adapted to perform a short-circuit check, wherein during the short-circuit check, the controller is adapted to: A first short-circuit check is performed during the bootstrap capacitor charging process by activating the low-side switching element of the switching element; as well as A second short-circuit check is performed after the first short-circuit check, wherein during the second short-circuit check, the controller is adapted to: The switching element can be started and stopped individually; Measure the first current corresponding to when at least one of the switching elements is activated; as well as When the measured first current meets or exceeds the first threshold current, it causes an indication that a short circuit fault has occurred in the other half of the measured half-bridge in the switching element.

2. The power tool according to claim 1, characterized in that, The controller is adapted to individually start and stop the switching element, and measures the first current by means of the following steps: Activate the first switching element among the switching elements; Measure the first current, wherein the first current corresponds to the first switching element; as well as The first switching element is deactivated.

3. The power tool according to claim 1, characterized in that, It also includes an indicator, wherein the controller is adapted to induce an indication of the short-circuit fault by activating the indicator.

4. The power tool according to claim 1, characterized in that, The controller is also adapted to deactivate the power supplied to the motor when the measured first current meets or exceeds the first threshold current.

5. The power tool according to claim 1, characterized in that, The controller is adapted to perform the first short-circuit check by simultaneously or individually activating the low-side switching element of the switching element.

6. The power tool according to claim 5, characterized in that, During the first short-circuit check, the controller is also adapted to: Measure the second current corresponding to at least one of the low-side switching elements; and An indication that a fault is caused when the measured second current meets or exceeds the second threshold current.

7. The power tool according to claim 6, characterized in that, It also includes an indicator, wherein the controller is adapted to induce an indication of the fault by activating the indicator.

8. The power tool according to claim 6, characterized in that, The controller is also adapted to deactivate the power supplied to the motor when the measured second current meets or exceeds the second threshold current.

9. A method for operating a brushless DC motor of a tool, wherein the brushless DC motor includes a switching element and is powered by a power supply, the method comprising: A first short-circuit check is performed during the bootstrap capacitor charging process by activating the low-side switching element of the switching element; as well as A second short-circuit check is performed after the first short-circuit check, wherein the second short-circuit check includes: The switching element can be started and stopped individually; Measure the first current corresponding to when at least one of the switching elements is activated; and When the measured first current meets or exceeds the first threshold current, it indicates that a short circuit fault has occurred in the other half of the measured half-bridge in the switching element.

10. The method according to claim 9, characterized in that, Individually activating and deactivating the switching element and measuring the first current includes: Activate the first switching element among the switching elements; Measuring the first current, wherein the first current corresponds to the first switching element; and The first switching element is deactivated.

11. The method according to claim 10, characterized in that, The second short-circuit check also includes: Activate the second switching element in the switching elements; Measure a second current, wherein the second current corresponds to the second switching element; Deactivate the second switching element; and A short-circuit fault is indicated when the measured second current meets or exceeds the first threshold current.

12. The method according to claim 9, characterized in that, The short-circuit fault is indicated by a start-up indicator.

13. The method according to claim 9, characterized in that, Also includes: When the measured first current meets or exceeds the first threshold current, the power supply to the brushless DC motor is stopped.

14. The method according to claim 9, characterized in that, The first short-circuit check includes activating the low-side switching element simultaneously or individually.

15. The method according to claim 14, characterized in that, The first short-circuit check also includes: Measure the second current corresponding to at least one of the low-side switching elements; and A fault is indicated when the measured second current meets or exceeds the second threshold current.

16. The method according to claim 15, characterized in that, The fault is indicated by a startup indicator.

17. The method according to claim 15, characterized in that, Also includes: When the measured second current meets or exceeds the second threshold current, the power supply to the brushless DC motor is stopped.

18. A controller for a tool and adapted to control a brushless DC motor including switching elements, said controller comprising: Processing unit, which is suitable for: A first short-circuit check is performed during the bootstrap capacitor charging process by activating the low-side switching element of the switching element; as well as A second short-circuit check is performed after the first short-circuit check, wherein the second short-circuit check includes: Activate the first switching element among the switching elements; Measure the first current corresponding to the first switching element; Deactivate the first switching element; When the measured first current meets or exceeds the first threshold current, it causes an indication that a first fault has occurred in one of the switching elements; When the measured first current is less than the first threshold current, the second switching element in the switching element is activated; Measure the second current corresponding to the second switching element; The second switching element is deactivated; and an indication that a second fault has occurred is generated when the measured second current meets or exceeds the first threshold current.

19. The controller according to claim 18, characterized in that, Indicators that the first fault or the second fault has occurred include a start indicator.

20. The controller according to claim 18, characterized in that, The processing unit is also adapted to shut down the power supply to the brushless DC motor when the measured first current meets or exceeds the first threshold current.

21. The controller according to claim 18, characterized in that, The first short-circuit check includes: The low-side switching element of the switching element is activated simultaneously or individually; Measure the third current corresponding to at least one of the low-side switching elements; and An indication that a third fault is triggered when the measured third current meets or exceeds the second threshold current.

22. The controller according to claim 21, characterized in that, The processing unit is also adapted to shut down the power supply to the brushless DC motor when the measured third current meets or exceeds the second threshold current.

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