Current sensing in electric tool device using field-effect transistor

Abstract

To measure a current flowing through a field-effect transistor based on a voltage, without using a shunt resistance.SOLUTION: An electric tool device 100 comprises a housing, a power supply interface, a field-effect transistor inside the housing connected between the power supply interface and a load 290 of the electric tool device 100, and an electronic processor 200 coupled to the field-effect transistor. The electronic processor 200 is configured to drive the load 290 by controlling the field-effect transistor and to measure a voltage at a terminal of the field-effect transistor. The electronic processor 200 is also configured to determine a current flowing through the field-effect transistor based on the voltage, without using a shunt resistance.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] (Reference to Related Application) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 094,100, filed October 20, 2020, the entire contents of which are incorporated herein by reference. Summary of the Invention

[0002] A power tool device described herein includes a housing, a power interface, a field effect transistor in the housing connected between the power interface and a load of the power tool device, and an electronic processor coupled to the field effect transistor. The electronic processor is configured to control the field effect transistor to drive the load and measure a voltage at terminals of the field effect transistor. The electronic processor is also configured to determine a current through the field effect transistor based on the voltage without using a shunt resistor.

[0003] In some embodiments, the terminal is the source of a field effect transistor.

[0004] In some aspects, the power tool device also includes an inverter circuit coupled between the power interface and the load, the field effect transistor being a component of the inverter circuit.

[0005] In some aspects, the field effect transistor is a low-side field effect transistor of an inverter circuit.

[0006] In some aspects, the power tool device also includes a bias resistor coupled between the current sense terminal of the low-side field effect transistor and ground, the connection point between the current sense terminal and the bias resistor being used to measure voltage.

[0007] In some embodiments, the field effect transistor is a high-side field effect transistor of an inverter circuit.

[0008] In some embodiments, the power tool device also includes an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

[0009] In some aspects, the power tool device is a demolition hammer and the housing includes a tool holder configured to receive a chisel.

[0010] In some aspects, the power tool device is a chainsaw.

[0011] A power tool described herein includes a housing, a power interface coupled to the housing, a motor within the housing, and an inverter circuit within the housing coupled between the power interface and the motor. The inverter circuit includes a plurality of high-side FETs coupled between the positive power terminal of the power interface and the motor, and a plurality of low-side FETs coupled between the motor and the negative power terminal of the power interface. The power tool also includes an electronic processor coupled to the plurality of high-side FETs and the plurality of low-side FETs. The electronic processor is configured to activate a first pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a first phase of the motor and measure current through the motor using the first activation FET in response to the first phase of the motor being activated. The electronic processor is also configured to activate a second pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a second phase of the motor and measure current through the motor using the second activation FET in response to the second phase of the motor being activated. The electronic processor is further configured to activate a third pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a third phase of the motor, and measure current through the motor using the third activation FET in response to the second phase of the motor being activated.

[0012] In some embodiments, the electronic processor is also configured to measure a first voltage at a first source terminal of the first activation FET and determine the first current based on the first voltage.

[0013] In some embodiments, the first activation FET is one of the plurality of low-side FETs.

[0014] In some embodiments, the power tool device also includes a bias resistor coupled between the first source terminal of the first activation FET and ground, the connection point between the first source terminal and the bias resistor being used to measure the first voltage.

[0015] In some embodiments, the first activation FET is one of the plurality of high-side FETs.

[0016] In some embodiments, the electronic processor is also configured to measure a second voltage at a second source terminal of the second activation FET and determine a second current based on the second voltage.

[0017] In some embodiments, the electronic processor is also configured to measure a third voltage at a third source terminal of the third activation FET and determine a third current based on the third voltage.

[0018] The work site lighting device described herein includes a housing, a power interface, a FET in the housing coupled between the power interface and a load of the work site lighting device, and an electronic processor coupled to the FET. The electronic processor is configured to control the FET to drive the load and measure a voltage at terminals of the FET. The electronic processor is also configured to determine a current through the FET based on the voltage.

[0019] In some embodiments, the terminal is the source of a FET.

[0020] In some aspects, the worksite lighting device also includes a bias resistor coupled between the terminal and ground, the connection point between the terminal and the bias resistor being used to measure voltage.

[0021] In some embodiments, the worksite lighting device also includes an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

[0022] A worksite lighting device described herein includes a housing, a power interface, a battery pack, a charge FET in the housing coupled between the power interface and the battery pack, and an electronic processor coupled to the charge FET. The electronic processor is configured to control the charge FET to charge the battery pack and measure a voltage at the terminals of the FET. The electronic processor is also configured to determine a charge current through the charge FET based on the voltage.

[0023] In some embodiments, the terminal is the source of a charge FET.

[0024] In some aspects, the worksite lighting device also includes a bias resistor coupled between the terminal and ground, the connection point between the terminal and the bias resistor being used to measure voltage.

[0025] In some embodiments, the worksite lighting device also includes an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

[0026] A battery pack described herein includes a housing, a device interface on the housing, a plurality of battery cells within the housing, a charge / discharge FET within the housing coupled between the plurality of battery cells and the device interface, and an electronic processor coupled to the charge / discharge FET. The electronic processor is configured to control the charge / discharge FET to charge / discharge the plurality of battery cells and measure a voltage at terminals of the FET. The electronic processor is also configured to determine a charge / discharge current flowing through the charge / discharge FET based on the voltage.

[0027] In some embodiments, the terminal is the source of a charge / discharge FET.

[0028] In some embodiments, the battery pack also includes a bias resistor coupled between the terminal and ground, the connection point between the terminal and the bias resistor being used to measure the voltage.

[0029] In some embodiments, the battery pack also includes an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

[0030] A method described herein for current sensing in a power tool includes using an electronic processor of the power tool to activate a first pair of multiple high-side field effect transistors (FETs) and multiple low-side FETs to activate a first phase of a motor, and measuring a first current through the motor using the first activation FETs in response to activating the first phase of the motor. The multiple high-side FETs and low-side FETs are provided in an inverter bridge of the power tool coupled between a power interface and a motor of the power tool. The method also includes activating a second pair of multiple high-side FETs and multiple low-side FETs to activate a second phase of the motor, and measuring a second current through the motor using the second activation FET in response to the second phase of the motor being activated. The method also includes activating a third pair of multiple high-side FETs and multiple low-side FETs to activate a third phase of the motor, and measuring a third current through the motor using the third activation FET in response to the third phase of the motor being activated.

[0031] In some embodiments, the method also includes measuring a first voltage at a first source terminal of the first activation FET and determining a first current based on the first voltage.

[0032] In some embodiments, the method also includes measuring a second voltage at a second source terminal of the second activation FET and determining a second current based on the second voltage.

[0033] In some embodiments, the method also includes measuring a third voltage at a third source terminal of the third activation FET and determining a third current based on the third voltage.

[0034] Before describing any embodiments in detail, it is to be understood that the embodiments are not limited in their application to the details of construction and arrangement of components set forth in the following description or illustrated in the accompanying drawings. The embodiments may be 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 "comprises," "includes," or "having" and variations thereof is intended to encompass the items listed thereafter and equivalents thereof, as well as additional items. Unless otherwise expressly stated or limited, the terms "mounted," "connected," "supported," and "coupled," and variations thereof, are used broadly and encompass both direct and indirect mounting, connecting, supporting, and coupling.

[0035] Additionally, it should be understood that the embodiments may include hardware, software, and electronic components or modules, which, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, upon reading this detailed description, one of ordinary skill in the art will recognize that, in at least one embodiment, electronic-based aspects may be implemented in software (e.g., software stored on a non-transitory computer-readable medium) executable by one or more processing units, such as a microprocessor and / or application-specific integrated circuits ("ASICs"). As such, it should be noted that the embodiments may be implemented using a number of hardware- and software-based devices and a number of different structural elements. For example, the terms "server," "computing device," "controller," "processor," etc., as used herein may include one or more processing units, one or more computer-readable media modules, one or more input / output interfaces, and various connections (e.g., a system bus) connecting the elements.

[0036] Those skilled in the art will understand that relative terms, such as "about," "approximately," "substantially," etc., used in connection with a quantity or state are inclusive of the declared value and have the meaning dictated by the context (e.g., the term includes at least the error associated with the precision of measurement, the tolerance associated with a particular value (e.g., manufacture, assembly, use, etc.)). Such terms should also be considered to indicate a range defined by the absolute values ​​of the two endpoints. For example, the phrase "about 2 to about 4" indicates a range of "2 to 4." Relative terms may refer to a percentage increase or decrease (e.g., 1%, 5%, 10% or more) of the stated value.

[0037] While certain drawings illustrate hardware and software within particular devices, it should be understood that these depictions are for illustrative purposes only. Functionality described herein as being performed by one element may be performed in a distributed manner by multiple components. Similarly, functionality performed by multiple elements may be integrated and performed by a single element. In some embodiments, illustrated components may be combined or divided into separate software, firmware, and / or hardware components. For example, logic and processing may be distributed across multiple electronic processors rather than being within and performed by a single electronic processor. Regardless of how they are combined or divided, hardware and software components may reside on the same computing device or be distributed among different computing devices connected by one or more networks or other suitable communications links. Similarly, components described as performing a particular function may also perform additional functions not described herein. For example, a device or structure "configured" in a particular way is configured in at least that way, but may also be configured in multiple ways not explicitly recited.

[0038] Other aspects of the embodiments will become apparent by consideration of the detailed description and accompanying drawings. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a block diagram of a current sensing circuit used in a power tool device. [Figure 2] 1 illustrates a handheld power tool according to some embodiments. [Figure 3] FIG. 3 is a block diagram of the power tool of FIG. 2 according to some embodiments. [Figure 4A] 3 is a simplified block diagram illustrating a FET switching module of the power tool of FIG. 2 according to some embodiments. [Figure 4B] 3 is a simplified block diagram illustrating a FET switching module of the power tool of FIG. 2 according to some embodiments. [Figure 5] 3 is a flowchart of a method for current sensing in the power tool of FIG. 2 according to some embodiments. [Figure 6] 1 illustrates a high power power tool according to some embodiments. [Figure 7] FIG. 7 is a simplified block diagram illustrating a FET switching module of the power tool of FIG. 6 according to some embodiments. [Figure 8A] FIG. 1 illustrates a worksite lighting device according to some embodiments. [Figure 8B] FIG. 1 illustrates a worksite lighting device according to some embodiments. [Figure 9] FIG. 8C is a block diagram of the worksite lighting device of FIGS. 8A-8B, according to some embodiments. [Figure 10] FIG. 8C is a simplified block diagram illustrating an LED driver of the worksite lighting device of FIGS. 8A-8B, according to some embodiments. [Figure 11] FIG. 8C is a simplified block diagram illustrating a charging circuit for the worksite lighting device of FIGS. 8A-8B, according to some embodiments. [Figure 12] 1 illustrates an outdoor power tool according to some embodiments. [Figure 13] FIG. 1 illustrates a battery pack, according to some embodiments. [Figure 14] FIG. 1 illustrates a battery pack, according to some embodiments. [Figure 15] FIG. 1 illustrates a battery pack, according to some embodiments. [Figure 16] FIG. 16 is a block diagram of the battery pack of FIGS. 13-15, according to some embodiments. [Figure 17] FIG. 16 is a simplified block diagram illustrating a charge / discharge module of the battery pack of FIGS. 13-15, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0040] Current sensing is used to implement various functions in power tool devices. For example, current sensing is used to implement e-clutches, load-based speed control, temperature estimation, and overcurrent protection. FIG. 1 shows an exemplary current sensing circuit 10 for use in a power tool device. The current sensing circuit 10 includes an inverter bridge 14 coupled between a power source and a load. The inverter bridge 14 is controlled by an electronic processor 18. In the illustrated example, the inverter bridge 14 is a three-phase inverter and includes three high-side FETs 22 and three low-side FETs 26 that are activated and deactivated in pairs to control each phase of the load.

[0041] Shunt resistors 30 are coupled between the three low-side FETs 26 and ground. The current sensing circuit 10 includes three shunt resistors 30, one for each phase. The shunt resistors 30 form the current sensing elements of the power tool device. The voltage across the shunt resistors 30 is amplified using an amplifier 34 and provided to the electronic processor 18. The electronic processor 18 receives the amplified voltage signal and includes an analog-to-digital converter (ADC) 38 that converts the amplified voltage signal to a digital equivalent. The electronic processor 18 determines the current based on the digital equivalent and the resistance of the shunt resistors 30.

[0042] 2 shows an exemplary power tool 100 in the form of a hammer drill / driver. The power tool 100 includes an upper main body 105, a handle portion 110, a battery pack receptacle 115, and a trigger 120. The battery pack receptacle 115 receives a battery pack 1000 (see FIG. 13 ) and includes a terminal assembly including a plurality of terminals. The number of terminals present in the receptacle 115 may vary based on the type of power tool 100. However, by way of illustration, the receptacle and terminal assembly may include a positive battery (“B+”) terminal, a negative battery (“B−”) terminal, a sensing or communication terminal, an identification terminal, etc.

[0043] The positive and negative battery terminals electrically connect the battery pack to the handheld power tool 100 and are operable to provide operating power (i.e., voltage and current) to the power tool 100. The sensor or communication terminals are operable to provide communication or sensing of the battery pack to the power tool 100. The identification terminals may be used by the battery pack or the handheld power tool to identify the other.

[0044] 3 shows a block diagram of the power tool 100. In the illustrated example, the power tool 100 includes a controller (e.g., electronic processor 200) electrically and / or communicatively connected to various modules or components of the power tool 100. For example, the illustrated electronic processor 200 is connected to a battery pack interface 205, a power input module 210, a FET switching module 215, one or more sensors 220, a trigger switch 225 (connected to the trigger 120), a transceiver 230, a user input module 235, and one or more indicators 240. In some embodiments, the trigger switch 225 is combined and integrated with the electronic processor 200 within a housing (e.g., the upper main body 105 and the handle portion 110) within the power tool 100. The electronic processor 200 includes a combination of hardware and software operable to, among other things, control the operation of the power tool 100, activate one or more indicators 240 (e.g., LEDs), monitor the operation of the power tool 100, communicate with associated external devices (e.g., a smartphone), etc.

[0045] In some embodiments, electronic processor 200 includes multiple electrical and electronic components that provide power, operational control, and protection for electronic processor 200 and / or components and modules within power tool 100. For example, electronic processor 200 includes, among other things, a processing unit 250 (e.g., a microprocessor, microcontroller, electronic processor, or another suitable programmable device), a memory 255, an input unit 260, and an output unit 265. Processing unit 250 includes, among other things, a control unit 270, an arithmetic logic unit (“ALU”) 275, and multiple registers 280 (shown as a group of registers in FIG. 3 ) and is implemented using known computer architectures such as a modified Harvard architecture, a von Neumann architecture, etc. Processing unit 250, memory 255, input unit 260, and output unit 265, as well as the various modules connected to electronic processor 200, are connected by one or more control and / or data buses (e.g., a common bus 285). The control and / or data buses are shown generally in Figure 3 for purposes of illustration. The use of one or more control and / or data buses for interconnection and communication between the various modules and components will be apparent to those skilled in the art upon review of the invention described herein.

[0046] Memory 255 is a non-transitory computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and data storage area may include a combination of different types of memory, such as read-only memory (“ROM”), random-access memory (“RAM”) (e.g., dynamic RAM [“DRAM”], synchronous DRAM [“SDRAM”], etc.), electrically erasable programmable read-only memory (“EEPROM”), flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory devices. Processing unit 250 is coupled to memory 255 and executes software instructions that may be stored in the RAM of memory 255 (e.g., during execution), in the ROM of memory 255 (e.g., on a generally persistent basis), or in another non-transitory computer-readable medium, such as another memory or a disk. Software included in implementations of power tool 100 may be stored in memory 255 of electronic processor 200. Software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. Electronic processor 200 is configured to retrieve and execute instructions from memory, particularly those related to the control processes and methods described herein. In other configurations, electronic processor 200 may include additional components, fewer components, or different components.

[0047] The battery pack interface 205 includes a combination of mechanical and electrical components configured and operable to interface with a battery pack (e.g., battery pack 1000, battery pack 1100, or battery pack 1200 of FIGS. 13-15). For example, power provided by the battery pack to the power tool 100 is provided to a power input module 210 via the battery pack interface 205. The power input module 210 includes a combination of active and passive components to condition or control the power received from the battery pack before power is provided to the electronic processor 200. The battery pack interface 205 also provides power to a FET switching module 215, which is switched by a switching FET within the FET switching module 215 to selectively provide power to the motor 290. The battery pack interface 205 also includes a communication line 295 for providing a communication line or link between the electronic processor 200 and the battery pack, for example.

[0048] Motor 290 may be, for example, a brushless direct current (BLDC) motor. Motor 290 is operated to actuate an output (e.g., a drill bit) on a workpiece. Motor 290 is controlled by a user using trigger 120. When a user activates trigger 120, electronic processor 200 controls the drive of motor 290. FET switching module 215 includes an H-bridge or inverter bridge (shown in FIGS. 1 and 4) used to control motor 290. Electronic processor 200 provides PWM signals to the H-bridge or inverter bridge to control the speed and direction of motor 290 based on signals received from trigger 120 and a rotor position sensor / estimator.

[0049] The one or more sensors 220 may include, among others, one or more temperature sensors, one or more Hall Effect sensors, etc. For example, the speed of the motor 290 may be determined using multiple Hall Effect sensors to sense the rotational position of the rotor of the motor 290. In some embodiments, a voltage sensor or a current sensor may be used to measure the rotational position of the rotor of the motor 290. The trigger switch 225 is connected to the trigger 120 to control the power provided to the motor 290 via the switching FET. In some embodiments, the amount of trigger pull detected by the trigger switch 225 is related to or corresponds to a desired rotational speed of the motor 290. In other embodiments, the amount of trigger pull detected by the trigger switch 225 is related to or corresponds to a desired torque.

[0050] The transceiver 230 is operatively coupled to the electronic processor 200 to enable wired and / or wireless communication with, for example, an external device (e.g., a user's smartphone, a connected display or control unit, etc.). The transceiver 230 enables the electronic processor 200 to receive input from the external device and provide output for display on the external device. In some embodiments, the trigger 120, the indicator 240, and the user input module 235 may be implemented as inputs and / or outputs on the external device. Inputs from, and outputs to, the external device are received and provided via the transceiver 230.

[0051] The user input module 235 is operably coupled to the electronic processor 200 to, for example, select a forward or reverse operating mode, torque and / or speed settings for the power tool 100 (e.g., using torque and / or speed switches). In some embodiments, the user input module 235 includes a combination of digital and analog input or output devices necessary to achieve a desired level of operation of the power tool 100, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc. The indicator 240 includes, for example, one or more light emitting diodes ("LEDs") and is configured to indicate a measured electrical characteristic of the power tool 100, a status of the power tool 100, etc.

[0052] As mentioned above, in one embodiment, shunt resistor 30 is used to sense motor current in power tool 100. FIG. 4A is a simplified block diagram of power tool 100 showing FET switching module 215 in further detail, according to another exemplary embodiment. In the example shown in FIG. 4A, power tool 100 uses current-sensing power metal-oxide semiconductor field-effect transistors (MOSFETs) to sense current rather than shunt resistor 30. FET switching module 215 includes an inverter bridge having six power MOSFETs. Three high-side FETs 305 are coupled between the positive battery terminal (B+) and motor 290, and three low-side FETs 310 are coupled between motor 290 and the negative battery terminal (B−).

[0053] During operation, the electronic processor 200 provides pulse-width modulated (PWM) signals to the FETs 305, 310 to activate and deactivate the FETs 305, 310. The motor 290 is, for example, a three-phase motor, and each phase of the motor 290 is operated to cause rotational movement of the rotor of the motor 290. A first pair of FETs, for example, a first high-side FET 305A and a second low-side FET 310A, is activated to activate the first phase of the motor 290. The first pair of FETs is then deactivated based on the PWM signal, and a second pair of FETs, for example, a second high-side FET 305B and a third low-side FET 310C, is activated to activate the second phase of the motor 290. The second pair of FETs is deactivated based on the PWM signal, and a third pair of FETs, e.g., the third high-side FET 305C and the first low-side FET 310A, is activated to activate the third phase of the motor 290.

[0054] The electronic processor 200 includes a gate driver that provides a PWM signal to the FETs 305, 310. The PWM signal is provided to the gate terminals of the FETs 305, 310. The drain terminal of the high-side FET 305 is coupled to the positive battery terminal (B+), and the source terminal of the high-side FET 305 is coupled to a common node 315 that is connected to the motor 290. The drain terminal of the low-side FET 310 is coupled to the common node 315, and the source terminal of the low-side FET is coupled to ground.

[0055] In the example shown in FIG. 4A , shunt resistor 30 and amplifier 34 are removed from power tool 100. Instead, the current sense terminal (e.g., separate from the source terminal) of low-side FET 310 is coupled to electronic processor 200. FETs 305 and 310 are, for example, power MOSFETs, each including an internal resistance of, for example, 0.5 mΩ to 2.0 mΩ. Bias resistor 320 is coupled between the source terminal of low-side FET 310 and ground. A junction 325 (shown generally with respect to the source terminal for illustrative purposes only) between the current sense terminal of low-side FET 310 and bias resistor 320 is connected to electronic processor 200. The internal resistance (e.g., drain-source resistance) of low-side FET 310 and bias resistor 320 function as a voltage divider to provide a voltage signal to electronic processor 200. Electronic processor 200 includes an analog-to-digital converter (ADC) 330 that receives the voltage signal from junction 325. The ADC converts the analog voltage signal received from junction 325 to a digital equivalent. The electronic processor 200 determines the current using a digital equivalent, for example, by dividing the voltage signal value by the internal resistance of the low-side FET 310.

[0056] Replacing the shunt resistor 30 and amplifier 34 results in a smaller electronic package, increased efficiency, and thermal improvements for the power tool. Specifically, the larger chip-based shunt resistor 30 and amplifier 34 are replaced with a smaller bias resistor 320, resulting in a smaller electronic package. Any heat loss through the shunt resistor 30 is also avoided in the modified design illustrated in FIG. 4A.

[0057] In the example shown in FIG. 4 , only the low-side FET 310 is implemented as a current-sensing power MOSFET, while the high-side FET 305 is implemented as a conventional power MOSFET. In some embodiments, both the high-side FET 305 and the low-side FET 310 can be implemented as current-sensing power MOSFETs to provide additional / redundant current sensing capability. In these embodiments, both the active phase high-side FET 305 and the low-side FET 310 can be used to monitor the current. Replacing only the low-side FET 310 as a current-sensing power MOSFET provides further cost savings compared to replacing all FETs 305, 310 with current-sensing power MOSFETs. Eliminating the shunt resistor 30 also allows for the selection of power MOSFETs with higher internal resistance. Therefore, further cost savings can be achieved while maintaining the same power efficiency of the inverter bridge. The power tool 100 is then controlled (e.g., turning off the motor) based on the sensed current.

[0058] 4B shows a modified embodiment of the circuit of FIG. 4A in which all three of nodes 325 are tied together and a single bias resistor is used. As a result of this connection, the sensed currents from all three phases of the motor are summed together and provided to ADC 330.

[0059] 5 is a flowchart of an example method 400 for current sensing in a power tool 100. The method 400 includes using the electronic processor 200 to activate a first pair of multiple high-side FETs 305 and multiple low-side FETs 310 to activate a first phase of the motor 290 (block 410). The electronic processor 200 provides PWM signals for activating and deactivating the FETs. To activate the first phase of the motor 290, the electronic processor 200 activates, for example, the first high-side FET 305A and the second low-side FET 310B. When the first high-side FET 305A and the second low-side FET 310B are activated, current flows from the positive battery terminal through FET 305A, motor phases U, V, and FET 310B to the negative battery terminal or ground. During the first phase of activation, the other FETs 305B, 305C, 310A, 310C may be deactivated so that no current flows through the FETs 305B, 305C, 310A, 310C.

[0060] The method 400 includes using the electronic processor 200 to measure a current through the motor using a first activation FET (e.g., the second low-side FET 310B) in response to a first phase of the motor 290 being activated (block 420). When the first phase is activated, current flows through the first high-side FET 305A and the second low-side FET 310B. Thus, the electronic processor 200 receives a voltage signal from the second low-side FET 310B and determines the current through the motor 290 based on the voltage signal from the second low-side FET 310B. In some embodiments, the electronic processor 200 measures the current based on the voltage signal from the first high-side FET 305A.

[0061] The method 400 includes using the electronic processor 200 to activate a second pair of the multiple high-side FETs 305 and multiple low-side FETs 310 to activate a second phase of the motor 290 (block 430). The electronic processor 200 provides PWM signals for activating and deactivating the FETs. To activate the second phase of the motor 290, the electronic processor 200 activates, for example, the second high-side FET 305B and the third low-side FET 310C. When the second high-side FET 305B and the third low-side FET 310C are activated, current flows from the positive battery terminal through FET 305B, motor phases V and W, and FET 310C to the negative battery terminal or ground. During activation of the second phase, the other FETs 305A, 305C, 310A, and 310B may be deactivated so that no current flows through the FETs 305A, 305C, 310A, and 310B.

[0062] The method 400 includes using the electronic processor 200 to measure a current through the motor using a second activation FET (e.g., the third low-side FET 310C) in response to a second phase of the motor 290 being activated (block 440). When the second phase is activated, current flows through the second high-side FET 305B and the third low-side FET 310C. Thus, the electronic processor 200 receives a voltage signal from the third low-side FET 310C and determines the current through the motor 290 based on the voltage signal from the third low-side FET 310C. In some embodiments, the electronic processor 200 measures the current based on the voltage signal from the second high-side FET 305B.

[0063] The method 400 includes using the electronic processor 200 to activate a third pair of the multiple high-side FETs 305 and multiple low-side FETs 310 to activate a third phase of the motor 290 (block 450). The electronic processor 200 provides PWM signals for activating and deactivating the FETs. To activate the third phase of the motor 290, the electronic processor 200 activates, for example, the third high-side FET 305C and the first low-side FET 310A. When the third high-side FET 305C and the first low-side FET 310A are activated, current flows from the positive battery terminal through FET 305C, motor phases W, U, and FET 310A to the negative battery terminal or ground. During activation of the third phase, the other FETs 305A, 305B, 310B, and 310C may be deactivated so that no current flows through the FETs 305A, 305B, 310B, and 310C.

[0064] Method 400 includes using electronic processor 200 to measure current through the motor using a third activation FET (e.g., first low-side FET 310A) in response to a third phase of motor 290 being activated (block 460). When the third phase is activated, current flows through third high-side FET 305C and first low-side FET 310A. Thus, electronic processor 200 receives a voltage signal from first low-side FET 310A and determines the current through motor 290 based on the voltage signal from first low-side FET 310A. In some embodiments, electronic processor 200 measures the current based on the voltage signal from third high-side FET 305C. Method 400 is repeated for the duration of operation of power tool 100.

[0065] FIG. 6 shows a high-power power tool 500, such as a demolition hammer or breaker tool. The power tool 500 includes an upper housing 505 and a lower housing 510. The upper housing 505 supports a handle 515 that a user can grasp to operate the power tool 500. An actuator 520 is provided by the handle 515 that acts as a trigger for the power tool 500. The upper housing 505 also receives a battery pack 525 for providing power to the motor of the power tool 500. The lower housing 510 includes a tool holder 530 for receiving a chisel 535. The power tool 500 includes similar components to those shown and described with respect to FIG. 3.

[0066] FIG. 7 shows a simplified block diagram of power tool 500. Power tool 500 illustrated in FIG. 7 includes similar components to power tool 100, with like parts designated by like numerals. In the illustrated example, FET switching module 215 includes an inverter bridge having twelve power MOSFETs. Six high-side FETs 705 are coupled between the positive battery terminal (B+) and motor 290, and six low-side FETs 310 are coupled between motor 290 and the negative battery terminal (B−).

[0067] Specifically, the inverter bridge includes high-side FETs 705A, 705B, and 705C connected in series with high-side FETs 705D, 705E, and 705F, respectively. The drains of high-side FETs 705A, 705B, and 705C are coupled to the positive battery terminal, and the sources of high-side FETs 705A, 705B, and 705C are coupled to the drains of high-side FETs 705D, 705E, and 705F. The inverter bridge also includes low-side FETs 710A, 710B, and 710C connected in series with low-side FETs 710D, 710E, and 710F, respectively. The sources of low-side FETs 710A, 710B, and 710C are coupled to the negative battery terminal or ground, and the drains of low-side FETs 710A, 710B, and 710C are coupled to the sources of low-side FETs 710D, 710E, and 710F. In some embodiments, high-side FETS 705 and low-side FETS 710 are connected as a parallel pair of FETs rather than a series pair of FETs.

[0068] During operation, the electronic processor 200 provides pulse-width modulated (PWM) signals to the FETs 705, 710 to activate and deactivate the FETs 705, 710. A first plurality of FETs, e.g., a first high-side FET 705A, a fourth high-side FET 705D, a second low-side FET 710B, and a fifth low-side FET 710E, are activated to activate a first phase of the motor 290. The first plurality of FETs are then deactivated based on the PWM signal, and a second plurality of FETs, e.g., a second high-side FET 705B, a fifth high-side FET 705E, a third low-side FET 710C, and a sixth low-side FET 710F, are activated to activate a second phase of the motor 290. The second plurality of FETs are deactivated based on the PWM signal, and a third plurality of FETs, e.g., third high-side FET 705C, sixth high-side FET 705F, first low-side FET 710A, and fourth low-side FET 710D, are activated to activate a third phase of motor 290.

[0069] The electronic processor 200 includes a gate driver that provides a PWM signal to the FETs 705 and 710. The PWM signal is provided to the gate terminals of the FETs 705 and 710. Similar to the power tool 100, the shunt resistor 30 and amplifier 34 are eliminated from the power tool 500. Instead, the source terminals of the low-side FETs 710A, 710B, and 710C are coupled to the electronic processor 200. A bias resistor 320 is coupled between the source terminals of the low-side FETs 710A, 710B, and 710C and ground. A junction 325 between the current sense terminals of the low-side FETs 710A, 710B, and 710C and the bias resistor 320 is connected to the electronic processor 200. The internal resistances of the low-side FETs 710A, 710B, and 710C and the bias resistor 320 function as a voltage divider to provide a voltage signal to the electronic processor 200. The ADC 330 converts the analog voltage signal received from junction 325 to its digital equivalent. The electronic processor 200 determines the current using a digital equivalent. In some embodiments, a configuration similar to that shown in Figure 4B is used with a single bias resistor.

[0070] In the example shown in FIG. 7 , only low-side FETs 710A, 710B, and 710C are implemented as current-sensing power MOSFETs, while the remaining FETs 705, 710D, 710E, and 710F are implemented as regular power MOSFETs. In some embodiments, all FETs 705, 710, or a subset of FETs 705, 710, can be implemented as current-sensing power MOSFETs to provide additional / redundant current sensing capability. Replacing only low-side FETs 710A, 710B, and 710C as current-sensing power MOSFETs provides further cost savings compared to replacing all FETs 705, 710 with current-sensing power MOSFETs. Eliminating shunt resistor 30 also allows for the selection of power MOSFETs with higher internal resistance. Therefore, further cost savings can be achieved while maintaining the same power efficiency of the inverter bridge. Power tool 500 is then controlled (e.g., turning off the motor) based on the sensed current.

[0071] 8A-8B show a mobile work site lighting device 800 for illuminating a work site, such as a construction site, or other large area. The lighting device 800 includes a body 805 (e.g., a housing), an extendable arm assembly 810 supported by the body 805, and a light assembly 815 coupled to the extendable arm assembly 810 and movable relative to the body 805. The lighting device 800 also includes a battery pack 820 for providing power to the light assembly 815 and a cooling system 825 for regulating the temperature of the battery pack 820 and other components of the lighting device 800. In some embodiments, the work site lighting device 800 can also function as a charger for charging the battery pack 820. The work site lighting device 800 includes a power cord 830 that can be connected to an external power source, such as a wall outlet. Power from the external power source is then used to power the light assembly 815 and charge the battery pack 820, as described further below.

[0072] FIG. 9 shows a block diagram of a work site lighting system 800. The work site lighting system 800 includes similar components to the power tool 100 shown in FIG. 3, and similar parts are designated by similar numerals. In the work site lighting system 800, a motor 290 is used to move an extendable arm assembly 810. Specifically, the motor 290 moves the extendable arm assembly 810 upward when rotating in a first direction and moves the extendable arm assembly 810 downward when rotating in a second direction. The work site lighting system 800 also includes an LED driver 835 that drives a light 840 in a light assembly 815. The LED driver 835 may be, for example, a constant current driver, a constant voltage driver, or the like, and includes a power MOSFET similar to the FET switching module 215.

[0073] The worksite lighting device 800 includes a charging circuit 845 for charging the battery pack 820 using power received from an external power source 850. Similar to the LED driver 835, the charging circuit 845 may also include a constant current circuit, a constant voltage circuit, etc.

[0074] FIG. 10 shows a simplified block diagram of work site lighting device 800 showing LED driver 835 in further detail, according to one exemplary embodiment. In the example shown in FIG. 10, work site lighting device 800 drives light 840 using current-sensing power MOSFET(s) 855. The drain of FET 855 is coupled to light 840, and the source of FET 855 is coupled to ground. Bias resistor 320 is coupled between the current-sensing terminal of FET 855 and ground. Node 325 between the current-sensing terminal of FET 855 and bias resistor 320 is connected to electronic processor 200. The internal resistance of FET 855 and bias resistor 320 function as a voltage divider to provide a voltage signal to electronic processor 200. Electronic processor 200 includes an analog-to-digital converter (ADC) 330 that receives the voltage signal from node 325. The ADC converts the analog voltage signal received from node 325 to a digital equivalent. Electronic processor 200 uses the digital equivalent to determine the current. 10 shows only one example configuration of LED driver 835. LED driver 835 may have other configurations and may include additional power MOSFETs and / or current sensing power MOSFETs. For example, FET 855 may be provided between the positive battery terminal and light 840, an additional FET 855 may be included for each section of light 840, etc.

[0075] Current sensing is not typically performed in lighting tools such as those described above. Lighting tools do not generate enough current to cause overcurrent or overtemperature problems. However, worksite lighting system 800, in combination with other components of the lighting system, may generate currents high enough to cause overcurrent or overtemperature problems. Therefore, current sensing power MOSFET 855 provides an efficient way to detect the current flowing through light 840 and take necessary protective measures.

[0076] FIG. 11 shows a simplified block diagram of work site lighting device 800 illustrating charging circuit 845 in further detail according to one exemplary embodiment. In the example shown in FIG. 11, work site lighting device 800 uses a current-sensing power MOSFET as a charging FET 860 to charge battery pack 820. The drain of FET 860 is coupled to an external power source 850, for example, via a rectifier. The source of FET 860 is coupled to the positive battery terminal. Bias resistor 320 is coupled between the current-sensing terminal of FET 860 and ground. Node 325 between the current-sensing terminal of FET 860 and bias resistor 320 is connected to electronic processor 200. The internal resistance of FET 860 and bias resistor 320 function as a voltage divider to provide a voltage signal to electronic processor 200. Electronic processor 200 includes an analog-to-digital converter (ADC) 330 that receives the voltage signal from node 325. The ADC converts the analog voltage signal received from node 325 to a digital equivalent. Electronic processor 200 determines the current using a digital equivalent. Figure 11 shows only one example configuration of charging circuit 845. Charging circuit 845 may have other configurations and may include additional power MOSFETs and / or current-sensing power MOSFETs. For example, node 325 may be coupled to the drain of FET 860, etc.

[0077] FIG. 12 shows an exemplary outdoor power tool 900 in the form of a chainsaw. The outdoor power tool 900 includes a main body 905, a handle portion 910, a battery pack receptacle 915, and a trigger 920. The battery pack receptacle 115 receives a battery pack 1100 (see FIG. 14) and includes a terminal assembly including a plurality of terminals. The number of terminals present in the receptacle 915 can vary based on the type of outdoor power tool 900. The outdoor power tool 900 includes power tool 100 and electronic components similar to those described in FIGS. 3, 4A, and 4B.

[0078] FIG. 13 shows an exemplary embodiment of a battery pack 1000 operable to provide power to cordless electric devices (e.g., power tools, outdoor tools, other electric and non-electric devices, etc.). The battery pack 1000 includes a housing 1005 and at least one rechargeable battery cell 1320 (shown in FIG. 16 ) supported by the housing 1005. The battery pack 1000 also includes a support 1010 for supporting the battery pack 1000 on the power tool and coupling the battery pack 1000 to the power tool, and a coupling mechanism 1015 for selectively coupling or releasing the battery pack 1000 from the power tool. In the illustrated embodiment, the support 1010 is connectable to a complementary support on the power tool (e.g., power tool 100). The battery pack 1000 includes a plurality of terminals 1020 of a terminal assembly within a support 1010, operable to electrically connect the battery cells 1320 to a PCB within the battery pack 1000. The plurality of terminals 1020 include, for example, a positive battery terminal, a charging terminal, a ground terminal, and a sensing terminal. In the illustrated example, the battery pack 1000 has a nominal voltage of 18V, 20V, 36V, etc.

[0079] FIG. 14 illustrates a second exemplary embodiment of a battery pack 1100 operable to provide power to a cordless electrical device. The battery pack 1100 can be removably and replaceably connected to a power tool to provide operating power to the power tool. The battery pack 1100 includes a casing 1105, an outer housing 1110 coupled to the casing 1105, and a plurality of battery cells 1320 (shown in FIG. 16) disposed within the casing 1105. The casing 1105 is shaped and sized to fit within an opening and cavity of a power tool (e.g., power tool 900). The casing includes end caps 1115 for substantially enclosing the battery cells 1320 within the casing 1105. The illustrated end cap 1115 includes two power terminals 1120 configured to mate with corresponding power terminals extending from the power tool. In some embodiments, the end cap 1115 may include terminals extending from the battery pack 1100 and configured to be received in a receptacle supported by the power tool. The end cap 1115 may include sensing terminals configured to mate with corresponding terminals from the power tool. In the illustrated example, the battery pack 1000 has a nominal voltage of 12V, 14.2V, etc.

[0080] FIG. 15 shows an exemplary embodiment of a high-voltage battery pack 1200 operable for a high-voltage electric device (e.g., a power tool, an outdoor tool, other electric and non-electric devices, etc.). The battery pack 1200 includes a housing 1205 and at least one rechargeable battery cell 1320 (shown in FIG. 16 ) supported by the housing 1205. The battery pack 1200 also includes a support 1210 for supporting the battery pack 1200 on the electric device and coupling the battery pack 1200 to the electric device, and a coupling mechanism 1215 for selectively coupling or releasing the battery pack 1200 from the electric device. In the illustrated embodiment, the support 1210 is connectable to a complementary support on the electric device (e.g., a power tool 500, a work site lighting system 800, etc.). The battery pack 1200 includes a plurality of terminals 1220 of a terminal assembly within the support 1210, operable to electrically connect the battery cells 1320 to a PCB within the battery pack 1200. The plurality of terminals 1220 include, for example, a positive battery terminal, a low power terminal, a charging terminal, a ground terminal, and a sensing terminal. In the illustrated example, the battery pack 1200 has a nominal voltage of 60V, 80V, 120V, etc.

[0081] FIG. 16 is a block diagram of the battery packs 1000, 1100, and 1200. FIG. 16 illustrates a controller (e.g., electronic processor 1300) associated with the battery packs 1000, 1100, and 1200. The electronic processor 1300 is electrically and / or communicatively connected to the various modules or components of the battery packs 1000, 1100, and 1200. For example, the illustrated electronic processor 1300 is connected to a fuel gauge 1305, one or more sensors 1310, a device interface 1315, a plurality of battery cells 1320, and a charge / discharge control module 1325 within the battery packs. The electronic processor 1300 includes a combination of hardware and software operable to, among other things, control the operation of the battery packs 1000, 1100, and 1200, activate the fuel gauge 1305 (e.g., including one or more LEDs), monitor the operation of the battery packs 1000, 1100, and 1200, and the like. The one or more sensors 1310 include, among other things, one or more temperature sensors, one or more voltage sensors, etc. The electronic processor 1300 also includes various preset or calculated fault condition values ​​related to temperature, current, voltage, etc. associated with the operation of the electrical device.

[0082] In some embodiments, electronic processor 1300 includes multiple electrical and electronic components that provide power, operational control, and protection for components and modules within electronic processor 1300 and / or battery packs 1000, 1100, 1200. For example, electronic processor 1300 includes, among other things, a processing unit 1330 (e.g., a microprocessor, microcontroller, or another suitable programmable device), a memory 1335, an input unit 1340, and an output unit 1345. Processing unit 1330 includes, among other things, a control unit 1350, an arithmetic logic unit (“ALU”) 1355, and multiple registers 1360 (shown as a group of registers in FIG. 16 ), and is implemented using a known computer architecture such as a modified Harvard architecture, a von Neumann architecture, or the like. The processing unit 1330, memory 1335, input unit 1340, and output unit 1345, as well as the various modules connected to the electronic processor 1300, are connected by one or more control and / or data buses (e.g., common bus 1365), which are shown generally in FIG. 16 for purposes of illustration. The use of one or more control and / or data buses for interconnection and communication between the various modules and components will be apparent to those skilled in the art upon review of the invention described herein.

[0083] The memory 1335 includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include a combination of different types of memory, such as read-only memory (“ROM”), random-access memory (“RAM”) (e.g., dynamic RAM [“DRAM”], synchronous DRAM [“SDRAM”], etc.), electrically erasable programmable read-only memory (“EEPROM”), flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory device. The processing unit 1330 is coupled to the memory 1335 and executes software instructions, which may be stored in the RAM of the memory 1335 (e.g., during execution), in the ROM of the memory 1335 (e.g., on a generally persistent basis), or in another memory or another non-transitory computer-readable medium, such as a disk. Software included in implementations of the battery pack chargers 1000, 1100, 1200 may be stored in the memory 1335 of the electronic processor 1300. Software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. Electronic processor 1300 is configured to retrieve and execute instructions from memory, particularly those related to controlling the battery pack described herein. Electronic processor 1300 may also store various battery pack parameters and characteristics (including the battery pack's nominal voltage, chemistry, battery cell characteristics, maximum allowable discharge current, maximum allowable temperature, etc.). In other configurations, electronic processor 1300 includes additional components, fewer components, or different components.

[0084] The device interface 1315 includes a combination of mechanical components (e.g., support 1010, 1210) and electrical components (e.g., terminals 1020, 1220) configured and operable to interface (e.g., mechanically, electrically, and communicatively connect) the battery pack with an electrical device (e.g., power tool 100, 500, 900, work site lighting system 800, etc.). For example, power provided from the battery pack 1000, 1100, 1200 to one of the electrical devices is provided to the device interface 1315 via a charge / discharge control module 1325. The charge / discharge control module 1325 includes, for example, one or more switches (e.g., FETs) for controlling charging current to and discharging current from the battery cells 1320. The device interface 1315 also includes a communication line 1370 for providing a communication line or link between, for example, the electronic processor 1300 and the electrical device.

[0085] The sensors 1310 include, for example, one or more voltage sensors, one or more temperature sensors, etc. For example, the electronic processor 1300 may use the sensors 1310 to monitor the individual charge state of each of the battery cells 1320, monitor the temperature of one or more of the battery cells 1320, etc. for a fault condition interrupt. If the voltage of one of the battery cells 1320 equals or exceeds an upper voltage limit (e.g., a maximum charging voltage), the charge / discharge control module 1325 prevents the battery cell from being further charged or requests a battery charger (not shown) to provide a constant voltage charging scheme. Alternatively, if one of the battery cells 1320 falls below a lower voltage limit, the charge / discharge control module prevents the battery cell 1320 from being further discharged. Similarly, if an upper or lower operating temperature limit of a battery cell 1320 of a battery pack is reached, the electronic processor 1300 may control the charge / discharge module 1325 to prevent charging or discharging until the temperature of the battery cell 1320 or the battery pack is within an acceptable temperature range. Additional fault condition interrupts may be implemented within the battery pack and are known to those skilled in the art. Fuel gauge 1305 includes one or more indicators, such as, for example, light emitting diodes ("LEDs"). Fuel gauge 1305 may be configured to display the status of, or information related to, the state of charge of battery cells 1320.

[0086] FIG. 17 shows a simplified block diagram of the battery packs 1000, 1100, 1200 showing the charge / discharge module 1325 in further detail, according to one exemplary embodiment. In the example shown in FIG. 17, the battery packs 1000, 1100, 1200 use current-sensing power MOSFET(s) 1400 to enable and disable charging and / or discharging. The drain of the FET 1400 is coupled to the battery cell 1320, and the source of the FET 1400 is coupled to ground. A bias resistor 1410 is coupled between the current-sensing terminal of the FET 1400 and ground. A junction 1420 between the current-sensing terminal of the FET 1400 and the bias resistor 1410 is connected to the electronic processor 1300. The internal resistance of the FET 1400 and the bias resistor 1410 act as a voltage divider to provide a voltage signal to the electronic processor 1300. The electronic processor 1300 includes an analog-to-digital converter (ADC) 1430 that receives the voltage signal from node 1420. The ADC 1430 converts the analog voltage signal received from node 1420 to a digital equivalent. The electronic processor 1300 uses the digital equivalent to determine the current. FIG. 17 shows only one exemplary configuration of the charge / discharge module 1325. The charge / discharge module 1325 may have other configurations and may include additional power MOSFETs and / or current-sensing power MOSFETs. For example, the FET 1400 may be located between the positive battery terminal and the device interface 1315, separate charge and discharge FETs may be included rather than a single FET, etc.

[0087] Current sensing is not typically done in battery packs like the one described above. Adding a current sensing resistor to a battery pack reduces the power efficiency of the battery pack. In contrast, using a charge / discharge FET to sense the current allows the battery pack to maintain the same power efficiency.

[0088] Accordingly, the embodiments described herein provide, among other things, current sensing in power tool devices using field effect transistors. Various features and advantages are set forth in the following claims.

Claims

1. A power tool device, comprising: Housing and A power supply interface; a field effect transistor within the housing connected between the power interface and a load of the power tool device; an inverter circuit coupled between the power supply interface and the load, the field effect transistor being a component of the inverter circuit; a bias resistor coupled between the current sense terminal of the field effect transistor and ground, the connection point between the current sense terminal and the bias resistor being used to measure a voltage; an electronic processor connected to the field effect transistor, the electronic processor comprising: controlling the field effect transistor to drive the load; measuring a voltage at the current sense terminal of the field effect transistor; determining a current flowing through the field effect transistor at the current sense terminal based on the voltage at the current sense terminal without using a shunt resistor. It is configured as follows: Power tool device.

2. The power tool device of claim 1 , wherein the field effect transistor is a low-side field effect transistor of the inverter circuit.

3. The power tool device of claim 1 , wherein the field effect transistor is a high-side field effect transistor of the inverter circuit.

4. The power tool device of claim 1 , further comprising an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

5. the power tool device is a demolition hammer; the housing includes a tool holder configured to receive a chisel; The power tool device of claim 1 .

6. The power tool device of claim 1 , wherein the power tool device is a chainsaw.

7. Housing and a motor within the housing; an inverter circuit within the housing coupled between a power interface and the motor, a plurality of high-side field effect transistors (FETs) coupled between a positive power terminal of the power interface and the motor; a plurality of low-side FETs coupled between the motor and a negative power terminal of the power interface; a bias resistor coupled between a source terminal of each of the plurality of high-side FETs and the plurality of low-side FETs and ground, a connection point between each source terminal and the bias resistor being used to measure a voltage; an inverter circuit; an electronic processor coupled to the plurality of high-side FETs and the plurality of low-side FETs, activating a first pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a first phase of the motor; measuring a first current flowing through the motor using a first activation FET in response to the first phase of the motor being activated; measuring a first voltage at a first source terminal of the first activation FET; determining the first current based on the first voltage; activating a second pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a second phase of the motor; measuring a second current flowing through the motor using a second activation FET in response to the second phase of the motor being activated; activating a third pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a third phase of the motor; measuring a third current flowing through the motor using a third activation FET in response to the third phase of the motor being activated; It was configured as follows: an electronic processor; Power tools.

8. The power tool of claim 7 , wherein the first activation FET is one of the plurality of low-side FETs.

9. The power tool of claim 7 , wherein the first activation FET is one of the plurality of high-side FETs.

10. The electronic processor measuring a second voltage at a second source terminal of the second activation FET; and determining the second current based on the second voltage. The power tool according to claim 7.

11. The electronic processor measuring a third voltage at a third source terminal of the third activation FET; and determining the third current based on the third voltage. The power tool according to claim 7.

12. 1. A work site lighting device, comprising: Housing and A power supply interface; a field effect transistor (FET) within the housing connected between the power interface and a load of the worksite lighting device; a bias resistor coupled between the current sense terminal of the FET and ground, the connection point between the current sense terminal and the bias resistor being used to measure a voltage; an electronic processor coupled to the FET, controlling the FET to drive the load; measuring a voltage at the current sense terminal of the FET; determining a current flowing through the FET at the current sense terminal based on the voltage. an electronic processor; Work site lighting equipment.

13. 13. The worksite lighting device of claim 12, further comprising an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

14. 1. A work site lighting device, comprising: Housing and A power supply interface; A battery pack and a charging field effect transistor (FET) within the housing connected between the power interface and the battery pack; a bias resistor coupled between a current sense terminal of the charge FET and ground, the connection point between the current sense terminal and the bias resistor being used to measure voltage; an electronic processor coupled to the charge FET, Controlling the charging FET to charge the battery pack; measuring the voltage at the current sense terminal of the charge FET; determining a current flowing through the charge FET at the current sense terminal based on the voltage. an electronic processor; Work site lighting equipment.

15. 15. The worksite lighting device of claim 14, further comprising an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

16. A battery pack, Housing and a device interface on the housing; a charge / discharge field effect transistor (FET) within the housing connected between a plurality of battery cells and the device interface; a bias resistor coupled between a current sense terminal of the charge / discharge FET and ground, the connection point between the current sense terminal and the bias resistor being used to measure a voltage; an electronic processor coupled to the charge / discharge FET, Controlling the charge / discharge FET to charge / discharge the plurality of battery cells; measuring the voltage at the current sense terminal of the charge / discharge FET; determining a charge / discharge current through the charge / discharge FET at the current sense terminal based on the voltage. an electronic processor; Battery pack.

17. 17. The battery pack of claim 16, further comprising an analog-to-digital converter configured to receive the voltage and convert the voltage into a digital value for the electronic processor.

18. 1. A method for current sensing in a power tool, comprising: activating, using an electronic processor of the power tool, a first pair of a plurality of high-side field effect transistors (FETs) and a plurality of low-side FETs to activate a first phase of a motor, the plurality of high-side FETs and the plurality of low-side FETs being disposed in an inverter bridge of the power tool connected between a power interface and the motor of the power tool; measuring a first current flowing through the motor using a first activation FET at a bias resistor coupled between a first source terminal of the first activation FET and ground in response to the first phase of the motor being activated, the connection point between the first source terminal and the bias resistor being used to measure a voltage; activating a second pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a second phase of the motor; measuring a second current flowing through the motor using a second activation FET at a bias resistor coupled between a second source terminal of the second activation FET and ground in response to the second phase of the motor being activated, the connection point between the second source terminal and the bias resistor being used to measure a voltage; activating a third pair of the plurality of high-side FETs and the plurality of low-side FETs to activate a third phase of the motor; measuring a third current flowing through the motor using a third activation FET at a bias resistor coupled between a third source terminal of the third activation FET and ground in response to the third phase of the motor being activated, the connection point between the third source terminal and the bias resistor being used to measure a voltage. method.

19. measuring a first voltage at a first source terminal of the first activation FET; determining the first current based on the first voltage.

20. The method of claim 18.

20. measuring a second voltage at a second source terminal of the second activation FET; determining the second current based on the second voltage.

20. The method of claim 19.

21. measuring a third voltage at a third source terminal of the third activation FET; determining the third current based on the third voltage.

21. The method of claim 20.

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