Power tool including low quiescent current DC link bus discharge circuit

Abstract

A power tool apparatus is disclosed, the power tool apparatus comprising: a housing; a battery pack interface configured to receive at least one battery pack; a first battery pack terminal and a second battery pack terminal; a low quiescent current direct current ("DC") link bus discharge circuit, the low quiescent current direct current link bus discharge circuit including a DC link bus capacitor, a first DC link bus switch, and a second DC link bus switch; and a controller. The controller is configured to: monitor a voltage of the first battery pack terminal; monitoring the voltage of the second battery pack terminal; when the voltage of the first battery pack terminal is greater than a first threshold and the voltage of the second battery pack terminal is zero volt, the first DC link bus switch and the second DC link bus switch are turned on.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 227,469, filed on July 30, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments described herein provide a battery-powered device. Utility Model Content

[0004] Embodiments described herein provide systems and methods that allow safe access to battery pack terminals after the battery pack has been disconnected from a power tool.

[0005] The power tool device described herein includes: a housing; a battery pack interface configured to receive at least one battery pack; a first battery pack terminal and a second battery pack terminal; a low quiescent current direct current ("DC") link bus discharge circuit, the low quiescent current DC link bus discharge circuit including a DC link bus capacitor, a first DC link bus switch and a second DC link bus switch; and a controller. The controller is configured to: monitor the voltage of the first battery pack terminal; monitor the voltage of the second battery pack terminal; when the voltage of the first battery pack terminal is greater than a first threshold and the voltage of the second battery pack terminal is zero volts, turn on the first DC link bus switch and the second DC link bus switch.

[0006] In some aspects, the power tool apparatus further includes a third DC link bus switch connected to the first DC link bus switch.

[0007] In some aspects, the controller is configured to enable the third DC link bus switch when the voltage of the second terminal is greater than a battery pack present voltage threshold.

[0008] In some aspects, the battery pack presents a voltage threshold of 18V or less.

[0009] In some aspects, the first DC link bus switch is disabled when the voltage of the first battery pack terminal is greater than the first threshold and the voltage of the second battery pack terminal is greater than a second threshold.

[0010] In some aspects, the at least one battery pack includes a first battery pack and a second battery pack.

[0011] In some aspects, the first threshold is between 18V and 36V.

[0012] In some aspects, the first threshold is 25V.

[0013] The power tool device described herein includes: a housing; a battery pack interface configured to receive at least one battery pack; a low static direct current ("DC") link bus discharge circuit, the low static DC link bus discharge circuit including a discharge resistor and a discharge switch; and a controller. The controller is configured to: determine when the power tool device is not in operation; implement a delay interval after determining that the power tool device is not in operation; after the delay interval ends, enable the discharge switch to discharge the voltage stored on the DC link bus through the discharge resistor.

[0014] In some aspects, the controller is configured to provide an on command to the controller pin after the delay interval has expired.

[0015] In some aspects, the power tool device is configured to disconnect the battery pack interface from the DC link capacitor using a solid-state disconnect circuit.

[0016] In some aspects, the controller is configured to determine a safe handling state of the power tool equipment.

[0017] The method for controlling a power tool device described in this article includes: monitoring the voltage of a first battery pack terminal; monitoring the voltage of a second battery pack terminal; and enabling a first DC link bus switch and a second DC link bus switch when the voltage of the first battery pack terminal is greater than a first threshold and the voltage of the second battery pack terminal is zero volts.

[0018] In some aspects, the methods further include enabling a third DC link bus switch when the voltage of the second terminal is greater than a battery pack present voltage threshold.

[0019] In some aspects, the battery pack presents a voltage threshold of 18V or less.

[0020] In some aspects, the methods further include deactivating the first DC link bus switch when the voltage of the first battery pack terminal is greater than the first threshold and the voltage of the second battery pack terminal is greater than a second threshold.

[0021] In some aspects, the first threshold is between 18V and 36V.

[0022] In some aspects, the first threshold is 25V.

[0023] In some aspects, the methods further include determining a safe operating state of the power tool equipment.

[0024] In some aspects, the methods further include connecting the first battery pack terminal to a first battery pack, and connecting the second battery pack terminal to a second battery pack.

[0025] Before explaining any embodiment in detail, it should be understood that the embodiment does not limit its application to the details of the configuration and arrangement of components set forth in the following description or shown in the accompanying drawings. The embodiments can be practiced or executed in various ways. It is also to be understood that the words and terms used herein are for illustrative purposes and should not be considered restrictive. The use of "including", "comprising" or "having" and variations thereof is intended to cover the items listed thereafter and their equivalents, as well as additional items. Unless otherwise specified or limited, the terms "mount", "connect", "support" and "couple", and variations thereof are used extensively and cover both direct mounting, connection, support and coupling as well as indirect mounting, connection, support and coupling.

[0026] In addition, it should be understood that embodiments may include hardware, software, and electronic components or modules, which, for the purpose of discussion, may be shown and described as if most components are implemented only in hardware. However, those of ordinary skill in the art will recognize, based on reading this detailed description, that in at least one embodiment, electronic-based aspects may be implemented in software (e.g., stored on a non-transitory computer-readable medium) that may be executed by one or more processing units (such as a microprocessor and / or an application-specific integrated circuit (“ASIC”)). Thus, it should be noted that embodiments may be implemented using multiple hardware- and software-based devices and multiple different structural components. For example, the “server,” “computing device,” “controller,” “processor,” etc. described in the specification may include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connectors (e.g., a system bus) connecting these components.

[0027] Relative terms used in conjunction with quantities or conditions, such as "about", "approximately", "substantially", etc., will be understood by those of ordinary skill in the art to include the stated value and have the meaning dictated by the context (e.g., the term includes at least the degree of error associated with measurement accuracy, the tolerance associated with a particular value [e.g., manufacturing, assembly, use, etc.], etc.). Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression "from about 2 to about 4" also discloses a range "from 2 to 4". Relative terms can refer to positive and negative percentages (e.g., 1%, 5%, 10%, or more) of the indicated value.

[0028] It should be understood that although some drawings show the hardware and software in a particular device, these depictions are for illustrative purposes only. The function described herein as being performed by a component can be performed in a distributed manner by multiple components. Likewise, the function performed by multiple components can be merged and performed by a single component. In some embodiments, the components shown can be combined or divided into separate software, firmware and / or hardware. For example, logic and processing can be distributed between multiple electronic processors, rather than being located in a single electronic processor and performed by it. Regardless of how hardware components and software components are combined or divided, these hardware components and software components can be located on the same computing device or can be distributed between different computing devices connected by one or more networks or other suitable communication links. Similarly, the components described as performing a specific function can also perform additional functions not described herein. For example, a device or structure that is "configured" in a certain way is configured at least in this way, but can also be configured in a way that is not explicitly listed.

[0029] Other aspects of the embodiments will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Multiple battery packs were shown that could be used with various devices.

[0031] Figure 2 A simplified block diagram of a power tool device is shown.

[0032] Figure 3 Shows the configuration to control Figure 2 An embodiment of a portion of an inverter bridge of a power tool device.

[0033] Figure 4 Shown Figure 2 Battery terminal block for power tool equipment.

[0034] Figure 5A and Figure 5B Demonstrated for use with Figure 2 Different sized battery packs for use with power tool equipment.

[0035] Figure 6 Demonstrated for Figure 5A and Figure 5B The battery pack terminal block of the battery pack.

[0036] Figure 7 yes Figure 5A and Figure 5B Simplified block diagram of a battery pack.

[0037] Figure 8 A low quiescent current capacitor discharge circuit is demonstrated.

[0038] Fig. 9 Demonstrated the use of Figure 8 A method for implementing a capacitor control system.

[0039] Fig.10 A solid-state disconnect circuit is demonstrated.

[0040] Fig.11 Demonstrated the use of Fig.10 A method for implementing a solid-state disconnect circuit. DETAILED DESCRIPTION

[0041] Figure 1 A high power electrical system is shown to which a plurality of battery packs 10, 10A may be attached. The high power electrical system includes various high power electrical devices capable of receiving and utilizing a plurality of battery packs and then using a static circuit to allow the capacitors to discharge. For example, the high power electrical system includes handheld devices (i.e., devices configured to be supported by an operator during use) and non-handheld devices (i.e., devices supported on a work surface or support rather than by an operator during use). Such equipment includes powered power tools (e.g., drills, impact drivers, impact wrenches, rotary hammers, hammer drills, saws [circular saws, cut-off saws 100, reciprocating saws, miter saws 105, table saws 120, etc.], core drills 130, breakers 115, demolition hammer compressors 110, pumps, etc.), outdoor tools (e.g., chainsaws 125, rope hammers, pruning shears, blowers, lawn mowers, etc.), drain cleaning and plumbing tools, construction tools, concrete tools, other powered equipment (e.g., vehicles, carts, wheeled and / or self-propelled tools, etc.), etc., as well as non-powered electrical equipment (e.g., power supplies 145, lights 135, AC / DC adapters 140, generators, etc.).

[0042] Figure 2 A simplified block diagram of an embodiment is shown, which shows an electronic assembly 275 and a motor assembly 210 of a power tool or power tool device 200. The electronic assembly 275 includes a circuit system of several embodiments coupled to circuits that allow low quiescent current and safe discharge of capacitors. The electronic assembly 275 includes a positive power input terminal 260, a negative power input terminal 270, a first controller 245, a second controller 240, an inverter bridge 225, and a trigger assembly 230. The motor assembly 210 includes a motor 215 and a rotor position sensor assembly 220. The electronic assembly 275 may also include additional user inputs, such as a mode selector switch, a speed dial, a clutch setting unit, etc. In some embodiments, in addition to or instead of the trigger assembly 230, the electronic assembly 275 may include a power switch.

[0043] The functions of the implemented circuit can be divided between the first controller 245 and the second controller 240. For example, the first controller 245 can be the main controller of the system, while the second controller 240 is an application controller that controls one or more applications of the implemented circuit. In some embodiments, the second controller 240 can be a motor controller that controls the operation of the inverter bridge 225 and the motor 215, and the first controller 245 can be the main controller that performs other functions of the implemented circuit. By distributing the functional load of the high-capacity and high-power implemented circuit, and by explicitly separating the motor control function from the first controller 245, the thermal load is distributed between the first controller 245 and the second controller 240. This thermal distribution thereby reduces the thermal characteristics of the implemented circuit.

[0044] In some embodiments, the first controller 245 and / or the second controller 240 are implemented as microprocessors with separate memory. In other embodiments, the first controller 245 and / or the second controller 240 may be implemented as microcontrollers (with memory on the same chip). In other embodiments, the first controller 245 and / or the second controller 240 may be partially or completely implemented as, for example, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a hardware-implemented state machine, etc., and memory may not be required or may be modified accordingly.

[0045] In some embodiments, the second controller 240 and the motor assembly 210 can be part of a single motor package. Such a motor package provides modularity for future applications. For example, multiple motor packages each including a motor assembly 210 and a second controller 240 can be assembled in the implemented circuit and controlled by a single first controller 245.

[0046] A communication protocol may be implemented between the first controller 245 and the second controller 240 to maintain uninterrupted operation of the implemented circuit. In one example, the first controller 245 and the second controller 240 may communicate via a communication bus 235, such as a serial peripheral interface (SPI) bus. The first controller 245 and the second controller 240 may be configured such that the first controller 245 and the second controller 240 exchange communications at certain time intervals. The time interval may be, for example, between 3 milliseconds (ms) and 15 ms. The first controller 245 may also communicate with the battery pack controller via a communication link 265.

[0047] As described above, in some embodiments, the second controller 240 controls the operation of the motor 215 through the inverter bridge 225. The first controller 245 is communicatively coupled to the trigger assembly 230. The trigger assembly 230 may include, for example, a potentiometer, a distance sensor, etc., to determine the distance the trigger is pulled and provide an indication of the distance to the first controller 245. The first controller 245 reads and processes the trigger information and provides the trigger information to the second controller 240. The second controller 240 is communicatively coupled to the rotor position sensor assembly 220. As described above, the rotor position sensor assembly 220 provides the absolute rotational position of the rotor and / or the rotational speed of the rotor. The second controller 240 performs open-loop or closed-loop control of the motor 215 through the inverter bridge 225 based on the signal (e.g., trigger information) received from the first controller 245 and the signal received from the rotor position sensor assembly 220. In some embodiments, the first controller 245 and the second controller 240 are communicatively coupled to the rotor position sensor assembly 220 to provide redundancy for monitoring the rotational speed.

[0048] Figure 3 An embodiment 300 of a portion of an inverter bridge 225 is shown that controls the supply of power to three phases (e.g., U, V, and W) of a motor 215 of a power tool device 200. The inverter bridge 300 includes a gate driver 305, a high-side FET 310, and a low-side FET 315 for each phase of the motor 215. The high-side FET 310 and the low-side FET 315 are controlled by the corresponding gate drivers 305.

[0049] In some embodiments, the inverter bridge 300 may include more than one high-side FET 310 and more than one low-side FET 315 per phase to provide redundant current paths for each phase. Figure 3 Only one set of gate drivers 305 , high-side FETs 310 , and low-side FETs 315 are shown, but the inverter bridge 300 includes three sets of gate drivers 305 , high-side FETs 310 , and low-side FETs 315 , one set for each phase of the motor 215 .

[0050] The high-side FET 310 receives the battery power supply at the drain of the high-side FET 310. The source of the high-side FET 310 is connected to the motor 215 (e.g., a phase coil of the motor 215) to provide the battery power supply to the motor 215 when the high-side FET 310 is closed. In other words, the high-side FET 310 is connected between the battery power supply and the motor phase coil.

[0051] The drain of the low-side FET 315 is connected to the motor 215 (e.g., the phase coil of the motor 215), and the source of the low-side FET 315 is connected to the ground. In other words, the low-side FET 315 is connected between the motor phase coil and the ground. The low-side FET 315 provides a current path between the motor phase coil and the ground when closed.

[0052] When the FETs 310, 315 are closed (or turned on), the FETs 310, 315 allow current to flow through the phase coil. Conversely, when the FETs 310, 315 are open (or turned off), the FETs 310, 315 prevent current from flowing through the phase coil. The FETs 310, 315 are characterized by a relatively high drain-source breakdown voltage (e.g., between 120V and 220V), a relatively high drain continuous current (e.g., between 50A and 90A), a relatively high drain pulse current (e.g., in excess of 300A), and a drain-source on-state resistance (R) of less than 15mΩ. DS(on) ).

[0053] In contrast, the FETs used in existing power tool devices are not graded for such high voltage and current characteristics. Therefore, existing power tool devices will not be able to handle such high current and voltage characteristics.

[0054] The gate driver 305 provides a gate voltage to the FETs 310, 315 to control whether the FETs 310, 315 are opened or closed. The gate driver 305 receives an operating power supply (e.g., a low voltage power supply) from the battery pack 10, 10A. The gate driver 305 also receives a control signal from the second controller 240 (one for each of the high-side current path and the low-side current path). The gate driver 305 provides a gate control voltage (e.g., from a low voltage power supply) to the FETs 310, 315 based on the control signal received from the second controller 240.

[0055] In some embodiments, the second controller 240 and the gate driver 305 may control only the low-side FET 315 to operate the motor 215. In other embodiments, the second controller 240 and the gate driver 305 may control only the high-side FET 310 to operate the motor 215. In other embodiments, the second controller 240 and the gate driver 305 alternate between controlling the high-side FET 310 and controlling the low-side FET 315 to operate the motor 215 and distribute the heat load between the FETs 310, 315.

[0056] In some embodiments, the inverter bridge 300 may further include a current sensor disposed in the current path to detect current flowing to the motor 215. The output of the current sensor is provided to the second controller 240. The second controller 240 may further control the motor 215 based on the output of the current sensor.

[0057] Reference Figure 2 , the discharge switch 255 is provided on the current path between the power supply terminal of the implemented circuit and the inverter bridge 300. The discharge switch 255 can be implemented using, for example, a metal oxide semiconductor field effect transistor (MOSFET). When the discharge switch 255 is turned off, the current flow stops between the power supply terminal and the inverter bridge 300.

[0058] The discharge controller 250 controls the discharge switch 255 (i.e., opens and closes the discharge switch 255). The discharge controller 250 may be a logic circuit, a hardware-implemented state machine, an electronic processor, etc. The discharge controller 250 receives inputs from the first controller 245, the second controller 240, and the trigger and provides a control signal to the discharge switch 255. The discharge controller 250 may also provide a state indication to the first controller 245 indicating whether the discharge switch 255 is open or closed.

[0059] In addition to the primary embodiment including the low quiescent current circuit, several techniques for implementing the discharge control scheme of the power tool device 200 using the discharge switch 255 are also contemplated. In one example, the discharge controller 250 can be an AND gate that implements a logic system using inputs from the first controller 245, the second controller 240, and the trigger assembly 230. The discharge controller 250 can close the discharge switch 255 only when the trigger, the first controller 245, and the second controller 240 provide a control signal to close the discharge switch 255.

[0060] In some embodiments, it may be desirable to close the discharge switch 255 to operate the motor 34 when the trigger is operated and the first controller 245 and the second controller 240 are ready to operate. In these embodiments, the discharge controller 250 may close the discharge switch 255 according to the trigger, the first controller 245, and the second controller 240. Thus, when one of the first controller 245 and the second controller 240 generates an interrupt due to a detected problem, or when the trigger is released, the discharge controller 250 opens the discharge switch 255 to prevent current from flowing to the inverter bridge 300. In some embodiments, when the first controller 245 or the second controller 240 detects an overvoltage condition, an overcurrent condition, an overheat condition, etc., the first controller 245 or the second controller 240 may generate or terminate a signal to the discharge controller 250 to open the discharge switch 255.

[0061] Figure 4 A tool terminal block 400 is shown that includes a positive power terminal 425, a ground terminal 435, a low power terminal 430, a positive transmission terminal 405, a negative transmission terminal 410, a positive receiver terminal 420, and a negative receiver terminal 415. The positive power terminal 425 and the ground terminal 435 are connected to the power terminals (i.e., the positive battery terminal and the ground terminal) of the battery pack 10, 10A to receive the main discharge current for the operation of the implemented circuit. The low power terminal 430 receives a low power voltage supply from the low power terminal of the battery pack 10, 10A to power certain functions of the tool.

[0062] The positive transmission terminal 405, the negative transmission terminal 410, the positive receiver terminal 420, and the negative receiver terminal 415 may be collectively referred to as the "communication terminals" of the implemented circuit. The communication terminals allow differential communication between the battery pack 10, 10A and the power tool device 200. In other embodiments, the tool communication terminals follow a full-duplex standard (e.g., the RS485 standard).

[0063] Return to reference Figure 2 , the positive power supply terminal 425 and the ground terminal 435 are electrically coupled to the inverter bridge 225 and provide a current path to operate the motor 215. The communication terminals (i.e., the positive transmission terminal 405, the negative transmission terminal 410, the positive receiver terminal 420, and the negative receiver terminal 415) can be coupled to the first controller 245, for example, through a power tool device transceiver. The communication terminals provide a communication link 265 between the first controller 245 and the battery pack controller.

[0064] Figure 5A An embodiment of a battery pack 500A is shown. The battery pack 500A includes a housing 505A, a user interface portion 510A for providing a charge status indication for the battery pack 500A, and a device interface portion 515A for connecting the battery pack 500A to a device (e.g., a power tool). The battery pack 500A includes a plurality of battery cells within the housing 505A.

[0065] Figure 5B Another embodiment of a battery pack 500B is shown. The battery pack 500B includes a battery housing 530 including a wall having an inner surface and an outer surface. The inner surface defines an internal cavity. The outer surface includes a top surface portion 515B and a bottom portion. The battery cells disposed within the cavity are connected in series to battery contacts 505B. Contacts 505B are disposed on the top surface portion 515B within a battery contact housing extension 510B. The housing extension 510B is configured to engage in a mating manner with one or more power tools or power accessories. A battery charge level indicator 520 is also disposed on the housing, and additional battery charging, monitoring and indication components are disposed within the cavity. As shown in FIG. Figure 5BAs shown, two tabs 535 are coupled to the housing 530 for releasably securing the housing 530 to the power tool. Features corresponding to those described above with respect to the battery pack 500A may also be included in the battery pack 500B.

[0066] Figure 6 A battery terminal block 600 is shown for interfacing with the tool terminal block 400 of the power tool device 200. The battery terminal block 600 is operable to electrically connect the battery pack 10, 10A and the power tool device 200, and as shown, includes a positive battery terminal 640, a ground terminal 630, a charger terminal 635, a low power terminal 625, a positive transmission terminal 605, a negative transmission terminal 610, a positive receiver terminal 620, and a negative receiver terminal 615. The positive battery terminal 640 and the ground terminal 630 are connectable to the power terminals (i.e., the positive power terminal 425 and the ground terminal 435) of the power tool device 200. The charger terminal 635 and the ground terminal 630 are connected to the charging terminals of the charger and receive a charging current to charge the battery cells of the battery pack 10. In some embodiments, the battery pack terminals 630, 640 may be made of F-Tec material (copper, phosphorus material) to provide battery heat distribution capabilities and durability.

[0067] The ground terminal 630 may form a common reference between the battery pack 10, 10A and the power tool device 200. The low power terminal 625 provides a low power voltage supply to the power tool device 200 to power certain functions of the power tool device 200. For example, the low power voltage supply may be used to power the first controller 245, the second controller 240, the gate driver 305, indicators (e.g., LEDs), a communication module, etc. of the power tool device 200.

[0068] The positive transmission terminal 605, the negative transmission terminal 610, the positive receiver terminal 620, and the negative receiver terminal 615 may be collectively referred to as the "battery communication terminals" of the battery pack 10, 10A. The battery communication terminals allow differential communication between the battery pack 10 and the power tool device 200 or the charger. The battery communication terminals and the communication terminals of the power tool device 200 may be collectively referred to as the communication link 265. In other embodiments, the communication terminals follow a full-duplex standard (e.g., the RS485 standard).

[0069] Figure 7 7 is a simplified block diagram of the battery pack 10, 10A. The battery pack 10, 10A includes a battery cell 755, a battery controller 760, a low power generator 725, and a battery transceiver 765. The battery controller 760 may be implemented in a manner similar to the first controller 245 and the second controller 240.

[0070] In some embodiments, the battery discharge switch 715 is connected between the battery cell 755 and the positive battery terminal 730. The battery controller 760 is operable to control (e.g., open and close) the discharge switch 715 to control the discharge of the battery cell 755. In some embodiments, the charging switch 710 may also be connected between the battery cell 755 and the charger terminal 705. The battery controller 760 is operable to control (e.g., open and close) the charging switch 710 to control the charging of the battery cell 755. In some embodiments, when the discharge switch 715 and the charging switch 710 are implemented using MOSFETs, two MOSFETs in series can be used as the discharge switch 715 and the charging switch 710. This allows the discharge switch 715 and the charging switch 710 to prevent any current from flowing in either direction when the discharge switch 715 and the charging switch 710 are open.

[0071] The discharge switch 715 and the charge switch 710 may be implemented using bipolar junction transistors, field effect transistors (FETs), etc. In some embodiments, the discharge switch and the charge switch 710 may be connected between the battery cell 755 and the ground terminal 790 on the ground side of the battery cell 755. In some embodiments, the ground terminal 790 may be divided into a charge path ground terminal and a discharge path ground terminal.

[0072] The low power generator 725 is connected between the battery cell 755 and the low power terminal 720. The low power generator 725 provides a low power voltage supply to the power tool device 200 at the low power terminal 720. In some embodiments, the battery controller 760 can provide control signals to the low power generator 725 to control the operation of the low power generator 725.

[0073] In the illustrated example, the battery transceiver 765 is implemented as a differential communication transceiver (eg, a Texas Instruments SN65HVD7 full-duplex RS-485 transceiver). The battery transceiver 765 receives the transmission signal 735 from the battery controller 760 and sends the receiver signal 750 to the battery controller 760.

[0074] The battery transceiver 765 is also connected to the communication terminals (770, 775, 780 and 785). When the battery pack 10 transmits a communication signal to the power tool device 200 or the charger, in addition to the transmission enable signal 740, the battery controller 760 also sends the transmission enable signal 740 to the battery transceiver 765. When the battery transceiver 765 receives the transmission enable signal 740, the battery transceiver 765 converts the transmission signal 735 into a complementary transmission signal at the positive transmission terminal 770 and the negative transmission terminal 775. When the battery transceiver 765 receives the receiver enable signal 745 from the battery controller 760, the battery transceiver 765 receives the complementary signal from the positive receiver terminal 780 and receives the negative receiver terminal signal 750 to the battery controller 760. The power tool device 200 can similarly include a power tool device transceiver that interacts with the first controller 245 in a manner similar to providing communication with the battery controller 760.

[0075] In other embodiments, the battery pack 10 may include separate transmitting and receiving components (eg, a transmitter and a receiver) rather than the battery transceiver 765 .

[0076] The battery controller 760 communicates with the first controller 245 via a communication link 265 (e.g., an RS-485 link) through the battery terminals. The communication link 265 between the battery controller 760 and the first controller 245 can be used for authentication of the battery pack 10, 10A and the power tool device 200 or for exchanging other information (e.g., the discharge capacity of the battery pack 10, 10A). The first controller 245 and the battery controller 760 can be configured so that the first controller 245 and the battery controller 760 exchange communications at a certain time interval. The time interval can be, for example, between 3ms and 15ms.

[0077] Figure 8A low quiescent current DC link bus discharge circuit 800 for a power tool 200 is shown. The circuit 800 includes a battery pack negative terminal 805 (e.g., connected to the lowest potential terminal of the battery packs 500A, 500B), an intermediate voltage terminal 810 (e.g., corresponding to the battery pack positive voltage of the first battery pack 500A, 500B), and a DC link bus terminal 815 (e.g., connected to the highest potential terminal of the battery packs 500A, 500B). When two battery packs are connected to the power tool 200, the DC link bus terminal 815 corresponds to the combined series voltage of the two battery packs (e.g., 36V-40V). When either battery pack is removed from its battery pack receiving interface of the power tool 200, the voltage of the DC link bus terminal can remain high if the DC link bus capacitor is charged. When the voltage at the DC link bus terminal 815 is greater than a first threshold value (e.g., 25V, between 18V and 36V, etc.) and the voltage at the intermediate voltage terminal is greater than a second threshold value (e.g., 18V, 10V-18V, etc.), the discharge transistor holding capacitor 820 is charged. The discharge transistor holding capacitor 820 can be charged to a DC link voltage value of, for example, 10V-15V. When the first battery pack 500A, 500B is attached to the power tool 200 or if the second battery pack 500A, 500B is attached to the power tool 200 and the discharge transistor holding capacitor 820 is charged, the voltage at the intermediate voltage terminal 810 will be greater than or approximately equal to the second threshold value.

[0078] Switches 825 and 830 (e.g., bipolar junction transistors, FETs, MOSFETs, etc.) are configured for asymmetric switching of a first DC link switch 835 and a second DC link switch 840. If the voltage of the intermediate voltage terminal 810 is greater than a battery pack presence voltage threshold (e.g., 10V) (which indicates that the first battery pack 500A, 500B is connected to the power tool 200), the second DC link switch 840 is turned on or enabled. In some embodiments, the first DC link switch 835 is a PMOS transistor and the second DC link switch 840 is an NMOS transistor. When the second DC link switch 840 is turned on, the DC link discharge switch 845 (e.g., bipolar junction transistors, FETs, MOSFETs, etc.) is turned off accordingly. In some embodiments, the DC link discharge switch 845 is an NMOS transistor. When the first battery pack 500A, 500B is removed from the power tool 200, the second DC link switch 840 is turned off.

[0079] The first DC link switch 835 being turned off or disabled ensures a low quiescent current (e.g., below a quiescent current threshold, such as less than or equal to 5 microamperes [“μA”]) for the power tool 200. If the voltage at the DC link terminal 815 is greater than a first threshold (e.g., greater than 25V) and the voltage at the intermediate voltage terminal 810 is zero (0) voltage, the first DC link switch 835 is turned on or enabled. This occurs when the DC link bus capacitor (not shown) is charged and both the first battery pack 500A and the second battery pack 500B are removed or unloaded from the power tool 200. In such an instance, with the first DC link switch 835 turned on and the second DC link switch 840 turned off (because the first battery packs 500A, 500B are removed), the DC link discharge switch 845 is turned on or enabled. When both the DC link discharge switch 845 and the first DC link switch 835 are turned on, the discharge transistor keeps the capacitor 820 discharged to ground. With the discharge transistor keeping the capacitor 820 discharged, there is no risk of, for example, a user contacting the battery pack receiving terminals of the power tool 200 (e.g., corresponding to the DC link bus terminals 815 and the intermediate voltage terminals 810) or of arcing or electric shock. Figure 8 , the DC link bus capacitance is illustratively shown as capacitor 850. Although only one capacitor 850 is shown to represent the DC link bus capacitance, capacitor 850 may represent an aggregation of capacitance on the DC link bus from multiple capacitors or other capacitance sources.

[0080] Fig. 9 A low quiescent current capacitor discharge method 900 is shown. The battery-powered power tool 200 may receive multiple (e.g., two) battery packs and may be turned on (step 905) by a user who initiates operation of the battery-powered power tool 200. This enables connection to a Figure 8 The battery pack of the circuit 800 is shown (step 910) to release current for powering the power tool 200. The terminals of the battery pack are electrically coupled to the terminals 805, 810, 815. Figure 8 The circuit 800 of the battery pack is switched on and the tool 200 powered by the battery pack monitors the DC link bus terminal 815 and the intermediate voltage terminal 810. Once the user has finished their task or operation using the power tool 200, the power tool operation is shut down (step 915), so there is no longer a need to transfer power from the battery pack to the power tool 200. As described above, the first DC link switch 835 being turned off ensures a low quiescent current for the power tool 200. Therefore, if the battery packs 500A, 500B remain attached to the power tool 200, the quiescent current drawn by the power tool 200 will be very low (e.g., less than 5 μA).

[0081] To ensure that the terminals of the power tool 200 are safe for the user to touch when the battery packs 500A, 500B are removed, the voltage of the DC link bus terminal 815 and the intermediate voltage terminal 810 (at Figure 8 ) (shown in and described with respect to that figure) (step 925) to detect whether one or both of these battery packs have been removed (i.e., unloaded) from the power tool 200. If the voltage at the DC link bus terminal 815 is above, for example, a first threshold (e.g., 25V) and the voltage at the intermediate voltage terminal 810 is greater than a second threshold (e.g., 18V), the controller 240, 245 can determine that two battery packs are connected to the power tool 200. If the high-side battery pack (e.g., corresponding to the highest potential terminal at the DC link bus) is removed from the power tool 200 while the discharge transistor holding capacitor 820 is charged (e.g., to 10V-15V) and the low-side battery pack is removed, the controller 240, 245 will measure a voltage at the DC link bus terminal 815 that is greater than the first threshold (e.g., 25V) and a voltage at the intermediate voltage terminal 810 that is zero (0) volts. In this case, the discharge transistor holding capacitor 820 is discharged through the DC link discharge switch 845 (step 930), as described above with respect to Figure 8 Once the discharge transistor keeps the capacitor 820 discharged, the battery pack terminals of the power tool 200 are safe to touch (step 935).

[0082] Fig.10 Another embodiment of a circuit for safely discharging a DC link capacitor or capacitance is presented. Fig.10A DC link capacitor discharge circuit 1000 is shown, which includes a discharge resistor 1005, a controller pin 1010 (e.g., from a controller 240, 245), and a discharge switch 1015 (e.g., a FET) for connecting the discharge resistor 1005 to ground 1020. When a battery pack (e.g., two battery packs) is connected to the power tool 200, the combined series voltage of the battery packs corresponds to the voltage of the DC link bus of the power tool 200. The positive end of the discharge resistor 1005 is connected to the DC link bus. During operation of the power tool 200, the battery pack is connected to the DC link bus via a solid-state disconnect circuit to provide power for driving the motor. However, when operation of the tool has ended, the solid-state disconnect circuit can be used to disconnect the battery pack voltage from the DC link bus. The voltage from the DC link capacitor can then be discharged through the DC link capacitor discharge circuit 1000. For example, after a predetermined time delay after the operation of the power tool 200 ends (e.g., after a sensed trigger release, after the motor has stopped rotating, etc.), the controller 240, 245 is configured to provide a turn-on signal to the controller pin 1010 to turn on the discharge switch 1015. After the discharge switch 1015 is turned on, the charge stored by the DC link capacitor for the DC link bus is discharged through the discharge resistor 1005. Since the discharge switch 1015 is off, the quiescent current drawn by the power tool 200 will be very low (e.g., less than 5 μA).

[0083] Fig.11 Demonstrated for Fig.10The control process 1100 of the circuit of the power tool 200 is described in detail. The user first connects multiple battery packs 500A, 500B to the power tool 200 (step 1105), and then turns on the power tool 200 (step 1110). By turning on the power tool 200, the battery pack is enabled (step 1110) and power is provided to the motor of the power tool 200. In operation, a solid-state disconnect circuit (e.g., a main power tool power switch) connects the battery pack voltage to the DC link bus to allow the motor of the power tool 200 to be driven. Once the user has completed the work using the power tool, the power tool operation is shut down (step 1115), thereby stopping the motor of the power tool 200. The power tool operation can be stopped by a variety of different methods and / or systems (e.g., releasing a trigger, a predetermined stop control, etc.). Then, the battery pack voltage is disconnected from the DC link capacitor using a solid-state disconnect circuit (step 1120). After the battery pack voltage is disconnected from the DC link bus and the DC link bus capacitor, a delay interval or period is set in the controller 240, 245 (step 1125). At the end of the delay interval or period, the controller 240, 245 provides an on command to the controller pin 1010 (step 1130) to discharge the voltage of the DC link capacitor through the discharge resistor 1005 (step 1135). Once the DC link capacitor is discharged, the battery pack terminals of the power tool 200 are safe to touch (step 1140).

[0084] Thus, the embodiments described herein provide, among other things, systems and methods for discharging a DC link bus capacitor to ensure safe access to battery terminals. Various features and advantages are set forth in the appended claims.

Claims

1. A power tool device, comprising: case; a battery pack interface configured to receive at least one battery pack; a first battery terminal and a second battery terminal; a low quiescent current direct current ("DC") link bus discharge circuit, the low quiescent current DC link bus discharge circuit comprising a DC link bus capacitor, a first DC link bus switch, and a second DC link bus switch; as well as A controller configured to: monitoring the voltage of the first battery terminal, monitoring the voltage of the second battery terminal, The first DC link bus switch and the second DC link bus switch are enabled when the voltage of the first battery pack terminal is greater than a first threshold and the voltage of the second battery pack terminal is zero volts. 2 . The power tool apparatus of claim 1 , further comprising a third DC link bus switch connected to the first DC link bus switch.

3. The power tool device according to claim 2, wherein: The controller is configured to enable the third DC link bus switch when the voltage of the second terminal is greater than a battery pack present voltage threshold.

4. The power tool device according to claim 3, wherein: The battery pack has a voltage threshold of 18 V or less.

5. The power tool device according to claim 1, wherein: The first DC link bus switch is disabled when the voltage of the first battery pack terminal is greater than the first threshold and the voltage of the second battery pack terminal is greater than a second threshold.

6. The power tool device according to claim 1, wherein: The at least one battery pack includes a first battery pack and a second battery pack.

7. The power tool device according to claim 6, wherein: The first threshold is between 18V and 36V.

8. The power tool device according to claim 7, wherein: The first threshold is 25V.

9. A power tool device, comprising: case; a battery pack interface configured to receive at least one battery pack; a low quiescent current direct current ("DC") link bus discharge circuit, the low quiescent current DC link bus discharge circuit comprising a discharge resistor and a discharge switch; as well as A controller configured to: Determine when the power tool equipment is not in operation, implementing a delay interval after determining that the power tool device is not in operation, After the delay interval ends, the discharge switch is enabled to discharge the voltage stored on the DC link bus through the discharge resistor.

10. The power tool device according to claim 9, wherein: The controller is configured to provide an on command to the controller pin after the delay interval has expired.

11. The power tool device according to claim 9, wherein: The power tool device is configured to disconnect the battery pack interface from the DC link capacitor using a solid-state disconnect circuit.

12. The power tool device according to claim 9, wherein: The controller is configured to determine a safe operating state of the power tool equipment.

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