# US 12,000,873 B2 · Power tool, detection circuit and detection method of load state of power tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,000,873 B2 - Document ID: US12000873B2 - Status: Granted - Kind: B2 - Application number: 17/686,378 - Filed: 2022-03-03 - Published: 2022-09-15 - Granted: 2024-06-04 - Earliest claimed: 2021-03-09 - Assignees: Globe (Jiangsu) Co., Ltd. - Applicants: Globe (Jiangsu) Co., Ltd. - Inventors: Zefeng Wei; Biao Li; Xian Zhuang - Web page: https://patentgrep.com/patent/US12000873B2 ## CPC - G01R 19/16523: {using diodes, e.g. Zener diodes} - H02P 29/024: Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load - B25F 5/00: Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for - G01R 15/144: {Measuring arrangements for voltage not covered by other subgroups of G01R15/14} - G08B 5/36: using visible light sources - G08B 21/182: {Level alarms, e.g. alarms responsive to variables exceeding a threshold} - H02J 7/80: including monitoring or indicating arrangements - H02J 7/855: {with circuits adapted for supplying loads from the battery} - B23D 59/001: {Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade (measuring in general G01; controlling in general G05)} - B27B 17/00: Chain saws; Equipment therefor {(slotting or mortising machines equipped with chain cutters B27F5/06)} - H02J 2207/20: Charging or discharging characterised by the power electronics converter - H02M 3/00: Conversion of DC power input into DC power output - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - B25F: COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR {(machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass B23P23/00 and subgroups)} - G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - B23D: PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR (making toothed gears or the like B23F; cutting metal by applying heat locally B23K; arrangements for copying or controlling B23Q) - B27B: SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR (saws specially adapted for pruning or debranching A01G3/08; sawing apparatus specially adapted for felling trees A01G23/091; features not restricted to a particular type of wood saw B23D, e.g. attaching saw blades B23D51/00; machine tool frames, beds, pillars or like members, in general B23Q1/01) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) ## Abstract The disclosure provides a power tool, a detection circuit and a detection method of a load state thereof. The detection circuit of the power tool includes: a main control unit, a sampling resistor, a voltage sampling unit and an alarm display unit. The sampling resistor is arranged on a driving loop of a motor. The voltage sampling unit is used to sample a voltage across the sampling resistor. The alarm display unit is connected with the main control unit. The main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor sampled by the voltage sampling unit. ## Claims ### Claim 1 A detection circuit of a load state of a power tool, comprising: a main control unit, comprising an operational amplifier, a sampling resistor, arranged on a driving loop of a motor, a voltage sampling unit, configured to sample a voltage across the sampling resistor, an alarm display unit, connected with the main control unit, an RC filter circuit, one end of the RC filter circuit being connected with an I/O port of the main control unit, a bias circuit, connected with the main control unit, a first end of the bias circuit being connected with a positive end of the operational amplifier, and a second end of the bias circuit being connected with the sampling resistor, an operational feedback amplifier circuit, connected with the RC filter circuit, and a capacitor C3, connected between the bias circuit and the operational feedback amplifier circuit and connected with a negative end of the operational amplifier, wherein one end of the sampling resistor is connected with the operational feedback amplifier circuit, and the operational amplifier in sequence, the main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor sampled by the voltage sampling unit. ### Claim 2 (depends on 1) The detection circuit of the load state of the power tool according to claim 1, further comprising a second direct current power source, wherein the second direct current power source is respectively connected with power supply terminals of the main control unit, the voltage sampling unit and the alarm display unit. ### Claim 3 (depends on 2) The detection circuit of the load state of the power tool according to claim 2, wherein the second direct current power source is connected with a first direct current power source, the first direct current power source is a driving power source of the power tool, and the first direct current power source is configured to supply power to the second direct current power source. ### Claim 4 (depends on 3) The detection circuit of the load state of the power tool according to claim 3, wherein the first direct current power source comprises a battery pack. ### Claim 5 (depends on 3) The detection circuit of the load state of the power tool according to claim 3, wherein one end of the sampling resistor is connected with a negative electrode of a motor driving unit, the other end of the sampling resistor is connected with a negative electrode of the first direct current power source, and a positive electrode of the motor driving unit is connected with a positive electrode of the first direct current power source. ### Claim 6 (depends on 3) The detection circuit of the load state of the power tool according to claim 3, wherein the voltage sampling unit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C2 and the capacitor C3, one end of the resistor R2 is connected with the second direct current power source, and the other end of the resistor R2 is respectively connected with a positive end of the operational amplifier, one end of the resistor R3 and one end of the capacitor C3, the other end of the resistor R3 is respectively connected with one end of the sampling resistor and a negative electrode of a motor driving unit, the other end of the capacitor C3 is respectively connected with a negative end of the operational amplifier, one end of the resistor R4 and one end of the resistor R5, the other end of the resistor R4 is respectively connected with the other end of the sampling resistor and a negative electrode of the first direct current power source, the other end of the resistor R5 is respectively connected with an output end of the operational amplifier and one end of the resistor R6, the other end of the resistor R6 is respectively connected with an input or output port of the main control unit and one end of the capacitor C2, and the other end of the capacitor C2 is grounded. ### Claim 7 (depends on 2) The detection circuit of the load state of the power tool according to claim 2, wherein the alarm display unit comprises a resistor R1 and a light-emitting diode LED1, one end of the resistor R1 is connected with the second direct current power source, the other end of the resistor R1 is connected with an anode of the light-emitting diode LED1, and a cathode of the light-emitting diode LED1 is connected with the main control unit. ### Claim 8 (depends on 1) The detection circuit of the load state of the power tool according to claim 1, wherein the main control unit is configured to obtain a load current of the power tool according to the voltage signal across the sampling resistor collected by the voltage sampling unit, determine the load state of the power tool according to an obtained magnitude of the load current of the power tool, and determine duration time of a current load state of the power tool, when the duration time of the current load state of the power tool is greater than or equal to a preset time, controlling the alarm display unit to execute a preset display state corresponding to the current load state of the power tool. ### Claim 9 A detection method of a load state of a power tool, comprising: obtaining a load current of the power tool by detecting a voltage across a sampling resistor, determining the load state of the power tool according to an obtained magnitude of the load current of the power tool, and determining duration time of a current load state of the power tool, when the duration time of the current load state of the power tool is greater than or equal to a preset time, controlling an alarm display unit to execute a preset display state corresponding to the current load state of the power tool; wherein, the power tool comprises a main control unit, an RC filter circuit and a bias circuit connected with the main control unit, an operational feedback amplifier circuit, connected with the RC filter circuit, and a capacitor C3 arranged between the bias circuit and the operational feedback amplifier circuit, a generated voltage is amplified by the main control unit and the operational feedback amplifier circuit, then is connected to an I/O port of the main control unit via the RC filter circuit to be processed. ### Claim 10 (depends on 9) The detection method of the load state of the power tool according to claim 9, wherein a value of the load current is defined as a reference current value when the power tool is overloaded, determining the load state of the power tool according to the obtained magnitude of the load current of the power tool comprises: determining the load state of the power tool according to a proportional range of the value of the load current of the power tool to the reference current value. ### Claim 11 (depends on 10) The detection method of the load state of the power tool according to claim 10, wherein determining the load state of the power tool according to the proportional range of the value of the load current of the power tool to the reference current value comprises: defining the load state of the power tool as a first load state when the value of the load current of the power tool is greater than or equal to the reference current value, defining the load state of the power tool as a second load state when the value of the load current of the power tool is greater than or equal to a first preset current value and less than the reference current value, defining the load state of the power tool as a third load state when the value of the load current of the power tool is greater than or equal to a second preset current value and less than the first preset current value, and defining the load state of the power tool as a fourth load state when the value of the load current of the power tool is less than the second preset current value. ### Claim 12 (depends on 11) The detection method of the load state of the power tool according to claim 11, wherein the first preset current value is set from 85% to 95% of the reference current value, and the second preset current value is set from 75% to 85% of the reference current value, the second preset current value is less than the first preset current value. ### Claim 13 A power tool, comprising: a body; a motor and a motor driving unit, arranged on the body; and a detection circuit of a load state of the power tool, arranged on the body, wherein the detection circuit of the load state of the power tool comprises: a main control unit, comprising an operational amplifier, a sampling resistor, arranged on a driving loop of the motor, a voltage sampling unit, configured to sample a voltage across the sampling resistor, an alarm display unit, connected with the main control unit, an RC filter circuit, one end of the RC filter circuit being connected with an I/O port of the main control unit, a bias circuit, connected with the main control unit, a first end of the bias circuit being connected with a positive end of the operational amplifier, and a second end of the bias circuit being connected with the sampling resistor, an operational feedback amplifier circuit, connected with the RC filter circuit, and a capacitor C3, connected between the bias circuit and the operational feedback amplifier circuit and connected with a negative end of the operational amplifier, wherein one end of the sampling resistor is connected with the operational feedback amplifier circuit, and the operational amplifier in sequence, the main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor collected by the voltage sampling unit. ### Claim 14 (depends on 13) The power tool according to claim 13, wherein the power tool comprises a cutting saw or a chain saw.