# US 2012/0074881 A1 · Method and system for electronic braking of a motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2012/0074881 A1 - Document ID: US20120074881A1 - Status: Published application - Kind: A1 - Application number: 13/247,250 - Filed: 2011-09-28 - Published: 2012-03-29 - Earliest claimed: 2010-09-28 - Assignees: Black & Decker Incl. - Inventors: Pradeep M. Pant - Web page: https://patentgrep.com/patent/US20120074881A1 ## CPC - B25B 23/147: specially adapted for electrically operated wrenches or screwdrivers - B25F 5/00: Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for - H02P 6/30: Arrangements for controlling the direction of rotation (H02P6/22 takes precedence) - H02P 23/20: Controlling the acceleration or deceleration - H02P 3/14: by regenerative braking - B25B: TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING, OR HOLDING - 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)} - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract A power tool includes a housing, a brushless DC motor housed inside the housing, a power supply, a control unit, and an input unit such as a trigger switch actuated by a user. The control unit controls the commutation of the motor through a series of power switches coupled to the power supply. The control unit initiates electronic braking of the motor after occurrence of a condition in the input unit, such as trigger release or reduced speed, indicative of the power tool shut-down. A mechanism is provided to power the control unit for a predetermined amount of time after the detection of the condition from the input unit in order to complete the electronic braking of the motor. ## Claims ### Claim 1 A power tool comprising: a housing; a brushless motor housed inside the housing; a power supply; an input unit actuated by a user; and a control unit configured to control commutation of the motor through a plurality of power switches coupled to the power supply and to initiate electronic braking of the motor after occurrence of a condition in the input unit indicative of the power tool shut-down, the control unit remaining powered for a predetermined amount of time after the detection of the condition from the input unit in order to complete the electronic braking of the motor. ### Claim 2 (depends on 1) The power tool of claim 1, wherein the input unit comprises ON/OFF switch. ### Claim 3 (depends on 2) The power tool of claim 2, further comprising a power contact arranged between the power supply and the control unit, the power contact being controlled to provide power to the control unit for the predetermined time after the ON/OFF switch turns OFF. ### Claim 4 (depends on 3) The power tool of claim 3, further comprising a delay module coupled to the power contact and configured to keep the power contact ON for the predetermined time after the ON/OFF switch is turned OFF. ### Claim 5 (depends on 4) The power tool of claim 4, wherein the delay module comprises a capacitor. ### Claim 6 (depends on 2) The power tool of claim 2, wherein the input unit further comprises an actuator coupled to a potentiometer and the ON/OFF switch, wherein release of the actuator turns off the ON/OFF switch. ### Claim 7 (depends on 6) The power tool of claim 6, wherein the control unit monitors the potentiometer speed and initiates electronic braking of the motor when the potentiometer speed falls under a predetermined speed threshold. ### Claim 8 (depends on 7) The power tool of claim 7, further comprising further comprising a power contact arranged between the power supply and the control unit. ### Claim 9 (depends on 8) The power tool of claim 8, further comprising a delay module coupled to the power contact and configured to keep the power contact ON for the predetermined time after the potentiometer speed falls under the predetermined speed threshold. ### Claim 10 (depends on 8) The power tool of claim 8, wherein the control unit is configured to control the power contact and to keep the power contact ON for the predetermined time after the potentiometer speed falls under the predetermined speed threshold. ### Claim 11 (depends on 8) The power tool of claim 8, wherein the control unit is configured to control the power contact and to keep the power contact ON for the predetermined time after the ON/OFF switch is turned OFF. ### Claim 12 (depends on 1) The power tool of claim 1, wherein the plurality of power switches comprises a plurality of high-side switches coupled to corresponding plurality of low-side switches. ### Claim 13 (depends on 12) The power tool of claim 12, wherein the control unit is configured to alternatively turn the plurality of low-side switches and plurality of high-side switches ON and OFF to brake the motor. ### Claim 14 (depends on 1) The power tool of claim 1, wherein the control unit comprises a programmable micro-controller or micro-processor, the power source comprises a DC battery, and the plurality of power switches comprises Field Effect Transistors (FETs). ### Claim 15 A method of controlling a motor inside a power tool comprising: controlling commutation of the motor via a controller and through a plurality of power switches coupled to a power supply; initiating electronic braking of the motor via the controller after occurrence of a condition in a user-actuated input unit of the power tool indicative of the power tool shut-down; and keeping the controller ON for a predetermined amount of time after the detection of the condition from the input unit in order to complete the electronic braking of the motor. ### Claim 16 (depends on 15) The method of claim 15, comprising: keeping the controller ON for the predetermined amount of time after an ON/OFF switch of the input unit is turned OFF. ### Claim 17 (depends on 15) The method of claim 15, comprising: monitoring a speed of a potentiometer from the input unit; and keeping the controller ON for the predetermined amount of time after the speed of the potentiometer falls below a predetermined speed threshold. ### Claim 18 (depends on 15) The method of claim 15, comprising: generating a delay via a delay module between the input unit and a power contact coupled to the power supply to keep the controller ON for the predetermined amount of time. ### Claim 19 (depends on 15) The method of claim 15, comprising: providing a feedback signal from the controller to a power contact coupled to the power supply to keep the controller ON for the predetermined amount of time. ### Claim 20 (depends on 15) The method of claim 15, comprising: turning a plurality of high-side power switches and a plurality of low-side power switches ON and OFF alternatively to brake the motor.