Short circuit detection in a power tool

Patent metadata

Field	Value
Publication number	US-2025102596-A1
Application number	US-202418888934-A
Country	US
Kind code	A1
Filing date	Sep 18, 2024
Priority date	Sep 22, 2023
Publication date	Mar 27, 2025
Grant date	—

Abstract

Power tools that include a housing, a motor supported by the housing, an inverter positioned between and electrically connected to a battery pack interface and the motor, a gate driver connected to the inverter, a rotational position detector configured to detect a position of the motor, a controller configured to control the gate driver, and a short circuit detection circuit. The short circuit detection circuit is configured to monitor the current in the inverter, compare the current in the inverter to a first current threshold, determine, in response to the current in the inverter being greater than or equal to the first current threshold, whether the position of the motor is changing based on a signal from the rotational position detector, and control, in response to the position of the motor not changing, a switch of the short circuit detection circuit to disable the gate driver.

First claim

What is claimed is:

1 . A power tool comprising:
a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack including a plurality of battery cells; an inverter positioned between and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter, the gate driver configured to control a current in the inverter; a rotational position detector configured to detect a position of the motor; a controller configured to control the gate driver; and a short circuit detection circuit configured to:
monitor the current in the inverter,
compare the current in the inverter to a first current threshold,
determine, in response to the current in the inverter being greater than or equal to the first current threshold, whether the position of the motor is changing based on a signal from the rotational position detector, and
control, in response to the position of the motor not changing, a switch of the short circuit detection circuit to disable the gate driver.

2 . The power tool of claim 1 , further comprising:
an indicator configured to provide an indication of a status of the short circuit detection circuit.

3 . The power tool of claim 1 , wherein the rotational position detector includes a plurality of Hall effect sensors, each Hall effect sensor configured to provide a Hall effect sensor signal corresponding to a position of a rotor of the motor.

4 . The power tool of claim 1 , wherein the short circuit detection circuit is further configured to:
select the first current threshold based on a voltage provided by the battery pack to the battery pack interface.

5 . The power tool of claim 1 , wherein the short circuit detection circuit is further configured to:
adjust a value of the first current threshold based on a change in the current in the inverter.

6 . The power tool of claim 1 , wherein the short circuit detection circuit is further configured to:
determine whether an expected braking time has elapsed; compare, in response to the expected braking time having elapsed, the current in the inverter to the first current threshold; and control, in response to the current in the inverter being greater than or equal to the first current threshold and in response to the expected braking time having elapsed, the switch of the short circuit detection circuit to disable the gate driver.

7 . The power tool of claim 1 , wherein the short circuit detection circuit is further configured to:
determine, in response to the position of the motor not changing, whether a stall time has elapsed; and control, in response to the stall time having elapsed, the switch of the short circuit detection circuit to disable the gate driver.

8 . The power tool of claim 1 , further comprising:
a trigger configured to be actuated, and wherein the short circuit detection circuit is further configured to:
detect actuation of the trigger,
drive, in response to actuation of the trigger, the motor, and
compare the current in the inverter to a first current threshold in response to the trigger being released while driving the motor.

9 . The power tool of claim 8 , wherein the short circuit detection circuit is further configured to:
enable the gate driver in response to actuation of the trigger and in response to the current in the inverter being less than the first current threshold.

10 . A method for controlling a power tool, the method comprising:
monitoring, with a short circuit detection circuit, current in an inverter, the inverter positioned between and electrically connected to a battery pack interface and a motor; comparing, with the short circuit detection circuit, the current in the inverter to a first current threshold; determining, with the short circuit detection circuit and in response to the current in the inverter being greater than or equal to the first current threshold, whether a position of the motor is changing based on a signal from a rotational position detector; and controlling, with the short circuit detection circuit and in response to the position of the motor not changing, a switch of the short circuit detection circuit to disable a gate driver, wherein the gate driver is configured to control a current in the inverter.

11 . The method of claim 10 , further comprising:
providing, with an indicator, an indication of a status of the short circuit detection circuit.

12 . The method of claim 10 , further comprising:
receiving, by the battery pack interface, a battery pack; and selecting the first current threshold based on a voltage provided by the battery pack to the battery pack interface.

13 . The method of claim 10 , further comprising:
adjusting a value of the first current threshold based on a change in the current in the inverter.

14 . The method of claim 10 , further comprising:
determining whether an expected braking time has elapsed; comparing, in response to the expected braking time having elapsed, the current in the inverter to the first current threshold; and controlling, in response to the current in the inverter being greater than or equal to the first current threshold and in response to the expected braking time having elapsed, the switch of the short circuit detection circuit to disable the gate driver.

15 . The method of claim 10 , further comprising:
determining, in response to the position of the motor not changing, whether a stall time has elapsed; and controlling, in response to the stall time having elapsed, the switch of the short circuit detection circuit to disable the gate driver.

16 . A power tool comprising:
a housing; a motor supported by the housing; a battery pack interface configured to receive a battery pack, the battery pack including a plurality of battery cells; an inverter positioned between and electrically connected to the battery pack interface and the motor; a gate driver connected to the inverter, the gate driver configured to control a current in the inverter; a controller configured to control the gate driver; and a short circuit detection circuit configured to:
monitor the current in the inverter,
compare the current in the inverter to a first current threshold,
compare, in response to the current in the inverter being greater than or equal to the first current threshold, the current in the inverter to a second current threshold, wherein a value of the second current threshold is based on a timer,
increment, in response to the current in the inverter being greater than or equal to the second current threshold, the timer, and
control, in response to the timer being greater than or equal to a timer threshold, a switch of the short circuit detection circuit to disable the gate driver.

17 . The power tool of claim 16 , wherein the short circuit detection circuit is further configured to:
increment, in response to the increment of the timer, the second current threshold.

18 . The power tool of claim 17 , wherein the short circuit detection circuit is further configured to:
compare, in response to the current in the inverter being greater than or equal to the first current threshold, the current in the inverter to the incremented second current threshold; and increment, in response to the current in the inverter being greater than or equal to the incremented second current threshold, the timer.

19 . The power tool of claim 16 , further comprising:
a rotational position detector c

Assignees

• Milwaukee Electric Tool Corp

Inventors

• Goltz Thomas
• Chadha Ankit
• Ganesan Nandini
• Noel Matthew C
• Al Musawi Mustafa Ibrahim Abed
• Kitzerow David J

Classifications

• H02J7/855

  with circuits adapted for supplying loads from the battery · CPC title

• H02J7/96 Primary

  in response to battery voltage · CPC title

• G01R31/52 Primary

  Testing for short-circuits, leakage current or ground faults · CPC title

• H02K29/08

  using magnetic effect devices, e.g. Hall-plates, magneto-resistors (H02K29/12 takes precedence) · CPC title

• G01R31/56

  Testing of electric apparatus (testing of transformers G01R31/62; testing of connections G01R31/66) · CPC title