Controlled power fade for battery powered devices

Patent metadata

Field	Value
Publication number	US-9413088-B2
Application number	US-201514603977-A
Country	US
Kind code	B2
Filing date	Jan 23, 2015
Priority date	Apr 7, 2010
Publication date	Aug 9, 2016
Grant date	Aug 9, 2016

Abstract

A method is provided for operating a power tool having a motor powered by a battery. The method includes: delivering power from the battery to the motor in accordance with an operator input; detecting a condition of the power tool indicating a shutdown of the power is imminent; and fading the power delivered from the battery to the motor, in response to the detected condition, through the use of a controller residing in the power tool.

First claim

What is claimed is:

1. A method for operating a power tool having a trigger switch and a motor powered by a battery pack, comprising:
setting the duty cycle of a pulse width modulated control signal in accordance with a position of the trigger switch;
delivering power from the battery pack to the motor in accordance with the control signal;
monitoring a parameter indicative of tool operation while power is delivered from the battery pack to the motor using a controller residing in the power tool;
detecting a condition of the parameter indicating a shutdown of the power is imminent; and
fading the power delivered from the battery to the motor, in response to the detected condition, using the controller, wherein the fading step comprises:
computing a value of the duty cycle as a function of a value of the parameter, and
setting the duty cycle of the control signal to the computed value of the duty cycle when the computed value of the duty cycle is less than the duty cycle set in accordance with position of the trigger switch, and retaining the duty cycle set in accordance with the position of the trigger switch when the computed value of the duty cycle is more than the duty cycle set in accordance with the position of the trigger switch.

2. The method of claim 1 wherein fading of the power delivered is by an amount that is computed as a function of a value of the parameter.

3. The method of claim 1 wherein fading of the power delivered further comprises decreasing the power delivered as a function of the value of the parameter, where the function is at least one of linear, step, exponential or polynomial.

4. The method of claim 1 wherein the parameter is voltage of the battery, comprising: initiating fading of the power delivered when the battery voltage falls below a voltage fade threshold and decreasing the power delivered linearly as a function of the battery voltage until the battery voltage falls below a voltage cutoff threshold.

5. The method of claim 1 wherein the parameter is temperature in the power tool, the method comprising: initiating fading of the power delivered when the temperature exceeds a temperature fade threshold and decreasing the power delivered linearly as a function of the temperature until the temperature exceeds a temperature cutoff threshold.

6. The method of claim 1 wherein the parameter is temperature in the battery pack, the method comprising: fading of the power delivered when the temperature exceeds a temperature fade threshold and decreasing the power delivered linearly as a function of the temperature until the temperature exceeds a temperature cutoff threshold.

7. The method of claim 6 , wherein the battery pack includes a positive terminal, a negative terminal, a temperature sense terminal, battery cells coupled to the positive and negative terminals, and a temperature sensor electrically coupled to the positive terminal.

8. A power tool system comprising:
a tool assembly having a motor;
a battery pack that selectively couples to the tool assembly and operates to provide power to the motor;
a trigger switch disposed on the tool assembly;
a discharge control module that is in data communication with the trigger switch and regulates power provided to the motor in accordance with a position of the trigger switch by adjusting a duty cycle of pulse width modulated control signal of a switch disposed in series with the motor, wherein the discharge control module is configured to monitor a parameter indicative of tool operation while power is delivered from the battery pack to the motor and fade the power delivered from the battery to the motor by adjusting the duty cycle of the control signal by an amount that is computed as a function of a value of the parameter,
wherein the discharge control module sets the duty cycle to a value computed as a function of a value of the parameter when the computed value of the duty cycle is less than the duty cycle set in accordance with position of the trigger switch, and retains the duty cycle set in accordance with the position of the trigger switch when the computed value of the duty cycle is more than the duty cycle set in accordance with the position of the trigger switch.

9. The power tool system of claim 8 wherein the discharge control module fades the power delivered by decreasing the power delivered as a function of the value of the parameter, where the function is at least one of linear, step, exponential or polynomial.

10. The power tool system of claim 8 , wherein the discharge control module monitors voltage of the battery, initiates fading of the power delivered when the battery voltage falls below a voltage fade threshold and decreases the power delivered linearly as a function of the battery voltage until the battery voltage falls below a voltage cutoff threshold.

11. The power tool system of claim 8 , further comprising a temperature sensor disposed in the tool assembly, wherein the discharge control module is configured to receive a temperature measure from the temperature sensor, initiate fading of the power delivered when the temperature exceeds a temperature fade threshold and decrease the power delivered linearly as a function of the temperature until the temperature exceeds a temperature cutoff threshold.

12. The power tool system of claim 8 , further comprising a temperature sensor disposed in the battery pack and in data communication with the discharge control module, wherein the discharge control module is configured to monitor temperature in the battery pack, initiate fading of the power delivered when the temperature exceeds a temperature fade threshold and decrease the power delivered linearly as a function of the temperature until the temperature exceeds a temperature cutoff threshold.

13. The power tool of claim 12 , wherein the battery pack includes a positive terminal, a negative terminal, a temperature sense terminal, battery cells coupled to the positive and negative terminals, and a temperature sensor electrically coupled to the positive terminal.

14. The power tool of claim 8 , wherein the switch is disposed in series with battery cells of the battery pack.

15. The power tool system of claim 8 , wherein the discharge control module resides in the tool assembly.

16. The power tool system of claim 8 , wherein the discharge control module resides in the battery pack.

17. A power tool system comprising:
a tool assembly having a motor;
a battery pack having a plurality of battery cells that selectively couples to the tool assembly via a positive terminal and a negative terminal to provide electric power to the motor;
a trigger switch disposed on the tool assembly; and
a discharge control module within the tool assembly that controls power delivered from the battery to the motor in accordance with a position of the trigger switch, wherein the discharge control module is electrically coupled to the battery pack to measure voltage of the battery cells while the tool is being operated by a user by interrupting current flow from the battery pack to the motor momentarily via a power switch while the trigger switch is being pulled by the user and measuring voltage of the battery in an unloaded condition while current flow is interrupted, the discharge control module being further configured to compare the unloaded voltage measure to a voltage cutoff threshold, and resume current flow from the battery to the motor when the unloaded voltage measure exceeds the voltage cutoff threshold.

18. The power tool of claim 17 , wherein the discharge control module is

Assignees

• Black & Decker Inc

Inventors

• Brotto Daniele C
• Forster Michael K
• Leh Jason K
• Lin Wing W

Classifications

• H02J7/585

  Sequential battery discharge in systems with a plurality of batteries · CPC title

• H02J7/63

  against overdischarge · CPC title

• H02J7/60

  including safety or protection arrangements · CPC title

• H02J7/855

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

• H02J7/751

  concerning the insertion or the connection of the batteries · CPC title