Controlled Power Fade For Battery Powered Devices
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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.
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Citations
48 Claims
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1-25. -25. (canceled)
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26. A method for operating a power tool having a trigger switch and a motor powered by a battery pack, comprising:
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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. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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33. A power tool system comprising:
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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. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41)
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42. A power tool system comprising:
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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. - View Dependent Claims (43, 44, 45, 46, 47, 48)
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Specification