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US 7,133,601 B2Granted
Amperage control for protection of battery over current in power tools
AssigneeBlack & Decker Inc.
InventorsAlan Phillips, Julie L. Jones
Life of this patent
Estimating the term…
Abstract
Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply preferably includes a battery, such a lithium ion or nickel cadmium.
Claims17
A method for extending the life of a power supply that supplies power to a motor in a power tool, comprising:
- supplying voltage pulses of an initial width to the motor using pulse width modulation;
- comparing a motor current generated due to the supplied voltage pulses to at least one of three different thresholds;
- and
- changing the pulse width from the initial width to one of zero, a first alternative pulse width and a second alternative pulse width based on the comparison to a given threshold.
1 more element
A power tool, comprising:
- a housing;
- a power supply disposed within the housing and including a plurality of lithium ion batteries;
- a motor disposed within the housing and providing torque to the power tool;
- and
- a pulse width modulation controller within the housing for varying the pulse width of voltage pulses supplied to the motor based on a comparison of the motor current to one of at least three different thresholds.
2 more elements
An apparatus for limiting current to a load, comprising:
- means for supplying power;
- means for providing torque to a load;
- means for switchably supplying power to the means for providing torque from the means for supplying power, the means for switchably supplying power being actuated according to a pulse width modulation technique;
- and
- means for controlling the means for switchably supplying power based on a comparison of current generated in the apparatus to one of at least three different thresholds.
2 more elements
Dependencies are inferred from the claim text.