Patent ID: 9024549
Filing Date: 2015-05-05
Classification: H02P

Abstract:
1. An over-temperature protection circuit for use with an electric motor of a direct current (DC) electric tool powered by use of a battery pack, comprising: a current detecting circuit electrically coupled to the battery pack and detecting a battery pack discharge current; a power device for controlling power provided to the electric motor to thereby cause the electric motor to rotate in one of plurality of power states and wherein the plurality of power states includes a speed control power state; and a computation control circuit in communication with the current detecting circuit for controlling the power device as a function of the battery pack discharge current being detected by the current detecting circuit wherein the computation control circuit causes the power device to stop power being provided to the electric motor when the battery pack discharge current as detected by the current detecting circuit exceeds a first current condition value while the electric motor is being caused to rotate in a one of the plurality of power states excluding the speed control power state by the power device and causes the power device to stop power being provided to the electric motor when the battery pack discharge current as detected by the current detecting circuit exceeds a preset second current condition value as detected by the current detecting circuit while the electric motor is being caused to rotate in the speed control power state by the power device and wherein the preset second current condition value is less than the preset first current condition value.