Patent ID: 8933653
Filing Date: 2015-01-13
Classification: H02P

Abstract:
1. A motor current detection apparatus comprising: a current detection unit configured to detect a conduction current flowing from a battery to a brushless motor and output a conduction current signal corresponding to the detected conduction current; a first filter configured to extract a first current signal which is included in the conduction current signal outputted from the current detection unit and is a signal component in a frequency band equal to or lower than a predetermined first cutoff frequency; a second filter configured to extract a second current signal which is included in the conduction current signal outputted from the current detection unit and is a signal component in a predetermined frequency band within a frequency band equal to or lower than a predetermined second cutoff frequency higher than the first cutoff frequency and having the second cutoff frequency as a maximum value; a first comparison circuit that is configured to compare a value of the first current signal and a previously set first threshold value, and to output to a first overcurrent determination unit a first comparison signal having one of a High level and a Low level depending on whether or not the value of the first current signal exceeds the first threshold value, the first overcurrent determination unit being configured to determine that a first current corresponding to the first current signal is an overcurrent in a case where the first comparison signal from the first comparison circuit has a level indicating that the value of the first current signal exceeds the first threshold value; and a second comparison circuit that is configured to compare a value of the second current signal and a previously set second threshold value larger than the first threshold value, and to output to a second overcurrent determination unit a second comparison signal having one of a High level and a Low level depending on whether or not the value of the second current signal exceeds the second threshold value, the second overcurrent determination unit being configured to determine that a second current corresponding to the second current signal is an overcurrent in a case where the second comparison signal from the second comparison circuit has a level indicating that the value of the second current signal exceeds the second threshold value.