Patent ID: 7733042
Filing Date: 2010-06-08
Classification: H02P

Abstract:
1. A rotor position detection circuit for detecting a position of a rotor in a motor based on a detection signal of an induced voltage, which is generated in a stator coil in the motor, the circuit comprising: a first low pass filter circuit for filtering the detection signal in a low frequency range, wherein the first low pass filter circuit has a first reference potential; a comparator for comparing an output signal from the first low pass filter circuit with a predetermined reference voltage and for outputting a rotation position signal based on a comparison between the output signal and the predetermined reference voltage; and a second low pass filter circuit for filtering a virtual neutral point potential of the motor in a low frequency range, wherein the second low pass filter circuit has a second reference potential, wherein the first low pass filter circuit is a single low pass filter provided by a first capacitor and a first resistor, the second low pass filter circuit is a single low pass filter provided by a second capacitor and a second resistor, the first reference potential of the first low pass filter circuit is the filtered virtual neutral point potential of the second low pass filter circuit, and the second reference potential of the second low pass filter circuit is a ground.