Patent ID: 7574873

Claim:
An inverter device for driving a sensorless DC brushless motor, comprising: an inverter circuit for switching a direct-current voltage obtained from a direct-current power source and supplying an alternating-current current of a sinusoidal wave to the sensorless DC brushless motor, wherein the direct-current voltage of the direct-current power source is switched by three-phase modulation; and current detecting means for detecting a power supply current between the direct-current power source and the inverter circuit, wherein the sensorless DC brushless motor includes stator windings of a three-phase wiring (U, V, W) electrically connected to the inverter circuit and a magnet rotor, and within a carrier period of the three-phase modulation, a current feeding time is equally added or subtracted in a current feeding period in each phase of the stator windings, and the current detecting means is a single current detecting means which is used also for detecting the current flowing in the stator windings, and by detecting the current flowing in the stator windings as well as detecting the power supply current, a rotational position of the magnet rotor is judged to thereby control the switching of the inverter circuit.