Patent ID: 7710056

Claim:
A brushless DC motor comprising: a stator having a stator coil; a permanent-magnet rotor disposed opposite to the stator; a rotor magnetic-field detecting element for detecting a magnetic field of the permanent-magnet rotor; a rectifying circuit for rectifying AC voltage of an AC power supply in full-wave; a DC power supply for converting the voltage rectified by the rectifying circuit into a low DC voltage; an inverter circuit having a plurality of switching elements in full-wave bridge connection, to which an output voltage of the DC power supply is applied; a driving logic circuit for controlling the switching elements to pass current through the stator coil; a current control circuit for controlling current passing through the inverter circuit; and a current-indicating circuit for indicating the current passing through the inverter circuit, wherein the current control circuit controls the output voltage of the DC power supply so that the current passing through the inverter circuit equals the current indicated by the current-indicating circuit, and the current indicated by the current-indicating circuit is further increased as the output voltage increases, and wherein the current control circuit increases the current passing through the inverter circuit as the motor increases its speed.