Drive apparatus and speed control apparatus for brushless motor

摘要

A drive apparatus for use in a brushless motor with a rotor and a drive coil assembly. The drive apparatus comprises an energization-state instruction circuit for generating an energization-state instruction signal instructing an energization state of the drive coil assembly on the basis of the position detection signal indicative of a position of the rotor and an energization switching circuit for outputting an energization switching signal to successively switch the energization state of the drive coil assembly in accordance with the energization-state instruction signal and a duty control signal. A power circuit is coupled to a direct-current voltage source and is responsive to the energization switching signal so as to energize the drive coil assembly by means of a direct-current voltage from the direct-current voltage source in accordance with the energization switching signal therefrom. A duty control circuit is responsive to a speed instruction signal from a speed instruction circuit and a motor speed signal from a speed detecting circuit for outputting the duty control signal to the energization switching circuit so as to control a duty ratio of the energization-state instruction signal on the basis of the duty control signal so as to output the energization switching signal to be inputted to the power circuit.