Method and apparatus for driving a brushless motor

Claim 2

Apparatus for driving an n-phase, m-pole (n and m are integers) brushless motor without use of physical rotary position detectors, such as Hall elements, comprising: harmonic detecting means for detecting an harmonic component of back emf induced in the phases of said motor; first and second comparator means exhibiting first and second different hysteresis characteristics, respectively, for generating first and second rectangular waveforms when said harmonic component crosses a reference level; counting means including an input stage whose state is determined by the polarity of one of said rectangular waveforms at a time determined by transitions in the other of said rectangular waveforms; decoding means for decoding the count of said counting means to produce a sequence of phase energizing signals to energize selected phases of said motor; and drive current means for supplying drive current to those phases energized by said phase energizing signals.

Claim 3

The apparatus of claim 1 wherein said input stage comprises flip-flop means having a data input for receiving said one rectangular waveform and a clock input;

Claim 4

Apparatus for driving an n-phase, m-pole (n and m are integers) brushless motor without use of physical rotary position detectors, such as Hall elements, comprising: harmonic detecting means for detecting an harmonic component of back emf induced in the phases of said motor; phase energizing means responsive to said harmonic component for generating phase energizing signals to energize selected phases of said motor; drive current means for supplying drive current to those phases energized by said phase energizing signals; and start-up means coupled to said phase energizing means for controlling the phase energizing signals generated to start up the rotation of said motor, said start-up means including means for supplying a clock signal at a relatively low frequency to said phase energizing means for a first predetermined time period, means for increasing the frequency of said clock signal for a second predetermined time period, and means for terminating the clock signal supplied to said phase energizing means at the completion of said second predetermined time period.

Claim 5

Apparatus for driving an n-phase, m-pole (n and m are integers) brushless motor without use of physical rotary position detectors, such as Hall elements, comprising: harmonic detecting means for detecting an harmonic component of back emf induced in the phases of said motor; phase energizing means responsive to said harmonic component for generating phase energizing signals to energize selected phases of said motor; drive current means for supplying drive current to those phases energized by said phase energizing signals; and start-up means coupled to said phase energizing means for controlling the phase energizing signals generated to start up the rotation of said motor, said start-up means including means for supplying a clock signal at a relatively low frequency to said phase energizing means for a first predetermined time period, means for increasing the frequency of said clock signal for a second predetermined time period, and means for terminating the clock signal supplied to said phase energizing means at the completion of said second predetermined time period.

Claim 6

The apparatus of claim 3 wherein said start-up means further includes means for controlling said drive current means to supply a drive current whose amplitude gradually increases over said first predetermined time period in a ramp-like manner from a relatively low reference level to a motor drive level.

Claim 7

The apparatus of claim 4 wherein said start-up means further includes means for delaying the beginning of said second predetermined time period relative to the completion of said first predetermined time period.