DRIVING METHOD FOR BRUSHLESS MOTOR

PROBLEM TO BE SOLVED: To prevent acoustic noises and improve efficiency in driving a three- phase brushless motor. SOLUTION: After signals detected from three Hall-effect elements are clamped, a maximum value of signals an and b* out of these signals is detected to generate a waveform (A), and a minimum value is also detected to generate a waveform (B). The waveform (A) is reversed and shifted to generate a waveform (C), and a waveform (D) is also generated from the waveform (B). The waveforms (C) and (D) are gated and synthesized to generate a first energizing waveform (G). Then, signals b and c* are synthesized to generate a second energizing waveform (indicated in dashed line), while signals c and a* are synthesized to generate a third energizing waveform (indicated, in alternate short and long dashed line). The generated energizing waveform (H) is supplied to a stator coil.