JPS6434191A - Device for driving brushless dc motor - Google Patents

Abstract

PURPOSE:To miniaturize the title device and stabilize the rotation of a motor, by a method wherein pulses in every 60 deg. are obtained from the terminal voltage of the motor to output a driving waveform, correcting the phase of the motor and increasing or decreasing an output voltage. CONSTITUTION:In the driving circuit of a brushless DC motor 18, a counter electromotive voltage is inputted from input terminals 1a-1c into filters 20a-20c. The outputs 46a-46c of the filters are inputted into a differentiating and AND circuit 21 and a micro-computer 22 through comparators 4a-4c while an inverter circuit 17 is controlled by the output of the micro-computer 22 to drive a motor 18. The differentiating and AND circuit 21 functions as a pulse generating means and the micro-computer 22 functions as a phase correcting means, an output voltage increasing and decreasing means and a control means while a timer and a counter, incorporated into the micro-computer, function as a rotating frequency operating means. According to this constitution, the filter constant of a filter circuit 20 may be designed regardless of the delay of a phase by correcting the phase of a terminal voltage after passing through the filter and the phase of the position of a field rotor.