JPS5743588A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To prevent generation of spike voltage and vibration of a brushless DC motor, by switching and controlling a currentpassing coil by terminal voltage of a capacitor which is charged and discharged by prescribed current to be determined by circuit in accordance with a position detecting signal. CONSTITUTION:A position detecting signal Va is put into a passing current switching section 13; connection of a switch 22 for a charging and discharging switch section 23 is changed over in accordance with Va; a capacitor 24 is charged or discharged by a prescribed current of constant current sources 20 and 21 in accordance with state of this switch 22, and a voltage range of the terminal voltage Wa is limited by a voltage limiting circuit 27. In the case of a position detecting signal Vb, as it is so in the case of the position detecting signal Va, a voltage range of a terminal voltage Wb of a capacitor 32 is limited. A voltage Wc is made to take a wave shape matching Vb by a voltage switching circuit 45. Wa-Wc are put into a differential circuit 49, and collector currents i1-i3 of transistors 46-48 become equal to distribution of a current ie in accordance with Wa-Wc ratio, and transistors 50-52 for driving of motor coils A-C are controlled by i1-i3.