JPS57177287A - Speed controller for brushless motor - Google Patents

Abstract

PURPOSE:To eliminate the influence of the distortion of a signal waveform from a position detector of a brushless motor by forming a waveform synchronized with the rotating angle of a motor rotor and deciding an energization period from the waveform to a coil. CONSTITUTION:When an output signal from a position detector 6 is ''H'', a diode D1 is reversely biased to interrupt a transistor T1, and a charging current which is controlled by a constant-current source having operational amplifiers OP1, T2, T3- R5 and which is proportional to a speed signal Vr from a speed detector 11 flows through a capacitor C1. The waveform b which is maintained constantly at a gradient with respect to the rotating angle theta of a rotor is compared by an operational amplifier OP2 with the Vr, becomes ''H'' when the Vr exceeds the waveform b, thereby interrupting the T3, the C2 is controlled by the constant-current source having Tr, OP3 and R8-R10, a charging current which is proportional to the Vr flows through the C2, and the gradient of the waveform d becomes constant with respect to the rotating angle theta. A speed error signal Vc is compared by an OP4 with the waveform d, a pulse e is formed during the period exceeding the waveform d, the waveforms e, c are applied to an AND gate, the output of which drives the Tb through a resistor R11, thereby deciding the energizing period delta of a coiling current i as designated by the waveform i.