ARRANGEMENT FOR GENERATING DRIVE SIGNALS FOR A MULTI-PHASE D.C. MOTOR, LOCK DETECTOR, DRIVE ARRANGEMENT AND DISK DRIVE
An arrangement for generating drive signals for a multi-phase d.c. motor (8) having a plurality of windings (2, 4, 6), comprising a multi-phase inverter (10) which supplies the drive signals to the windings (2, 4, 6) of the motor in such a manner that these windings are recurrently energized by the drive signals in a given sequence. At least one of the windings (2, 4, 6) is not supplied with a drive signal at least during predetermined free periods. The arrangement further comprises a phase detector (40) which under control of said multi-phase inverter (10) samples the back-emf signals of these windings in order to obtain a phase-error signal, a low-pass filter (42) which generates a control signal in dependence upon the phase-error signal, and a controllable oscillator (44) which generates a frequency signal whose frequency depends on the control signal. The timing with which the multi-phase inverter (10) supplies the drive signals to the windings (2, 4, 6) depends on the frequency signal, the arrangement thus comprising a phase-locked loop formed by the multi-phase inverter (10), the phase detector (40), the low-pass filter (42) and the oscillator (44). The arrangement further comprises a lock detector (70) which on the basis of informtaion about the frequency and phase of the phase-error signal and information about the frequency and phase of the frequency signal determines whether or not the phase-locked loop is locked in phase.