Abstract: A rotation control device causes a disc on which information and sync signals are recorded to rotate at a predetermined speed. The control device includes a generator for generating a signal whose frequency is identical with that of a rotation signal which will be output from a frequency generator while the disc rotates at the predetermined speed. A control loop is defined which compares a phase of an output of the signal generator and a rotation signal output from the frequency generator, thereby controlling the drive of the motor.

Abstract: A D.C. commutatorless electric motor comprises a rotor having a permanent magnet, first and second Hall elements for detecting rotational angle of the rotor according a magnetic field formed by the permanent magnet of the rotor, first and second stator coils respectively coupled to the first Hall element through first and second switching elements, third and fourth stator coils respectively coupled to the second Hall element through third and fourth switching elements, first impedance control element for controlling impedances of the first and second switching elements, and a second impedance control element for controlling impedances of the third and fourth switching elements. One terminal of the first and second stator coils is coupled to a positive power source terminal, and the other terminal of the first and second stator coils is coupled at a common connection point to the third and fourth stator coils which have one terminal coupled to a negative power source terminal.

Abstract: A protective circuit for an electric motor comprises a frequency signal generating circuit for generating a frequency signal in accordance with the rotational speed of the motor, a switching circuit switched over to either permit or cut off supply of current to the motor, and a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of the motor, and cutting off the supply of current to the motor by the switching circuit.

Abstract: A driving circuit for a D.C. commutatorless motor comprises a rotor having a permanent magnet, a pair of Hall elements stator coils positive and negative power sources, power switching elements, where each of the stator coils has one terminal thereof grounded and the other terminal thereof coupled to the positive power source through one of the power switching elements and to the negative power source through another power switching element, a differential switching circuit for switching each of output terminals of the Hall elements with a difference of approximately .pi./2 radians in phase by an output signal thereof, and a difference signal producing circuit coupled between the power switching elements and the differential switching circuit, for producing a signal in accordance with a difference between two output signals having a difference of approximately .pi. radians in phase obtained from the differential switching circuit.

Abstract: A commutatorless electrical motor comprises a cylindrical magnetic rotor having main magnetic poles where N and S poles are alternately arranged in the circumferential direction, and an axis of N and S poles of each magnet extends radially, and a sub magnetic poles at one end of the cylindrical rotor. The sub magnetic poles are arranged such that N and S poles of each magnetized area extends axially. The magnetized area providing each sub magnetic pole has an arcuate extent of .pi./2 or less in an electrical angle. Each of the magnetized area providing each sub magnetic pole makes a given change in the magnetic flux density distribution in the vicinity of rotational position detecting elements so that the rotational position of the rotor can be accurately detected.

Abstract: In a multiphase brushless DC motor having a permanent magnet rotor, a plurality of stator windings and a pair of Hall-effect generators acting as electromagnetic sensors, the stator windings are successively energized by currents supplied from a respective one of a plurality of power transistors which are responsive to the conduction of a respective one of a plurality of switching transistors. The switching transistors are connected in pairs to form first and second differential amplifiers. The latter responds to the potential at the Hall voltage electrode of the respective Hall-effect generator relative to a potential at the junction point of the differential amplifier configuration.

Abstract: A three-phase brushless DC motor has three power transistors with their collector-emitter paths connected to the respective stator windings, three switching transistors with their collector electrodes connected via respective resistors to the negative terminal of a DC voltage source and their emitter electrodes connected in common to the positive terminal of the DC voltage source via a current regulating circuit, and two Hall effect devices each having a pair of control current electrodes and a pair of Hall voltage electrodes. Sinusoidal Hall voltages generated at the Hall electrodes of the Hall effect devices are combined and divided by a voltage dividing network which provides three sinusoidal output voltages. Each of the switching transistors detects the voltage difference between the output voltages. Switching occurs recyclically from one switching transistor to another in response to the output voltage which is higher than any other two output voltages.

Abstract: A three-phase brushless DC motor has three power transistors with their collector-emitter paths connected to the respective stator windings, and two Hall effect devices each having a pair of control current electrodes and a pair of Hall voltage electrodes. One of the Hall voltage electrodes of the Hall effect devices is connected to the base electrodes of the first and second power transistors and the other Hall voltage electrodes are connected together by a combining network which delivers a resultant voltage to the base electrode of the third power transistor. A voltage dividing and balancing network is connected between the base electrodes of the first and second transistors and between the control current electrodes of the Hall effect devices to drive the stator windings with three-phase commutating currents of equal amplitude.