초록 ▼

A circuit for driving a brushless dc motor includes an active deceleration circuit for rapidly slowing the motor. A phase locked loop senses a position of the rotor for commutating from a drive state to a next drive state in a sequence of drive states at an appropriate time for maintaining torque on

A circuit for driving a brushless dc motor includes an active deceleration circuit for rapidly slowing the motor. A phase locked loop senses a position of the rotor for commutating from a drive state to a next drive state in a sequence of drive states at an appropriate time for maintaining torque on the rotor in the direction of rotation. Thus, the rotor "chases" the energized windings. A speed control loop controls current in the windings and, thus, motor speed. When the speed of the motor exceeds a desired speed by more than a threshold amount, rather than commutating to a next drive state in the sequence, the circuit skips a commutation. By skipping one commutation, the current drive state is maintained while the rotor continues to turn, due to its own inertia, such that the rotor "passes up" the current drive state. This results in a torque on the rotor in a direction opposite rotation. When the phase locked loop indicates an appropriate time for commutating to a next drive state, the circuit transitions to the next drive state in the sequence. Therefore, the current drive state continues to remain one commutation behind the normally appropriate drive state, maintaining the reverse torque. Accordingly, during deceleration, the energized windings "chase" the rotor. When the rotor slows sufficiently, the energized windings will "catch up" to the rotor such that the current drive state will be the appropriate drive state for again inducing a torque on the rotor in the direction of rotation.

대표청구항 ▼

[ I claim:] [8.] A circuit for driving a brushless dc motor, the circuit comprising:a. a phase locked loop for commutating to a next drive state in a sequence of drive states wherein a torque on a rotor of the motor is maintained in a direction of rotation;b. a speed control loop coupled to the phas

[ I claim:] [8.] A circuit for driving a brushless dc motor, the circuit comprising:a. a phase locked loop for commutating to a next drive state in a sequence of drive states wherein a torque on a rotor of the motor is maintained in a direction of rotation;b. a speed control loop coupled to the phase locked loop for sensing a speed of the rotor for controlling a level of the torque; andc. a deceleration circuit coupled to the speed control loop for skipping exactly one commutation wherein the torque on the rotor is maintained in a direction opposite rotation after the speed of the rotor exceeds a desired speed.