Method and circuitry for drag braking a polyphase DC motor
First Claim
1. A data storage system, comprising:
- a polyphase DC motor for rotating a data medium, having a rotor and a plurality of stator coils;
a sequencer for incrementally generating sets of commutation signals to select stator coils for energization to rotate said rotor according to a commutation sequence that increments in a forward direction and generates a flux vector that leads the rotor;
a power stage to which said commutation signals are applied to energize the selected coils in accordance with said commutation signals;
a circuit for interrupting the energization of the selected coil;
a circuit for producing an altered commutation sequence that increments in a forward direction and generates a flux vector that lags the rotor; and
a circuit for applying the altered commutation sequence to said power stage to brake the rotation of the rotor.
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Abstract
A method and circuit for braking a forward rotation of a rotor of a polyphase DC motor. A commutation sequencer is incremented by several phases to produce an incremented commutation sequence to produce a magnetic flux vector that lags a magnetic pole of the motor. Driving currents are applied to coils of the motor in accordance with the incremented commutation sequence to brake the rotor. The method is implemented in a circuit that has a sequencer for incrementally generating sets of commutation signals to select stator coils for energization to rotate the rotor. A power stage to which the commutation signals are applied energizes the selected coils in accordance with the commutation signals. A circuit interrupts the energization of the selected coils and the commutation sequence is altered to produce a sequence that produces a negative torque on the rotor. Circuits are also provided to inhibit application of the altered commutation sequence until recirculation currents in the power stage caused by the coils in response to the reduction of the input voltage have fallen below a predetermined level, and to inhibit application of the altered commutation sequence until a voltage on a sense resistor between the power stage and a reference potential has fallen below a predetermined level after an operation of the circuit for interrupting the energization of the selected coils.
32 Citations
22 Claims
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1. A data storage system, comprising:
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a polyphase DC motor for rotating a data medium, having a rotor and a plurality of stator coils; a sequencer for incrementally generating sets of commutation signals to select stator coils for energization to rotate said rotor according to a commutation sequence that increments in a forward direction and generates a flux vector that leads the rotor; a power stage to which said commutation signals are applied to energize the selected coils in accordance with said commutation signals; a circuit for interrupting the energization of the selected coil; a circuit for producing an altered commutation sequence that increments in a forward direction and generates a flux vector that lags the rotor; and a circuit for applying the altered commutation sequence to said power stage to brake the rotation of the rotor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A data storage system, comprising:
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a polyphase DC motor for rotating a data medium, having a rotor and a plurality of stator coils; a power stage to energize selected ones of the plurality of stator coils; a sequencer for incrementally generating sets of commutation signals for application to said power stage to select stator coils for energization to rotate said rotor in a forward direction according to a commutation sequence; said commutation signals being selected to create a magnetic flux vector that moves in advance of a pole of said rotor to cause said rotor to rotate in a forward direction; a circuit for interrupting the energization of the stator coils; a circuit for altering the commutation sequence to produce an altered commutation sequence in the forward direction that creates a flux vector that moves behind the pole of the rotor to apply a negative torque to the rotor; and a circuit to adjust a supply voltage to the power stage to control a magnitude of the negative torque applied to the rotor. - View Dependent Claims (10, 11)
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12. A data storage system, comprising:
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a polyphase DC motor for rotating a data medium, having a rotor and a plurality of stator coils; a power stage to energize selected ones of the plurality of stator coils; a sequencer for incrementally generating sets of commutation signals for application to said power stage to select stator coils for energization to rotate said rotor according to a commutation sequence; said commutation signals being selected to create a magnetic flux vector that moves in advance of a pole of said rotor to cause said rotor to rotate in a forward direction; a circuit for interrupting the energization of the stator coils; a circuit for altering the commutation sequence to produce an altered commutation sequence that creates a flux vector that moves behind the pole of the rotor to apply a negative torque to the rotor; and a circuit for reducing an input voltage from the power stage in response to a signal to brake the rotor, and for reapplying the input voltage after the altered commutation sequence has been applied. - View Dependent Claims (13, 14, 15)
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16. A data storage system comprising:
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a polyphase DC motor for rotating a data medium, having a rotor and a plurality of stator coils; a power stage to energize selected ones of the plurality of stator coils; a sequencer for incrementally generating sets of commutation signals for application to said power stage to select stator coils for energization to rotate said rotor according to a commutation sequence; said commutation signals being selected to create a magnetic flux vector that moves in advance of a pole of said rotor to cause said rotor to rotate in a forward direction; a circuit for interrupting the energization of the stator coils; and a circuit for altering the commutation sequence to produce an altered commutation sequence that creates a flux vector that moves behind the pole of the rotor to apply a negative torque to the rotor, wherein said circuit for altering the commutation sequence to produce an altered commutation sequence comprises a plurality of multiplexers connected to output the sets of commutation signals in a first order in the absence of a reverse torque signal, and to output the sets of commutation signals in a second order in the presence of a reverse torque signal.
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17. A data storage system comprising:
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a brushless and sensorless DC motor for rotating a data medium, having a rotor and having a stator with at least three coils; energizing means for energizing said at least three coils in accordance with sequential commutation sequences; interrupting means for interrupting the energizing of said at least three coils; monitoring means for monitoring the voltage outputs of said at least three coils after the interrupting means has interrupted the energizing of said at least three coils; and altering means for producing an altered commutation sequence that produces a negative torque on the rotor. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification