Digital adaptive sensorless commutational drive controller for a brushless DC motor
First Claim
1. A method of providing synchronous commutation to a plurality of phase windings in a brushless, sensorless, direct current (DC) motor comprising:
- receiving binary back electromotive force (BEMF) level signals associated with each phase winding, said BEMF level signals indicating whether the voltage level in the associated phase winding is above or below a threshold voltage level;
operating a state machine, said state machine sequentially advancing through a plurality of states, each state being based on the position and motion of the DC motor rotor and each state dictating which of the phase windings in the DC motor are supplied drive power;
detecting changes in the logic level of the BEMF level signals;
counting the amount of time that elapses between adjacent logic level changes in the BEMF level signals;
generating a switch time that is some fraction of the elapsed time between adjacent logic level changes; and
advancing the state machine when the switch time elapses following the most recent logic level change.
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Accused Products
Abstract
A digitally adaptive controller circuit for commutating a brushless, sensorless, DC motor in either of two directions adapted to receive digital back electromotive force (BEMF) detector signals. The digital circuit is driven by an input clock that is adjustable to configure the motor controller for use with a broad range of DC motors. The circuit includes commutational logic that decodes a current commutational state and a user-definable binary direction input into logic levels for digital control signals for controlling motor drive switches. The circuit also includes a signature analyzer to compare logic levels in the BEMF detector signals with expected logic levels based on an expected rotor position and direction of rotation. The digital circuit commutates the motor if the logic levels in the BEMF detector signals are at the expected logic levels. The digital circuit is compact and simple enough to be deployed onto a single programmable logic device.
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Citations
51 Claims
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1. A method of providing synchronous commutation to a plurality of phase windings in a brushless, sensorless, direct current (DC) motor comprising:
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receiving binary back electromotive force (BEMF) level signals associated with each phase winding, said BEMF level signals indicating whether the voltage level in the associated phase winding is above or below a threshold voltage level;
operating a state machine, said state machine sequentially advancing through a plurality of states, each state being based on the position and motion of the DC motor rotor and each state dictating which of the phase windings in the DC motor are supplied drive power;
detecting changes in the logic level of the BEMF level signals;
counting the amount of time that elapses between adjacent logic level changes in the BEMF level signals;
generating a switch time that is some fraction of the elapsed time between adjacent logic level changes; and
advancing the state machine when the switch time elapses following the most recent logic level change. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A digital motor controller configured to generate binary output signals to drive a plurality of phase windings in a brushless, sensorless, direct current (DC) motor comprising:
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an input means for receiving binary input signals corresponding to each phase winding, each binary input signal indicating whether the back electromotive force (BEMF) voltage level in the associated phase winding is above or below a zero-crossing voltage;
a signature analyzer means for identifying zero crossings in the BEMF levels in the phase windings by generating a zero-crossing signal change that indicates when a binary input signal changes from a first logic level to a second logic level; and
a delay means for counting the amount of time that elapses between the zero crossings and also for generating a switching signal change that is some fraction of the elapsed time between zero crossings;
wherein the switching signal change produces a change in the binary output signals so as to properly commutate the phase windings. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A digital circuit for commutating a brushless, sensorless, DC motor in either of two directions comprising:
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an input circuit adapted to receive digital back electromotive force (BEMF) detector signals, each signal indicating whether the voltage level in an associated phase winding in the DC motor is above a voltage threshold;
a commutational logic circuit adapted to generate digital control signals for controlling DC motor drive switches; and
a signature analyzer circuit configured to compare logic levels in the BEMF detector signals with expected logic levels based on an expected rotor position, wherein the digital circuit commutates the digital control signals if the logic levels in the BEMF detector signals are at the expected logic levels. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of controlling the operation of a three-phase brushless DC motor comprising:
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activating a current logic state in a state machine that is configured to cycle through a sequence of logic states, each logic state corresponding to a rotor position and travel;
transmitting digital drive signals that control the position of switches that, for each logic state, are adapted to push or pull two of the three windings to a voltage source;
pulling a first phase winding in the DC motor to a high voltage source;
pushing a second phase winding in the DC motor to a low voltage source;
detecting rising and falling voltage threshold crossing directions in back EMF levels of the third, undriven phase winding in the DC motor; and
comparing the rising or falling direction of a detected voltage threshold crossing with an anticipated rising or falling direction for the voltage threshold crossing, wherein if the direction of the detected voltage threshold crossing matches the anticipated direction for the voltage threshold crossing, generating a zero-crossing command, thereby initiating a logic state change in the state machine. - View Dependent Claims (26, 27, 28)
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29. A digital circuit for commutating a brushless, sensorless, DC motor comprising:
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an input circuit adapted to receive digital back electromotive force (BEMF) detector signals, each signal indicating whether the voltage level in an associated phase winding in the DC motor is above a voltage threshold;
a commutational logic circuit adapted to generate digital control signals for controlling power delivery to individual DC motor windings; and
a signature analyzer circuit configured to compare logic levels in the BEMF detector signals with expected logic levels based on an expected rotor position, wherein the digital circuit commutates the digital control signals if the logic levels in the BEMF detector signals are at the expected logic levels and wherein the digital circuit is deployable onto a programmable logic device that is disposed on a semiconductor on insulator device. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A digital motor controller to commutate a brushless, sensorless, DC motor comprising:
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an input circuit adapted to receive digital back electromotive force (BEMF) detector signals, each signal indicating whether the voltage level in an associated phase winding in the DC motor is above a voltage threshold;
a commutational logic circuit adapted to generate digital control signals for controlling power delivery to individual DC motor windings; and
a signature analyzer circuit configured to compare logic levels in the BEMF detector signals with expected logic levels based on an expected rotor position, wherein the motor controller is driven by a single input clock and said motor controller is configurable for use with different sensorless, brushless DC motors by adjusting the frequency of the input clock. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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Specification