Converged motor drive control for brushless dc motor
AssigneeTexas Instruments Incorporated
InventorsZachery S. Buckley, Seil Oh
Life of this patent
Estimating the term…
Abstract
A system includes a timer to determine a time interval between successive commutation state changes of a brushless direct current (BLDC) motor. A speed calculator computes a speed of the BLDC motor based on the time interval. A threshold calculator determines a threshold based on the computed speed, the threshold specifying a calculation of back electromotive force (BEMF) and mutual inductance of the BLDC motor at a next state change of the BLDC motor. A state change trigger commands the next state change based on a measured voltage associated with a floating phase of the BLDC motor relative to the threshold.
Claims19
A system comprising:
- a timer circuit having a state change input adapted to be coupled to a brushless direct current motor, and having an elapsed time output;
- a speed circuit having an elapsed time input coupled to the elapsed time output, and having a speed output;
- a threshold circuit having a speed input and a state threshold output, the threshold circuit including a back electromotive force calculator and a mutual inductance calculator;
- and
- a trigger circuit having a comparator input coupled to the state threshold output, and having a trigger output.
A brushless direct current motor system, comprising:
- a motor controller adapted to be coupled to phase windings of the brushless direct current motor, the motor controller includes:
- a drive state controller coupled to the phase windings of the brushless direct current motor, the controller providing a variable commutation threshold voltage that varies based on a speed of the brushless direct current motor, the variable commutation threshold voltage specifying a back electromotive force and mutual inductance for a floating phase of the brushless direct current motor at a next commutation state change of the brushless direct current motor, the drive state controller having a trigger output to command the next commutation state change based on a comparison of a measured voltage for the floating phase of the brushless direct current motor to the threshold voltage;
- and
- a driver control having a trigger input coupled to the trigger output and having an control output to control current supplied to phases of the brushless direct current motor current.
A method comprising:
- detecting commutation state changes for a brushless direct current motor;
- calculating a speed of the brushless direct current motor based on a time interval between successive commutation state changes of the brushless direct current motor;
- calculating a variable threshold voltage based on the computed speed, the threshold voltage representing a back electromotive force and a mutual inductance for a floating phase winding of the brushless direct current motor at a next commutation state change;
- and
- comparing the threshold voltage to a measured voltage for the floating phase winding of the brushless direct current motor to determine the next commutation state change.
Dependencies are inferred from the claim text.