Circuit and method for improved back electromotive force detection
AssigneeSTMicroelectronics S.r.l.
InventorJianwen Shao
Life of this patent
Estimating the term…
Abstract
A circuit and method provide a back EMF signal that represents a back EMF voltage induced in a coil of a brushless motor. In one embodiment of the invention, the circuit includes an input node operable to receive a tap voltage from the coil, and a network coupled to the input node and operable to generate the back EMF signal by removing a predetermined offset voltage from the tap voltage. Such a circuit provides a signal that more accurately indicates a zero crossing than existing circuits for controlling a sensorless brushless motor.
Claims19
A circuit for providing a back EMF signal that represents a back EMF voltage induced in a coil of a brushless motor, the circuit comprising:
- an input node operable to receive a tap voltage from the coil;
- and
- a network coupled to the input node and operable to generate the back EMF signal by removing a predetermined offset voltage from the tap voltage.
A driver circuit for a sensorless brushless motor having a plurality of coils each inducing a respective back EMF voltage, the driver comprising:
- a plurality of input nodes each operable to receive a tap voltage from a respective coil;
- a plurality of networks each coupled to a respective input node and operable to generate a respective back EMF signal by removing a predetermined offset voltage from the corresponding tap voltage;
- and
- a zero-crossing detector operable to receive the back EMF signals and determine there from when zero crossings of the respective back EMF voltages occur.
A sensorless brushless motor assembly, comprising:
- a sensorless brushless motor having a plurality of coils each generating a back EMF voltage during a respective floating period;
- and
- a motor driver circuit including
- a plurality of input nodes each operable to receive a tap voltage from a respective one of the coils;
- a plurality of networks each coupled to a respective one of the input nodes and operable to generate a respective back EMF signal by removing a predetermined offset voltage from the corresponding tap voltage;
- and
- a zero-crossing detector operable to receive the back EMF signals and to determine when the zero crossings of the back EMF voltages occur.
A method of providing a back EMF signal that represents a back EMF voltage induced in a coil of a brushless motor, comprising:
- receiving a tap voltage from the coil;
- and
- generating the back EMF signal equal to the tap voltage minus a predetermined offset voltage.
A method of advancing a sensorless brushless motor having a plurality of coils, comprising:
- receiving a tap voltage from one of the coils while the coil is floating;
- removing a predetermined offset voltage from the tap voltage to generate a back EMF signal that represents a back EMF voltage induced in the floating coil;
- detecting a zero crossing of the back EMF voltage from the back EMF signal;
- and
- advancing the motor a step in a commutation sequence in response to detection of the zero crossing.
A circuit for providing a back EMF signal that represents a back EMF voltage induced in a coil of a brushless motor, the circuit comprising:
- means for receiving a tap voltage from the coil;
- and
- means for generating the back EMF signal by removing a predetermined offset voltage from the tap voltage.
Dependencies are inferred from the claim text.