Sensorless control of two-phase brushless DC motor
AssigneeAtmel Corporation
InventorJacob Lassen
Life of this patent
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Abstract
A motor control system for a two-phase brushless DC motor uses measured EMF voltage from the passive set of stator coils to control commutation. A microcontroller receives the EMF voltage measurement and compares it to a threshold voltage value, which may be speed-dependent for advance commutation at high motor speeds. A match of the EMF voltage measurement with the threshold value triggers commutation of the drive to the opposite set of stator coils. The microcontroller also has an up-down counter timer whose count value is compared to an external speed reference. Each match of the count value triggers a transition in a pulse-width modulated (PWM) drive signal. The duty cycle of the PWM signal establishes an average drive voltage that controls motor speed.
Claims22
An integrated circuit particularly configured for control of a two-phase brushless DC motor having a rotor with permanent magnet poles and a stator with two sets of stator coils coupled to a drive circuit, and with the drive circuit in switching relation to the sets of stator coils to alternately energize the respective sets, of stator coils, the integrated circuit comprising:
- EMF circuitry coupled to receive and sample an electromotive force (EMF) signal corresponding to an EMF voltage generated in response to rotor motion upon whichever set of stator coils is not energized at any given sampling time;
- and
- commutation control circuitry responsive to the sampled EMF signal to provide switching control signals to the drive circuit, such that commutation times are determined by the EMF voltage on the non-energized stator coils.
A motor control system, comprising:
- a two-phase brushless DC motor having a rotor with permanent magnet poles and having a stator with two sets of stator coils configured to alternately magnetically drive said rotor;
- a drive circuit coupled in switching relation to said sets of stator coils such that in successive commutation time intervals an alternately selected one of said sets of stator coils is coupled to and energized by a motor power supply voltage, the other unconnected set of stator coils constituting passive coils responsive to rotor motion to generate an electromotive force (EMF) voltage on said passive coils;
- and
- a microcontroller coupled to receive and measure the EMF voltage on the passive coils and to determine commutation time intervals therefrom, the microcontroller also coupled to said drive circuit to control the switching of the selection of the energized set of stator coils.
A motor control system, comprising:
- a two-phase brushless DC motor having a rotor with permanent magnet poles and having two sets of stator coils configured to alternately magnetically drive said rotor;
- a drive circuit coupled in switching relation to said sets of stator coils such that in successive commutation time intervals an alternately selected one of said sets of stator coils is coupled to and energized by a motor power supply voltage, the other unconnected set of stator coils constituting passive coils responsive to rotor motion to generate an electromotive force (EMF) voltage on said passive coils;
- and
- a microcontroller including an analog-to-digital conversion circuit block coupled to receive and measure the EMF voltage on the passive coils and to convert it to digital form for comparison with a speed-dependent threshold value, the microcontroller further configured to establish commutation times based on said comparison of the measured EMF voltage with the speed-dependent threshold value, the microcontroller also including an up-down counter timer circuit, the microcontroller coupled to receive an external motor speed reference and convert it to compare count value for comparison with a count by said timer, each match of the count with the speed reference-dependent compare count value triggering a pulse transition of a pulse-width modulated (PWM) drive control signal, the PWM motor drive control signal with a duty cycle dependent upon the external motor speed reference, the PWM motor drive control signal coupled to the drive circuit to control the energized set of stator coils.
Dependencies are inferred from the claim text.