US-20260125103-A1 - DEAD-TIME COMPENSATION FOR BRUSHLESS DC MOTOR CONTROL

Abstract

A method of operating an inverter for a brushless direct current (BLDC) motor includes: driving a high-side switch to conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period in each of a plurality of operating periods; driving a low-side switch to a conductive state after a dead-time after the conductive period and to conduct current between the output node and a DC low node; receiving a duty cycle command; determining an adjusted duty cycle representing the conductive period as a portion of an operating period; determining a duty cycle difference signal as a difference between an initial duty cycle based on the duty cycle command, and the adjusted duty cycle; and determining a feedback duty offset signal based on the duty cycle difference signal. The adjusted duty cycle is computed based on the feedback duty offset signal.

Inventors

• Taibin Wang
• Mengnan Zuo
• Yongfei LIU
• Fei Lu

Assignees

• STEERING SOLUTIONS IP HOLDING CORPORATION

Dates

Publication Date

20260507

Application Date

20241118

Priority Date

20241107

Claims (20)

1. 1 . A method of operating an inverter for a brushless direct current (BLDC) motor, comprising: driving a high-side switch to a conductive state to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period in each of a plurality of operating periods; driving a low-side switch to a conductive state after a dead-time after the conductive period to selectively conduct current between the output node and a DC low node, wherein the DC low node and the DC high node have a DC voltage applied therebetween; receiving a duty cycle command; determining an adjusted duty cycle representing the conductive period as a portion of an operating period of the plurality of operating periods; determining a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command; and determining a feedback duty offset signal based on the duty cycle difference signal, wherein determining the adjusted duty cycle includes computing the adjusted duty cycle based on the feedback duty offset signal.
2. 2 . The method of claim 1 , wherein the inverter includes a plurality of phase drivers each configured to supply a corresponding DC power to the BLDC motor via a corresponding output node.
3. 3 . The method of claim 1 , wherein the initial duty cycle is equal to the duty cycle command.
4. 4 . The method of claim 1 , further including determining the initial duty cycle by applying a time delay to the duty cycle command.
5. 5 . The method of claim 1 , wherein determining the feedback duty offset signal further includes computing the feedback duty offset signal by a proportional-integral (PI) controller and based on the duty cycle difference signal.
6. 6 . The method of claim 1 , wherein determining the adjusted duty cycle based on the feedback duty offset signal further includes: determining a final duty offset signal based on the feedback duty offset signal; and adding the final duty offset signal to the duty cycle command to determine the adjusted duty cycle.
7. 7 . The method of claim 6 , wherein determining the final duty offset signal based on the feedback duty offset signal further includes: determining a polarity of a current between the output node and the BLDC motor; determining a prefeed duty offset signal based on the dead-time and the polarity of the current between the output node and the BLDC motor; and subtracting the feedback duty offset signal from the prefeed duty offset signal to determine the final duty offset signal.
8. 8 . The method of claim 7 , wherein determining the prefeed duty offset signal based on the dead-time and the polarity of the current between the output node and the BLDC motor further includes: determining if the polarity of the current between the output node and the BLDC motor is non-negative; setting the prefeed duty offset signal based on the dead-time in response to the polarity of the current between the output node and the BLDC motor being non-negative; and setting the prefeed duty offset signal to zero in response to the polarity of the current between the output node and the BLDC motor being negative.
9. 9 . The method of claim 1 , wherein the BLDC motor is configured to perform at least one of: applying an assist torque to a steering system of a vehicle, or controlling the steering system.
10. 10 . A method of operating an inverter for a brushless direct current (BLDC) motor, comprising: driving a high-side switch to a conductive state to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period in each of a plurality of operating periods; driving a low-side switch to a conductive state after a dead-time after the conductive period to selectively conduct current between the output node and a DC low node, wherein the DC low node and the DC high node have a DC voltage applied therebetween; receiving a duty cycle command; determining a current between the output node and the BLDC motor; determining a prefeed duty offset signal based on the current between the output node and the BLDC motor; determining an adjusted duty cycle based on the prefeed duty offset signal and the duty cycle command; and determining the conductive period based on the adjusted duty cycle and a duration of an operating period of the plurality of operating periods.
11. 11 . The method of claim 10 , wherein the inverter includes a plurality of phase drivers each configured to supply a corresponding DC power to the BLDC motor via a corresponding output node.
12. 12 . The method of claim 10 , wherein determining the prefeed duty offset signal further includes: determining a polarity of the current between the output node and the BLDC motor; and determining the prefeed duty offset signal based on the dead-time and the polarity of the current between the output node and the BLDC motor.
13. 13 . The method of claim 12 , wherein determining the prefeed duty offset signal further includes: determining if the polarity of the current between the output node and the BLDC motor is non-negative; setting the prefeed duty offset signal based on the dead-time in response to the polarity of the current between the output node and the BLDC motor being non-negative; and setting the prefeed duty offset signal to zero in response to the polarity of the current between the output node and the BLDC motor being negative.
14. 14 . The method of claim 10 , further including: determining a feedback duty cycle based on an on-time of the conductive period divided by a total time of a corresponding operating period of the plurality of operating periods; determining a duty cycle difference signal as a difference between an initial duty cycle and the feedback duty cycle, wherein the initial duty cycle is based on the duty cycle command; and determining a feedback duty offset signal based on the duty cycle difference signal, wherein determining the adjusted duty cycle based on the prefeed duty offset signal and the duty cycle command includes determining the adjusted duty cycle further based on the feedback duty offset signal.
15. 15 . The method of claim 14 , wherein determining the feedback duty offset signal further includes computing the feedback duty offset signal by a proportional-integral (PI) controller and based on the duty cycle difference signal.
16. 16 . The method of claim 14 , wherein determining the adjusted duty cycle based on the prefeed duty offset signal and the duty cycle command further includes: subtracting the feedback duty offset signal from the prefeed duty offset signal to determine a final duty offset signal; and adding the final duty offset signal to the duty cycle command to determine the adjusted duty cycle.
17. 17 . A system for operating a brushless direct current (BLDC) motor, comprising: a DC power supply including a DC high node and a DC low node, wherein the DC low node and the DC high node have a DC voltage therebetween; an inverter having a phase driver configured to apply a DC power to the BLDC motor via an output node connected to the BLDC motor, wherein the phase driver includes: a high-side switch configured to selectively conduct current between the DC high node and the output node, and a low-side switch configured to selectively conduct current between the output node and the DC low node; and a controller configured to: drive the high-side switch to a conductive state for a conductive period in each of a plurality of operating periods; drive the low-side switch to a conductive state after a dead-time after the conductive period; receive a duty cycle command; determine an adjusted duty cycle representing the conductive period as a portion of an operating period of the plurality of operating periods; determine a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command; and determine a feedback duty offset signal based on the duty cycle difference signal, wherein determining the adjusted duty cycle includes the controller computing the adjusted duty cycle based on the feedback duty offset signal.
18. 18 . The system of claim 17 , wherein the controller is further configured to: determine a final duty offset signal based on the feedback duty offset signal; and add the final duty offset signal to the duty cycle command to determine the adjusted duty cycle.
19. 19 . The system of claim 18 , wherein the controller is further configured to: determine a polarity of a current between the output node and the BLDC motor; determine a prefeed duty offset signal based on the dead-time and the polarity of the current between the output node and the BLDC motor; and subtract the feedback duty offset signal from the prefeed duty offset signal to determine the final duty offset signal.
20. 20 . The system of claim 17 , wherein the BLDC motor is configured to perform at least one of: applying an assist torque to a steering system of a vehicle, or controlling the steering system.

Description

CROSS-REFERENCE TO RELATED APPLICATION This patent application claims priority to CN patent application No. 202411585410.7, filed Nov. 8, 2024, which is incorporated herein by reference in its entirety. TECHNICAL FIELD This disclosure relates to control techniques for driving a brushless DC (BLDC) motor. More specifically, the present disclosure relates to control techniques to compensate of effects of dead-time in drivers for BLDC motors. BACKGROUND A vehicle, such as a car, truck, sport utility vehicle, crossover, mini-van, marine craft, aircraft, all-terrain vehicle, recreational vehicle, or other suitable forms of transportation, typically includes a steering system, such as an electronic power steering (EPS) system, a steer-by-wire (SbW) steering system, a hydraulic steering system, or other suitable steering system. The steering system of such a vehicle typically controls various aspects of vehicle steering including providing steering assist to an operator of the vehicle, controlling steerable wheels of the vehicle, and the like. Brushless DC (BLDC) motors have a variety of applications. One such application is for providing a steering torque in an EPS system or a SbW steering system. An inverter may be used to conduct current from a direct current (DC) supply to a winding of a BLDC motor by selectively conducting current between either of a DC positive node or a DC negative node to an output node. A dead-time may be used to prevent short circuiting that could otherwise result from both the DC positive node and the DC negative node being simultaneously connected to the output node. However, such dead-time can introduce undesirable effects, such as non-linear operation that can adversely impact control of BLDC motors. SUMMARY An aspect of the disclosed embodiments includes a method of operating an inverter for a brushless direct current (BLDC) motor. The method includes: driving a high-side switch to a conductive state to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period in each of a plurality of operating periods; driving a low-side switch to a conductive state after a dead-time after the conductive period to selectively conduct current between the output node and a DC low node, wherein the DC low node and the DC high node have a DC voltage applied therebetween; receiving a duty cycle command; determining an adjusted duty cycle representing the conductive period as a portion of an operating period of the plurality of operating periods; determining a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command; and determining a feedback duty offset signal based on the duty cycle difference signal. Determining the adjusted duty cycle includes computing the adjusted duty cycle based on the feedback duty offset signal. Another aspect of the disclosed embodiments includes a method of operating an inverter for a brushless direct current (BLDC) motor. The method includes: driving a high-side switch to a conductive state to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period in each of a plurality of operating periods; driving a low-side switch to a conductive state after a dead-time after the conductive period to selectively conduct current between the output node and a DC low node, wherein the DC low node and the DC high node have a DC voltage applied therebetween; receiving a duty cycle command; determining a current between the output node and the BLDC motor; determining a prefeed duty offset signal based on the current between the output node and the BLDC motor; determining an adjusted duty cycle based on the prefeed duty offset signal and the duty cycle command; and determining the conductive period based on the adjusted duty cycle and a duration of an operating period of the plurality of operating periods. Another aspect of the disclosed embodiments includes a system for operating a brushless direct current (BLDC) motor. The system for operating the BLDC motor includes: a DC power supply including a DC high node and a DC low node, wherein the DC low node and the DC high node have a DC voltage therebetween; an inverter having a phase driver configured to apply a DC power to the BLDC motor via an output node connected to the BLDC motor; and a controller. The phase driver includes: a high-side switch configured to selectively conduct current between the DC high node and the output node, and a low-side switch configured to selectively conduct current between the output node and the DC low node. The controller is configured to: drive the high-side switch to a conductive state for a conductive period in each of a plurality of operating periods; drive the low-side switch to a conductive state after a dead-time after the conductive period; receive a duty