Sensorless brushless direct current (BLDC) motor position control

Patent metadata

Field	Value
Publication number	US-9887653-B2
Application number	US-201615163943-A
Country	US
Kind code	B2
Filing date	May 25, 2016
Priority date	May 25, 2016
Publication date	Feb 6, 2018
Grant date	Feb 6, 2018

Abstract

Described embodiments provide circuits, systems and methods for controlling operation of brushless direct current motors that include a plurality of windings. A gate driver provides control signals to switching elements that control a voltage applied to each of the windings of the motor. A zero crossing detector detects zero crossings of a voltage applied to the windings and transitions a zero crossing signal between a first logic level and a second logic level based on the detected zero crossings. A position estimator estimates an angular position of the motor, and counts in a first direction based on the first logic level of the zero crossing signal, and in a second direction based on the second logic level of the zero crossing signal. An observer determines a value of the counter after an elapsed time, and generates an angular position signal based upon the value of the counter.

First claim

We claim:

1. An electronic circuit for controlling operation of a brushless direct current (DC) motor having a plurality of windings, the electronic circuit comprising:
a gate driver for providing an associated control signal to each of one or more switching elements coupled to the electronic circuit, the one or more switching elements controlling a voltage applied to each of the plurality of windings of the motor;
a controller to generate a speed signal based upon a received frequency demand signal and provide the speed signal to the gate driver;
a zero crossing detector for detecting a zero crossing of a voltage applied to at least one of the windings, the zero crossing detector configured to transition a zero crossing signal between a first logic level and a second logic level based on the detected zero crossing;
a position estimator for estimating an angular position of the motor, the position estimator comprising a counter configured to count in a first predetermined direction based on the first logic level of the zero crossing signal, and configured to count in a second predetermined direction based on the second logic level of the zero crossing signal; and
an observer for determining a value of the counter after a predetermined elapsed time, the observer configured to generate an angular position signal based, at least in part, upon the determined value of the counter, wherein the observer is configured to generate a frequency signal based, at least in part, upon the determined value of the counter and provide the frequency signal to the controller, wherein the controller is configured to generate the speed signal based upon the received frequency demand signal and the frequency signal, wherein the observer is configured to receive at least one adjustment parameter, the observer configured to generate at least one of the angular position signal and the frequency signal based upon the determined value of the counter and the at least one adjustment parameter, and wherein the at least one adjustment parameter comprises a frequency adjustment parameter, K I , and wherein the observer is configured to generate the frequency signal by multiplying the determined value of the counter by the frequency adjustment parameter, added to a previous value of the frequency signal.

2. The electronic circuit of claim 1 , wherein the one or more switching elements are coupled in a half-bridge circuit comprising at least one branch, each branch associated with a given one of the plurality of windings, each branch comprising a first switching element coupled between a high supply voltage and a switching node of the given winding, and a second switching element coupled between the switching node and a low supply voltage.

3. The electronic circuit of claim 1 , wherein the gate driver receives the angular position signal from the observer, the gate driver configured to generate the control signal for each switching element based, at least in part, upon the angular position signal and the speed signal.

4. The electronic circuit of claim 1 , wherein the at least one adjustment parameter comprises a position adjustment parameter, K P , and wherein the observer is configured to generate the angular position signal by multiplying the determined value of the counter by the position adjustment parameter, added to a previous value of the angular position signal and added to the frequency signal.

5. The electronic circuit of claim 4 , wherein the angular position signal is determined by: θ(n)=θ(n−1)+(K P ·ERROR)+FREQ(n), and wherein the frequency signal is determined by: FREQ(n)=FREQ(n−1)+(K I ·ERROR), wherein θ(n) is a current value of the angular position signal, θ(n−1) is the previous value of the angular position signal, K P is the position adjustment parameter, ERROR is the determined value of the counter, FREQ(n) is a current value of the frequency signal, FREQ(n−1) is the previous value of the frequency signal, and K I is the frequency adjustment parameter.

6. The electronic circuit of claim 4 , wherein the frequency adjustment parameter adjusts a slope of the frequency signal, and wherein the position adjustment parameter adjusts a slope of the angular position signal.

7. The electronic circuit of claim 1 , wherein the at least one adjustment parameter is determined based on one or more characteristics of the motor.

8. The electronic circuit of claim 7 , wherein the one or more characteristics comprise a response time of the motor.

9. The electronic circuit of claim 1 , wherein the counter comprises an up/down counter configured to increment the value of the counter based on the first logic level of the zero crossing signal, and decrement the value of the counter based on the second logic level of the zero crossing signal, wherein the first logic level is a logic high level, and the second logic level is a logic low level.

10. The electronic circuit of claim 9 , wherein, if the determined value of the counter is non-zero, the observer is configured to adjust the frequency signal.

11. The electronic circuit of claim 10 , wherein if the determined value of the counter is a positive value, the frequency signal is increased, and wherein if the determined value of the counter is a negative value, the frequency signal is decreased.

12. The electronic circuit of claim 9 , wherein the controller is configured to employ the frequency signal as a reference signal to compare to the received frequency demand signal to run the motor at a substantially constant frequency.

13. The electronic circuit of claim 1 , wherein the electronic circuit does not employ blanking time to determine the angular position of the motor.

14. The electronic circuit of claim 1 , wherein the electronic circuit does not receive signals from one or more position sensors of the motor.

15. The electronic circuit of claim 1 , wherein the zero crossing detector detects a zero crossing of a voltage applied to all of the windings.

16. The electronic circuit of claim 1 , wherein the one or more switching elements each comprise a field effect transistor.

17. The electronic circuit of claim 1 , wherein the electronic circuit is implemented in an integrated circuit.

18. The electronic circuit of claim 17 , wherein the one or more switching elements are internal to the integrated circuit.

19. The electronic circuit of claim 17 , wherein the one or more switching elements are external to the integrated circuit.

20. The electronic circuit of claim 1 , further comprising:
a center tap averaging block coupled to the zero crossing detector and a voltage applied to at least one of the windings, wherein the center tap averaging block generates an approximate center tap voltage of the windings, and wherein the zero crossing detector detects a zero crossing based upon the approximate center tap voltage.

21. An electronic circuit for driving a load, the electronic circuit comprising:
a gate driver for providing an associated control signal to each of one or more switching elements coupled to the electronic circuit and the load, the one or more switching elements controlling a voltage applied to the load;
a controller to generate a speed signal based upon a received frequency demand signal and provide the speed signal to the gate driver;
a zero crossing detector for detecting a zero crossing of a voltage applied to the load, the zero crossing detector configured to transition a zero crossing signal between a first logic level and a second logic level based on the detected zero cros

Assignees

• Allegro Microsystems Llc

Inventors

• Ross Thomas
• Allegrini Gianluca
• Li Yi

Classifications

• H02P6/12

  Monitoring commutation; Providing indication of commutation failure · CPC title

• H02P6/182 Primary

  using back-emf in windings · CPC title

• H02P6/085

  in a bridge configuration · CPC title

• H02P6/157

  wherein the commutation is function of electro-magnetic force [EMF] · CPC title