Stepper motor drive and stall detection circuit

Patent metadata

Field	Value
Publication number	US-10153718-B2
Application number	US-201715435912-A
Country	US
Kind code	B2
Filing date	Feb 17, 2017
Priority date	Feb 17, 2017
Publication date	Dec 11, 2018
Grant date	Dec 11, 2018

Abstract

A first differential amplifier output drives a first winding of a stepper motor and a second differential amplifier output drives a second winding of the stepper motor. Inputs of the first and second differential amplifiers receive input drive signals generated by either a digital to analog converter or a pulse width modulator, where the input drive signals are phase offset sinusoids. Current flowing through a stepper motor winding is sensed to generate a current sense signal. A stall sensing circuit processes the current sense signal to determine whether the stepper motor has stalled by: taking a first derivative of the current sense signal to generate a first derivative signal; taking a second derivative of the current sense signal to generate a second derivative signal; and processing one or more of the current sense signal, the first derivative signal and the second derivative signal to detect a stepper motor stall condition.

First claim

What is claimed is:

1. A circuit for driving a first winding and a second winding of a stepper motor, comprising:
a first differential amplifier circuit having a first input, a second input and an output, said output of the first differential amplifier circuit configured to be coupled to a first terminal of the first winding of the stepper motor;
a second differential amplifier circuit having a first input, a second input and an output, said output of the second differential amplifier circuit configured to be coupled to a first terminal of the second winding of the stepper motor;
a digital to analog converter circuit configured to generate a first input drive signal coupled to the first input of the first differential amplifier circuit and generate a second input drive signal coupled to the first input of the second differential amplifier circuit; and
a stall sensing circuit configured to receive the current sense signal and determine whether the stepper motor has stalled by:
taking a first derivative of the current sense signal to generate a first derivative signal; and
processing the current sense signal and the first derivative signal to detect a stepper motor stall condition.

2. The circuit of claim 1 , wherein the first and second input drive signals have one of a sinusoidal shape or square wave shape that are offset from each other in phase.

3. The circuit of claim 2 , wherein a second terminal of each of the first and second windings of the stepper motor is coupled to ground through a resistor.

4. The circuit of claim 1 , wherein each of the first and second differential amplifier circuits includes a circuit configured to generate a reference voltage for application to the second input.

5. The circuit of claim 4 , wherein each of the first and second differential amplifier circuits further includes a feedback resistor coupled to form a feedback path from the output to the first input.

6. The circuit of claim 5 , wherein each of the first and second differential amplifier circuits has a first power supply input coupled to receive a positive supply voltage and a second power supply input coupled to receive a negative supply voltage.

7. The circuit of claim 1 , wherein the stall sensing circuit is further configured to determine whether the stepper motor has stalled by:
taking a second derivative of the current sense signal to generate a second derivative signal; and
processing the current sense signal, the first derivative signal and the second derivative signal to detect a stepper motor stall condition.

8. The circuit of claim 1 , wherein the stall sensing circuit comprises a sense resistor coupled between ground and a second terminal of one of the first and second windings of the stepper motor.

9. A circuit for driving a first winding and a second winding of a stepper motor, comprising:
a first differential amplifier circuit having a first input, a second input and an output, said output of the first differential amplifier circuit configured to be coupled to a first terminal of the first winding of the stepper motor, and including a capacitor coupled to form a feedback path from the output of the first differential amplifier circuit to the first input of the first differential amplifier circuit;
a second differential amplifier circuit having a first input, a second input and an output, said output of the second differential amplifier circuit configured to be coupled to a first terminal of the second winding of the stepper motor, and including a capacitor coupled to form a feedback path from the output of the second differential amplifier circuit to the first input of the second differential amplifier circuit; and
a pulse width modulation circuit configured to generate a first input drive signal coupled to the first input of the first differential amplifier circuit and generate a second input drive signal coupled to the first input of the second differential amplifier circuit.

10. The circuit of claim 9 , wherein the capacitors in the feedback paths of the first and second differential amplifier circuits provide first order filtering of the first and second input drive signals from the pulse width modulation circuit.

11. The circuit of claim 9 , wherein pulse widths of the first and second input drive signals sinusoidally vary over time offset in phase.

12. The circuit of claim 11 , wherein a second terminal of each of the first and second windings of the stepper motor is coupled to ground through a resistor.

13. The circuit of claim 9 , wherein each of the first and second differential amplifier circuits includes a circuit configured to generate a reference voltage for application to the second input.

14. The circuit of claim 13 , wherein each of the first and second differential amplifier circuits further includes a feedback resistor coupled in parallel with the capacitor.

15. The circuit of claim 14 , wherein each of the first and second differential amplifier circuits has a first power supply input coupled to receive a positive supply voltage and a second power supply input coupled to receive a negative supply voltage.

16. The circuit of claim 9 , further comprising:
a current sensing circuit configured to sense current flowing through the first winding of the stepper motor and output a current sense signal; and
a stall sensing circuit configured to receive the current sense signal and determine whether the stepper motor has stalled by:
taking a first derivative of the current sense signal to generate a first derivative signal; and
processing the current sense signal and the first derivative signal to detect a stepper motor stall condition.

17. The circuit of claim 16 , wherein the stall sensing circuit is further configured to determine whether the stepper motor has stalled by:
taking a second derivative of the current sense signal to generate a second derivative signal; and
processing the current sense signal, the first derivative signal and the second derivative signal to detect a stepper motor stall condition.

18. The circuit of claim 16 , wherein the current sensing circuit comprises a sense resistor coupled between ground and a second terminal of one of the first and second windings of the stepper motor.

19. A circuit, comprising:
a current sensing circuit configured to sense current flowing through a winding of a stepper motor and output a current sense signal; and
a stall sensing circuit configured to receive the current sense signal and determine whether the stepper motor has stalled by:
taking a derivative of the current sense signal to generate a derivative signal; and
processing the current sense signal and the derivative signal to detect a stepper motor stall condition.

20. The circuit of claim 19 , wherein the derivative is a first derivative.

21. The circuit of claim 20 , wherein the determination of whether the stepper motor has stalled further comprises taking a Fast Fourier Transform (FFT) of a first derivative signal and the processing is processing of the FFT to detect high frequency fluctuations of the current sense signal to detect a stepper motor stall condition.

22. The circuit of claim 20 , wherein the processing is processing a first derivative signal to detect a difference between minimum and maximum values of the first derivative signal within a window to detect a stepper motor stall condition.

23. The circuit of claim 20 , wherein processing is processing a first derivative signal to detect zero

Assignees

• St Microelectronics Inc

Inventors

• Byers Ian

Classifications

• H02P23/0077

  Characterised by the use of a particular software algorithm · CPC title

• H02P8/08 Primary

  Determining position before starting · CPC title

• H02P8/04 Primary

  Arrangements for starting · CPC title

• H02P8/36

  Protection against faults, e.g. against overheating or step-out; Indicating faults · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title