Methods and apparatus for actuator control

1. A control circuit, capable of operating an actuator, comprising:

a drive circuit connected to the actuator and comprising:

a first output terminal; and

a second output terminal;

a digital signal processing circuit connected to the drive circuit and configured to:

measure waveform characteristics of a back electromotive force (EMF) induced by the actuator; and

compute a countermeasure value according to the back EMF;

a signal generator circuit connected between the digital signal processing circuit and the driver circuit and configured to generate an output signal; and

a selector circuit connected between the drive circuit and the digital processing circuit, wherein the selector circuit is responsive to the output signal and configured to selectively couple one of the first output terminal and the second output terminal to the digital signal processing circuit according to the output signal;

wherein the drive circuit is configured to operate the actuator according to the countermeasure value.

2. The control circuit according to claim 1 , wherein the digital signal processing circuit comprises:

a digital filter comprising:

a low pass filter; and

a high pass filter;

a waveform characteristic circuit configured to compute at least one of a resonance period and a peak-to-peak value of the back EMF; and

a DC computation circuit configured to compute a DC component of the back EMF.

3. The control circuit according to claim 2 , wherein the digital signal processing circuit is further configured to:

detect a maximum peak value;

detect a minimum peak value;

compute a trigger time value according to the resonance period; and

count a trigger time period that begins at one of: the detected maximum peak and the detected minimum peak, and ends at the trigger time value.

4. The control circuit according to claim 3 , wherein the digital signal processing circuit is further configured to generate an activation signal at the end of a trigger time period.

5. The control circuit according to claim 4 , wherein the drive circuit applies a drive signal corresponding to the computed countermeasure value to the actuator at the end of the trigger time period.

6. The control circuit according to claim 1 , wherein measuring waveform characteristics comprises:

computing a resonance period of the back EMF; and

computing a peak-to-peak value of the back EMF.

7. The control circuit according to claim 6 , wherein the countermeasure value is computed according to the peak-to-peak value of the back EMF.

8. A method for controlling an actuator, comprising:

receiving a back electromotive force (EMF) signal;

measuring a characteristic of the back EMF, wherein the characteristic comprises at least one of a peak-to-peak value and a resonance period;

computing a countermeasure value according to the measured characteristic, wherein the countermeasure value is a multiple of the peak-to-peak value; and

applying a drive signal, corresponding to the countermeasure value, to the actuator.

9. The method according to claim 8 , wherein measuring the characteristic of the back EMF comprises:

computing the peak-to-peak value of the back EMF comprising:

detecting a maximum peak value; and

detecting a minimum peak value; and

computing the resonance period of the back EMF.

10. The method according to claim 9 , wherein the countermeasure value is computed according to the computed peak-to-peak value.

11. The method according to claim 9 , further comprising computing a trigger time value according to the computed resonance period.

12. The method according to 11 , further comprising:

counting a trigger time period that ends at the trigger time value; and

generating an activation signal at the end of the trigger time period.

13. The method of claim 12 , wherein the trigger time period begins at one of: the detected maximum peak value and the detected minimum peak value.

14. The method according to claim 13 , wherein the drive signal is applied to the actuator at the end of the trigger time period.

15. The method according to claim 8 , further comprising:

selectively transmitting the back EMF signal according to a current of the actuator; and

computing a DC component of the back EMF.

16. A method for controlling an actuator, comprising:

detecting a first maximum peak of a back electromotive force (EMF) signal;

detecting a first minimum peak of the back EMF signal;

detecting and measuring a second maximum peak of the back EMF signal;

detecting and measuring a second minimum peak of the back EMF signal;

computing a peak-to-peak value based on the measured second maximum peak and the measured second minimum peak;

computing a countermeasure value according to the computed peak-to-peak value;

detecting a third maximum peak of the back EMF signal;

counting for a predetermined time, comprising starting counting when the third maximum peak is detected; and

applying a drive signal to the actuator at the end of the predetermined time, wherein the drive signal corresponds to the countermeasure value.

17. The method according to claim 16 , further comprising computing a resonance period of the back EMF.

18. The method according to claim 16 , wherein counting for the predetermined time further comprises:

ending counting at the trigger time value.

19. The method according to claim 18 , further comprising computing a trigger time value according to the computed resonance period.

20. The method according to claim 16 , further comprising generating an activation signal at the end of the predetermined time.