Apparatus and method for charging and discharging a capacitor

• US 20040090798A1
• Filed: 07/17/2003
• Published: 05/13/2004
• Est. Priority Date: 09/05/2002
• Status: Active Grant

• Current Assignee: Parker Intangibles LLC (Parker-Hannifin Corporation)
• Original Assignee: Viking Technologies, L.C.
• Inventors: Vandersluis, Donald, Oudshoorn, Mark
• Granted Patent: US 6,979,933 B2
• Time in Patent Office: Days
• US Class Current: 363/1
• CPC Class Codes: H02M 3/3353 having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
• CPC Class Codes: H02M 3/338 in a self-oscillating arrangement H02M3/337 takes precedence
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

An apparatus for electrically stimulating a smart material includes a controllable power source for charging the smart material and/or switching circuitry for discharging the smart material. The controllable power source includes a regulated DC to DC converter having controllable drive circuitry associated therewith. The drive circuitry can be self-oscillating through associated feedback means. The switching circuitry can be responsive to one or more control signals.

Claims

1. An apparatus comprising:

a smart material actuator, and

at least one of a controllable power source for charging the smart material actuator and a switching circuitry for discharging the smart material actuator.

2. The apparatus of claim 1, wherein the controllable power source includes a DC-to-DC converter having a transformer including primary and secondary windings and controllable drive circuitry coupled to the primary winding of the transformer for generating drive signals 180 degrees out of phase with one another.

3. The apparatus of claim 2, wherein the controllable drive circuitry is self-oscillating.

4. The apparatus of claim 3, wherein the self-oscillating drive circuitry further comprises feedback means for delivering a feedback signal, the feedback means including push-pull circuitry and an auxiliary winding associated with the transformer.

5. The apparatus of claim 4, wherein the push-pull circuitry includes a pair of NPN transistors.

6. The apparatus of claim 2 further comprising a rectifier associated with the secondary winding of the transformer for generating a DC voltage from an AC signal associated with the secondary winding.

7. The apparatus of claim 2 further comprising noise reduction circuitry coupled to the secondary winding of the transformer for filtering noise generated by the controllable drive circuitry.

8. The apparatus of claim 7, wherein the noise reduction circuitry includes a bead inductor and a bypass capacitor.

9. The apparatus of claim 3 further comprising means for enabling the self-oscillating driver.

10. The apparatus of claim 9, wherein the enabling means includes voltage feedback means for feeding back voltage.

11. The apparatus of claim 10, wherein the voltage feedback means includes a Zener diode.

12. The apparatus of claim 4 further comprising means for biasing the push-pull circuitry.

13. The apparatus of claim 12, wherein the biasing means includes a voltage divider.

14. The apparatus of claim 2, wherein the DC-to-DC converter further comprises means for reverse polarity protection associated with an input to the DC-to-DC converter.

15. The apparatus of claim 14, wherein the reverse polarity protection means is a diode.

16. The apparatus of claim 1, wherein the switching circuitry is responsive to a single controlled input signal.

17. The apparatus of claim 1, wherein the switching circuitry is responsive to one of a plurality of controlled input signals.

18. The apparatus of claim 1, wherein a rate of discharge is determined by an impedance of the switching circuitry.

19. The apparatus of claim 1, wherein a rate of charge is determined by an impedance of the controllable power source.

20. The apparatus of claim 2, wherein the transformer is of wound core design.

21. The apparatus of claim 2, wherein the transformer is of LTCC design.

22. An apparatus for driving a smart material actuator comprising:

a controllable power source connectible to the smart material actuator for charging the smart material actuator; and

a switching circuitry coupled between the controllable power source and the smart actuator for discharging the smart material actuator in response to removal of a power source.

29. The method of claim 22, further including the step of determining the rate of discharge by an impedance of the switching circuitry.

30. The method of claim 22 further including the step of determining the rate of charge by an impedance of the controllable power source.

23. A method for driving a smart material actuator comprising at least one of the steps of:

charging the smart material actuator with a controllable power source connectible to the smart material actuator; and

discharging the smart material actuator in response to removal of a power source with a switching circuitry coupled between the controllable power source and the smart actuator.

24. The method of claim 23 further comprising the step of generating drive signals 180 degrees out of phase with one another where the controllable power source includes a DC to DC converter having a transformer including primary and secondary windings and controllable drive circuitry coupled to the primary winding of the transformer.

25. The method of claim 24 wherein the controllable drive circuitry is self-oscillating.

26. The method of claim 25 further comprising the step of delivering a feedback signal derived from push-pull circuitry and an auxiliary winding associated with the transformer.

27. The method of claim 23 further including the step of generating a DC voltage from an AC signal associated with the secondary winding of the transformer by using a rectifier associated with the secondary winding.

28. The method of claim 23 further including the step of reducing noise generated by the controllable drive circuitry by coupling noise reduction circuitry to the secondary winding of the transformer.