Mirror element drive circuit with fault protection

• US 20050073786A1
• Filed: 09/13/2004
• Published: 04/07/2005
• Est. Priority Date: 11/08/2001
• Status: Abandoned Application

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Turnbull, Robert R., Friend, Timothy R., Meekhof, David A., Poe, G. Bruce, Mart, Gregory A.
• Application Number:
  US10/939,985
• Publication Number:
  US 20050073786A1
• Time in Patent Office: Days
• US Class Current: 361/93.100
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H02H 7/0851 for motors actuating a movable member between two end positions, e.g. detecting an end position or obstruction by overload signal

Abstract

In at least one embodiment a fault sense circuit includes a current sense device, a voltage sense device, a power sense device, a sub-combination thereof or a combination thereof. The current sense device is positioned to sense a drive current provided to a load by a drive circuit. The voltage sense device is coupled across the current sense device and receives a threshold signal at a first input and provides an output signal on an output whose value is dependent upon whether a sense signal at a second input is above or below the threshold signal. A level of the threshold signal changes in response to a voltage level of a power supply that supplies the drive current to the drive circuit.

Claims

1. A rearview mirror element drive circuit, comprising:

a controller configured to receive an actual element voltage signal, an actual element current signal and an element drive transistor power dissipation signal, said controller is further configured to detect a fault condition by comparing said actual element voltage signal to a desired voltage value, comparing said actual element current to a desired current value, comparing said element drive transistor power dissipation signal to a maximum power value, a sub-combination thereof or a combination thereof.

2. A rearview mirror element drive circuit as in claim 1 wherein said element drive circuit is temporarily disabled when a fault is detected for a period of time.

3. A rearview mirror element drive circuit as in claim 2 wherein said period of time is approximately 1.0 second or less.

4. A rearview mirror element drive circuit as in claim 2 wherein said period of time is approximately 400 ms.

5. A rearview mirror element drive circuit as in claim 2 wherein said element drive circuit is disabled for a second period of time prior to being automatically enabled.

6. A rearview mirror element drive circuit as in claim 5 wherein said second period of time is greater than approximately 2 seconds.

7. A rearview mirror element drive circuit as in claim 5 wherein said second period of time is approximately 4 seconds.

8. A rearview mirror element drive circuit as in claim 1 wherein said controller is configured as a micro controller.

9. A rearview mirror element drive circuit as in claim 1 configured as one of the devices selected from a group comprising:

class-D element drive circuits, switching element drive circuits, linear element drive circuits, analog element drive circuits and digital drive circuits.

10. A rearview mirror element drive circuit, comprising:

a controller configured to receive an actual element voltage signal, said controller is further configured to detect a fault condition by comparing said actual element voltage signal to a desired voltage value.

11. A rearview mirror element drive circuit as in claim 10 wherein said controller is further configured to receive an actual element current signal.

12. A rearview mirror element drive circuit as in claim 11 wherein said controller is further configured to detect a fault condition by comparing said actual element current signal to a desired current value.

13. A rearview mirror element drive circuit as in claim 10 wherein said controller is configured to receive an element drive transistor power dissipation signal.

14. A rearview mirror element drive circuit as in claim 13 wherein said controller is further configured to detect a fault condition by comparing said element drive transistor power dissipation signal to a maximum power value.

15. A rearview mirror element drive circuit as in claim 10 wherein said element drive circuit is temporarily disabled when a fault is detected for a period of time.

16. A rearview mirror element drive circuit as in claim 15 wherein said period of time is approximately 1.0 second or less.

17. A rearview mirror element drive circuit as in claim 15 wherein said period of time is approximately 400 ms.

18. A rearview mirror element drive circuit as in claim 15 wherein said element drive circuit is disabled for a second period of time prior to being automatically enabled.

19. A rearview mirror element drive circuit as in claim 18 wherein said second period of time is greater than approximately 2 seconds.

20. A rearview mirror element drive circuit as in claim 18 wherein said second period of time is approximately 4 seconds.

21. A rearview mirror element drive circuit as in claim 10 wherein said controller is configured as a micro controller.

22. A rearview mirror element drive circuit as in claim 10 configured as one of the devices selected from a group comprising:

class-D element drive circuits, switching element drive circuits, linear element drive circuits, analog element drive circuits and digital drive circuits.

23. A rearview mirror element drive circuit, comprising:

a controller configured to receive an actual element voltage signal and an actual element current signal, said controller is further configured to detect a fault condition by comparing said actual element voltage signal to a desired voltage value and by comparing said actual element current signal to an actual element current signal.

24. A rearview mirror element drive circuit as in claim 23 a controller configured to receive an element drive transistor power dissipation signal.

25. A rearview mirror element drive circuit as in claim 24 wherein said controller is further configured to detect a fault condition by comparing said element drive transistor power dissipation signal to a maximum power value.

26. A rearview mirror element drive circuit as in claim 23 wherein said element drive circuit is temporarily disabled when a fault is detected for a period of time.

27. A rearview mirror element drive circuit as in claim 26 wherein said period of time is approximately 1.0 second or less.

28. A rearview mirror element drive circuit as in claim 26 wherein said period of time is approximately 400 ms.

29. A rearview mirror element drive circuit as in claim 26 wherein said element drive circuit is disabled for a second period of time prior to being automatically enabled.

30. A rearview mirror element drive circuit as in claim 29 wherein said second period of time is greater than approximately 2 seconds.

31. A rearview mirror element drive circuit as in claim 29 wherein said second period of time is approximately 4 seconds.

32. A rearview mirror element drive circuit as in claim 23 wherein said controller is configured as a micro controller.

33. A rearview mirror element drive circuit as in claim 23 configured as one of the devices selected from a group comprising:

class-D element drive circuits, switching element drive circuits, linear element drive circuits, analog element drive circuits and digital drive circuits.

34. A rearview mirror element drive circuit, comprising:

a controller configured to receive an actual element current signal, said controller is further configured to detect a fault condition by comparing said actual element current signal to a desired current value.

35. A rearview mirror element drive circuit as in claim 34 wherein said controller is further configured to receive an actual element voltage signal.

36. A rearview mirror element drive circuit as in claim 35 wherein said controller is further configured to detect a fault condition by comparing said actual element voltage signal to a desired voltage value.

37. A rearview mirror element drive circuit as in claim 34 a controller configured to receive an element drive transistor power dissipation signal.

38. A rearview mirror element drive circuit as in claim 37 wherein said controller is further configured to detect a fault condition by comparing said element drive transistor power dissipation signal to a maximum power value.

39. A rearview mirror element drive circuit as in claim 34 wherein said element drive circuit is temporarily disabled when a fault is detected for a period of time.

40. A rearview mirror element drive circuit as in claim 39 wherein said period of time is approximately 1.0 second or less.

41. A rearview mirror element drive circuit as in claim 39 wherein said period of time is approximately 400 ms.

42. A rearview mirror element drive circuit as in claim 39 wherein said element drive circuit is disabled for a second period of time prior to being automatically enabled.

43. A rearview mirror element drive circuit as in claim 42 wherein said second period of time is greater than approximately 2 seconds.

44. A rearview mirror element drive circuit as in claim 42 wherein said second period of time is approximately 4 seconds.

45. A rearview mirror element drive circuit as in claim 34 wherein said controller is configured as a micro controller.

46. A rearview mirror element drive circuit as in claim 34 configured as one of the devices selected from a group comprising:

class-D element drive circuits, switching element drive circuits, linear element drive circuits, analog element drive circuits and digital drive circuits.

47. A rearview mirror element drive circuit, comprising:

a controller configured to receive an element drive transistor power dissipation signal, said controller is further configured to detect a fault condition by comparing said element drive transistor power dissipation signal to a desired voltage value.

48. A rearview mirror element drive circuit as in claim 47 wherein said controller is further configured to receive an actual element current signal.

49. A rearview mirror element drive circuit as in claim 48 wherein said controller is further configured to detect a fault condition by comparing said actual element current signal to a desired current value.

50. A rearview mirror element drive circuit as in claim 47 a controller configured to receive an actual element voltage signal.

51. A rearview mirror element drive circuit as in claim 50 wherein said controller is further configured to detect a fault condition by comparing said actual element voltage signal to a desired voltage value.

52. A rearview mirror element drive circuit as in claim 47 wherein said element drive circuit is temporarily disabled when a fault is detected for a period of time.

53. A rearview mirror element drive circuit as in claim 52 wherein said period of time is approximately 1.0 second or less.

54. A rearview mirror element drive circuit as in claim 52 wherein said period of time is approximately 400 ms.

55. A rearview mirror element drive circuit as in claim 52 wherein said element drive circuit is disabled for a second period of time prior to being automatically enabled.

56. A rearview mirror element drive circuit as in claim 55 wherein said second period of time is greater than approximately 2 seconds.

57. A rearview mirror element drive circuit as in claim 55 wherein said second period of time is approximately 4 seconds.

58. A rearview mirror element drive circuit as in claim 47 wherein said controller is configured as a micro controller.

59. A rearview mirror element drive circuit as in claim 47 configured as one of the devices selected from a group comprising:

class-D element drive circuits, switching element drive circuits, linear element drive circuits, analog element drive circuits and digital drive circuits.