Overcharge prevention method, changing circuit, electronic device and timepiece

• US 6,373,790 B1
• Filed: 02/23/2000
• Issued: 04/16/2002
• Est. Priority Date: 05/18/1998
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Fujisawa, Teruhiko
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): GOODWIN, JEANNE M
• Application Number:
  US09/462,798
• Time in Patent Office: 783 Days
• Field of Search: 368/203, 368/204, 320/134, 320/132, 320/162, 320/137, 320/166, 363/52, 363/53, 363/56.02, 363/56.03, 363/127, 363/132, 327/494, 327/495-498, 327/531, 327/533, 327/540, 327/543, 327/587, 327/588
• US Class Current: 368/204
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02M 7/219 in a bridge configuration

Abstract

In an overcharge prevention method for a voltage storage element connected to a bridge rectifier circuit which includes a first switching section connected between one input terminal supplied with an AC voltage and a first power source line, a second switching section connected between the other input terminal supplied with the AC voltage and the first power source line, a third switching section connected between the one input terminal and a second power source line, and a fourth switching section connected between the other input terminal and the second power source line, both the first and second switching sections or both the third and fourth switching sections are concurrently turned on, forming a closed loop path between the one input terminal and the other input terminal, and thus the charge voltage at the voltage storage element is prevented from exceeding a withstand voltage of the voltage storage element, and the overcharging of the voltage storage element is avoided. Furthermore, since the voltage storage element is not shorted, no short-circuit current occurs, power stored in the voltage storage element is prevented from being consumed in vain, and the voltage storage element and a driven circuit are free from damage. Since a closed loop path, different from a charging path, is formed to allow a generated current to flow therethrough in order to prevent overcharge of the voltage storage element, circuit elements having low withstand voltages may be employed, facilitating the integration of the circuit. Since the closed loop path, formed between two input terminals corresponding to the two output terminals of a generator, applies short-circuit braking to the rotation of a rotor in the generator, the amplitude of a terminal voltage is automatically lowered, and the generation of electromagnetic noise in coils and the rotor in the generator is controlled.

Claims

1. An overcharge prevention method for a voltage storage element connected to a bridge rectifier circuit comprising a first switching section connected between a first input terminal supplied with an AC voltage and a first power source line, a second switching section connected between a second input terminal supplied with the AC voltage and the first power source line, a third switching section connected between the first input terminal and a second power source line, and a fourth switching section connected between the second input terminal and the second power source line, the method comprising:

concurrently switching on one of;

both the first and second switching sections, and

both the third and fourth switching sections,

to form a closed loop path between the first input terminal and the second input terminal.

2. An overcharge prevention method according to claim 1,

wherein the first and second switching sections comprise P-channel MOSFETs, and

wherein the third and fourth switching sections comprise N-channel MOSFETs.

3. An overcharge prevention method used in a charging circuit which rectifies an AC voltage supplied to input terminals to charge a voltage storage element with power, the charging circuit comprising a first comparator section for comparing a terminal voltage at a first input terminal supplied with the AC voltage with an output voltage at a first power source line, a first switching section, which is connected between the first power source line and the first input terminal, and is turned on and off in response to the first comparator section, a second comparator section for comparing a terminal voltage at a second input terninal with the output voltage at the first power source line, a second switching section, which is connected between the first power source line and the second input terminal, and is turned on and off in response to the second comparator section, a third comparator section for comparing the terminal voltage supplied to the first input terminal with an output voltage at a second power source line, a third switching section, which is connected between the second power source line and the first input terminal, and is turned on and off in response to the third comparator section, a fourth comparator section for comparing the terminal voltage supplied to the second input terminal with the output voltage at the second power source line, a fourth switching section, which is connected between the second power source line and the second input terminal, and is turned on and off in response to the fourth comparator section, and the voltage storage element connected between the first power source line and the second power source line, wherein said overcharge prevention method comprises the steps of:

(a) detecting the voltage charged at the voltage storage element,

(b) determining whether the detected charge voltage exceeds a predetermined voltage,

(c) turning off one of;

both the first and second switching sections, and

both the third and fourth switching sections,

when the charge voltage exceeds the predetermined voltage, and

(d) forming a closed loop path between the first input terminal and the second input terminal, by concurrently turning on one of;

both the first and second switching sections, and

both the third and fourth switching sections.

4. An overcharge prevention method according to claim 3, wherein in step (b), the predetermined voltage is a reference voltage.

5. An overcharge prevention method according to claim 3, wherein, in step (d), both the first and second switching sections are turned on.

6. An overcharge prevention method according to claim 5, wherein, in step (d), both the first and second switching sections are turned on, subsequent to turning off both the third and fourth switching sections.

7. An overcharge prevention method according to one of claims 5 and 6, further comprising the step of returning both the third and fourth switching sections to a normal charging operation, subsequent to retiring both the first and second switching sections to a normal charging operation, when the first, second, third and fourth switching sections are returned to the normal charging operation.

8. An overcharge prevention method according to claim 3, wherein, in step (d), both the first and second switching sections are turned on with both the third and fourth switching sections remaining in an off state.

9. An overcharge prevention method according to claim 3, wherein, in step (d), both the third and fourth switching sections are turned on.

10. An overcharge prevention method according to claim 9, wherein, in step (d), both the third and fourth switching sections are turned on, subsequent to turning off both the first and second switching sections.

11. An overcharge prevention method according to one of claim 9 or 10, further comprising the step of returning both the first and second switching sections to a normal charging operation, subsequent to returning both the third and fourth switching sections to a normal charging operation, when the first, second, third and fourth switching sections are returned to the normal charging operation.

12. An overcharge prevention method according to claim 3, wherein, in step (d), both the third and fourth switching sections are turned on with both the first and second switching sections remaining in an off state.

13. An overcharge prevention method according to claim 3, wherein, in step (a), the detection of the charge voltage is intermittently performed at a predetermined sampling period.

14. A charging circuit comprising:

a bridge rectifier circuit comprising;

first switching means connected between a first input terminal supplied with an AC voltage and a first power source line,

second switching means connected between a second input terminal supplied with the AC voltage and the first power source line,

third switching means connected between the first input terminal and a second power source line, and

fourth switching means connected between the second input terminal and the second power source line,

a voltage storage element connected to said bridge rectifier circuit; and

closed loop forming means that forms a closed loop path between the first input terminal and the second input terminal, by concurrently turning on one of;

both the first and second switching means, and

both the third and fourth switching means.

15. A charging circuit according to claim 14, wherein the closed loop forming means concurrently turns on one of

both the first and second switching means subsequent to turning off both the third and fourth switching means, and

both the third and fourth switching means subsequent to turning off both the first and second switching means.

16. A charging circuit for charging a voltage storage element arranged between a first power source line and a second power source line by rectifying an AC voltage supplied between first and second input terminals, the charging circuit comprising:

first comparator means for comparing a terminal voltage supplied to the first input terminal with an output voltage at the first power source line;

first switching means, which is coupled between the first power source line and the first input terminal, and is turned on and off in response to said first comparator means;

second comparator means for comparing a terminal voltage supplied to the second input terminal with the output voltage at the first power source line;

second switching means, which is coupled between the first power source line and the second input terminal, and is turned on and off in response to said second comparator means;

third comparator means for comparing the terminal voltage supplied to the first input terminal with an output voltage at the second power source line;

third switching means, which is coupled between the second power source line and the first input terminal, and is turned on and off in response to said third comparator means;

fourth comparator means for comparing the terminal voltage supplied to the second input terminal with the output voltage at the second power source line;

fourth switching means, which is coupled between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator means;

a voltage storage element, which is coupled between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switching means;

predetermined voltage comparator means for detecting a voltage charged at said voltage storage element and for determining whether the detected charge voltage exceeds a predetermined voltage; and

closed loop forming means, which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switching means and by turning on both said first and second switching means, in response to the detection result by said predetermined voltage comparator means.

17. A charging circuit according to claim 16, wherein said predetermined voltage is a reference voltage.

18. A charging circuit according to claim 16, wherein said closed loop forming means comprises:

first control signal generating means for generating a first control signal for turning on both said first and second switching means when said predetermined voltage comparator means detects that the charge voltage exceeds the predetermined voltage;

second control signal generating means for generating a second control signal for turning off both said third and fourth switching means prior to turning on said first and second switching means;

first gating means, coupled between said first comparator means and said first switching means, for turning on said first switching means in response to the first control signal;

second gating means, coupled between said second comparator means and said second switching means, for turning on said second switching means in response to the first control signal;

third gating means, coupled between said third comparator means and said third switching means, for turning off said third switching means in response to the second control signal; and

fourth gating means, coupled between said fourth comparator means and said fourth switching means, for turning off said fourth switching means in response to the second control signal.

19. A charging circuit according to claim 16, wherein said closed loop forming means comprises:

control signal generating means for generating a control signal for turning on both said first and second switching means and for turning off both said third and fourth switching means, when said predetermined voltage comparator means detects that the charge voltage exceeds the predetermined voltage;

first gating means, coupled between said first comparator means and said first switching means, for turning on said first switching means in response to the control signal;

second gating means, coupled between said second comparator means and said second switching means, for turning on said second switching means in response to the control signal;

third gating means, coupled between said third comparator means and said third switching means, for turning off said third switching means in response to the control signal;

fourth gating means, coupled between said fourth comparator means and said fourth switching means, for turning off said fourth switching means in response to the control signal;

fifth gating means for supplying said first gating means with the control signal when said third switching means is in an off state; and

sixth gating means for supplying said second gating means with the control signal when said fourth switching means is in an off state.

20. A charging circuit according to claim 16, wherein each said switching means comprises a transistor.

21. A charging circuit according to claim 20, further comprising a parasitic diode connected in parallel with each said transistor.

22. A charging circuit according to claim 16, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises an oscillating weight that turns and a generating element for generating an electromotive force in response to the turning motion of the oscillating weight.

23. A charging circuit according to claim 16, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises an elastic member to which a deforming force is exerted, rotary means that is rotated by a restoring force that takes place when said elastic member restores to an original shape, and a generating element that generates an electromotive force in response to the rotary motion of said rotary means.

24. A charging circuit according to claim 16, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises a piezoelectric element that generates an electromotive force by means of the piezoelectric effect in response to a displacement applied thereto.

25. A charging circuit according to claim 16, wherein said predetermined voltage comparator means intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

26. An electronic device comprising:

a generator for generating an AC power,

a charging circuit comprising;

first comparator means for comparing a terminal voltage supplied to a first input terminal with an output voltage at a first power source line;

first switching means, which is coupled between the first power source line and the first input terminal, and is turned on and off in response to said first comparator means;

second comparator means for comparing a terminal voltage supplied to a second input terminal with the output voltage at the first power source line;

second switching means, which is coupled between the first power source line and the second input terminal, and is turned on and off in response to said second comparator means;

third comparator means for comparing the terminal voltage supplied to the first input terminal with an output voltage at a second power source line;

third switching means, which is coupled between the second power source line and the first input terminal, and is turned on and off in response to said third comparator means;

fourth comparator means for comparing the terminal voltage supplied to the second input terminal with the output voltage at the second power source line;

fourth switching means, which is coupled between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator means,

a voltage storage element, which is coupled between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switching means;

predetermined voltage comparator means for detecting a voltage charged at said voltage storage element and for determining whether the detected charge voltage exceeds a predetermined voltage; and

closed loop forming means which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switching means and by turning on both said first and second switching means, in response to a detection result by said predetermined voltage comparator means; and

a processing circuit operated from the power supplied by said voltage storage element.

27. An electronic device according to claim 26, wherein said predetermined voltage is a reference voltage.

28. An electronic device according to claim 26, wherein said predetermined voltage comparator means intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

29. A timepiece comprising:

a generator for generating an AC power,

a charging circuit comprising first comparator means for comparing a terminal voltage supplied to a first input terminal with an output voltage at a first power source line, first switching means, which is connected between the first power source line and the first input terminal, and is turned on and off in response to said first comparator means, second comparator means for comparing a terminal voltage supplied to a second input terminal with the output voltage at the first power source line, second switching means, which is connected between the first power source line and the second input terminal, and is turned on and off in response to said second comparator means, third comparator means for comparing the terminal voltage supplied to the first input terminal with an output voltage at a second power source line, third switching means, which is connected between the second power source line and the first input terminal, and is turned on and off in response to said third comparator means, fourth comparator means for comparing the terminal voltage supplied to the second input terminal with the output voltage at the second power source line, fourth switching means, which is connected between the second power source line and the second input terminal, and is turned on and off in response the second input terminal with the output voltage at the second power source line, fourth switching means, which is connected between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator means, a voltage storage element, which is connected between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switching means, predetermined voltage comparator means, which detects a voltage charged at said voltage storage element and determines whether the detected charge voltage exceeds a predetermined voltage, and closed loop forming means which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switching means and by turning on both said first and second switching means, in response to the detection result by said predetermined voltage comparator means, and

a time measurement circuit, operated from the power supplied from said voltage storage element, for measuring time.

30. A timepiece according to claim 29, wherein said predetermined voltage is a reference voltage.

31. A timepiece according to claim 29, wherein said predetermined voltage comparator means intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

32. A charging circuit comprising:

a bridge rectifier circuit comprising;

a first switch connected between a first input terminal supplied with an AC voltage and a first power source line,

a second switch connected between a second input terminal supplied with the AC voltage and the first power source line,

a third switch connected between the first input terminal and a second power source line, and

a fourth switch connected between the second input terminal and the second power source line;

a voltage storage element connected to said bridge rectifier circuit; and

a closed loop forming circuit that forms a closed loop path between the first input terminal and the second input terminal, by concurrently turning on one of;

both the first and second switches, and

both the third and fourth switches.

33. A charging circuit according to claim 32, wherein the closed loop forming circuit concurrently turns on one of

both the first and second switches subsequent to turning off both the third and fourth switches, and

both the third and fourth switches subsequent to turning off both the first and second switches.

34. A charging circuit for charging a voltage storage element arranged between a first power source line and a second power source line, with charge, by rectifying an AC voltage supplied between first and second input terminals, the charging circuit comprising:

a first comparator to compare a terminal voltage supplied to the first input terminal with an output voltage at the first power source line;

a first switch, which is coupled between the first power source line and the first input terminal, and is turned on and off in response to said first comparator;

a second comparator to compare a terminal voltage supplied to the second input terminal with the output voltage at the first power source line;

a second switch, which is coupled between the first power source line and the second input terminal, and is turned on and off in response to said second comparator;

a third comparator to compare the terminal voltage supplied to the first input terminal with an output voltage at the second power source line;

a third switch, which is coupled between the second power source line and the first input terminal, and is turned on and off in response to said third comparator;

a fourth comparator to compare the terminal voltage supplied to the second input terminal with the output voltage at the second power source line;

a fourth switch, which is coupled between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator;

a voltage storage element, which is coupled between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switches;

a predetermined voltage comparator to detect a voltage charged at said voltage storage element and to determine whether the detected charge voltage exceeds a predetermined voltage; and

a closed loop forming circuit, which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switches and by turning on both said first and second switches, in response to the detection result by said predetermined voltage comparator.

35. A charging circuit according to claim 34, wherein said predetermined voltage is a reference voltage.

36. A charging circuit according to claim 34, wherein said closed loop forming circuit comprises:

a first control signal generator to generate a first control signal to turn on both said first and second switches when said predetermined voltage comparator detects that the charge voltage exceeds the predetermined voltage;

a second control signal generator to generate a second control signal to turn off both said third and fourth switches prior to turning on both said first and second switches;

a first gate, coupled between said first comparator and said first switch, to turn on said first switch in response to the first control signal;

a second gate, coupled between said second comparator and said second switch, to turn on said second switch in response to the first control signal;

a third gate, coupled between said third comparator and said third switch, to turn off said third switch in response to the second control signal; and

a fourth gate, coupled between said fourth comparator and said fourth switch, to turn off said fourth switch in response to the second control signal.

37. A charging circuit according to claim 34, wherein said closed loop forming circuit comprises:

a control signal generator to generate a control signal to turn on both said first and second switches and to turn off both said third and fourth switches, when said predetermined voltage comparator detects that the charge voltage exceeds the predetermined voltage;

a first gate, coupled between said first comparator and said first switch, to turn on said first switch in response to the control signal;

a second gate, coupled between said second comparator and said second switch, to turn on said second switch in response to the control signal;

a third gate, coupled between said third comparator and said third switch, to turn off said third switch in response to the control signal;

a fourth gate, coupled between said fourth comparator and said fourth switch, to turn off said fourth switch in response to the control signal;

a fifth gate to supply said first gate with the control signal when said third switch is in an off state; and

a sixth gate to supply said second gate with the control signal when said fourth switch is in an off state.

38. A charging circuit according to claim 34, wherein each said switch comprises a transistor.

39. A charging circuit according to claim 38, further comprising a parasitic diode connected in parallel with each said transistor.

40. A charging circuit according to claim 34, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises an oscillating weight that turns and a generating element to generate an electromotive force in response to the turning motion of the oscillating weight.

41. A charging circuit according to claim 34, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises an elastic member to which a deforming force is exerted, a rotor that is rotated by a restoring force that takes place when said elastic member restores to an original shape, and a generating element that generates an electromotive force in response to the rotary motion of said rotor.

42. A charging circuit according to claim 34, wherein the AC power supplied to the first and second input terminals is generated by a generator which comprises a piezoelectric element that generates an electromotive force by means of the piezoelectric effect in response to a displacement applied thereto.

43. A charging circuit according to claim 34, wherein said predetermined voltage comparator intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

44. An electronic device comprising:

a generator to generate an AC power,

a charging circuit comprising;

a first comparator to compare a terminal voltage supplied to a first input terminal with an output voltage at a first power source line;

a first switch, which is coupled between the first power source line and the first input terminal, and is turned on and off in response to said first comparator;

a second comparator to compare a terminal voltage supplied to a second input terminal with the output voltage at the first power source line;

a second switch, which is coupled between the first power source line and the second input terminal, and is turned on and off in response to said second comparator;

a third comparator to compare the terminal voltage supplied to the first input terminal with an output voltage at a second power source line;

a third switch, which is coupled between the second power source line and the first input terminal, and is turned on and off in response to said third comparator;

a fourth comparator to compare the terminal voltage supplied to the second input terminal with the output voltage at the second power source line;

a fourth switch, which is coupled between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator,

a voltage storage element, which is coupled between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switches;

a predetermined voltage comparator to detect a voltage charged at said voltage storage element and to determine whether the detected charge voltage exceeds a predetermined voltage; and

a closed loop forming circuit which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switches and by turning on both said first and second switches, in response to a detection result by said predetermined voltage comparator; and

a processing circuit operated from the power supplied by said voltage storage element.

45. An electronic device according to claim 44, wherein said predetermined voltage is a reference voltage.

46. An electronic device according to claim 44, wherein said predetermined voltage comparator intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

47. A timepiece comprising:

a generator to generate an AC power,

a charging circuit comprising;

a first comparator to compare a terminal voltage supplied to a first input terminal with an output voltage at a first power source line;

a first switch, which is coupled between the first power source line and the first input terminal, and is turned on and off in response to said first comparator;

a second comparator to compare a terminal voltage supplied to a second input terminal with the output voltage at the first power source line;

a second switch, which is coupled between the first power source line and the second input terminal, and is turned on and off in response to said second comparator;

a third comparator to compare the terminal voltage supplied to the first input terminal with an output voltage at a second power source line;

a third switch, which is coupled between the second power source line and the first input terminal, and is turned on and off in response to said third comparator;

a fourth comparator to compare the terminal voltage supplied to the second input terminal with the output voltage at the second power source line;

a fourth switch, which is coupled between the second power source line and the second input terminal, and is turned on and off in response to said fourth comparator;

a voltage storage element, which is coupled between the first power source line and the second power source line, and is charged with a charging current rectified through said first, second, third and fourth switches;

a predetermined voltage comparator to detect a voltage charged at said voltage storage element and to determine whether the detected charge voltage exceeds a predetermined voltage; and

a closed loop forming circuit which forms a closed loop path between the first input terminal and the second input terminal by turning off both said third and fourth switches and by turning on both said first and second switches, in response to a detection result by said predetermined voltage comparator; and

a time measurement circuit, operated from the power supplied from said voltage storage element, for measuring time.

48. A timepiece according to claim 47, wherein said predetermined voltage is a reference voltage.

49. A timepiece according to claim 47, wherein said predetermined voltage comparator intermittently detects a voltage charged at said voltage storage element at a predetermined sampling period.

50. An electronic device comprising:

a charging circuit comprising;

a bridge rectifier circuit comprising;

a first switch connected between a first input terminal supplied with an AC voltage and a first power source line,

a second switch connected between a second input terminal supplied with the AC voltage and the first power source line,

a third switch connected between the first input terminal and a second power source line, and

a fourth switch connected between the second input terminal and the second power source line;

a voltage storage element connected to said bridge rectifier circuit;

a closed loop forming circuit that forms a closed loop path between the first input terminal and the second input terminal, by concurrently turning on one of;

both the first and second switches, and

both the third and fourth switches; and

a processing circuit operated from power supplied by the voltage storage element.

51. A new electronic device according to claim 50, wherein the closed loop forming circuit concurrently turns on one of

both the first and second switches subsequent to turning off both the third and fourth switches, and

both the third and fourth switches subsequent to turning off both the first and second switches.

52. A timepiece comprising:

a charging circuit comprising;

a bridge rectifier circuit comprising;

a first switch connected between a first input terminal supplied with an AC voltage and a first power source line,

a second switch connected between a second input terminal supplied with the AC voltage and the first power source line,

a third switch connected between the first input terminal and a second power source line, and

a fourth switch connected between the second input terminal and the second power source line;

a voltage storage element connected to said bridge rectifier circuit;

a closed hoop forming circuit that forms a closed hoop path between the first input terminal and the second input terminal, by concurrently turning on one of;

both the first and second switches, and

both the third and fourth switches; and

a time measurement circuit that measures time and is operated from power supplied from the voltage storage element.

53. A timepiece according to claim 52, wherein the closed loop forming circuit concurrently turns on one of

both the first and second switches subsequent to turning off both the third and fourth switches, and

both the third and fourth switches subsequent to turning off both the first and second switches.