Communication apparatus having power backup function for image memory

• US 6,018,802 A
• Filed: 02/24/1997
• Issued: 01/25/2000
• Est. Priority Date: 08/31/1993
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Abe, Koichi, Kurosawa, Yuji
• Primary Examiner(s): Auve, Glenn A.
• Assistant Examiner(s): WILEY, DAVID ARMAND
• Application Number:
  US08/804,757
• Time in Patent Office: 1,065 Days
• Field of Search: 395/750.01-750.08, 395/183.12, 365/229, 710/300
• US Class Current: 713/300
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: H04N 1/00885 Power supply means, e.g. arrangements for the control of power supply to the apparatus or components thereof
• CPC Class Codes: H04N 1/00893 using a back-up supply, e.g. in case of main-supply failure
• CPC Class Codes: H04N 1/00899 Detection of supply level or supply failure
• CPC Class Codes: H04N 1/32363 at the transmitter or at the receiver

Abstract

A communication apparatus comprises a main power supply for supplying a power to respective units of the apparatus, a central control unit powered from said main power supply for controlling the entire apparatus, a rewritable data memory unit, a main power supply control unit for controlling an operation of said main power supply, a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit, and a unit for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply.

Claims

1. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit; and

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply,

wherein said main power supply control unit includes timer means and starts said main power supply when the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said secondary battery to start a stand-by charge mode.

2. A communication apparatus according to claim 1 further comprising a solar cell for charging said secondary battery and supplying the power to said memory unit during the stop of said main power supply.

3. A communication apparatus according to claim 2 wherein a power supply to supply the power to said memory unit is any one of said main power supply, said secondary battery and said solar cell, and said main power supply, said secondary battery and said solar cell are switched such that the power is supplied to said memory unit from said secondary battery or said solar cell during the stop of said main power supply, and the power is supplied to said memory unit from said main power supply during the operation of said main power supply.

4. A communication apparatus according to claim 2 wherein the power is supplied to said main power supply control unit in the priority order of from said main power supply, said solar cell and said secondary battery.

5. A communication apparatus according to claim 2 wherein said secondary battery is charged by the rest of the power supplied from said solar cell.

6. A communication apparatus according to claim 1 or 2 further comprising switching means, wherein said main power supply control unit starts said main power supply by an on signal from said switching means.

7. A communication apparatus according to claim 6 wherein said switching means comprises a document sheet detection switch, a switch for starting the operation of a transmission start key or an off-hook detection switch of hand set.

8. A communication apparatus according to claim 7 wherein said switching means comprises a mechanical switch or a reed switch.

9. A communication apparatus according to claim 1 or 2 further comprising call signal detection means for detecting a call signal from a telephone line, wherein said main power supply control unit starts said main power supply by the detection of the call signal by said call signal detection means.

10. A communication apparatus according to claim 1 or 2 further comprising switching means and call signal detection means for detecting a call signal from a telephone line, wherein said main power supply control unit starts said main power supply by an on signal from said switching means or a call detection signal from said call signal detection means.

11. A communication apparatus according to claim 10 wherein said main power supply control unit and said central control unit receive the on signal of said switching means and the call detection signal of said call signal detection means, and said main power supply control unit forcibly stops said main power supply when said central control unit issues a stop command.

12. A communication apparatus according to claim 1 or 2 wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery, and starts said main power supply when the detected voltage drops below a predetermined threshold to cause said main power supply to supply the power to said main power supply control unit and said secondary battery and start a stand-by charge mode.

13. A communication apparatus according to claim 12 wherein the operation of said main power supply is stopped when a voltage of said secondary battery rises above a threshold in the stand-by charge mode.

14. A communication apparatus according to claim 1 or 2 further comprising power failure detection means for detecting the stop of the power from said main power supply, wherein said main power supply control unit switches control of refreshing of said memory unit from said central control unit to said main power supply control unit when the power failure is detected by said power failure detection means.

15. A communication apparatus according to claim 1 or 2 further comprising energization detection means for detecting the energization to said main power supply, wherein said main power supply control unit starts said main power supply and switches control of refreshing of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said energization detection means detects the energization.

16. A communication apparatus according to claim 1 or 2 further comprising detection means for detecting the energization to said main power supply and detecting the stop of the energization of said main power supply, wherein said main power supply control unit switches control of refreshing of said memory unit from said central control unit to said main power supply control unit when said detection means detects the stop of the energization, and starts said main power supply and switches the control of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said detection means detects the energization.

17. A communication apparatus according to claim 1 or 2 wherein said main power supply control unit includes timer means and stops the operation of said main power supply when a unit other than said main power supply does not operate for a predetermined time period.

18. A communication apparatus according to claim 1 or 2 wherein said main power supply charges said secondary battery during the operation.

19. A communication apparatus according to claim 1 or 2 wherein said main power supply comprises a switching power supply and the switching is externally controllable.

20. A communication apparatus according to claim 1 or 2 wherein said main power supply control unit controls refreshing of said memory unit during the stop of said main power supply.

21. A communication apparatus according to claim 1 or 2 wherein said main power supply control unit controls refreshing of said memory unit during the stop of said main power supply, and said central controls said memory unit during the operation of said main power supply.

22. A communication apparatus according to claim 1 or 2 wherein a power supply to supply the power to said memory unit is either one of said main power supply and said secondary battery, and said main power supply and said secondary battery are switched such that the power is supplied to said memory unit from said secondary battery during the stop of said main power supply, and the power is supplied to said memory unit from said main power supply during the operation of said main power supply.

24. A communication apparatus according to claim 1 or 23 wherein the operation of said main power supply is stopped when said main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

23. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit;

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply; and

a solar cell for charging said secondary battery and supplying the power to said memory unit during the stop of said main power supply,

wherein said main power supply control unit includes timer means and starts said main power supply when the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said secondary battery to start a stand-by charge mode.

25. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit; and

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply,

wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery and timer means and starts said main power supply when the voltage of said secondary voltage drops below a predetermined threshold or the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said secondary battery to start a stand-by charge mode.

26. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit; and

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply,

wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery and timer means and starts said main power supply when the voltage of said secondary voltage drops below a predetermined threshold or the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said secondary battery to start a stand-by change mode and,

wherein the operation of said main power supply is stopped when a voltage of said secondary battery rises above a threshold in the stand-by charge mode or when said main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

27. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit;

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply; and

energization detection means for detecting the energization to said main power supply, wherein said main power supply control unit starts said main power supply and switches the control of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said energization detection means detects the energization,

wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery, and the operation of said main power supply is stopped when a voltage of said secondary battery rises above a threshold in a main power supply back-up mode in which said main power supply operates and backs up the data stored in said memory unit.

28. A communication apparatus comprising;

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit;

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply; and

energization detection means for detecting the energization to said main power supply, wherein said main power supply control unit starts said main power supply and switches the control of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said energization detection means detects the energization,

wherein said main power supply control unit includes timer means, and stops the operation of said main power supply when a main power supply back-up mode in which said main power supply operates and backs up the data stored in said memory means lasts for a predetermined time period.

29. A communication apparatus comprising:

a main power supply for supplying a power to respective units of the apparatus;

a central control unit powered from said main power supply for controlling the entire apparatus;

a rewritable data memory unit;

a main power supply control unit for controlling an operation of said main power supply;

a secondary battery charged by said main power supply for supplying a power to said main power supply control unit and said memory unit;

means for supplying the power from said secondary battery to said memory unit during the stop of said main power supply and supplying the power from said main power supply to said memory unit during the operation of said main power supply; and

energization detection means for detecting the energization to said main power supply, wherein said main power supply control unit starts said main power supply and switches the control of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said energization detection means detects the energization,

wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery and timer means, and stops the operation of said main power supply when the voltage of said secondary battery rises above a predetermined threshold in a main power supply back-up mode in which said main power supply operates and backs the data stored in said memory means or when the main power supply back-up mode lasts for a predetermined time period.

30. A communication apparatus comprising:

a main power supply for supplying power to respective units of the apparatus;

a central control unit, powered from said main power supply, that generates an ON/OFF instruction signal;

a rewritable data memory unit;

a main power supply control unit for turning ON and turning OFF said main power supply in response to the ON/OFF instruction signal generated by said central control unit;

a battery charged by said main power supply for supplying power to said main power supply control unit and said memory unit; and

means for selectively supplying power to said memory unit (a) from said battery in response to an OFF condition of the ON/OFF instruction signal, and (b) from said main power supply in response to an ON condition of the ON/OFF instruction signal.

31. A communication apparatus according to claim 30 further comprising a solar cell for charging said battery and supplying the power to said memory unit during the stop of said main power supply.

32. A communication apparatus according to claim 31, wherein a power supply to supply the power to said memory unit is any one of said main power supply, said battery and said solar cell, and said main power supply, said battery and said solar cell are switched such that the power is supplied to said memory unit from said battery or said solar cell during stop of said power supply, and the power is supplied to said memory unit from said main power supply during the operation of said main power supply.

33. A communication apparatus according to claim 31, wherein the power is supplied to said main power supply control unit in the priority order of from said main power supply, said solar cell and said battery.

34. A communication apparatus according to claim 31, wherein said battery is charged by the rest of the power supplied from said solar cell.

35. A communication apparatus according to claim 30 or 31 further comprising switching means, wherein said main power supply control unit starts said main power supply by an on signal from said switching means.

36. A communication apparatus according to claim 35, wherein said switching means comprises a document sheet detection switch, a switch for starting the operation of a transmission start key or an off-hook detection switch of a hand set.

37. A communication apparatus according to claim 36, wherein said switching means comprises a mechanical switch or a reed switch.

38. A communication apparatus according to claim 30 or 31 further comprising call signal detection means for detecting a call signal from a telephone line, wherein said main power supply control unit starts said main power supply by the detect ion of the call signal by said call signal detection means.

39. A communication apparatus according to claim 30 or 31 further comprising switching means and call signal detection means for detecting a call signal from a telephone line, wherein said main power supply control unit starts said main power supply by an on signal from said switching means or a call detection signal from said call signal detection mean.

40. A communication apparatus according to claim 30 or 31, wherein said main power supply control unit includes voltage detection means for detecting a voltage of said battery, and starts said main power supply when the detected voltage drops below a predetermined threshold to cause said main power supply to supply the power to said main power supply control unit and said battery and start a stand-by charge mode.

41. A communication apparatus according to claim 40, wherein the operation of said main power supply is stopped when a voltage of said battery rises above a threshold in the stand-by charge mode.

42. A communication apparatus according to claim 30 or 31, wherein said main power supply control unit includes timer means and starts said main power supply when the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said battery to start a stand-by charge mode.

43. A communication apparatus according to claim 30 or 31, wherein said main power supply control unit includes voltage detection means for detecting a voltage of said battery and timer means and starts said main power supply when the voltage of said battery drops below a predetermined threshold or the power is not supplied from said main power supply for a predetermined time period and causes said main power supply to supply the power to said main power supply control unit and said battery to start a stand-by charge mode.

44. A communication apparatus according to claim 43, wherein the operation of said main power supply is stopped when a voltage of said battery rises above a threshold in the stand-by charge mode or when said main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

45. A communication apparatus according to claim 30 or 31 further comprising energization detection means for detecting the energization to said main power supply, wherein said main power supply control unit starts said main power supply and switches control of refreshing of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said energization detection means detects the energization.

46. A communication apparatus according to claim 45, wherein said main power supply control unit includes voltage detection means for detecting a voltage of said secondary battery, and the operation of said main power supply is stopped when a voltage of said battery rises above a threshold in a main power supply back-up mode in which said main power supply operates and backs up the data stored in said memory unit.

47. A communication apparatus according to claim 45, wherein said main power supply control unit includes timer means, and stops the operation of said main power supply when a main power supply back-up mode in which said main power supply operates and backs up the data stored in said memory means lasts for a predetermined time period.

48. A communication apparatus according to claim 45, wherein said main power supply control unit includes voltage detection means for detecting a voltage of said battery and timer means, and stops the operation of said main power supply when the voltage of said battery rises above a predetermined threshold in a main power supply back-up mode in which said main power supply operates and backs the data stored in said memory means or when the main power supply back-up mode lasts for a predetermined time period.

49. A communication apparatus according to claim 30 or 31, wherein said main power supply control unit includes timer means and stops the operation of said main power supply when a unit other than said main power supply does not operate for a predetermined time period.

50. A communication apparatus according to claim 30 or 31, wherein said main power supply charges said battery during the operation.

51. A communication apparatus according to claim 30 or 31, wherein said main power supply comprises a switching power supply and the switching is externally controllable.

52. A communication apparatus according to claim 30 or 31, wherein said main power supply control unit controls refreshing of said memory unit during the stop of said main power supply.

53. A communication apparatus according to claim 30 or 31, wherein a power supply to supply the power to said memory unit is either one of said main power supply and said battery, and said main power supply and said battery are switched such that the power is supplied to said memory unit from said battery during stop of said main power supply, and the power is supplied to said memory unit from said main power supply during the operation of said main power supply.

54. A communication apparatus according to claim 30 wherein the operation of said main power supply is stopped when said main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

55. An apparatus according to claim 30, further comprising a central control unit powered from said main power supply for controlling the entire apparatus, wherein said main power supply control unit turns ON/OFF in response to an ON/OFF instruction signal from said central control unit.

56. A communication apparatus according to claim 55 further comprising power failure detection means for detecting the stop of the power from said main power supply, wherein said main power supply control unit switches control of refreshing of said memory unit from said central control unit to said main power supply control unit when the power failure is detected by said power failure detection means.

57. A communication apparatus according to claim 55 further comprising detection means for detecting the energization to said main power supply and detecting the stop of the energization of said main power supply, wherein said main power supply control unit switches control of refreshing of said memory unit from said central control unit to said main power supply control unit when said detection means detects the stop of the energization, and starts said main power supply and switches the control of said memory unit from said main power supply control unit to said central control unit and causes said main power supply to supply the power to said memory unit when said detection means detects the energization.

58. A communication apparatus according to claim 55, wherein said main power supply control unit controls refreshing of said memory unit during the stop of said main power supply, and said central control unit controls said memory unit during the operation of said main power supply.

59. A communication apparatus according to claim 55, wherein said main power supply control unit and said central control unit receive the on signal of said switching means and the call detection signal of said call signal detection means, and said main power supply control unit forcibly stops said main power supply when said central control unit issues a stop command.

60. An apparatus according to claim 30, wherein said memory unit is set in a self-refresh mode during an OFF period of said main power supply.

61. A communication method operative in a communication apparatus including respective units, a main power supply, a rewritable data memory unit, a main power supply control unit and a battery, said method-comprising:

a main power supply step of supplying power to respective units of the apparatus from the main power supply;

a generating step of generating an ON/OFF instruction signal;

a main power supply control step of turning ON and turning OFF said main power supply in response to the ON/OFF instruction signal generated in said generating step;

a charging step of charging a battery by the main power supply unit, the battery supplying power to the main power supply control unit and the memory unit; and

a supplying step of selectively supplying power to the memory unit (a) from the battery in response to an OFF condition of the ON/OFF instruction signal generated in said generating step, and (b) from the main power supply in response to an ON condition of the ON/OFF instruction signal generated in said generating step.

62. A method according to claim 61, further comprising a step of using a solar cell for charging the battery and supplying the power to the memory unit during the stop of the main power supply.

63. A method according to claim 62, wherein a power supply to supply the power to the memory unit is any one of the main power supply, the battery and the solar cell, and the main power supply, the battery and the solar cell are switched such that the power is supplied to the memory unit from the battery or the solar cell during stop of the power supply, and the power is supplied to the memory unit from the main power supply during the operation of the main power supply.

64. A method according to claim 62, wherein the power is supplied to the main power supply control unit in the priority order of from the main power supply, the solar cell and the battery.

65. A method according to claim 62, wherein the battery is charged by the rest of the power supplied from the solar cell.

66. A method according to claim 61 or 62, wherein the apparatus further includes switching means, and wherein the main power supply control unit starts the main power supply by an on signal from the switching means.

67. A method according to claim 66, wherein the switching means comprises a document sheet detection switch, a switch for starting the operation of a transmission start key or an off-hook detection switch of a hand set.

68. A method according to claim 67, wherein the switching means comprises a mechanical switch or a reed switch.

69. A method according to claim 61 or 62, further comprising a call signal detection step of detecting a call signal from a telephone line, wherein the main power supply control unit starts the main power supply by the detection of the call signal by said call signal detection step.

70. A according to claim 61 or 62, wherein the apparatus further includes switching means and call signal detection means for detecting a call signal from a telephone line, wherein the main power supply control unit starts the main power supply by an ON signal from the switching means or a call detection signal from the call signal detection means.

71. A method according to claim 61 or 62, wherein the main power supply control unit includes voltage detection means for detecting a voltage of the battery, and starts said main power supply step when the detected voltage drops below a predetermined threshold to cause the main power supply to supply the power to the main power supply control unit and the battery and start a stand-by charge mode.

72. A method according to claim 71, wherein the operation of the main power supply is stopped when a voltage of the battery rises above a threshold in the stand-by charge mode.

73. A method according to claim 61 or 62, wherein the main power supply control unit includes timer means and starts the main power supply when the power is not supplied from the main power supply for a predetermined time period and causes the main power supply to supply the power to the main power supply control unit and the battery to start a stand-by charge mode.

74. A method according to claim 61 or 62, wherein the main power supply control unit includes voltage detection means for detecting a voltage of the battery and timer means and starts the main power supply when the voltage of the battery drops below a predetermined threshold or the power is not supplied from the main power supply for a predetermined time period and causes the main power supply to supply the power to the main power supply control unit and the battery to start a stand-by charge mode.

75. A method according to claim 74, wherein the operation of the main power supply is stopped when a voltage of the battery rises above a threshold in the stand-by charge mode or when the main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

76. A method according to claim 61, wherein the apparatus further includes a central control unit powered from the main power supply for controlling the entire apparatus, wherein the main power supply control unit turns ON/OFF in response to an ON/OFF instruction signal from the central control unit.

77. A method according to claim 76, wherein the apparatus further includes power failure detection means for detecting the stop of the power from the main power supply, wherein said main power supply control step switches control of refreshing of the memory unit from the central control unit to the main power supply control unit when the power failure is detected by the power failure detection means.

78. A method according to claim 76, wherein the apparatus further includes energization detection means for detecting the energization to the main power supply, wherein said main power supply control step starts the main power supply and switches control of refreshing of the memory unit from the main power supply control unit to the central control unit and causes the main power supply to supply the power to the memory unit when the energization detection means detects the energization.

79. A method according to claim 76, wherein said main power supply control step controls refreshing of the memory unit during the stop of the main power supply, and the central control unit controls the memory unit during the operation of the main power supply.

80. A method according to claim 76, wherein the main power supply control unit and the central control unit receive the on signal of the switching means and the call detection signal of the call signal detection means, and the main power supply control unit forcibly stops said main power supply step when the central control unit issues a stop command.

81. A method according to claim 61 or 62, wherein the apparatus further includes energization detection means for detecting the energization to the main power supply, wherein said main power supply control step starts the main power supply and switches control of refreshing of the memory unit from the main power supply control unit to the central control unit and causes the main power supply to supply the power to the memory unit when the energization detection means detects the energization.

82. A communication apparatus according to claim 81, wherein the main power supply control unit includes voltage detection means for detecting a voltage of the battery, and the operation of the main power supply is stopped when a voltage of the battery rises above a threshold in a main power supply back-up mode in which the power supply operates and backs up the data stored in the memory unit.

83. A method according to claim 81, wherein the main power supply control unit includes timer means, and stops the operation of the main power supply when a main power supply back-up mode in which the main power supply operates and backs up the data stored in the memory unit lasts for a predetermined time period.

84. A method according to claim 81, wherein the main power supply control unit includes voltage detection means for detecting a voltage of the battery and timer means, and stops the operation of the main power supply when the voltage of the battery rises above a predetermined threshold in a main power supply back-up mode in which the main power supply operates and backs the data stored in the memory unit or when the main power supply back-up mode lasts for a predetermined time period.

85. A method according to claim 61 or 62, wherein the main power supply control unit includes timer means and stops the operation of the main power supply when a unit other than the main power supply does not operate for a predetermined time period.

86. A method according to claim 61 or 62, wherein said main power supply step charges the battery during the operation.

87. A method according to claim 61 or 62, wherein the main power supply comprises a switching power supply and the switching is externally controllable.

88. A method according to claim 61 or 62, wherein said main power supply control step controls refreshing of the memory unit during the stop of the main power supply.

89. A method according to claim 61 or 62, wherein a power supply to supply the power to the memory unit is either one of the main power supply and the battery, and the main power supply and the battery are switched such that the power is supplied to the memory unit from the battery during stop of the main power supply, and the power is supplied to the memory unit from the main power supply during the operation of the main power supply.

90. A method according to claim 61, wherein the operation of the main power supply is stopped when the main power supply does not supply the power for a predetermined time period in the stand-by charge mode.

91. A method according to claim 61, wherein the memory unit is set in a self-refresh mode during an OFF period of the main power supply.