Secondary Battery Protection Circuit, Battery Pack and Thermosensitive Protection Switch Device

• US 20080116851A1
• Filed: 04/20/2006
• Published: 05/22/2008
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Mori, Iichiro
• Granted Patent: US 7,952,330 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 2200/106 PTC
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: H01M 50/583 in response to current, e.g. fuses
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A protection circuit is provided for protecting a secondary battery from overcharging and excessive discharge current by a simple circuit. The protection circuit is provided with a connection terminal (T3) for connecting the secondary battery (6); a connection terminal (T1) for connecting a charging device for charging the secondary battery (6) and/or a load device driven by a discharge current from the secondary battery (6); a bimetal switch (SW1) that is provided between the connection terminals (T1, T3) and turned off in the case of exceeding a specified temperature set beforehand; a heater (R2) for heating the bimetal switch (SW1); and an integrated circuit (IC1) for turning the bimetal switch (SW1) off by causing the heater (R2) to generate heat if a voltage applied to the connection terminal (T3) by the secondary battery (6) exceeds a preset reference voltage.

Claims

1-57. -57. (canceled)

58. A protection circuit for a secondary battery, comprising:

a first and a second connection terminals for connecting a charging device for charging the secondary battery and/or a load device driven by a discharge current from the secondary battery;

a third and a fourth connection terminals connected with the opposite electrodes of the secondary battery;

a heat-sensitive switch that is provided between the first and third connection terminals and turned off in the case of exceeding a specified temperature set beforehand;

a first heater for heating the heat-sensitive switch; and

a protection controller for turning the heat-sensitive switch off by causing the first heater to generate heat if a physical quantity relating to the characteristic of the secondary battery exceeds a preset value of the physical quantity.

59. A protection circuit for a secondary battery according to claim 58, wherein:

the physical quantity relating to the characteristic of the secondary battery is a voltage at the third connection terminal; and

the protection controller turns off the heat-sensitive switch by causing the heater to generate heat if the voltage at the third connection terminal exceeds a preset reference voltage.

60. A protection circuit for a secondary battery according to claim 59, wherein the first heater is a PTC thermistor whose resistance value increases and decreases with temperature.

61. A protection circuit for a secondary battery according to claim 59, wherein heat-sensitive switch is one selected from a bimetal switch, a switch using a shape-memory alloy and a switch using a shape-memory resin.

62. A protection circuit for a secondary battery according to claim 59, further comprising a fuse connected in series with the heat-sensitive switch, wherein operating conditions of the heat-sensitive switch are set so that the heat-sensitive switch is turned off earlier than the fuse.

63. A protection circuit for a secondary battery according to claim 58, wherein:

the first heater is connected in parallel with the heat-sensitive switch; and

the protection controller includes a detector for detecting the physical quantity relating to the characteristic of the secondary battery.

64. A protection circuit for a secondary battery according to claim 63, wherein:

the physical quantity relating to the characteristic of the secondary battery is a voltage at the third connection terminal;

the detector detects the voltage at the third connection terminal; and

the protection controller turns the heat-sensitive switch off by causing the first heater to generate heat if the voltage detected by the detector exceeds a preset reference voltage.

65. A protection circuit for a secondary battery according to claim 63, wherein:

the physical quantity relating to the characteristic of the secondary battery is the temperature of the secondary battery; and

the protection controller turns the heat-sensitive switch off by causing the first heater to generate heat if the temperature of the secondary battery detected by the detector exceeds a preset temperature.

66. A protection circuit for a secondary battery according to claim 63, wherein:

a first rectifying element is so disposed between the first heater and the first connection terminal as to allow the discharge current of the secondary battery connected with the third connection terminal to flow in forward direction; and

the protection controller includes a switching device for connecting and disconnecting a connection point of the first heater and the first rectifying element and the second connection terminal and turns the switching device on if the physical quantity detected by the detector exceeds the preset value of the physical quantity.

67. A protection circuit for a secondary battery according to claim 63, wherein:

the first heater includes a series circuit of a second and a third heaters; and

the protection controller includes a switching device for connecting and disconnecting a connection point of the second and third heaters and the fourth connection terminal and turns the switching device on if the physical quantity detected by the detector exceeds the preset value of the physical quantity.

68. A protection circuit for a secondary battery according to claim 63, further comprising a fourth heater having one end thereof connected to the first connection terminal and adapted to heat the heat-sensitive switch,

wherein the protection controller includes a switching device for connecting and disconnecting the other end of the fourth heater and the second connection terminal and turns the switching device on if the physical quantity detected by the detector exceeds the preset value of the physical quantity.

69. A protection circuit for a secondary battery according to claim 68, wherein the resistance values of the first and fourth heaters are so set as to equalize a heat value of the first heater by a discharge current from the secondary battery connected with the third connection terminal when the heat-sensitive switch is turned off and a heat value of the fourth heater by an output current from the charging device connected with the first connection terminal when the switching device is turned on.

70. A protection circuit for a secondary battery according to claim 68, further comprising a second rectifying element provided between the third connection terminal and the first heater in such a manner as to allow the discharge current of the secondary battery connected with the third connection terminal in forward direction.

71. A protection circuit for a secondary battery according to claim 67, wherein:

the second and third heaters are a PTC thermistor whose resistance value increases and decreases with temperature;

the PTC thermistor is substantially plate-shaped and formed with a groove for dividing at least one surface thereof into a plurality of areas;

some of the plurality of areas on the one surface of the PTC thermistor are used as a first electrode and at least some of the areas except those used as the first electrode are used as a second electrode;

the other surface of the PTC thermistor is used as a third electrode;

the first and third electrodes are used as connection terminals at the opposite ends of the second heater; and

the third and second electrodes are used as connection terminals at the opposite ends of the third heater.

72. A protection circuit for a secondary battery according to claim 68, wherein:

the first and fourth heaters are a PTC thermistor whose resistance value increases and decreases with temperature;

the PTC thermistor is substantially plate-shaped and formed with a groove for dividing at least one surface thereof into a plurality of areas;

some of the plurality of areas on the one surface of the PTC thermistor are used as a first electrode and at least some of the areas except those used as the first electrode are used as a second electrode;

the other surface of the PTC thermistor is used as a third electrode;

the first and third electrodes are used as connection terminals at the opposite ends of the first heater; and

the third and second electrodes are used as connection terminals at the opposite ends of the fourth heater.

73. A protection circuit for a secondary battery according to claim 71, wherein:

the groove divides the one surface of the PTC thermistor into two areas; and

one area divided by the groove is used as the first electrode and the other area is used as the second electrode.

74. A protection circuit for a secondary battery according to claim 71, wherein:

the groove is a substantially crisscross groove for dividing the one surface of the PTC into four areas;

two adjacent ones of the four areas are used as the first electrode; and

the areas other than those used as the first electrode are used as the second electrode.

75. A protection circuit for a secondary battery according to claim 69, wherein the PTC thermistor is shaped such that vertical and horizontal directions can be physically determined.

76. A protection circuit for a secondary battery according to claim 58, wherein:

the heat-sensitive switch is turned off in the case of exceeding a specified operating temperature by self-heat generation due a current flowing thereinto and in the case of exceeding the operating temperature by being externally heated; and

the protection controller includes;

a switching device for controlling the energization of the first heater,

a first overcharging protector for causing the switching device to energize the first heater if a voltage between the third and fourth connection terminals exceeds a specified overcharging protection voltage, and

a second overcharging protector for causing the switching device to energize the first heater if a voltage between the first and second connection terminals exceeds the overcharging protection voltage.

77. A protection circuit for a secondary battery according to claim 76, wherein:

the first overcharging protector includes a first comparator for detecting whether or not a voltage between the third and fourth connection terminals exceeds the overcharging protection voltage;

the second overcharging protector includes a second comparator for outputting a high-level signal if a voltage between the first and second connection terminals has exceeded the overcharging protection voltage; and

the switching device energizes the first heater if at least either one of the first and second comparators has outputted a high-level signal.

78. A protection circuit for a secondary battery according to claim 77, wherein the switching device includes:

an OR gate having an input terminal thereof connected to output terminals of the first and second comparators; and

an n-channel field-effect transistor having a gate thereof connected to an output terminal of the OR gate, having a drain thereof connected with the first heater, and having a source thereof connected to the second and fourth connection terminals.

79. A protection circuit for a secondary battery according to claim 58, wherein

the protection controller includes a switching device, and

the protection circuit further comprises a short-circuit protector for causing the switching device to energize the first heater if a voltage between the third and fourth connection terminals exceeds a sum of a voltage between the first and second connection terminals and a specified short-circuit protection voltage.

80. A protection circuit for a secondary battery according to claim 79, wherein:

the protection controller further includes a first overcharging protector and a second overcharging protector;

the first overcharging protector includes a first comparator for detecting whether or not a voltage between the third and fourth connection terminals exceeds an overcharging protection voltage;

the second overcharging protector includes a second comparator for outputting a high-level signal if a voltage between the first and second connection terminals has exceeded the overcharging protection voltage;

the short-circuit protector includes a third comparator for outputting a high-level signal if the voltage between the third and fourth connection terminals exceeds a sum of the voltage between the first and second connection terminals and the short-circuit protection voltage; and

the switching device energizes the first heater if at least one of the first to third comparators has outputted a high-level signal.

81. A protection circuit for a secondary battery according to claim 80, wherein the switching device includes:

an OR gate having an input terminal thereof connected to output terminals of the first to third comparators; and

an n-channel field-effect transistor having a gate thereof connected to an output terminal of the OR gate, having a drain thereof connected to the first heater, and having a source thereof connected to the second and fourth connection terminals.

82. A protection circuit for a secondary battery according to claim 79, further comprising a temperature controller for causing the switching device to stop energizing the first heater if the temperature of the first heater has reached to a specified upper limit temperature higher than the operating temperature of the heat-sensitive switch.

83. A protection circuit for a secondary battery according to claim 82, wherein:

the first overcharging protector includes a first comparator for outputting a high-level signal if a voltage between the third and fourth connection terminals exceeds an overcharging protection voltage;

the second overcharging protector includes a second comparator for outputting a high-level signal it a voltage between the first and second connection terminals has exceeded the overcharging protection voltage;

the short-circuit protector includes a third comparator for outputting a high-level signal if the voltage between the third and fourth connection terminals exceeds a sum of the voltage between the first and second connection terminals and the short-circuit protection voltage;

the temperature controller includes;

a temperature sensor for detecting the temperature of the first heater, and

a fourth comparator for outputting a low-level signal if temperature detected by the temperature sensor has reached the upper limit temperature; and

the switching device includes;

an OR gate having an input terminal thereof connected to output terminals of the first to third comparators,

an AND gate having an input terminal thereof connected to an output terminal of the OR gate and an output terminal of the fourth comparator, and

an n-channel field-effect transistor having a gate thereof connected to an output terminal of the AND gate, having a drain thereof connected to the first heater, and having a source thereof connected to the second and fourth connection terminals.

84. A protection circuit for a secondary battery according to claim 58, wherein:

the heat-sensitive switch is turned off in the case of exceeding a specified operating temperature by self-heat generation due a current flowing thereinto and in the case of exceeding the operating temperature by being externally heated; and

the protection controller includes;

a switching device for switching the energization of the first heater,

a first overcharging protector for causing the switching device to energize the first heater if the voltage between the third and fourth connection terminals exceeds a specified overcharging protection voltage, and

a temperature controller for causing the switching device to stop energizing the first heater if the temperature of the first heater has reached a specified upper limit temperature higher than the operating temperature of the heat-sensitive switch.

85. A protection circuit for a secondary battery according to claim 84, further comprising a short-circuit protector, wherein:

the protection controller further includes a second overcharging protector;

the first overcharging protector includes a first comparator for outputting a high-level signal if the voltage between the third and fourth connection terminals exceeds the overcharging protection voltage;

the second overcharging protector includes a second comparator for outputting a high-level signal if the voltage between the first and second connection terminals exceeds the overcharging protection voltage;

the short-circuit protector includes a third comparator for outputting a high-level signal if the voltage between the third and fourth connection terminals exceeds a sum of the voltage between the first and second connection terminals and the short-circuit protection voltage;

the temperature controller includes;

a temperature sensor for detecting the temperature of the first heater, and

a fourth comparator for outputting a low-level signal if the temperature detected by the temperature sensor has reached the upper limit temperature; and

the switching device includes;

an OR gate having an input terminal thereof connected with output terminals of the first to third comparators,

an AND gate having an input terminal thereof connected to an output terminal of the OR gate and an output terminal of the fourth comparator, and

an n-channel field-effect transistor having a gate thereof connected to an output terminal of the AND gate, a drain thereof connected to the first heater, and a source thereof connected to the second and fourth connection terminals.

86. A protection circuit for a secondary battery according to claim 85, wherein the switching device causes the first heater to be energized if high-level signals are outputted from both first and fourth comparators while causing the energization of the first heater to be stopped if a low-level signal is outputted from at least either one of the two comparators.

87. A protection circuit for a secondary battery according to claim 84, further comprising:

a temperature fuse connected between the heat-sensitive switch and the third connection terminal; and

an upper limit temperature changer for changing the upper limit temperature to the one higher than the melting temperature of the temperature fuse if the voltage between the third and fourth connection terminals has exceeded a second overcharging protection voltage higher than the overcharging protection voltage.

88. A protection circuit for a secondary battery according to claim 58, wherein:

the heat-sensitive switch is connected between the first and third connection terminals and is turned off in the case of exceeding a specified operating temperature by self-heat generation due a current flowing thereinto and in the case of exceeding the operating temperature by being externally heated; and

the protection controller includes;

a switching device for controlling the energization of the first heater,

a first overcharging protector for causing the switching device to energize the first heater if the voltage between the third and fourth connection terminals exceeds a specified overcharging protection voltage, and

a short-circuit protector for causing the switching device to energize the first heater if the voltage between the third and fourth connection terminals exceeds a sum of the voltage between the first and second connection terminals and a specified short-circuit protection voltage.

89. A protection circuit for a secondary battery according to claim 88, wherein:

the first overcharging protector includes a first comparator for detecting whether or not the voltage between the third and fourth connection terminals exceeds the overcharging protection voltage;

the short-circuit protector includes a third comparator for outputting a high-level signal if the voltage between the third and fourth connection terminals exceeds a sum of the voltage between the first and second connection terminals and a specified short-circuit protection voltage; and

the switching device energizes the first heater if at least either one of the first and third comparators has outputted a high-level signal.

90. A protection circuit for a secondary battery according to claim 89, wherein the switching device includes:

an OR gate having an input terminal thereof connected to output terminals of the first and third comparators, and

an n-channel field-effect transistor having a gate thereof connected to an output terminal of the OR gate, a drain thereof connected to the first heater, and a source thereof connected to the second and fourth connection terminals.

91. A protection circuit for a secondary battery according to claim 79, wherein a resistor is connected in parallel with the heat-sensitive switch.

92. A protection circuit for a secondary battery according to claim 76, further comprising a power supply controller for stopping the supply of power from the secondary battery to the protection circuit if the voltage between the third and fourth connection terminals falls to or below a specified excessive discharge voltage.

93. A protection circuit for a secondary battery according to claim 58, wherein:

the heat-sensitive switch is a bimetal switch; and

the protection controller includes;

an overcharging protector for energizing the first heater to turn the bimetal switch off if the voltage between the third and fourth connection terminals exceeds a specified overcharging protection voltage, and

a breaker for counting the number of times the bimetal switch is turned off by the overcharging protector and breaking the electrical connection with the secondary battery if a count value has exceeded a specified value determined based on an operation assurance number.

94. A protection circuit for a secondary battery according to claim 93, wherein the breaker includes:

a temperature fuse connected between the bimetal switch and the third connection terminal;

a second heater for heating the temperature fuse; and

a temperature fuse controller for energizing the second heater to melt the temperature fuse if the Count value has exceeded the specified value.

95. A protection circuit for a secondary battery according to claim 94, wherein:

the overcharging protector includes a comparator and a first transistor;

the temperature fuse controller includes a counter and a second transistor;

the comparator turns the first transistor on to energize the first heater and causes the counter to count up if the voltage between the third and fourth connection terminals has exceeded the overcharging protection voltage; and

the counter turns the second transistor on to energize the second heater if the count value has exceeded the specified value.

96. A protection circuit for a secondary battery according to claim 95, wherein:

the first heater includes the first transistor;

the second heater includes the second transistor;

the bimetal switch is heated by heat generated when the first transistor is on; and

the temperature fuse is heated by heat generated when the second transistor is on.

97. A protection circuit for a secondary battery according to claim 58, further comprising a heat-sensitive protection switch device including a frame body having a first and a second supporting members arranged at a specified distance from each other, a first wiring conductor for forming a contact by being arranged on the first supporting member at a first-surface side of the frame body and forming a mounting terminal by extending from the contact, a second wiring conductor for forming a contact by being arranged on the second supporting member at the first-surface side of the frame body and forming a mounting terminal by extending from the contact, and a heat-sensitive switch, wherein:

the heat-sensitive switch is arranged to straddle between the respective contacts of the first and second wiring conductors, and

a second-surface side of the frame body facing the first surface has a space portion in which the first heater is arranged via the respective supporting members.

98. A protection circuit for a secondary battery according to claim 97 wherein:

the heat-sensitive switch includes a movable contact member arranged to straddle between the respective contacts and a bimetal element for acting on the movable contact member to disconnect the respective contacts if being heated by the first heater; and

the frame body includes a coupling member for coupling the first and second supporting members and mounting the bimetal element on the first-surface side.

99. A protection circuit for a secondary battery according to claim 98, wherein the frame body is formed a recess in a second-surface side of the coupling member by forming the coupling member in an intermediate portion between the first and second surfaces of the first and second supporting members, the recess being the space portion.

100. A protection circuit for a secondary battery according to claim 97, wherein a cover body for covering the heat-sensitive switch is provided at the first-surface side of the frame body.

101. A protection circuit for a secondary battery according to claim 97, wherein the frame body is constructed by fixing the first and second supporting members by the wiring board.

102. A battery pack, comprising:

a secondary battery; and

a protection circuit therefor according to claim 58.

103. A battery pack according to claim 102, further comprising:

a bottomed container for accommodating the secondary battery; and

an external terminal connecting unit including wiring patterns constructing the protection circuit;

the protection circuit being formed in the external terminal connecting unit.

104. A battery pack according to claim 103, wherein:

the wiring patterns are printed on a surface of the external terminal connecting unit facing the secondary battery accommodated in the container.

105. A battery pack according to claim 103, wherein the heat-sensitive switch is arranged at a position of the external terminal connecting unit facing the secondary battery accommodated in the container.

106. A battery pack according to claim 105, further comprising an electrically conductive cover disposed to cover the protection controller and mounted to connect wiring patterns formed at the opposite sides of the protection controller while straddling the protection controller.

107. A battery pack according to claim 106, further comprising a fuse connected in series with the heat-sensitive switch is further provided, wherein:

operating conditions of the heat-sensitive switch are set such that the heat-sensitive switch is turned off earlier than the fuse; and

the fuse is arranged at a position of the cover facing the secondary battery accommodated in the container.

108. A battery pack according to claim 105, wherein:

the heat-sensitive switch includes a movable section driven by the temperature-dependent deformation of one selected from a bimetal, a shape-memory alloy and a shape-memory resin; and

a supporting member supporting the movable section is formed on a surface of the external terminal connecting unit facing the secondary battery accommodated in the container.

109. A battery pack according to claim 102, wherein:

the protection circuit comprises a heat-sensitive protection switch device including a frame body having a first and a second supporting members arranged at a specified distance from each other, a first wiring conductor for forming a contact by being arranged on the first supporting member at a first-surface side of the frame body and forming a mounting terminal by extending from the contact, a second wiring conductor for forming a contact by being arranged on the second supporting member at the first-surface side of the frame body and forming a mounting terminal by extending from the contact, and a heat-sensitive switch;

the heat-sensitive switch is arranged to straddle between the respective contacts of the first and second wiring conductors; and

a second-surface side of the frame body facing the first surface has a space portion in which the first heater is arranged via the respective supporting members.

110. A battery pack according to claim 109, wherein:

the heat-sensitive protection switch device is arranged between a positive electrode terminal of the secondary battery and the first connection terminal; and

the protection controller includes;

an overcharging detecting circuit for detecting that the secondary battery has been overcharged, and

a switching element on-off controlled by a detection signal of the overcharging detecting circuit.

111. A battery pack according to claim 110, wherein the overcharging detecting circuit, the switching element and the first heater are constructed by a semiconductor integrated circuit.

112. A battery pack according to claim 111, wherein the semiconductor integrated circuit is arranged in the space portion to heat the heat-sensitive switch.

113. A heat-sensitive protection switch device for turning a circuit off by being heated by a heating element, comprising:

a frame body having a first and a second supporting members arranged at a specified distance from each other;

a first wiring conductor for forming a contact by being arranged on the first supporting member at a first-surface side of the frame body and forming a mounting terminal by extending from the contact;

a second wiring conductor for forming a contact by being arranged on the second supporting member at the first-surface side of the frame body and forming a mounting terminal by extending from the contact; and

a heat-sensitive switch arranged to straddle between the respective contacts of the first and second wiring conductors and adapted to disconnect the respective contacts if being heated by the heating element,

a second-surface side of the frame body facing the first surface being formed with such an operating in which the heating element for heating the heat-sensitive switch via the respective supporting members can be arranged.

114. A battery pack having a first and a second connection terminals, comprising:

a secondary battery for supplying power to a load device; and

a protection circuit for protecting the secondary battery,

the protection circuit being constructed using the heat-sensitive protection switch device according to claim 113.