Secondary battery protection circuit, battery pack and thermosensitive protection switch device

1. 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, 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, 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,

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.

2. 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;

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, wherein

the protection controller further comprises a switching device, and 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, wherein

the protection controller further comprises:

a first overcharging protector, and

a second overcharging protector, wherein

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,

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.

3. 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;

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, wherein

the protection controller further comprises:

a switching device,

a first overcharging protector,

a second overcharging protector,

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, and

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,

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 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;

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.

4. 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;

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, 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,

a second overcharging protector, 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,

wherein

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.

5. A protection circuit for a secondary battery according to claim 4 , 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.

6. 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, 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 over charging 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, 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,

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.

7. 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, 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.

8. A protection circuit for a secondary battery according to claim 7 , 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.

9. A protection circuit for a secondary battery according to claim 8 , 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.

10. A protection circuit for a secondary battery according to claim 9 , 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.