HK1083571B - Secondary battery with protective circuit - Google Patents

Description

Secondary battery with protection circuit

Technical Field

The present invention relates to a secondary battery capable of repeated charging and discharging, and more particularly to a secondary battery having a built-in protection circuit.

Technical Field

Conventionally, secondary batteries with built-in protection circuits are used for portable telephones, portable personal computers, and the like, and as the charging capacity increases, a safer protection circuit is required.

Reference numeral 501 of fig. 16 denotes a conventional secondary battery, which includes an electric storage device 511, a control circuit 515, a protection circuit 512, a main switching element 514, and a main fusing element 533.

The high-voltage side output terminal of the power storage device 511 is connected to the 1 st output terminal 528 through the protection circuit 512, and the ground side output terminal is connected to the 2 nd output terminal 529 through the main fuse element 533 and the main switch element 514.

The on and off of the main switching element 514 are controlled by the control circuit 515, but in the following description, it is assumed that the main switching element 514 is maintained in an on state.

If the power storage device 511 is configured to be repeatedly chargeable and dischargeable, and the charger 513 is connected between the 1 st and 2 nd output terminals 528 and 529, a charging current flows through the protection circuit 512, the main fuse element 533, and the main switching element 514, and the power storage device 511 is charged.

When an external circuit such as a portable personal computer is connected in place of the charger 513, the charging device 511 discharges, and a discharge current in the opposite direction to the charging current flows through the protection circuit 512, the main fuse element 533, and the main switch element 514, and is supplied to the external circuit.

The protection circuit 512 includes a voltage detection circuit 521, an auxiliary switching element 522, and a fuse circuit 524. The fuse circuit 524 includes 1 st and 2 nd auxiliary fuse elements 535a and 535b and a heating element 536 composed of a resistance heating body.

The 1 st and 2 nd auxiliary fuse elements 535a and 535b are connected in series, and the high-voltage side output terminal of the power storage device 511 is connected to the 1 st output terminal 528 by this series circuit.

The 1 st and 2 nd auxiliary fuse elements 535a and 535b are connected to the auxiliary switching element 522 through the heating element 536.

The voltage detection circuit 521 controls the auxiliary switching element 522 to be turned on and off, and the voltage detection circuit 521 detects the voltage between the high-voltage side output terminal and the ground side output terminal of the power storage device 511, and if the voltage is smaller than a preset upper limit voltage value, the auxiliary switching element 522 is maintained in the off state, and no current flows into the heating element 536.

On the other hand, if power storage device 511 is overcharged due to erroneous connection of secondary battery 501 or the like, and a voltage larger than the upper limit voltage value appears at the high-voltage side output terminal of power storage device 511, voltage detection circuit 521 detects an overvoltage and turns on auxiliary switching element 522. As a result, a large current flows into the heating element 536, and heat is generated.

Heating element 536 is disposed adjacent to 1 st and 2 nd auxiliary fuse elements 535a and 535b, and when a large current flows into heating element 536 to generate heat, 1 st and 2 nd auxiliary fuse elements 535a and 535b are fused, and the high-voltage side output terminal of power storage device 511 is disconnected from 1 st output terminal 528.

As a result, charging of power storage device 511 is stopped, and accidents such as smoke can be prevented.

On the other hand, even if the state of charge of the power storage device 511 is normal, if a short circuit occurs between the 1 st and 2 nd output terminals 528 and 529, a large overcurrent is generated due to discharge of the power storage device 511, and flows through the 1 st and 2 nd auxiliary fuse elements 535a and 535b, the main switch element 514, and the main fuse element 533.

The main fuse element 533 is disposed in close contact with the main switch element 514, and when the main switch element 514 generates heat due to a fault or an overcurrent flowing into the main switch element, the main fuse element 533 is fused by the heat. As a result, the ground-side output terminal of the power storage device 511 is disconnected from the 2 nd output terminal 529, and the discharge of the power storage device 511 is completed, so that accidents such as smoke can be prevented.

However, since the primary fuse element 533 is located in the middle of the path through which the charge and discharge current flows in the secondary battery 501, there is a problem in that the power is unnecessarily consumed in the primary fuse element 533 and the service life of the secondary battery 501 is shortened.

Further, if the rated current of secondary battery 501 is large, primary fuse element 533 of a current capacity corresponding to the rated current must be used, and therefore, there are problems such as an increase in the outer size of primary fuse element 533 and an increase in cost.

In recent years, demands for miniaturization and long-term growth have been increasing for portable personal computers, which has led to a demand for improvement of the secondary battery 501.

The present invention has been made to solve the above-described problems of the conventional technology, and an object of the present invention is to provide a small-sized secondary battery with low power consumption.

Disclosure of Invention

In order to solve the above problem, a secondary battery according to the present invention includes a power storage device, a protection circuit, an auxiliary switching element, a heating element, a 1 st auxiliary fuse element, 1 st and 2 nd output terminals, and a temperature detection portion, and is configured such that: when a charging device is connected to the 1 st and 2 nd output terminals, a charging current supplied from the charging device flows through the protection circuit to charge the power storage device, and when an external circuit is connected to the 1 st and 2 nd output terminals, a discharging current of the power storage device flows through the protection circuit to supply the protection circuit to the external circuit, the protection circuit includes a series circuit in which a 1 st voltage-dividing resistance element, a 2 nd voltage-dividing resistance element, and a main fuse element are connected in series, the series circuit is connected between a high-voltage-side output terminal and a ground-side output terminal of the power storage device, and before the main fuse element is fused, a voltage between the high-voltage-side output terminal and the ground-side output terminal is divided by the 1 st voltage-dividing resistance element and the 2 nd voltage-dividing resistance element to generate a divided voltage, and the divided voltage is input to a control terminal of the auxiliary switching element, the auxiliary switching element is placed in an off state, and if the main fuse element fuses due to heat generation at the temperature detection portion closely arranged thereto, the control terminal of the auxiliary switching element is set to be connected to the high-voltage side output terminal through the 1 st or 2 nd voltage dividing resistance element or to the ground side output terminal through the 1 st or 2 nd voltage dividing resistance element, the auxiliary switching element is turned on, the heating element is energized and generates heat due to conduction of the auxiliary switching element, and the 1 st output terminal is set to be disconnected from the power storage device and the heating element when the 1 st auxiliary fuse element fuses due to heat generation of the heating element.

In the secondary battery of the present invention, the protection circuit includes a 2 nd auxiliary fusing element that fuses by heat generation of the heating element to disconnect the auxiliary switching element from the power storage device and to stop a current flowing into the auxiliary switching element.

In the secondary battery of the present invention, a main switching element is provided in a path through which the charging current and the discharging current flow, the main switching element controls the flow of the charging current and the discharging current, and the temperature detection portion is the main switching element.

In the secondary battery of the present invention, a voltage detection circuit that detects a voltage between the high-voltage-side output terminal and the ground-side output terminal of the power storage device is provided, an output terminal of the voltage detection circuit is connected to a control terminal of the auxiliary switching element, and the auxiliary switching element is placed in conduction if the voltage detection circuit detects a voltage equal to or higher than an upper limit voltage.

In the secondary battery of the present invention, a diode element is inserted between the output terminal of the voltage detection circuit and the control terminal of the auxiliary switching element, and the voltage detection circuit is disconnected from the auxiliary switching element by reverse-biasing the diode element after the primary fuse element is fused.

In the secondary battery of the present invention, the auxiliary switching element is a transistor.

The present invention has the above-described configuration, and the resistance value of the thermistor changes according to the temperature of the temperature detection portion.

The structure is as follows: the thermal coupling between the temperature detection portion and the thermosensitive element is improved, and if the thermal coupling portion is broken, an excessive current larger than the normal charge-discharge current of the electric storage device flows in to generate heat, so that the thermosensitive element is heated to raise the temperature.

The thermistor of the present invention includes a PTC thermistor whose resistance value increases with an increase in temperature, an NTC thermistor whose resistance value decreases with an increase in temperature, and a CTR thermistor, and also includes a fuse whose resistance value becomes infinite as a result of fusing due to an increase in temperature.

In short, any circuit in which a thermosensitive element whose resistance value changes with a change in temperature of a temperature detection portion is disposed on a path different from a path through which a charge/discharge current flows, and an auxiliary switching element is turned on by a change in resistance value of the thermosensitive element to fuse a 1 st auxiliary fuse element is included in the present invention.

Drawings

Fig. 1 shows a secondary battery according to a first embodiment of the present invention.

Fig. 2 is a secondary battery according to a second example of the present invention.

Fig. 3 is a secondary battery according to a third example of the present invention.

Fig. 4 shows a secondary battery according to a fourth example of the present invention.

Fig. 5 is a secondary battery according to a fifth example of the present invention.

Fig. 6 is a secondary battery in which a diode is added to the secondary battery of the first example.

Fig. 7 shows a secondary battery in which the main switching element of the secondary battery of the first example is disposed on the 1 st output terminal side.

Fig. 8 shows a secondary battery using a first example of a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 9 shows a secondary battery of a second example using a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 10 shows a secondary battery of a third example using a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 11 shows a secondary battery of a fourth example using a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 12 shows a fifth example of a secondary battery using a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 13 shows a secondary battery in which a diode is added to the secondary battery of the first example using a p-tunnel MOSFET or a pnp bipolar transistor.

Fig. 14 shows a secondary battery in which a main switching element of a secondary battery using a first example of a p-tunnel MOSFET or a pnp bipolar transistor is disposed on the 1 st output terminal side.

Fig. 15 is a secondary battery in which an output terminal of a voltage detection circuit and a gate terminal of an auxiliary switching element are connected through an auxiliary fuse circuit.

Fig. 16 is a conventional secondary battery.

In the drawings, reference numerals 101 to 107, 201 to 207, and 301 denote secondary batteries. Reference numeral 128 denotes a 1 st output terminal. Reference numeral 129 denotes a 2 nd output terminal. Reference numeral 114 denotes a main switching element (temperature detection portion). Reference numerals 122, 222, 322 denote auxiliary switching elements. Reference numerals 133, 143, 153, 233, 243, 253, 300 denote fusing elements (thermosensitive elements). Reference numeral 136 denotes a heating element. Reference numeral 135a denotes a 1 st auxiliary fusing element. Reference numeral 135b denotes a 2 nd auxiliary fusing element. Reference numerals 163 and 263 denote thermistors (heat sensitive elements).

Detailed Description

Reference numeral 101 in fig. 1 denotes a secondary battery according to a first example of the present invention.

The secondary battery 101 includes an electric storage device 111, a control circuit 115, a protection circuit 61, and a main switching element 114.

The turning on and off of the main switching element 114 is controlled by the control circuit 115, but in the following description it is assumed that the main switching element 114 is maintained in a turned-on state.

The high-voltage side output terminal a of the power storage device 111 is connected to the 1 st output terminal 128 via the protection circuit 61, and the ground side output terminal b of the power storage device 111 is connected to the 2 nd output terminal 129 via the main switching element 114.

The power storage device 111 is configured to be capable of repeating charging and discharging, and when the charging device 113 is connected to the 1 st and 2 nd output terminals 128 and 129, a charging current supplied from the charging device 113 flows through the protection circuit 112 and the main switching element 114, and the charging current charges the power storage device 111.

When an external circuit such as a portable personal computer is connected in place of the charging device 113, a discharge current generated by discharging the power storage device 111 flows through the protection circuit 61 and the main switching element 114, and is supplied to the external circuit.

The protection circuit 61 includes a voltage detection circuit 121, an auxiliary switching element 122, a main fuse circuit 51, and an auxiliary fuse circuit 124.

The auxiliary fusing circuit 124 includes 1 st and 2 nd auxiliary fusing elements 135a and 135b and a heating element 136 electrically composed of a heat resistive body.

The 1 st and 2 nd auxiliary fuse elements 135a and 135b are connected in series, and the 1 st auxiliary fuse element 135a side terminal and the 1 st output terminal 128 are connected in the series circuit, and the 2 nd auxiliary fuse element 135b side terminal and the high voltage side output terminal a of the power storage device 111 are connected in the series circuit. Therefore, the high-voltage side terminal of the power storage device 111 is connected to the 1 st output terminal 128 via the series circuit of the 1 st and 2 nd auxiliary fuse elements 135a and 135 b.

The auxiliary switching element 122 is an n-tunnel MOSFET or an npn bipolar transistor, and if it is an n-tunnel MOSFET, its source terminal is connected to the ground-side output terminal b of the power storage device 111. One end of the heating element 136 is connected to the drain terminal of the auxiliary switching element 122, and the other end of the heating element 136 is connected to a point where the 1 st and 2 nd auxiliary fuse elements 135a and 135b are connected to each other.

In the secondary battery 101 of the first example, the gate terminal of the auxiliary switching element 122 is connected to the output side terminal c of the voltage detection circuit 121.

The main fuse circuit 51 includes 1 st and 2 nd voltage-dividing resistance elements 131 and 132 and a main fuse element 133, and a gate terminal of the auxiliary switching element 122 is connected to a high-voltage side output terminal a of the power storage device 111 through the 1 st voltage-dividing resistance element 131.

At the same time, the gate terminal of the auxiliary switching element 122 is connected to the ground-side output terminal b of the power storage device 111 through the series circuit of the 2 nd voltage-dividing resistance element 132 and the main fuse element 133.

During normal charging or normal discharging of power storage device 111, voltage detection circuit 121 does not output a signal, and is in an off state.

When the resistance value of the main fuse element 133 is ignored in this state, the voltage divided by the 1 st voltage-dividing resistance element 131 and the 2 nd voltage-dividing resistance element 132 is applied to the gate terminal of the auxiliary switching element 122 from the voltage output from the power storage device 111.

This voltage is a voltage smaller than the threshold voltage of the auxiliary switching element 122, and the auxiliary switching element 122 is placed in an off state.

When the voltage detection circuit 121 detects a voltage higher than the upper limit voltage from this state, a high voltage signal is output and the auxiliary switching element 122 is turned on.

Although no current flows into the heating element 136 while the auxiliary switching element 122 is in the off state, if the drain terminal is connected to the ground-side output terminal b by conduction, a voltage is applied across the heating element 136, and a current flows into the heating element 136.

Both the current supplied by the charging device 113 and the current supplied by the electrical storage device 111 in this state flow into the heating element 136.

The heating element 136 generates heat by the inflow of current, and the 1 st and 2 nd auxiliary fusing elements 135a and 135b are fused by the heat.

Since the 1 st and 2 nd auxiliary fusing elements 135a and 135b are fused, the current from the charging device 113 and the current from the power storage device 111 are stopped, respectively, and the current no longer flows into the heating element 136.

In this state, the high-voltage side output terminal a of the power storage device 111 is disconnected from the 1 st output terminal 128, and thus current no longer flows, and as a result, an accident such as smoke can be prevented.

On the other hand, even if the state of charge of power storage device 111 is normal, there may be a case where a short circuit occurs between output terminals 128 and 129 of the 1 st and 2 nd outputs, causing an overcurrent to flow into main switching element 114, or a case where main switching element 114 fails, causing an overcurrent to flow into main switching element 114.

In this case, although the voltage detection circuit 121 does not operate, the main fuse element 133 and the main fuse elements (reference numerals 143, 153, 233, 243, 253, and 300) of the following embodiments are arranged in close contact with the main switch element 114 of the present embodiment and the following embodiments, and when the main switch element 114 generates heat due to an overcurrent, the main fuse element 133 is thermally fused.

Therefore, if the main switching element 114 serves as a temperature detection portion, when the main fuse element 133 is blown off by heat generated from the temperature detection portion, the connection between the gate terminal of the auxiliary switching element 122 and the ground-side output terminal through the 2 nd voltage-dividing resistance element 132 is cut off, and as a result, the gate terminal is pulled up (pull up) through the 1 st voltage-dividing resistance element 131, and the auxiliary switching element 122 is turned on.

Due to this conduction, a large discharge current of the power storage device 111 flows into the heating element 136, and heat is generated.

When the 2 nd auxiliary fusing element 135b is fused by the discharge current, the high-voltage side output terminal a of the power storage device 111 is disconnected from the 1 st output terminal 128 and the heating element 136, the discharge current stops, and accidents such as smoke can be prevented.

In contrast, when a charging device having an excessively large output voltage is connected between the 1 st and 2 nd output terminals 128 and 129 and the voltage detection circuit 121 does not operate at this voltage, as described above, when an overcurrent flows into the main switching element 114, the main fuse element 133 is fused by heat, the auxiliary switching element 122 is turned on, the heating element 136 generates heat, the 1 st auxiliary fuse element 125a is fused, and the charging device is disconnected from the 1 st output terminal 128, and the overcurrent is stopped.

Although the case where the output-side terminal c of the voltage detection circuit 121 is off in the normal operating state has been described above, the case where the voltage detection circuit 121 outputs a low voltage smaller than the threshold voltage and turns off the auxiliary switching element 122 in the normal operating state is also included.

In this case, since the current flowing through the 1 st voltage-dividing resistance element 131 flows into the voltage detection circuit 121 after the main fuse element 133 is blown, if the output impedance of the voltage detection circuit 121 is too low, the voltage of the gate terminal of the auxiliary switching element 122 may not be increased and may not be switched to the on state.

In this case, as in the secondary battery 106 shown in fig. 6, if the diode element 137 is provided in the main fusing circuit 55, the output side terminal c of the voltage detection circuit 121 is connected to the anode terminal thereof, the cathode terminal thereof is connected to the gate terminal of the auxiliary switching element 122, and the diode element 137 is reverse-biased after the main fusing element 133 is fused, the current flowing into the 1 st voltage-dividing resistance element 131 is blocked by the diode element 137 and does not flow into the voltage detection circuit 121 any more, so that the auxiliary switching element 122 can be reliably turned on even if the output impedance of the voltage detection circuit 121 is small.

Although the case where both of 1 st and 2 nd auxiliary fusing elements 135a and 135b are fused has been described above, power storage device 111 is disconnected from charging device 113 as long as any 1 of 1 st and 2 nd fusing elements are fused, and therefore, accidents such as smoke can be prevented.

However, it is also possible to set: even if only any 1 of the fuse elements is first fused, current can be continuously supplied to the heating element 136 through the other fuse element, and thus the remaining one fuse element can be fused by the heating element 136.

Next, fig. 2 shows a secondary battery 102 of a second example in which the configuration of the protection circuit 62 is different from that of the main fusing circuit 51 of the first example. In the secondary battery 102 of the second example and the secondary batteries 103 to 107, 201 to 207, and 301 of the following embodiments, the same reference numerals are attached to the same structures as those of the secondary battery 101 of the first example, and descriptions thereof and the connection states thereof are omitted.

In the main fuse circuit 52 of the secondary battery 102 according to the second example, the gate terminal of the auxiliary switching element 122 is connected to the high-voltage side output terminal a of the power storage device 111 via the 1 st voltage-dividing resistance element 141, and the output side terminal c of the voltage detection circuit 121 is connected to the ground side output terminal b via the 2 nd voltage-dividing resistance element 142.

In addition, the gate terminal of the auxiliary switching element 122 is short-circuited to the output side terminal c of the voltage detection circuit 121 by the main fuse element 143.

When the main switching element 114 generates heat due to overcurrent or the like and the main fusing element 143 is fused by heat, the gate terminal of the auxiliary switching element 122 and the output side terminal c of the voltage detection circuit 121 are disconnected. Therefore, the current flowing through the 1 st voltage-dividing resistance element 141 does not flow into the voltage detection circuit 121, and therefore the voltage at the high-voltage-side output terminal a of the power storage device 111 can be applied to the gate terminal of the auxiliary switching element 122 through the 1 st voltage-dividing resistance element 141, and the auxiliary switching element 122 is reliably turned on.

In the power supply devices 101 and 102 of the first and second examples, the power supply voltage side terminal d and the ground side terminal e of the voltage detection circuit 121 are directly connected to the high voltage side output terminal a and the ground side output terminal b of the power storage device 111, respectively, but it is also possible to change the state in which the voltage detection circuit 121 is stopped by blowing the main fuse element, thereby reliably turning on the auxiliary switch element 122.

Reference numeral 103 in fig. 3 denotes a secondary battery of a third example of such a structure. In the secondary battery 103 of the third example, the main fuse circuit 53 of the protection circuit 63 has the gate terminal of the auxiliary switching element 122 connected to the high-voltage side output terminal a via the 1 st voltage-dividing resistance element 151, and has the gate terminal connected to the ground side output terminal b via the series circuit of the 2 nd voltage-dividing resistance element 152 and the main fuse element 153.

In the series circuit of the 2 nd voltage-dividing resistive element 152 and the main fuse element 153, the terminal on the 2 nd voltage-dividing resistive element 152 side is connected to the gate terminal of the auxiliary switch element 122, and the terminal on the main fuse element 153 side is connected to the ground side output terminal b.

The power supply voltage side terminal d of the voltage detection circuit 121 is directly connected to the high voltage side output terminal a, and the ground side terminal e is connected to a portion where the 2 nd voltage-dividing resistive element 152 and the main fuse element 153 are connected. Therefore, the ground side terminal e of the voltage detection circuit 121 is connected to the ground side output terminal b via the main fuse element 153.

In such a configuration, if the main switching element 114 generates heat and the main fuse element 153 fuses, the ground side terminal e of the voltage detection circuit 121 is disconnected from the ground side output terminal b, and the operation is stopped.

Therefore, the current flowing through the 1 st voltage-dividing resistive element 151 does not flow to the ground-side output terminal b through the voltage detection circuit 121, and therefore the voltage of the gate terminal of the auxiliary switching element 122 does not decrease, and since the main fuse element 153 melts, the gate terminal of the auxiliary switching element 122 is pulled up to the high-voltage-side output terminal a through the 1 st voltage-dividing resistive element 151, and the auxiliary switching element 122 is reliably turned on.

While the secondary batteries 101 to 103, 106 have been described above using the main switching element 114 as the temperature detection portion, and the main fusing element 153 is fused by heat generation of the main switching element 114, other components, for example, the power storage device and the control circuit 115 may be used as the temperature detection portion in each of the above-described embodiments and the following embodiments, and the auxiliary switching element may be turned on by closely disposing a heat sensitive element such as the main fusing element 153 to the temperature detection portion.

In the secondary batteries 101 to 103 and 106, the primary fuse element 153 is used as a thermistor, and the resistance value of the thermistor increases infinitely due to a temperature rise, but the primary fuse elements 133, 143 and 153 of the above embodiments may be replaced with a thermistor whose resistance value increases or decreases with a temperature rise.

For example, reference numeral 104 in fig. 4 denotes a secondary battery of a fourth example in which the primary fuse element 133 of the secondary battery 101 of the first example shown in fig. 1 is replaced with a thermistor 162 whose resistance value increases with an increase in temperature.

In the secondary battery 104 of the fourth example, the main fuse circuit 54 included in the protection circuit 64 is configured by a series circuit of a voltage-dividing resistance element 161 and a thermistor 162, and the gate terminal of the auxiliary switching element 122 is connected to the high-voltage-side output terminal a via the voltage-dividing resistance element 161 and to the ground-side output terminal b via the thermistor 162.

The thermistor 162 is disposed in close contact with the surface of the main switching element 114, thereby improving thermal coupling. Therefore, if the main switching element 114 generates heat due to a failure, an overcurrent, or the like, the resistance value of the thermistor 162 increases due to heat, and the potential of the gate terminal of the auxiliary switching element 122 increases. Further, if the potential of the gate terminal becomes a voltage larger than the threshold voltage, the auxiliary switching element 122 is turned on.

In the above embodiments, the auxiliary fuse circuit 124 includes the 1 st and 2 nd auxiliary fuse elements 135a and 135b, but the 2 nd auxiliary fuse element 135b is not necessarily required.

For example, reference numeral 105 in fig. 5 denotes a secondary battery in which the no 2 nd auxiliary fusing element 135b is provided for the secondary battery 101 of the first example shown in fig. 1.

In the secondary battery 105, the heating element 136 generates heat by the auxiliary switching element 122 being turned on, the 1 st auxiliary fusing element 135a is fused, and the 1 st output terminal 128 is disconnected from the internal circuit of the secondary battery 105.

In the above embodiments, the main switching element 114 is provided between the 2 nd output terminal 129 and the ground side output terminal b, but may be provided between the 1 st output terminal 128 and the auxiliary fuse circuit 124 as shown in fig. 7. In this case, the structure is: the main fusing element 133 is also closely arranged to the main switching element 114, and the main switching element 114 is heated and fused by an overcurrent. When a thermistor is used instead of the main fuse element 133, the resistance value may be increased by heat generation of the main switching element 114.

In the above embodiments, the auxiliary switching element 122 is an n-tunnel MOSFET or an npn bipolar transistor, but a relay element or another switching element may be used instead of a p-tunnel MOSFET or a pnp bipolar transistor.

In each of the secondary batteries 101 to 107 using an n-tunnel MOSFET or an npn bipolar transistor, the gate terminal or the base terminal of the auxiliary switching element 122 is connected to the ground side output terminal b by the elements 133, 143, 153, and 162 (including elements whose resistance value increases infinitely after fusing) whose resistance value increases due to heat generation of the main switching element 114; however, when a p-tunnel MOSFET or a pnp bipolar transistor is used and an element whose resistance value increases due to heat generation of the main switching element 114 caused by an overcurrent is connected to the gate terminal or the base terminal, the gate terminal or the base terminal is connected to the high-voltage-side output terminal a through the element.

Such secondary batteries are denoted by reference numerals 201 to 207 in fig. 8 to 14, which correspond to the secondary batteries 101 to 107 in fig. 1 to 7. The main fuse circuits corresponding to the main fuse circuits 51 to 55 shown in FIGS. 1 to 7 are denoted by reference numerals 71 to 75, and the 1 XX sign of the elements in the main fuse circuits 51 to 55 is changed to the 2 XX sign in the main fuse circuits 71 to 75.

In the secondary batteries 201 to 207 of fig. 8 to 14, the output side terminal c of the voltage detection circuit 221 is also in an off state in a normal operation state, and a voltage obtained by dividing the voltage between the high-voltage side output terminal a and the ground side output terminal b by the fuse circuits 71 to 75 is applied to the gate terminal or the base terminal of the auxiliary switching element 222.

The auxiliary switching element 222 is configured to maintain an off state when the voltage is applied.

In addition, there is also a case where the output side terminal c of the voltage detection circuit 221 is not in an off state and a high voltage is output in order to turn off the auxiliary switching element 222.

If the main switching element 114 generates heat due to an overcurrent, the main fuse elements 233, 243, and 253 fuse, or the resistance value of the thermistor 262 increases, a low voltage close to the potential of the ground-side output terminal b is applied to the gate terminal or the base terminal of the auxiliary switching element 222.

Since the auxiliary switching element 222 is formed of a p-tunnel MOSFET or a pnp bipolar transistor, if a low voltage is applied, it is turned on, and a current flows into the heating element 136, so that the 1 st and 2 nd auxiliary fuse elements 135a and 135b are blown.

In this case, as shown in fig. 10, the following can be constructed: that is, in order to melt the main fuse element 253, the voltage detection circuit 221 is stopped, the power supply side voltage terminal d of the voltage detection circuit 221 is connected between the main fuse element 253 and the 2 nd voltage-dividing resistance element 252 connected in series, and the power supply side terminal d is disconnected from the high-voltage side output terminal a by melting the main fuse element 253.

As shown in fig. 13, if the diode element 237 is connected to the output side terminal c of the voltage detection circuit 221, when the gate terminal of the auxiliary switch element 222 is pulled down (pulldown) by the 1 st resistance element 231 and the auxiliary switch element 222 is turned on after the main fuse element 233 is melted, the current output from the voltage detection circuit 221 can be blocked by directing the anode terminal toward the gate terminal and directing the cathode terminal toward the output side terminal c of the voltage detection circuit 221 so as not to increase the potential of the gate terminal by the current output from the voltage detection circuit 221.

The above embodiments, together with the secondary battery 301 shown in fig. 15, are included in the invention.

In the secondary battery 301, an output side terminal c of the voltage detection circuit 321 and a gate terminal or a base terminal of the auxiliary switch element 322 are connected through the auxiliary fuse element 300.

The voltage detection circuit 321 is configured to detect a normal voltage, turn off the auxiliary switching element 322 while a signal indicating the normal voltage is input to the auxiliary switching element 322, and turn on the auxiliary switching element 322 if the signal indicating the normal voltage is no longer input to the auxiliary switching element 322.

If an overcurrent flows into the main switching element 114 and the main fuse element 300 is blown out by heat, the signal detected as the normal voltage by the voltage detection circuit 321 is not inputted to the gate terminal of the auxiliary switching element 322 regardless of the signal outputted from the voltage detection circuit 321, and therefore, if the main fuse element 300 is blown out, the auxiliary switching element 322 is always turned on, and a current can flow into the heat generation resistance element 136, and the 1 st and 2 nd auxiliary fuse elements 135a and 135b are blown out.

In the circuit diagram of fig. 11, if an n-tunnel MOSFET or an npn transistor is used as the auxiliary switching element 222 and an element whose resistance value decreases with an increase in temperature is used as the thermistor 262, the auxiliary switching element 222 can be turned on by heat generation of the main switching element 114 due to overcurrent, as in the above-described embodiments.

Effects of the invention

Since the main fuse element is not disposed on the path of the charge/discharge current of the power storage device, no energy loss is caused by the main fuse element during normal operation. In addition, a main fuse element having a small current capacity can be used.

Claims (6)

1. A secondary battery includes an electric storage device, a protection circuit, an auxiliary switching element, a heating element, a 1 st auxiliary fusing element, 1 st and 2 nd output terminals, and a temperature detection portion, and is configured such that:

when a charging device is connected to the 1 st and 2 nd output terminals, a charging current supplied from the charging device flows through the protection circuit to charge the power storage device,

when an external circuit is connected to the 1 st and 2 nd output terminals, a discharge current of the power storage device flows through the protection circuit and is supplied to the external circuit,

the protection circuit includes a series circuit in which a 1 st voltage-dividing resistance element, a 2 nd voltage-dividing resistance element, and a main fuse element are connected in series,

the series circuit is connected between a high-voltage-side output terminal and a ground-side output terminal of the power storage device,

before the main fuse element is blown, a voltage between the high-voltage-side output terminal and the ground-side output terminal is divided by the 1 st voltage-dividing resistive element and the 2 nd voltage-dividing resistive element to generate a divided voltage,

the divided voltage is input to a control terminal of the auxiliary switching element, the auxiliary switching element is placed in an off state,

if the main fuse element is fused by heat generation at the temperature detection portion closely arranged thereto, the control terminal of the auxiliary switch element is set to be connected to the high-voltage side output terminal through the 1 st or 2 nd voltage-dividing resistance element or to the ground side output terminal through the 1 st or 2 nd voltage-dividing resistance element, the auxiliary switch element becomes a conductive state, and the heating element is energized and generates heat by conduction of the auxiliary switch element,

the 1 st output terminal is disconnected from the power storage device and the heating element when the 1 st auxiliary fusing element is fused by heat generated by the heating element.

2. The secondary battery according to claim 1, wherein:

the protection circuit includes a 2 nd auxiliary fusing element that fuses due to heat generation of the heating element to disconnect the auxiliary switching element from the power storage device and stop a current flowing into the auxiliary switching element.

3. The secondary battery according to claim 1 or 2, wherein a main switching element is provided on a path through which the charging current and the discharging current flow, and the main switching element controls the flow of the charging current and the discharging current, wherein:

the temperature detection portion is a main switching element.

4. The secondary battery according to claim 1 or 2,

a voltage detection circuit that detects a voltage between the high-voltage-side output terminal and the ground-side output terminal of the electrical storage device is provided,

the output terminal of the voltage detection circuit is connected to the control terminal of the auxiliary switching element and is arranged to put the auxiliary switching element into conduction if the voltage detection circuit detects a voltage above the upper limit voltage.

5. The secondary battery according to claim 4, wherein the secondary battery further comprises a battery case,

a diode element is interposed between the output terminal of the voltage detection circuit and the control terminal of the auxiliary switching element, and the voltage detection circuit is disconnected from the auxiliary switching element by reverse biasing the diode element after the primary fuse element is fused.

6. The secondary battery according to claim 1 or 2,

the auxiliary switching element is a transistor.