CN101728842A - Battery case - Google Patents

Abstract

The invention aims to provide a battery case being capable of carrying out temperature protection on a storage battery with high precision, preventing self heating in discharging and carrying out proper charging stop control. When a thermistor (R13) detects that the temperature of a lithium-ion storage battery (12) exceeds the predetermined temperature, the battery case (10A) conducts an MOS transistor (M13) so as to enable the voltage between external terminals (14) and external terminals (TH) of terminals (32 and 33) connected to a charging device (30) to be smaller or equal to the predetermined voltage, thereby stopping the charging of the charging device (30).

Description

Battery case

technical field

The present invention relates to a battery case, in particular to a protection circuit with a protection circuit for closing a switching element provided between a secondary battery and a load or between a secondary battery and a charging device by detecting overcharge, overdischarge, or overcurrent of a secondary battery Battery case.

Background technique

In recent years, lithium ion batteries have been installed in portable devices such as digital cameras as secondary batteries. Since lithium-ion batteries are difficult to withstand overcharge and overdischarge, they are put into use in the form of battery boxes with overcharge and overdischarge protection circuits.

4 and 5 show block diagrams of various examples of conventional battery packs. In FIG. 4 , a series circuit of a resistor R1 and a capacitor C1 is connected to the lithium ion battery 2 in parallel. The positive electrode of the lithium ion battery 2 is connected to the external terminal 3 of the battery case 1, and the negative electrode is connected to the external terminal 4 of the battery case 1 through n-channel MOS (metal oxide film semiconductor) transistors M1 and M2 for current interruption.

The drains of the MOS transistors M1 and M2 are connected, the source of the MOS transistor M1 is connected to the negative electrode of the lithium ion battery 2 , and the source of the MOS transistor M2 is connected to the external terminal 4 . In addition, body diodes D1 and D2 are equivalently connected between the drain and the source of each of the MOS transistors M1 and M2 .

The protection IC (Integrated Circuit) 5 incorporates an overcharge detection circuit, an overdischarge detection circuit, and an overcurrent detection circuit. The protection IC5 works by connecting the positive electrode of the lithium-ion battery 2 to the power supply Vdd through the resistor R1 and connecting the negative electrode of the lithium-ion battery 2 to the power supply Vss.

When the protection IC5 detects over-discharge or over-current through the over-discharge detection circuit or over-current detection circuit, the output of DOUT is low (low) to disconnect the connection of the MOS transistor M1; When charging, make the output of COUT low (low) to disconnect the connection of the MOS transistor M2.

In FIG. 5 , a thermistor R3 is further provided in the battery case 1 . One end of the thermistor R3 is connected to the terminal 6 of the battery case 1 , and the other end is connected to the external terminal 4 . When charging, the terminal 6 of the battery case 1 receives a certain voltage from the charging device through the voltage dividing resistor. Since the resistance value of the thermistor R3 changes according to the temperature of the battery case 1, the voltage of the terminal 6 changes. The charging device detects the voltage of the terminal 6, and stops charging when the temperature of the battery box 1 exceeds a predetermined value.

Here, Japanese Patent Laid-Open No. 2004-152580 describes that a diode connected in series to a temperature protection element (PTC element) and a diode connected in antiparallel to these elements are connected to a secondary battery so that even during normal discharge When the temperature reaches high temperature, the temperature protection element (PTC element) will not work.

The existing example shown in FIG. 4 has no protection function for the temperature of the battery case. However, the existing example shown in Fig. 5 has a temperature protection function for the battery box, but because the battery box is connected to a certain voltage from the charging device through the voltage dividing resistor, when the predetermined voltage of the charging device changes or the charging When there is an error in the voltage dividing resistance of the device, it is difficult to accurately detect the temperature of the battery case, and it is difficult to perform accurate control to stop charging.

Contents of the invention

The present invention is made to solve the above-mentioned problems, and its object is to provide a battery that can accurately protect the temperature of the secondary battery, prevent self-heating during discharge, and perform appropriate control to stop charging. box.

The present invention employs the following structures in order to solve the above object.

The battery case of the present invention comprises: first to third external terminals (13, 14, TH) connected to the positive and negative power supply terminals (31, 32) of the charging device and the voltage detection terminals, as the voltage detection terminals When the voltage of (33) is lower than the predetermined voltage, the charging device stops charging; the secondary battery (12) connected between the first external terminal and the third external terminal; A protection circuit (15A) that controls the on/off of the first and second switching elements (M11, M12) for charging, over-discharging, and over-current, and the first and second switching elements (M11, M12) are arranged on the wiring between a secondary battery and a load or between the secondary battery and the charging device; a first thermal sensor provided between the second external terminal (14) and the third external terminal (TH) A resistor (R23); wherein, the battery case (10A) has a series connection of a second thermistor (R13) and a resistor (R14) arranged in the vicinity of the secondary battery (12) and connected in parallel with the secondary battery a circuit, the third switching element (M13) connected between the second external terminal (14) and the third external terminal (TH), when the second thermistor (R13) detects the When the temperature of the secondary battery (12) exceeds a predetermined temperature, the protection circuit (15A) turns on the third switching element (M13), by making the second external terminal (14) and the third external Short-circuit between terminals (TH), high-precision temperature protection of the secondary battery, self-heating during discharge can be prevented, and appropriate control to stop charging can be performed.

The third switching element (M13) may be a MOS transistor.

The first and second thermistors (R23, R13) may be NTC thermistors with a negative temperature coefficient.

It should be noted that the reference symbols in the parentheses are just an example added for easy understanding, and are not limited to the illustrated content.

Description of drawings

FIG. 1 is a block diagram of a reference example of a battery case of the present invention.

Fig. 2 is a diagram showing temperature and resistance characteristics of an NTC thermistor and a PTC thermistor, respectively.

Fig. 3 is a block diagram of one embodiment of the battery case of the present invention.

FIG. 4 is a block diagram of an example of a conventional battery case.

Fig. 5 is a block diagram of another example of a conventional battery case.

Description of main symbols:

10, 10A is the battery box, 12 is the lithium ion battery, 13, 14 is TH external terminal, 15, 15A is the protection IC, 16 is the overcharge detection circuit, 17 is the over discharge detection circuit, 18 is the overcurrent detection circuit, 19 20 is a voltage regulator, 21 and 38 are comparison circuits, 22 is a non-inductive time setting circuit, 30 is a charging device, 31, 32, and 33 are terminals, 34 is a reference voltage, 36 is a current source, and 39 It is a charging control circuit, M11, M12, M13, M40 are MOS transistors, R11, R12, R35 are resistors, R13, R23 are thermistors.

BEST MODE FOR CARRYING OUT THE INVENTION

(reference example)

FIG. 1 is a block diagram of a reference example of a battery case of the present invention. In the drawing, a series circuit of a resistor R11 and a capacitor C11 is connected in parallel to the lithium ion battery 12 . The positive pole of the lithium-ion battery 12 is connected to the external terminal 13 of the battery case 10 by a line, and the negative pole is connected to the external terminal 14 of the battery case 10 by a line through n-channel MOS transistors M11 and M12 for current interruption.

The drains of the MOS transistors M11 and M12 are connected, the source of the MOS transistor M11 is connected to the negative electrode of the lithium ion battery 12 , and the source of the MOS transistor M12 is connected to the external terminal 14 . Furthermore, body diodes D11 and D12 are equivalently connected between the drain and the source of each of the MOS transistors M11 and M12 .

A series circuit of a thermistor R13 and a resistor R14 is connected in parallel to the lithium ion battery 12 . The above-mentioned thermistor R13 is arranged near the lithium ion battery 12 in the battery case, and is thermally bonded to the lithium ion battery 12 . Thermistor R13 uses an NTC (Negative Temperature Coefficient) thermistor with a negative temperature coefficient.

The temperature and resistance characteristics of an NTC thermistor with a negative temperature coefficient and a PTC (Positive Temperature Coefficient) thermistor with a positive temperature coefficient are shown in Figure 2, respectively.

The protection IC (Integrated Circuit) 15 incorporates an overcharge detection circuit 16 , an overdischarge detection circuit 17 , and an overcurrent detection circuit 18 . The protection IC 15 operates by connecting the power supply Vdd to the terminal 15a from the positive pole of the lithium ion battery 12 through the resistor R11 and connecting the power supply Vss to the terminal 15c from the negative pole of the lithium ion battery 12 .

The overcharge detection circuit 16 detects overcharge of the lithium ion battery 12 from the voltages of the terminals 15 a and 15 c, and supplies a detection signal to the logic circuit 19 . The overdischarge detection circuit 17 detects overdischarge of the lithium ion battery 12 from the voltages of the terminals 15 a and 15 c, and supplies a detection signal to the logic circuit 19 . The overcurrent detection circuit 18 detects that the current flowing into the resistor R12 is an excessive overcurrent from the voltages of the terminals 15c and 15f, and supplies a detection signal to the logic circuit 19 .

The protection IC 15 is connected to the connection point A of the thermistor R13 and the resistor R14 at the terminal 15b, one end of the resistor R12 is connected to the terminal 15f, and the other end of the resistor R12 is connected to the external terminal 14. The protection IC 15 connects the DOUT output terminal 15d to the gate of the MOS transistor M11, and connects the COUT output terminal 15e to the gate of the MOS transistor M12.

In the protection IC 15 , the terminal 15 b is connected to the non-inverting input terminal of the comparison circuit 21 . The terminal 15c is connected to the negative pole of a voltage stabilizing source 20 such as a Zener diode, and the positive pole of the voltage stabilizing source 20 is connected to the inverting input terminal of the comparator circuit 21.

As shown in Figure 2, since the thermistor R13 is an NTC thermistor with a negative temperature coefficient, the resistance value becomes lower as the temperature rises, causing the voltage at the connection point A to rise.

The comparison circuit 21 has a hysteresis characteristic, and by comparing the constant voltage V1 generated by the constant voltage source 20 with the voltage at the connection point A, when the voltage at the connection point A is high, it outputs a high signal. That is, when the detected temperature of the thermistor R13 exceeds a predetermined temperature (for example, about 70° C.) corresponding to the constant voltage V1, the comparison circuit 21 outputs a high signal as a high temperature detection signal.

The high temperature detection signal output by the comparison circuit 21 is supplied to the non-sensing time setting circuit 22 . When the high signal maintaining time of the high temperature detection signal exceeds a predetermined value (for example, 0.5 sec), the non-sensing time setting circuit 22 supplies the high high temperature detection signal to the logic circuit 19 .

The logic circuit 19 respectively receives the detection signals from the overcharge detection circuit 16 , the overdischarge detection circuit 17 , and the overcurrent detection circuit 18 , and also receives the high temperature detection signal output by the non-sensing time setting circuit 22 .

When the logic circuit 19 detects the overcharge detection signal by the overcharge detection circuit 16, the output of the COUT of the terminal 15e is low (low) to disconnect the connection of the MOS transistor M12; when the logic circuit 19 passes the overdischarge detection circuit 17 When the over-discharge detection signal is detected, the output of the DOUT of the terminal 15d is low (low) to disconnect the connection of the MOS transistor M11; when the logic circuit 19 detects the over-current detection signal by the over-current detection circuit 18, the terminal The output of DOUT of 15d is low (low) to disconnect the connection of the MOS transistor M11.

When the high temperature detection signal is high, the logic circuit 19 makes the output of COUT of the terminal 15e low to disconnect the MOS transistor M12. Accordingly, the temperature of the lithium ion battery 12 can be accurately detected, and when the temperature of the lithium ion battery 12 reaches a high temperature, charging can be stopped to protect the battery.

Since the thermistor R13 uses an NTC thermistor, and the NTC thermistor is shown in Figure 2, the resistance value changes nearly linearly with respect to the temperature, so the temperature can be detected with high precision. Furthermore, since the thermistor R13 is arranged near the lithium ion battery 12 in the battery case 10, the temperature of the lithium ion battery 12 can be detected with high accuracy. Here, since the resistance value of the PTC thermistor rapidly increases above a certain temperature, the temperature cannot be detected with high accuracy.

When the output of COUT is low and the connection of the MOS transistor M12 is disconnected, when a load is connected between the external terminals 13 and 14, the output of DOUT is high and the MOS transistor M11 is turned on, so the body diode of the MOS transistor M12 D12 is turned on, and the discharge current of the lithium ion battery 12 flows into the load connected between the external terminals 13 and 14 .

At this time, if the forward voltage drop of the body diode D12 is marked as Vf, and the discharge current is marked as Id, then the power Wd expressed as Wd=Vf×Id is released in the form of heat. Therefore, the battery case 10 may be further heated. The following examples illustrate the content of the control to prevent such self-heating and to perform appropriate stop charging.

(Example)

Fig. 3 is a block diagram showing an embodiment of the battery case of the present invention. In the drawings, the same parts as those in FIG. 1 are marked with the same symbols.

The battery case 10A of this embodiment is a battery case connected to a charging device 30 having three terminals and charged. Before describing the battery case 1OA of this embodiment below, the charging device 30 will be described.

The charging device 30 includes a terminal 31 , a terminal 32 , and a terminal 33 respectively connected to the external terminal 13 , the external terminal 14 of the battery case 10A, and an external terminal TH to be described later. Terminal 31 is a positive power supply terminal, and terminal 32 is a negative power supply terminal. The terminal 33 is a terminal for voltage detection for detecting the voltage between the terminal 32 and the terminal 33 . Furthermore, the charging device 30 includes a reference voltage 34, a resistor R35, a current source 36, a diode D37, a comparison circuit 38, a charging control circuit 39, and a MOS transistor M40.

One input terminal of the comparison circuit 38 inputs the voltage divided by the reference voltage 34 by the resistor R35 and the resistance between the terminal 32 and the terminal 33 , that is, the voltage between the input terminal 32 and the terminal 33 . The other input terminal of the comparator circuit 38 inputs the constant voltage VT generated by the current source 36 and the diode D37. When the voltage between the terminal 32 and the terminal 33 is less than or equal to the voltage VT, the output of the comparison circuit 38 changes. The output of the comparison circuit 38 is input to the charging control circuit 39 .

The charging control circuit 39 performs ON/OFF control of the MOS transistor M40 based on, for example, a charging current or a charging voltage. In this embodiment, when the battery case having the thermistor connected between the terminal 32 and the terminal 33 is connected, the charging of the battery case is stopped by detecting the temperature rise of the battery case. In this embodiment, when the resistance value of the thermistor decreases so that the voltage between the terminal 32 and the terminal 33 is less than or equal to the predetermined voltage VT, the charging control circuit 39 will not operate, and the MOS transistor 40 will be turned off to stop charging Charging the battery case.

Specifically, for example, when the voltage between the terminal 32 and the terminal 33 is less than or equal to the predetermined voltage VT, the output of the comparison circuit 38 is low. The charge control circuit 39 switches operation/non-operation based on the output of the comparison circuit 38 . When the output of the comparison circuit 38 is low, the charging control circuit 39 is in an inoperative state, and turns off the MOS transistor M40. That is, when the voltage between the terminal 32 and the terminal 33 is less than or equal to the predetermined voltage VT, the charging control circuit 39 turns off the MOS transistor M40 to stop charging the battery box. Here, in this embodiment, a p-channel MOS transistor is used as the MOS transistor M40. A constant current source may also be used instead of the reference voltage 34 .

Next, the battery case 10A of this embodiment will be described. The battery case 10A of this embodiment performs control to stop charging to the charging device 30 when the temperature of the battery case 10A reaches a high temperature.

The battery pack 10A of this embodiment is configured by providing the third external terminal TH, the thermistor R23 and the MOS transistor M13 connected in parallel between the external terminal TH and the external terminal 14 in the battery pack 10 described in the reference example. .

The protection IC 15A of this embodiment has an output terminal Tout that outputs a signal from the non-sensing time setting circuit 22, and the output terminal Tout is connected to the gate of the MOS transistor M13. When the detection temperature of the thermistor R13 exceeds a predetermined temperature and a high temperature detection signal is output from the non-sensing time setting circuit 22, a high signal of the output terminal Tout is input to the gate to turn on the MOS transistor M13. Here, the MOS transistor M13 is an n-channel MOS transistor.

Next, the case where the battery case 10A of this embodiment is connected to the charging device 30 will be described.

External terminals 13 , 14 , and TH of battery case 10A are connected to terminals 31 , 32 , and 33 of charging device 30 , respectively.

When the battery case 10A is connected to the charging device 30 , the voltage between the terminals 32 and 33 of the charging device 30 is a voltage obtained by dividing the reference voltage 34 by the resistor R35 and the thermistor R23 . In this embodiment, the value of the thermistor R23 is set to make the voltage between the terminal 32 and the terminal 33 higher than the predetermined voltage VT when the battery pack 10A is connected to the charging device 30 . The thermistor R23 of this embodiment is an NTC thermistor. In the charging device 30, when the temperature of the battery case 10A rises and the resistance value of the thermistor R23 drops, the reference voltage 34 is divided by the resistor R35 and the thermistor R23 (the voltage between the terminal 32 and the terminal 33). ) will decrease. When the resistance value of the thermistor R23 drops so that the divided voltage value is less than or equal to the predetermined voltage VT, the charging device 30 stops charging the battery case 10A.

When the high temperature detection signal is output from the non-sensing time setting circuit 22 in the state where the battery case 10A is connected to the charging device 30, the high signal output from the output terminal Tout of the protection IC 15A is input to the gate of the MOS transistor M13, The MOS transistor M13 is turned on. When the MOS transistor M13 is turned on, the external terminal 14 of the battery case 10A and the external terminal TH are short-circuited, and the voltage between the terminal 32 and the terminal 33 becomes less than or equal to the predetermined voltage VT. In the charging device 30, when the voltage between the terminal 32 and the terminal 33 is less than or equal to the predetermined voltage VT, the output of the comparison circuit 38 changes, the charging control circuit 39 turns off the MOS transistor M40, and stops charging the battery case 10A.

As described above, the battery case 10A of this embodiment has the MOS transistor M13 so that the voltage between the external terminal 14 and the external terminal TH can be made equal to or lower than the predetermined voltage VT when the temperature detected by the thermistor R13 exceeds a predetermined temperature. Therefore, the battery case 10A can stop charging from the charging device 30 to the battery case 10A by controlling the temperature of the battery case 10A.

Accordingly, according to the battery case 10A, even if the predetermined voltage VT of the charging device 30 changes or there is an error in the voltage dividing resistance of the charging device 30, the high temperature of the battery case 10A can be detected by the charging device 30, and the battery can be stopped accurately. Charging from the charging device 30 .

Since the battery case 10A of this embodiment controls charging stop by the MOS transistor M13 , it is not necessary to turn off the MOS transistor M12 in order to stop charging from the charging device 30 . Therefore, even if the high temperature detection signal is output from the non-sensing time setting circuit 22, the logic circuit 29 makes the output of COUT of the terminal 15e high to turn on the MOS transistor M12. Accordingly, the body diode D12 is not turned on, and self-heating of the battery case 10A can be prevented.

Accordingly, according to the battery case 10A of the present embodiment, not only self-heating can be prevented, but also charging stop can be appropriately controlled.

As mentioned above, although this invention was demonstrated based on an Example, this invention is not limited to the content shown in the said Example. Various changes can be made without exceeding the idea of the present invention, and appropriate changes can be made according to the application state.

Claims (3)

1. A battery box, comprising: connected to the positive and negative power supply terminals of the charging device and the first to third external terminals of the voltage detection terminal, when the voltage of the voltage detection terminal is lower than a predetermined voltage, the charging device stops charging, a secondary battery connected between the first external terminal and the third external terminal, A protection circuit that controls the on/off of the first and second switching elements by detecting overcharge, overdischarge, and overcurrent of the secondary battery, and the first and second switching elements are arranged between the secondary battery and the secondary battery. load or the wiring between the secondary battery and the charging device, a first thermistor disposed between the second external terminal and the third external terminal, The battery box is characterized in that it has a series circuit of a second thermistor and a resistor, the second thermistor being arranged near the secondary battery and connected in parallel with the secondary battery, a third switching element connected between the second external terminal and the third external terminal, When the second thermistor detects that the temperature of the secondary battery exceeds a predetermined temperature, the protection circuit turns on the third switching element, so that the second external terminal and the third external Short circuit between terminals. 2. The battery box according to claim 1, wherein the third switching element is a MOS transistor. 3. The battery box according to claim 1 or 2, wherein the first and second thermistors are NTC thermistors with a negative temperature coefficient.

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