JP2012157128A - Overvoltage detection device, protection device and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overvoltage detection device, a protection device and a battery pack, capable of preventing, when a charging current of a secondary battery increases, a protection circuit for detecting an overvoltage, higher than an overvoltage detected by software control, from detecting first an overvoltage state of a secondary battery.SOLUTION: The overvoltage state of a secondary battery 1 is detected when the number of continuous determination times that a battery voltage, detected at intervals of 250 msec and including a voltage drop produced in resistors (resistors Ra1, Ra2, Rb1, Rb2, Rc1, Rc2) in a charge path of the secondary battery 1, is higher than a prescribed voltage (4.3 V) for detecting the overvoltage state of the secondary battery 1 by a protection circuit 5 is greater than and including a second number of times (two times) smaller than the number of battery voltage detection times during 1.5 sec preceding the overvoltage detection by the protection circuit 5.

Description

  The present invention relates to an overvoltage detection device that detects an overvoltage of a secondary battery, a protection device including the overvoltage detection device, and a battery pack including the protection device.

  When charging a secondary battery represented by a lithium ion battery, constant current charging is performed at a predetermined current, and the terminal voltage (hereinafter referred to as battery voltage) is the maximum voltage allowed for the secondary battery (to prevent overcharging). A so-called constant-current / constant-voltage charging method, in which charging is performed by constant voltage charging after reaching a predetermined voltage set lower than the protection voltage), is mainly used. If the battery voltage exceeds the maximum voltage, the life of the battery (degree of deterioration) and charge / discharge capacity will be impaired, and there is a risk of ignition, so control is performed so that the battery voltage does not exceed the maximum voltage during charging. Is done.

  In order to ensure the prevention of overvoltage of the secondary battery, the protection circuit by hardware and the control circuit controlled by software are often performed twice. For example, in Patent Document 1, when the state in which the battery voltage is higher than the maximum setting voltage is longer than the minimum setting time, the protection circuit that detects that the secondary battery is in the maximum overcharge state, and the battery voltage are set to the maximum setting. A battery pack is disclosed that includes a control circuit that determines that a secondary battery is in an overcharged state when a state higher than a set voltage lower than the voltage is longer than a set time.

  By the way, during charging, a voltage drop generated in a member such as a wiring or a switching element interposed in the charging path is added to the net voltage of the secondary battery and detected as a battery voltage. The net charging voltage applied to the secondary battery after subtracting the drop changes to small / large according to the large / small charging current.

  On the other hand, in Patent Document 2, the net charging voltage applied to the secondary battery is obtained by detecting the battery voltage in which the voltage drop generated in the charging path due to the charging current is offset by the compensation voltage and performing constant voltage charging. A technique for making it constant is disclosed. By applying this type of technology to the control circuit as described above and determining the overvoltage based on the battery voltage minus the voltage drop that occurs in the charging path, it is possible to accurately determine that the secondary battery is in an overcharged state. Judgment is made.

JP 2004-127532 A JP 7-95733 A

  However, since the above-described protection circuit is usually realized by a general-purpose IC, and the voltage drop generated in the charging path cannot be subtracted by applying the technique of Patent Document 2, the charging current increases more than expected. In this case, there is a problem that the maximum overcharge state is detected by the protection circuit before the control circuit determines that the overvoltage state is present.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a protection circuit (hereinafter referred to as an overvoltage) higher than the overvoltage detected by software control when the charging current of the secondary battery increases. , Also referred to as a detection circuit) is to provide an overvoltage detection device, a protection device, and a battery pack that can prevent the secondary battery from detecting an overvoltage state first.

  The overvoltage detection device according to the present invention detects that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including the voltage drop in the charging path is continuously higher than the predetermined voltage for a predetermined time or more. A detection circuit that calculates the canceling voltage that cancels the voltage drop by detecting the battery voltage and the charging current in time series, and a voltage obtained by adding the calculated canceling voltage to the detected battery voltage is lower than the predetermined voltage; And a control circuit that detects that the secondary battery is in a first overvoltage state when the voltage is continuously higher than a voltage by a first number of times, the control circuit time-series the battery voltage. A determination unit that determines whether the detected voltage is higher than the predetermined voltage and a counting unit that counts the number of times the determination unit determines that the voltage is high, and the counting unit continuously counts The number of times is the predetermined time Wherein when the battery voltage is the second number of times or more less than the number to be detected, wherein the secondary battery are adapted to detect that it is in the second overvoltage condition.

In the present invention, when the voltage obtained by detecting the battery voltage including the voltage drop generated in the charging path of the secondary battery in time series is higher than the predetermined voltage at which the detection circuit detects the predetermined overvoltage state, it is continuous. When the number of times determined in this way is equal to or greater than a second number that is less than the number of times that the battery voltage is detected within a predetermined time until the predetermined overvoltage state is detected by the detection circuit, the control circuit performs the second operation of the secondary battery. Detects overvoltage condition.
As a result, even when there is a high probability that a predetermined overvoltage state is detected after a predetermined time in the detection circuit because the voltage at the time of charging the secondary battery to which the voltage drop is added is higher than the predetermined voltage. Prior to the circuit detecting a predetermined overvoltage condition, the control circuit detects a second overvoltage condition.

  The overvoltage detection device according to the present invention detects that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including the voltage drop in the charging path is continuously higher than the predetermined voltage for a predetermined time or more. A detection circuit that calculates the canceling voltage that cancels the voltage drop by detecting the battery voltage and the charging current in time series, and a voltage obtained by adding the calculated canceling voltage to the detected battery voltage is lower than the predetermined voltage; And a control circuit that detects that the secondary battery is in a first overvoltage state when the voltage is continuously higher than a voltage by a first number of times, wherein the control circuit has a magnitude of the cancellation voltage. Has a determination unit that determines whether or not is greater than a predetermined value smaller than the difference between the predetermined voltage and the first voltage, and a counting unit that counts the number of times that the determination unit has determined to be large. And counted When the number is equal to or more than a second number less than the number of times the battery voltage is detected within the predetermined time, the secondary battery is detected to be in a second overvoltage state. To do.

In the present invention, the voltage drop generated in the charging path of the secondary battery is less than the predetermined value smaller than the difference between the predetermined voltage and the first voltage at which each of the detection circuit and the control circuit detects the overvoltage state of the secondary battery. More than the second number of times that the number of times that the canceling voltage to be canceled is continuously determined is larger than the number of times that the battery voltage is detected within a predetermined time until the predetermined overvoltage state is detected by the detection circuit. If so, the control circuit detects the second overvoltage state of the secondary battery.
Thus, even if the first overvoltage state is difficult to be detected by the control circuit prior to the detection circuit because the magnitude of the voltage drop in the charging path is larger than the predetermined value, the detection circuit is in the predetermined overvoltage state. Prior to detecting, the control circuit detects a second overvoltage condition.

  The overvoltage detection device according to the present invention is characterized in that the first number of times is greater than the number of times the battery voltage is detected within the predetermined time.

In the present invention, the battery voltage is detected within a predetermined time required for the detection circuit to detect the predetermined overvoltage state based on the first number of times that the control circuit counts until the first overvoltage state is detected. More than the number of times.
As a result, a predetermined overvoltage state that has a higher possibility of degrading and damaging the secondary battery is quickly detected by the detection circuit.

  The overvoltage detection device according to the present invention detects that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including the voltage drop in the charging path is continuously higher than the predetermined voltage for a predetermined time or more. A detection circuit detects a battery voltage and a charging current, calculates a cancel voltage that cancels the voltage drop, and adds a calculated cancel voltage to the detected battery voltage to a voltage that is lower than the first voltage lower than the predetermined voltage. In the overvoltage detection device comprising a control circuit for detecting that the secondary battery is in a first overvoltage state when continuously high for 1 hour or more, the control circuit detects that the voltage of the battery voltage is A determination unit that determines whether or not the voltage is higher than a predetermined voltage; and a timer unit that counts time when the determination unit determines that the determination unit is high. Less than 2 hours If it is, wherein the secondary battery are adapted to detect that it is in the second over-voltage condition.

In the present invention, the detection circuit continuously determines that the detected voltage of the battery voltage including the voltage drop generated in the charging path of the secondary battery is higher than the predetermined voltage at which the predetermined overvoltage state is detected. When the time is equal to or longer than the second time shorter than the predetermined time until the predetermined overvoltage state is detected by the detection circuit, the control circuit detects the second overvoltage state of the secondary battery.
As a result, even when there is a high probability that a predetermined overvoltage state is detected after a predetermined time in the detection circuit because the voltage at the time of charging the secondary battery to which the voltage drop is added is higher than the predetermined voltage. Prior to the circuit detecting a predetermined overvoltage condition, the control circuit detects a second overvoltage condition.

  The overvoltage detection device according to the present invention detects that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including the voltage drop in the charging path is continuously higher than the predetermined voltage for a predetermined time or more. A detection circuit detects a battery voltage and a charging current, calculates a cancel voltage that cancels the voltage drop, and adds a calculated cancel voltage to the detected battery voltage to a voltage that is lower than the first voltage lower than the predetermined voltage. And a control circuit that detects that the secondary battery is in the first overvoltage state when the voltage is continuously high for one hour or more, wherein the control circuit has a magnitude of the cancellation voltage that is the predetermined voltage. And a determination unit that determines whether or not the difference is larger than a predetermined value that is smaller than the difference between the first voltages and a timing unit that counts time when it is determined that the determination unit is large, and the timing unit continuously counts time. Time If serial is shorter second time or more than the predetermined time, wherein the secondary battery are adapted to detect that it is in the second over-voltage condition.

In the present invention, the voltage drop generated in the charging path of the secondary battery is less than the predetermined value smaller than the difference between the predetermined voltage and the first voltage at which each of the detection circuit and the control circuit detects the overvoltage state of the secondary battery. When the time when it is continuously determined that the magnitude of the canceling voltage to be canceled is larger than the predetermined time until the predetermined overvoltage state is detected by the detection circuit is equal to or longer than the second time, the control circuit A second overvoltage condition of the battery is detected.
Thus, even if the first overvoltage state is difficult to be detected by the control circuit prior to the detection circuit because the magnitude of the voltage drop in the charging path is larger than the predetermined value, the detection circuit is in the predetermined overvoltage state. Prior to detecting, the control circuit detects a second overvoltage condition.

  The overvoltage detection device according to the present invention is characterized in that the first time is longer than the predetermined time.

In the present invention, the first time that is counted until the control circuit detects the first overvoltage state is longer than the predetermined time required until the detection circuit detects the predetermined overvoltage state.
As a result, a predetermined overvoltage state that has a higher possibility of degrading and damaging the secondary battery is quickly detected by the detection circuit.

  The protection device according to the present invention, when any of the above-described overvoltage detection device and the detection circuit and control circuit included in the overvoltage detection device detects that the secondary battery is in an overvoltage state, And a blocking unit that blocks the charging path.

In the present invention, when any of the detection circuit and the control circuit of the overvoltage detection device detects the overvoltage state of the secondary battery, the blocking unit blocks the charging path to the secondary battery.
As a result, the secondary battery connected to the protection device is prevented from being damaged such as deterioration or breakage due to falling into an overvoltage state during charging.

  In the protection device according to the present invention, the shut-off unit includes a non-return-type shut-off element and a switching element interposed in series with the charging path, and the non-return-type shut-off element includes the detection circuit. When the secondary battery is detected to be in an overvoltage state, the charging path is irreversibly interrupted, and the switching element detects that the control circuit is in an overvoltage state. In this case, it is characterized in that it is switched from on to off.

In the present invention, when the detection circuit of the overvoltage detection device detects the overvoltage state of the secondary battery, the non-return type interruption element irreversibly cuts off the charging path, and the control circuit of the secondary battery When an overvoltage state is detected, the switching element is switched from on to off.
As a result, when the charging current increases in a situation where the predetermined overvoltage state should not be detected by the detection circuit, the switching element is turned off before the charging path is interrupted by the non-return type interruption element.

  The battery pack according to the present invention includes the above-described protection device and a secondary battery protected from an overvoltage state by the protection device.

In the present invention, the protection device protects the secondary battery from the overvoltage state.
As a result, when the charging current of the secondary battery increases, the protection device that can prevent the detection circuit that detects an overvoltage higher than the overvoltage determined by software control from detecting the overvoltage state of the secondary battery first is packed. It can be applied to batteries.

According to the present invention, the number of times that the voltage at which the battery voltage including the voltage drop is detected is determined to be higher than the predetermined voltage, or the magnitude of the cancellation voltage is larger than the predetermined value that is smaller than the difference between the predetermined voltage and the first voltage. When the battery voltage is detected within the predetermined time is less than the number of times that the battery voltage is detected (or the time when the voltage at which the battery voltage including the voltage drop is detected is continuously determined to be higher than the predetermined voltage, or the predetermined voltage In addition, the overvoltage state of the secondary battery is detected while the time continuously determined that the magnitude of the cancellation voltage is larger than the predetermined value smaller than the difference between the first voltages is shorter than the predetermined time.
As a result, since the voltage at the time of charging the secondary battery to which the voltage drop is added is higher than the predetermined voltage, there is a high probability that an overvoltage is detected after a predetermined time in the detection circuit, or the voltage drop of the charging path Even if the first overvoltage state is difficult to detect in the control circuit prior to the detection circuit because the magnitude is larger than the predetermined value, the detection circuit detects the predetermined overvoltage state before the detection circuit. The control circuit detects a second overvoltage condition.
Therefore, when the charging current of the secondary battery increases, it becomes possible to prevent the detection circuit that detects an overvoltage higher than the overvoltage detected by software control from detecting the overvoltage state of the secondary battery first. .

It is a block diagram which shows the structural example of the battery pack which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the conditions from which CPU and the protection circuit which concern on Embodiment 1 of this invention detect an overvoltage state. It is a flowchart which shows the process sequence of CPU which detects an overvoltage state, when the cancellation | release battery voltage is higher than 4.2V (1st voltage). It is a flowchart which shows the process sequence of CPU which detects an overvoltage state, when a battery voltage is higher than 4.3V (predetermined voltage). It is a flowchart which shows the process sequence of CPU which act | operates a interruption | blocking part based on a 1st detection flag-a 3rd detection flag. It is explanatory drawing which shows the conditions which CPU and the protection circuit which concern on Embodiment 2 of this invention detect an overvoltage state. It is a flowchart which shows the process sequence of CPU which detects an overvoltage state, when the magnitude | size of cancellation voltage is higher than predetermined value. It is a block diagram which shows the structural example of the battery pack which concerns on a modification.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a battery pack according to Embodiment 1 of the present invention. In the figure, reference numeral 10 denotes a battery pack. The battery pack 10 detects the temperature of the secondary battery 1 in which battery cells 1a, 1b, and 1c made of lithium ion batteries are connected in series in this order, and the temperature of the secondary battery 1. The temperature sensor 2 is provided. The positive electrode terminal of the battery cell 1a and the negative electrode terminal of the battery cell 1c correspond to the positive electrode terminal and the negative electrode terminal of the secondary battery 1, respectively.

Resistors Ra1, Ra2, Rb1, Rb2, and Rc1, Rc2 corresponding to the resistances of the charge / discharge paths are equivalently connected in series to each of the battery cells 1a, 1b, and 1c.
The secondary battery 1 may be another battery such as a nickel metal hydride battery or a nickel cadmium battery. Moreover, the number of the battery cells which comprise the secondary battery 1 is not limited to 3, One, 2 or 4 or more may be sufficient.

  The positive electrode terminal of the secondary battery 1 is connected to the plus (+) terminal 91 via the blocking unit 3 that blocks the charge / discharge current of the secondary battery 1. A negative electrode terminal of the secondary battery 1 is connected to a minus (−) terminal 92 via a current detection resistor 4 for detecting a charge / discharge current of the secondary battery 1. The battery pack 10 is detachably attached to an electric device (not shown) such as a personal computer (PC) or a portable terminal via a plus (+) terminal 91 and a minus (−) terminal 92. . Further, a path from the plus (+) terminal 91 to the minus (−) terminal 92 via the blocking unit 3, the secondary battery 1, and the current detection resistor 4 corresponds to a charging / discharging path (hereinafter also referred to as a charging path). To do.

  The interruption unit 3 includes N-channel MOSFETs (switching elements) 35 and 36 for turning on and off the discharge current and the charge current of the secondary battery 1 and fuses 31 and 31 in series between two terminals. The non-return cutoff element 30 has a series circuit, and the series circuit is connected between the positive terminal and the positive (+) terminal 91 of the secondary battery 1. Instead of the MOSFETs 35 and 36, other switching elements such as transistors may be used. The gates of the MOSFETs 35 and 36 are each given an H (high) level on signal from the AFE 6 described later during normal charging and discharging. A parallel circuit of heating resistors 32 and 32 is interposed between the connection point of the fuses 31 and 31 and the other one terminal of the non-return cutoff element 30.

  The blocking unit 3 also includes an N-channel MOSFET 33 having a drain connected to the other terminal of the non-return blocking element 30 and an OR circuit 34 having an output terminal connected to the gate of the MOSFET 33. The source of the MOSFET 33 is connected to the negative terminal of the secondary battery 1. When the output terminal of the OR circuit 34 becomes H (high) level, the drain and the source of the MOSFET 33 are electrically connected, and the voltage and / or the external voltage of the secondary battery 1 is connected to the heating resistors 32 and 32 via the fuses 31 and 31. The fuses 31 and 31 are blown by applying a voltage from. Thereby, a charging / discharging path is interrupted | blocked irreversibly. The non-return cutoff element 30 that cuts off the charge / discharge path is not limited to the fuses 31 and 31.

  Both ends of each of the battery cells 1a, 1b, and 1c are connected to an input terminal of a protection circuit (detection circuit) 5 that detects an overvoltage state of each battery cell and supplies a detection signal to the OR circuit 34, and the battery cells 1a, 1b, and 1c. It is connected to an input terminal of an analog front end (Analogue Front End, hereinafter referred to as AFE) 6 that switches the voltage and gives it to the control unit 7 composed of a microcomputer. The other input terminal of the AFE 6 is connected to both ends of the current detection resistor 4. Here, the voltages of the battery cells 1a, 1b, and 1c applied to the protection circuit 5 and the AFE 6 include voltage drops that occur in the resistors Ra1, Ra2, Rb1, Rb2, and Rc1, Rc2. These resistance values are known, and for each of the resistors Ra1, Ra2, Rb1, Rb2 and Rc1, Rc2, an added value of the resistance value is stored in the ROM 71.

  The protection circuit 5 includes a comparator that compares the voltages of the battery cells 1a, 1b, and 1c and a reference voltage, and a timer (none of which are shown). The reference voltage is 4.3 V (predetermined voltage) in the present embodiment, but is not limited to this. Each of the comparators outputs a signal for starting a timer when the voltage of the battery cells 1a, 1b, and 1c including the voltage drop becomes higher than 4.3V. When, for example, 1.5 seconds have elapsed for each timer, an overvoltage state of the secondary battery 1 is detected, and an overvoltage state detection signal is given to one input terminal of the OR circuit 34. Thereby, the fuses 31 and 31 of the interruption | blocking part 3 are fuse | melted, and the charging / discharging path of the secondary battery 1 is interrupted | blocked.

  The AFE 6 has a comparator (not shown), and when an overcurrent of the secondary battery 1 is detected from a comparison result between the voltage across the current detection resistor 4 and the reference voltage, an L (low) level OFF signal is sent to the MOSFETs 35 and 36. To interrupt the charge / discharge current. The AFE 6 also gives an off signal to the MOSFETs 35 and 36 when an overvoltage detection signal is given from the I / O port 73.

  The control unit 7 includes a CPU 70. The CPU 70 stores a ROM 71 for storing information such as programs, a RAM 72 for storing temporarily generated information, an overvoltage state detection signal to the other input terminal of the OR circuit 34 and the AFE 6. The output I / O port 73, an A / D converter 74 that converts an analog voltage into a digital voltage, a timer 75 that measures time, and a communication unit 76 that communicates with an external electrical device are connected to each other by a bus. ing.

The A / D converter 74 is supplied with the voltage of each of the battery cells 1a, 1b, and 1c given from the AFE 6, the voltage given from the temperature sensor 2, and the voltage across the current detection resistor 4. The A / D converter 74 converts these analog voltages into digital voltages.
The communication unit 76 is connected to a serial data (SDA) terminal 93 for transmitting / receiving data to / from an external electric device and a serial clock (SCL) terminal 94 for receiving a clock.

  Among the configurations of the battery pack described above, the configuration excluding the secondary battery 1 and the temperature sensor 2 corresponds to the overvoltage protection device according to the present invention, and the configuration excluding the blocking unit 3 from the overvoltage protection device is the present invention. This corresponds to the overvoltage detection device according to. The control unit 7 and the AFE 6 correspond to a control circuit.

  The CPU 70 executes processing such as calculation and input / output in accordance with a control program stored in the ROM 71 in advance. For example, the CPU 70 takes in the voltage of the current detection resistor 4 in time series via the A / D converter 74 and integrates the charge / discharge current converted from the acquired voltage to integrate the remaining capacity of the secondary battery 1. In addition, the remaining capacity data is generated. The generated remaining capacity data is transmitted to an external electrical device via the communication unit 76. The CPU 70 further takes in the voltage of the temperature sensor 2 via the A / D converter 74 in a time series, for example, in a cycle of 250 milliseconds, and detects the battery temperature based on the taken-in voltage.

  The CPU 70 also detects the voltage of the battery cells 1a, 1b, and 1c given from the AFE 6 to the A / D converter 74 in a time series with a cycle of 250 milliseconds, and based on the highest voltage among the detected voltages, The overvoltage state of the secondary battery 1 is detected. The voltage detection period is not limited to 250 milliseconds. As described above, the detected voltage includes a voltage drop that occurs in the charge / discharge path.

  The CPU 70 calculates an offset voltage that cancels the voltage drop based on the charging current detected in time series by the current detection resistor 4 and the resistance value of the wiring of the charge / discharge path stored in the ROM 71. The net voltage of each of the battery cells 1a, 1b, and 1c (hereinafter, also referred to as the canceling battery voltage) can be estimated by adding the canceling voltage thus added to the voltage of each of the battery cells 1a, 1b, and 1c. In the present embodiment, the CPU 70 converts the voltage of each of the battery cells 1a, 1b, 1c including the voltage drop (hereinafter referred to as battery voltage) and the estimated net voltage of each of the battery cells 1a, 1b, 1c. Based on this, an overvoltage state of the secondary battery 1 is detected, and different detection flags are set according to the detected conditions.

  Next, the CPU 70 gives an overvoltage detection signal from the I / O port 73 to the OR circuit 34 or the AFE 6 according to the set detection flag. Thereby, when a detection signal is given to the OR circuit 34, the fuses 31, 31 of the interrupting unit 3 are blown and the charge / discharge path of the secondary battery 1 is interrupted. Further, when a detection signal is given to the AFE 6, an off signal is given to the MOSFETs 35 and 36, and the charge / discharge path of the secondary battery 1 is shut off. In this case, only the charging MOSFET 36 may be turned off to cut off the charging current to prevent overvoltage and overcharging.

  FIG. 2 is an explanatory diagram showing conditions under which the CPU 70 and the protection circuit 5 according to Embodiment 1 of the present invention detect an overvoltage state. In the figure, the horizontal axis represents overvoltage determination time (seconds) or the number of determinations, and the vertical axis represents battery voltage (V) or canceling battery voltage (V). Since the determination of the overvoltage by the CPU 70 is performed every 250 milliseconds, the determination times of 0.5 seconds, 1.5 seconds, and 5 seconds shown on the horizontal axis are the determination times of 2, 6, and 20, respectively. Correspondingly, 20 times and 2 times correspond to the first number and the second number, respectively. Also, 4.3 V and 4.2 V shown on the vertical axis respectively correspond to the predetermined voltage and the first voltage. However, the values of the first number, the second number, the predetermined voltage, and the first voltage are not limited to the values described above.

  In FIG. 2, areas to which the name of the flag and the name of the protection circuit 5 are attached are areas in which the CPU 70 and the protection circuit 5 detect the overvoltage state of the secondary battery 1, respectively. When the CPU 70 detects an overvoltage state, a flag with a name attached to the area is set. The region without a parenthesis (or with a parenthesis) is a region where an overvoltage state is detected based on the battery voltage (or canceling battery voltage). However, the regions marked with “(second detection flag)” and “(protection circuit)” in parentheses are overvoltage states when the battery voltage determined by the CPU 70 and the protection circuit 5 is converted into the canceling battery voltage. Is an example of a region in which these are detected, and these regions are indicated by diagonal lines that rise to the right and to the right.

  The protection circuit 5 detects the overvoltage state of the secondary battery 1 when the state where the battery voltage is higher than 4.3 V continues for 1.5 seconds or more as described above. For example, the added value of the resistance values of the resistors (for example, resistors Ra1 and Ra2) equivalently connected in series to each of the battery cells 1a, 1b, and 1c is 0.035 ohm, and a charging current of 2A flows. Assuming that the voltage drop across these resistors is 0.07V. Therefore, the protection circuit 5 equivalently detects an overvoltage state when a state where the canceling battery voltage is higher than 4.23 V (= 4.3 V−0.07 V) continues for 1.5 seconds or more.

  Needless to say, when the charging current is larger than 2 A, the lower limit of the region indicated by the oblique slanting line in FIG. 2 is lowered to a voltage lower than 4.23 V. As described above, as the charging current of the secondary battery 1 increases from 0, the region indicated by the slanting line with the lower right slope extends infinitely downward, so that a voltage lower than 4.2 V in terms of the canceling battery voltage is 5 It becomes easy to enter the area indicated by hatching within seconds. That is, the possibility that the overvoltage state of the secondary battery 1 is detected by the protection circuit 5 is increased before the CPU 70 sets the first detection flag.

In the first embodiment, the CPU 70 can detect the overvoltage state before the protection circuit 5 detects the overvoltage state of the secondary battery 1.
Below, the case where CPU70 detects an overvoltage state and sets a 1st detection flag-a 3rd detection flag is demonstrated using a flowchart. When the CPU 70 determines that the canceling battery voltage is higher than 4.2V for 20 times or more, the CPU 70 sets the first detection flag to detect the overvoltage state of the secondary battery 1 and passes through the I / O port 73. By supplying an overvoltage detection signal to the AFE 6, the MOSFETs 35 and 36 are turned off.

  FIG. 3 is a flowchart showing a processing procedure of the CPU 70 that detects an overvoltage state when the canceling battery voltage is higher than 4.2 V (first voltage). The process of FIG. 3 is activated at a cycle of 250 milliseconds, but is not limited to this. It is assumed that the charging current and the battery voltage in the figure are derived by being integrated and averaged by, for example, a process (not shown) executed by the CPU 70 with a period of 10 milliseconds (the same applies hereinafter).

  When the processing of FIG. 3 is activated, the CPU 70 determines the current obtained by inverting the sign of the charging current and the resistance of the charging path stored in the ROM 71 (resistance values of the resistors Ra1, Ra2, Rb1, Rb2 or Rc1, Rc2). Is calculated to obtain an offset voltage that cancels the voltage drop that occurs in the charging path (S10). Therefore, the cancellation voltage is calculated as a negative value. After that, the CPU 70 adds the canceling voltage to the battery voltage to obtain the canceling battery voltage (S11), and determines whether the calculated canceling battery voltage is 4.2V, that is, higher than the first voltage (S12).

  When the canceling battery voltage is not higher than 4.2 V (first voltage) (S12: NO), the CPU 70 clears the first determination number used as a counter to zero (S13), and further clears the first detection flag (S14). 3) The process of FIG. In this manner, the counter and flag used in the process of FIG. 3 are cleared while the canceling battery voltage is lower than 4.2V. When the canceling battery voltage is higher than 4.2 V (S12: YES), the CPU 70 determines whether or not the first detection flag is set to 1 (S15).

  When the first detection flag is set to 1 (S15: YES), the CPU 70 ends the process of FIG. 3 as it is. When the first detection flag is not set to 1 (S15: NO), the CPU 70 increments the first determination number by 1 (S16), and then the first determination number is 20 times or more, that is, the first number or more. It is determined whether or not (S17).

  When the first determination number is less than 20 (S17: NO), the CPU 70 shifts the processing to step S14 in order to ensure that the first detection flag is cleared. When the first determination number is 20 times or more (S17: YES), the CPU 70 clears the first determination number to zero (S18), and further performs the first detection to indicate that the overvoltage state of the secondary battery 1 is detected. The flag is set to 1 (S19), and the process of FIG.

  Returning to FIG. 2, when the CPU 70 determines that the canceling battery voltage is higher than 4.25 V continuously for 20 times or more, the CPU 70 detects the overvoltage state of the secondary battery 1 and sets the third detection flag. By supplying an overvoltage state detection signal to the OR circuit 34 via the O port 73, the fuses 31, 31 of the non-return cutoff element 30 are blown. The flowchart showing the processing procedure of the CPU 70 for detecting the overvoltage state when the canceling battery voltage is higher than 4.25V is set when the voltage determined in step S21 is different from the flowchart shown in FIG. Since only the flag and the name of the counter used during processing are different, and the other processing is the same, illustration and description thereof are omitted.

  By the way, since the third detection flag is set when the canceling battery voltage becomes higher than when the first detection flag is set, an overvoltage state in which the first detection flag is set is detected. As long as the MOSFETs 35 and 36 are reliably turned off, the third detection flag is not set. That is, the third detection flag is detected when the MOSFETs 35 and 36 cannot be turned off.

  Next, the second detection flag will be described. When the CPU 70 determines that the battery voltage is higher than 4.3 V (predetermined voltage) twice or more, the CPU 70 sets the second detection flag to detect the overvoltage state of the secondary battery 1, and the I / O port 73. By supplying an overvoltage state detection signal to the OR circuit 34 via the, the fuses 31, 31 of the non-return cutoff element 30 are blown. Here, the voltage used as a reference for the overvoltage determination by the CPU 70 is 4.3 V, which is the same as the reference voltage compared by the comparator of the protection circuit 5, and is shorter than 1.5 seconds, which is the overvoltage determination time by the protection circuit 5. The CPU 70 detects an overvoltage state with the number of determinations corresponding to 5 seconds. That is, the protection circuit 5 plays a role of fail-safe when the MOSFETs 35 and 36 are not normally turned off when the second detection flag is set.

FIG. 4 is a flowchart showing a processing procedure of the CPU 70 that detects an overvoltage state when the battery voltage is higher than 4.3 V (predetermined voltage). The process of FIG. 4 is started at a cycle of 250 milliseconds, but is not limited to this.
When the process of FIG. 4 is activated, the CPU 70 determines whether or not the battery voltage is 4.3V, that is, higher than a predetermined voltage (S21), and if not higher than 4.3V (S21: NO), The second determination number to be used is cleared to zero (S22), the second detection flag is further cleared (S23), and the process of FIG. 4 is terminated.

  When the battery voltage is higher than 4.3 V (S21: YES), the CPU 70 determines whether or not the second detection flag is set to 1 (S24). When the second detection flag is set to 1 (S24: YES), the CPU 70 ends the process of FIG. 3 as it is. When the second detection flag is not set to 1 (S24: NO), the CPU 70 increments the second determination number by 1 (S25), and then the second determination number is 2 times or more, that is, the second number or more. It is determined whether or not (S26).

  When less than twice (S26: NO), CPU70 transfers a process to step S23, in order to ensure the clearing of a 2nd detection flag. When the second determination number is two times or more (S26: YES), the CPU 70 clears the second determination number to zero (S27), and further performs the second detection to indicate that the overvoltage state of the secondary battery 1 is detected. The flag is set to 1 (S28), and the process of FIG. 4 is terminated.

Below, the process which interrupts | blocks a charging / discharging path according to whether the 1st detection flag-the 3rd detection flag are set is demonstrated.
FIG. 5 is a flowchart illustrating a processing procedure of the CPU 70 that operates the blocking unit 3 based on the first detection flag to the third detection flag. The process of FIG. 5 is started at a cycle of 250 milliseconds, but is not limited to this.

  When the process of FIG. 5 is activated, the CPU 70 determines whether or not the first detection flag is set to 1 (S31), and if it is set (S31: YES), the I / O port 73 and An off signal is given to the MOSFETs 35 and 36 via the AFE 6. As a result, the MOSFETs 35, 36, that is, the switching elements of the blocking unit 3 are turned off (S32). When the first detection flag is not set to 1 (S31: NO), the CPU 70 determines whether or not the second detection flag is set to 1 (S33).

  When the second detection flag is set to 1 (S33: YES), the CPU 70 shifts the processing to step S32 in order to turn off the switching element. When the second detection flag is not set to 1 (S33: NO), the CPU 70 turns on the switching element of the blocking unit 3 by giving an ON signal to the MOSFETs 35 and 36 via the I / O port 73 and the AFE 6. (S34). When the process of step S32 or S34 is completed, the CPU 70 determines whether or not the third detection flag is set to 1 (S35).

  When the third detection flag is not set to 1 (S35: NO), the CPU 70 ends the process of FIG. 5 as it is. When the third detection flag is set to 1 (S35: YES), the CPU 70 gives an H (high) level signal to the OR circuit 34 via the I / O port 73 and ends the processing of FIG. . As a result, the MOSFET 33 is turned on, and the fuses 31 and 31 of the non-return cutoff element 30 are blown (S36).

As described above, according to the first embodiment, the battery voltage including the voltage drop generated in the charging path of the secondary battery is set every 250 msec, rather than the predetermined voltage (4.3 V) at which the protection circuit detects the overvoltage state. The number of times that the detected voltage is continuously determined to be higher is equal to or more than the second number (2 times), which is less than the number of times the battery voltage is detected in 1.5 seconds until the overvoltage state is detected by the protection circuit. In some cases, the CPU detects an overvoltage state of the secondary battery.
As a result, even when there is a high probability that an overvoltage state is detected after 1.5 seconds in the protection circuit because the voltage at the time of charging the secondary battery to which the voltage drop is added is higher than the predetermined voltage. Prior to the circuit detecting an overvoltage condition, the CPU is used to detect the overvoltage condition.
Therefore, when the charging current of the secondary battery increases, it becomes possible to prevent the protection circuit that detects an overvoltage higher than the overvoltage detected by software control from detecting the overvoltage state of the secondary battery first. .

Further, the first number (20 times) counted until the CPU detects the overvoltage state is greater than the number of times (6 times) the battery voltage is detected in 1.5 seconds required for the protection circuit to detect the overvoltage state. There are so many.
As a result, an overvoltage state that has a higher possibility of degrading and damaging the secondary battery can be quickly detected by the protection circuit.

Furthermore, when any one of the protection circuit of the overvoltage detection device and the CPU detects an overvoltage state of the secondary battery, the blocking unit blocks the charging path to the secondary battery.
As a result, the secondary battery connected to the protection device can be prevented from being damaged such as deterioration or breakage due to falling into an overvoltage state during charging.

Furthermore, when the protection circuit of the overvoltage detection device detects an overvoltage state, the fuse of the non-recovery interruption element irreversibly interrupts the charging path, and when the CPU detects an overvoltage state, the switching element (MOSFET) Switch from on to off.
This allows the switching element to be turned off before the charging path is interrupted by the non-recoverable interrupting element if the charging current increases under circumstances where an overvoltage condition should not be detected by the protection circuit It becomes.

Furthermore, the protection device protects the secondary battery from an overvoltage condition.
Thus, when the charging current of the secondary battery increases, the protection device that can prevent the protection circuit that detects an overvoltage higher than the overvoltage determined by software control from detecting the overvoltage state of the secondary battery first is packed. It becomes possible to apply to a battery.

(Embodiment 2)
In the first embodiment, when the overvoltage state of the secondary battery 1 is detected based on the battery voltage, the CPU 70 detects the overvoltage state and sets the second detection flag before the protection circuit 5 detects the overvoltage state. It is a form to do. On the other hand, in the second embodiment, the magnitude of the cancellation voltage cannot be ignored with respect to the difference between the predetermined voltage that the protection circuit 5 compares with the battery voltage and the first voltage that the CPU 70 determines to compare with the cancellation battery voltage. This is a mode in which the CPU 70 sets the second detection flag prior to the protection circuit 5 when the charging current increases.

  FIG. 6 is an explanatory diagram showing conditions under which the CPU 70 and the protection circuit 5 according to Embodiment 2 of the present invention detect an overvoltage state. In the figure, the horizontal axis represents overvoltage determination time (seconds) or the number of determinations, and the vertical axis represents battery voltage (V) or canceling battery voltage (V). When the judgment time is longer than 5 seconds and the canceling battery voltage is higher than 4.23 V, the area where the name of the flag and the name of the protection circuit 5 are attached and the name without parentheses (or with parentheses) are written. The meaning of the region indicated by the region and the region indicated by the diagonally slanting line to the right is the same as in the case of FIG.

  When the canceling battery voltage is higher than 4.23 V, unlike the example shown in FIG. 2, the second detection flag is set even if the protection circuit 5 detects the overvoltage state of the secondary battery 1. There is nothing to do. Therefore, when a voltage lower than 4.2V in terms of the canceling battery voltage rises to 4.23V or more within 5 seconds and enters the region indicated by the slanting line of the lower right, the CPU 70 causes the first detection flag. Prior to being set, the protection circuit 5 detects the overvoltage state of the secondary battery 1.

  Therefore, in the second embodiment, the lower limit voltage at which the charging current is larger than 2A and the overvoltage state of the secondary battery 1 is detected by the protection circuit 5 is less than 4.23 V in terms of the canceling battery voltage. In such a case (for example, when the region in which the protection circuit 5 detects the overvoltage state has expanded to the region indicated by the diagonally upward slanting line in FIG. 6), the CPU 70 before the protection circuit 5 detects the overvoltage state. Allows the second detection flag to be set. In other words, the magnitude of the canceling voltage that cancels the voltage drop due to the wiring is 0.07V (= 4.3V−4.23V), which is smaller than the difference between the predetermined voltage (4.3V) and the first voltage (4.2V). ), The CPU 70 detects the overvoltage state of the secondary battery 1 prior to the protection circuit 5.

  Specifically, the number of times that the magnitude of the cancellation voltage is continuously determined to be greater than 0.07 V is two times corresponding to 0.5 seconds, which is shorter than 1.5 seconds, which is the overvoltage determination time by the protection circuit 5. When this is the case, the second detection flag is set. In FIG. 6, the region where the second detection flag is set is indicated by a slanting line with a right lowering. However, the region in which the CPU 70 sets the second detection flag is drawn in contrast to the region in which the protection circuit 5 detects the overvoltage state of the secondary battery 1, and the second detection flag itself has an offset voltage. This is set when a charging current such that the magnitude of is greater than 0.07 V flows for 0.5 seconds or more. Thereby, the MOSFETs 35 and 36 are temporarily turned off as a kind of overcurrent protection.

  The boundary value of 4.23 V described above is not limited to this, and can be set as appropriate within the range of the predetermined voltage (4.3 V) and the first voltage (4.2 V). When this boundary value is set to 4.2 V or less, it is always within the range in which the second detection flag is not set, for example, when the charging current becomes 0.286 A (= 0.1 V / 0.035 ohm) or more. An area where the protection circuit 5 detects an overvoltage state exists before the CPU 70.

FIG. 7 is a flowchart showing a processing procedure of the CPU 70 that detects an overvoltage state when the magnitude of the cancellation voltage is higher than a predetermined value. The process of FIG. 3 is activated at a cycle of 250 milliseconds, but is not limited to this.
When the process of FIG. 7 is activated, the CPU 70 calculates the product of the current obtained by inverting the sign of the charging current and the resistance of the charging path stored in the ROM 71, and cancels the voltage drop that occurs in the charging path. Is calculated (S40). Thereafter, the CPU 70 determines whether or not the magnitude of the cancellation voltage, that is, the absolute value of the cancellation voltage is greater than 0.07 V (S41).

If the absolute value of the cancellation voltage is not greater than 0.07V (S41: NO), the process proceeds to step S42, and if greater than 0.07V (S41: YES), the process proceeds to step S44. Here, the processing of steps S42 to S48 is exactly the same as the processing of steps S22 to S28 shown in FIG.
In addition, the same code | symbol is attached | subjected to the location corresponding to Embodiment 1, and the detailed description is abbreviate | omitted.

As described above, according to the second embodiment, the protection circuit and the CPU each detect the difference between the predetermined voltage (4.3V) and the first voltage (4.2V) that detect the overvoltage state of the secondary battery (0.2V). The overvoltage state is detected by the protection circuit the number of times that it is continuously determined that the magnitude of the canceling voltage that cancels the voltage drop that occurs in the charging path of the secondary battery is larger than 0.07V, which is smaller than 1V). If it is equal to or more than the second number (two times) that is less than the number of times the battery voltage is detected for 1.5 seconds, the overvoltage state of the secondary battery is detected.
As a result, since the magnitude of the voltage drop in the charging path is larger than the predetermined value, the protection circuit detects the overvoltage state even when it is difficult for the CPU to detect the overvoltage state prior to the protection circuit. Prior to this, the CPU can detect the overvoltage state.

  In the first and second embodiments, the case where the canceling battery voltage and the battery voltage are both higher than the predetermined voltage and the case where the magnitude of the canceling voltage is larger than the predetermined value continue for a predetermined number of times of determination. In this case, the predetermined detection flag may be set when each of the above cases continues for a time corresponding to the number of determinations. Specifically, for example, in steps S25 and S26 shown in the flowchart of FIG. 4, if the result of incrementing the second determination count becomes equal to or greater than the second count, it is determined that the determination has continued for a predetermined time or more. Set.

  In the first and second embodiments, among the configurations realized by the hardware of the control circuit and the software executed by the CPU 70, steps S21 and S41 shown in FIGS. 4 and 7 correspond to the software of the determination unit. S25 and S45 correspond to the software of the counting unit or the time measuring unit.

  Furthermore, in the first and second embodiments, the resistors Ra1, Ra2, Rb1, Rb2, and Rc1, Rc2 corresponding to the resistance due to the wiring of the charge / discharge path are equivalent to the battery cells 1a, 1b, and 1c, respectively. However, when the protection circuit 5 and the AFE 6 and the battery cells 1a, 1b, and 1c can be connected so as not to be affected by the voltage drop due to these resistors, the protection circuit 5 However, there is no possibility that the overvoltage state of the secondary battery 1 is detected before the CPU 70.

  For example, FIG. 8 is a block diagram illustrating a configuration example of a battery pack according to a modification. In FIG. 8, since the resistance values of the resistors Ra2, Rb1, Rb2, and Rc1 can be ignored as compared with the resistance values of the resistors Ra1 and Rc2, the illustration is omitted. The input terminals of the protection circuit 5 and the AFE 6 are directly connected to the battery cells 1a, 1b, and 1c. Other circuits are the same as those in FIG. In the battery pack shown in FIG. 8, the voltage of the battery cells 1a, 1b, and 1c detected by the protection circuit 5 and the CPU 70 does not include a voltage drop that occurs in the charging path due to the charging current. The voltage becomes equal to the battery voltage. Therefore, the region in which the protection circuit 5 detects the overvoltage state of the secondary battery 1 in FIG. 2 does not extend to the region indicated by the slanted line in FIG. The charging current is not affected by the magnitude.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10 pack battery 1 secondary battery 1a, 1b, 1c battery cell 3 shut-off part 30 non-recovery shut-off element (non-return-type shut-off element)
35, 36 MOSFET (switching element)
4 Current detection resistor 5 Protection circuit (detection circuit)
6 AFE
7 Control unit 70 CPU

Claims (9)

A detection circuit for detecting that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including a voltage drop in the charging path is continuously higher than a predetermined voltage for a predetermined time, the battery voltage and the charging A cancel voltage that cancels the voltage drop is calculated by detecting current in time series, and a voltage obtained by adding the calculated cancel voltage to the detected battery voltage continues for a first time or more from the first voltage lower than the predetermined voltage. An overvoltage detection device comprising a control circuit for detecting that the secondary battery is in a first overvoltage state,
The control circuit includes:
A determination unit that determines whether or not a voltage obtained by detecting the battery voltage in time series is higher than the predetermined voltage;
A counting unit that counts the number of times that the determination unit is determined to be high,
When the number of times the counting unit continuously counts is equal to or more than a second number less than the number of times the battery voltage is detected within the predetermined time, it is detected that the secondary battery is in the second overvoltage state. An overvoltage detection device, characterized in that A detection circuit for detecting that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including a voltage drop in the charging path is continuously higher than a predetermined voltage for a predetermined time, the battery voltage and the charging A cancel voltage that cancels the voltage drop is calculated by detecting current in time series, and a voltage obtained by adding the calculated cancel voltage to the detected battery voltage continues for a first time or more from the first voltage lower than the predetermined voltage. An overvoltage detection device comprising a control circuit for detecting that the secondary battery is in a first overvoltage state,
The control circuit includes:
A determination unit that determines whether the magnitude of the cancellation voltage is greater than a predetermined value that is smaller than a difference between the predetermined voltage and the first voltage;
A counting unit that counts the number of times that the determination unit is determined to be large,
When the number of times the counting unit continuously counts is equal to or more than a second number less than the number of times the battery voltage is detected within the predetermined time, it is detected that the secondary battery is in the second overvoltage state. An overvoltage detection device, characterized in that   3. The overvoltage detection device according to claim 1, wherein the first number of times is greater than the number of times the battery voltage is detected within the predetermined time. A detection circuit for detecting that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including a voltage drop in the charging path is continuously higher than a predetermined voltage for a predetermined time, the battery voltage and the charging When a voltage obtained by detecting a current and canceling the voltage drop is calculated, and a voltage obtained by adding the calculated cancel voltage to the detected battery voltage is continuously higher than a first voltage lower than the predetermined voltage for a first time or more, An overvoltage detection device comprising a control circuit for detecting that the secondary battery is in a first overvoltage state;
The control circuit includes:
A determination unit that determines whether or not a voltage at which the battery voltage is detected is higher than the predetermined voltage;
If it is determined that the determination unit is high, it has a timing unit for measuring time,
When the time continuously measured by the time measuring unit is equal to or longer than a second time shorter than the predetermined time, it is detected that the secondary battery is in a second overvoltage state. Overvoltage detection device. A detection circuit for detecting that the secondary battery is in a predetermined overvoltage state when the battery voltage of the secondary battery including a voltage drop in the charging path is continuously higher than a predetermined voltage for a predetermined time, the battery voltage and the charging When a voltage obtained by detecting a current and canceling the voltage drop is calculated, and a voltage obtained by adding the calculated cancel voltage to the detected battery voltage is continuously higher than a first voltage lower than the predetermined voltage for a first time or more, An overvoltage detection device comprising a control circuit for detecting that the secondary battery is in a first overvoltage state;
The control circuit includes:
A determination unit that determines whether the magnitude of the cancellation voltage is greater than a predetermined value that is smaller than a difference between the predetermined voltage and the first voltage;
If it is determined that the determination unit is large, it has a timing unit for measuring time,
When the time continuously measured by the time measuring unit is equal to or longer than a second time shorter than the predetermined time, it is detected that the secondary battery is in a second overvoltage state. Overvoltage detection device.   The overvoltage detection device according to claim 4, wherein the first time is longer than the predetermined time. The overvoltage detection device according to any one of claims 1 to 6,
When any one of the detection circuit and the control circuit included in the overvoltage detection device detects that the secondary battery is in an overvoltage state, it includes a blocking unit that blocks a charging path of the secondary battery. Protection device. The blocking unit includes a non-return type blocking element and a switching element interposed in series in the charging path,
When the detection circuit detects that the secondary battery is in an overvoltage state, the non-return-type interruption element irreversibly cuts off the charging path,
The protection device according to claim 7, wherein the switching element is configured to switch from on to off when the control circuit detects that the secondary battery is in an overvoltage state.   A battery pack comprising the protection device according to claim 7 and a secondary battery protected from an overvoltage state by the protection device.

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