JP5110168B2 - Battery protection device and battery pack incorporating the same - Google Patents

Description

  The present invention provides a battery protection device comprising: switching means for switching conduction / cutoff of a charge / discharge path between an input / output terminal and a bipolar electrode of a secondary battery; and control means for controlling a switching operation of the switching means; The present invention relates to a battery pack incorporating the same.

  Conventionally, a battery in which a first FET and a second FET are connected in series to a charge / discharge circuit that connects between a positive electrode and a negative electrode of a secondary battery and a positive electrode and a negative electrode of an input / output terminal between the same electrodes. A protection device is known (see, for example, Patent Document 1). FIG. 3 is a configuration diagram of the battery protection device described in FIG. FIG. 4 is a flowchart described in FIG. This battery protection device detects a terminal voltage E2 between the positive electrode 71 and the negative electrode 72 of the input / output terminal when the battery voltage E1 between the positive electrode and the negative electrode of the secondary battery 65 is equal to or higher than the charge prohibition voltage (S2, Yes). (S5) When a charging state in which the terminal voltage E2 is higher than the battery voltage E1 is detected (S6, No), the first and second FETs 66 and 67 are controlled to be turned off (S7). However, when a discharge state in which the terminal voltage E2 is lower than the battery voltage E1 is detected (S6, Yes), the first and second FETs 66 and 67 are controlled to be turned on (S4). (See paragraph [0019] of Patent Document 1 and flowchart of FIG. 5). By controlling in this way, it is possible to prevent a discharge current from flowing through the parasitic diode 66a of the first FET 66 even when discharging is performed in a state where charging prohibition is controlled. Deterioration due to the generation of heat due to the flow of discharge current is prevented.

JP 2001-57740 A

  However, according to FIG. 5 of Patent Document 1 (FIG. 4 of the present application), when the battery voltage E1 is equal to or higher than the charge prohibition voltage (S2, Yes), a discharge state in which the terminal voltage E2 is lower than the battery voltage E1 is detected. (S6, Yes) After the first and second FETs 66 and 67 are turned on (S4), unless the terminal voltage E2 is detected to be higher than the battery voltage E1 (S6), The second FETs 66 and 67 are controlled not to be turned off (S7) but to be kept on (S4).

  However, even if the terminal voltage E2 is detected in a state where the first and second FETs 66 and 67 are on (S5), as long as the first and second FETs 66 and 67 are on, the terminal voltage E2 and Since the battery voltage E1 is substantially the same voltage, it is not easy to detect a charging state in which the terminal voltage E2 is higher than the battery voltage E1 (that is, detect a difference between the terminal voltage E2 and the battery voltage E1) in S6. . Therefore, in spite of the situation where the battery voltage E1 is equal to or higher than the charging prohibition voltage (S2, Yes), the first and second FETs 66 and 67 are turned off by detecting a charging state in which the terminal voltage E2 is higher than the battery voltage E1. It is very difficult to prohibit charging of the secondary battery 65 by setting (S7).

  Therefore, the present invention prevents the secondary battery from continuing to be charged while suppressing the reduction of the terminal voltage even if the terminal voltage is lowered while the charging prohibition condition for the secondary battery is satisfied. An object of the present invention is to provide a battery protection device and a battery pack.

In order to achieve the above object, a battery protection device according to the present invention comprises:
Switching means for switching conduction / interruption of a charging / discharging path between the input / output terminal for discharging from the secondary battery to the electronic device and charging from the charging device to the secondary battery and the bipolar terminal of the secondary battery; ,
Control means for controlling the switching operation of the switching means,
The control means detects the decrease in the terminal voltage of the input / output terminal in a state where the charge / discharge path is blocked by the switching means due to the charging prohibition condition of the secondary battery being satisfied. The switching means is provided with a conduction time for temporarily turning on the charging / discharging path, and the switching means returns the charging / discharging path to a cut-off state when the conduction time elapses.

  Here, it is preferable that the conduction time is set to a time synchronized with a change in the operation mode of the electronic device. For example, the electronic device is a portable device having a wireless communication function. When the electronic device is a portable device having a wireless communication function, it is preferable that the conduction time is set to a time synchronized with a radio wave transmission / reception operation of the portable device.

  In order to achieve the above object, a battery pack according to the present invention incorporates the battery protection device and the secondary battery.

  According to the present invention, even if the terminal voltage is lowered while the charging prohibition condition for the secondary battery is satisfied, the charging state of the secondary battery is prevented from continuing while suppressing the reduction of the terminal voltage. Can do.

1 is an overall configuration diagram of a battery pack 100 according to an embodiment of the present invention. FIG. 4 is a diagram showing a relationship between an on time of switching element 1 and a charge / discharge current of secondary battery 200. FIG. 5 is a configuration diagram of a battery protection device described in FIG. 4 of Patent Document 1. 6 is a flowchart described in FIG.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a battery pack 100 according to an embodiment of the present invention. The battery pack 100 is an input / output for discharging to a portable device 300 powered by a secondary battery 200 such as a lithium ion battery, a nickel hydride battery, or an electric double layer capacitor, and charging the secondary battery 200 by the charger 400. Switching elements 1 and 2 for switching conduction / interruption of charge / discharge path 9 (9a, 9b) between terminals 5 and 6 and bipolar terminals 3 and 4 of secondary battery 200, and switching operation of switching elements 1 and 2 This is a module component that incorporates a battery protection device including a battery protection IC 90 to be controlled together with the secondary battery 200.

  The battery pack 100 is built in or externally attached to the mobile device 300. The mobile device 300 is an electronic device that can be carried by a person, and a device having a wireless communication function such as a mobile phone is a specific example. Other specific examples include information terminal devices such as PDAs and mobile personal computers, cameras, game machines, and players such as music and video.

  Switching elements 1 and 2 are connected in series so that switching between conduction / cutoff of charge / discharge path 9b between negative electrode 4 and negative electrode input / output terminal 6 of secondary battery 200 is possible. The switching element 1 is a first switching unit that can switch between interruption / conduction of the charging current of the secondary battery 200 that flows in the charging direction through the charging / discharging path 9, and the switching element 2 moves the charging / discharging path 9 in the discharging direction. It is the 2nd switching means which can switch interruption | blocking / conduction of the discharge current of the flowing secondary battery 200. FIG. Charging of the secondary battery 20 is permitted when the switching element 1 is on, and charging of the secondary battery 200 is prohibited when the switching element 1 is off. Further, discharging of the secondary battery 200 is permitted when the switching element 2 is in the on state, and discharging of the secondary battery 200 is prohibited in the off state.

  The switching elements 1 and 2 are semiconductor elements, such as MOSFET and IGBT which have a parasitic diode, for example. The switching element 1 is arranged between the negative electrode 4 and the negative input / output terminal 6 in such a direction that the forward direction of the parasitic diode 1a becomes the discharge direction of the secondary battery 200, and the switching element 2 is arranged in the order of the parasitic diode 2a. It is arranged between the negative electrode 4 and the negative electrode input / output terminal 6 so that the direction is the charging direction of the secondary battery 200. The switching elements 1 and 2 may be bipolar transistors, and diodes may be formed between the collector and emitter in the illustrated direction.

  The battery protection IC 90 includes a temperature detection unit 10 that detects the temperature of the secondary battery 200, a voltage detection unit 21 such as an overcharge detection unit that detects overcharge of the secondary battery 200, and overdischarge of the secondary battery 200. Overdischarge detection unit 22 to detect, current detection unit to detect charge / discharge current of secondary battery 200 (for example, overcurrent detection unit 31 to detect overcurrent during charging, and overcurrent to detect overcurrent during discharge) And a control unit 50 that controls on / off of the switching elements 1 and 2 based on a signal indicating a detection result from each of the detection units. Each detection unit may be configured by, for example, a comparator or an AD converter. The control unit 50 may be configured by, for example, a logic circuit or a microcomputer.

  The temperature detection unit 10 detects the voltage at the connection point between the thermistor 11 and the resistance element 12 connected in series between the positive charge / discharge path 9a and the negative charge / discharge path 9b via the terminal VTH1. Accordingly, the temperature of the secondary battery 200 is detected, and a detection signal corresponding to the detected temperature is output to the control unit 50.

  The voltage detector 21 is connected to the VDD terminal connected to the positive charge / discharge path 9a and the V-terminal connected to the path between the negative input / output terminal 6 and the switching element 1 among the charge / discharge paths 9b. Then, the terminal voltage between the positive input / output terminal 5 and the negative input / output terminal 6 is detected, and a detection signal corresponding to the detected terminal voltage is output to the control unit 50.

  The control unit 50 turns off the switching element 1 when the charging prohibition condition for the secondary battery 200 is satisfied. Thereby, it can prevent that the charging current which charges the secondary battery 200 flows irrespective of the on-off state of the switching element 2. FIG. When the discharge prohibition condition for the secondary battery 200 is satisfied, the switching element 2 is turned off. Thereby, it is possible to prevent the discharge current of the secondary battery 200 from flowing regardless of the on / off state of the switching element 1.

  The charging prohibition condition of the secondary battery 200 is determined based on, for example, the temperature of the secondary battery 200, the charging voltage and charging current supplied to the secondary battery 200, the cumulative usage time of the secondary battery 200, and the like. .

  For example, when the temperature of the secondary battery 200 detected by the temperature detection unit 10 is within a temperature range (for example, a predetermined high temperature region or low temperature region) in which charging of the secondary battery 200 is prohibited, the control unit 50 In other words, when the temperature condition prohibiting charging of the secondary battery 200 is established, the switching element 1 is turned off, and when it is outside the temperature range (when the temperature condition is not established). ), The switching element 1 is turned on. For example, the control unit 50 outputs a signal for turning off the switching element 1 when a signal indicating that the temperature of the secondary battery 200 is within a temperature range in which charging of the secondary battery 200 is prohibited is input. And a circuit that outputs a signal that turns on the switching element 1 when a signal indicating that the temperature is out of the temperature range is input. Thereby, the progress of deterioration of the secondary battery 200 due to charging in a specific temperature region can be delayed.

  Further, for example, the control unit 50 uses the charging voltage for charging the secondary battery 200 detected by the voltage detection unit 21 (that is, the voltage between the input and output terminals 5 and 6) to charge the secondary battery 200. Is within a voltage range (for example, a predetermined high voltage region) that prohibits charging (that is, when a voltage condition that prohibits charging of the secondary battery 200 is satisfied), the switching element 1 is turned off. When the voltage is outside the voltage range (when the voltage condition is not satisfied), the switching element 1 is turned on. Thereby, the progress of deterioration of the secondary battery 200 due to charging in a specific voltage region can be delayed.

  The same applies to the case where on / off of the switching element 2 is controlled in accordance with the discharge prohibition condition of the secondary battery 200.

  By the way, in the state where the switching element 2 is turned on and the switching element 1 is turned off because the charging prohibition condition of the secondary battery 200 is satisfied, both the portable device 300 and the charger 400 are connected. There are cases where the input / output terminals 5 and 6 are electrically connected. For example, it is a case where the portable device 300 is operating while being connected to the charger 400 in an environment where the charging prohibition condition is satisfied. In this case, the charging current from the charger 400 does not flow through the secondary battery 200 but flows through the portable device 300.

  However, when the consumption current (load current) of the mobile device 300 exceeds the charging current supplied from the charger 400, the voltage between the input / output terminals 5 and 6 decreases. In this case, the inter-terminal voltage is such that the discharge current flowing from the secondary battery 200 to the portable device 300 passes through the parasitic diode 1a, so that at least the forward voltage of the parasitic diode 1a is equal to the bipolar terminals 3 of the secondary battery 200. 4 is lower than the voltage between both electrodes. When the inter-terminal voltage decreases in this way, for example, the mobile device 300 may determine that the battery pack 100 is abnormal by detecting a decrease in the inter-terminal voltage. In addition, heat is generated when a current flows through the parasitic diode 1a.

  Therefore, in order to prevent these problems, the control unit 50 reduces the voltage between the terminals while the charging / discharging path 9 is shut off by turning off the switching element 1 when the charging prohibition condition of the secondary battery 200 is satisfied. When the detection signal shown is input from the voltage detection unit 21, the switching element 1 is switched from OFF to ON while the switching element 2 is ON, thereby bringing the charge / discharge path 9 into a conductive state. The voltage detection unit 21 detects, for example, a decrease in the voltage between the terminals when the actually detected voltage between the terminals is lower than a voltage value obtained by subtracting the forward voltage of the parasitic diode 1a from the voltage between the terminals in a steady state. A signal may be output to the control unit 50. In order to increase the detection sensitivity of the voltage drop between the terminals, the terminal voltage is detected when the actually detected voltage between the terminals is lower than the voltage value obtained by subtracting the voltage smaller than the forward voltage of the parasitic diode 1a from the voltage between the terminals in the steady state. A detection signal indicating a decrease in the inter-voltage may be output to the control unit 50.

  In this way, by switching the switching element 1 from OFF to ON while the switching element 2 is ON, the charging / discharging path 9 is turned on, so that the secondary battery 200 can be removed from the secondary battery 200 without passing through the parasitic diode 1a. Can be supplied from the secondary battery 200 to the portable device 300, which cannot be supplemented only from the charger 400, while preventing a decrease in the voltage between the terminals, and at the parasitic diode 1a. Heat generation due to voltage drop can be prevented.

  However, when the load current of the portable device 300 decreases even when the charging / discharging path 9 is made conductive in the discharge direction by turning on the switching element 1 in this way, power is supplied to the portable device 300 only from the charger 400. As a result, the charging current from the charger 400 becomes excessive. As a result, the excess current becomes a charging current for charging the secondary battery 200. Therefore, although the charging prohibition condition of the secondary battery 200 is established, the switching element 1 is turned on, so that the voltage drop between terminals can be suppressed and the heat generation in the parasitic diode 1a can be prevented. However, the secondary battery 200 is charged.

  In order to prevent this, the switching element 1 that has been turned on may be turned off again. However, even if the switching element 1 is turned on and the voltage detection unit 21 detects the voltage between the terminals, Since the voltage difference between the electrodes of the secondary battery 200 and the voltage between terminals of the secondary battery 200 hardly occurs as long as it is turned on, the recovery from the decrease in the voltage between terminals due to the decrease in the load current of the portable device 300 is performed between the terminals. It is very difficult to recognize by detecting the voltage.

  Therefore, the control unit 50 detects that the detection signal indicating a decrease in the voltage between the terminals is in a state where the charging / discharging path 9 is shut off by turning off the switching element 1 when the charging prohibition condition of the secondary battery 200 is satisfied. 21 is provided with a conduction time for temporarily switching the charging / discharging path 9 by switching the switching element 1 from off to on while the switching element 2 is turned on. Control which returns charging / discharging path | route 9 to the interruption | blocking state by switching 1 from ON to OFF is performed. In this way, the timing of switching element 1 from on to off (in other words, switching timing from the conduction state to the cutoff state of charging / discharging path 9) is managed by the time from the switching element 1 on, so that the terminal Even if the recovery from the voltage drop cannot be recognized by voltage detection, the switching element 1 can be returned from on to off at an appropriate timing.

  Therefore, the control unit 50 includes a timer 51 as time management means in order to manage temporary conduction time. The timer 51 is configured to generate a trigger signal when a predetermined time has elapsed since the switching element 1 is turned on. The control unit 50 turns on the switching element 1 when a detection signal indicating a decrease in the voltage between the terminals is input from the voltage detection unit 21 when the charging prohibition condition of the secondary battery 200 is satisfied, When the trigger signal shown is generated by the timer 51, a signal for returning the switching element 1 from ON to OFF is output.

  The temporary ON time of the switching element 1 (that is, the temporary conduction time of the charging / discharging path 9) may be set to a time synchronized with a change in the operation mode of the mobile device 300. Since the load current changes according to the operation mode of the mobile device 300, the secondary battery 200 is prevented from being charged / discharged more than necessary by synchronizing the on-time of the switching element 1 with the change in the operation mode. Can do.

  For example, the load current of the mobile device 300 changes depending on the operation mode. The mobile device 300 may operate in a high power consumption mode in which power consumption is higher than that in the normal operation mode. The portable device 300 shifts from the normal operation mode to the high power consumption mode when the transition condition for the high power consumption mode is satisfied in the normal operation mode. The portable device 300 shifts from the high power consumption mode to the normal power consumption mode when the condition for shifting to the normal operation mode is satisfied in the high power consumption mode. If the mobile device 300 is a mobile phone, when the deterioration of the radio wave environment is detected by a decrease in radio wave reception level, etc., the mobile device 300 shifts to a high power consumption mode in which radio waves are transmitted with a transmission power higher than the normal transmission power, and the transmission / reception operation is performed. repeat. Therefore, since the length of the transmission time for transmitting radio waves with a transmission power larger than normal is determined in advance, by setting the length of the on-time of the switching element 1 to the time synchronized with the transmission time, The switching element 1 temporarily turned on at an appropriate timing can be returned to the off state. The ON time of the switching element 1 may be set to a length longer than the transmission time.

  FIG. 2 is a diagram showing the relationship between the on-time of the switching element 1 and the charge / discharge current of the secondary battery 200. FIG. 2 shows a situation where a mobile phone connected to the charger is transmitting / receiving in an environment where the charging prohibition condition is satisfied. Therefore, in this situation, the mobile phone operates by repeating the reception period and the transmission period in which transmission is performed with transmission power larger than normal.

  Ttr is a radio wave transmission period of the mobile phone, Itr is a load current during the mobile phone transmission period Ttr, Trv is a radio wave reception period of the mobile phone, and Irv is a load during the mobile phone reception period Trv. Ich is a charging current supplied by the charger 400, and T is an ON time of the switching element 1 when a decrease in the voltage between the terminals is detected when the charging prohibition condition is satisfied.

The amount of charge Qch flowing into the secondary battery 200 is
Qch = (Ich−Irv) × (T−Ttr) + (Ich−Itr) × Ttr
... (1)
Can be expressed as

The average current value I flowing into the secondary battery 200 is
I = {(Ich−Irv) × (T−Ttr) + (Ich−Itr) × Ttr}
/ (Ttr + Trv) (2)
Can be expressed as

  Therefore, in the case of Itr> Ich, if T = Ttr, the battery inflow current I in one cycle including the radio wave transmission period and the reception period is negative, and the secondary battery 200 is discharged. Show.

  Since the voltage between the terminals decreases when Itr> Ich, the count Cout of the timer 51 becomes 1 at the timing when the decrease is detected and is held for a certain time T. Since the load current Itr during the transmission period of the mobile phone is larger than the load current Irv during the reception period, a discharge current of (Ich-Itr) flows from the secondary battery 200 during the transmission period Ttr. When the reception period Trv is switched, a charging current for charging the secondary battery 200 of (Ich-Irv) flows. In order to prevent a decrease in the voltage between terminals, T is preferably set to a time equal to or longer than Ttr. However, in order to prevent a decrease in the voltage between terminals so that the charging period in the state where charging of the secondary battery 200 is prohibited is long, the length of T-Ttr is considered in consideration of the variation as a temporary charging permission. It is preferable to set T so that the length is as short as possible.

  Therefore, in the situation where the mobile phone to which the charger is connected is operating in the weak radio wave region when the charge prohibition condition is satisfied, the heat generation due to the current flowing through the parasitic diode is prevented and the decrease in the voltage between the terminals is suppressed. Therefore, it is possible to prevent the secondary battery from being charged by making the charging / discharging path 9 conductive for a period necessary for this purpose and continuing the conductive state.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, the switching elements 1 and 2 may replace the arrangement positions shown in FIG.

  This international application claims priority based on Japanese Patent Application No. 2008-246650 filed on Sep. 25, 2008. The entire contents of Japanese Patent Application No. 2008-246650 are hereby incorporated by reference. Incorporated into.

DESCRIPTION OF SYMBOLS 1 Charge control switching element 1a, 2a Parasitic diode 2 Discharge control switching element 3 Positive terminal 4 Negative terminal 5 Positive side input / output terminal 6 Negative side input / output terminal 9a, 9b Charging / discharging path 10 Temperature detection part 21 Voltage detection part 50 Control unit 51 Timer 90 Battery protection IC
100 battery pack 200 secondary battery 300 portable device 400 charger

Claims (4)

Switching means for switching conduction / interruption of a charging / discharging path between the input / output terminal for discharging from the secondary battery to the electronic device and charging from the charging device to the secondary battery and the bipolar terminal of the secondary battery; ,
Control means for controlling the switching operation of the switching means,
The control means detects the decrease in the terminal voltage of the input / output terminal in a state where the charge / discharge path is blocked by the switching means due to the charging prohibition condition of the secondary battery being satisfied. Providing a conduction time for temporarily turning on the charge / discharge path by a switching means, and returning the charge / discharge path to a cut-off state by the switching means when the conduction time has elapsed ;
The battery protection device according to claim 1, wherein the conduction time is set to a time synchronized with a change in an operation mode of the electronic device. The battery protection device according to claim 1 , wherein the electronic device is a portable device having a wireless communication function. The battery protection device according to claim 2 , wherein the conduction time is set to a time synchronized with a radio wave transmission / reception operation of the portable device. A battery pack comprising the battery protection device according to any one of claims 1 to 3 and the secondary battery.

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