JP2007124768A - Pack battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pack battery including an electric circuit capable of, when an overcurrent is passed due to short-circuiting or the like, quickly causing an FET element for charging in the pack battery to transition from on state to off state. <P>SOLUTION: The pack battery includes: a battery 1; an n-type semiconductor FET element 92 for discharging disposed on the high voltage side of a charging/discharging path; controlling means; and a boosting circuit 11 that controls turn-on/off of the FET element 92 for discharging at a gate voltage corresponding to a boosted on signal based on an on/off signal from the controlling means. When the FET element 92 for discharging is turned on, the boosting circuit 11 applies a battery voltage through a battery voltage application path 21 and supplies a voltage boosted higher than the battery voltage to its gate. When the FET element 92 for discharging is turned off, the boosting circuit 11 applies the battery voltage to its gate through the battery voltage application path 21 with the boosting circuit 11 bypassed. A switching element 30 is placed between the source and the gate of the FET element 92 for discharging. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery pack.

  Regarding conventional battery packs, the following patent document describes an n-type semiconductor discharging FET element arranged on the high voltage side of a charge / discharge path. The battery pack and the notebook computer that uses it as a power source need to communicate with each other in order to exchange data. The communication signal is the common ground between the battery pack and the computer (= low voltage on the charge / discharge path). Since the ground voltage fluctuates when the device is turned on and off, the FET device could not be placed on the low voltage side path. .

Therefore, in the past, when using an n-type semiconductor discharge FET element that is inexpensive and has low on-resistance, it is arranged on the high voltage side of the charge / discharge path, and the voltage boosted using a booster circuit is supplied to the element. The device was turned on by applying the voltage to the gate.
Japanese Patent Laid-Open No. 11-178224

  In the above-described conventional battery pack, when the discharging FET element is changed from the on state to the off state, the supply of the boosted voltage from the booster circuit is cut off to be in the off state. At this time, when the discharging FET element is changed from the on state to the off state, a certain amount of time is required for the electric charge accumulated in the gate to be discharged and the source and the gate to become substantially the same potential to be in the off state. . In particular, when an overcurrent is detected, it is necessary to quickly switch the discharging FET element from the on state to the off state.

  The present invention has been made to solve such problems, and when an overcurrent flows due to a short circuit accident between output terminals, the charging FET element in the battery pack is changed from an on state to an off state. An object of the present invention is to provide a battery pack having an electric circuit that can be shifted quickly.

  The present invention boosts a battery pack based on a battery, an n-type semiconductor discharge FET element disposed on the high voltage side of the charge / discharge path, a control means, and an on / off signal from the control means. A booster circuit that controls on / off of the discharging FET element with a gate voltage corresponding to an on signal, wherein the booster circuit applies a battery voltage via a battery voltage application path, and boosts the battery voltage from the battery voltage. To the gate to turn on the discharge FET element, bypass the boost circuit and apply the battery voltage to the gate in the battery voltage application path to turn off the discharge FET element, A switching element is inserted between the source of the discharging FET element and the gate.

Further, the switching element is an FET element, and a gate voltage of the switching element is supplied from the battery voltage, and a source and a drain of the switching element are provided between the source of the discharging FET element and the gate. It is connected.
It is characterized by that.

  In the present invention, when an overcurrent flows due to a short circuit accident between the output terminals or the like, by inserting a switching element between the source and the gate of the discharging FET element, the discharging FET element is turned off from the on state. You can switch quickly.

  When the gate voltage of the discharging FET element is changed from the high level in the on state to the low level in the off state in which the source and the gate are substantially at the same potential, the booster circuit is bypassed and the battery voltage application path is Since the battery voltage is applied to the gate and the discharging FET element is turned off, the charge accumulated in the gate is discharged through the battery voltage application path, so that a certain amount of time is required.

  In the present invention, a switching element is inserted between the source of the discharging FET element and the gate, the switching element is an FET element, and the gate voltage is supplied with a constant voltage from the battery voltage. The source and drain of the switching element are connected between the source of the FET element for use and the gate.

  It will be described below that this switching element can quickly change the gate voltage of the discharging FET element from the high level in the on state to the low level in the off state in which the source and the gate have substantially the same potential.

  For example, a metal foreign object such as a necklace is accidentally placed between the output terminals and a short-circuit accident occurs, or a short-circuit accident occurs in the discharge circuit on the electronic device side while attached to the electronic device, etc. When an overcurrent is detected, the battery voltage is applied to the gate in the battery voltage application path by bypassing the booster circuit, and the charge accumulated in the gate is discharged to the source, so that the source and the gate are substantially at the same potential. If there is no switching element, a certain amount of time is required to enter the OFF state as described above.

  Here, when the charge accumulated in the gate is discharged, when the gate potential approaches the source potential, the resistance between the source and drain of the discharging FET element increases, the current value of the overcurrent is reduced, and the current value is reduced. Get smaller. When the current value is reduced in a state where the output terminal is short-circuited, the electric resistance of the foreign matter is substantially constant. Therefore, the voltage between the output terminals is reduced as the current value is reduced. When the voltage between the output terminals decreases, the source potential of the switching element decreases, the gate-source voltage becomes equal to or higher than the threshold voltage, the switching element is turned on, and the discharging FET element is passed through this switching element. The electric charge accumulated in the gate of the discharge FET is quickly and instantaneously discharged, the potential between the source of the discharging FET element and the gate becomes the same potential, and the discharging FET element can be quickly and instantaneously turned off.

  In particular, as described above, when discharging the charge accumulated at the gate of the discharging FET element after overcurrent detection, the resistance between the source and drain of the discharging FET element increases as the gate potential approaches the source potential. Therefore, at this time, if an overcurrent that is a large current is kept flowing, the discharging FET element may be thermally destroyed. Therefore, in the present invention, when the resistance between the source and the drain of the discharge FET element increases, the discharge FET element is turned off quickly and instantaneously by the switching element, thereby Can be prevented from thermal destruction.

  Embodiments of the present invention will be described in detail with reference to the drawings. First, the overall configuration of the battery pack A of the embodiment will be described, and then the switching element that is a characteristic point of the embodiment will be described.

  As shown in FIG. 1, in the battery pack A of the present embodiment, a 4-cell secondary battery 1 such as lithium ion, and a current detection resistor 2 (in the current detection unit) that detects current when the battery 1 is charged and discharged. And a microprocessor unit (hereinafter referred to as MPU (= Micro Processing Unit)) that monitors and controls charging / discharging of the battery 1. When the battery pack A is installed in a personal computer (hereinafter referred to as a PC), which is an electronic device, the output from the battery 1 is supplied to the PC from the + terminal and the GND terminal. Communication is performed via communication lines SCL and SDA. On the other hand, as a charger, charging power is supplied from the PC by a constant current / constant voltage charging method in which the maximum current and the maximum voltage are regulated.

  In the MPU, the battery voltage at the measurement point d and the analog voltage at both ends of the current detection resistor 2 are digitally converted and converted into an actual voltage [mV] or an actual current value [mA], and a charge / discharge current. And the remaining capacity processing unit 4 for calculating the remaining capacity, and detecting the full charge of the battery 1, the abnormal current, the abnormal temperature of the battery detected from a separately provided temperature sensing element (not shown), When detecting an abnormal voltage, a control unit 5 is provided which controls the charge / discharge current by cutting it off.

  Here, in order to cut off the charging current and the discharging current, the control unit 5 performs the charging FET element 91 and the discharging FET element 92 which are n-channel MOSFETs arranged on the high voltage side of the charging / discharging path. In order to perform on / off control, an on / off signal is issued to a control circuit 10 including a booster circuit.

  In the control unit 5, when the voltage of the battery 1 becomes equal to or higher than the overcharge voltage (eg, 4.2 V / Cell or higher), an off signal is sent from the port CHG in order to turn off the charging FET element 91. To emit. Further, when the voltage of the battery 1 becomes equal to or lower than the overdischarge voltage (for example, 2.7 V / Cell or lower), an off signal is generated from the DSG as a port in order to turn off the discharging FET element 92.

  On the other hand, in the remaining capacity processing unit 4 of the MPU, a value obtained by multiplying the charging / discharging current converted by the A / D conversion unit 3 by a measurement unit time (for example, 250 msec) is integrated. The value is subtracted or, at the time of charging, the integrated value is added from the remaining capacity at the start of charging. The remaining capacity of the battery 1 is calculated by such calculation.

  Further, the control unit 5 is fully charged from the battery voltage and charging current converted by the A / D conversion unit 3 (in constant current / constant voltage charging in which the current and voltage are regulated, the voltage is a predetermined value or more. When the condition is less than or equal to a predetermined value, it is detected that the battery is fully charged), and information indicating that the remaining capacity is 100% is output.

  A communication data creation unit that creates various types of battery information such as battery voltage, remaining capacity, charge / discharge current value, etc., in signal data that can be received by the electronic device for a PC (= personal computer), a charger, etc. 6, a driver unit 7 for actually communicating with a PC or a charger, and a memory 8 for storing various parameters for calculating the remaining capacity and various data. In addition, the driver unit 7 receives a request for transmission of various information of the battery pack from the electronic device, and transmits the data created by the communication data creation unit 6 from the driver unit to the electronic device. The communication data creating unit 6, the drive unit 7, and the memory 8 are a communication unit COM that performs communication with an electronic device or the like.

  Further, the remaining capacity processing unit 4 has the following functions. When the secondary battery 1 such as lithium ion is repeatedly charged in the vicinity of the full charge voltage, deterioration of the battery itself is promoted, or an overcharge prevention circuit or element that is a safety component in the battery cell frequently operates. Thus, an adverse effect of shortening the cycle life of such a circuit or element occurs. In order to avoid such a problem, in the present embodiment, the remaining capacity processing unit 4 drops to a predetermined remaining capacity (for example, 95% or less) or a predetermined voltage (for example, 4 V / cell) corresponding thereto. Until then, the instruction information for prohibiting charging is output to the PC and the charger side via the communication data creation processing unit 6.

  Next, the control circuit 10 including the booster circuit will be described. In the control circuit 10, on / off control is performed by supplying on / off signals to the gates of the charging FET element 91 and the discharging FET element 92 based on the on / off signals from the DSG and CHG of the MPU. The gate of the element is provided with a booster circuit 11 composed of a booster circuit 11C and a booster circuit 11D because it is necessary to supply a voltage higher than the battery voltage in order to turn it on. An on / off signal is applied to the gate of the charging FET element 91 from CHG which is a port of the control circuit 10, and an on / off signal is applied to the gate of the discharging FET element 92 from DSG which is a port of the control circuit 10. Is done.

  In the following, the signals from the booster circuit 11D and the port DSG will be described in detail. Since the signals from the booster circuit 11C and the port CHG have the same configuration and operation, the same reference numerals as those of the booster circuit 11D are attached and the description will be given. Omitted.

  The battery voltage on the high voltage side of the charge / discharge path is input from the port PACK to the DSG of the booster circuit 11 via the battery voltage application path 21 including the resistor R4 (about 10 KΩ), and an on / off signal from the port DSG. Is supplied to the gate of the discharging FET element 92 via a resistor R2 (about 10 KΩ). Such resistors R2 and R4 prevent noise from entering the control circuit 10 from the charging / discharging path on the high voltage side, or when the short circuit accident occurs in the control circuit 10, the current suddenly flows from the battery. It is provided for the purpose of preventing inflow. A resistor R1 attached between the gate and source of the discharging FET element 92 is provided to completely turn off the voltage between GS when the FET is turned off.

  The step-up circuit 11D is called a charge pump, and has a configuration in which an oscillator OSC that oscillates at several tens of kHz, a supply switch 12 that is on / off controlled based on an on / off signal of the MPG DSG output, When the supply switch 12 is on, a buffer circuit 13 is provided to which an output from the oscillator OSC is input. Further, the battery voltage is supplied to the buffer circuit 13 as a power supply voltage via the battery voltage application path 21. Further, the supply switch 12 may be omitted, and the buffer circuit 13 may be turned on / off based on the on / off signal of the MPU DSG output.

  A capacitor 14C for generating a voltage by accumulating the output from the buffer circuit 13 as an electric charge, and a diode 14D1 and a diode 14D2 provided in a direction in which a current flows from the battery voltage are provided. One end of the side is connected to the branch point T. Also, a switch SW that is turned off and on based on the on / off signal of the MPU DSG output is provided at both ends of the two diodes 14D1 and 14D2 connected in series (when the DSG output is on, the switch When SW is in the off state and the DSG output is off, the switch SW is in the on state).

  The booster circuit 11D having the above configuration generally operates as follows. When the FET element is turned on, the switch SW is turned off by the on signal of the MPG terminal DSG output, the supply switch 12 is turned on, and the buffer circuit 13 to which the oscillator OSC output is input receives the substantially battery voltage. A voltage that oscillates between the lowest voltage (= battery voltage−12 V) is output (a schematic output waveform example is shown in FIG. 1). The supply switch 12 may be turned on / off, and the supply switch 12 may be omitted to turn on / off the oscillation of the oscillator OSC.

  When the lowest voltage is output from the buffer circuit 13, the voltage across the capacitor 14C is substantially a battery voltage.

  Next, when a substantially battery voltage is output from the buffer circuit 13, the charge of the capacitor 14C that has become the substantially battery voltage is held without flowing to the battery side because of the diode 14DC. In this case, the electric charge accumulated in the previous step is accumulated on the battery voltage on the negative electrode side of the capacitor 14C. Such charges are accumulated in the parasitic capacitance between the gate and the source of the FET element 92, and a voltage higher than the battery voltage capable of turning the FET element 92 on can be supplied to the gate. it can. In addition to the parasitic capacitance between the gate and the source, a capacitor may be separately provided between the terminal DSG and the gate. However, for such a capacitor, when the FET element 92 is turned from the on state to the off state, it may take time to discharge the charge.

  When the FET element is turned off, the switch SW is turned on and the supply switch 12 is turned off by an off signal of the MPS terminal DSG output. At this time, the oscillation of the oscillator OSC may be stopped. Since the switch SW is turned on, the battery voltage is applied to the gate via the battery voltage application path, bypassing the booster circuit 11, and therefore, the parasitic capacitance is accumulated between the source and the gate. The electric charge is discharged through the battery voltage application path.

  Here, if there is no switching element 30 to be described later, when an overcurrent such as a short circuit of the output terminal is detected, the charge accumulated in the gate is discharged, and the source and the gate become substantially the same potential and are in the off state. It takes a certain amount of time to become.

  In this embodiment, the switching element 30 is provided in order to discharge the charge accumulated in the gate when an overcurrent such as a short circuit of the output terminal is detected. The element 30 is an n-channel MOSFET element, and the switching element 30 is inserted between the source and the gate of the discharging FET element 92, and the gate voltage is supplied with a constant voltage from the battery voltage. The source and drain of the switching element are connected between the source of the FET element for use and the gate. The constant voltage applied to the gate via the resistor R3 is a voltage of 2.5 V supplied from the battery voltage by a regulator circuit (not shown) in the battery pack A.

  As described above, for the abnormal current that is an overcurrent, the charging FET element 91 and the discharging FET element 92 are turned off by the program execution process of the control unit 5 in the MPU. It takes time (about 1.0 S or less) until an overcurrent actually flows and the device is turned off. In this embodiment, when a very large overcurrent flows due to a short circuit of the battery pack A or the like, it takes time to turn off the charging FET element 91 and the discharging FET element 92 from the MPU. Prior to the program execution process, the discharging FET element 92 is turned off by the function of the control circuit 10. The control circuit 10 includes a voltage detection circuit 19 that detects the voltage across the current detection resistor 2. In this voltage detection circuit 19, when a voltage larger than a predetermined voltage and corresponding to an overcurrent is input, the voltage detection circuit 19 turns off the discharging FET element 92 from the voltage detection circuit 19 to the booster circuit 11D. Similarly to the MPU, an off signal is issued to turn on the switch SW and turn off the supply switch 12. Thus, the control circuit 10 has a protection circuit function. In addition, the protection circuit function of the control circuit 10 is eliminated, and the charge FET element 91 and the discharge FET element 92 are turned off by the program execution process of the control unit 5 in the MPU as described above. Only the circuit function may be used. In the present invention, the control circuit 10 or the control unit 5 is used as a control means for turning off the charging FET element 91 and the discharging FET element 92 as a protection circuit function.

  Hereinafter, the operation of the switching element 30 which is a feature of the present embodiment will be described in detail.

  For example, a metal foreign object such as a necklace is accidentally placed between the output terminals and a short-circuit accident occurs, or a short-circuit accident occurs in the discharge circuit on the electronic device side while attached to the electronic device, etc. When an overcurrent such as an output terminal is short-circuited is detected, the voltage detection circuit 19 of the control circuit 10 detects it, and in order to turn off the discharging FET element 92, an off signal is issued and the switch SW is turned on. And the supply switch 12 is turned off. Thereby, the battery voltage is applied to the gate in the battery voltage application path by bypassing the booster circuit 11D, and the charge accumulated in the gate is discharged to the source or the like, and the source and the gate become substantially the same potential and are turned off. To enter the state, if there is no switching element, a certain amount of time is required as described above. In particular, the resistors R2 and R4 are provided in order to prevent noise and short circuit, so that time is required.

  If the switching element 30 is not provided, the discharge current (channel CH3), the voltage between the gate and the source of the discharge FET element 92 (the gate voltage with reference to the source) (channel) with the passage of time (T) at this time CH1) is shown in FIG. CH3 in FIG. 2A indicates a voltage across the current detection resistor 2, and as shown in this graph, a large current starts to flow due to a short circuit or the like. Then, after about 370 μsec (100 μsec / div) has elapsed from the current generation, the voltage detection circuit 19 emits an off signal, the switch SW is turned off, and the supply switch 12 is turned on, so that the gate is accumulated at the gate. The discharged electric charge is discharged, and the GS voltage of CH1 in FIG. When about 680 μsec (t1) elapses and the GS voltage becomes about 2.0 V or less, the discharging FET element 92 is turned off and the current is almost zero.

  FIG. 2B shows the discharge current (CH3) (showing the voltage across the current detection resistor 2) and the voltage between the gate and source of the discharge FET element 92 over time (T) in this embodiment. (Gate voltage with reference to the source) (CH1) and gate-source voltage (CH2) of the switching element 30 are shown. In FIG. 2B, as described above, an overcurrent is generated, and about 370 μsec (100 μsec / div) has elapsed from the occurrence of the current, and then the voltage detection circuit 19 generates an OFF signal, and the switch SW is turned on. When the supply switch 12 is turned on in the off state, the charge accumulated in the gate is discharged, and the voltage between GS of CH1 in FIG. 2B gradually decreases.

  Further, the change with time of the GS voltage (CH2) of the switching element 30 will be described below. When discharging the charge accumulated at the gate of the discharging FET element 92, when the gate potential approaches the source potential, the resistance between the source and drain of the discharging FET element 92 increases, and the current value of the overcurrent is reduced. The current value becomes small. When the current value is reduced in a state where the output terminal is short-circuited, the electric resistance of the foreign matter is substantially constant. Therefore, the voltage between the output terminals is reduced as the current value is reduced. As the voltage between the output terminals decreases, the source potential of the switching element 30 decreases, the gate-source voltage becomes equal to or lower than the gate threshold potential, and the switching element is turned on 30. That is, since a constant voltage (about 2.5 V) is supplied from the regulator circuit to the gate of the switching element 30, when the source potential decreases to about 0.5 V, which is close to zero V, an elapsed time of about 640 msec ( At t2), the GS voltage (CH2) of the switching element 30 becomes approximately 2.0 V, and the gate voltage is turned on, so that the switching element 30 is turned on. The charges accumulated in the gate of the discharging FET element 92 are quickly and instantaneously discharged through the switching element 30 in the on state, and the potential between the source and the gate of the discharging FET element 92 becomes the same potential. In addition, the discharging FET element can be turned off to interrupt the current.

  In particular, as described above, when discharging the charge accumulated in the gate of the discharging FET element after the overcurrent detection, when the gate potential approaches the source potential, the resistance between the source and drain of the discharging FET element 92 is increased. At this time, if an overcurrent that is a large current continues to flow, the discharging FET element 92 may be thermally destroyed. Therefore, in the present embodiment, when the resistance between the source and drain of the discharging FET element 92 increases, the switching FET element 92 quickly and instantaneously turns off the discharging FET element 92 as described above. It is possible to prevent thermal destruction of the discharge FET element 92. As can be seen in FIGS. 2A and 2B, in this embodiment, by using the switching element 30, the discharge FET element 92 is turned off from the start of the overcurrent, thereby interrupting the current. In addition, it is improved by about 40 μsec (t1-t2).

It is a circuit block diagram of the battery pack of the present invention. It is a graph which shows the electrical property of the Example of this invention.

Explanation of symbols

A Battery pack PC Electronic device MPU Microprocessor unit 1 Battery 2 Current detection resistor (current detection unit)
4 remaining capacity integration processing unit 5 control unit 91 charging FET element 92 discharging FET element 10 control circuit 11 boosting circuit

Claims (2)

In the battery pack, the battery, the n-type semiconductor discharge FET element arranged on the high voltage side of the charge / discharge path, the control means, and the boosted on signal based on the on / off signal from the control means And a booster circuit that controls on / off of the discharging FET element with the gate voltage,
In the booster circuit, a battery voltage is applied via a battery voltage application path, a voltage boosted from the battery voltage is supplied to the gate to turn on the discharging FET element, and the booster circuit is bypassed. Applying the battery voltage to the gate in the battery voltage application path to turn off the discharging FET element,
A battery pack, wherein a switching element is inserted between a source of the discharging FET element and the gate. The switching element is an FET element, and the gate voltage is supplied with a constant voltage from the battery voltage,
2. The battery pack according to claim 1, wherein a source and a drain of the switching element are connected between the source of the discharging FET element and the gate.

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