JPH11258280A - Voltage detector for secondary battery and secondary battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detector made into an integrated circuit capable of easily setting a shut-down detection voltage and a restoration detection voltage corresponding to a secondary battery. SOLUTION: This voltage detector is provided with voltage dividing resistors R1 -R3 for voltage-dividing the battery voltage of the secondary battery by a prescribed voltage dividing ratio, a comparator 11 for comparing a detection voltage obtained through the voltage dividing resistors R1 -R3 with a prescribed reference voltage and a voltage dividing ratio control means for charging the voltage dividing ratio of the voltage dividing resistors R1 -R3 corresponding to the output of the comparator 11 and imparting hysterisis characteristics to the comparator 11. Especially, the voltage dividing resistors R1 -R3 are turned to discrete components externally attached to a voltage detector body 10 made into the integrated circuit with the comparator 11 and the voltage dividing ratio control means as a subject and the resistance value is easily adjusted. Also, the voltage detector body 10 made into the integrated circuit is shared by the various secondary batteries.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage detecting device for a secondary battery which is integrated and suitable for detecting a charging voltage of a secondary battery of various specifications, and a package of the voltage detecting device together with the secondary battery. The present invention relates to a secondary battery device.

[0002]

2. Related Art In recent years, secondary batteries such as lithium ion batteries and nickel hydrogen batteries have been actively used as internal power supplies in electronic devices such as notebook personal computers and mobile phones. In recent years, various secondary battery devices in which a fuel gauge (FG) circuit for controlling charging and discharging of a secondary battery is packaged integrally with the secondary battery have been developed as a so-called battery pack.

[0003] One of the important functions of this type of fuel gauge circuit is a voltage detecting device that monitors the charging voltage of a secondary battery and is used to prevent excessive charging and discharging of the secondary battery. . This voltage detection device basically detects when the charge / discharge voltage of the secondary battery reaches the shutdown voltage and turns off a switch (for example, FET) that controls the charge / discharge of the secondary battery, This serves to prevent excessive charging and discharging of the secondary battery.

Incidentally, when the secondary battery recovers from the above-mentioned shutdown voltage, if this is detected at the same level as the shutdown, if the switch for charging / discharging control is turned on, the secondary battery will return to the shutdown voltage again. May return to Therefore, the voltage detection device generally detects the charge / discharge voltage of the secondary battery by providing a difference between the shutdown detection voltage and the recovery detection voltage, that is, a voltage detection device having a predetermined width of hysteresis. The characteristics are set.

[0005]

In the case where a secondary battery device (battery package) is realized by integrally packaging the above-described voltage detecting device together with the secondary battery, it is necessary to consider the reliability and the mounting cost. It is preferable that the voltage detecting device is formed as an integrated circuit. For example, the voltage detecting device is formed as a circuit as shown in FIG.

The voltage detecting device shown in FIG. 4 will be described. This voltage detecting device has a battery voltage Vbat of a secondary battery.
Is mainly composed of the comparator 1 which operates using the power supply. The reference voltage Vref generated from the battery voltage Vbat is supplied to the inverting input terminal (-) of the comparator 1 by the constant current source 2 and the constant voltage diode 3, and the voltage dividing resistors R1, R2, A comparison voltage obtained by dividing the battery voltage Vbat at R3 is applied to a non-inverting input terminal (+) of the comparator 1, so that the battery voltage Vbat is monitored, and this is compared and detected.

By the way, the comparator 1 is connected in series between the power supplies at its output and is provided to form a driver circuit.
The channel type FET 4 and the p-channel type FET 5 are selectively made conductive, thereby providing an output p-channel type FET.
6 is turned on and off. At the same time, the p-channel FET 7 for hysteresis control is turned on / off at the output, thereby selectively short-circuiting the voltage dividing resistor R3, thereby changing the voltage dividing ratio with respect to the battery voltage Vbat.

By the way, in the voltage detection device integrated as described above, the shutdown detection voltage and its recovery detection voltage, which are the operating characteristics, and the width of the hysteresis are the same as those of the voltage dividing resistors R1, R2, and R3. Determined by value. However, the optimum shutdown detection voltage and its recovery detection voltage for the secondary battery differ depending on the characteristics of the secondary battery. In particular, not only the battery type is determined according to the specifications of the secondary battery, but also a single battery cell (unit cell) or a plurality of battery cells connected in series or further in parallel. Implemented as a battery block. For this reason, voltage detectors integrated into integrated circuits with operating characteristics according to the specifications of the secondary battery are individually developed,
Alternatively, it is necessary to prepare in advance a plurality of types of integrated circuit voltage detectors having different operation characteristics, and select and use the integrated voltage detector. It has been difficult to share the voltage detector as an integrated circuit.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an integrated circuit capable of easily setting a shutdown detection voltage and a recovery detection voltage for secondary batteries of various specifications. To provide an improved voltage detection device. Another object of the present invention is to provide a secondary battery device having high operation stability in which such a voltage detection device is packaged integrally with a secondary battery.

[0010]

In order to achieve the above-mentioned object, a voltage detecting device for a secondary battery according to the present invention comprises: a voltage dividing resistor for dividing the battery voltage of the secondary battery at a predetermined voltage dividing ratio;
A comparator for comparing a detection voltage obtained through the voltage dividing resistor with a predetermined reference voltage, and changing a voltage dividing ratio of the voltage dividing resistor in accordance with an output of the comparator to provide the comparator with a hysteresis characteristic. A voltage dividing device which is externally attached to a voltage detecting device main body which is formed as an integrated circuit mainly by the comparator and the voltage dividing ratio controlling means. It is characterized by parts.

Further, in the secondary battery device according to the present invention, the voltage detection device configured as described above is packaged integrally with secondary batteries of various specifications, and a shutdown detection voltage according to the performance of the secondary battery is provided. And a reset detection voltage. That is, according to the present invention, a voltage dividing resistor for setting a shutdown detection voltage and a reset detection voltage for a secondary battery is externally provided to a voltage detection device main body formed mainly of a comparator and a voltage division ratio control unit. It is characterized in that the resistance value can be easily adjusted by using discrete components attached thereto, and that the voltage detecting device body to be integrated is shared with secondary batteries of various specifications.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a voltage detecting device for a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a voltage detection device for detecting a shutdown voltage of a secondary battery and a return voltage thereof.
2, R3 is a voltage dividing resistor for detecting the voltage Vbat of the secondary battery by dividing the voltage. These voltage dividing resistors R1, R2, and R3 are composed of discrete components external to the voltage detection device main body 10 that is formed into a trail circuit as described below, and a circuit in which the voltage detection device main body 10 is mounted. It is mounted on a substrate (not shown) and connected to the voltage detection device main body 10.

The voltage detecting device main body 10 includes a comparator 11 which operates using the battery voltage Vbat of the secondary battery as a power supply.
And the voltage dividing resistors R1 and R2 according to the output of the comparator 11.
2, a voltage division ratio control means for giving a hysteresis to the operation characteristics of the comparator 11 by changing the voltage division ratio of the battery voltage Vbat by R3, and these are realized as an integrated circuit. That is, the comparator 11 has its inverting input terminal
The reference voltage Vref generated from the battery voltage Vbat by the constant current source 12 and the constant voltage diode 13 is input to (−),
The detection voltage obtained by dividing the battery voltage Vbat by the voltage dividing resistors R1, R2, R3 is input to its non-inverting input terminal (+), and these voltages are compared.

The voltage dividing resistors R1, R2, R3 are connected to the terminals a,
b, c, respectively, and the terminal a is connected to a common contact of the switch 14 constituting the voltage division ratio control means,
The terminals b and c are connected to a normally closed contact and a normally open contact of the switch 14, respectively. The switch 14 is realized, for example, as a semiconductor analog switch that performs a switching operation faster than the comparator 11. Thus, the voltage dividing resistor R1 is connected between the terminal a and the positive electrode (+) of the secondary battery, and the voltage dividing resistors R2, R
Reference numeral 3 is connected between each of the terminals b and c and the negative electrode (-) of the secondary battery.

By connecting the voltage dividing resistors R1, R2, and R3 to the terminals a, b, and c in this manner, when the switch 14 is turned off, the battery voltage Vbat of the secondary battery becomes V1. = Vbat ｛{R2 / (R1 + R2)}, and when the switch 14 is turned on, V2 = Vbat ｛{R3 / (R1 + R3)}. The voltage dividing resistors R2 and R3 are set, for example, as [R2> R3] as described later.

The output of the comparator 11 is supplied to the voltage detection signal Vo via two inverter circuits 15 and 16 in order.
ut is output to a charge / discharge control circuit (not shown). The output of the inverter circuit 15 is
A p-channel type F for selectively driving the switch 15
Given to ET17 to operate the FET17,
The switch 15 is selectively turned on and off by the FET 17. In the drawing, reference numeral 18 denotes a load resistance of the FET 17.

According to the voltage detecting device thus constructed, when the battery voltage Vbat of the secondary battery is sufficiently higher than its shutdown voltage (initial state), for example, the output of the comparator 11 is at the [H] level. It is assumed that the switch 14 is in the OFF operation state. In this case, since the voltage dividing resistor R2 is selected through the switch 14, the battery voltage Vbat of the secondary battery is
Is supplied to the non-inverting input terminal (+) of the comparator 11 as the above-described detection voltage V1 by being divided by the voltage dividing resistors R1 and R2. Since the detection voltage V1 at this time is higher than the reference voltage Vref, the output of the comparator 11 becomes the [H] level, and the above-described initial state is set.

From such an initial state, the battery voltage Vbat gradually decreases with the discharge of the secondary battery, and the voltage V1 detected by being divided by the voltage dividing resistors R1 and R2 is equal to the reference voltage Vref. When the value falls below this, the output of the comparator 11 is inverted to the [L] level. Then, in response to this, the output Vout of the voltage detecting device main body 10 is inverted to the [L] level, and it is detected that the battery voltage Vbat of the secondary battery has fallen below the shunt down voltage. At the same time, the FET 17 receiving the output of the inverter circuit 15 is turned on, whereby the switch 14 is quickly switched and turned on.

With the turning-on operation of the switch 14, the battery voltage Vbat is divided by the voltage dividing resistors R1 and R3, and supplied to the comparator 11 as a detection voltage V2 (<V1). Therefore, when the detection voltage V1 becomes lower than the reference voltage Vref and the comparator 11 inverts, the switch 14 is instantaneously switched in response to the output, and the detection voltage V1
Instead, the detection voltage V2 lower than the detection voltage V1 is supplied to the comparator 11, so that the comparator 11 is stabilized with the output inverted as described above.

Thereafter, even if the battery voltage Vbat of the secondary battery gradually recovers and the battery voltage Vbat reaches the shunt-down voltage, the switch 14 is in the ON operation state as described above. Non-inverting input terminal
The detection voltage V2 applied to (+) does not exceed the reference voltage Vref, and the comparator 11 does not perform the inversion operation. However, when the battery voltage Vbat of the secondary battery further recovers and the voltage V2 detected by being divided by the voltage dividing resistors R1 and R3 exceeds the reference voltage Vref, the comparator 11
Perform an inverting operation, and its output becomes the [H] level.

As a result, the output V of the voltage detecting device
out is inverted to the [H] level, and the battery voltage Vb of the secondary battery is
It is detected that at has returned to the normal value. At the same time, the FET 17 is turned off by the output of the inverter circuit 15, whereby the switch 14 is quickly switched and turned off. And the voltage dividing resistor R3
Instead, the voltage dividing resistor R2 is connected again to the circuit, and the detection voltage V1 detected by dividing the voltage by the voltage dividing resistors R1 and R2 is given to the comparison 11, and the battery voltage of the secondary battery is Detection of a drop beyond the shunt-down voltage of Vbat will be performed.

Therefore, according to the voltage detecting device configured as described above, the change in the battery voltage Vbat of the secondary battery is changed by the power supply voltage Vbat by the voltage dividing resistors R1, R2 and R3 as shown in FIG. By simply switching the voltage dividing ratio according to the output of the comparator 11, it is possible to individually set the shutdown detection voltage and the recovery detection voltage, and to perform detection with a predetermined width of hysteresis. In particular, the voltage dividing resistors R1, R2, R
3. The voltage dividing ratio of the battery voltage Vbat by
1 can be individually set as a resistance value of a discrete component externally attached thereto, so that it can be adjusted according to the performance of the secondary battery and its voltage detection level (shunt down detection voltage, recovery The detection voltage can be set arbitrarily.

Therefore, in realizing the secondary battery device (battery pack), even if the specifications of the secondary battery are not determined, the voltage detecting device main body 10 having the above-described configuration and integrated into an integrated circuit is used. The voltage dividing resistors R1, R2, and R3 externally attached to the voltage detection device main body 10 may be determined according to the characteristics of the secondary battery finally evaluated and determined. The development of a secondary battery device (battery pack) becomes very easy. Further, the development period can be significantly reduced. Further, since the voltage detecting device main body 10 integrated as described above can be commonly used for secondary batteries of various specifications, the voltage detecting device main body 1 having various configurations (characteristics) can be used.
It is not necessary to prepare 0, and the development of the situation of the voltage detection device main body 10 can be facilitated, so that effects such as reduction of the overall manufacturing cost can be achieved.

In the above-described configuration, the voltage dividing resistors R1,
Since R2 and R3 are externally attached to the voltage detection device main body 10, for example, the value of the external resistance is changed according to the time of charging and discharging of the secondary battery, whereby the detection voltage and the hysteresis width during charging are changed. Further, the detection voltage at the time of discharging and the hysteresis width thereof can be set separately. Specifically, depending on whether the secondary battery is in a charged state or a discharged state, for example, resistors R4 and R5 are selectively connected in parallel to the voltage dividing resistors R2 and R3, respectively, R2, R3 and resistors R4, R5 may be selectively switched. This eliminates the need to prepare two voltage detecting devices, one for detecting the voltage during charging and the other for detecting the voltage during discharging, so that a secondary battery device (battery pack) is realized as described below. In this case, the configuration can be simplified.

When the voltage detecting device having the above configuration is packaged integrally with a secondary battery to realize a secondary battery device (battery pack), it may be configured as shown in FIG. 3, for example. That is, a switch 21 composed of an FET and a resistor 22 for detecting a charge / discharge current are connected in series to the secondary battery BAT. In addition, a temperature sensor 23 for detecting the temperature inside the secondary battery BAT, a fuel cage circuit 24, a microprocessor 25 for controlling the operation thereof, and the above-described voltage detection circuit 10 are integrally packaged to form a secondary battery device (battery). The fuel cage circuit 24 includes, for example, a power switch circuit 24a, a current measurement circuit 24b, and a voltage measurement circuit 24c.
An overcurrent protection circuit 24d and a switch driver 2e are provided. Then, while taking in the battery temperature detected by the temperature sensor 23 through the AD converter 25a built in the microprocessor 25, the charge / discharge current of the secondary battery BAT and the battery voltage are measured, and the remaining battery capacity is measured. The secondary battery device may be configured to control the charge and discharge while monitoring. At this time, the voltage detection device 10 outputs the fuel cage circuit 24
And controls the operation of the microprocessor 25 to ensure stable operation.

At this time, it is possible to determine whether the secondary battery is charging or discharging based on the direction of the current detected by the fuel cage circuit 24. The determination result is used based on the determination result. If the switching control is executed, it is possible to reliably perform voltage detection according to charging / discharging of the secondary battery with only one voltage detection device as described above.

The present invention is not limited to the above embodiment. For example, the configuration of the comparator 11 constituting the voltage detection device main body 10 and the configuration of the voltage dividing ratio control means for the voltage dividing resistors R1, R2, R3 can be variously modified. For example, it is of course possible to connect the voltage dividing resistors R1, R2, and R3 in parallel with each other to change the voltage dividing ratio. In addition, a voltage dividing resistor R1, R2, R3 having a predetermined resistance value is built in in advance, and an external resistor corresponding to the built-in voltage dividing resistor can be connected in series or in parallel. Is also possible. Other. The present invention can be implemented with various modifications without departing from the scope of the invention. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0028]

As described above, according to the present invention, the detection voltage obtained by dividing the battery voltage of the secondary battery by the predetermined voltage dividing ratio by the voltage dividing resistor is compared with the predetermined reference voltage in the comparator. And a voltage dividing ratio control means for changing the voltage dividing ratio of the voltage dividing resistor in accordance with the output of the comparator to provide the comparator with a hysteresis characteristic, wherein the voltage dividing resistor is connected to the comparator and the voltage dividing ratio. Since the control means is a discrete component externally attached to the voltage detection device main body formed as an integrated circuit, the shutdown detection voltage and the recovery detection voltage for the secondary batteries of various specifications can be obtained simply by adjusting the voltage dividing resistor. Can be easily set.

In particular, since the main body of the voltage detecting device formed into an integrated circuit can be shared with secondary batteries of various specifications, development of the secondary battery device packaged integrally with the voltage detecting device and the secondary battery is facilitated. Therefore, a great effect can be obtained in practical use, such as inexpensive production.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a voltage detection device for a secondary battery according to an embodiment of the present invention.

FIG. 2 is a transition diagram showing operating characteristics of the voltage detection device shown in FIG. 1 with respect to a change in battery voltage Vbat.

FIG. 3 is a schematic configuration diagram of a secondary battery device (battery pack) configured by integrally packaging the voltage detection device and the secondary battery shown in FIG. 1;

FIG. 4 is a diagram showing a configuration example of a conventional voltage detection device integrated into a circuit.

[Explanation of symbols]

 BAT Secondary battery R1, R2, R3 Voltage dividing resistor (discrete part) 10 Voltage detecting device main body (integrated circuit) 11 Comparator 12 Constant current source 13 Constant voltage diode (reference voltage) 14 Switch 15 Inverter circuit 16 Inverter circuit 17 FET 18 Load resistance

Claims (2)

[Claims] 1. A voltage dividing resistor for dividing a battery voltage of a secondary battery at a predetermined voltage dividing ratio, a comparator for comparing a detection voltage obtained through the voltage dividing resistor with a predetermined reference voltage, Voltage dividing ratio control means for changing the voltage dividing ratio of the voltage dividing resistor according to the output of the voltage dividing device to provide a hysteresis characteristic to the comparator, wherein the voltage dividing resistor comprises the comparator and the voltage dividing ratio controlling means. A voltage detection device for a secondary battery, wherein the voltage detection device is a discrete component externally attached to a voltage detection device main body formed as an integrated circuit. 2. A secondary battery device, wherein the voltage detector for a secondary battery according to claim 1 is packaged integrally with the secondary battery.