Temperature determination circuit for charging

Abstract

To properly determine suitability of temperature of a storage battery according to R-T characteristics of a thermistor installed in the storage battery.SOLUTION: In a temperature determination circuit, a thermistor RT for temperature measurement is arranged in a lithium-ion battery B, with the upper limit temperature of the lithium-ion battery B allowed at the time of charging as allowable upper limit temperature TH. The temperature determination circuit includes: a first comparator 3 that compares a resistance value of the thermistor RT for temperature measurement while the lithium-ion battery B is charged with a resistance value indicated by the thermistor RT for temperature measurement at the allowable upper limit temperature TH; and an AND circuit 5 that determines suitability of temperature TDET while the lithium-ion battery B is charged based on the comparison result by the first comparator 3, and outputs the result.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a temperature determination circuit for charging, which determines whether the temperature of a storage battery during charging is appropriate. [Background technology]

[0002] For example, lithium ion batteries are generally charged using a constant current / constant voltage charging method that manages the charging voltage and charging current. In addition, in order to prevent abnormal overheating of the lithium ion battery, charging must be stopped when the temperature of the lithium ion battery deviates from a specified temperature range. For this reason, a thermistor has conventionally been installed in the lithium ion battery to manage the temperature and charging of the lithium ion battery (see, for example, Patent Document 1).

[0003] That is, the temperature of the lithium-ion battery is measured by utilizing the fact that the resistance value of the thermistor changes with temperature.Then, in a charge management IC (Integrated Circuit), charging continues if the measured temperature is within a preset temperature range, and stops charging if it is outside the preset temperature range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-187585 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the temperature characteristics of a thermistor (RT characteristics that indicate the relationship between resistance value and temperature) may differ depending on the type and manufacturer of the lithium-ion battery. In other words, even at the same temperature, the resistance value indicated by the thermistor may differ for each lithium-ion battery. Since conventional charge management ICs cannot absorb or correct such differences in the resistance values ​​indicated by thermistors, the types of lithium-ion batteries that can be used with one charge management IC are limited. In other words, it was necessary to provide a different charge management IC for each lithium-ion battery with a different thermistor.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a charging temperature determination circuit that can properly determine whether the temperature of a storage battery is appropriate in accordance with the RT characteristics of a thermistor disposed in the storage battery. [Means for solving the problem]

[0007] In order to solve the above problem, the invention described in claim 1 is a charging temperature judgment circuit characterized in that a temperature measuring thermistor is provided in a storage battery, the upper limit temperature of the storage battery that is allowable during charging is defined as an allowable upper limit temperature, and the circuit is equipped with an upper limit temperature comparison unit that compares the resistance value of the temperature measuring thermistor while the storage battery is charging with the resistance value indicated by the temperature measuring thermistor at the allowable upper limit temperature, and a judgment output unit that judges whether the temperature during charging of the storage battery is appropriate based on the comparison result by the upper limit temperature comparison unit and outputs the judgement result.

[0008] The invention described in claim 2 is characterized in that, in the charging temperature judgment circuit described in claim 1, the lowest temperature allowable for the storage battery during charging is set as an allowable lower limit temperature, and a lower limit temperature comparison unit is provided which compares the resistance value of the temperature measurement thermistor while the storage battery is charging with the resistance value indicated by the temperature measurement thermistor at the allowable lower limit temperature, and the judgment output unit judges whether the temperature during charging of the storage battery is appropriate based on the comparison result by the upper limit temperature comparison unit and the comparison result by the lower limit temperature comparison unit, and outputs the judgment.

[0009] The invention described in claim 3 is characterized in that, in the charging temperature determination circuit described in claim 2, the resistance value exhibited by the temperature measurement thermistor at the allowable upper limit temperature that is the object of comparison by the upper limit temperature comparison unit, and the resistance value exhibited by the temperature measurement thermistor at the allowable lower limit temperature that is the object of comparison by the lower limit temperature comparison unit are changeable. Effect of the Invention

[0010] According to the invention described in claim 1, the resistance value of the temperature measurement thermistor while the storage battery is being charged is compared with the resistance value indicated by this temperature measurement thermistor at the allowable upper limit temperature to determine whether the temperature of the storage battery being charged exceeds the upper limit and output the result. In other words, since the resistance value indicated by the allowable upper limit temperature of the temperature measurement thermistor that actually measures the temperature of the storage battery being charged is used to determine whether the temperature is appropriate, it is possible to make an appropriate determination according to the RT characteristic of the temperature measurement thermistor provided in the storage battery.

[0011] Then, by having a charge management IC or the like manage charging based on the result of the determination by such a charging temperature determination circuit, it becomes unnecessary to provide a different charge management IC or the like for each storage battery having a different temperature measurement thermistor.

[0012] According to the invention described in claim 2, the resistance value of the temperature measurement thermistor while the storage battery is being charged is compared with the resistance value indicated by this temperature measurement thermistor at the allowable lower limit temperature to determine whether the temperature of the storage battery being charged exceeds (falls below) the lower limit, and output the result. In other words, since the resistance value indicated by the temperature measurement thermistor, which actually measures the temperature of the storage battery being charged, at the allowable lower limit temperature is used to determine whether the temperature is appropriate, it becomes possible to make an appropriate determination according to the RT characteristic of the temperature measurement thermistor arranged in the storage battery.

[0013] According to the invention described in claim 3, the resistance values ​​indicated by the temperature-measuring thermistor at the allowable upper limit temperature and the allowable lower limit temperature, which are the objects of comparison by the upper limit temperature comparator and the lower limit temperature comparator, can be changed. Therefore, by changing these resistance values ​​(the resistance values ​​to be compared) according to the RT characteristics of the temperature-measuring thermistors arranged in the storage battery, it becomes possible to accommodate a plurality of temperature-measuring thermistors with different RT characteristics with one charging temperature determination circuit. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a charging temperature determination circuit according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the present invention will be described based on the illustrated embodiment.

[0016] 1 is a schematic diagram showing a charging temperature determination circuit 1 according to an embodiment of the present invention, and the part other than that enclosed by a dashed line in the figure constitutes the charging temperature determination circuit 1. This charging temperature determination circuit 1 is a circuit that determines whether the temperature of the storage battery during charging or the like is appropriate (whether the temperature of the storage battery is within an allowable temperature range or not), and in this embodiment, a case will be described in which the storage battery, which is the part enclosed by the dashed line in the figure, is a lithium-ion battery B.

[0017] Here, the lithium ion battery B is provided with a temperature measuring thermistor RT for measuring the temperature TDET of the lithium ion battery B, and in this embodiment, the temperature measuring thermistor RT is an NTC (Negative Temperature Coefficient) thermistor. That is, it has a characteristic that the resistance value decreases as the temperature increases and increases as the temperature decreases. In contrast, a PTC (Positive Temperature Coefficient) thermistor may be used, which has a characteristic that the resistance value increases as the temperature increases and decreases as the temperature decreases.

[0018] In addition, the upper limit temperature of the lithium ion battery B allowed during charging is defined as the allowable upper limit temperature TH, and the lower limit temperature of the lithium ion battery B allowed during charging is defined as the allowable lower limit temperature TL. It is then determined and monitored whether the temperature TDET of the lithium ion battery B during charging is equal to or higher than the allowable lower limit temperature TL and equal to or lower than the allowable upper limit temperature TH.

[0019] Furthermore, when the temperature TDET of the lithium ion battery B is the upper limit temperature TH, the resistance value that the temperature measuring thermistor RT should exhibit is defined as the upper limit temperature resistance value RH. Similarly, when the temperature TDET of the lithium ion battery B is the lower limit temperature TL, the resistance value that the temperature measuring thermistor RT should exhibit is defined as the lower limit temperature resistance value RL.

[0020] The charging temperature determination circuit 1 mainly includes a plurality of resistors (thermistors) 21 to 24, a first comparator (upper limit temperature comparison section) 3, a second comparator (lower limit temperature comparison section) 4, and an AND circuit (determination output section) 5.

[0021] The first comparator 3 is a comparator that compares the resistance value of the temperature measurement thermistor RT while the lithium ion battery B is being charged (hereinafter referred to as "charging resistance value RC") with the upper limit temperature resistance value RH. Similarly, the second comparator 4 is a comparator that compares the charging resistance value RC with the lower limit temperature resistance value RL.

[0022] In this embodiment, the charging resistance value RC is compared with the upper limit temperature resistance value RH, and the charging resistance value RC is compared with the lower limit temperature resistance value RL as voltages. That is, a first resistor 21 is arranged in series with the temperature measurement thermistor RT, and a second resistor 22, a third resistor 23, and a fourth resistor 24 are arranged in series in parallel with the temperature measurement thermistor RT and the first resistor 21. A reference voltage Vref is applied to both ends of the temperature measurement thermistor RT and the first resistor 21 arranged in series, and to both ends of the second resistor 22, the third resistor 23, and the fourth resistor 24 arranged in series.

[0023] As a result, a voltage value corresponding to the charging resistance value RC (hereinafter referred to as "charging thermistor voltage VC") is input to the "+" terminal (non-inverting input terminal) of the first comparator 3 and the "-" terminal (inverting input terminal) of the second comparator 4. A voltage value corresponding to the upper limit temperature resistance value RH (hereinafter referred to as "upper limit temperature voltage VH") is input to the "-" terminal of the first comparator 3. Similarly, a voltage value corresponding to the lower limit temperature resistance value RL (hereinafter referred to as "lower limit temperature voltage VL") is input to the "+" terminal of the second comparator 4. In other words, the size, resistance value and arrangement position of each resistor 21 to 24 are set according to the RT characteristics of the temperature measurement thermistor RT so that the charging thermistor voltage VC, the upper limit temperature voltage VH and the lower limit temperature voltage VL are input to the comparators 3 and 4.

[0024] The first comparator 3 compares the charging thermistor voltage VC with the upper limit temperature voltage VH, and if the charging thermistor voltage VC is greater than the upper limit temperature voltage VH, that is, if the temperature TDET of the lithium ion battery B being charged is lower than the allowable upper limit temperature TH, it outputs an output voltage of "H" to the B input terminal INB of the AND circuit 5. Conversely, if the charging thermistor voltage VC is smaller than the upper limit temperature voltage VH, that is, if the temperature TDET of the lithium ion battery B being charged is higher than the allowable upper limit temperature TH, it outputs an output voltage of "L" to the B input terminal INB of the AND circuit 5.

[0025] Similarly, the second comparator 4 compares the charging thermistor voltage VC with the lower limit temperature voltage VL, and if the charging thermistor voltage VC is smaller than the lower limit temperature voltage VL, that is, if the temperature TDET of the lithium ion battery B being charged is higher than the allowable lower limit temperature TL, it outputs an output voltage of "H" to the A input terminal INA of the AND circuit 5. Conversely, if the charging thermistor voltage VC is larger than the lower limit temperature voltage VL, that is, if the temperature TDET of the lithium ion battery B being charged is lower than the allowable lower limit temperature TL, it outputs an output voltage of "L" to the A input terminal INA of the AND circuit 5.

[0026] The AND circuit 5 is a logical AND circuit that judges whether the temperature TDET of the lithium ion battery B during charging is appropriate or not based on the comparison result by the first comparator 3 and the comparison result by the second comparator 4, and outputs the judgment result. That is, when the voltage input to the A input terminal INA is "H" and the voltage input to the B input terminal INB is "H", the temperature TDET of the lithium ion battery B during charging is equal to or higher than the allowable lower limit temperature TL and equal to or lower than the allowable upper limit temperature TH, and outputs the within-allowable temperature signal "HI". On the other hand, when either the voltage input to the A input terminal INA or the voltage input to the B input terminal INB is "L", the temperature TDET of the lithium ion battery B during charging is lower than the allowable lower limit temperature TL or higher than the allowable upper limit temperature TH, and outputs the outside-allowable temperature signal "LO".

[0027] The charging temperature determination circuit 1 configured as above compares the charging resistance value RC (charging thermistor voltage VC) of the temperature measurement thermistor RT while the lithium ion battery B is being charged with the upper limit temperature resistance value RH (upper limit temperature voltage VH) that this temperature measurement thermistor RT should indicate at the upper limit temperature TH, and determines whether or not the temperature TDET of the lithium ion battery B while being charged exceeds the upper limit, and outputs the result. In other words, the temperature measurement thermistor RT that actually measures the temperature TDET of the lithium ion battery B while being charged determines whether the temperature TDET is appropriate using the upper limit temperature resistance value RH (upper limit temperature voltage VH) that should be indicated at the upper limit temperature TH, so that it is possible to make an appropriate determination according to the RT characteristics of the temperature measurement thermistor RT arranged in the lithium ion battery B.

[0028] Similarly, the temperature measuring thermistor RT is compared with the resistance value RC (thermistor voltage VC) during charging of the lithium ion battery B and the lower limit temperature resistance value RL (lower limit temperature voltage VL) that the temperature measuring thermistor RT should indicate at the allowable lower limit temperature TL to determine whether the temperature TDET of the lithium ion battery B during charging exceeds (falls below) the allowable lower limit, and outputs the result. In other words, the temperature measuring thermistor RT, which actually measures the temperature TDET of the lithium ion battery B during charging, determines whether the temperature TDET is appropriate using the lower limit temperature resistance value RL (lower limit temperature voltage VL) that the temperature measuring thermistor RT should indicate at the allowable lower limit temperature TL, so that an appropriate determination can be made according to the RT characteristics of the temperature measuring thermistor RT provided in the lithium ion battery B.

[0029] Then, by having a charge management IC or the like manage charging (continue or stop charging) based on the judgment result / output of such a charging temperature judgment circuit 1, it becomes unnecessary to provide (manufacture) a different charge management IC or the like for each lithium ion battery B having a different temperature measurement thermistor RT. Here, this charging temperature judgment circuit 1 may be incorporated into the charge management IC or the like, or may be externally attached (post-installed) to the charge management IC or lithium ion battery B.

[0030] Incidentally, the upper limit temperature resistance value RH (upper limit temperature voltage VH) to be compared by the first comparator 3 and the lower limit temperature resistance value RL (lower limit temperature voltage VL) to be compared by the second comparator 4 may be made changeable / adjustable. That is, each of the resistors 21 to 24 is made a variable resistor, and the upper limit temperature voltage VH input to the first comparator 3 and the lower limit temperature voltage VL input to the second comparator 4 can be made changeable / adjustable.

[0031] Then, the resistance value of each of resistors 21-24 is changed / adjusted according to the RT characteristics of the temperature-measuring thermistor RT arranged in the lithium-ion battery B, so that the upper limit temperature voltage VH that this temperature-measuring thermistor RT should exhibit at the upper limit temperature TH and the lower limit temperature voltage VL that it should exhibit at the lower limit temperature TL are input to the comparators 3, 4, respectively. This makes it possible for one charging temperature determination circuit 1 to handle a plurality of temperature-measuring thermistors RT with different RT characteristics.

[0032] Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if the design is changed within the scope of the present invention, it is included in the present invention. For example, in the above embodiment, it is determined and monitored whether the temperature TDET of the lithium ion battery B during charging is equal to or higher than the allowable lower limit temperature TL and equal to or lower than the allowable upper limit temperature TH, but it may be determined and monitored only whether the temperature is equal to or lower than the allowable upper limit temperature TH depending on the characteristics and performance of the lithium ion battery B and the charging environment. Also, although the case where the storage battery is a lithium ion battery B has been described, it is of course possible to use other storage batteries (for example, a lead storage battery).

[0033] 1 Charging temperature determination circuit 21 The First Resistance 22 The Second Resistance 23 The Third Resistance 24 The Fourth Resistance 3 First comparator (upper limit temperature comparison section) 4 Second comparator (lower limit temperature comparison section) 5 AND circuit (judgment output section) B Lithium-ion battery (storage battery) RT Temperature measurement thermistor TH Maximum allowable temperature TL Lower limit temperature TDET Temperature during charging

Claims

1. a thermistor for measuring temperature is provided in the storage battery, and an upper limit temperature of the storage battery that is allowed during charging is defined as an allowable upper limit temperature; an upper limit temperature comparison unit that compares a resistance value of the temperature measurement thermistor while the storage battery is being charged with a resistance value indicated by the temperature measurement thermistor at the allowable upper limit temperature; a determination output unit that determines whether the temperature during charging of the storage battery is appropriate based on a comparison result by the upper limit temperature comparison unit, and outputs the result; A charging temperature determination circuit comprising:

2. a lower limit temperature of the storage battery that is allowed during charging is set as an allowable lower limit temperature; a lower limit temperature comparison unit that compares a resistance value of the temperature measurement thermistor while the storage battery is being charged with a resistance value indicated by the temperature measurement thermistor at the allowable lower limit temperature, the determination output unit determines whether the temperature during charging of the storage battery is appropriate based on a comparison result by the upper limit temperature comparison unit and a comparison result by the lower limit temperature comparison unit, and outputs the result.

2. The charging temperature determination circuit according to claim 1,

3. a resistance value indicated by the temperature measuring thermistor at the allowable upper limit temperature to be compared by the upper limit temperature comparing unit and a resistance value indicated by the temperature measuring thermistor at the allowable lower limit temperature to be compared by the lower limit temperature comparing unit are changeable; 3. The charging temperature determination circuit according to claim 2.

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