JPH1070846A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of measurement of the temperature of a battery being charged by correcting inside a battery charger a voltage error caused by the contact resistance between the terminals being charged, in a charger for charging a battery pack with a built-in secondary battery and a thermister. SOLUTION: A contact resistance occurring between negative pole terminals 6a and 6b when a battery pack is connected by current detecting means 12 and contact resistance measuring means 13 is measured, and a voltage induced when a charging current is flowing is calculated as a correction value by correction value determining means 14. The correction value stated above is subtracted from a divided voltage generated between a voltage dividing resistor 8 and a thermister 5, a corrected voltage is calculated by voltage correcting means 15. A reference voltage output from the corrected voltage and reference voltage generating means 9 are compared with each other by comparison mean 10, and the temperature of the battery is measured thereby enhancing the measuring accuracy of the temperature of a battery being charged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger for measuring a battery temperature with a thermistor incorporated in a battery pack and stopping charging or controlling a charging current based on the measurement result.

[0002]

2. Description of the Related Art In recent years, a charging device measures the temperature of a battery pack containing a secondary battery and a thermistor in order to ensure the safety of the battery, and when the battery temperature becomes abnormally high or low. In addition, control is performed to stop charging or increase / decrease the charging current.

A conventional charging device will be described below with reference to FIGS. FIG. 3 is a block diagram showing a conventional charging device for performing battery temperature measurement. In FIG. 3, reference numeral 1 denotes a DC power supply unit which outputs a charging current, and a charging switch 2 connected to a positive output of the DC power supply unit 1 controls a charging current output. Reference numerals 3a and 3b denote device-side and battery-side positive terminals and output terminals for charging current, respectively.
6b, a thermistor 5, and a battery-side temperature detection terminal 7b. The thermistor 5 provided in the battery pack 4 has one as a negative electrode of the secondary battery and the other as a battery-side temperature detection terminal 7.
b. Reference numerals 6a and 6b denote output terminals serving as feedback sections for charging current, respectively, which are device-side and battery-side negative terminals. Reference numerals 7a and 7b denote device-side and battery-side temperature detection terminals, respectively, and 8 denotes a voltage-dividing resistor.
1 is located. Reference numeral 9 denotes a reference voltage generator which outputs a reference voltage. Reference numeral 10 denotes a comparing means, which is a temperature detecting terminal 7a.
The divided voltage generated during the period 7b and the reference voltage output from the reference voltage generating means 9 are used as input means to output a comparison result. The control unit 11 receives a signal of the comparison means 10 and a battery voltage and a charging current (not shown) required for the charging control, outputs a corresponding voltage to the charging switch 2, and outputs a specified voltage to the voltage dividing resistor 8. Is output.

The operation of the conventional charging device having the above-described configuration will be described below with reference to the flowchart of FIG. 4 when the battery temperature becomes abnormally low.

[0005] First, when the battery pack 4 is connected to the charging device, the charging device supplies charging current from the DC power supply unit 1, and supplies the charging current to the battery pack 4 via the charging switch 2 in the ON state and the positive terminals 3 a and 3 b. Start charging. Battery pack 4
Is fed back to the DC power supply unit 1 via the negative terminals 6a and 6b.

During charging, a divided voltage V7 is generated between the temperature detecting terminals 7a and 7b by the voltage dividing resistor 8 and the thermistor 5. The divided voltage V7 is compared with a reference voltage V8 generated by the reference voltage generating means 9 as an input signal of the comparing means 10.

The divided voltage V7 is determined by the resistance value of the thermistor 5. When the battery temperature rises, the resistance value of the thermistor 5 decreases, and the divided voltage V7 decreases. Conversely, when the battery temperature decreases, the resistance value of the thermistor 5 increases,
The divided voltage V7 increases. Utilizing this relationship, the reference voltage V8 of the comparator is determined in advance, and this is compared with the divided voltage 7, so that the battery temperature can be measured. If the divided voltage V7 is lower than the reference voltage V8, the comparing means 10
Outputs the signal to the control unit 11. In response to this, the control unit 11 determines that the battery temperature is normal, and outputs a signal to continue charging, so that the charge switch 2 is kept on. During charging, the comparing means 10 periodically measures the divided voltage V7 and periodically compares the divided voltage V7 with the reference voltage V8 by the above-described series of operations.

When the divided voltage V7 exceeds the reference voltage V8, the comparing means 10 outputs a signal to the control unit 11. In response to this, the control unit 11 determines that the battery temperature is abnormally low and needs to stop charging, outputs a signal to turn off the charging switch 2, and stops charging. Even after the charging is stopped, the measurement of the divided voltage is periodically performed, and the comparison with the reference voltage is performed by the above-described series of operations.
At this time, when the divided voltage V7 falls below the reference voltage V8, the control unit 11 receiving the signal from the comparing means determines that the battery pack has returned to a temperature suitable for charging, and turns on the charging switch 2 again. A signal for setting the state is output, and charging is restarted.

[0009]

However, in the above-mentioned conventional configuration, when the temperature is detected during charging, the terminal itself is deteriorated due to long-term use, and the terminal itself is caused by dirt attached to the terminal surface. When a charging current flows due to contact resistance generated between the resistor and the negative electrode terminal, a voltage is generated between the negative electrode terminals. The above-described voltage is applied to the divided voltage input from the temperature detection terminal to the comparison means, and the measured temperature includes an error with respect to the temperature of the battery pack.

The present invention solves the above-mentioned conventional problems. A resistance component generated between negative electrodes is calculated in a charging device, and a voltage error is reduced by reducing a divided voltage generated by the resistance component. It is an object of the present invention to provide a charging device capable of canceling out and accurately detecting a temperature.

[0011]

Means for Solving the Problems To achieve the above object, a charging apparatus according to the present invention comprises a conventional charging apparatus,
When the thermistor is connected between the battery-side positive terminal and the battery-side temperature detection terminal, the contact resistance generated by the device-side positive terminal and the device-side temperature detection terminal is determined. When connected between the detection terminal, a contact resistance measuring means for measuring a contact resistance generated by the device-side negative terminal and the device-side temperature detection terminal, and an output of the contact resistance measuring means and an output of the current detecting means are input. Correction value determining means, and a voltage correcting means which receives the output of the correction value determining means as an input, wherein the output voltage of the voltage correcting means by the comparing means, the reference voltage generated by the reference voltage generating means, By calculating the resistance component generated between the terminals in the charging device, the voltage error generated by the resistance component is reduced from the measured divided voltage. Cancellation, it is possible to always accurate temperature measurements without being influenced by the contact resistance between the terminals own terminal resistance and terminal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a charging device for performing temperature measurement according to the present invention. In FIG. 1, the same or equivalent components as those in the conventional example are denoted by the same reference numerals, and the description thereof will be omitted. Only different configurations will be described. In the figure, reference numeral 12 denotes a current detecting means which is located between the DC power supply unit 1 and the device-side negative terminal 6a, and measures a charging current value. Reference numeral 13 denotes a contact resistance measuring unit which receives a divided voltage generated between the temperature detecting terminals 7a and 7b and a charging current value of the current detecting unit 12 as inputs, and connects the charging device and the battery pack 4 to the negative terminal 6a. 6b is measured. 1
Reference numeral 4 denotes a correction value determining unit which receives the contact resistance value obtained by the contact resistance measuring unit 13 and the charging current value output from the current detecting unit 12 and determines a correction value of the divided voltage. Reference numeral 15 denotes a voltage correction unit that corrects the divided voltage by inputting the divided voltage and the correction value of the correction value determining unit 14 and subtracting the correction value from the divided voltage.

The comparing means 10 of the present invention receives the output voltage of the voltage correcting means 15 and the reference voltage output from the reference voltage generating means 9 which has been previously set to an appropriate value, and inputs the comparison result to the control unit 11. Output.

The control unit 11 receives the signal of the comparison unit 10 and other battery voltages and charging currents not shown in the drawings required for the charging control and inputs them to the charging switch 2 and the contact resistance measuring unit 13 in response thereto. And outputs a specified voltage to the voltage dividing resistor 8.

The charge control when the battery temperature becomes abnormally low will be described with reference to the flowchart of FIG. 2 as an example of the charging device configured as described above. First, the battery pack 4 is charged. Connect to the device. When the battery pack 4 is connected, the control unit 11 first outputs a signal for turning off the charging switch 2, and the charging current is not supplied yet. At this time, the divided voltage V1 generated between the temperature detecting terminals 7a and 7b is measured by the contact resistance measuring means 13 and stored.

Next, the control unit 11 outputs a signal for turning on the charging switch 2 and starts supplying the charging current from the DC power supply unit 1 to the battery pack 4 via the charging switch 2 and the positive terminals 3a and 3b. The charging current is supplied to the negative terminals 6b and 6a,
The current returns to the DC power supply unit 1 via the current detecting means 12.
At this time, the divided voltage V generated at the temperature detection terminals 7a and 7b.
2 is stored in the contact resistance measuring means 13 after measurement. Further, the charging current I1 at that time is measured by the current detecting means 12 and stored in the contact resistance measuring means 13.
The contact resistance measuring means 13 uses the previously stored V1, V2, I
From 1, the contact resistance value R1 is calculated by (Equation 1).

[0018]

R1 = (V2−V1) / I1 Next, the correction value determining means 14 calculates a difference between the charging current value I2 measured again by the current detecting means 12 and the contact resistance value R1 obtained by the contact resistance measuring means 13. A correction value V3 for correcting the voltage is calculated by (Equation 2).

[0019]

V3 = R1 × I2 Then, as shown in (Equation 3), the correction voltage V5 is obtained by subtracting the correction value V3 obtained earlier from the divided voltage V4 measured again, as shown in (Equation 3).

[0020]

V5 = V4−V3 The correction voltage V5 is compared with the reference voltage V6 generated by the reference voltage generation means 9 in the comparison means 10.

The correction voltage V5 is determined by the resistance value of the thermistor 5, and when the battery temperature rises, the resistance value of the thermistor 5 decreases and the correction voltage V5 decreases. Conversely, when the battery temperature decreases, the resistance value of the thermistor 5 increases, and the correction voltage V5
Becomes larger.

Using this correlation, when the correction voltage V5 is lower than the reference voltage V6, the control section 11 determines that the battery temperature is normal, determines that the battery temperature is normal, and makes the charge switch 2 based on a signal from the comparing means 10. To output a signal for maintaining the ON state. During charging, the contact resistance measuring means 13 periodically measures the divided voltage V4, the current detecting means 12 periodically measures the charging current value I2, and the correction value determining means 14 calculates the correction value V3. The detection operation is performed regularly, and the battery temperature is constantly monitored for abnormality.

Conversely, when the correction voltage V5 exceeds the reference voltage V6, the control unit 11 determines from the signal from the comparing means 10 that the battery temperature is abnormally low, and turns off the charge switch 2. Outputs a signal to stop charging. After the charging is stopped, the charging current does not flow.
Since 3 = 0 and V5 = V4, the divided voltage V4
Is measured, and the comparing means 10 compares the correction voltage V5 = V4 with the reference voltage V6 to constantly monitor the battery temperature. When the correction voltage V5 is lower than the reference voltage V6, the control unit 11 receiving the output signal of the comparing unit 10
It is determined that the battery pack 4 has returned to a temperature suitable for charging,
A signal for turning on the charging switch 2 again is output, and charging is restarted.

In the above embodiment, the case where the thermistor 5 is connected between the battery-side negative electrode terminal 6b and the battery-side temperature detecting terminal 7b is shown. It goes without saying that the same control can be performed even when connected between the detection terminals 7b.

In the above-described embodiment, the control is performed when the correction voltage V5 exceeds the reference voltage V6 for abnormally low temperature and the battery pack 4 becomes low temperature. It goes without saying that the same control can be performed even when V5 drops and the battery pack 4 becomes hot. In addition, two or more reference voltage generating means 9 and two or more comparing means 10 are provided to control both low temperature and high temperature, or to detect a plurality of temperatures such as first low temperature and second low temperature, and perform control corresponding to the detection result. Needless to say, it is easy to do.

In the above embodiment, 9, 10, 1
Each of the means 1, 13, 14, and 15 was realized in a microcomputer.

According to the power supply device of the present embodiment,
Voltage error caused by contact resistance between terminals during charging,
First, the contact resistance measuring unit 13 measures the contact resistance value, and the correction value determining unit 14 calculates the correction value.
By measuring the battery temperature with the correction voltage obtained by subtracting the correction value from the divided voltage according to 5, the battery temperature can always be accurately measured regardless of whether the battery is being charged or not, and the appropriate Charge control can be performed.

[0028]

As described above, according to the power supply device of the present invention, the measurement error due to the voltage generated between the terminals is reduced in the charging device from the divided voltage generated by the contact resistance of the temperature detection terminal during charging. By performing the correction, it is possible to provide an excellent charging device that can always accurately measure the battery temperature without being affected by the resistance of the terminal itself and the contact resistance between the terminals.

[Brief description of the drawings]

FIG. 1 is a block diagram of a charging device of the present invention.

FIG. 2 is a flowchart showing a control operation of the charging device of the present invention.

FIG. 3 is a block diagram of a charging device showing a conventional example.

FIG. 4 is a flowchart showing a control operation of a conventional charging device.
G

[Explanation of symbols]

 Reference Signs List 1 DC power supply unit 2 Charge switch 3a Device side positive terminal 3b Battery side positive terminal 4 Battery pack 5 Thermistor 6a Device side negative terminal 6b Battery side negative terminal 7a Device side temperature detecting terminal 7b Battery side temperature detecting terminal 8 Voltage dividing resistor 9 Reference Voltage generation means 10 Comparison means 11 Control unit 12 Current detection means 13 Contact resistance measurement means 14 Correction value determination means 15 Voltage correction means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H02J 7/10 H02J 7/10 L H

Claims (1)

[Claims] 1. A DC power supply unit for supplying a charging current to a battery pack, a charging switch located on a charging path to the battery pack for controlling a charging current, and a device side located on the charging path and outputting a charging current A positive terminal, a battery-side positive terminal connected to the device-side positive terminal, a device-side negative terminal serving as a feedback section for charging current, a battery-side negative terminal connected to the device-side negative terminal, and a charging current value , A battery-side temperature detection terminal connected to a thermistor in the battery pack, a device-side temperature detection terminal connected to the battery-side temperature detection terminal, and the device-side temperature detection terminal A reference voltage generating means for generating a reference voltage and a voltage dividing resistor connected to the battery pack; a comparing means; and a control unit for receiving an output of the comparing means as an input and outputting a control signal to the charge switch, and built in the battery pack. Is A battery device that measures the battery temperature with the thermistor and stops charging of the battery pack or controls the charging current in accordance with the detected battery temperature, wherein the thermistor is connected to the battery-side positive terminal and the battery-side temperature. When connected between the detection terminal, the contact resistance generated by the device-side positive terminal and the device-side temperature detection terminal, and the thermistor between the battery-side negative terminal and the battery-side temperature detection terminal When connected, a contact resistance measuring unit for measuring a contact resistance generated by the device-side negative terminal and the device-side temperature detection terminal, and a correction using the output of the contact resistance measuring unit and the output of the current detecting unit as inputs. Value determining means, and voltage correcting means for receiving an output of the correction value determining means as input, wherein the output voltage of the voltage correcting means and the reference voltage generation by the comparing means are provided. A charging device that compares the reference voltage with a reference voltage generated by the means.