JPH09311147A - Charge / discharge current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging and discharging current measuring apparatus which has a simplified structure and measures electric current at high measurement precision. SOLUTION: This charging and discharging current measuring apparatus comprises a current detection resistor 2 to generate slight voltage proportional to the charging and discharging current, a slight voltage amplifying means 3 to amplify the slight voltage generated by the current detection resistor 2, and an input raising means 4 to previously raise the input of the slight voltage amplifying means 3. The apparatus is driven in a way in which slight voltage generated by the current detection resistor 2 is previously raised by the slight voltage amplifying means 3 and at the same time the output voltage obtained by amplifying the slight voltage is lowered corresponding to the increase of the charging and discharging current and the output voltage is increased following the increase of the discharging current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current measuring device for charging / discharging current of a secondary battery.

[0002]

2. Description of the Related Art In recent years, a battery pack in which a plurality of secondary batteries are connected and housed in a housing has been widely used as a power source for portable electronic equipment such as a notebook computer. The battery pack has a function of measuring the battery capacity in order to display a standard of the usable time of a device that supplies power. Furthermore, in lithium ion secondary batteries, which have grown remarkably recently, it is necessary to accurately measure the charge / discharge current and measure the battery capacity in order to accurately control the charge / discharge state. Usually, for the measurement of charge / discharge current, a resistor having a minute resistance value is arranged in the charge / discharge path for supplying power to the equipment, and minute voltage amplification means for charging current measurement and discharge current measurement are respectively provided, A general method is to measure the charging / discharging current flowing through each of them by each minute voltage amplifying means.

A conventional charge / discharge current measuring device will be described below with reference to the drawings. FIG. 7 is a diagram showing a configuration of a conventional charge / discharge current measuring device. In FIG. 7, 1 is a secondary battery, 2 is a current detection resistor, and a resistor having a minute resistance value is connected to the negative electrode of the secondary battery 1. Reference numeral 3 denotes a charging current minute voltage amplifying means, which includes an operational amplifier 31 and a transistor 3 which receive the minute voltage generated across the current detecting resistor 2 as an input.
2, a current mirror circuit including a transistor 34, a transistor 35, a transistor 36, and a resistor 33, and a predetermined reference power source V1. Reference numeral 4 denotes a discharge current minute voltage amplifying means, which is similar to the charging current minute voltage measuring means 3 and has an operational amplifier 41 which receives a minute voltage generated across the current detecting resistor 2 as an input, a transistor 42 and a transistor 44. Transistor 45, transistor 46,
It is composed of a current mirror circuit including a resistor 43 and a predetermined reference power source V1. Reference numeral 9 is a charging / discharging state detecting means and a comparator 51 for comparing the outputs of the resistors 33 and 43 of the output parts of the operational amplifier 31 and the operational amplifier 41 and the pull-up resistor 5.
2 and a reference power source V1. 6 is an output means. Reference numerals 7 and 8 denote input resistances of the operational amplifier 31 and the operational amplifier 41.

Next, the operation of the conventional charging / discharging current measuring device having the above structure will be described. First, when the charging current flows through the secondary battery 1, the charging current is converted into a minute voltage by the current detection resistor 2, and the negative feedback operation of the operational amplifier 31 using this as the input causes the current detection resistor 2 and the input resistor 8 to have a negative feedback operation. A minute current proportional to the charging current determined by the ratio is output to the output means 6 as the collector current of the transistor 36. Further, the charging / discharging state detecting means 5 compares the outputs of the resistors 33 and 43 to obtain a low output in the charging state. Similarly, when a discharge current flows through the secondary battery 1, a minute current proportional to the discharge current determined by the ratio of the current detection resistor 2 and the input resistor 7 is output to the output means 6 as the collector current of the transistor 46. Further, the charging / discharging state detecting means 5 compares the outputs of the resistors 33 and 43, and a high output is obtained in the discharging state. Therefore, the absolute value of the current value is obtained from the output value of the output means 6, and the charge / discharge state detection means 9 determines whether the current is the charge current or the discharge current.

[0005]

However, in the above-mentioned conventional structure, the minute voltage amplifying means is required for measuring the charging current and the discharging current, and the output from each minute voltage amplifying means is the charging current or the discharging current. There is a problem that a circuit configuration becomes large because a charging / discharging state detecting means indicating that is required. Further, the measurement accuracy of the charge / discharge current is mainly determined by the offset voltage of the operational amplifier and the ratio of the current detection resistance and the input resistance. There has been a problem that the tolerance of each circuit element of the current detecting resistor and each of the operational amplifiers constituting the minute voltage amplifying means affects the accuracy of current measurement.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a charging / discharging current measuring device which measures the charging / discharging current with a simple structure and has a good current measurement accuracy.

[0007]

In order to achieve the above object, a charging / discharging current measuring apparatus of the present invention comprises a current detecting resistor for generating a minute voltage proportional to the charging / discharging current, and a minute voltage generated by the current detecting resistor. For amplifying the input voltage, the input voltage raising means for raising the input of the minute voltage amplifying means in advance, the first switch for short-circuiting the output of the current detection resistor, and the specified current for the minute voltage amplifying means. It comprises a correction means having a second switch for inputting a considerable input, an output means for outputting the output signal of the minute voltage amplification means, and a storage means for storing the output of the output means.

In the charging / discharging current measuring device of the present invention, by raising the input of the minute voltage amplifying means, the charging current and the discharging current can be measured by one operational amplifier. Further, it is possible to discriminate the charging current or the discharging current from the value of the output of the operational amplifier, the charging / discharging state detecting means is not required, and the charging / discharging current can be measured with a simple configuration.

Further, the outputs when the inputs corresponding to two or more kinds of specified currents are input to the minute voltage amplifying means are stored, and the charging / discharging corresponding to the output of the minute voltage amplifying means is performed by the linear correction connecting these outputs. By determining the current value, the charge / discharge current can be measured accurately.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a first embodiment of a charging / discharging current measuring device of the present invention. FIG.
In FIG. 1, 1 is a secondary battery, 2 is a current detection resistor, and a resistor having a minute resistance value is connected to the negative electrode of the secondary battery 1. Reference numeral 3 denotes a minute voltage amplifying means, which receives the minute voltage generated across the current detection resistor 2 as an input, an input resistor 32 of the operational amplifier 31, a resistor 33 and a transistor 34, a transistor 36, a transistor 37, a transistor 38, and a resistor. Three
It is composed of a current mirror circuit composed of 5 and a predetermined reference power source V1. Reference numeral 4 denotes a reference current source V1 for raising the input voltage to the operational amplifier 31 so that the output of the operational amplifier 31 can be output even if no current flows through the current detection resistor 2 by an input raising means. It consists of and. Reference numeral 5 is a correction means, which is a switch 51 and a switch 5.
2. A switch 53, a resistor 54, and a predetermined reference voltage V1 divided by the resistor 55. Reference numeral 6 is an output means, which is composed of a resistive load. Reference numeral 7 is a storage means for storing the output of the output means 6.

The operation of the charging / discharging current measuring device configured as described above will be described. Even when the charging current or the discharging current does not flow in the secondary battery 1, the potential of the non-inverting input terminal of the operational amplifier 31 rises due to the constant current source 41 input to the non-inverting input terminal of the operational amplifier 31.
The transistor 34 is operated, and the negative feedback operation of the operational amplifier 31 outputs it to the output means 6 through the current mirror circuit of the minute voltage amplification means 3.

Since the charging current flows here, the potential of the non-inverting input terminal of the operational amplifier 31 decreases, and the output amount of the output means 6 decreases compared to when the charging / discharging current does not flow. On the contrary, since the discharge current flows, the output amount of the output means 6 is increased as compared to when the charging / discharging current does not flow. At this time, the correction means 5 for measuring the charge / discharge current turns on the switch 51, turns off the switch 52, and turns off the switch 53. In this way, the output of the specified amount of the output means 6 when the charging / discharging current is not flowing is used as a reference amount, and the output device 6 outputs an amount reduced from the reference amount by an amount proportional to the charging current. An amount increased from the reference amount by an amount proportional to is output from the output means 6.

Further, here, the switch 51 of the correction means 5
By turning off the switch 52, turning on the switch 52, and turning off the switch 53, the voltage generated in the minute resistance of the current detection resistor 2 is short-circuited, and the state when the charging / discharging current does not flow in the operational amplifier 31 is changed. The output of the output means 6 at this time is stored in the storage means 7. Also,
By turning off the switch 51, turning off the switch 52, and turning on the switch 53 of the correction means 5, a voltage corresponding to a predetermined specified discharge current composed of the resistor 54, the resistor 55, and the reference power source V1 is obtained. Entered in.

For example, if the specified discharge current is 4 A and the current detection resistor 2 is 20 mΩ, 80 mV is constituted by the resistor 54, the resistor 55, and the reference power source V1. The output of the output means 6 at this time is stored in the storage means 7. In this way, the switch 52 of the correction unit 5 is turned on by the correction unit 5 and the storage unit 7 and the output of the output unit 6 when the charging / discharging current is not flowing is stored in the storage unit 7, and the switch 53 of the correction unit 5 is stored. The storage means 7 stores the output of the output means 6 when the specified discharge current is turned on. By determining the value of the charging / discharging current corresponding to the output of the output means 6 with the straight line connecting these two points, the influence of the offset voltage of the operational amplifier 31 and the element variation such as the minute resistance and the input resistance of the current detection means is eliminated. You can If this correction is periodically performed, the influence of the temperature characteristics of the element on the temperature change can be eliminated, and accurate current measurement can be performed.

FIG. 2 shows the charge / discharge current value corresponding to the output of the output means 6. In the correction means 5,
The output of the output means 6 when the switch 52 is turned on and the current is zero is 2V, and the output of the output means 6 when the switch 53 is turned on and the discharge current 4A is 4V is stored in the storage means 7, and a straight line connecting these two points is shown. Obtained as in 2. Here, if the output of the output means 6 is 3V when the switch 51 is on, it can be determined from the straight line in FIG. 2 that the discharge current is 2A.

As described above, according to the charging / discharging current measuring device shown in this embodiment, the current detecting means 2 for converting the charging / discharging current into a minute voltage, and the minute voltage generated at both ends of the current detecting resistor 2. Operational amplifier 31 and operational amplifier 3 which input
1 input resistance 32, resistance 33 and transistor 34, transistor 36, transistor 37, transistor 38,
A minute voltage amplifying means 3 including a current mirror circuit including a resistor 35 and a predetermined reference power source V1, and a current detecting resistor 2
Constant current source 4 so that output is performed even if no current is flowing through
Input raising means 4 consisting of 1 and a predetermined reference power source V1
And a correction unit 5 including a switch 51, a switch 52, a switch 53, a resistor 54, and a predetermined reference voltage V1 divided by a resistor 55, an output unit 6, and a storage unit 7 for storing the output of the output unit 6. By providing the above, the charge current and the discharge current can be measured by one operational amplifier, and the charge current or the discharge current can be discriminated from the output value of the operational amplifier. Further, the charging / discharging state detecting means is not required, the charging / discharging current can be measured with a simple configuration, and the device with high current measurement accuracy can be obtained by periodically correcting.

(Second Embodiment) A second embodiment of the charge / discharge current measuring apparatus according to the present invention will be described below with reference to the drawings. FIG. 3 is a circuit diagram showing the second embodiment. In FIG. 3, 5 is a correction means, which is composed of a switch 51, a switch 53, a switch 56, a switch 57, a resistor 54, a resistor 55, a resistor 58, and a predetermined reference voltage V1 divided by the resistor 59. . Since other configurations are the same as those in FIG. 1, the same parts are designated by the same reference numerals, and detailed description thereof will be omitted.

The operation of the second embodiment constructed as above will be described. In the correction of the correction means 5 in the first embodiment, instead of storing the output when no current is flowing in the storage means 7, the switch 51 of the correction means 5 is turned off and the switch 53 is set as the charging current side point. By turning off the switch, turning off the switch 56 and turning on the switch 57, for example, when a certain specified charging current is 3 A and the resistance of the current detection means 2 is 20 mΩ, 60 mV is the specified charging composed of the resistor 58, the resistor 59 and the reference power source V1 The voltage corresponding to the current is input, and the output of the output means 6 at this time is stored in the storage means 7. Therefore, the value of the charging / discharging current corresponding to the output of the output means 6 is determined by the straight line connecting the two points of the output when the switch 53 is turned on and the output when the switch 57 is turned on. FIG. 4 shows the values of the charging / discharging current corresponding to the output of the output means 6. In FIG. 4, the output of the output means 6 is 4V at the discharge current 4A when the switch 53 is turned on in the correction means 5, and the charging current 3A when the switch 52 is turned on.
The output of the output means 6 at 0.5 V is stored in the storage means 7, and a straight line connecting these two points is obtained as shown in FIG. Here, if the output of the output means 6 is 1 V when the switch 51 is on, it can be determined from the straight line in FIG. 4 that the charging current is 2 A.

As described above, the correction means 5 is switched to the switch 51,
Switch 53, switch 56, switch 57 and resistor 5
4, a resistor 55, a resistor 58, and a resistor 59, which are divided by a predetermined reference voltage V1 and store the output of a certain specified point on the discharge current side and the output of a certain specified point on the charge current side, The device can measure the charge / discharge current with a simple configuration.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a circuit diagram showing a third embodiment of the present invention. In FIG. 5, reference numeral 3 denotes a minute voltage amplifying means, which receives an minute voltage generated across the current detection resistor 2 as an input, an input resistor 32 of the operational amplifier 31, a resistor 33 and a transistor 34, a transistor 36, a transistor 37, The current mirror circuit includes a transistor 38, a transistor 39, and a resistor 35, and a predetermined reference power source V1. Reference numeral 5 is a correction means, which is a switch 51, a switch 52, a switch 53, a switch 56, a switch 57 and a resistor 54, a resistor 55 and a resistor 5.
8 and a predetermined reference voltage V1 divided by the resistor 59. Reference numeral 6 is an output means, and a comparator 61 and a capacitor 62 for charging the output current of the minute voltage amplification means 3 with the input of the comparator 61.
And a transistor 67 for discharging the capacitor 62,
The current mirror circuit including the transistor 68 and the reference voltage of the comparator 61 are used as the resistor 63, the resistor 64, the resistor 65, a predetermined reference power source V1, and the comparator 61 according to the output of the comparator 61.
The transistor 66 for changing the reference voltage of, the transistor 69 for switching the charging or discharging of the capacitor 62 according to the output of the comparator 61, and the inverter 610. Since other configurations are basically the same as those in FIG. 1, the same parts are designated by the same reference numerals, and detailed description thereof will be omitted.

The operation of the charging / discharging current measuring device configured as described above will be described. In the output of the output means 6 in the first and second embodiments, an oscillating circuit is used instead of the resistance load, and the charging / discharging current value is determined by the value of the pulse frequency. A minute current proportional to the charging / discharging current charges the capacitor 62 as the collector current of the transistor 39 of the minute voltage amplifying means 3. When the voltage of the capacitor 62 becomes larger than the divided voltage of the combined resistance of the resistors 63, 64 and 65, the output of the comparator 61 is inverted, turning on the transistor 66 and turning off the transistor 69. At this time, a current twice as much as the collector current of the transistor 39 flows as a collector current of the transistor 68 from the current mirror circuit including the transistors 67 and 68, so that the capacitor 62 is discharged with the same magnitude as the charging current. When the voltage of the capacitor 62 becomes smaller than the divided voltage of the resistors 63 and 64, the output of the comparator 61 is inverted again, turning off the transistor 66,
The transistor 69 is turned on, and the capacitor 62 is charged again. After that, the same operation is repeated to output the pulse frequency according to the value of the charge / discharge current.

In the pulse frequency system as the output means, the measurement resolution of the charging / discharging current is improved by increasing the pulse frequency as compared with the resistance load, but the comparator 61 delays the time until the output is reversed after the input is reversed. Has the operating characteristic that occurs. Since this delay time has a constant value regardless of the pulse frequency, the higher the pulse frequency, the worse the linearity in the relationship between the charge and discharge current values corresponding to the pulse frequency. Therefore, the correction means 5 of the second embodiment of the second
For correction at points, the value of the charging / discharging current corresponding to the output of the output means 6 is determined by the straight line connecting the three points.

First, the switch 51 of the correction means 5 is turned off,
Switch 52 on, switch 53 off, switch 5
By turning on 6 and turning off the switch 57, the voltage generated in the minute resistance of the current detection resistor 2 is short-circuited, and the output when the charging / discharging current is not flowing is output from the output means 6 as the pulse frequency. The frequency is stored in the storage means 7. Next, the switch 51 of the correction means 5
Is turned off, the switch 52 is turned off, the switch 53 is turned on, the switch 56 is turned on, and the switch 57 is turned off, the output of the output means 6 when a certain specified discharge current flows is output from the output means 6 as a pulse frequency. The frequency is stored in the storage means 7.

Further, by turning on the switch 51, turning off the switch 52, turning off the switch 53, turning off the switch 56 and turning on the switch 57 of the correction means 5, the output means 6 of the output means 6 when a certain specified charging current flows. The output is output as the pulse frequency from the output means 6, and this frequency is stored in the storage means 7. Therefore, by determining the value of the charging / discharging current corresponding to the output frequency of the output means 6 by the straight line connecting the three points of the output of the output means 6 when the switch 52 or the switch 53 or the switch 57 is turned on, the pulse frequency as the output means Even when the linearity of the output with respect to the input due to the influence of the delay time of the comparator is poor as in the method of converting to, the charging and discharging current can be measured with high measurement accuracy.
At this time, the correction means 5 for measuring the charge / discharge current is the switch 5
1 on, switch 52 off, switch 53 off,
The switch 56 is turned on and the switch 57 is turned off.

FIG. 6 shows the charge / discharge current value corresponding to the output frequency of the output means 6. Correction means 5 in FIG.
The output frequency of the output means 6 when the charge / discharge current is zero when the switch 52 is turned on is 50 Hz, and the output frequency of the output means 6 when the discharge current is 4 A when the switch 53 is turned on is 90 H.
z, the output frequency of the output means 6 at the charging current 3A with the switch 57 turned on is 10 Hz, and the straight line connecting these three points is obtained as shown in FIG. When the output frequency of the output means 6 is 60 Hz when the switch 51 is on and the switch 56 is on, it can be determined from the straight line in FIG. 6 that the discharge current is 1 A.

As described above, even in the case where the output circuit is the oscillation circuit and the charge / discharge current value is determined by the value of the pulse frequency, the correction means 5 includes the switch 51, the switch 52, the switch 53, the switch 56, the switch 57 and the resistor 54. Reference voltage V1 divided by the resistors 55, 58, and 59
And stores the output frequency at which the charging / discharging current is zero, the output frequency at a certain specified point on the discharge current side, and the output frequency at a certain specified point on the charge current side.
By determining the value of the charging / discharging current corresponding to the output frequency of the output means 6 with a straight line connecting the points, a device capable of measuring the charging / discharging current with good measurement accuracy can be obtained even by the method of converting the charging / discharging current into the pulse frequency by the output means.

In the present embodiment, the output of the minute voltage amplifying means is reduced according to the increase of the charging current, and the output of the minute voltage amplifying means is increased according to the increase of the discharging current. The configuration of the input terminal of the operational amplifier may be inverted so that the output of the current amplification means is increased as the charging current increases and the output of the current amplification means is decreased as the discharging current increases. Further, in the third embodiment, the charging corresponding to the output is made by a straight line connecting the output at the point where no current flows, the output at the specified point with the charging current and the output at the specified point with the discharging current. Although the value of the discharge current is determined, the value of the charge / discharge current corresponding to the output may be determined by a straight line connecting the outputs of the correction means at a plurality of points.

[0029]

As described above, the charging / discharging current measuring device of the present invention can measure the charging / discharging current with a simple structure and can realize a device with high current measurement accuracy. Further, it is possible to realize an apparatus capable of measuring charge / discharge current with high measurement accuracy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a value of a charging / discharging current corresponding to an output of an output means in the circuit.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a value of a charging / discharging current corresponding to an output of an output means in the same circuit.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing a value of a charging / discharging current corresponding to an output of an output means in the circuit.

FIG. 7 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 1 Secondary Battery 2 Current Detection Resistor 3 Micro Voltage Amplifying Means 4 Input Raising Means 5 Correction Means 6 Output Means 7 Storage Means

Claims (6)

[Claims] 1. A current detection resistor located in a charge / discharge path of a battery for generating a minute voltage proportional to a charge / discharge current, a minute voltage amplifying means for amplifying a minute voltage generated by the current detecting resistance, and an output means. In the charging / discharging current measuring device, the minute voltage amplifying means preliminarily raises the minute voltage generated by the current detection resistor, and an output voltage obtained by amplifying the minute voltage according to an increase in charging current. The charging / discharging current measuring device is characterized in that it operates so as to decrease the output voltage and increase the output voltage in accordance with the increase in the discharging current. 2. The charging / discharging current measuring device further includes a first switch for short-circuiting a minute voltage generated by the current detecting resistor and an input voltage corresponding to a prescribed current preset in the minute voltage amplifying means. It has a correction means having a second switch for inputting, and a storage means for storing the output of the minute voltage amplification means, wherein the storage means stores the minute voltage amplification means when the first switch is turned on. The output and the output of the minute voltage amplifying means when the second switch is turned on are stored, and the value of the charging / discharging current linearly corresponding to the output of the minute voltage amplifying means by the two stored outputs. Charge / discharge current measuring device for determining. 3. The charging / discharging current measuring device includes a correcting means for inputting an input voltage corresponding to a predetermined specified current to the minute voltage amplifying means, and a storing means for storing an output of the minute voltage amplifying means. The correction means includes a third switch and a fourth switch for inputting two different types of input voltages corresponding to the specified currents to the minute voltage amplification means, and the third switch is turned on. The output of the minute voltage amplifying means and the output of the minute voltage amplifying means when the fourth switch is turned on are stored, and the two stored outputs linearly output the minute voltage amplifying means. The charging / discharging current measuring device according to claim 1, wherein the charging / discharging current value corresponding to is determined. 4. The output voltage of the small voltage amplifying means is a voltage generated in a resistive load, and the value of the charging / discharging current corresponding to the voltage is determined. Charge / discharge current measuring device. 5. The storage means comprises a plurality of switches for inputting input voltages corresponding to different predetermined currents to the minute voltage amplification means, and the minute switches when the first switch is turned on. The output of the voltage amplifying means and the respective outputs of the minute voltage amplifying means when the plurality of switches are sequentially turned on are stored, and the output of the minute voltage amplifying means is formed by a straight line connecting the outputs of these plural points. The charging / discharging current measuring device according to claim 2, wherein the charging / discharging current value corresponding to is determined. 6. The output means of the minute voltage amplifying means converts the minute voltage generated by the current detecting resistor into a frequency and determines the value of the charging / discharging current corresponding to the frequency. The charging / discharging current measuring device described.