JP3193390B2 - Battery capacity display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for displaying the capacity of a battery by measuring and integrating the current of the battery, that is, the current at the time of charging or discharging, and more particularly to a battery for accurately measuring the current. The present invention relates to a capacity display device.

[0002]

2. Description of the Related Art In recent years, there has been a growing demand for battery-applied equipment incorporating a battery such as a storage battery. Under such circumstances, a function of calculating and displaying a remaining capacity of a battery has been provided to improve convenience of use. Battery-applied devices have been proposed. The block diagram shown in FIG. 7 shows an example.

[0003] FIG. 7 shows a load 2 by a discharge current from the battery 1.
Displays the remaining capacity of the battery accompanying the supply of the discharge current when the battery is driven. The discharge current is detected by the low resistance 3 and supplied to the discharge current detection circuit 10 via the amplifier 4 and the A / D converter 5. The remaining capacity of the battery 1 is calculated by the calculation and the back calculation (conversion) to the discharge current, and then integrated by the remaining capacity calculation circuit 11 to be displayed on the display circuit 8.

[0004] That is, the discharge current from the battery 1 to the load 2 is detected as a voltage by the low resistance 3, amplified by 1+ (R1 / R2) times by the amplifier 4 having the operational amplifier OP 1, and then guided to the microcomputer 6. . That is, the output voltage of the amplifier 4 is converted into a digital value by the A / D converter 5 and further detected by the discharge current detection circuit 10 by performing an inverse calculation using the previously stored gain of the amplifier 4. It is converted to a discharge current value. Then, the remaining capacity calculation circuit 11
The value obtained by subtracting the discharge amount per time from the previous remaining capacity is displayed on the display circuit 8 as the current remaining capacity.

The operational amplifier OP1 has an adjustable offset voltage, is connected to a variable resistor VR1, and the resistor R2 is composed of a variable resistor VR2 so that the gain of the amplifier 4 can be adjusted. I have.

[0006]

According to the above-described battery capacity calculation method, the resistance Rs of the low resistance 3, the fluctuation of the gain of the amplifier 4 due to the fluctuation of the resistances of the resistors R1 and R2, and the offset voltage of the operational amplifier OP1. Is a problem in the accuracy of current measurement.

FIG. 8 is a characteristic diagram showing the relationship between the discharge current and the output voltage of the amplifier 4. Line A is a resistor R3, amplifier 4
And the ideal gain when the offset voltage (input side) of the operational amplifier OP1 is 0. The gain represented by the straight line A is taken in the discharge current detecting means 11.

If the input offset voltage of the operational amplifier OP1 exists as Vos, the output voltage of the amplifier 4 when the current I flows, that is, the output voltage VA / D of the A / D converter 5, becomes VA / D = (Rs × I + Vos) × G where the resistance value Rs of the low resistance 3 and the gain G of the amplifier 4 are represented by a straight line B.

On the other hand, if the variable resistor VR2 is adjusted so that the output voltage coincides with Vs at the time of the current Is, ignoring the offset voltage Vos, a straight line C is obtained, and the gain greatly changes. In such a case, for example, when the output voltage of the operational amplifier OP1 is V1, the microcomputer 6 converts and outputs the current I1 by the straight line A, and the actual current I1
2, a large error occurs, and measurement accuracy cannot be ensured. In particular, when the load 2 increases the low resistance 3 of a motor or the like, a voltage drop occurs between the low resistance 3 and the motor, which has an adverse effect on the motor start. Since it is minute, the input offset voltage can be a factor of a large error.

On the contrary, even if the input offset voltage Vos is adjusted to 0 by the variable resistor VR1, the resistance R3,
The gain of the amplifier 4 changes due to the variation of the resistors R1 and R2, and becomes as shown by a straight line D.

Therefore, conventionally, two variable resistors VR1 and VR2 are provided, such as adjusting the offset voltage when no current is flowing through the variable resistor VR1 to 0, and further adjusting the gain by the variable resistor VR2. The configuration is complicated, and the adjustment work requires time and effort. Furthermore, as shown in FIG. 7, in the case of a single power supply that takes the circuit power of the microcomputer 6 from the battery 1 via the constant voltage circuit 7, an operational amplifier OP1 whose offset voltage can be adjusted is required. Type operational amplifiers are special and expensive.

The present invention has been made in view of the above,
It is an object of the present invention to provide a battery capacity display device capable of accurately measuring current with an inexpensive circuit configuration, and having only one adjustment unit and having few adjustment steps.

[0013]

According to the present invention, there is provided a battery capacity display apparatus comprising: a resistor for detecting a current of a battery as a voltage between both ends; an amplifying means for amplifying a voltage between both ends of the resistor; and a predetermined gain of the amplifying means. First storage means for storing the input current Is and the output voltage Vs, the adjusting means for previously adjusting and setting the output voltage of the amplifying means to Vs when the battery current is Is, and the amplifying means A conversion means for converting the output voltage of the battery into a current value of the battery using a predetermined gain stored in the first storage means, and an offset value Vo of the amplification means when the battery current is cut off. Second
Correction means for obtaining the gain of the amplification means from Is, Vs, Vo stored in the first and second storage means, and correcting the output value of the conversion means from the gain and the predetermined gain. Means, a remaining capacity calculating means for calculating the remaining capacity of the battery by integrating the corrected current value, and a display means for displaying the obtained remaining capacity.

[0014]

According to the present invention, when a battery current, that is, a charging or discharging current flows, a voltage is generated across the resistor, and this voltage is amplified by the amplifying means. The amplified voltage is led to a conversion means, where it is back calculated using a predetermined gain and converted into a current. Subsequently, the converted current is corrected to the actual current of the battery from the actual gain of the amplification means and the predetermined gain. Then, the corrected current value is integrated by the remaining capacity calculating means, and the latest remaining capacity of the battery is calculated from the integrated amount and the current remaining capacity by, for example, addition or subtraction, guided to the display means and displayed. .

[0015]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a characteristic diagram showing the relationship between the battery current and the output voltage of the amplifier 4 for explaining the operation.

In FIG. 1, a battery 1 and a load 2 such as a motor
Are connected in series via a low resistance 3 for current detection. The amplifier 4 includes an operational amplifier OP1 therein, and guides the voltage between both ends of the low resistor 3 to a non-inverting input terminal via a resistor Ro, and a variable resistor VR connected between the inverting input terminal and ground.
2 and a feedback resistor R1 is connected to the output side. This operational amplifier OP
The gain G of 1 is expressed as follows: G = (1 + R1 / R2) The resistance value Rs of the low resistance R3 is set to 10 m in consideration of the effect on the load 2 due to the voltage drop at the low resistance R3.
Ω, the voltage when a current of 2 A flows is 2
0 mV, and at this time, the output of the operational amplifier OP1 is 5 V
Then, the gain G becomes approximately 250 times, and is substantially (R1
/ R2) can be replaced with the gain G.

The microcomputer 6 has built-in A / D converters 5 to remaining capacity calculation circuit 11 and discharge SW detection circuit 14, and calculates the remaining capacity of the battery from the output voltage of the amplifier 4. I have.

The A / D converter 5 converts the output voltage of the amplifier 4 into a digital value, and the converted digital value is input to a discharge current detection circuit 10. The discharge current detection circuit 10 converts the input voltage based on the ideal gain line A shown in FIG. 2, for example, the current Iin when the taken voltage value is Vin, as follows: Iin = Vin × (Is / Vs) Is what you do. Note that Is and Vs are stored in the storage circuit 12 in advance as described later.

The storage circuit 12 stores a desired point on the ideal gain line A, that is, a current Is and its output voltage Vs. At this time, the amplifier 4 outputs the battery current Is
At this time, the variable resistor VR2 is adjusted so that the output voltage of the amplifier 4 matches Vs.

When the battery current is cut off, that is, when the discharge switch SW is turned off, the storage circuit 13 detects this state by the discharge SW detection circuit 14 and outputs the output voltage (offset value) Vo of the amplifier 4 at that time. It is to take in. As a result, the gain and offset value Vo of the amplifier 4 are as shown by a straight line B in FIG. Note that Vo =
Vos × G. Thus, accurate results are obtained only for Vs and Is, but otherwise produce errors.

The correction circuit 15 includes the discharge current detection circuit 10
The correction is performed on the current Iin converted by the equation (1). That is, since the discharge current detection circuit 10 performs an inverse calculation using the ideal gain line A as described above, the actual gain and offset value Vo of the amplifier 4 are not considered. Therefore, the correction circuit 15 performs correction based on the difference between the ideal gain and the actual gain and offset value. This correction is performed by, for example, substituting Vin = Vs · Iin / Is into the equation of the straight line B, I = (Vin−Vo) · Is / (Vs−Vo), and obtaining a relational expression between I and Iin. By leaving
It can be done only from this relational expression.

The remaining capacity calculation circuit 11 takes in the corrected current, that is, the actual current value of the battery, and integrates it for each required unit time to calculate the amount of discharge per unit time. The latest (current) remaining capacity is obtained by subtracting the calculated amount of discharge per unit time from. The display circuit 8 displays the latest remaining battery capacity in a percentage display, a bar graph, or a lighting display of a corresponding segment.

As described above, in the first embodiment, a special and expensive operational amplifier capable of adjusting an offset value is not used, and
An accurate current measurement and its display can be performed with an inexpensive circuit configuration. Further, the adjustment point is one point of VR2, and the cost can be reduced by the adjustment process.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 3, components having the same reference numerals as those in FIG. 1 perform the same functions. This embodiment is made in consideration of the case where the offset value Vo of the operational amplifier OP1 shows 0 when the discharge switch SW is off in FIG. That is, when the offset voltage of the operational amplifier OP1 is on the negative side, the output voltage becomes as shown by the straight line C in FIG. 2, and although the output voltage is actually negative, it becomes 0 V because of the single power supply. Could be. In such a case, even if the correction of the first embodiment is performed, an error occurs, and accuracy cannot be ensured. In the second embodiment, correction can be performed even when the offset voltage of the operational amplifier OP1 is on the negative side.

FIG. 3 shows the circuit diagram of FIG.
Is different. That is, the amplifier 41 constitutes an operational amplifier. The resistors R5 and R6 are connected to the non-inverting input terminal, and the other end of the resistor R2 to which the voltage across the low resistor 3 is led is connected to the inverting input terminal. Note that, as is well known, the resistance value of the resistor R5 is set to be the same as the resistance R1, and the resistance value of the resistor R6 is set to be the same as the resistance R2.

In order to achieve the object of this embodiment,
The constant voltage of the constant voltage circuit 7 is connected to the non-inverting input terminal by the resistor R3.
A bias voltage VBIAS divided by R4 is applied.
Therefore, the output voltage V with respect to the current I is (VBIAS−I ·
Rs) × G. FIG. 4 is a characteristic diagram showing a relationship between the current of the amplifier 41 and the output voltage, and a straight line A indicates an ideal gain. Note that the characteristic straight line has a negative gradient from the configuration of the operational amplifier 41.

On the other hand, if the input offset voltage of the amplifier 41 is Vos when the discharge switch SW is off, the output voltage Vo at that time is Vo = (VBIAS−Vos) × G
It is represented by Therefore, the output voltage VA / D when the current I flows is expressed as VA / D = (VBIAS−I · Rs−Vos) × G.

Here, the gain G is set by adjusting the variable resistor VR2 so that the output voltage is 5 V when the discharge switch SW is off, that is, when the discharge current is zero.
In addition, in order to always obtain a positive output voltage with respect to the measured current and enable the current measurement, VBIAS> I · Rs + Vos is set. That is, by setting the gain G as described above, the offset value Vo as shown by the straight lines C and B in FIG.
Appears in either positive or negative direction, the difference from the bias voltage VBIAS is accurately amplified, so that the error is eliminated. Also,
By setting the value of the bias voltage VBIAS to be larger than the maximum value of the current measurement + the maximum value of the offset voltage, it is possible to perform all measurements within the current range of the battery.

The discharge current from the battery is detected by the low resistance 3 as a voltage between both ends, amplified by the amplifier 41, guided to the A / D converter 5, and converted into a digital value. Then, the current is converted into a current based on the ideal gain of Vs and Is taken in advance by the discharge current detection circuit 10. The storage circuit 12 stores the above Vs and Is, and the storage circuit 13 stores the offset value Vo. Therefore, the correction circuit 15
Calculates the actual discharge current by performing the same correction as shown in the first embodiment based on the above stored contents. The corrected discharge current value is added to the discharge amount per unit time by the remaining capacity calculation circuit 11 and is subtracted to obtain the latest remaining capacity, which is then led to the display circuit 8 and displayed in% or the like. You.

As described above, in the second embodiment, in addition to the effects of the first embodiment, it is possible to always perform error-free current measurement regardless of whether the offset voltage is positive or negative.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 5, components having the same reference numerals as those in FIG. 1 perform the same functions. In this embodiment, the resolution of the A / D converter 5 is substantially improved. For example, when a motor or the like is employed as the load 2, the current at the time of inrush is large, but the current at the time of stable rotation is often small. At this time, if the measurement width is increased to measure the inrush current, that is, if the resolution is reduced,
The measurement accuracy of the current during the stable rotation cannot be secured, and an error occurs in the remaining capacity display. In the third embodiment,
The resolution of the A / D converter 5 can ensure measurement accuracy by switching the gain of the amplifier 42.

The circuit diagram of FIG. 5 is obtained by adding a resistor R7 comprising a variable resistor VR3 and a gain correction switching circuit 16 to the circuit diagram of FIG. That is, the resistor R7 is connected in parallel to the resistor R2, and the gain correction switching circuit 16 is provided at one end thereof. The gain correction switching circuit 16 is connected to the discharge current detection circuit 10 and the correction circuit 15, and outputs a signal indicating the switching state of the gain to the discharge current detection circuit 10 and the correction circuit 15.

When the gain correction switching circuit 16 is at the H level, the resistor R7 is disconnected from the circuit, and the gain G of the operational amplifier OP1 is represented by R1 / R2. On the other hand, when the gain correction switching circuit 16 is at the L level, the resistor R7 is connected in parallel with the resistor R2, and the gain G of the operational amplifier OP1 is R1 ×
It is expressed as (R2 + R7) / (R2 × R7). If R
If 7 = R2, the gain G when the gain correction switching circuit 16 is at the L level is 2 times the gain G when the gain correction switching circuit 16 is at the H level.
Double. That is, when the output of the gain correction switching circuit 16 is set to L level, the resolution of the A / D converter 5 can be doubled. However, the measurement width is ２. 6, a straight line A indicates the gain G when the output of the gain correction switching circuit 16 is at the H level, and a straight line B indicates the gain G when the output of the gain correction switching circuit 16 is at the L level.

The discharge current detection circuit 10 changes the conversion value according to the output state of the output of the gain correction switching circuit 16, and the output of the gain correction switching circuit 16 is H
When the output of the gain correction switching circuit 16 is at the L level, (R2 / R1)
1).

The variable resistor VR2 is adjusted when the gain correction switching circuit 16 is at the H level, and when the current value is an arbitrary current value Is, the output voltage becomes Vs ₁ on the ideal gain straight line A.
It is adjusted so that The variable resistor VR3 is intended to gain correction switching circuit 16 is adjusted at the L level, the output voltage at any time the current value Is is adjusted to be Vs ₂ on the straight line B.

The storage circuit 12 calculates the current value Is
The output voltages Vs ₁ and Vs ₂ are stored. When the gain correction switching circuit 16 is at the H level, Is and Vs ₁ are stored. When the gain correction switching circuit 16 is at the L level, I and Vs ₁ are stored.
s and Vs ₂ are the discharge current detection circuit 10 and the correction circuit 1
5 and so on.

The memory circuit 13 takes in the offset value Vo ₁ when the discharge switch SW is off and the gain correction switching circuit 16 is at H level, and then switches the gain correction switching circuit 16 to L level to take in the offset value Vo ₂ . And the gain correction switching circuit 1
6 is Vo ₁ is at H level, when the gain correction switching circuit 16 is at the L level Vo ₂ is used in the discharge current detection circuit 10 and correction circuit 15.

The correction circuit 15 calculates the actual discharge current of the battery by performing the same correction calculation as shown in the first embodiment. In this case, when the gain correction switching circuit 16 is at the H level, Is, Vs ₁ and Vo ₁ are used for the correction calculation, and when the gain correction switching circuit 16 is at the L level,
Is, Vs ₂ and Vo ₂ are used for the correction operation. The microcomputer 6 detects the H and L level states of the gain correction switching circuit 16, and detects the discharge current detection circuit 10 and the correction circuit 1
5 is switched.

If the gain correction switching circuit 16 is switched to the H level at the time of inrush in the case of a motor load or the like, and is switched to the L level at the time of stable rotation, current detection according to the load state can be suitably performed. This switching may be performed manually, or the microcomputer 6 may appropriately control the switching by time management or current management. Further, even when the load 2 is not a motor, current detection according to the load state can be performed with high accuracy.

In the third embodiment, the switching can be controlled as follows. That is, the output L level of the gain correction switching circuit 16 is set to the normal state (straight line B).
When the output value of the A / D converter 5 becomes full scale and exceeds the measurement range in the state of the output L level, this is detected and the output is switched to the H level (straight line A), and the measurement range is changed. Spread it out. On the other hand, when it is detected that the output value of the A / D converter 5 has dropped to a predetermined value or less in the state of the output H level, the output is returned to the L level to narrow the measurement range and increase the resolution.

In the first to third embodiments, the corrected output current of the discharge current detection circuit 10 is corrected by the correction circuit 15, but the contents stored in the storage circuits 12 and 13 are corrected by the discharge current detection circuit. It is also possible to adopt a configuration in which the correction is taken into account at the same time as the conversion. In each of the embodiments described above, the discharge current of the battery has been described. However, the charge current to the battery is similarly measured, and the charge capacity is integrated.
It can be displayed.

[0042]

As described above, according to the present invention,
Converting the battery current into voltage and detecting it, converting the amplified voltage output under a predetermined gain, automatically correcting the obtained current to the actual current, and integrating the battery capacity In this way, accurate and accurate current measurement can be achieved with an inexpensive circuit configuration without using a special and expensive operational amplifier, and only one adjusting means is required. Cost reduction can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram illustrating a relationship between a battery current and an output voltage of an amplifier 4 for explaining the operation of the first embodiment.

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

FIG. 4 is a characteristic diagram illustrating a relationship between a battery current and an output voltage of an amplifier 41 for explaining the operation of the second embodiment.

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

FIG. 6 is a characteristic diagram illustrating the relationship between the battery current and the output voltage of the amplifier 42 for explaining the operation of the third embodiment.

FIG. 7 is a circuit diagram of a conventional battery capacity display device.

FIG. 8 is a characteristic diagram showing a relationship between a discharge current and an output voltage of an amplifier 4 according to a conventional battery capacity display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Load 3 Low resistance 4,41,42 Amplifier 5 A / D converter 6 Microcomputer 7 Constant voltage circuit 8 Display circuit 10 Discharge current detection circuit 11 Remaining capacity calculation circuit 12,13 Storage circuit 14 Discharge SW detection circuit 15 Correction Circuit 16 Gain correction switching circuit 16 SW Discharge switch OP1 Operational amplifier Ro to R7 Resistance VR1 to VR3 Variable resistance

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 31/36

Claims (1)

(57) [Claims] 1. A resistor for detecting a current of a battery as a voltage between both ends, an amplifying means for amplifying a voltage between both ends of the resistor, and a first memory for storing an input current Is and an output voltage Vs representing a predetermined gain of the amplifying means. Storage means, adjustment means for previously adjusting and setting the output voltage of the amplifying means to Vs when the current of the battery is Is, and adjusting the output voltage of the amplifying means to the first voltage.
A conversion means for converting the current value of the battery into a current value using a predetermined gain stored in the storage means; a second storage means for storing an offset value Vo of the amplification means when the current of the battery is cut off; the first, it is stored in the second storage means
Is, Vs, the gain of the amplifier means from Vo obtained,
Correction means for correcting the output value of the conversion means from the gain and the predetermined gain, and remaining capacity calculation means for calculating the remaining capacity of the battery by integrating the corrected current value,
And a display unit for displaying the obtained remaining capacity.