JPH0442075A - Capacity display circuit - Google Patents

Abstract

PURPOSE:To suppose a voltage drop to a low value by using amplifying means for amplifying the drop generated at an element for detecting a battery current and to simultaneously prevent an erroneous calculation due to an offset voltage of the means. CONSTITUTION:When a charging/discharging current flows to a battery 1, voltage drops V1, V2 are generated at a resistor 2 of current detecting means. In this case, since an inverting amplifier 4 generates a positive voltage proportional to the V1 and a non-inverting amplifier 5 generates a positive voltage proportional to the V2, a calculation with the positive values can be performed. On the other hand, when no charging/discharging current flows to the battery 1, they are not input to the amplifiers 4, 5, but a superposing voltage generator 6 always generates a negative voltage, which is divided, and input to the amplifiers 4, 5. Accordingly, the output voltages of the amplifiers 4, 5 become positive values. A calculator 10 stores a calculated result when no charging/ discharging current flows to the battery 1, subtracts the stored calculated result from the calculated result when the current flows, integrates the result, and displays it on a display 11. Accordingly, an offset voltage when the current does not flow to the battery 1 is not erroneously calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a capacity display circuit that calculates and displays the capacity of a battery.

(b) Conventional technology Conventionally, a secondary battery, a current detection resistor connected in series to the secondary battery, and a micro-microphone connected to the secondary battery and the current detection resistor to measure the amount of charge and discharge of the secondary battery. A circuit equipped with a computer and capable of calculating and displaying the capacity of a battery was published in Japanese Patent Application Laid-open No. 1983-
This is disclosed in Japanese Patent No. 29079, and in this case, the voltage generated in the current detection resistor is directly read by a microcomputer. Here, in order to make the voltage drop occurring in the resistor sufficiently small compared to the output voltage of the battery, it is necessary to
It is necessary to increase the phase difference detection ability, and the device itself becomes expensive. Therefore, it is conceivable to provide an amplification means to amplify the voltage generated in the current detection resistor according to the charge/discharge current, but for example, an amplification means such as an OP amplifier generates an offset voltage even when the input is zero. It is known. That is, there is a concern that an output may be generated in the OP amplifier even when no charging/discharging current is flowing through the battery, and the calculation section may calculate the output incorrectly.

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned problem, and minimizes the voltage drop by using an amplifying means that amplifies the voltage drop F generated in the element that detects the battery current. The objective is to keep the voltage low and at the same time to prevent erroneous calculations due to offset voltage of the amplifier stage.

(d) Means for Solving the Problems The present invention provides a display circuit for calculating and displaying the amount of charge and discharge of a battery. a superimposed voltage generating circuit that generates a voltage superimposed on the voltage generated by the current detecting means, and an amplifying means that amplifies the voltage generated by the current detecting means and the voltage generated by the superimposed voltage generating circuit. and a calculation section for processing the voltage amplified by the amplification means, and a display means for displaying the calculation results of the calculation section, and the @tube voltage generation circuit is always inputted to the amplification means, On the other hand, the calculation section stores the calculation result when only the voltage generated by the superimposed voltage generation circuit is input to the amplification means without charging/discharging current flowing through the battery, and when charging/discharging current flows through the battery and the The stored operation result is subtracted from the operation result when the voltage generated by the detection means and the voltage generated by the superimposed voltage generation circuit are input to the amplification means, and the subtracted result is displayed on the display means. It is characterized by this.

The present invention also provides a first switch connected between an output end of the current detection means and an input end of the amplification means into which the output of the current detection means is input, a contact connected to ground, and a contact point of the amplification means. and a second switch connected between the input end and the output of the arithmetic unit, the first switch is normally closed and the second switch is open, and the first switch is intermittently closed at minute intervals. It is characterized in that it opens and the second switch closes.

(E) Generally, a working amplifier outputs an offset voltage even when the input is O, but this offset voltage appears in mV. On the other hand, since the arithmetic unit is designed to perform arithmetic processing on the output of the amplifying means when the output is a positive value, if the negative offset voltage is output as is, the arithmetic unit will be unable to perform calculations. According to the present invention, if the voltage obtained by amplifying the voltage generated by the superimposed voltage generating circuit is made larger than the negative voltage of the offset voltage, the current detecting means input to the amplifying means which is the object of calculation can be Even if the generated voltage becomes small, the amplified voltage will not become smaller than the negative voltage of the offset voltage, and the output voltage of the amplifying means at this time can always be a positive value and calculation can be performed at all times. Further, the calculation unit stores the calculation result when only the voltage generated by the ton/π type pressure generation circuit is input to the amplification means, that is, when no charging/discharging current flows through the battery, and stores the calculation result when the charging/discharging current is flowing through the battery. The stored calculation result is subtracted from the calculation result when the current is flowing, and the subtracted result is converted to V4W and displayed on the display means, so the OP when no charge/discharge current is flowing through the battery. There is no possibility of erroneously calculating the output of the amplifier as it is.

Furthermore, it is known that the offset voltage of an amplifier changes depending on the ambient temperature and the like. Therefore, the amplifier is charged t
If the Lt ponds are placed close together, due to temperature changes of the batteries,
The offset voltage of the amplifying means changes. As a result, the degree of increase in amplification means also changes. Therefore, according to the present invention, there is provided a first switch connected between the output terminal of the current detection stage and the input terminal of the amplification T stage for manually inputting the output of this current detection means, and a contact connected to ground. and a second switch connected between the input end of the amplification means, and the first switch is normally closed and the second switch is open depending on the output of the arithmetic unit, and the output is intermittently set at minute intervals. Since the first switch is opened and the second switch is closed only when only the voltage generated by the superimposed voltage generation circuit is input to the amplification means during this minute time, the calculation section The stored value of the calculation result when no charge/discharge current is flowing through the battery is updated to correct the change in the amplification degree of the amplification means.

(f) Example Embodiments of the present invention will be described in detail below based on the drawings.

The drawing is an electrical circuit diagram showing an embodiment of the capacitance display circuit of the present invention.

In the figure, 1 is N1 connected to the capacitance display circuit of the present invention.
- It is a Cdt pond.

Reference numeral 2 denotes a resistor as a current detecting means, which generates a voltage depending on the charging/discharging current across the resistor.

Reference numerals 31 and 32 are a first switch and a second switch, which will be described later, respectively, and these switches 31 and 32 are designed to be switched in conjunction with each other.

Reference numerals 4 and 5 denote an inverting amplifier and a non-inverting amplifier as first and second amplification means, respectively. These amplifiers operate with a single power supply, and the voltage generated by the resistor 2 is transferred to the inverting amplifier 4.
The signal is input to one input terminal, and the non-inverting amplifier 5 is input to ten input terminals. That is, when the battery 1 is connected to a charger and being charged, the inverting amplifier @4 outputs a positive output, while when the battery 1 is connected to a load or the like and being discharged, the non-inverting amplifier 5 outputs a positive output. It's starting to happen.

Further, 6 is a superimposed negative voltage generation circuit, which generates a negative voltage of -3V, and this negative voltage is divided by a resistor and then inputted to one input terminal of the inverting amplifier 4 and the non-inverting amplifier 5, respectively. It has become.

Reference numerals 7 and 8 are first and second conhalators serving as comparison means, respectively, and the outputs of the amplifiers 4 and 5 are input to the input terminals of the comparators 7 and 8. An analog signal generated by a D/A converter 9, which will be described later, is input to the input terminal.

10 is a microcomputer as an arithmetic unit,
The output of the second comparator 7.8 described in πj is manually input, and a digital signal is output. After this digital signal is converted into an analog signal by the D/'A converter 9, it is inputted to one input terminal of the comparator 7.8 as described above. Furthermore, the microcomputer 10 further includes the switch 31 .
32, which normally closes the first switch 31 and opens the second switch 32, periodically opens the first switch 3I by minute intervals and switches the second switch 3I The opening 32 is closed.

Note that the first switch 311. is connected between the output end of the current detection means and the input end of the amplification means into which the output of the current detection means is input, and the second switch 32 is connected between a contact connected to ground and the input end of the amplification means. is connected between.

Reference numeral 11 denotes a display circuit section, which displays the remaining capacity of the battery calculated by the microcomputer 10 by lighting an LED.

By the way, a charge is connected to the Ni-Cd battery l,
When the charging current flows, a voltage drop vl in the figure occurs across the resistor 2. At this time, since the inputs of the inverting amplifier 4 and the non-inverting amplifier 5 become negative voltages, the output of the inverting amplifier 4 generates an IE main voltage that is not proportional to the above 1.

Conversely, when a load or the like is connected to the N1-Cd battery l and a discharge current flows, a voltage drop v2 in the figure occurs across the resistor 2. At this time, the output of the non-inverting amplifier 5 is
A positive voltage proportional to 2 is generated.

Therefore, when the N1-Cd battery 1 is being charged, the inverting amplifier 4 generates a positive output, and when discharging the N1-Cd battery 1, the non-inverting amplifier 5 generates a positive output.

On the other hand, when no charging/discharging current flows through the battery 1, the resistor 2
does not generate a voltage and is not input to the amplifier 4.5, but the superimposed voltage generation circuit 6 always generates a negative voltage, and after this is divided, it is input to one input terminal of the amplifiers 4 and 5. , so the output voltage of the amplifier is always a positive value.

Further, the digital signal generated by the microcomputer 10 changes its value moment by moment, and is converted into an analog signal by the D/A converter 9. Here, the first and second comparators 7.8 successively compare the voltage obtained by amplifying the sum of the voltage generated by the resistor 2 and the negative voltage generated by the superimposed voltage generation circuit 6 with the analog signal. , and inputs the comparison result to the microcomputer 10.

On the other hand, the microcomputer 10 is designed to calculate only the result of comparison between the output of the amplifying means that generated the positive output and the analog signal. Therefore, when charging the battery 1, the voltage input to the inverting amplifier 4 is calculated, and when discharging the battery 1, the voltage input to the non-inverting amplifier 5 is calculated. The voltage value calculated at this time is a voltage obtained by amplifying the sum of the voltage generated by the resistor 2 and the negative voltage generated by the superimposed voltage generation circuit 6.

Here, the microcomputer IO includes the superimposed voltage generation circuit 6
The calculation result is stored when only the generated voltage is input to the amplification means, that is, when no charging/discharging current is flowing through the battery l.

Therefore, the voltage obtained by amplifying only the voltage generated by the superimposed voltage generating circuit 6 is subtracted from the calculation result of the voltage obtained by amplifying the sum of the voltage generated by the resistor 2 and the negative voltage generated by the superimposed voltage generating circuit 6. , by integrating the subtracted results, only the actual measured value of the charging/discharging current of the battery 1 can be integrated.

In addition, the microcomputer IO always controls the first switch 31.
is closed and the second switch 32 is open, but the first switch 31 is periodically opened by minute intervals, and the second switch 32 is opened.
is now closed. As a result, during the charging and discharging of the battery I, a state in which no current flows through the battery 1 is periodically created for minute intervals. At this time, as described above, only the voltage generated by the superimposed voltage generating circuit 6 is input to the amplifying means, and the microcomputer 10 stores the calculation result at that time. Therefore, the values stored in the microcomputer 10 are updated sequentially. To explain this in detail, the microcomputer 10 always calculates the output from the amplifier that generated the positive output. That is, when charging the battery 1, the output of the inverting amplifier 4 is always positive and Unless the output of the non-inverting amplifier 5 is always positive when discharging 1, the microcomputer 10 will be unable to perform addition during charging and subtraction during discharging. - A force field width transducer generally outputs an offset voltage even when the input is O, but this offset voltage appears at more than ten mV. If this negative offset voltage is output as it is, the microcomputer will be unable to perform calculations. Therefore, as mentioned above, the superimposed voltage generation circuit 6 is provided to supply a negative voltage to the amplifier even when no charging/discharging current is flowing through the battery l. is not output. It is also known that the offset voltage of an amplifier changes depending on the ambient temperature and the like.

Therefore, if a battery to be charged is placed close to the amplifier, the offset voltage of the amplifier changes due to a change in the temperature of the battery. As a result, the amplification degree of the amplifier also changes, and in order to correct this, the microcomputer 10 periodically updates the stored value as described above.

In this embodiment, the voltage generated by the superimposed voltage generation circuit 6 is a negative voltage, but the present invention is not limited to this, and it is also possible to generate a positive voltage and input it to each of the input terminals of the amplifiers 4 and 5. good.

(g) The effect amplifier of the invention generally outputs an offset voltage even when the input is O, but this offset voltage appears at more than ten mV. On the other hand i
The calculation unit is designed to process the output of the amplifier I stage when it is a positive value, so if the negative offset voltage is output as is, the calculation unit will not be able to perform calculations. turn into. According to the present invention, if the voltage obtained by amplifying the voltage generated by the superimposed voltage generating circuit is made larger than the voltage of the offset voltage, the current detecting means input to the amplifying means which is the object of calculation can be Even if the generated voltage becomes small, the amplified voltage will not become smaller than the negative voltage of the offset voltage, and the output voltage of the amplifying means at this time can always be calculated as a positive value. Further, the calculation section stores the calculation result when only the voltage generated by the superimposed voltage generation circuit is input to the amplification means, that is, when no charging/discharging current is flowing through the battery, and when the charging/discharging current is not flowing through the battery. The stored calculation result is subtracted from the calculation result when the battery is charged, and the subtracted result is integrated and displayed on the display means, so the output of the OP amplifier when no charge/discharge current is flowing through the battery There is no way to calculate it incorrectly.

Furthermore, it is known that the offset voltage of an amplifier changes depending on the ambient temperature and the like. Therefore, if a battery to be charged is placed close to the amplifier, the offset voltage of the amplifying means changes due to a change in the temperature of the battery. As a result, the amplification degree of the amplification means also changes. Therefore, according to the present invention, the first switch is connected between the output end of the current detection means and the input end of the amplification means into which the output of the current detection means is input, the contact connected to ground and the amplification means are connected to each other. and a second switch connected between the input end of the means, and the first switch is normally closed and the second switch is open according to the output of the arithmetic unit, and the first switch is intermittently closed at minute intervals. Since the switch is configured so that it opens and the second switch closes,
The calculation unit updates the stored value of the calculation result when only the voltage generated by the superimposed voltage generation circuit is input to the amplification means during this minute time, that is, when no charging/discharging current is flowing through the battery. , to compensate for changes in the amplification degree of the amplification means.

[Brief explanation of drawings]

The drawing is an electrical circuit diagram showing an embodiment of the capacitance display circuit of the present invention. 1... Ni-Cd battery, 2... Resistor, 31. First switch, 32... Second switch, 4... Inverting amplifier, 5... Non-inverting amplifier, 6 - Superimposed voltage generation circuit , 7... first comparator, 8... second comparator, 9... D/A converter, 10 - microcomputer, 11... display circuit section.

Claims (2)

[Claims] (1) In a capacity display circuit that calculates and displays the charge and discharge amount of the battery, a current detection means that detects the charge and discharge current of the battery;
a superimposed voltage generating circuit that generates a voltage to be superimposed on the voltage generated by the current detecting means; an amplifying means that amplifies the voltage generated by the current detecting means and the voltage generated by the superimposed voltage generating circuit; The superimposed voltage generating circuit is always inputted to the amplifying means, and the calculating section is configured to control the charging and discharging of the battery. The calculation result when only the voltage generated by the superimposed voltage generation circuit is input to the amplification means without current flowing is stored, and when a charging/discharging current flows through the battery, the voltage generated by the current detection means and the superimposed voltage are stored. A capacity display circuit characterized in that the stored calculation result is subtracted from the calculation result when the generated voltage of the generation circuit is input to the amplification means, and the subtracted result is displayed on the display means. (2) a first switch connected between the output end of the current detection means and the input end of the amplification means into which the output of the current detection means is input; a contact connected to ground; and an input end of the amplification means; and a second switch connected between the first and second switches, and the first switch is normally closed and the second switch is open according to the output of the calculation section, and the first switch is intermittently opened only at minute time intervals. 2. The capacity display circuit according to claim 1, wherein the second switch is closed.