JPH03235625A - Capacity indicating circuit - Google Patents

Abstract

PURPOSE:To decrease voltage drop across a resistor and to realize a simple and inexpensive circuit by amplifying the voltage across a detecting resistor through a first amplifier at the time of charging of a battery whereas through a second amplifier at the time of discharging. CONSTITUTION:When an Ni-Cd battery 1 is charged, voltage across a current detecting resistor 2 is amplified through an inverted amplifier 3. When the Ni-Cd battery 1 is discharged, the voltage across the resistor 2 is amplified through a non-inverted amplifier 4. Consequently, charge/discharge state of the battery 1 can be judged through a simple structure and the voltage drop across the resistor 2 can be suppressed. Furthermore, since the operating section, i.e., a microcomputer 8, deals with a considerably high amplified voltage, accuracy thereof may be as low as 8b;t, for example, resulting in cost reduction of the device. Operation results can be indicated, as the residual capacity of the battery 1, on a display circuit section 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Application in Industry-1- The present invention relates to a capacity table/8 circuit for calculating and displaying the capacity of a battery.

(B) Conventional technology Conventionally, a secondary battery, a 14-current detection resistor connected in series to the secondary battery, and a 14-current detection resistor connected to the secondary battery and the current detection resistor are used to measure the charging and discharging of the secondary battery. A circuit that is equipped with a microcomputer to calculate and display the battery capacity was published in Japanese Patent Application Laid-Open No. 6+.
This is disclosed in Japanese Patent No. 29079, but 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 across the resistor sufficiently small compared to the output voltage of the battery, it is necessary to increase the potential difference detection ability of the microcomputer, which makes the device itself expensive.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above points, and aims to suppress the voltage drop [゛] occurring in the element that detects the battery current as low as possible, and at the same time The voltage of the arithmetic unit that calculates (
To provide an armpit display circuit that is inexpensive and has a simple structure without increasing the ability to detect a q difference.

(d) Means for Solving the Problems The present invention provides a capacity display circuit that calculates and displays the charge/discharge amount tL of a battery. a D/A converter for converting a signal into an analog signal; a current detection means for detecting a charge/discharge current of the battery; a first amplification means for amplifying the voltage generated by the lower current detection stage when charging the battery; A second amplification lower stage that amplifies the voltage generated by the current detection f-stage during discharging, an analog signal generated by the D/A converter, and an output of the first and second amplification means j. and a first and second comparison means for outputting the comparison result to the arithmetic section, and a lower display section for displaying the arithmetic result processed in the arithmetic section according to the comparison result.

(E) Effect According to the present invention, is the current generated by the current detection means? 1tI
The first amplifying means amplifies this voltage when the battery is being charged, and the second amplifying means amplifies this voltage when the battery is discharging, thereby reducing the voltage drop that occurs at the lower stage of the current detection. be able to. Furthermore, since the arithmetic unit processes the amplified voltage that is seven times larger, it may have low accuracy, and the device itself can be made inexpensive.

(f) Example Hereinafter, embodiments of the present invention will be described in detail with reference to 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. A resistor 2 serves as a current detection means, and is designed to have a value of several meters to several tens of milliohms. 3 and 4 are an inverting amplifier and a non-inverting amplifier as first and second amplification means, respectively, and these amplifiers operate with a single power supply,
It is designed not to output negative values. 5 and 6 are first and second comparators as comparison means, respectively, and the output of the amplifier 3.4 is inputted to the input terminals of the comparators 1/-5 and 6. On the other hand, an analog signal generated by a D/A converter 7, which will be described later, is input to one input terminal.

Reference numeral 8 denotes a microcomputer as an arithmetic unit, which receives the outputs of the first and second comparators 5 and 6 and outputs a digital signal. After this digital signal is converted into an analog signal by the D/A converter 7, it is inputted to one input terminal of the comparators 5 and 6 as described above. Further, reference numeral 9 denotes a display circuit section, which displays the remaining capacity of the battery calculated by the microcomputer 8 by lighting an LED.

By the way, when a charger is connected to the N1-Cd1i battery 1 and a charging current flows, a voltage drop F, vl in the figure, occurs in the resistor 2. At this time, since the inputs of the inverting amplifier 3 and the non-inverting amplifier 4 become negative voltages, the inverting amplifier 3
The output of Wlri, which is proportional to the above-mentioned 1, is generated, while the output of the inverting amplifier 41 becomes the GND level.

Conversely, a load etc. is connected to the N i -Cdt pond l,
When the discharge current flows, a voltage drop v2 in the figure occurs across the resistor 2. At this time, the output of the inverting amplifier 3 is GND
On the other hand, the output of the non-inverting amplifier 4 generates a voltage proportional to the voltage v2.

Therefore, when charging the N1-Cdt battery 1, the inverting amplifier 3 amplifies the voltage generated by the resistor 2, and when discharging the voltage, the non-inverting amplifier 4 amplifies it.

Further, the digital signal generated by the microcomputer 8 changes its value moment by moment, and is converted into an analog signal by the D/A converter 7. Here, the first and second comparators 5 and 6 successively compare the analog signal and a voltage obtained by amplifying the voltage generated by the resistor 2, and input the comparison results to the microcomputer 8. On the other hand, the microcomputer 8 calculates the Ni-
The remaining capacity of the Cd battery 1 is calculated.

Below 1. In such a configuration, when the Ni-Cd battery 1 is connected to a charger via a display circuit and the battery 1 is charged, a charging current flows through the resistor 2. At this time, a voltage drop of 1 shown in the figure occurs across the resistor 2, and this voltage is amplified by the inverting amplifier 3 as described above and is input to the input terminal of the first comparator 5. On the other hand, the digital signal generated by the microcomputer 8 is sent to the D/A converter 7.
The signal is inputted to one input terminal f of the first comparator 5 via. Here, the comparator 5 successively compares the two and outputs the comparison result to the microcomputer 8. At this time, the microcomputer 8 determines that the battery is in a charging state, calculates a digital signal corresponding to the comparison result, and displays the calculation result on the display circuit section 9 as the remaining capacity of the battery.

On the other hand, when the N1-Cd battery 1 is connected to a load or the like via the capacity display circuit of the present invention and the battery 1 is discharged, a current flows through the resistor 2. At this time, a voltage drop v2 shown in the figure occurs in the resistor 2, and this voltage in is amplified by the non-inverting amplifier 54 as described in 1 and is input to the input terminal of the second comparator 6. Ru. On the other hand, a digital signal generated by the microcomputer 8 is input to one input terminal of the second comparator 6 via the D/A converter 7. Here, the comparator 6 successively compares the two and outputs the comparison result to the microcomputer 8. At this time, the microcomputer 8 determines that the battery is in a discharged state, calculates a digital signal corresponding to the comparison result, and displays the calculation result on the display circuit section 9 as the remaining capacity of the battery.

(g) Effects of the Invention According to the present invention, the first amplifying means amplifies the voltage generated by the resistor for detecting current flow when the battery is being charged, while the voltage is amplified when the battery is being discharged. Since the second amplifying means amplifies this voltage, the charging/discharging state of the battery can be determined with a simple structure, and the drop in tri generated in the resistor can be suppressed to a small level. In addition, since the arithmetic unit is designed to process a sufficiently large amplified voltage, 8
The accuracy may be as low as a bit, and the price of the device can be lowered.

[Brief explanation of drawings]

The drawing is an electrical circuit diagram showing one row of one embodiment of the volumetric display circuit of the present invention. 1... Ni-Cd battery, 2... Resistor, 3...
Inverting amplifier, 4...Non-inverting amplifier 95...First comparator, 6...Second comparator, 7...
D/A converter, 8...microcomputer, 9 display circuit section.

Claims (1)

[Claims] (1) In a capacity display circuit that calculates and displays the amount of charge and discharge of a battery, there is a calculation section that calculates the amount of charge and discharge of the battery, and a digital signal that converts the digital signal generated by the calculation section into an analog signal.
A converter, a current detection means for detecting the charge/discharge current of the battery, a first amplification means for amplifying the voltage generated by the current detection means when the battery is charged, and a voltage generated by the current detection means when the battery is discharged. a second amplifying means for amplifying the voltage generated by the D/A converter; and a second amplifying means for comparing the analog signal generated by the D/A converter with the output of the first and second amplifying means and outputting the comparison result to the arithmetic unit. 1. A capacity display device comprising: second comparison means; and display means for displaying the calculation results processed in the calculation section according to the comparison results.