WO2004053511A1

WO2004053511A1 - Current sensor and battery remaining power sensing system

Info

Publication number: WO2004053511A1
Application number: PCT/JP2003/015847
Authority: WO
Inventors: Kenichi Ohkubo
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 2002-12-12
Filing date: 2003-12-11
Publication date: 2004-06-24
Also published as: TWI229742B; TW200420897A; JP2004191241A

Abstract

A battery remaining power sensing system for stably sensing the battery remaining power accurately comprises a current sensing circuit (30) installed in a device body (1a) and a remaining power calculation microcomputer (34) installed in a battery pack (2a). The current sensing circuit includes a reference voltage generating section (31) for generating a reference voltage (Vb) and an A/D converter (26) for converting the reference voltage (Vb) and the terminal voltage (Vi) of the current sensing resistive element (24) to two pieces (D(Vi), D(Vb)) of digital data. The remaining power calculation microcomputer calculates the discharge current (I) flowing through a power supply line (28) by using the ratio between the two pieces of digital data.

Description

Specification

Current detection device and remaining battery detection system

The present invention is directed to a remaining amount detection system that calculates a discharge current flowing through a power supply line based on a voltage between terminals of a current detection resistance element, and calculates a remaining amount of a battery from the calculated current value, and a current used in the system. It relates to a detection device. Background art

Batteries are often used as power sources for portable electronic devices such as mobile phones and digital cameras. Since these batteries are storage batteries,

However, the battery capacity that can be used once is limited and must be charged before it is exhausted. In order to notify the user of the remaining battery level, the remaining battery level is displayed on a display device installed in the device. Conventionally, as a method of detecting the remaining amount of the battery for performing such display, a method of detecting the amount of discharge current flowing through a power supply line connected to the battery and calculating the remaining amount of the battery from the detected amount of current has been used. It is known (for example, Japanese Patent Application Laid-Open No. Hei 4-332580).

FIG. 1 is a block diagram of a conventional battery remaining power detection system. The device body 1 is, for example, a mobile phone or a digital camera. Inside the main unit 1, there are a main unit load 27 that performs the original functions of the mobile phone and digital camera, a control microcomputer 22 that controls the overall operation of the main unit 1, and a standby screen for the mobile phone. A display device 23 for displaying an image captured by the camera is provided.

The battery pack 2 is detachable from the device body 1. Inside the battery pack 2, a battery 11, a current detecting resistor 24, a current detecting circuit 21, and a remaining amount calculating microcomputer 12 are provided. The current detection resistance element 24 is a minute resistance provided in the middle of the power supply line 28, and the voltage V i between the terminals of the minute resistance is extracted by the current detection circuit 21. The current detection circuit 21 includes an amplifier 25 and an AZD converter 26. The amplifier 25 is connected to the current detecting resistance element 24, amplifies the voltage V i extracted from the current detection resistance element 24, and generates an amplified voltage V i '. Is output. The octano converter 26 receives the amplified voltage V i ′ from the amplifier 25, normalizes the amplification voltage V i ′, converts it into digital data, and generates voltage data D (V i). The remaining amount calculation microcomputer 12 receives the voltage data D (V i) from the current detection circuit 21 and calculates a discharge current I flowing through the power supply line 28 based on the voltage data D (V i). Calculate the remaining battery capacity of battery 11 from discharge current I. The calculated remaining battery level is transferred to the control microphone port computer 22 via the communication line 29, and the control microphone port computer 22 displays the remaining battery level on the display device 23.

In the conventional battery remaining power detection system, a gain error sometimes occurs in the amplifier 25 of the current detection circuit 21. This error causes a detection error of the discharge current, and there is a problem that the remaining battery level cannot be accurately detected. In addition, if the reference voltage Vr for the AD converter 26 fluctuates, an error occurs in the voltage data D (Vi), and this error may cause inaccurate detection of the remaining battery level. Was.

In order to avoid such inconveniences, it is conceivable to use an amplifier having a small gain error or to use a voltage source having no fluctuation in output voltage as a reference voltage supply source for the A / D converter 26. However, since a high-precision amplifier and voltage source are required, there is a disadvantage that the cost of the battery level detection system increases. Disclosure of the invention

The present invention provides a remaining amount detection system and a current detection device that can accurately calculate the value of a current flowing through a power supply line without being affected by a gain error of an amplifier or an output error of an AZD converter. With the goal.

An aspect of the present invention is achieved to solve at least one of the above-described problems. The present invention relates to a remaining amount detecting device that calculates the remaining amount of a battery. Disclosed is a current detection device that supplies data representing the amount of discharge current flowing through a power supply line having a current detection resistance element disposed in the power line. The current detection device includes: a reference voltage generation circuit that generates a reference voltage; first data corresponding to a terminal-to-terminal voltage of a current detection resistance element arranged in the power supply line; and a reference voltage corresponding to the reference voltage. The first And an A / D conversion circuit for generating the second data.

The present invention further discloses a system for detecting a remaining battery level. The system includes a current detection device that is connected to the battery and generates data representing a discharge current amount flowing through a power supply line having a current detection resistance element disposed in the middle thereof, and a remaining device that calculates a remaining amount of the battery. An amount detection device. The current detection device generates a reference voltage generation circuit that generates a reference voltage, first data corresponding to a voltage between terminals of the current detection resistance element, and second data corresponding to the reference voltage. And an AD conversion circuit. The remaining amount detection device calculates the amount of discharge current based on the first and second data, and integrates the calculated amount of current to calculate the remaining amount of the battery. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a conventional battery remaining power detection system.

FIG. 2 is a block diagram of a battery remaining amount detection system according to a preferred embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of the battery remaining amount detection system in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 2 is a block diagram of the battery remaining power detection system according to the preferred embodiment of the present invention. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

Device body 1 _a is, for example, an electronic device such as a mobile phone or a digital camera, in addition to the main body load 2 7 control microcomputer Ichita 2 2, for detecting the current flowing amount of the power supply line 2 8 As components, a current detecting resistor element 24 and a current detecting circuit 30 are provided.

The current detecting resistance element 24 is a minute resistance provided in the middle of the power supply line 28. The voltage V i between the terminals of the current detection resistance element 24 is taken out by the current detection circuit 30. The current detection circuit 30 includes a reference voltage generator 31, a selector 32, an amplifier 25, an AZD converter 26, and an output unit 33. The reference voltage generator 31 generates a reference voltage Vb from the power supply voltage of the device body 1a. The reference voltage generator 31 is, for example, This is a gap-type reference voltage source, and can stably output the reference voltage Vb in response to temperature changes, power supply voltage fluctuations, and manufacturing variations.

It is conceivable that the band gap type reference voltage generation source is a voltage source for the reference voltage Vr for the AZD converter 26. However, the bandgap-type reference voltage source has a characteristic that unless the output voltage is about 1.2 V, a stable output voltage cannot be output with respect to a temperature change or the like. For this reason, for an AZD converter that requires a voltage higher than 1.2 V as a reference voltage, a non-gap-type reference voltage source cannot be used as a reference voltage Vr.

The selector 32 connects the first input terminal S a connected to one terminal of the current detecting resistance element 24 and the second input terminal S b connected to the output terminal of the reference voltage generator 31. Have. The selector 32 operates, for example, in response to a selection signal SEL supplied from the control microcomputer 22 and selects one of the two input terminals Sa and Sb (V i, V b). And output. In the present embodiment, the selector 32 selects the inter-terminal voltage Vi and the reference voltage Vb in a time-division manner according to the selection signal SEL.

The amplifier 25 is connected to the output terminal of the selector 32, amplifies the inter-terminal voltage Vi and the reference voltage Vb of the current detecting resistance element 24, and generates the first amplified voltage Vi ′ and the second amplified voltage V Generate b 'respectively.

The AZD converter 26 operates by receiving the reference voltage Vr generated from the voltage of the power supply line 28, and converts the first and second amplified voltages V i ′, Vb ′ output from the amplifier 25 into digital data. The conversion generates first and second voltage data D (V i) and D (Vb), and outputs the first and second voltage data D (V i) and D (Vb).

The output unit 33 is connected to the output terminal of the AZD converter 26, receives the first and second voltage data D (Vi) and D (Vb), and converts the data into a format such as a parallel / serial conversion. The data is converted and output to the communication line 29.

The battery pack 2a is attachable to and detachable from the device body 1a, and includes a battery 11 and a computer 34 for calculating the remaining capacity of microphone. Microcomputer for calculating remaining amount The computer 34 receives the two data D (Vi) and D (Vb) transferred via the communication line 29, calculates a ratio D (Vi) / D (Vb), and based on the calculated ratio. Then, the discharge current I flowing through the power supply line 28 is calculated, the remaining battery level is calculated from the current I, and the remaining battery level is supplied to the control microcomputer 22 of the device body 1a via the communication line 29. .

In this embodiment, in order to reduce the size of the device mounted on the battery pack 2a, the computer 34 for calculating the remaining amount of microphone and the current detection circuit 30 are separately mounted, and the current detection circuit 30 is mounted on the main body of the device. The microcomputer is mounted on the battery pack 2a.

FIG. 3 is a flowchart illustrating the operation of FIG. The processing of steps S1 to S4 is performed on the device body 1a side, and the processing of steps S5 to S7 is performed on the battery pack 2a side.

In step S1, the selector 32 selects the first input terminal Sa, and supplies the first voltage Vi to the amplifier 25.

In step S2, the amplifier 25 amplifies the first voltage V i to generate a first amplified voltage V i ′, and supplies the first amplified voltage V i ′ to the AZD converter 26. The AZD converter 26 converts the first amplified voltage V i ′ into digital data (first voltage data D (V i)), and the output unit 33 converts the first voltage data D (V i) into a communication line. 2 Output to 9.

In step S3, the selector 32 selects the second input terminal Sb, and supplies the second voltage Vb to the amplifier 25.

In step S4, the amplifier 25 amplifies the second voltage Vb to generate a second amplified voltage Vb ', and supplies the second amplified voltage Vb' to the AZD converter 26. The A / D converter 26 converts the second amplified voltage Vb 'into digital data, and the output unit 33 outputs the second voltage data D (Vb) to the communication line 29.

In step S5, the remaining amount calculation microcomputer 34 performs an operation on the received first and second voltage data D (V i) and D (Vb) to obtain the first voltage data D (V i) and The ratio D (V i) / Ό (Vb) to the second voltage data D (Vb) is calculated. The microcomputer 34 calculates the first voltage obtained in step S2. The data D (V i) is retained by dividing the retained data D (V i) by the second voltage data D (V b) obtained in step S4. Calculate D (V b).

In step S6, a discharge current I flowing through the power supply line 28 is calculated. For example, in step S6, first, based on the ratio D (V i) / Ό (V b) of the two voltage data calculated in step S5, the voltage V i between the terminals of the current detecting resistance element 24 is determined. Is calculated.

Here, a method of calculating the inter-terminal voltage Vi will be described. First, the value of the second voltage data D (V i) in step S2 is expressed by equation (1). Here, Ga is the gain of the amplifier, and N is the number of bits of digital data output from the A / D converter 26.

D (Vi) = ... (1)

(Vr / 2 ^N ) On the other hand, the value of the first voltage data D (V b) in Step S4 is expressed by Equation 2.

D (Vb) = ^-… (

(Vr / 2 ^N ) By dividing Equation 1 by Equation 2 and rearranging, Equation 3 is obtained.

D (Vi),

Vi = Vb <(3)

D (Vb) Therefore, the inter-terminal voltage Vi can be calculated according to Equation 3. Although the reference voltage Vb is the output voltage of the reference voltage generator 31, it is a voltage that always shows a constant value. By storing it, the operation of Equation 3 can be performed.

Subsequently, from the calculated inter-terminal voltage V i, a current flowing through the current detecting resistance element 24, that is, a discharge current I flowing through the power supply line 28 is calculated using the following equation.

I = V i / R. Here, R is the resistance value of the current detection resistance element 24.

In step S7, the remaining amount of the battery 11 is calculated using the current I. For example, the current The time interval at which the first and second voltage data D (V i) and D (V b) are transmitted from the detection circuit 30 is defined as the first and second voltages transmitted by the Δΐ and η-th current detections. Voltage data is D (V in), D (V bn), and the current value calculated from these two voltage data is I (n), Δ from the _n-th current detection to the ( _n + 1) -th current detection The integrated current discharged during t is represented by I (η) · Δ1: Then, the accumulated amount of discharge current I (η) · Δt is measured in advance when the battery 11 is charged, and is subtracted from the accumulated remaining battery amount, so that the remaining battery amount of the battery 11 is reduced. Is calculated. According to the present embodiment, the current detection circuit 30 including the reference voltage generation unit 31 outputs the first and second voltage data D (V i) and D (V b). The remaining amount calculation microcomputer 34 calculates the inter-terminal voltage Vi using the ratio D (Vi) / V (Vb) of the first and second voltage data. Thus, the discharge current I can be obtained without being affected by the gain error of the amplifier 25 or the output error due to the fluctuation of the reference voltage Vr with respect to the A / D converter 26. That is, the first and second voltage data D (V i) and D (V b) include the gain error of the amplifier 25 and the output error of the A / D converter 26 by substantially the same amount. However, by using the ratio D (V i) / Ό (V b) of the two voltage data, the errors included in the two voltage data cancel each other out. Then, the terminal voltage V i is calculated by multiplying this ratio by the reference voltage V b stored in the remaining capacity calculation microcomputer 34. Therefore, the terminal voltage V i is a true value that does not include an error. Therefore, the discharge current I flowing through the power supply line 28 can be accurately derived, and the battery remaining amount can be accurately calculated.

In the present embodiment, the current detection circuit 30 is mounted on the device body 1a, but is not limited to this. That is, as shown in FIG. 1, the current detection circuit 30 may be mounted on the battery pack 2a. Further, instead of performing the process of obtaining the ratio of the first and second voltage data D (V i) and D (V b) by the remaining amount calculation microcomputer 34, the current detection circuit 30 may perform the process. In this case, a circuit for calculating the remaining amount is provided in the current detection circuit 30.

According to the present invention, the value of the discharge current flowing through the power supply line can be accurately calculated without being affected by the gain error of the amplifier or the output error of the AZD converter, The remaining battery capacity of the battery connected to the power line can always be accurately calculated.

Claims

The scope of the claims

1. Supply the data indicating the amount of discharge current flowing to the power supply line connected to the battery and having the current detection resistor element arranged in the middle to the remaining amount detection device that calculates the remaining amount of the battery. In the current detection device that

A reference voltage generating circuit for generating a reference voltage;

An AZD conversion circuit that generates first data corresponding to a voltage between terminals of a current detection resistance element arranged in the middle of the power supply line and second data corresponding to the reference voltage. A current detector characterized by the above-mentioned.

2. A selection circuit for selectively supplying the inter-terminal voltage of the current detection resistance element and the reference voltage to the AZD conversion circuit, wherein the A_D conversion circuit includes the first and second data The current detection according to claim 1, wherein the current is generated in a time-division manner.

3. The claim 1 or claim 2, further comprising an amplifier circuit for amplifying the inter-terminal voltage of the current detecting resistance element and the reference voltage, and supplying the amplified voltage to the A / D conversion circuit. Item 3. The current detection device according to Item 2.

4. In the system that detects the remaining battery power,

A current detection device that is connected to the battery and generates data representing a discharge current amount flowing through a power supply line having a current detection resistance element arranged in the middle thereof,

-A reference voltage generating circuit for generating a reference voltage;

The current detection device including an AZD conversion circuit that generates first data corresponding to a voltage between terminals of the current detection resistance element and second data corresponding to the reference voltage;

A remaining amount detection device that calculates the amount of discharge current based on the first and second data, and integrates the calculated amount of current to calculate a remaining amount of the battery. Detection system.

5. The current detection device further includes a selection circuit that selectively supplies the inter-terminal voltage of the current detection resistance element and the reference voltage to the AZD conversion circuit, wherein the AZD conversion circuit is configured to output the first voltage. And outputting the second data in a time-sharing manner.

The remaining amount detection system according to 4.

6. The current detection device further includes an amplifier circuit that amplifies the inter-terminal voltage of the current detection resistance element and the reference voltage, and supplies the amplified voltage to the AZD conversion circuit. Item 4. The remaining amount detection system according to item 4 or 5.

7. The current detection device and the remaining amount detection device are mounted on different devices connected by a communication line,

The current detection device further includes an output circuit for format-converting the first and second data and outputting the converted data to the communication line,

The remaining amount detection system according to any one of claims 4 to 6, wherein the remaining amount detection device receives the first and second data via the communication line.

8. An electronic device operable by a battery,

A power line connected to the battery;

A current detection resistance element arranged in the middle of the power supply line;

A reference voltage generating circuit for generating a reference voltage;

A selection circuit connected to the resistance element for current detection and the reference voltage generation circuit, for selecting a voltage between terminals of the resistance element for current detection and the reference voltage in a time division manner, a first circuit corresponding to the voltage between terminals; An AZD conversion circuit that generates digital data and second digital data corresponding to the reference voltage;

An electronic apparatus comprising: a remaining amount detection device that calculates a remaining amount of the battery using a ratio of the first digital data and the second digital data.

9. Amplify and amplify the inter-terminal voltage of the resistance element for current detection and the reference voltage 9. The electronic device according to claim 8, further comprising an amplifier circuit that supplies a voltage to the AZD conversion circuit.

10. The battery is rechargeable, and the remaining amount detecting device measures the remaining amount of the battery when the battery is charged, and the remaining amount detecting device uses the ratio to supply the power. 9.The current amount of the battery is calculated by calculating the amount of discharge current flowing through the line, integrating the calculated amount of discharge current, and subtracting the integrated amount of discharge current from the remaining amount of the battery at the time of charging. Electronic device as described.