JPH08205410A - Battery voltage detector for electric apparatus - Google Patents

Abstract

PURPOSE: To provide a battery voltage detector for an electric apparatus in which the consumption of the battery can be delayed. CONSTITUTION: A stabilized power source 6 for removing the ripple of an external power source is connected to the positive terminal 5 of a jack 2, and a DC/DC converter 7 for stepping up an input voltage to 4V and supplying it to respective parts is provided at the output side of the power source 6. The positive electrode of a battery 1 is connected to the output side of the power source 6, and the negative electrode is connected to the contact 4 of the jack 2. When an AC adapter is attached to or detached from the jack 2, the contact 4 is brought into contact with or separated from a negative terminal 3. A battery voltage detector 8A inputs the positive and negative potentials of the battery 1 to first and second A/D converters 16, 17 via first and second voltage dividers 14, 15, and individually A/D converts it. The difference of the outputs of the converters 16, 17 is calculated by a digital calculator 18 to obtain a battery voltage. A controller 13 displays the battery discharge mark at a display unit 11 when the battery voltage is a predetermined value or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery voltage detecting circuit for an electric device, and more particularly to a battery voltage detecting circuit for an electric device such as a portable AV device which can use both a battery and an external power source.
The present invention relates to a battery voltage detection circuit of an electric device suitable for performing a warning when a battery is almost dead, a battery charge control, and the like.

[0002]

2. Description of the Related Art In many cases, electric equipment such as portable AV equipment that operates on a DC power supply uses both an external power supply using a battery and an AC adaptor. FIG. 2 shows a conventional power supply system of a dual power supply type electric device. 1 is a battery that generates 2.4V in two cells connected in series (here, a rechargeable secondary battery), 2 is a power output terminal of an AC adapter (not shown), which is detachably connected It is a jack as an external power source input terminal for inputting an external power source of DC 5.4V formed by an AC adapter. The negative terminal 3 having a spring property of the jack 2 is connected to the GND of the device. When the power output terminal of the AC adapter is not connected to the jack 2, the negative terminal 3 is connected to the contact 4 of the jack 2, and when the power output terminal of the AC adapter is connected, the negative terminal 3 and the contact 4 are open. It becomes a state. A stabilized power supply circuit 6 for removing a ripple of an external power supply voltage and outputting DC 3.9V is connected between the positive terminal 5 of the jack 2 and GND, and an output side of the stabilized power supply circuit 6 is connected to the stabilized power supply circuit 6. A DC / DC converter 7 is provided that boosts the input voltage to 4V and supplies power to the load of each part. The positive electrode of the battery 1 is connected to the output side of the stabilized power supply circuit 6, and the negative electrode is the contact 4 of the jack 2.
Connected with.

When the power output terminal of the AC adapter is not connected to the jack 2, the negative terminal 3 comes into contact with the contact 4, and the DC / DC converter 7 turns on based on the voltage of the battery 1.
A voltage of V is formed and power is supplied to each part. Conversely, Jack 2
When the power output terminal of the AC adapter is connected to the negative terminal 3, the negative terminal 3 separates from the contact 4, and the DC / DC converter 7 forms a voltage of 4V based on the voltage obtained by stabilizing the external power source by the stabilizing power circuit 6. Power each part.

By the way, when the secondary battery drops below the final voltage of 1 V per cell due to discharge, its performance is significantly deteriorated.
For example, the number of times charge and discharge can be repeated decreases from 500 to 300. Therefore, the electric device of FIG. 2 is provided with a battery voltage detection circuit 8, and when the voltage of the battery 1 detected by this circuit is compared with a predetermined reference voltage by the controller 10 of the microcomputer configuration, and the voltage becomes equal to or lower than the reference voltage. On display 1
1, a warning is displayed, and a charging circuit (not shown) is operated to charge the battery 1.

The battery voltage detection circuit 8 is mainly composed of an operational amplifier 9. The negative electrode of the battery 1 is connected to the inverting input terminal via the resistor R1, and the positive electrode is connected to the non-inverting input terminal via the resistor R1. Has been done. The output terminal of the operational amplifier 9 is connected to the inverting input via the feedback resistor R2, and the non-inverting input terminal is connected to GND via the resistor R2. According to the battery voltage detection circuit 8 configured as above, assuming that the positive potential of the battery 1 is V + and the negative potential of the battery is V-, whether the jack 2 is connected to the power output terminal of the AC adapter or not. Irrespective of whether the contact 4 is connected to the negative terminal 3 or open, the output voltage V _OUT is As described above, a value proportional to the voltage between both electrodes of the battery 1 can be detected.

The controller 10 is an A / D converter 12
V _OUT is A / D converted and digital voltage value V _OUT '
After that, the control unit 13 compares it with a predetermined digital reference voltage value V _C ′ (V _C ′ is set to V _OUT ′ when the voltage between both electrodes of the battery 1 is 2 V), and the reference voltage value V _c
When it is less than ′, the battery indicator is displayed on the display unit 11. When the electric device is equipped with a charging circuit for the battery 1, the charging circuit is turned on, and the battery 1 is charged by the charging circuit when the power output terminal of the AC adapter is connected to the jack 2.

[0007]

In the battery voltage detecting circuit 8 described above, both the CMOS type and the bipolar transistor type can be used for the operational amplifier 9, but the CMOS type is extremely expensive. Therefore, in the past, an inexpensive bipolar transistor type was used for the operational amplifier 9. However, the operational current I _{1 of} the bipolar transistor type operational amplifier 9 is 3.5.
Since the conversion efficiency of the input / output current by the DC / DC converter 7 is about 50% when the AC adapter is not used, the current consumption of the battery 1 due to I ₁ is about 7 mA. Will become a big thing. Therefore, there is a problem that the battery 1 is consumed quickly and the continuous operation time by the battery 1 is shortened. The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a battery voltage detection circuit for an electric device that can delay battery consumption.

[0008]

In the battery voltage detection circuit for electric equipment of the present invention, the battery, the external power supply input terminal, and the negative electrode of the battery are connected to GND when the external power supply is not connected to the external power supply input terminal. And a connecting / opening means for connecting and disconnecting the negative electrode of the battery from GND when the external power source is connected to the external power source input terminal, and forming a predetermined power source voltage from the positive electrode side of the external power source input terminal or the external power source. In an electrical device in which the positive side of the battery is connected to the output side of the power circuit,
A first A / D conversion unit for A / D converting the positive electrode potential of the battery, a second A / D conversion unit for A / D converting the negative electrode potential of the battery, a first A / D conversion unit and a first A / D conversion unit. Digital operation means for calculating the battery voltage by digitally calculating the difference between the outputs of the two A / D conversion means.

The battery voltage detection circuit for another electric device of the present invention is characterized in that the voltage dividing means is provided before the first A / D converting means or the second A / D converting means.

[0010]

According to the battery voltage detection circuit for electric equipment of the present invention, the positive electrode potential of the battery is A / D converted by the first A / D conversion means, and the negative electrode potential of the battery is second A / D converted. Means for A / D conversion, and digital operation means for the first A
The battery voltage is detected by obtaining the difference between the outputs of the / D conversion means and the second A / D conversion means. As a result, the first and second A /
As the D conversion means and the digital operation means, those having a small operating current, such as CMOS type, can be used, so that the battery consumption can be greatly suppressed as compared with the conventional operational amplifier, and the continuous operation time of the electric equipment can be reduced. Can be lengthened.

According to the battery voltage detection circuit of another electric device of the present invention, the positive or negative electrode potential of the battery is divided by the voltage dividing means and then divided into the first A / D converting means or the second A / D means.
Input into the conversion means. As a result, the first A / D conversion means or the second
Even if the dynamic range of the A / D conversion means is narrow, the battery voltage can be accurately detected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of a power supply system of a dual power supply type electric device according to an embodiment of the present invention. The same components as those in the conventional example shown in FIG. 2 are designated by the same reference numerals. 1
Is a rechargeable battery that can be repeatedly charged and discharged, 2 is a jack as an external power supply input terminal to which a DC 5.4V power supply output terminal of an AC adapter is detachably connected, 6 is a ripple of the external power supply voltage, A stabilized power supply circuit that outputs a DC voltage of 3.9V, and a DC / DC converter 7 that boosts the input voltage to 4V and supplies power to the load of each part. 10A is DC /
The controller 10A is a microcomputer-configured controller that operates by supplying 4V from the DC converter 7, and the controller 10A has a part of a battery voltage detection function as described later.

Reference numeral 14 is a first voltage dividing circuit composed of resistors R1 and R2, and 15 is a second voltage dividing circuit composed of resistors R1 and R2.
Reference numeral 16 is a first A / D converter for A / D converting the positive electrode side potential of the battery 1 divided by the first voltage dividing circuit 14, and 17 is the battery 1 divided by the second voltage dividing circuit 15. A second A / D converter for A / D-converting the negative-electrode side potential of the digital converter, 18 is a digital arithmetic unit composed of a hard circuit,
The difference between the outputs of the A / D converters 16 and 17 is digitally calculated and output to the control unit 13 as the detected voltage of the battery 1. First and second voltage dividing circuits 14 and 15, first and second A
The / D converters 16 and 17 and the digital operation unit 18 constitute a battery voltage detection circuit 8A. The first and second voltage dividing circuits 14 and 15 are provided to supplement the dynamic range of the first and second A / D converters 16 and 17 when the positive electrode side potential and the negative electrode side potential of the battery 1 are relatively high. It is a thing. The other components are the same as those in FIG.

Next, the operation of the above embodiment will be described.
Now, assuming that the positive electrode potential of the battery 1 is V ₊ and the negative electrode potential is V ₋ , regardless of whether the power output terminal of the AC adapter is connected to the jack 2 (the contact 4 of the jack 2 and the negative terminal 3 are connected). Irrespective of whether it is in the open state or the open state), the output VOUT 'of the digital calculation unit 18 is As described above, a value proportional to the voltage between both electrodes of the battery 1 can be detected.

The controller 13 of the controller 10A controls the digital voltage value V _OUT ′ input from the digital calculator 18.
Is a predetermined digital reference voltage value V _C ′ (V _C ′ is the battery 1
Is set to V _OUT ′ when the voltage between the two electrodes is 2 V), and when the reference voltage value is below V _c ′, the indicator 11 displays the dead battery mark. When the electric device is equipped with a charging circuit for the battery 1, the charging circuit is turned on, and the battery 1 is charged by the charging circuit when the power output terminal of the AC adapter is connected to the jack 2.

According to this embodiment, the first and second A / Ds
By using a CMOS type with a small operating current for the converters 16 and 17 and the digital operation unit 18, the current consumption of the battery 1 is reduced by nearly 7 mA compared to the case where an operational amplifier as in the past is used, and battery consumption is greatly suppressed. Therefore, the continuous operation time of the electric device can be extended.
In addition, after dividing the positive electrode side potential and the negative electrode side potential of the battery 1 by the first and second voltage dividing circuits 14 and 15, the first and second A / D
Since the signals are input to the converters 16 and 17, the first and second A / A ratios are higher than those of the positive electrode side potential and the negative electrode side potential of the battery 1.
Even if the dynamic range of the D converters 16 and 17 is narrow, it is possible to accurately detect the battery voltage.

In the above embodiment, the digital arithmetic unit 18 is composed of a hard circuit, but it may be realized by software processing of a microcomputer. In this case, the controller can be composed of an inexpensive one-chip microcomputer with a built-in A / D converter. Further, when the dynamic range of the first and second A / D converters 16 and 17 is sufficient as compared with the positive and negative potentials of the battery 1, the first and second voltage dividing circuits 14 and 15 are Either one or both can be omitted.

[0018]

According to the battery voltage detection circuit for electric equipment of the present invention, the positive electrode potential of the battery is converted into A / D by the first A / D conversion means.
Along with the D conversion, the negative electrode potential of the battery is A / D converted by the second A / D conversion means, and the first by the digital operation means.
Since the battery voltage is detected by obtaining the difference between the outputs of the A / D conversion means and the second A / D conversion means, the first and second A / D conversion means and the digital calculation means are C
Since a MOS type or the like having a small operating current can be used, the battery consumption can be greatly suppressed and the continuous operation time of the electric device can be lengthened as compared with the case of using the conventional operational amplifier.

According to the battery voltage detection circuit of another electric device of the present invention, the first A / D conversion means or the second A / D conversion means or the second A / D conversion means is used after the positive electrode potential or the negative electrode potential of the battery is divided by the voltage dividing means.
Input to the / D conversion means. Accordingly, the battery voltage can be accurately detected even when the dynamic range of the first A / D conversion unit or the second A / D conversion unit is narrower than the positive electrode potential or the negative electrode potential of the battery.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply system of a dual power supply type electric device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a power supply system of a conventional two-power-source electric device.

[Explanation of symbols]

1 Battery 2 Jack 3 Negative Terminal 4 Contact 5 Positive Terminal 6 Stabilized Power Supply Circuit 7 DC / DC Converter 8A Battery Voltage Detection Circuit 10A Controller 11 Indicator 13 Control Unit 14 First Voltage Dividing Circuit 15 Second Voltage Dividing Circuit 16 First A /
D converter 17 Second A / D converter 18 Digital operation unit

Claims (2)

[Claims] 1. A battery, an external power supply input terminal, and when the external power supply is not connected to the external power supply input terminal, the negative electrode of the battery is connected to GND, and the external power supply is connected to the external power supply input terminal. An electric device having a connection / opening means for opening the negative electrode of the battery from the GND, and the positive electrode side of the battery being connected to the positive electrode side of the external power supply input terminal or the output side of the power supply circuit for forming a predetermined power supply voltage from the external power supply. A first A / D converting means for A / D converting the positive electrode potential of the battery, a second A / D converting means for A / D converting the negative electrode potential of the battery, and a first A / D converting means And a digital calculation means for calculating a battery voltage by digitally calculating the difference between the outputs of the second A / D conversion means, and a battery voltage detection circuit for an electric device. 2. A first A / D conversion means or a second A / D
2. The battery voltage detection circuit for an electric device according to claim 1, wherein a voltage dividing means is provided before the D conversion means.