JPH0634728A - Battery voltage detection device - Google Patents

Abstract

(57) [Summary] [Purpose] To be able to accurately detect the remaining amount of the backup battery. [Constitution] The battery voltage detection device 1 outputs a discharge command A for switching the battery from charging to discharging to the charging circuit 13 after the power is turned on or after the power is restored, and based on the detection signal detected during the discharging state. Low battery LED
A CPU 11 that outputs a control signal that drives 16;
When the power is restored and the discharge command A is input from the CPU 11, the battery 14 is discharged for a certain period of time, and the battery 1 in the discharged state is discharged.
Charging circuit 1 that detects the output voltage of 4 and outputs a detection signal
3, the battery 14 is switched from charging to discharging and the LOW battery is detected during discharging when the system starts operating with the AC power after the power is turned on or the power is restored.

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 device, and more particularly to an electronic cashless register (ECR),
The present invention relates to a battery voltage detection device used in an electronic device such as a POS terminal and detecting the voltage of a backup battery of a memory of the electronic device, for example.

[0002]

2. Description of the Related Art The characteristics of Ni-Cd batteries are good large current characteristics, excellent low temperature characteristics, long cycle life, strong overcharge, and easy maintenance. Therefore, it is used for applications requiring high reliability, such as backup power supplies for communication and emergency. In addition, since the Ni-Cd battery can be used as a charger with a relatively simple circuit as compared with a lead battery, it is often used for applications with a small battery capacity and is widely used as a general storage battery. . As a method of charging such a storage battery, for example, there is a floating method. This method charges and discharges a battery and a load connected in parallel, and is used for battery backup of memory when the power is cut off. Conventionally, as a method of detecting the remaining amount (remaining capacity) of the backup battery, for example, by detecting the voltage of the battery while charging the battery,
When the remaining amount becomes lower than the voltage that can be held in the memory, the LOW battery is displayed by the LED or the like.

[0003]

However, in such a conventional battery voltage detecting device, since the voltage during charging is detected, an accurate battery can be obtained due to a change in charging characteristic due to a temperature change or the like. Since the remaining capacity may not be detected, a battery with a large battery capacity must be used in order to reliably perform battery backup while considering this, and this has the drawback of increasing the size and cost of the entire system. It was Hereinafter, the reason for detecting the battery voltage during charging and its drawbacks will be described in more detail. In general, EC
The discharge current of the backup battery of the R and POS terminals is about 0.001 CA, and the charging method is trickle charging.
The discharge characteristics of the battery are very complicated, but the discharge current is 0.
When it is 1 CA or less, only the influence of the ambient temperature needs to be considered. Further, it is known that the discharge characteristics are considerably different depending on the ambient temperature, and at any temperature, when the voltage of one cell reaches 1.1V, it immediately drops to 0V. Therefore,
Although it is easy to detect low voltage, it is meaningless to detect the voltage of the battery during discharging because the detection result cannot be held if the backup voltage is exhausted during discharging of the backup battery (that is, during power failure). It is said that. On the other hand, the charging characteristic is more complicated than the discharging characteristic, but if it is limited to trickle charging, only the influence of the ambient temperature needs to be considered. The charging characteristics vary considerably depending on the ambient temperature, and when the remaining capacity is 0, the voltage of one cell becomes 1.35V at 0 ° C.
It becomes 1.23V at 40 ° C. Voltage is 0.35 at 40 ℃
It becomes V when the remaining capacity is 80%. Therefore,
It is difficult to accurately perform LOW battery detection that detects whether or not the memory such as RAM kept the voltage that can be held during a power outage, and the conventional LOW battery detection has a large remaining capacity at high temperature and the memory can be held. Nevertheless, it is recognized as a LOW battery. Therefore, there is a drawback in that a battery having a capacity larger than that required by the system must be mounted. An object of the present invention is to make it possible to accurately detect the remaining amount of the backup battery.

[0004]

The means of the present invention are as follows. The battery is a battery for backing up the memory of a battery device such as a POS terminal, for example, a Ni-
It is a secondary battery such as a Cd battery. The charging voltage supply means is a power supply circuit or the like for supplying a predetermined charging voltage to the battery. The power recovery detection means is a CPU that detects the rise of the power of the electronic device when the power is turned on or the power is restored.
Etc. The battery discharging means puts the battery in a discharging state in response to the detection of the power restoration detecting means, and for example, CP
This is performed by turning on / off a switch such as a transistor provided in the charging path of the battery according to a control signal from U. The voltage detection means is a circuit for detecting the output voltage of the battery when the battery is discharged by the battery discharge means, such as an operational amplifier.

[0005]

The operation of the means of the present invention is as follows. A predetermined charging voltage is supplied to the battery for backing up the memory etc. by the charging voltage supply means. In this state, when the electronic device is powered on or restored from a power failure, the power source restoration detecting unit detects the rise of the power source, and the battery discharging unit puts the battery in a discharging state in response to the detection of the power source restoration detection. Then, the output voltage of the battery is detected by the voltage detecting means in the discharging state. Therefore,
It is hardly affected by temperature characteristics, and the remaining battery level of the backup battery can be detected accurately.

[0006]

EXAMPLES Examples will be described below with reference to FIGS. 1 to 4 are diagrams showing an embodiment of a battery voltage detecting device. First, the configuration will be described. FIG. 1 is an overall configuration diagram of a battery voltage detection device. In this figure, 11 is a CPU that executes a battery voltage detection processing control (FIG. 4) described later, and the CPU 11 switches the charging circuit 13 (described later) from charging to discharging the battery for a certain time after the power is turned on or after the power is restored. The discharge command A is output, and the low battery LED 16 is output based on the detection signal detected during the discharge state.
A control signal for driving (described later) is output.

The power supply 12 is a charging circuit 1 when the AC power is input.
3 is supplied with a power supply voltage Vc (for example, 30 V), and a power supply voltage V _cc (for example, 5 V) corresponding to a backup voltage V _BUP for backing up a memory 15 (described later) is supplied (see the timing chart of FIG. 3). ). The charging circuit 13 charges the battery 14 (described later) with the supply voltage Vc from the power supply 12 when there is an AC input, and also outputs the supply voltage Vcc as the backup voltage V _BUP , and when there is no AC input, the power supply of the battery 14 Is output as a backup voltage V _BUP , and when the AC power is restored and the discharge command A is input from the CPU 11, the battery 14 is discharged for a certain period of time, and the output voltage of the battery 14 in the discharging state is detected to detect a detection signal. Is output (see the timing chart in FIG. 3).

The battery 14 is a battery such as Ni-Cd for backing up the memory 15 by supplying the backup voltage V _BUP to the memory 15 when the power source 12 has no AC input.

The memory 15 is a memory such as a RAM which is built in an ECR, a POS terminal or the like and which is backed up by a battery with a backup voltage V _BUP . The low-battery LED 16 is turned on by a notification signal from the CPU 11 indicating that the battery voltage has dropped below a specified level, and the low battery LED 16 is turned on.
Indicates that the is in a low battery state.

The output voltage Vc of the power source 12 is a voltage of 30V when there is an AC input, and is 0V when there is no AC input. In addition, Vcc is a power source that has a voltage of 5 V when there is an Ac input and 0 V when there is no Ac input, and is not backed up even in the event of a power failure.
It is a power source for LSI such as PU and ROM. Further, the backup voltage V _BUP output from the charging circuit 13 is a voltage of approximately Vcc when there is an Ac input, and is a battery voltage when there is no Ac input. Power supply for the LSI.

FIG. 2 is a circuit diagram of the charging circuit 13. In FIG. 2, the charging circuit 13 is supplied with the voltage Vc from the power supply 12, and is turned on / off by turning on / off the transistor G2 to supply the power supply voltage Vc to the battery 14, and the discharge command A from the CPU 11.
(See FIG. 3A) to turn on / off the transistor G
1, a transistor G2 that turns ON / OFF, an operational amplifier OP that outputs a detection signal by comparing the output voltage of the battery 14 in the discharge state with the reference value output from the reference value generation circuit 21, and resistors R1 and R2. , R3 and diode D
1, D2, D3.

The discharge command A output from the CPU 11 is
As shown in FIG. 3A, the signal at the normal time is the H level,
It is a signal that goes to L level to change the state of the battery 14 from the discharging state to the charging state by the C input and then to keep the battery 14 in the discharging state for a certain time.

Next, the operation of this embodiment will be described. FIG. 4 is a flowchart showing a program for battery voltage detection control, and this flow is executed by turning on the AC power supply. First, in step S1, return AC after power ON or after power failure
When there is an input, the signal level of the discharge command A output to the charging circuit 13 is changed from H level to L level for a certain period of time (for example, 1
00msec) to lower the battery 14 for 100msec
During this period, the battery voltage is detected by switching from charging to discharging. Next, in step S2, it is determined whether or not the battery 14 is in the LOW battery state based on the detection signal of the battery detected during discharging. When it is determined that the battery 14 is in the LOW battery state, in step S3 The battery LED 16 is turned on to notify that the battery voltage has dropped below the specified value, and the process of this flow ends. When it is determined that the battery 14 is in the LOW battery state, the process of this flow ends.

In this way, the battery 14 is put into a discharging state by setting the discharging command A after AC input to the L level, and the voltage of the battery 14 being discharged is discharged. The detection voltage is, for example, 1
If 1.1 V or less per cell, it is determined that the battery is a LOW battery, and the low battery LED 16 is turned on.

Next, the operation of the charging circuit 13 shown in FIG. 2 will be described. The CPU 11 constantly supplies the H level discharge command A to the transistor G2 of the charging circuit 13, and the transistor G2 is in the ON state by the H level discharge command A input via the resistor R2. Transistor G
When the transistor 2 is turned on, the transistor G1 is turned on, and the charging voltage Vc is supplied from the power source 12 to the resistor R1 and the diode D1.
To the battery 14 through. As shown in FIG. 3, the battery 14 has a resistance R when there is an AC input and the voltage Vc rises.
1 is charged, and when there is no AC input and the voltage of the voltage Vc drops, the battery is discharged. Normally, when there is an AC input, the voltages Vc and Vcc are supplied from the power source 12, so these voltages Vc and Vcc are output as they are as the backup voltage V _BUP of the memory 15, and the voltage is supplied from the battery 14. It will not be done. Further, when the power supply switch is turned off or the power supply 12 stops supplying the voltages Vc and Vcc due to a power failure or the like,
The battery 14 is discharged and the battery voltage is output from the battery 14 through the diode D2 and the backup voltage V _BUP is output.
become.

When the CPU 11 detects that the power switch is ON or the recovery from the power failure, the CPU 11 drops the discharge command A, which is always H level and is output to the transistor G2 of the charging circuit 13, to L level for a certain period of time (for example, 100 msec). Then, the transistor G2 is turned off, the transistor G1 is also turned off, and since the voltage Vc is not applied, the battery 14 is in a discharged state as shown in FIG. That is, when the discharge command A becomes L level, the battery 14 is in a discharged state even during AC input. At this time, the voltage Vc of the power source 12
c through diode D3 for backup voltage V _BUP
Is output as. Then, the output voltage of the battery 14 being discharged is detected by comparing with the reference value by the operational amplifier OP, and the detection signal is output to the CPU 11. CPU1
When the detection signal is less than the specified value, 1 determines that the battery is a LOW battery and lights the low battery LED 16.

As described above, the battery voltage detecting device 1
Outputs a discharge command A for switching the battery from charging to discharging for a certain period of time after the power is turned on or after the power is restored, and controls the low battery LED 16 based on the detection signal detected during the discharging state. When the CPU 11 that outputs a signal and the AC power supply recovers and the discharge command A is input from the CPU 11, the battery 14 is discharged for a certain period of time, the output voltage of the battery 14 in the discharged state is detected, and a detection signal is output. With a charging circuit 13, when the system starts operating with AC power after the power is turned on or after a power failure is restored,
Switch the battery 14 from charging to discharging and LOW during discharging
Since the battery is detected, it is possible to detect the battery voltage based on the discharge characteristics that are less affected by the ambient temperature.
Accurate LOW battery detection is possible. Therefore, the battery capacity can be the minimum necessary capacity, and the system can be downsized and the cost can be reduced.

In this embodiment, the detection signal is output by comparing the output voltage of the battery with the reference value by the operational amplifier OP, but any output voltage of the battery can be detected during discharging. It may be something like this.

Needless to say, the transistors and diodes constituting the charging circuit and the types thereof are not limited to those in the above-mentioned embodiments.

[0020]

According to the present invention, the battery is discharged according to the rise of the power source, and the output voltage of the battery is detected at this time, so that the remaining amount of the battery can be accurately detected. The battery capacity of the mounted battery can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a battery voltage detection device.

FIG. 2 is a circuit diagram of a charging circuit of the battery voltage detection device.

FIG. 3 is a timing chart of each part of the charging circuit of the battery voltage detection device.

FIG. 4 is a flowchart of a battery voltage detection process of the battery voltage detection device.

[Explanation of symbols]

11 CPU 12 Power Supply 13 Charging Circuit 14 Battery 15 Memory 16 Low Battery LED A Discharge Command Vc, Vcc Power Supply Voltage V _BUP Backup Voltage

Claims (1)

[Claims] 1. A battery for backing up the power supply of an electronic device, a charging voltage supply means for supplying a predetermined charging voltage to the battery, a power recovery detection means for detecting a rise of the power supply of the electronic device, Battery discharging means for putting the battery into a discharging state in response to detection by the power restoration detecting means, and voltage detecting means for detecting an output voltage of the battery in the discharging state by the battery discharging means, And battery voltage detection device.