JPH04141715A - Battery backup device - Google Patents

Abstract

PURPOSE:To surely judge whether an electric circuit backed up by a battery is normal or not at the time of power restoration by providing a monitor circuit which monitors the voltage value of the battery voltage at the time of battery backup and storing the reduction of the battery voltage. CONSTITUTION:When a power source is turned off, circuit parts 10 and 11 are operated by the battery. A second voltage monitor part 13 monitors the battery voltage; and when detecting that the battery voltage is so reduced that the operation normalcy of the first circuit part 10 cannot be kept, this monitor part 13 writes this state in the second circuit part 11. Normalcy data stored in the second circuit part 11 is read out at the time of power restoration. Thus, it is surely judged whether the electric circuit backed up by the battery is normal or not at the time of power restoration.

Description

[Detailed Description of the Invention] [Summary] Regarding a battery backup device that upgrades electrical circuits when the power is turned off, the present invention enables reliable determination of the normality of the electrical circuit backed up by the battery when the power is restored. A first circuit section that is backed up by a battery when the power is turned off, a second circuit section that records whether the contents of the first circuit section are normal or not, and a second circuit section that records whether the contents of the first circuit section are normal or not when the power is turned on. a first voltage monitoring unit that continues/cancels the reset request state; and a voltage monitoring unit that monitors the voltage to ensure the normality of the contents of the first circuit unit in a power-off state, and issues a reset request when the voltage drops. a second voltage monitoring unit that performs the reset operation, and only when a reset request is received from both voltage monitoring units in response to a reset request of the first voltage monitoring unit and the second voltage monitoring unit, the second voltage monitoring unit and a gate circuit configured to reset the second circuit section.

[Field of Industrial Application] The present invention relates to a battery backup device that backs up an electric circuit even when the power is cut off, and more specifically, it monitors the voltage value of a backup battery to determine whether the electric circuit backed up by the battery is normal or not. This invention relates to a battery backup device that can determine when power is restored.

[Prior Art] Conventionally, in order to guarantee the operation of an electric circuit, backup with a battery has been carried out to ensure the operation even when the power is cut off. FIG. 3 is a conceptual diagram of the battery backup method. The voltage from the battery is diode D1
The voltage from the power supply is supplied to the memory 1 via the diode D2. Normal electric circuit 2 is powered only by a power source.

In a circuit configured as described above, when the power is normally turned on, if the power supply voltage is set to be slightly higher than the battery voltage, the diode D1 is turned off and the diode D2 is turned on. As a result, the memory 1 is supplied with power only from the power supply, and the electric circuit 2 is also supplied with power from the power supply. Then, data is written into the memory 1 from the electric circuit 2 as necessary.

Here, it is assumed that the power supply is cut off for some reason. At this moment, diode D] is turned on, and power is supplied to memory 1 from the battery. Needless to say, the electric circuit 2 does not operate because no power is supplied to it. In this way, when the power is turned off, only the memory 1 is backed up by the battery and the written data is retained.

As a method for determining whether or not backup is being performed normally when power is restored from such battery backup, the following method has conventionally been used.

■Memory data continuous writing method As shown in Figure 4, a data writing area 1a is provided in memory 1 for writing certain data, data is written in that area, and when the power is restored, the contents This method reads out the data and confirms its contents. If the read content matches the previously written content, it is determined that the normality of the memory 1 is maintained.

■Battery voltage monitoring method As shown in Figure 5, this is a method in which a voltage monitoring section 3 is provided to measure the battery voltage during battery backup, and the voltage monitoring section 3 monitors the battery voltage. . In this case, the threshold value for determining voltage abnormality is set to the very edge of the guaranteed operation range in which the memory 1 operates.

[Problems to be Solved by the Invention] The above memory data reading method (2) has a problem in that it does not guarantee that the entire memory really operates normally. In other words, even if the data in the data write area 1a of the memory 1 is normal, there is a problem in that the data in other areas may be destroyed. Also, the above ■
In the battery voltage monitoring method, even if the power supply voltage fluctuates temporarily during normal voltage operation, the voltage monitoring unit 3
The problem is that it reacts. Generally, there is a problem in that a power supply abnormality is determined even though power supply fluctuations of this degree often do not pose a problem in a normal operating state using a power supply.

In addition, in this type of system, the circuit is often equipped with a voltage monitoring circuit to control the reset sequence when the power is turned on, and when the power is restored from a perfect backup state, there is no possibility that the backup state has been maintained in some way. It is necessary to prevent the circuit from resetting.

The present invention has been made in view of these problems, and provides a battery backup device that can reliably determine whether or not an electric circuit backed up by a battery is normal when power is restored. It is intended to.

[Means for Solving the Problems] FIG. 1 is a block diagram of the principle of the present invention. Components that are the same as those in FIG. 3 are designated by the same reference numerals. In the figure, 10
is the first one backed up by the battery when the power is cut off.
1] is a second circuit section that records whether the contents of the first circuit section 10 are normal; 12 is a first voltage monitor that continues/cancels the reset request state when the power is turned on; and 13 are connected to the first circuit section 10 in a power-off state.
a second voltage monitoring unit that monitors the voltage to ensure the normality of the contents of the unit and requests a reset when the voltage drops;
4 is the first voltage monitoring section] 2 and the second voltage monitoring section 13
only when a reset request is received from both voltage monitoring units 12 and 13 in response to a reset request from the first circuit unit
This is a gate circuit configured to reset -〇 and the second circuit section 11.

[Function] When the power is turned off, the circuit section 10, 1.1 starts to operate automatically. Here, the second voltage monitoring section 11
monitors the battery voltage, and the voltage is the first.
If it is detected that the operation of the second circuit section]0 has deteriorated to such an extent that normality of operation cannot be maintained, this fact is written in the second circuit section. Therefore, by reading the normality data stored in the second circuit section 1 when the power is restored, it is possible to reliably determine the normality of the operation of the first circuit section 0 during battery backup.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. Components that are the same as those in FIG. 1 are designated by the same reference numerals. In the figure, SWI and SW2 are power on/off switches that operate in conjunction with each other. DI and D2 are power switching diodes connected in series with a battery or a power source.

10 is a first circuit section backed up by a battery when the power is cut off, such as a memory such as a RAM; 11 is a memory such as a RAM;
[Circuit unit] A second circuit unit that maintains that the contents of O are normal, and here it is a set/reset (R3) flip-flop. ] 2 is a voltage monitoring unit that continues/cancels the reset request state when the power is turned on; ] 3 is a voltage monitoring unit that monitors the voltage in order to ensure the normality of the contents of the first circuit unit] O when the power is turned off; This is the second voltage monitoring unit that performs the following steps and requests a reset when the voltage drops. For example, dedicated ICs may be used as these voltage monitoring units 12 and 13. Here, the second voltage monitoring section 13 needs to be highly accurate in order to accurately measure the voltage at which the memory reaches zero or becomes inoperable.

14 is the first voltage monitoring section 12 and the second voltage monitoring section 1
In response to the reset request of 3, both voltage monitoring units 12 and 13
A gate circuit is configured to reset the first circuit section 10 and the second circuit section 11 only when a reset request is received from the gate, and an AND gate is not shown here. 15 is a flip-flop that receives a reset signal from the AND gate]4; 16 is a memory control section that receives a reset signal from the flip-flop]5. The memory control unit 16 includes a refresh circuit and the like in the case of memory]0 or dynamic RAM, for example.

For example, a cent signal is directed to the set input of the flip-flop 1, which is the second circuit section, from a program or a hardware circuit (for example, the electric circuit 2 in FIG. 3) that operates using a separate power source. A reset signal from the flip-flop 15 is applied to its reset input. Also,
The output of the AND gate 14 is connected to the reset input of the flip-flop 15. The operation of the circuit configured as described above will be explained as follows.

First, the switches SWI and SW2 are turned on to turn on the power. When the power is turned on for the first time, both the first and second voltage monitoring sections 11.13 issue a reset request to reset and initialize the memory 10 and the flip-flop 11. At this time, the reset signal from each voltage monitoring section 12.13 is output at "0" level. Both of these reset signals are inverted at the input of the AND gate ]4 and become "1". As a result, the output of the ant gate 14 becomes "1" or is inverted and becomes "0", resetting the flip-flop 15. The reset signal of this flip-flop 15 is given to the memory control section 16 and the flip-flop 11 at "0 level" from its Q output.The memory control section 16 initializes the memory 10. If there is no input, it is naturally not necessary to reset the foot flop 15.

Thereafter, as the power supply voltage rises, the reset state is released, power is supplied from the power supply, and the memory 10 performs a predetermined function. In this state, the second circuit section 11 (flip-flop 11) is set to a normal state. As described above, the setting method can be performed using software such as a program or hardware. When set, the Q output of the flip-flop 11 becomes "1" indicating normality.

Even if the second voltage monitoring unit 13 momentarily detects a drop in the power supply voltage and issues a reset request during operation using the power supply, the first voltage monitoring unit 12 does not issue a reset request, so the AND gate 14 does not issue a reset signal. Therefore, the circuit does not respond to temporary fluctuations in the power supply voltage while operating on the power supply.

Here, when the power is turned off, power is supplied to the parts other than the first voltage monitoring section 2 from the battery.

Further, the first voltage monitoring unit 12 is always in the reset request state (
"0" level), and the AND gate 14 is opened. During battery backup, the second voltage monitoring unit 13
If a voltage drop in the battery is detected, a reset request is issued. This reset request enters the reset power R3T of the flip-flop 15 via the AND gate 14 and resets the flip-flop 15. As a result, the reset signal of flip-flop 15 is
1 and enters memory 16. Therefore, flip-flop 11
is reset and its Q output becomes "0" indicating an abnormal state. In this way, if the voltage of the battery during battery backup drops even once, the flip-flop 11
The Q output of will indicate an abnormal condition.

If the power is restored due to battery backup or normal operation, the first voltage monitoring unit 2 will issue a normal reset request when the power is turned on again, but the second voltage monitoring unit 3 will issue a set request. Therefore, the AND gate 14 remains closed and the flip-flop 11 is not reset. The programmer reads the Q output of the flip-flop 11 and determines the normality of the memory 10. When the Q output is "1", it is determined that the data stored in the memory 10 is normal. Here, if the flip-flop 11
If the Q output of the flip-flop 11 is "0", it can be seen that the normality of the memory is not guaranteed during battery backup.In this way, by reading the Q output of the flip-flop 11 when the power is restored, It is possible to reliably determine the normality of the memory 10 during battery backup.

In the above embodiment, a memory is used as the first circuit section 10, but the present invention is not limited to this. Any type of circuit may be used as long as it requires battery backup when the power is turned off.

[Effects of the Invention] As described above in detail, according to the present invention, a monitoring circuit is provided to monitor the voltage value of the battery voltage during battery backup, and a decrease in the battery voltage is memorized. This makes it possible to reliably determine whether the electrical circuit backed up by the battery is normal or not when the power is restored. Therefore, according to the present invention, the normality storage circuit (second circuit section 11 in FIG. 1) in the backup state is prevented from being reset due to malfunction of the voltage monitoring section in the normal state, and when the power is restored, It is possible to prohibit resetting of the backup part of the battery and improve the accuracy of guaranteeing normality during battery backup.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram of a configuration showing an embodiment of the present invention, Figure 3 is a conceptual diagram of battery backup, and Figure 4 is an explanatory diagram of a conventional normality confirmation method. , FIG. 5 is an explanatory diagram of a conventional normality confirmation method. In FIG. 1, 10 is a first circuit diagram, 11 is a second circuit diagram, 12 is a first voltage monitoring circuit, 13 is a second voltage monitoring circuit, 14 is a gate circuit, Dl, D2 are diodes It is.

Claims (3)

[Claims] (1) A first circuit section (10) that is backed up by a battery when the power is turned off, and a second circuit section (11) that records whether the contents of the first circuit section (10) are normal. and the first one that continues/cancels the reset request state when the power is turned on.
a voltage monitoring section (12); and a second voltage monitoring section (12) that monitors the voltage in order to ensure the normality of the contents of the first circuit section (10) in a power-off state and requests a reset when the voltage drops. a monitoring section (13), the first voltage monitoring section (12) and the second voltage monitoring section (1
3) In response to the reset request, both voltage monitoring units (12)
, (13), and a gate circuit (14) configured to reset the first circuit section (10) and the second circuit section (11) only when there is a reset request from the circuit section (13). battery backup device. (2) The battery backup device according to claim 1, wherein a memory is used as the first circuit section (10). (3) In addition to increasing the voltage monitoring accuracy of the second voltage monitoring unit (13), when the voltage value of the battery voltage drops below the reference value during power-off, a reset request is made and the second circuit unit 2. The battery backup device according to claim 1, wherein a decrease in battery voltage is recorded in (11).