JP3396983B2 - Memory backup circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory backup circuit for a facsimile apparatus, a printer apparatus, a copying apparatus, etc., and particularly for a DRAM backup circuit using a secondary battery, which consumes a large amount of current and has a charge / discharge cycle. The present invention relates to a memory backup circuit capable of extending the life of a battery by reducing the battery life.

[0002]

2. Description of the Related Art In a conventional memory backup circuit, a main control circuit and a memory are driven by a power supply from a main power supply circuit. Then, the secondary battery is charged by the power source from the main power source circuit, and when the main power source is turned off, the memory is backed up by the secondary battery. FIG. 4 is a block diagram of a conventional memory backup circuit. The main power supply 13 supplies power to the main control circuit 11 and also supplies power to the voltage detection circuit 12 and the memory 10 through the diode D1. Further, the secondary battery B is connected through the resistor R1 and the switch SW1.
Charge the AT. The Zener diode ZD1 is
A constant voltage circuit for charging the secondary battery BAT with a constant voltage is formed together with the resistor R1. The voltage detection circuit 12 monitors the input voltage, and if it is equal to or higher than a certain voltage, the switch SW1.
Is turned on, and the switch SW1 is turned off if the voltage is below a certain voltage. Normally, when the main power supply 13 is on,
The memory 10 operates by being supplied with power through the diode D1. However, when the main power supply 13 is turned off, power is supplied from the secondary battery BAT to the memory 10 through the switch SW1 and the resistor R1, and the memory 10 is backed up. When the secondary battery BAT is discharged below a certain voltage, the voltage detection circuit 12 turns off the switch SW1 and the backup is stopped. Thereby, over-discharge of the secondary battery BAT can be suppressed. As another conventional example, there is a multifunction telephone described in, for example, Japanese Patent Application Laid-Open No. 2-53352. According to this, a method of supplying power from a secondary battery at the time of power off or momentary interruption is used. . That is, when power is supplied to the circuit section from the commercial power source, the charging operation is performed by simultaneously supplying power to the secondary battery, and the operating state of the rectifier of the commercial power source is monitored to stop or instantaneously When the disconnection occurs, the secondary battery is discharged by switching the power supply switching circuit.

[0003]

By the way, the life of the secondary battery largely depends on the charging / discharging cycle, and there is a problem that the life becomes short when the number of times of charging / discharging is large.
Particularly in recent facsimile machines, since the amount of information that is desired to be backed up is constantly increasing, the number of charge / discharge cycles is increased, which causes a problem that the life of the secondary battery is shortened. On the other hand, for the energy saving mode that reduces power consumption during standby,
Recently, it has been close-up and the demand is increasing. The first object of the present invention is to solve these problems,
An object of the present invention is to provide a memory backup circuit that can reduce the power consumption of a secondary battery by using the energy saving mode. A second object of the present invention is to provide a memory backup circuit capable of extending the life of the secondary battery and detecting whether or not the memory is backed up. Further, a third object of the present invention is to provide a memory backup circuit capable of reducing the cost of the secondary battery and extending the life of the secondary battery.

[0004]

To achieve the above object, a memory backup circuit of the present invention comprises a main power supply (13), a main control circuit (11) supplied with power from the main power supply (13), and a memory. (10) and a backup power supply (BAT) for backing up the memory (10), in a memory backup circuit, the memory (10) is always operated from the main power supply (13).
In addition to the power supply, the main power (13) of said backup power supply (BAT) and a power supply path for supplying power to said memory (10) from a backup power supply (BAT rechargeable secondary battery in the off ) To turn on / off a power supply path for supplying power to the memory from the above), and the first switch (S1).
Voltage detection circuit (12) for controlling on / off of W1)
And a second switch (SW2) installed between the main power supply (13) and the main control circuit (11) to turn on / off the power supply of the apparatus.
In addition, from the main power source (13), the memory (1
0) and a power supply path for supplying power from the backup power supply (BAT) to the memory (10) when the main power supply (13) is off, and a backup power supply for a rechargeable secondary battery. A first switch (SW1) for turning on / off a power supply path for supplying power from (BAT) to the memory, and a voltage detection circuit (1) for controlling on / off of the first switch (SW1).
2), the main power supply (13) and the main control circuit (1
1) a second switch (SW2) installed between the main power supply (13) and the second switch (SW2) for turning on / off the power supply of the apparatus, and the second switch (SW2) according to an external input signal. A power control circuit for controlling the on / off of the switch (SW2) of the power supply and detecting the on / off of the main power supply (13) to inform the main control circuit (11) of the state of the main power supply (13). 14) is also provided. Further, a first power supply path for constantly supplying power to the memory (10) from the main power supply (13), and a third on / off switch from the backup power supply (BAT) when the main power supply (13) is off. A second power supply path for boosting power by the DC-DC converter (15) to supply power to the memory (10) via the switch (SW3) and turning on / off of the third switch (SW3). A second switch (SW) installed between the voltage detection circuit (12) for controlling and the main power supply (13) and the main control circuit (11) for turning on / off the power supply of the device.
2) and power is directly supplied from the main power supply (13) to control the on / off of the second switch (SW2) according to an input signal from the outside, and the main power supply (13) is turned on. It is also characterized in that the main control circuit (11) is provided with a power supply control circuit (14) for detecting the ON / OFF state and notifying the main power supply (13) of the state.

[0005]

In the present invention, by utilizing the energy-saving mode configuration, the power is supplied from the main power source to the memory when the main power source is turned on, thereby reducing the power consumption of the secondary battery. Further, when the main power supply is turned off, it is selected whether or not the backup is performed to extend the life of the secondary battery, and the voltage of the backup circuit is monitored to detect whether or not the memory is backed up. Further, by using a DC-DC converter for the backup power supply circuit, the discharge voltage of the secondary battery is lowered to reduce the cost, and the voltage of the secondary battery is detected to determine whether the backup is turned on or off. Extend the life of the secondary battery. As a result, when the main power is turned on, the memory is backed up without being supplied with power from the battery, so the number of charge / discharge cycles is reduced, and as a result, the life of the battery is extended. In addition, the main control circuit selects whether to perform backup when the main power is off,
Since it is possible to recognize whether or not the memory backup has been performed when the main control circuit is on, the backup level can be selected depending on whether important data exists in the memory or not, and as a result, the battery level The life can be extended. Furthermore, since the DC-DC converter is used to boost the voltage, a battery with a low rated voltage can be used and the charging circuit can be simplified, so that the cost can be reduced. Further, since the battery voltage is monitored and backup is stopped, deterioration of the battery life due to over-discharge does not occur.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a memory backup circuit showing a first embodiment of the present invention. 1 is different from the conventional memory backup circuit shown in FIG. 4 in that a switch SW2 is newly installed between the main power supply 13 and the main control circuit 11. That is, in the conventional backup circuit, the main power is turned on /
While the power supply of the device is turned on / off by turning it off, in the present embodiment, the main power supply is always kept on and the power supply of the device is turned on / off by turning on / off the switch SW2. Do off. When the switch SW2 is off, no current flows in the main control circuit 11, so the memory 10 does not operate, and only a charging current flows for memory backup to the secondary battery BAT. Therefore, the current consumption is very small, and since the memory 10 is inactive, the secondary battery BAT is not discharged. Only when the main power supply 13 is turned off due to a power failure, that is, when the switch SW2 is on and the main power supply 13 is turned off due to a power failure or the like, a discharge current is supplied from the secondary battery BAT to the memory 10 to perform backup. .

FIG. 2 is a block diagram of a memory backup circuit showing a second embodiment of the present invention. In FIG. 2, an automatic power supply start-up circuit (power supply control circuit) 14 for the energy saving mode of the facsimile apparatus is further incorporated.
The power supply control circuit 14 activates the main control circuit 11 by detecting a ringing signal or the like. During normal operation, the switch SW2 is activated by a signal from the power supply control circuit 14.
Is turned on, power is supplied to the main control circuit 11, and the apparatus operates. The switch SW1 is also turned on by the signal from the main control circuit 11, and the charging current flows in the secondary battery BAT. On the other hand, in the standby mode, when the energy saving mode is designated and important information is not input to the memory, the switch S is activated by the signal from the main control circuit 11.
W1 is turned off, and the switch SW2 is turned off by a signal from the power supply control circuit 14. At this time, since the main power supply 13 is on, the secondary battery BAT is not discharged, but a current flows through the path of the main power supply 13 → diode D1 → memory 10, so the memory 10 is backed up. The voltage monitoring circuit of the backup circuit in the main control circuit also detects the presence of the battery. In this state, when the ringing signal and other signals are input, the power supply control circuit 14 turns on the switch SW2. Main control circuit 11
Recognizes that the contents of the memory 10 are backed up by the information of the voltage monitoring circuit of the built-in backup circuit.

In FIG. 2, the main power source 1 is caused by a power failure or the like.
3 is turned off and then turned on again, the power supply control circuit 1
Reference numeral 4 turns on the switch SW2 and also notifies the memory control circuit 11 that the switch SW2 is turned on by turning on the main power. The main control circuit 11 thereby recognizes that the contents of the memory 10 have not been backed up. Next, in the standby mode, when the energy saving mode is designated and important information is input to the memory 10, the switch SW1 is turned on by the signal from the main control circuit 11 and the signal from the voltage detection circuit 12. The switch SW2 is turned off by a signal from the power supply control circuit 14. While the main power supply 13 is on, the secondary battery BAT is not discharged and the memory 10 is backed up. In this state, when the ringing signal and other signals are input, the same operation as described above is performed, that is, the power supply control circuit 14 turns on the switch SW2 and the switch SW2 is turned on to the main control circuit 11. Notice. As a result, the main control circuit 11 causes the memory 10
Recognize that the contents of are backed up. On the other hand, when the main power supply 13 is turned off due to a power failure or the like, the switch SW
Since 1 is on, the memory 10 is backed up by being supplied with power from the secondary battery BAT. Secondary battery BAT
Is discharged to a voltage below a certain voltage, the switch SW1 is turned off by the voltage detection circuit 12, and the backup is stopped. When the main power supply 13 is turned on, the voltage detection circuit 12
Since the output of is read by the main control circuit 11, the main control circuit 11 recognizes whether or not the contents of the memory 10 are backed up.

FIG. 3 is a block diagram of a memory backup circuit showing a third embodiment of the present invention. Circuit of FIG. 3 and FIG.
2 is different from that of FIG. 2 in that the switch SW1 in FIG. 2 is removed, a switch SW3 is provided between the main power supply 13 and the memory 10 instead, and that a switch SW3 is provided between the main power supply 13 and the memory 10. The DC-DC converter 15 is newly connected, and the switch SW2
The point is that the path is connected from the front part of to the memory 10 via the diode D2. The switch S
The control inputs of W3 are the output from the voltage detection circuit 12 and the output from the main control circuit 11. That is, in the embodiment of FIG. 2, the backup path by the main power supply 13 and the backup path by the secondary battery BAT are the same path, but in this embodiment, they are separate paths. Further, the switch SW3 is installed in the discharge path of the secondary battery BAT. As described above, in the third embodiment, the DC-DC converter 15 is used for the backup circuit, and the low voltage battery can be used. That is, a DC / DC converter 15 boosts the voltage to 5V using a battery having a charging / discharging voltage of 3V. Further, for this reason, the overdischarge is prevented by directly monitoring the voltage of the secondary battery BAT.
The operation of this circuit is almost the same as in the case of FIG. During normal operation, power is supplied from the diode D2 in order to reduce the output current of the DC-DC converter 15. That is, the switch SW turns on / off the device power
2 is turned on / off, and when the device power is off, the contents of the memory 10 are backed up from the main power supply 13 via the diode D2. Main power supply 13 due to power failure
Is off, the discharge current of the secondary battery BAT is turned on, and the DC-DC converter 15 is turned on via the switch SW3.
The voltage boosted by is supplied to the memory 10.

[0010]

As described above, according to the present invention,
Since the memory is backed up without supplying power from the battery when the main power is turned on, the number of charge / discharge cycles is reduced, and as a result, the life of the battery is extended. In addition, the main control circuit can select whether or not to perform backup when the main power is off, and can recognize whether or not memory backup has been performed, so the backup level can be selected depending on the presence or absence of important data. As a result, the life of the battery can be extended. Furthermore, since the voltage is boosted by the DC-DC converter, a battery with a low rated voltage can be used, and the charging circuit can be simplified, so that the cost can be reduced. Further, since the battery voltage is monitored and the backup is stopped, deterioration of the battery life due to over-discharge does not occur.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a memory backup circuit showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a memory backup circuit showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a memory backup circuit showing a third embodiment of the present invention.

FIG. 4 is a block diagram of a conventional memory backup circuit.

[Explanation of symbols]

10 ... Memory, 11 ... Main control circuit, 12 ... Voltage detection circuit, 13 ... Main power supply, 14 ... Power supply control circuit, 15 ...
DC-DC converter, SW1, 2, 3 ... Switch, D
1, D2 ... Diode, R1 ... Resistor, ZD ... Zener diode, BAT ... Secondary battery,

Claims (3)

(57) [Claims] 1. A memory backup circuit comprising a main power supply, a main control circuit and a memory receiving power from the main power supply, and a backup power supply for backing up the memory, wherein power is constantly supplied from the main power supply to the memory. In addition, when the main power supply is off, a power supply path for supplying power to the memory from the backup power supply and a power supply path for supplying power to the memory from the backup power supply of a rechargeable secondary battery are turned on. A first switch that turns on / off, a voltage detection circuit that detects an input voltage to the memory and controls on / off of the first switch, and is installed between the main power supply and the main control circuit. A memory backup circuit comprising a second switch for turning on / off the power supply of the device. 2. A memory backup circuit comprising a main power supply, a main control circuit and a memory receiving power from the main power supply, and a backup power supply for backing up the memory, wherein power is constantly supplied to the memory from the main power supply. In addition, when the main power supply is off, a power supply path for supplying power to the memory from the backup power supply and a power supply path for supplying power to the memory from the backup power supply of a rechargeable secondary battery are turned on. A first switch that turns on / off, a voltage detection circuit that detects an input voltage to the memory and controls on / off of the first switch, and is installed between the main power supply and the main control circuit. A second switch for turning on / off the power of the device, and power supplied directly from the main power source The main control circuit includes a power supply control circuit that controls ON / OFF of the second switch according to a power signal, and a power supply monitoring circuit that is supplied with power from the backup circuit and monitors the voltage of the backup circuit. A memory backup circuit characterized by the above. 3. A memory backup circuit comprising a main power supply, a main control circuit and a memory receiving power from the main power supply, and a backup power supply for backing up the memory, wherein the main power supply always supplies power to the memory. And a second power supply path for supplying power to the memory when the main power supply is off and the backup power supply is stepped up by a DC-DC converter via a third on / off switch.
Of the third ON / OFF by detecting the power supply path of the
A voltage detection circuit for controlling a full on / off switch, is installed between the main power supply and the main control circuit, a second switch for turning on / off the device, power is supplied directly from the main power And a power supply control circuit for controlling ON / OFF of the second switch according to an input signal from the outside, and a power supply monitoring circuit for supplying power from the backup circuit and monitoring the voltage of the backup circuit. A memory backup circuit provided in the main control circuit.