JPH04199412A - Memory back-up device - Google Patents

Abstract

PURPOSE:To assure the back-up of a memory with high reliability despite a short daily using time of the memory by backing up the memory with use of a main power supply, a sub-power supply, and a battery. CONSTITUTION:A main power supply 25 is connected to a commercial power supply 21 via a series connection of a plug socket 22, a noise filter 23, and a power switch 24. Meanwhile a sub-power supply 26 having the capacity smaller than that of the supply 25 is connected to the supply 21 via the socket 22 and the filter 23. Then a volatile memory 28 is backed up by the supply 25 in an ON state of the switch 24 and then backed up the supply 26 in an OFF state of the switch 24 respectively. Then the memory 28 is backed up by a battery 31 when the supply 21 is stopped. As a result, the memory 28 can be backed up with high reliability despite a short daily using time of the memory 28. Furthermore the capacity of the battery 31 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a memory backup device for electronic devices such as electronic cash registers and PO5 (point-off sales) terminals that use relatively large-capacity volatile memories. .

[Prior Art] For example, large-capacity memories are used in electronic cash registers, POS terminals, etc. to register and process various product sales data, but such memories are volatile and require power backup. RAM which is memory
(random access memory) is used.

In this type of device, it is necessary to retain the data registered in the memory for many days, so a battery is installed to back up the memory even when the power is turned off at the end of the day's work. It has become.

As a memory backup device used in such electronic equipment, the one shown in FIG. 3 is conventionally known. This connects a power supply 5 to a commercial power supply 1 through an outlet plug 2, a nozzle filter 3, and a power switch 4 in series, and outputs a DC voltage VCC for operating each circuit from the output terminal of the power supply 5. It is outputting. A RAM 7, which is a volatile memory, is connected to the output terminal of the power source 5 via a diode 6. Further, a rechargeable battery 10 is connected to the output terminal of the power source 5 through a diode 8 and a charging current limiting resistor 9. Then, this battery 10 is connected to the RA through a diode 11.
Connected to M7 as a backup power source.

In this device, when the power switch 4 is turned on, the DC voltage VCC from the power source 5 is supplied to the RAM 7 via the diode 6, and also to the diode 8 and the resistor 9.
This battery 1 is supplied to the battery 10 via
0 is charged. Then, when the power switch 4 is turned off, the output of the DC voltage vcc from the power source 5 is stopped, so that the voltage of the battery 10 is supplied to the RAM 7 via the diode 11 and is backed up as a memory.

[Problems to be Solved by the Invention] Incidentally, the usage time of electronic cash registers, POS terminals, etc. may vary from day to day depending on the location and conditions of use. For this reason, in the conventional device, there was a risk that the battery 10 would be completely discharged in some cases, making it impossible to guarantee memory backup.

For example, a product designed to be used for 8 hours a day may
If the device is only used for about an hour, the battery will be completely discharged and memory backup cannot be guaranteed.

SUMMARY OF THE INVENTION Therefore, the present invention aims to provide a memory backup device that can reliably guarantee memory backup even if the usage time per day is short and that can reduce the capacity of the battery used.

Means for Solving Problem E] The present invention provides a main power source that is connected to a commercial power source via a power switch and outputs a DC voltage for operating each circuit section;
A sub power supply with a smaller capacity than the main power supply that is connected to the commercial power supply and outputs DC voltage, a battery, and a sub power supply that is backed up by the main power supply when the power switch is on, backed up by the sub power supply when the power switch is off, and that is connected to the commercial power supply. It consists of volatile memory that is backed up by a battery when the supply is interrupted.

[Function] In the present invention having such a configuration, when the power switch is on, DC voltage is supplied to the memory from the main power supply, and when the power switch is off, the memory is supplied with DC voltage from the sub power supply. is backed up. Furthermore, in the event of a power outage, the memory is backed up by a battery.

[Example code] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a main power source 25 is connected to a commercial power source 21 through an outlet plug 22, and further through a Nozzle filter 23 and a power switch 24 in series. This main power supply 25 outputs a DC voltage VCC for operating each circuit section from its output terminal.

In addition, the main power supply 2 is connected to the commercial power supply 21 through an outlet/plug 22 and further through a Nozzle filter 23.
A sub power supply 26 with a smaller capacity than 5 is connected. This sub power supply 26 outputs a DC voltage VCC2 necessary for memory backup from its output terminal.

A RAM 28, which is a volatile memory, is connected to the output terminal of the main power supply 25 via a diode 27.

In addition, a diode 29 is connected to the output terminal of this main power supply 25.
Further, a rechargeable battery 31 is connected via a charging current limiting resistor 30.

The RAM 28 is connected to the output terminal of the sub power supply 26 via a diode 32.

Further, the battery 31 is connected to the output terminal of the sub power source 26 via a diode 33 and a charging current limiting resistor 34.

The battery 10 is connected to the RA via a diode 35.
Connected to M28 as a backup power source in case of power outage.

The diode 3 is also connected to the output terminal of the sub power supply 26.
Further, a light emitting diode 38 is connected through a resistor 36 and the collector and emitter of a first transistor 37 of NPN type. The collector and emitter of a second NPN transistor 39 are connected between the base and emitter of the first transistor 37. Said first
The base of the transistor 37 is also connected to the cathode of the diode 32 via a resistor 40.

The base of the second transistor 39 is connected to the output terminal of the voltage VCCI of the main power supply 25 via a resistor 41.

In this embodiment with such a configuration, the power switch 2
4 is turned on, the main power supply 25 is connected to the commercial power supply 21, and the DC voltage VC is output from the output terminal of the main power supply 25.
CI is output and supplied to each circuit section and also to the RAM 28 via the diode 27.

Also, the battery 3 is connected via a diode 29 and a resistor 30.
1 is charged.

Further, since the sub power supply 26 is also connected to the commercial power supply 2, the DC voltage VCC2 is output.

By outputting the DC voltage V(,, the second transistor 39 is turned on and the first transistor 37 is turned off, so that the light emitting diode 38 is turned off.

When the power switch 24 is turned off in this state, the output of the DC voltage VCCI from the main power supply 25 is stopped. However, since the sub power supply 26 is connected to the commercial power supply 21, the output state of the DC voltage Vco2 from the sub power supply 26 continues.

Therefore, the DC voltage V CC2 from the sub power supply 26 is RA
Since it is supplied to M28, R is supplied even after the power switch 24 is turned off.
AM28 is reliably memory backed up. Furthermore, since the battery 31 is connected to the output terminal of the sub-power source 26 via the diode 33 and the resistor 34, charging continues.

Further, when the output of the DC voltage VCCI from the main power supply 25 is stopped, the first transistor 39 is turned off, so the second transistor 37 is turned on and the light emitting diode 38 is turned on. This informs the user that the sub power supply 26 is backing up the RAM 28.

Therefore, even if the power switch 24 is turned off for a long period of time, memory backup of the RAM 28 is reliably guaranteed.

Furthermore, when the commercial power supply 21 is out of power or the outlet plug 22 is disconnected, the DC voltage VC from the sub power supply 26 is
The output of C2 is also stopped. When such a situation occurs, the memory of the RAM 28 is backed up by the battery 31.

In this way, the memory of the RAM 28 will be reliably backed up no matter what happens.

Moreover, since the battery 31 only needs to perform memory backup control when a special situation occurs, such as when the commercial power supply 21 is out of power or when the outlet/plug 22 is disconnected, a small-capacity, inexpensive battery is sufficient.

In the above embodiment, the battery is charged by both the main power source and the sub power source, but the invention is not limited to this, and the battery may be charged by only the negative power source. A non-type primary battery may be used.

[Effects of the Invention] As detailed above, according to the present invention, memory backup can be reliably guaranteed even if the usage time is short in one day.
Moreover, it is possible to provide a memory backup device that can reduce the capacity of the battery used.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing one embodiment of the present invention, and FIG. 3 is a circuit diagram showing a conventional example. 21...Commercial power supply, 24...Power switch, 25...Main power supply, 26...Sub power supply, 28...RAM (volatile memory), 31...Battery. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A main power supply that is connected to a commercial power supply via a power switch and outputs DC voltage for operating each circuit, a sub power supply that is connected to the commercial power supply and outputs DC voltage and has a smaller capacity than the main power supply, and a battery. and a volatile memory backed up by the main power supply when the power switch is on, backed up by the sub power supply when the power switch is off, and backed up by the battery when the commercial power supply stops. memory backup device.