JPH0487533A - Memory backup battery system - Google Patents

Abstract

PURPOSE:To protect information stored in a RAM against long term power supply interruption, to reduce the size of the system through utilization of a small capacity primary battery, to reduce the frequency of replacement of the primary battery and the maintenance cost thereof, and to enhance the reliability of the system by connecting primary and secondary batteries in parallel with the circuit as a backup power supply for a RAM. CONSTITUTION:A power supply 1 feeds power to a RAM 2 and also charges a secondary battery V2. Upon interruption of the power supply 1, either a secondary battery section 20 or a primary battery section 10 having higher battery voltage begins to feed current. Upon restart of the power supply 1, a secondary battery voltage drop detecting/indicating section 21 detects voltage of the secondary battery V2 which is then compared with the reference voltage of a comparator Z2 and if it is lower than the reference voltage, voltage drop of the secondary battery V2 is indicated. A primary battery voltage drop detecting/indicating section 11 detects voltage of the primary battery V1 which is then compared with the reference voltage of a comparator Z1 and if it is lower than the reference level, voltage drop of the primary battery V1 and request for battery change are indicated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a memory backup battery system.

[Conventional technology]

As shown in Fig. 2, in the conventional memory backup battery system, when the backup battery is a primary lithium battery (hereinafter referred to as a negative battery) Vl, the CMOS SRAM is connected via a rectifier diode D2 for preventing current backflow. ,
When the +5V DC stabilized power supply (hereinafter referred to as the power supply) 1 that supplies current to the RAM) 2 is disconnected, the RAM
2, a rectifier diode 6 is used to prevent current backflow to the primary battery V1, and a resistor R is used to limit the current to the primary battery Vl when the rectifier diode 6 is short-circuited.
Current was supplied from the primary battery v1 to the RAM2 via the primary battery v1 and the RAM2.

Further, as shown in FIG. 3, when the backup battery is a secondary lithium battery (hereinafter referred to as secondary battery) V2, when the power supply 1 is in operation, the power supply 1 is connected to the RA via the rectifier diode D2.
In addition to supplying current to M2, a current limiting resistor R1
The secondary battery V2 is charged via the rectifier diode D3 for preventing backflow to the secondary battery V2, with the upper limit of the charging voltage determined by the constant voltage diode D1.

When the power supply 1 is cut off, the second revision pond V2 supplies current to the RAM 2 through the rectifier diode D4 for preventing backflow to the second revision pond V2, thereby protecting the stored information.

[Problem to be solved by the invention]

In the conventional memory backup battery system described above, when the battery is Ichikakenike V1, when the power supply 1 is expected to be disconnected for a long time and the load current of RAM 2 is relatively large, a battery with a large capacity is used. Must. However, since a primary battery with a large battery capacity also has a large external size, if there is a restriction on the external size due to device mounting, a battery with an external size within the restricted range will have a small capacity. As a result, the battery life expires within a short period of time after the product is shipped, reducing the reliability of the device and requiring battery replacement each time, which is a problem in that it is time consuming and costly.

In addition, if the battery is 2 Kaiken Ike V2, it can be used repeatedly by charging, but if the power is disconnected for a long time, the current capacity is small and it will be discharged in a short time, so it is not sufficient to protect the information in RAM2. There is also the problem that once over-discharge occurs, the service life rapidly decreases.

The purpose of the present invention is to protect information stored in RAM in response to long-term power outages, prevent deterioration of the life of the secondary battery, notify when to replace the primary battery, and use a small primary battery with a small capacity. To provide a memory backup battery system capable of reducing the size of the device, reducing the number of times of primary battery replacement, reducing maintenance costs, and improving the reliability of the device.

[Means to solve the problem]

The memory backup battery system of the present invention is connected in parallel with a power supply that supplies current to protect information stored in the RAM, and the type/source that is charged by the power supply and supplies current to the RAM when the power supply is cut off. a secondary battery voltage drop detection display unit that detects and displays a voltage drop in the secondary battery unit; and a secondary battery voltage drop detection display unit that detects and displays a voltage drop in the secondary battery unit;
It has a primary battery section connected in parallel to the power source that supplies current to the AM, and a primary battery voltage drop detection section that detects and displays a voltage drop in the primary battery section.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

This embodiment includes a power supply 1 that supplies current to protect information stored in the RAM 2, a secondary battery section 20 that is charged by the power supply 1 and supplies current to the RAM 2 when the power supply 1 is cut off, and a secondary battery section 20 A secondary battery voltage drop detection display unit 21 detects and displays a voltage drop in the primary battery unit 10, a primary battery unit lO supplies current to the RAM 2 when the power supply 1 is cut off, and a primary battery unit 10 detects and displays a voltage drop in the primary battery unit 10. It is composed of a next battery voltage drop detection section 11.

The secondary battery unit 20 includes two rechargeable batteries 2 and a power source 1.
rectifier diode for preventing current backflow to D2. D3 and 2
It is composed of a rectifier diode D4 for preventing current backflow to the reformed pond V2, a resistor R1 to limit the current from the power source 1, and a constant voltage diode D1 that sets the upper limit of the charging voltage of the reformed pond V2. .

The secondary battery voltage drop detection unit 21 includes a resistor R2 that limits the current from the 2nd amendment pond v2, resistors R3 and R4 that divides the current from the power source 1, and 2nd amendment 8 via the resistor R2. ! A comparator z2 that inputs the current of V2 and the current from current 1 via resistors R, 3, and R4, a resistor R5 that limits the current output from comparator z2, and a comparator Z2 via resistor R5. Light emitting diode D5 that lights up with a small current to display voltage drop indication ALM2
It is composed of.

Comparator Z2 is connected to V2 via resistor R2.
A voltage detection bin P2 inputs the current from the power source 1 and detects the voltage, a reference voltage bin N2 inputs the voltage of the current from the power supply 1 via resistors R3 and R4, and a voltage detection bin P2 and a reference voltage bin N2. It has an output bin T2 that outputs the comparison result of the voltage input from the input voltage.

The primary battery section 10 includes a replaceable 1st correction pond V1, a rectifier diode D6 for preventing current backflow to the 1st correction pond V1, and a resistor for limiting the current to the 1st correction pond V1 when the rectifier diode D6 is short-circuited. It consists of a certain resistor R6.

The primary battery voltage drop detection unit 11 includes a resistor R7 that limits the current from the first modified voltage source V1, resistors R8 and R9 that divides the current from the power source 1, and a first modified secondary voltage source via the resistor R7. Comparator z1 inputs the current of V1 and the current from power supply 1 via resistors R8 and R9, and comparator Z
a resistor R10 that limits the current output from the resistor R10, and a light emitting diode D7 that lights up with the current from the comparator z1 via the resistor R10 to display the voltage drop indication ALMI.
It is composed of.

Comparator Z1 is connected to V1 via resistor R7.
A voltage detection bin P1 inputs the current from the power source 1 and detects the voltage, a reference voltage bin N1 inputs the voltage of the current from the power source 1 via resistors R8 and R9, and a voltage detection bin P1 and a reference voltage bin N1. It has an output pin T1 that outputs a comparison result of voltages input from the input terminal.

Next, the operation of this embodiment will be explained. When power supply 1 is operating, it supplies power to RAM2 and at the same time
The secondary battery 2 is charged via the resistor R1 and the rectifier diode D3 of the battery section 20.

When the power supply 1 stops, the secondary battery section 20 and the primary battery section 10
Start supplying current at the same time or from whichever battery voltage is higher. If the power supply 1 is disconnected for a long period of time, the 2nd reform pond v2 has a smaller capacity than the 1st reform pond V1, so it is discharged relatively quickly. In that case, only one revision pond v1 supplies current to the RAM2.

When the power supply 1 operates again, the secondary battery voltage drop detection display section 21 detects the voltage of the second reformed pond V2 through the resistor R2.
It is detected by the voltage detection bin P2 of the comparator Z2 and compared with the voltage of the reference voltage bin N2 of the comparator Z2. When the voltage of the voltage detection bin P2 is below the voltage of the reference voltage bin N2, the output of the output pin T2 becomes rl-, level,
The light emitting diode D5 is turned on via the resistor R5, and a voltage drop display ALM2 indicating the voltage drop of the second modified pond V2 is displayed. In this case, the voltage of the reference voltage bin N2 is
If the depth of discharge is deep, the charging/discharging cycle of the battery will be shortened, so the secondary battery voltage drop detection display unit 21 is set to display the voltage drop display ALM2 at an early stage.

The primary battery voltage drop detection display section 11 detects the voltage of the first revision pond 1 via the resistor R7 at the voltage detection bin P1 of the comparator Z1, and detects the voltage at the reference voltage bin N of the comparator Z1.
Compare with the voltage of 1. When the voltage of the voltage detection bin P1 is lower than the voltage of the reference voltage bin N1, the output of the output pin T1 becomes "L" level, lights up the light emitting diode D7 via the resistor RIO, and the voltage of the voltage detection bin V1 decreases. and a voltage drop indication ALMI indicating a battery replacement request is displayed.

1 Replace the revision pond Vl with a new battery and turn on the power supply, the voltage drop display ALM1 of light emitting diode D7 will go out, and 2
The voltage of the voltage detection bin P2 of the comparator Z2 connected to the revision pond ■2 via the resistor R2 is the reference voltage bin N.
When the voltage exceeds 2, the voltage drop display ALM2 of the light emitting diode D5 is turned off.

Note that the first revision pond V1 is replaced when the secondary battery is charged or when the power supply 1 is in operation to protect information in the memory.

〔Effect of the invention〕

As explained above, the present invention provides a primary battery and a secondary battery with R
By connecting it in parallel to the circuit for power backup of AM, it is possible to protect the stored information in RAM in case of long-term power cut-off, and it is possible to use a small primary battery with a small capacity, which reduces the size of the device. This has the effect of reducing the number of primary battery replacements, lowering maintenance costs, and improving the reliability of the device.

In addition, by having a battery voltage drop detection display circuit,
This has the effect of preventing deterioration of the life of the secondary battery and notifying the replacement of the primary battery.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 and FIG.
The figure is a circuit diagram of a conventional example. 1...-Power supply, 2...RAM, Vl...
...-Primary battery, 10...Primary battery section, 11
-...Primary battery voltage drop detection section, V2...
・Secondary battery, 20... Secondary battery part, 21...
・-・Secondary battery voltage drop detection display section, Dl...
Constant voltage diode, D2. D3. D4゜D6...
- Rectifier diode, D5. D7------Light emitting diode, ALMI, ALM2---Voltage drop display,
R1, R2, R3, R4, R5, R6゜R7, R8, R
9, RIO---Resistor, Zl. Z2...Comparator, Nl, N2...
-Reference voltage bin, PL, R2...Voltage detection bin, T1. T2...- Output bin. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] a power source that supplies current to protect the information stored in the RAM; and a power source that is charged by the power source and that is activated when the power source is turned off.
2 connected in parallel with said power supply supplying current to M.
a secondary battery unit, a secondary battery voltage drop detection display unit that detects and displays a voltage drop in the secondary battery unit, and a unit connected in parallel to the power source that supplies current to the RAM when the power source is turned off. A memory backup battery system comprising: a secondary battery section; and a primary battery voltage drop detection section that detects and displays a voltage drop in the primary battery section.