JPS5831213Y2 - memory backup circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit that uses a battery to retain memory in a memory section when the input voltage drops, and at this time stops supplying auxiliary power to circuits other than the memory.

A conventional memory backup circuit is shown in FIG.

In the figure, 7 is a power transformer, 8 is a rectifier circuit, 9 is a smoothing capacitor, and 1 is an output voltage V that is lower and stabilized than the input voltage Vi.

2 is a control unit, 3 is a memory,
6 is a battery.

In the case of a vending machine, the control unit 2 performs calculation control such as calculation of input amount, calculation of change, and determination of whether or not a sale is possible, and the memory 3 stores the calculation results by the control unit 2.

In the above circuit, when the power supply voltage drops due to a power outage or voltage fluctuation, the diode 10 becomes conductive and auxiliary power is supplied from the battery 6 to the memory 3 for backup.

However, in this circuit, auxiliary power is supplied to the control unit 2 and the stabilized power supply circuit 1 other than the memory 3, resulting in rapid battery consumption.

To improve this, it is possible to connect a diode 11 between the control unit 2 and the memory 3 as shown in FIG. 2, but the forward rising voltage Vf of the diode is 0.7 to 0.9
(2) Therefore, there is a problem in the interface between the memory 3 and other (2)/C circuits, which is particularly noticeable in C-MO3 ICs.

Furthermore, since the memory 3 is connected to the stabilized power supply circuit 1 through a diode, there is a drawback that the voltage of the memory 3 becomes extremely unstable.

FIG. 3 shows an embodiment of a memory backup circuit according to the present invention.

In the figure, 5 is an NPN transistor with a stabilized output voltage V at its collector.

is supplied and connects the emitter to the memory 3 and the diode 10.

4 is a Zener diode whose anode is connected to the base of the transistor 50 through a resistor 11, and the base of the octopus is connected to the resistor 12 connected to the collector.

The cathode of the Zener diode 40 is connected to the input side of the stabilized power supply circuit 10.

In the above configuration, under normal conditions, the input voltage V. is higher than the constant voltage of the Zener diode 4, and the transistor 5 is supplied with a base current and becomes conductive.

Therefore, the output voltage V is applied to the memory 3 through the transistor 5.

However, since the saturation voltage between the collector and emitter of the transistor 5 is 20 to 5 mV, no interface problem occurs.

When the input voltage vi falls, the Zener diode 4 is cut off, the transistor 5 becomes non-conductive, the diode 10 becomes conductive, and the memory 3 is supplied with auxiliary power from the battery 6.

If such a switching circuit is simply composed of transistors, when the input voltage drops, the difference between the base and collector of the transistor 50! ! The current from the battery 6 flows to the control unit 2 and the stabilized power supply circuit 1 which should be cut off by 7% of the current in the @ direction.

However, in the present invention, the above-mentioned situation is prevented by the Zener diode 4, and the leakage current of the Zener diode 4 at the time of cut-off is shunted by the resistor 12, so that the base voltage of the transistor 50 can be reliably lowered.

According to the present invention described in detail above, it is possible to back up only the memory without using a special interface and at any input voltage below the normal operating voltage.

Therefore, since battery consumption can be minimized, the lifespan of non-rechargeable primary batteries can be extended, which is particularly effective.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram using a conventional battery backup circuit, FIG. 2 shows an example using a diode, and FIG. 3 shows a battery backup circuit according to the present invention. DESCRIPTION OF SYMBOLS 1... Stabilized power supply circuit, 2... Control unit, 3... Memory, 4... Zener diode, 5... Transistor, 6...
Battery.

Claims (1)

[Scope of utility model registration request] In a circuit in which a control unit and a memory are connected to the output side of a stabilized power supply circuit that generates a low output voltage due to an input voltage, a Zener diode connected to the input terminal of the stabilized power supply circuit is connected to the Zener diode at the base. a transistor having a collector connected to the control section and the output side of the stabilized power supply circuit and an emitter connected to the memory; a resistor connected between the base and collector of the transistor; and a battery connected to the emitter of the transistor. A memory backup circuit consisting of.