JPS59144926A - Backup power supply circuit - Google Patents

Abstract

PURPOSE:To execute a backup operation so that load operation at the time of backup power supply can be guaranteed over a long period by always supplying so that the optimum power supply voltage originaly required by a load even at the power supply by a main power source or at the power supply by backup. CONSTITUTION:When a main current supply VCC is applied to a power supply terminal 1, the VCC is supplied to a load through a diode D1. Since the power is simultaneously supplied also to an analog switch element 4 through a line 41, the element 4 is turned to an operation enabled state. A high level signal is applied to a control terminal C2 through a resistor R1 under said state, so that an analog switch circuit SW2 is closed and a low level signal is applied to a control terminal C1. Consequently, the analog switch circuit SW1 is opened again and a battery 2 is disconnected from a power supply line.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a battery silent lζ bank amplifier power supply circuit.

Conventional technology Even if the main power supply that supplies gravity to the load suddenly becomes unable to supply power due to a power outage or failure, the main power supply can be restored from a separately installed battery, etc.
There is a so-called backup power supply circuit that supplies power on behalf of the load and can operate continuously by smoothly replacing the power supply from the load side.

There are a variety of such bank-up power supply circuits, from those used in CVCF power supplies for large computer uninterruptible systems to those built into small electronic devices. This is to ensure continued stable operation under load. The present invention relates to a backup power supply circuit built into the latter electronic equipment.

FIG. 1 shows a back amplifier power supply circuit according to the prior art.

Main power supply V. 0 is supplied to the power supply terminal and the diode "DI"
' is led to the load terminal 3 via '. For example, the load is C-
MO8RAM to 5y, is often used for the purpose of preserving υ memory. Main power supply V. If 0 is +5V, the forward voltage drop of the diode (hereinafter referred to as vF) is 0.4V to 0.
Since the voltage is 6V, approximately 4.4V is supplied to the terminal 3. 2 is a lithium battery, for example, for powering the back amplifier, and its output voltage is normally 3.0V to 3.5V. Therefore, the diode "D2" in the backup power supply path is biased in the reverse direction and is in the OFF state. In this state, a small amount of reverse current flows through the diode "D2, but this amount i
-i Increases rapidly as temperature rises. Especially C-MOS
In the case of a main power supply Vcc that does not operate a small current load such as an element, the power supply capacity is small and the increase in reverse current cannot be ignored in some cases.

Next, when the main power supply VCC is disconnected for some reason, the voltage at the load terminal 3 that has lost its power supply path also gradually decreases. Although this speed depends on the capacitor included in the load circuit and the load current, when the heavy pressure eventually decreases until the diode D2 is biased in the forward direction, a power supply path from the lithium battery 2 is formed at the load terminal 3.

Looking at this over time, we can see that the heavy pressure on the load terminal 3 gradually decreases from power supply from the power source 1 Vco to power supply from the lithium battery 2, and the load circuit operates normally at these direct voltages of 4.4V to 2.9V. It is possible. That is.

This purpose can be achieved by simply constructing such a bank-up power supply circuit, but as mentioned above, the main power supply voltage V. The temperature dependence of the reverse current leaking through the terminal 'D2' when power is supplied by the bank amplifier and the relatively large VF (0.4 V to 0
．． 6 V) may not be negligible in order to maintain stable operation of the load circuit. This is also due to the essential drawback of the prior art using the diode "D2" that a bank amplifier feed line with a voltage lower than the main power supply line must always be provided.

Purpose The present invention has been made in view of the above-mentioned drawbacks of the prior art.The purpose of the present invention is to eliminate the above-mentioned drawbacks and to solve the problems originally required by the load even when the main power supply is being supplied or when the back amplifier is being supplied. By making it possible to always supply power at the optimum power supply voltage.

The object of the present invention is to propose a backup power supply circuit that can guarantee load operation during back bladder supply for a long period of time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the figures.

FIG. 2 is a buffer rough paper feeding circuit diagram of an embodiment according to the present invention. In the figure, the power supply path of the main power supply Vcc extends from the power supply terminal Che to the load terminal 3 via the diode Dht. Main power ■. . If is negative, of course the direction of the diode DI is reversed.On the other hand, the backup supply path is constituted by an analog switch element 4.For example, Motorola's C-
This is a MOS analogue integer element MC14066B.

To give an overview of the analog switch element 4, FIG. 3 shows its logic circuit diagram, and FIG. 4 shows a logical value table for the operation of the circuit shown in FIG. 3. The basic configuration of the analog switch element 4 is a three-terminal circuit shown in FIG.
Input terminal I, output terminal O, and input terminal 1. It consists of an analog switch circuit SW interposed between the two terminals. The analog switch circuit sw is kept open or closed by a signal from the control terminal C. FIG. 4 shows this relationship; when the LO level is applied to the control terminal C, the analog switch circuit SW is opened 0FFL, and when the HI level is applied 711, the analog switch circuit SW is turned ON. The analog switch circuit SW has its open B4V connected to the Wtν line (1, resistive to 1
000MΩ or more, and the line resistance when closed is 300MΩ.
It is necessary to realize the above-mentioned operation by setting the value to be less than or equal to Q. This ability to pass analog signals with low loss when open is comparable to the contact characteristics of relays, etc., and does not require mechanical structure or operation.
Since there is no deterioration in electrical characteristics, there is an effect that high-speed and stable switch operation can be obtained semi-permanently. 2 is a power supply for the bank amplifier power supply path. As long as each Yuzu cell can be used and a bright light can be obtained, Nuravanteri may be used, and its compaction is not subject to the limitations as in the above-mentioned prior art.

The operation and effect of the above configuration will be explained below.

Main power supply V to power supply terminal 1. When 0 is applied, this is the default.1) 'fi: Power is supplied to the load via. At the same time, Analogs Zutsute Shiko 4 also line 41 (
Since it is supplied with power in this manner, it is in an operational state. In this state, the H level is applied to the control terminal C2 via the resistor RL f, so the analog switch circuit SW2 is closed and the LO level is applied to the control terminal CI. Therefore, the analog switch circuit SW1 is opened and the battery 2 is cut off from the bank amplifier power supply path. The line resistance at the time of interruption is 1001
Since the voltage is 000 or more, even if there is current leaking from the load terminal 3 toward the battery 2, the needle is extremely small.

In the C-MUS analog switch element 4, the bias current flowing to the control terminal CI is still extremely small (nA
-pA order). Furthermore, in this state, a current flows through the analog switch circuit SW2 via the resistor R2t-. This resistor R2 is O of the analog switch circuit SW2, which will be described later.
It is a pull-up resistor that is used to apply the I level to the control terminal CI during FF, but as mentioned above, the control terminal C1
Since the bias current flowing through is extremely small, it is possible to make this resistance value extremely large.

In any case, the resistance value of resistor R2, or the control terminal C
The temperature dependence of the current flowing through the diode "D2" described above is
2, the amount of current supplied from the load terminal 3 to the backup power supply path in FIG. 2 has extremely small and predictable temperature dependence.

Therefore, if the main power supply VCe takes into account this amount of current, even if the main power source VCe is the minimum one that saves power, the current that should normally be supplied to the load will be insufficient due to the rise in the operating ambient temperature. This has the advantage of preventing situations like this.

Next, when the supply of the main power supply VCC is cut off for some unknown reason, the potential of the load terminal 3 also gradually decreases. For example, C-MO8R
If the load is a low power consumption load such as an AM load, the potential at the load terminal 3 will gradually decrease. During this time, the potential of the power supply terminal 1 decreases rapidly and becomes the potential of the control terminal C2 at the 'kLO level via the resistor R1. Since the analog switch circuit SW2 is opened, f(
I level is applied. Therefore, analog switch circuit S
When Wl is closed, a bank-up power supply path is formed in which power is supplied from the battery 2 instead. The voltage of battery 2 is the main power supply V
It may be the same as the value of cc. Analog switch circuit SWl
Since the line resistance is less than 300Q, for example, even if a 1 mAk bank up supply is applied, the voltage drop at SWI is 0.3
VF of the third diode (0.4V~0.
6 V). Furthermore, if the power supply current is higher than this, a battery 2 with a higher voltage may be used. Therefore, the load circuit has the advantage that the optimum rated power supply load originally required by the load circuit can always be obtained both during main power supply and during backup power supply.

Effects As described above, according to the present invention, it is possible to always provide the optimum rated power supply load required by the load, whether when the main power supply is supplying power or when the bank amplifier is supplying power. This has the effect of guaranteeing normal operation of the load during backup power supply. For example, C-MO8R
If the minimum value of the power supply voltage that guarantees AM operation is 2■, then in the conventional technology, the battery pressure is 2V + Vp (0,
When the voltage reaches 4 to 0.6 V), the life of the battery is considered to have expired. However, according to the present invention, the upper limit value of the battery voltage is not limited by the main power supply grinding pressure value.

To put it simply, it is possible to easily provide a bank-up power supply circuit with a long power supply life, since it is possible to use a battery having almost the maximum value of the power supply voltage that guarantees the operation of the C-MO8RAM. Of course, even if the same battery as in the conventional technology is used, if the power supply current is small, the voltage drop caused by the analog switch circuit SWl is sufficiently small compared to the VF of the diode D2. The increase in tonnage pressure margin also has the effect of extending the life of the notch.

Still, according to the present invention, especially if a C-MOS analog switch element is used in the backup power supply path, the amount of current flowing into the bank amplifier power supply circuit in the power supply path by the main power supply VCC is also small. In addition, since the temperature dependence of the amount of current is extremely small, there is no fear that excess current will be drawn into the backup power supply path even if the operating ambient temperature of the backup power supply path rises. This is the main power supply V provided to run all low power consumption loads such as C-MO8RAM. If it is 0, it is possible to configure the power supply capacity to be saved to the minimum necessary in advance, so it is possible to improve the efficiency of the main power supply, which is particularly effective in small electronic devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a backup power supply circuit of the prior art. FIG. 2 shows a backup supply l of an embodiment of the present invention.
・Power supply terminal, 2 river battery, 3...load terminal, 4...
・Analog switch element, sw...analog switch circuit, Dl, D2...diode, R1, R2...
It is resistance. Fig. 1 Fig. 2 Fig. 4 Hand Itouri Neichi ■Yo Calligraphy (Hometsu 1 Discord June 2, 1958) Patent Application No. 18128-18128 2, Name of Invention Backup Power Supply Circuit 3. Relationship with the case of the person making the amendment Patent applicant Canon Co., Ltd. 3-30-2 Shimomaruko, Ota-ku, Tokyo Address: 1-11-10 Toramon, Minato-ku, Tokyo 105 Date of the 7th Order: 1 Right Brief description of drawings column/, contents of sleeve IJ- of subject specification dated May 31, 1958

Claims (1)

[Claims] (1) A main power supply line consisting of a diode and a back amplifier power supply line consisting of an analog switch means connected in series to a battery, the main power supply line and the backup power supply line being connected on the load side. When the sample is taken out, the analog switch means is opened. Further, the bank-up power supply circuit is characterized in that the analog switch means is closed when the detection means detects the absence of a main power source. 2. The bank amplifier power supply circuit according to claim 1, characterized in that the bank amplifier power supply circuit comprises an analog switch means or a C-MOS element.