JPH02309569A - Power source with battery backup - Google Patents

Abstract

PURPOSE:To prevent an error operation owing to a voltage drop of a battery and an overdischarge of the battery by providing a switching device operated by the control signal from an output watching device when a power source is backed up by the battery. CONSTITUTION:By turning on a switch 5, an AC input is fed to a DC power source 1, a transistor and a switching circuit 3 are turned on while a DC voltage is output to the load, and a battery 4 is charged. When the AC output is cut off, a DC voltage is fed to the load from the battery 4, but when it is continued for a long time, the output of the battery 4 is reduced. By selecting the values of resistances R1 to R3 adequately in such a case, the transistor and the circuit 3 are turned off and the output is cut off when the output is made less than a specific level. Consequently, an error operation of the load owing to the reduction of the battery voltage, and a deterioration of performance owing to an overdischarge of the battery can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply with battery backup that supplies power to electronic equipment that requires temporary power backup during a power outage.

[Prior Art] When a conventional power supply with battery backup uses an internal battery to back up an electronic device when the input voltage is cut off, current continues to flow from the battery to the electronic device regardless of the state of charge of the battery, thereby preventing battery overload. No consideration was given to discharge, output voltage drop, etc.

[Problems to be Solved by the Invention] However, the above-described power supply with backup has the following two problems.

(1) The battery will be over-discharged and its life will be shortened.

(2) The operation of the load electronic equipment becomes unstable due to a decrease in the battery output voltage.

The present invention aims to solve the above problems and prevent over-discharge of a battery and malfunction of electronic equipment as a load.

[Means for Solving the Problems] The present invention provides a power supply for supplying power to electronic equipment, which includes a DC power supply unit that converts an input voltage to a DC output voltage, and a DC power supply unit for backing up a load when the input voltage is cut off. a battery installed in parallel with the output of
It is characterized by comprising means for monitoring the output voltage of a power source, and switch means for preventing overdischarge of the battery, which is operated by a control signal from the output voltage monitoring means.

Embodiment FIG. 1 is a schematic diagram of a circuit showing an embodiment of the present invention. 1 is a DC power supply section that converts AC input voltage to DC output voltage. 2
is an output voltage monitoring circuit composed of resistors R1, R2, R3 and a transistor. 3 is a relay switch. 4
5 is the main switch for turning on and off the power supply with battery backup.

vout is the voltage between A and C, which is the output voltage for the load. VB is the voltage between I and I, which is the output voltage of the backup battery.

The operation of this circuit will be explained. When switch 5 is turned on, AC input voltage is supplied to the DC power supply section.

The DC power supply section outputs a DC voltage (Vout) to the load. Also, at this time, R1, R2 of the second output voltage monitoring circuit,
By appropriately determining the resistance of R3, the transistor is turned on, relay 3 is turned on, and battery 4 is charged.

If the AC input voltage is cut off due to a power outage etc. in this state,
This time, DC voltage (VB) is supplied from the battery 4 to the load.

When the cut-off time extends for a long time, the output voltage VB of the battery 4 decreases. By appropriately selecting the values of R1, R2, and R3, when this output voltage VB falls below a certain level, the transistor will turn off, relay 3 will break, and power will not be supplied from battery 4. It disappears.

When the cutoff of the AC input voltage is released, power is again supplied from the DC power supply section, so the output voltage VB rises, the transistor is turned on, the relay is closed, and the battery is charged.

[Effects of the Invention] This makes it possible to prevent load manufacturability due to a drop in battery voltage VB during power backup by battery 4. Furthermore, deterioration of the characteristics of the battery 4 due to over-discharge of the battery 4 can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment according to the invention. 1: DC power supply section 2: Output voltage monitoring circuit consisting of resistors R1, R2, R3 and transistors 3: Switch circuit 4 using a relay for backup Battery 5: Main switch of the power supply. that's all

Claims (1)

[Claims] A power supply that supplies power to electronic equipment includes a DC power supply unit that converts input voltage to a DC output voltage, a battery that is attached in parallel to the output of the DC power supply unit for the purpose of backing up the load when the input voltage is cut off, and a power supply unit. 1. A power supply with battery backup, comprising means for monitoring the output voltage of the battery, and switch means for preventing over-discharge of the battery operated by a control signal from the output voltage monitoring means.