JPH01311836A - Backup power circuit - Google Patents

Abstract

PURPOSE:To obtain a backup power circuit, the backup guarantee time of which at the time of service interruption is lengthened and which fills the role even in service interruption immediately after the start of the operation of an equipment by constituting a capacitor for the backup of a micor-computer so that the capacitor can be charged even from the power supply of the equipment. CONSTITUTION:Since the capacity of a capacitor 3 for backup is increased in order to lengthen the backup guarantee time at the time of service interruption, a resistor 4 for charge and discharge is scaled up, and the charging time is lengthened. Consequently, the capacitor 3 for backup is charged slowly from a power input 1 immediately after a power supply is turned ON, but the power input terminal 2 of a micro-computer can be supplied with sufficient currents, thus driving the micro-computer to start the operation of an equipment. Accordingly, currents flow through the base of a transistor 9 through a resistor 7 from a power supply 6 for the equipment, and the transistor 9 turns conductive and the capacitor 3 for backup is charged in a short time through a charging circuit composed of the resistor 7, a constant voltage diode 8 and the transistor 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to microcomputers (hereinafter referred to as microcomputers) such as color televisions and video tape recorders.
This relates to a backup power supply circuit that backs up the power for microcontrollers and memory in the event of an instantaneous or short-term power outage in devices that use

[Conventional technology]

Some devices that use a microcomputer or memory are equipped with a backup power circuit to prevent the microcomputer or memory from being reset in the event of an instantaneous or short-term power outage.

Conventionally, such a backup power supply circuit has a configuration as shown in FIG. In FIG. 2, 1 is a power input, 2 is a power input terminal of a microcomputer, 3 is a backup capacitor, 4 is a charging/discharging resistor, and 5 is a diode.

Next, the operation will be explained. The current input from the power input 1 drives the microcomputer through the power input terminal 2 of the microcomputer, and at the same time charges the backup capacitor 3 through the charging/discharging resistor 4.

At this point, an instantaneous or short-term power outage occurs and the power input 1
When it runs out, the backup capacitor 3 is discharged through the charging/discharging resistor 4, and the power input terminal 2 of the microcomputer is passed through to back up the microcomputer. At this time, the diode 5 is provided to prevent discharge current from flowing to the power supply input 1 side.

In this backup power supply circuit, in order to extend the guaranteed backup time in the event of a power outage, the backup capacitor 3 may have a large capacity.

1. Since current is required to drive the microcontroller, make the charging/discharging resistor 4 thicker. I. Increase the time it takes to charge the backup capacitor 3 so that it does not interfere with the microcontroller's operation. There is a need to.

[Problem to be solved by the invention]

Since the conventional backup power supply circuit is configured as described above, if the capacity of the backup capacitor 3 is made large in order to extend the guaranteed backup time in the event of a power outage, the time it takes for the backup capacitor 3 to be charged will be reduced. It needs to be longer.

However, there is a problem that if a power outage occurs immediately after the equipment starts operating, the backup capacitor 3 will not be sufficiently charged and will not function as a backup.

This invention was made to solve the problems mentioned in -J2, and provides a backup power supply circuit that extends the guaranteed backup time in the event of a power outage and functions even during a power outage immediately after the equipment starts operating. The purpose is to

[3I! Means for Solving the Problem] The backup power supply circuit according to the present invention includes a charging circuit for charging a backup capacitor also from the power supply of the device.

[For production]

The charging circuit in this invention, when the device starts operating,
Charge the backup capacitor from the device's power supply.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a power input, 2 is a power input terminal of a microcomputer, 3 is a backup capacitor, 4 is a charging/discharging resistor, and 5 is a diode. The charging cycle @10 described below is newly added to the configuration shown in FIG. 2.

That is, 6 is a power source for the device, 7 is a resistor, 8 is a constant voltage diode, and 9 is an L transistor, and the charging circuit 10 is constituted by these.

A resistor 7 and a constant voltage diode 8 are connected in series between the power supply 6 and ground of the 8i device, and a transistor 9 is connected at the connection point.
The emitter is connected to the connection point between the charging/discharging resistor 4 and the backup capacitor 3.

Further, the collector of the transistor 9 is connected to the power supply 6 of the device.

Next, the operation will be explained. Now, in order to prolong the guaranteed backup time in the event of a power outage, the backup capacitor 3 has a large capacity.Secondly, as already explained, the charging/discharging resistor 4 is made large to lengthen the charging time.

Therefore, immediately after the power is turned on, charging of the backup capacitor 3 from the power source 1 is slow, but sufficient current can be supplied to the power input terminal 2 of the microcomputer, so the microcomputer is driven and the equipment operates. start. Along with this, transistor 9 is passed from f4R6 of the device to resistor 7.
Current flows through the base of t, transistor 9 becomes conductive, and t
- Charge the backup capacitor 3 in a short time through the charging circuit.

In the above embodiment, as an example of the charging circuit 10 that charges the backup capacitor 3 from the power source 6 of the device, the charging circuit 10 is configured by the resistor 7, the constant voltage diode 8, and the transistor 9. Needless to say, there are many other circuits that can be used to achieve this.

[Effects of the Invention] As described above, according to the present invention, the backup capacitor of the microcomputer can be reduced to 8! Since the device is configured so that it can be charged from the power source of the device, the guaranteed backup time in the event of a power outage is extended, and the device can continue to function even in the event of a power outage immediately after the device starts operating.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a backup power supply circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional backup power supply circuit. 1...Power input, 2...Microcontroller power input terminal, 3
. . . Backup capacitor, 4. Resistor for charging and discharging, 6. Power supply for equipment, 7. Resistor, 8. Constant voltage diode, 9. Transistor, 10. Charging circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A backup capacitor that is charged from the power input through the charging/discharging resistor and, when the power input is removed, discharges to a predetermined device through the charging/discharging resistor and the power input terminal to back up this device; and a charging circuit that charges the backup capacitor from the power source of the device when charging the backup capacitor.