JPH0863404A - Backup power unit - Google Patents

Abstract

PURPOSE: To hold the memory contents of a microcomputer for a long time in case of power source abnormality by cutting off a switch means when a drop in the voltage of a power line is detected. CONSTITUTION: When the voltage Vb of a power source 1 drops below a specific voltage (when the power source 1 stops, as well), a divided voltage Vd drops below the output voltage Vr of a regulator 3 and the output of a comparator 4 falls to an L level. A relay switch 5 is therefore cut off. Once the relay switch 5 is cut off, capacitors 10 and 11 begin to be charged and a backup power source 6 supplies (bacaks up) electric power to a microcomputer 7. At this time, the relay switch 5 is disconnected and the power source 1 and a driving part 2 are disconnected, so the discharging path of the backup power source 6 includes only the microcomputer 7 to extend the backup time. Consequently, the storage contents of the microcomputer 7 can be held for a long time if the power source 1 becomes abnormal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to a backup power supply device suitable for holding the stored contents of a memory of a microcomputer having a memory function.

[0002]

2. Description of the Related Art In recent years, a microcomputer having a memory has been used in various electronic devices, but the power supply voltage to the microcomputer has fallen below an allowable value (including a power failure) or the power is cut off. May cause the memory contents to be lost. In general, such a phenomenon often occurs momentarily, for example, only for a few seconds, and a backup power supply is provided to prevent the loss of the stored contents of the memory in order to cope with such a short time power supply abnormality. ing.

However, a large-capacity capacitor or the like is required to provide the required power capacity as a backup power source, and the size becomes large by using large parts, and the price becomes large by using special parts. There is also a problem in terms of FIG. 2 is a block diagram of a conventional backup power supply, and exemplifies an electronic device for a vehicle.

Reference numeral 21 denotes a power source, which is composed of a battery. Reference numeral 25 denotes an on-vehicle electronic device, which includes a drive unit 24 including various circuits and actuators, and a microcomputer (microcomputer) 23 that controls the drive units 24. The drive unit 24 and the microcomputer 23 are connected to a power supply 21. ing. A backup power supply 22 is connected between the microcomputer 23 and the power supply 21 to prepare for power failure.

The backup power source 22 is composed of a large-capacity capacitor 26 and is normally charged.
When the power supply voltage drops (generated by starting the starter motor, etc.) or the power supply stops, the capacitor 26
The electric power is supplied to the microcomputer 23 by the discharge from the.

[0006]

However, when the power supply voltage drops or the power supply is stopped, power is supplied to the microcomputer 23 by the backup power supply 22, but the drive unit 24 is connected to drive the drive. There is also power consumption by the unit 24. Therefore, the backup (power supply) time for the microcomputer 23 is shortened, and in order to extend the backup time, it is necessary to increase the capacity of the capacitor 26 of the backup power supply 22, which causes problems such as an increase in shape and an increase in price. Become.

The present invention solves such a problem.
The purpose is to realize a backup power supply that has a long backup time, is compact, and can be manufactured at low cost.

[0008]

SUMMARY OF THE INVENTION The present invention achieves the above-mentioned object, and in a backup power supply device for electronic equipment having a microcomputer having a memory, a power supply for supplying power to each circuit of the electronic equipment. In the line, switch means having one end connected, charging / discharging means connected to the other end of the switch means and at the power input terminal of the microcomputer, and when a voltage drop in the power line is detected,
And a detection means for shutting off the switch means.

[0009]

According to the present invention by the above means, when the power source voltage of the power source is lowered or stopped, the detecting means detects the state, and the switch means causes the charging / discharging circuit to operate in the electronic circuit. Since the circuit is disconnected from other circuits, the discharge path of the charge / discharge circuit is only the microcomputer, and the backup time can be extended.

[0010]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing the configuration of the embodiment and shows an on-vehicle device. Reference numeral 1 denotes a power source, which is composed of a battery and supplies power to each component of the vehicle-mounted device 13.

Reference numeral 2 denotes a drive unit, which is composed of various circuits and actuators for operating the in-vehicle device 13. A regulator 3 generates a stable voltage from the voltage of the power supply 1 and outputs it. The output voltage of the regulator 3 is a voltage Vr lower than or equal to the power source voltage Vb, and if the power source voltage Vb is higher than or equal to the voltage Vr, the power source of the voltage Vr is stably output.

Fixed resistors 8 and 9 are grounded in series with the power source 1 and output a divided voltage Vd for detecting the fluctuation of the power source voltage from an intermediate point thereof, and the divided voltage Vd is used as the comparator 4.
It is input to the non-inverting input terminal of. Reference numeral 4 denotes a comparator, which is a resistor 8 connected to the control voltage of the regulator 3 and the power supply 1.
(R1) and the voltage Vd divided by the resistor 9 (R2) are compared, and when the divided voltage Vd is lower than the output voltage Vr of the regulator 3, a low potential output (L level) is output,
In the opposite case, a high potential output (H level) is output. If it is determined that the power supply 1 is abnormal when the power supply voltage Vb of the power supply 1 becomes half, the output voltages Vr of the resistors 8 and 9 and the regulator 3 may be selected to have the following relationship.

2Vr (R1 + R2) = VbR2 However, when 2Vr <Vb, it is desirable that R1 and R2 are large in terms of power consumption. Reference numeral 5 is an electromagnetic relay switch, which closes its contact when the output of the comparator 4 is at H level. 6 is a backup power supply, which is a switch 5 and a microcomputer 7
It is connected to the microcomputer 7 during normal operation and is charged by the supply voltage from the power supply 1. When the power supply voltage Vb drops or when the power supply 1 is shut off, discharge is started to supply the backup power to the microcomputer 7.

The backup power source 6 has a diode 12 connected in the forward direction from the relay switch 5 toward the microcomputer 7, and capacitors 10 and 11 are provided at both ends of the diode 12.
Is grounded. The diode 12 is a diode for preventing backflow. 7 is a microcomputer,
The drive unit 2 such as the actuator of the vehicle-mounted device is controlled.
In addition, it has a built-in memory function for holding data for that purpose.

Next, the operation will be described. When the power supply 1 is normal, the divided voltage Vd is higher than the output voltage Vr of the regulator 3. Therefore, the output of the comparator 4 is at the H level, the relay switch 5 is connected, and the microcomputer 7 is supplied with power from the power supply 1.
The backup power source 6 is charged. But power supply 1
When the voltage Vb of the voltage Vb becomes lower than a predetermined voltage (the same applies when the power supply is stopped), the divided voltage Vd becomes lower than the output voltage Vr of the regulator 3 and the output of the comparator 4 becomes L level. Therefore, the relay switch 5 is cut off.

When the relay switch 5 is cut off, the backup power supply 6 supplies (backs up) power to the microcomputer 7 when the capacitors 10 and 11 start discharging. At this time, since the relay switch 5 is in the disconnected state and the power supply 1 and the drive unit 2 are disconnected, the discharge path of the backup power supply 6 is only the microcomputer 7, and the backup time can be lengthened.

When the power supply voltage Vb returns to a predetermined voltage,
The output of the comparator 4 becomes H level again, and the relay switch 5 is brought into the connected state to return to the normal power supply state.

[0018]

As described above, according to the present invention, since the charging / discharging means effectively supplies the discharge current to the microcomputer, the microcomputer can be used in the event of a power failure etc. without using a large and expensive component such as a large capacity capacitor. It becomes possible to retain the stored contents of the memory for a long time.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a conventional backup power supply device.

[Explanation of symbols]

 1 ... Power supply 2 Drive unit 3 Regulator 4 Comparator 5 Switch 6・ ・ ・ Backup power supply 7 ・ ・ ・ Microcomputer

Claims (1)

[Claims] 1. In a backup power supply device for an electronic device having a microcomputer having a memory, a power supply line for supplying power to each circuit of the electronic device,
A switch means having one end connected thereto, a charge / discharge means connected to the other end of the switch means and connected to a power input terminal of the microcomputer, and the switch means when a voltage drop in the power supply line is detected. A backup power supply device, comprising: