JP3354413B2 - Electronic circuit backup voltage detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a backup voltage detecting device for an electronic circuit.

[0002]

2. Description of the Related Art In a conventional backup voltage detecting device for an electronic circuit shown in FIG.
Microcomputers (hereinafter referred to as microcomputers) having (random access memory) IC, IC3 are IC1, IC
V11 is a reset IC that outputs a reset signal of
C1 is a backup voltage for IC2, and C1 is a backup capacitor. The IC2 performs different processing for other circuit systems depending on the presence or absence of the backup data of the IC1 when there is data and when there is no data. If the voltage V11 of the backup capacitor C1 becomes lower than the reference voltage (backup guaranteed voltage) of the IC3 in the backup state with the backup voltage V11 of the backup capacitor C1 when the power supply V is turned off, a reset signal is output from the IC3, and the IC1 and IC2 are reset. Both are reset to prevent runaway of the IC (a state where the memory contents are not guaranteed).

[0003]

By the way, when IC1 and IC2 are reset by a reset signal from IC3, the backup data of IC1 is erased. The processing in the case where there is no is performed for another circuit system. At this time, IC
1. Power supply for IC2 and backup capacitor C1,
Reset IC IC3 has a common power supply, and IC1, I2
Since the reset signal of C2 is common, IC2 cannot directly recognize the presence or absence of the backup data of IC1, so that the process is selected depending on whether or not IC2 itself has been reset.

[0004] As another example, in FIG.
The power supply of C2 and the backup capacitor C1 are common, but the power supplies of IC1 and IC2 are 3V and 5V, for example.
If the power is supplied from different power lines like
There has been a problem that IC2 cannot determine at all whether there is backup data for IC1.

An object of the present invention is to solve the above-mentioned problem and to provide a backup voltage detecting device for an electronic circuit capable of detecting a backup state of the electronic circuit.

[0006]

Backup voltage detecting device for an electronic circuit according to the present invention According to an aspect of the first micro which the first backup voltage from the backup voltage source connected to the power supply of the first voltage value is supplied A computer IC and a second power supply different from the first power supply supplied with a voltage having a second voltage value different from the first voltage value;
In the electronic circuit and a second microcomputer IC that performs processing according to the presence or absence of a backup of the microcomputer IC, the first switch is inserted between the backup voltage source and the first power supply, said first 2 microcomputer IC is the first microcomputer
Detecting means for detecting a backup voltage of the computer IC via a second switch; comparing means for comparing the detected voltage value with a reference voltage value; and control means for controlling the first and second switches. It is a thing.

[0007]

[0008]

A first electric component (for example, a microcomputer IC) to which a backup voltage is supplied from a capacitor as a backup voltage source connected to a power supply, and a process for performing a process according to the presence or absence of backup of the first electric component. In an electronic circuit including two electric components (for example, a microcomputer IC), a first switch is inserted between a power supply and a backup capacitor, and the second electric component is
The backup voltage of the first electric component is detected via the second switch, and a process according to the backup state of the first electric component is performed.

[0009]

FIG. 1 is a circuit diagram showing an embodiment of a backup voltage detecting device for an electronic circuit according to the present invention. In FIG. 1, IC1 has a microcomputer IC having an internal RAM (random access memory) to be backed up, and IC2 has an internal RAM (random access memory), and controls on / off of switches S1 and S2, and control of IC1. This is a microcomputer IC that detects and determines a backup voltage and performs processing for other circuits based on the detection and determination. V1 is a power supply of the IC2, V2 is a power supply of the IC1 having a voltage different from the power supply V1, and C1 is a capacitor as a backup voltage source.

When the power supplies V1 and V2 are off, the switch S
1, S2 is off. When the power supply V1 and the power supply V2 are turned on, the IC2 rises and the switch S2
Turn on. At this time, the switch S1 is off. Backup capacitor C1 through switch S2
, Ie, the backup voltage Vd of IC1 is input to the detection input port of IC2. In IC2,
The voltage Vd input to the detection input port is compared with a predetermined reference voltage value Vr. This reference voltage value V
r is set to a voltage level at which IC1 can be backed up. As a result of the comparison, if the detected voltage Vd is smaller than the reference voltage value Vr, the IC2 determines that the IC1 is not backed up, and if the detected voltage Vd is larger than the reference voltage value Vr, it determines that the IC1 is backed up. Accordingly, the IC2 turns on the switch S1 in accordance with the former determination, applies the power supply V2 to the IC1 via the switch S1, supplies a reset signal to the IC1 when Vd <Vr, resets the IC1, and resets the IC1. In the case of Vr, a process corresponding to the presence or absence of backup of the IC is performed without outputting a reset signal.

As described above, even when the power supplies of IC1 and IC2 are different, the backup state of IC1 can be detected by IC2. Further, since the switch S1 is turned off immediately after the power supplies V1 and V2 are turned on and until the detection of the backup voltage ends, the power supply V2 supplies the backup capacitor C
The backup voltage can be accurately measured without 1 being charged. Further, since the switch S2 is off while the power supplies V1 and V2 are off, there is no decrease in the charge of the backup capacitor C1 flowing to the detection input port of the microcomputer. Also,
It is not necessary to use a backup reset IC (for example, IC3 in FIG. 2).

[0012]

EXAMPLES Although the microcomputer IC and I C1, IC 2 in the example of FIG. 1, but may be other electrical components having an equivalent function is not limited thereto.

[0013]

According to the electronic circuit backup voltage detecting device of the present invention, the backup voltage of the microcomputer IC can be detected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a backup voltage detecting device for an electronic circuit according to the present invention.

FIG. 2 is a circuit diagram showing an example of a conventional backup voltage detecting device for an electronic circuit.

[Explanation of symbols]

 IC1 microcomputer IC IC2 microcomputer IC V1 power supply V2 power supply C1 backup capacitor S1 switch S2 switch

Claims (1)

(57) [Claims] 1. A first microcomputer IC to which a backup voltage is supplied from a backup voltage source connected to a first power supply having a first voltage value, and a second power supply different from the first power supply. A voltage having a second voltage value different from the first voltage value is supplied, and the first microcomputer
An electronic circuit including a second microcomputer IC for performing processing according to the presence or absence of backup of the computer IC , wherein a first switch is inserted between the first power supply and the backup voltage source; Microco
The computer IC is the first microcomputer I
Detecting means for detecting the backup voltage of C via a second switch; comparing means for comparing the detected voltage value with a reference voltage value; and control means for controlling the first and second switches. A backup voltage detecting device for an electronic circuit, comprising: