JPS649592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply failure detection circuit that detects an abnormality in the output voltage of a power supply.

FIG. 1 shows a generally known failure detection circuit for a conventional DC stabilized power supply.

In the figure, 1 and 2 are DC stabilized power supplies;
The negative side of 2 and the positive side of 2 are grounded. 3 is a relay, 4 is a contact of the relay, 5 is a resistor, and 6 is a switch.

Next, the operation will be explained. When the switch 6 is open, the coil of the relay 3 is not excited and the contact 4 is closed to the b side. When the switch 6 is closed, the coil of the relay 3 is energized, the contact 4 is closed to the a side, and the coil of the relay 3 is connected to the positive side of the stabilized power source via the resistor 5 and the switch 6.

When the voltage of the stabilized power supply drops, the coil of the relay 3 is demagnetized and the contact 4 is closed to the b side.

As described above, a failure of the stabilized power supply device can be detected based on the voltage drop.

Because the failure detection circuit of conventional regulated power supplies is configured as described above, it is not possible to detect low voltage regulated power supplies, and it is possible to detect when the voltage drops, but when the voltage increases In this case, there were various drawbacks such as inability to detect.

This invention was made with the aim of eliminating the above-mentioned drawbacks of the conventional technology, and by configuring a detection circuit using semiconductors, it is possible to detect failures in low-voltage stabilized power supplies and to detect failures in which the voltage increases. The present invention provides a power supply failure detection circuit that also enables detection.

An embodiment of the present invention will be described below with reference to the drawings. In Figure 2, 1 and 2 are DC stabilized power supply devices (hereinafter referred to as stabilized power supplies), and stabilized power supply 1
is on the positive side when viewed from the common potential, and the stabilized power supply 2 is on the negative side when viewed from the common potential. Reference numerals 7 and 8 denote resistors connected in series, and the potential at a connection point a between these resistors 7 and 8 during normal operation is set to be a negative potential. One end of the series connection circuit consisting of resistors 7 and 8 is connected to the positive side of the stabilized power source 1, and the other end is connected to the negative side of the stabilized power source 2. 9 is a resistor, 10 is a diode connected in series with the resistor 9, one end of the connection circuit consisting of the resistor 9 and the diode 10 is connected to the positive side of the stabilized power supply 1, and the other end is connected to the connection point a. There is. The resistors 7, 8, 9 and the diode 10 constitute a detection circuit. Reference numeral 11 denotes a transistor as a switch element, the base of which is connected to the connection point b between the resistor 9 and the diode 10. 12
is a diode, and the cathode of this diode 12 is connected to the connection point b, and the anode is connected to the emitter of the transistor 11, respectively. A diode 13 has an anode connected to the emitter of the transistor 11 and a cathode connected to the collector of the transistor 11, respectively. Note that the emitter of the transistor 11 and the anode of the diode 13 are respectively grounded. 14 and 17 are resistors connected in series, and the potential of the connection point c between these resistors 14 and 17 during normal operation is set to be a positive potential. One end of the series connection circuit made up of the resistors 14 and 17 is connected to the positive side of the stabilized power source 1, and the other end is connected to the negative side of the stabilized power source 2. 15
is a resistor, and 18 is a diode connected in series with the resistor 15. One end of the series connection circuit consisting of the resistor 15 and the diode 18 is connected to the positive side of the stabilized power supply 1, and the other end is connected to the connection point c. It is connected.
These resistors 14, 15, 17 and diode 18 constitute a detection circuit. Reference numeral 21 denotes a transistor as a switch element, the base of which is connected to the connection point d between the resistor 15 and the diode 18, and the collector connected to the positive side of the stabilized power supply 1 via the resistor 16. 19 is a diode, and the cathode of this diode 19 is connected to the connection point d.
, the anode is connected to the emitter of the transistor 21,
each connected. 20 is transistor 2
The diode 20 has an anode connected to the emitter of the diode 20, and the cathode of the diode 20 is connected to the base of a transistor 22 as a switch element. . Further, the emitter of the transistor 22 is grounded, and the collector is connected to the output terminal 23.

Next, the operation of the device configured as described above will be explained.

The potential at connection point b is divided by resistors 7 and 8 so that it becomes a negative potential when stabilized power supplies 1 and 2 are normal. All current flowing through diode 1
0, flows to the negative side of the stabilized power supply 2 via the resistor 8. In this state, no current flows through the base of the transistor 11, and the transistor 11 is non-conductive. In addition, the potential at the connection point c is divided by resistors 14 and 17 so that it becomes a positive potential when the stabilized power supplies 1 and 2 are normal. Current flows into the base of the transistor 21 through the transistor 15, and the transistor 21 becomes conductive. Further, at this time, a current flows from the positive side of the stabilized power supply 1 through the resistor 16, from the collector to the emitter of the transistor 21, and flows into the base of the transistor 22 through the diode 20, making the transistor 22 conductive.

Next, when the voltage across the stabilized power supply 1 increases, the potential at the connection point a increases and becomes a positive potential. Then, the current flowing from the positive side of the stabilized power supply 1 to the resistor 8 via the resistor 9 and the diode 10 flows into the base of the transistor 11, making the transistor 11 conductive. When the transistor 11 becomes conductive, the voltage flows from the stabilized power supply 1 to the resistor 16, from the collector of the transistor 21 to the emitter, and from the diode 20.
The current flowing into the transistor 22 via the resistor 16, the collector to the emitter of the transistor 21, the diode 19, flows from the collector to the emitter of the transistor 11, and then flows into the base of the transistor 22. There is no current and transistor 22 becomes non-conducting.

On the other hand, when the voltage across the stabilized power supply 2 decreases, the potential at the connection point a increases and becomes a positive potential. Therefore, transistor 11, in which current flows into the base of transistor 11, becomes conductive, and transistor 2
The inflow voltage to the base of transistor 22 disappears and transistor 22 becomes non-conductive.

Next, when the voltage across the stabilized power supply 1 decreases, the potential at the connection point c decreases and becomes a negative potential. At this time, the current flowing into the transistor 21 via the resistor 15 flows to the negative side of the stabilized power supply 2 via the diode 18 and the resistor 17, and the current flows into the transistor 21 via the diode 18 and the resistor 17.
1 is non-conductive. In addition, from the positive side of the stabilized power supply 1, the resistor 16 is connected, the collector of the transistor 21 is connected to the emitter, and the diode 20 is connected to the transistor 2.
The current flowing into the base of transistor 2 disappears, and transistor 22 becomes non-conductive.

Further, when the voltage across the stabilized power supply 2 increases, the potential at the connection point c decreases and becomes a negative potential. At this time, the current flowing into the base of the transistor 21 disappears, and the transistor 21 becomes non-conductive, so the current flowing into the base of the transistor 22 also disappears, and the transistor 22 becomes non-conductive. In this way, when a failure occurs in the DC stabilized power supply and the voltage rises or falls, the transistor 22
becomes non-conductive, and a failure of the DC stabilized power supply can be detected.

In the above embodiment, a failure is output due to non-conduction of the transistor 22, but if the electromagnetic relay 24 is connected to the output terminal 23 and the DC stabilized power supply 25 is connected as shown in FIG. 3, the DC stabilized power supply device is activated. 1, 2, and 25 failures can be detected.

In addition, in the above embodiment, the power supply is composed of two DC stabilized power supply devices 1 and 2, and the intermediate point thereof is kept at ground potential. It may also consist of only the stabilized power supply device 2.

As described above, according to the present invention, there is a detection circuit that detects an abnormality in the power supply voltage, a first switch circuit that is in communication state under normal conditions, and a second switch circuit that is connected to the first output side. and a third switch circuit that forms a bypass to the second switch based on the output of the detection circuit, so that it is possible to detect a failure in the low voltage DC stabilizing power supply and to prevent the voltage from increasing. Failures can be detected easily and reliably.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional DC stabilized power supply failure detection circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 3 is a circuit showing an example of application of the circuit shown in Fig. 2. It is a diagram. In the figure, 1 and 2 are DC stabilized power supplies, 3 is an electromagnetic relay, 4 is a contact of relay 3, 5 is a resistor, 6 is a switch, 7, 8, and 9 are resistors, 10 is a diode, and 11 is a transistor. , 12 and 13 are diodes, 14 and 15 are resistors, 16 and 17 are resistors,
18, 19, and 20 are diodes, 21, 22 are transistors, and 23 is an output terminal. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A first switch circuit connected to a power supply, which is connected to the output side of the first switch circuit and conducts through the first switch circuit when the voltage of the power supply is normal. a detection circuit that detects an abnormality in the voltage of the power supply; a detection circuit that makes the second switch circuit non-conductive based on the output from the detection circuit; 1. A power failure detection circuit comprising a third switch circuit forming a power supply line. 2. Power supply failure detection according to claim 1, characterized in that the power supply consists of a first power supply and a second power supply connected in series with each other, and the connection point thereof is maintained at ground potential. circuit. 3. The power failure detection circuit according to claim 1 or 2, wherein the detection circuit detects rises and falls in the voltage of the power supply.