JPH04364332A - Power supply circuit at power failure for distribution line voltage current detector - Google Patents

Abstract

PURPOSE:To provide a downsized power supply system suitable as a long term backup power supply. CONSTITUTION:A transformer 1 steps down an AC power supply voltage to produce a control voltage which is then converted through a rectifier 2 into a DC voltage which is boosted by a factor of 5-10 through a DC/DC converter 4 to produce a high voltage for charging a backup capacitor 7. When the AC power supply voltage drops due to fault, a backup switching circuit 8 controls a capacitor power supply according to the level decision result of a level decision circuit 10 to produce a constant voltage which is then fed to a voltage current detector.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for a voltage/current detection device for a power distribution line during a power outage.

0002

2. Description of the Related Art Conventionally, automation systems and fault detection systems attached to power distribution lines require backup of the power supply for several to several tens of seconds in the event of a power outage, and for this reason, batteries have conventionally been used for this purpose.

0003

For this reason, when a large current is required to back up the entire system, a large capacity battery that can supply a large current even though the backup time is short has been used. However, batteries that can supply large currents are not only large in size, but also have a guaranteed lifespan of only about 5 years, so this invention has the problem of being insufficient as a long-term backup power source. This was done to solve technical problems, and it was done with the focus on the fact that the smaller the capacitance of the capacitor used for backup, the lower the cost, weight, and bulk. It is an object of the present invention to provide a power supply circuit for a voltage/current detection device for a power distribution line during a power outage, which is suitable as a backup power source for a long period of time, and which can downsize the entire system.

0004

[Means for Solving the Problems] The present invention includes a transformer that steps down an AC power supply to approximately the control power supply voltage of a voltage/current detection device, a rectifier that converts this into direct current, and a DC/DC transformer that steps up the rectified voltage. a DC converter and the DC/D
A voltage-capacitive backup capacitor connected to the output side of the C converter to be charged; a level determination circuit that determines the level of a predetermined voltage when the voltage drops due to an accident in the AC power supply; The gist thereof is that the backup switching circuit is activated in response to the result of level determination and controls and supplies the capacitor power supply to a constant voltage to the voltage/current detection device.

[0005]

[Operation] With the above configuration, normally the transformer is AC
The power source is stepped down to a control voltage, and a rectifier converts it to direct current. The DC/DC converter boosts the rectified voltage to
The voltage-capacitive backup capacitor is charged with the boosted high charging voltage. When the voltage drops to the specified voltage due to an AC power supply accident, the level judgment circuit judges the level,
The backup switching circuit controls and supplies the capacitor power supply to a constant voltage to the voltage/current detection device in response to the level determination result of the level determination circuit.

[0006] The present invention proposes that the higher the charging voltage of a backup capacitor, the longer the time (
backup time) becomes longer. Working voltage + margin ≦ charging voltage - (consumption voltage) Note that the consumption voltage refers to the voltage that is naturally discharged, and the working voltage refers to the voltage used in the circuit of the voltage and current detection device.

[0007]

[Example] An example embodying this invention is shown below in Figure 1.
Explain according to the following. A system supply power supply circuit 11 of the voltage and current detection device is connected to an AC 100V power supply that is a power distribution line. The system supply power circuit 11 is a transformer,
It is composed of a rectifier, a stabilizing power supply IC, etc., and is connected to the control circuit 12 of the voltage/current detection device to supply power. Note that the control power supply voltage of this control circuit 12 is 5V.
It becomes.

Next, backup circuit B will be explained. The primary side of the transformer 1 is a common AC100V power supply connected to the primary side of the system supply power supply.
It is connected to a 0V power supply and reduces the voltage on the secondary side to 6V. Rectifier 2 is connected to the secondary side of transformer 1,
Convert alternating current to direct current. The DC/DC converter 4 is connected to the output side of the rectifier 2 via a capacitor 3 for noise absorption and converter startup, and is configured to boost the voltage to 50V, which is about 5.5 times. Note that since the control voltage of the control circuit of the voltage/current detection device is 5V, the charging voltage of the capacitor 7 may be 30V instead of the 50V. DC/
A voltage capacitor type capacitor 7 is connected to the positive terminal of the DC converter 4 through a series circuit of a diode 5 for blocking reverse current and a charge resistor 6 for preventing heat. This capacitor 7 is a capacitor that has a high charging voltage so that it can obtain a power capacity even if its capacitance is small, and its capacitance is 10,000 μF to 330 μF.
00 μF is appropriate.

The backup switching circuit 8 is connected to the voltage capacitance type capacitor 7, and can be switched and connected to the control circuit 12 of the voltage/current detection device using the capacitor 7 as a power source. This backup switching circuit 8 is constituted by a switching power supply IC, and is configured to step down the control voltage of the control circuit 12 of the voltage/current detection circuit to 5V. That is, as the capacitor 7 discharges, the voltage of the capacitor 7 decreases, but this backup switching circuit 8
corresponds to the voltage drop and applies control voltage to the control circuit 12 so as to secure the necessary control voltage of 5V. This application time is 3 to 5 seconds.

A level determination circuit 10 is connected to the secondary side of the transformer 1 via a rectifier 9. The level determination circuit 10 has its output side connected to the backup switching circuit 8, and outputs a level determination signal to the backup switching circuit 8 when the AC 100V power supply drops to 60V or less. When the level determination signal is input, the backup switching circuit 8 switches and connects the capacitor 7 as a power source to the control circuit 12 based on the signal.

Now, the operation of the backup circuit configured as described above will be explained. During normal operation, the control circuit 12 of the voltage and current detection device receives power from the system supply power supply circuit 11. On the other hand, in backup circuit B, a rectifier circuit 2, a DC/DC converter 4, a diode 5
, the capacitor 7 is charged via the resistor 6. Now, an accident has occurred on the power distribution line, and the voltage of the AC 100V power supply has dropped.
When the level determination circuit 10 detects that the voltage of the AC 100V power supply has reached 60V or less, the backup switching circuit 8
Outputs a level judgment signal to. Backup switching circuit 8
Based on the signal, the capacitor 7 is switched and connected to the control circuit 12 as a power source. Then, as the capacitor 7 discharges, the voltage of the capacitor 7 drops, and the backup switching circuit 8 adjusts the necessary control voltage of 5V to correspond to the voltage drop.
The control circuit 12 is controlled to ensure that the control voltage is 3.
Apply for about 5 seconds.

[0012] Normally, in the case of an AC 100V power supply, if a transformer that steps down the voltage to about 60V is used, a DC/DC converter is no longer necessary. However, in this case, there is a problem that the secondary winding etc. become correspondingly larger, and the entire transformer becomes larger. In this embodiment, the transformer 1 steps down the voltage at 6V, so the transformer 1 can be small, and the entire backup circuit can also be made small.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but may be constructed as follows. (a) It is not limited to AC100V power supply, but
Any AC power supply of 100 to 200V is sufficient, and transformer 1
The secondary side of the voltage should be configured to step down to 6 to 15V. (b) Voltage boosting of the DC/DC converter must be performed within the range of 30 to 60V. (c) Set the control power supply voltage of the control circuit of the voltage and current detection device to 5
Set within the range of ~15V. Note that when the control power supply voltage is 15V, the charging voltage of the capacitor 7 is at least 50V.
It is necessary to set it to V. Further, the boosting factor of the DC/DC converter is appropriately selected depending on the backup time, capacitor capacity, and charging time.

[0014]

[Effects of the Invention] As described in detail above, normally a capacitor used as a backup tries to cover the power supply capacity with its capacity, but the present invention provides control of a voltage and current detection device for a backup capacitor. Since the capacitor is charged at a voltage higher than the control power supply voltage of the circuit, it is possible to reduce the size, cost, weight, and bulk of the capacitor, and it is suitable as a backup power source for a long period of time. This has the excellent effect of making it more compact.

[Brief explanation of the drawing]

FIG. 1 is an electrical block circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

1... Transformer, 2... Rectifier, 4... DC/DC converter, 5... Diode, 6... Charge resistor, 7... Capacitor, 8... Backup switching circuit, 10... Level judgment circuit,
11...System supply power circuit, 12...Control circuit, B...
backup circuit.

Claims (1)

[Claims] Claim 1: A transformer that steps down the AC power supply to approximately the control power supply voltage of the voltage and current detection device, a rectifier that converts this to direct current, and a DC/DC that steps up the rectified voltage.
a converter, a voltage-capacitive backup capacitor that is connected to the output side of the DC/DC converter to be charged, and a level determination circuit that determines the level of a predetermined voltage when the voltage drops due to an accident in the AC power supply. and a backup switching circuit that is activated in response to the level determination result of the level determination circuit and supplies the capacitor power supply to the voltage and current detection device at a constant voltage. Power supply circuit during power outage.