JPH11296238A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a rush current allowed to flow, when a contact is on, into a capacitive component in a power supply circuit wherein the input of a DC voltage is on/off controlled by the contact. SOLUTION: When the contact 1 of a power supply switch is turned on, a current is allowed to flow into the coil 21 of a relay, and for a period of several ms to several-tens ms up to the on of a contact 22 of the relay interlocking with the on of the contact 1, a current is allowed to flow from the contact 1 of the switch to a capacitive component part 42 in a main circuit part 41 through a current limiting resistor 3 so as to reduce the rush current allowed to flow into the part 42 when the contact 22 of the relay is turned on.

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 which receives a DC voltage and outputs a DC voltage.

[0002]

2. Description of the Related Art FIG. 2 shows a first example of a conventional power supply circuit having a circuit for preventing an inrush current. 2. Description of the Related Art Conventionally, in a power supply circuit in which a DC voltage input is turned on / off by a contact structure, a thyristor is provided as means for preventing an inrush current flowing to a capacitance component portion in the power supply circuit when the contact is turned on, and protecting the contact You are using

In FIG. 2, when a contact 1 of a power switch is turned on, a current flows through a coil 21 of a relay.
Even if the contact 22 of the relay is turned on and the contact 1 of the power switch is turned off, the same current as when the contact 1 of the power switch is turned on continues to flow through the coil 21 of the relay.
The relay is self-holding. Immediately after turning on the contact 1 of the power switch, the thyristor 5 is turned off, so that a current flows to the capacitance component section 42 of the main circuit 41 via the current limiting resistor 3. At this time, contact 1 of the power switch and contact 2 of the relay
2, the current limited by the current limiting resistor 3 flows.

Thereafter, the input voltage is divided by the current limiting resistor 3, the voltage dividing resistor 61 and the voltage dividing resistor 62, and when the divided voltage exceeds the gate trigger voltage of the thyristor 5, the thyristor 5 is turned on. Thereby, the main circuit 41
Is supplied via the thyristor 5.
At this time, since the capacitance component section 42 of the main circuit 41 is sufficiently charged via the current limiting resistor 3, the rush current when the thyristor 5 is turned on can be suppressed.

FIG. 3 shows a second example of a conventional power supply circuit having a circuit for preventing an inrush current. In the prior art shown in FIG. 3, a current limiting resistor 3 for preventing an inrush current is inserted in advance, and after the inrush current converges, a short-circuit contact 7 for short-circuiting the current limiting resistor 3 and an operation for operating the short-circuit contact 7 are provided. And an inrush current time setting circuit 8.

[0006]

However, in the first example of the conventional power supply circuit, in using the thyristor, there are many points to be considered such as the design of the current rating of the thyristor and the trigger circuit constant, the malfunction due to noise, and the like. There is an aspect that is difficult to use. There is also a problem that a large mounting area is required due to an increase in the number of components. Further, the normal relay can hold the contact with a smaller current when the contact is kept held than when the contact is turned on. However, the coil 21 of the relay of FIG. Since the same amount of current flows when holding the contacts, there is also a problem that the current consumption of the self-holding circuit of the relay is large.
Also in the second example of the conventional power supply circuit, there is a problem that a complicated circuit needs to be added in order to set the time until the rush current converges. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power supply circuit that is easy to use, has a small mounting area, and has low current consumption, with a simple circuit configuration.

[0007]

According to the present invention, there is provided a relay contact means for turning on / off an input current flowing to a main circuit by a contact of a relay, and to a capacitance component of the main circuit when the contact of the relay is on. A power supply circuit for preventing a rush current that flows, the object of the present invention is to provide a contact of a power switch connected in series to a coil of the relay, and a series connection between a contact of the power switch and the main circuit. And a resistor connected in series between a contact of the relay and a coil of the relay, wherein the resistor comprises:
When the contacts of the power switch are turned on, the current flowing through the contacts of the power switch is limited, and when the contacts of the relay are turned on, a current sufficient to maintain the ON state of the contacts of the relay is passed through the coil of the relay. Is achieved by:

[0008]

According to the power supply circuit of the present invention having the above configuration, the rush current can be reduced with a simple circuit configuration and with a small number of components.

FIG. 1 shows an embodiment of the present invention in correspondence with FIG. The contact 1 of the power switch is connected in series with the coil 21 of the relay with reference to the DC voltage input terminal of the power supply circuit and GND. Further, the contact 1 of the power switch is connected in parallel to the relay contact 22 and the current limiting resistor 3 connected in series.
The contact point 22 of the relay is connected in series between the DC voltage input terminal of the power supply circuit and the main circuit 41. The relay contact 22 is composed of the current limiting resistor 3 and the coil 2 of the relay.
1 are connected in series to those connected in series.
In the present invention, when the contact 1 of the power switch is turned on, a current flows through the coil 21 of the relay, and during a period of several ms to several tens of ms until the contact 22 of the relay is turned on in conjunction therewith,
A current flows from the contact 1 of the power switch to the capacitance component 42 of the main circuit 41 via the current limiting resistor 3. This allows
The effect of reducing the inrush current flowing to the capacitance component section 42 of the main circuit 41 when the relay contact 22 is turned on can be obtained. Further, when the contact 1 of the power switch is turned on, the rush current flowing to the capacitance component section 42 of the main circuit 41 can be limited by the current limiting resistor 3. Further, after the relay contact 22 is turned on, the current limiting resistor 3 is connected in series with the relay coil 21. Therefore, the current limiting resistor 3 has a size sufficient to maintain the ON state of the contact 22. Current flowing through the power supply can be limited.

[0010]

As described above, according to the present invention, the rush current flowing to the contact can be reduced at a low cost with a small number of parts as compared with the conventional method using a thyristor.
Further, low current consumption can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit using an inrush current prevention circuit according to the present invention.

FIG. 2 is a circuit diagram showing a first example of a power supply circuit using a conventional inrush current prevention circuit.

FIG. 3 is a circuit diagram showing a second example of a power supply circuit using a conventional inrush current prevention circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power switch contact 21 Relay coil 22 Relay contact 3 Current limiting resistor 41 Main circuit part 42 Capacitance component part 5 Thyristor 61 Voltage dividing resistor 62 Voltage dividing resistor 7 Short circuit contact 8 Inrush current time setting circuit

Claims (1)

[Claims] 1. A power supply circuit comprising: relay contact means for turning on / off an input current flowing to a main circuit by a contact of a relay, and preventing an inrush current flowing to a capacitance component of the main circuit when the contact of the relay is on. A contact of a power switch connected in series to the coil of the relay; and a contact of the relay and the coil of the relay connected in series between the contact of the power switch and the main circuit. A resistor connected in series between the power switch, the resistor limits a current flowing through the contact of the power switch when the contact of the power switch is on, and the resistor of the relay when the contact of the relay is on. A power supply circuit, comprising: a current limiting resistor for flowing a current sufficient to maintain an ON state of a contact to a coil of the relay.