JPH0226223A - Rush current preventing circuit - Google Patents

Abstract

PURPOSE:To prevent a rush current and to prevent components from deteriorating by comparing the input with the output of a power switch in terms of voltage values, and controlling a circuit switch circuit by the comparison result. CONSTITUTION:When a magnet switch 2 is closed, AC input is supplied to a rectifier 3, and a triac 5a is cut off so that a rush current is prevented by a resistor 6. The contact of a relay 5b is connected in series with the triac 5b. The input voltage of the switch 2 is compared with its output voltage by a voltage comparator 7. When the drop of the output voltage is detected, the contact 5b is opened through a circuit switch control circuit 8, and a current is limited by a resistor 6. Accordingly, even if the switch 2 is chattered, the rush current is prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding the inrush current prevention circuit in a power supply device, the purpose of this invention is to improve the reliability of the power supply device by blocking inrush current generated due to malfunction of a magnetic switch, etc. Compare the input and output voltage values of the power switch in a rush current prevention circuit that includes a flow path switch circuit that opens and closes the current flow path and a resistor that is connected in parallel with the flow path switch circuit at the subsequent stage. The present invention is configured to include a voltage comparison circuit and a flow path switch control circuit that controls the flow path switch circuit based on the comparison result of the voltage comparison circuit.

[Industrial application field]

The present invention relates to an inrush current prevention circuit in a power supply device,
In particular, the present invention relates to an inrush current prevention circuit that is effective against inrush currents caused by malfunctions of electrically controlled power switches such as magnetic switches.

In recent years, power supplies have been controlled from host devices to turn on/off the power.
Many configurations that perform disconnection are now being adopted, and for this reason, magnet switches and the like are increasingly being used as power switches.

[Conventional technology]

FIG. 3 is a schematic configuration diagram showing a conventional general power supply device. As shown in the figure, in power supply A, the AC input is connected to a no-fuse breaker (NFB), which is an input protection circuit.
1 and magnet switches (M, S) 2 which are power on/off switches, and are led to a rectifier 3. This magnet switch 2 is set to 0N10FF by a signal from a control device (not shown), and the power is turned on/off.
Disconnection is controlled.

The AC input via the magnet switch 2 is also led to a power failure alarm detection circuit 4, where voltage fluctuations are monitored. As shown in FIG. 4, this power failure alarm detection circuit 4 has a power failure alarm set in the range (10 to 20 ■) between the minimum fluctuation value of AC input and the minimum operating capacity value of the power supply device, and the voltage Measures are being taken to prevent the fall.

Furthermore, a triac 5a as a flow path switch circuit for opening and closing the current path of AC input is provided downstream of the magnet switch 2, and a resistor 6 for preventing inrush current is interposed in parallel with the triac 5a to prevent inrush current. forming a circuit. In this inrush current prevention circuit, the triac 5a is cut off when the power is turned on, and the influence of the inrush current is blocked by the resistor 6. After a certain period of time, the triac 5a is turned on by the signal 3a from the rectifier 3. It was made so that

[Problem to be solved by the invention]

In the conventional power supply device described above, when the signal from the control device that controls the magnetic switch fluctuates due to noise, etc., the magnetic switch malfunctions, causing sudden voltage fluctuations due to chattering, etc., and causing inrush current. There was a problem with letting it happen.

If this voltage fluctuation drops enough to be detected by the power outage alarm detection circuit, it will be recognized by the power outage alarm and countermeasures will be taken. This is a factor that impedes the reliability of the power supply device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an inrush current prevention circuit that prevents inrush currents generated due to malfunctions of magnetic switches, etc., and improves the reliability of power supply devices. do.

[Means to solve the problem]

In the present invention, means for achieving the above object includes a flow path switch circuit that opens and closes a current flow path, and a resistance connected in parallel with the flow path switch circuit, which is provided downstream of the power switch. The current prevention circuit includes a voltage comparison circuit that compares the input and output voltage values of the power switch, and a flow path switch control section that controls the flow path switch circuit based on the comparison result of the voltage comparison circuit. It is a circuit.

[Effect]

During power-on, a sudden change in voltage due to chattering or the like occurring in a power switch such as a magnetic switch due to malfunction or the like is detected by a comparison between the input voltage and output voltage of the power switch in a voltage comparison circuit. Through detection by this voltage comparison circuit, the flow path switch control circuit
A signal is issued to the flow path switch circuit to interrupt the current flowing through the flow path switch circuit. As a result, the current is diverted to a flow path that passes through the inrush current prevention resistor, thereby blocking inrush currents that occur due to sudden voltage fluctuations due to malfunctions, etc. while the power is turned on, and preventing performance deterioration due to component stress. I can do it.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a main part of a power supply device that is an embodiment of the present invention. In the same figure, when a magnet switch 2, which is a power switch, is turned ON, AC input is supplied to a rectifier 3, and a flow path switch circuit 5 that opens and closes a current path in that path, and this flow path switch circuit. The configuration in which a resistor 6 for inrush current prevention connected in parallel with 5 is interposed is the same as the conventional one. The flow path switch circuit 5 is also equipped with a triac 5a as in the past.
When the power is turned on, the current path is closed and the path of the resistor 6 prevents inrush current when the power is turned on. After a certain period of time, a signal 3a from the rectifier 3 opens the current flow path of the triac 5a, forming an inrush current prevention circuit when the power is turned on.

Further, in this embodiment, as shown in the figure, the flow path switch circuit 5 includes a relay (RL) 5 connected in series with the triac 5a.
b is provided. When this relay 5b is in the "OFF" state, the contacts close and current flows through it, and when it is "ON'", the contacts open and cut off the current. moreover,
A voltage comparison circuit 7 that compares the input voltage and output voltage of the magnetic switch 2, and a flow path that turns on the relay 5b when the voltage comparison circuit 7 detects a drop in the output voltage of the magnetic switch 2. A switch control circuit 8 is provided to form the entire inrush current prevention circuit.

The voltage comparison circuit 7 includes a transformer 71, a transformer 72, and a comparator 73. The transformer 71 steps down the input voltage of the magnetic switch 2 and inputs it to the negative terminal of the comparator 73, and the transformer 72 steps down the output voltage of the magnetic switch 2 and inputs it to the positive terminal of the comparator 73. The flow path switch control section 8 includes a capacitor 81. resistance 8
2. Diode 83. It is composed of a transistor 84 and a relay switch 85, and controls the relay 5b of the flow path switch circuit 5.

FIG. 2 is a waveform diagram illustrating the operation of the above circuit. As shown in the figure, when the magnetic switch 2 is in the normal "ON" state, the output of the comparator 73 does not change because the inputs to the positive and negative terminals of the comparator 73 are in-phase sine waves. However, if chattering or the like occurs due to a malfunction of the magnetic switch 2, the voltage on its output side decreases, so that the positive terminal voltage of the comparator 73 becomes lower than the negative terminal voltage, and the output becomes -VE. As a result, transistor 8
Since voltage ■1 is generated between the collector emitter of 4,
The relay switch 85 is activated and the relay 5b is turned ON. Even if the contact of the magnetic switch 2 is restored and the output of the comparator 73 becomes normal, due to the time constant of the capacitor 81 and the resistor 82, Since the voltage of , does not return immediately, the relay 5b remains "ON" for a while. Therefore, the inrush current that occurs when the magnet switch 2 returns is blocked by the inrush current prevention resistor 6. Ru.

In the above embodiment, the flow path switch circuit 5 is provided with a relay 5b and is controlled by the flow path switch control section, but of course, the conventional control line 3 of the triac 5a is
It is also possible to adopt a configuration in which a is controlled.

(Effects of the Invention) As explained above, according to the present invention, inrush current generated due to voltage drop due to malfunction of a t-source switch such as a magnet switch, which is not detected by a normally provided power failure alarm detection circuit, is prevented. It is possible to reduce the stress on the components and prevent performance deterioration, thereby providing an inrush current prevention circuit that improves the reliability of the power supply device.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a main part of an embodiment of the present invention, FIG. 2 is a waveform diagram illustrating the embodiment, FIG. 3 is a conventional configuration diagram, and FIG. 4 is an explanatory diagram of a power outage alarm. A; Power supply device, 1; No fuse breaker (NFB), 2; Magnetic switch (M, S), 3; Rectifier, 4; Power failure alarm detection circuit, 5; Flow path switch circuit, 5a; Triac, 5b; Relay 6; Resistor for inrush current prevention, 7; Voltage comparison circuit, 71.72;) Lance, 73: Comparator, 8; Flow path switch control circuit, 8 Capacitor, 82; Resistor, 83; Diode, 84; Transistor, 85; Relay switch. Figure 2: Degree shape diagram showing implementation OI∆i

Claims (1)

[Claims] A flow path switch circuit (5) that opens and closes a current flow path, and a resistor (6) that is connected in parallel with the flow path switch circuit (5) are installed after the power switch (2). In a rush current prevention circuit equipped with a voltage comparator circuit (7) that compares the input and output voltage values of the power switch (2), and a flow path switch circuit (5) based on the comparison result of the voltage comparator circuit (7), ) A flow path switch control circuit (8) for controlling the inrush current prevention circuit.