JPS6166530A - Rush current limiting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to the power-on operation when an electronic device is turned on. The present invention relates to a circuit for limiting the current to IB1, and particularly to an inrush current limiting circuit suitable for limiting inrush current using a resistor.

[Background of the invention]

AC-DC is an efficient DC power source in modern electronic devices.
Switching type power supplies, which are one type of converter type, are increasingly being used. This power supply uses a method that directly rectifies the AC line and smoothes it using a capacitor, so it can generate an excessive inrush current when the input is turned on. In addition, even in a 7'C device using a transformer, etc., a starting current several tens of times the normal current flows during the cycle due to the excitation of the transformer. On the other hand, the '1d power supply equipment absorbs the above-mentioned inrush current and has a high power supply capacity. Currently, we are trying to save resources by giving a certain amount of margin, and with Nariko-so W in, etc., which is a load, it is absolutely necessary to limit the transient inrush 4 flow at the time of input. be. Various methods have been devised to limit this. Here, the present invention relates to an inrush current limiting circuit system that utilizes the sequential operation of relay contacts, which is the most single and reliable among them, and these VCs will be explained.

FIG. 1 is a general inrush current limiting circuit using a beam lane-tance. In the figure, input terminals 1 and 2VC are supplied with AC input power. In order to supply input power to the load device 10 (which may be a DC input power source), the relay 4 is driven by first closing the switch 3, and its contact point 6 is closed. Therefore, power is supplied to the load device 10 through the resistor 9. Here, since the resistor 9 is completely passed through, even if the input impedance of the load device [10 is low at the initial stage of power-on, the impedance after the input terminal becomes equal to or higher than the resistance value of the resistor 9 due to this simple insertion, and the inrush current is limited. Thereafter, the relay 5 is driven by closing the relay contact 7, and its contact, the relay contact 8, is closed, and the input power source and the load device are connected through the relay contact 8, and a normal power supply state is established. Here, in order to set the inrush current limit time according to the time during which the inrush current flows when the load device 100 is turned on, the operating time of the relay 5 can be adjusted. This can be done by configuring the relay 5 as a delayed operation type. be.

The operation status of each of these relays is shown in FIG. 2. Although inrush current can be prevented in such a temporary manner, this circuit system has the following drawbacks. This is because when the relay 5 is inoperable due to a failure in the relay 5 itself, or when the relay contact 8 has a poor contact, a current equivalent to the steady-state input current of the load device 10 constantly flows through the resistor 9. become. Therefore, for resistor 9 (R1), use a resistor with a power capacity that can withstand them, or use a product with a power capacity that can withstand short-term rush currents, and detect the temperature during the above-mentioned constant excessive power consumption. Therefore, there is a drawback that it is necessary to take a method of stopping the driving of the relay 4.

This is a method that eliminates the need to use an unnecessary power capacity product such as resistor 9 and to install a temperature detector to deal with abnormalities such as relay inoperation and poor contact of its contacts, which are the shortcomings of the circuit system shown in Figure 1. In this case, it is sufficient to operate the relay 4 shown in FIG. 1 only for a certain period of time and use a resistor that can withstand the power capacity during that period. To achieve this kind of operation, the method of using an electronic circuit rather than a relay sequence and driving the relay coil with a semiconductor is cost-effective and generally used.
This method will now be explained with reference to FIG.

In the M3 diagram, first, by closing switch 3, a signal is input to the human power of the multivibrator circuit 11, and a signal for a certain period of time is output. This signal is applied to the base of transistor 15, and transistor 15 is turned on during the time that the signal is applied to its base, driving subv-4. So relay 4
The contact point 6 of the relay is closed. Therefore, power is supplied to the load device 10 through the resistor 9. The inrush current limiting operation resulting from this operation is similar to the circuit operation shown in FIG. 1, and will therefore be omitted here. On the other hand, a signal due to the closed state of the switch S is input to the delay circuit 12, and a signal is output after a certain period of time has elapsed. The output signal of is applied to the base of transistor 14, turning transistor 14 on. This causes the relay 5 to be driven.

Therefore, relay contact 8, which is the contact of relay 5, is closed.
The input power source and the load device are connected through the relay contact 8, and a normal power supply state is established. Here, in order to set the inrush current limit time according to the time during which the inrush current flows when the load device 100 is turned on, the one-shot multi-bar (7'L/-
This is possible by adjusting the output signal time of 1 and the delay time of the delay circuit 12 by 11. In this case, it is necessary to set the time at which the relay 5 starts to be driven before the relay 4 stops driving.

A series of these operating conditions is shown in Figure 4. In this circuit system, the time for the current to flow through resistor 9 (R1) is limited to within the output signal time of one-nine-t multi-biflator 11. Resistance 9 may also occur due to poor contact at contact 8.
1C does not have the drawback that the current continues to flow through the load device 100 for a long time, and the power level increasing force of the resistor 11 eliminates the safety of the energy level detector.

However, although this circuit system can solve the problems caused by malfunctioning of the relay or abnormal conditions due to poor contact of its contacts as shown in Figure 1, because the relay drive circuit is composed of electronic circuits, it has the following problems. There are drawbacks. This is most likely due to an abnormality in which a signal is constantly sent to the transistor 13 due to damage to the one/wire multivibrator 11, or damage to the 7-J-to-mode between the collector and emitter of the transistor 15. In such an abnormality, the relay 4 remains driven all the time. Therefore, the relay contact 6, which is the contact point, remains closed even if the switch 5 is opened and the relay contact 8 is also opened, and has a resistance? Since the constant current of the load device 10 continues to flow through the IC, the same measures as those shown in the circuit system shown in FIG. 1 are required. Furthermore, considering that poor contact of relay contacts and damage to semiconductor elements are particularly common in % of component failures compared to elements such as resistors and capacitors, it is essential to solve the above-mentioned drawbacks.

[Purpose of the invention]

The object of the invention was the drawbacks of the prior art described above. An object of the present invention is to provide an inrush current limiting circuit that can reliably prevent the steady current of a load device from continuously flowing through a resistor provided for the purpose of limiting inrush current even in the event of relay failure or electronic circuit failure. .

[Summary of the invention]

The disadvantage of conventional circuits is that it may not be possible to ensure that the relay contact of the line into which the resistor is inserted remains closed for a certain period of time.
In the circuit shown in the figure, a capacitor is inserted between the relay No. 4 and the collector of the transistor No. 13, which is less likely to cause a failure, and the capacitor prevents failure in the short-circuit mode of the transistor No. 13 or when the signal continues to be applied to the pace. The solution is to prevent the relay from continuing to be driven.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Fifth
In the figure, 1.2 is an input terminal to which AC input or DC input power is supplied. 1o is a load device that operates by receiving the input power, and 6 and 8V'i relay contact 9 is a resistor, so these three points serve to limit the rush current when the 10 load devices are turned on. . 3 is a switch for turning on the power, which starts turning on the input power to the 10 load devices. Reference numeral 12 denotes a signal delay circuit which, when a signal is input, outputs a signal with a fixed delay time from when the signal is applied. 13 and 14 are transistors for driving relays 4 and 5, respectively, and 15 is a capacitor related to the present invention. Here, the 16 resistors are for discharging the charging current of the 15 capacitors when unnecessary.

Next, the operation of this circuit will be explained. First, the operation of this circuit is started by closing the switch 3. switch 5
When closed, the 'HL source voltage VCC is applied to the pace of transistor 13 as a voltage signal divided by resistors 17 and 18. Then, the transistor 13 is turned on and its collector and emitter become conductive. Then, a charging current flows into the capacitor 15 from the 1α voltage VCC through the relay coil 4. This current also flows through the relay coil 4Vc at the same time, exciting the coil. Then, the relay contact 6 is closed, and the input power is passed through the resistor 97 to the load device 10:
Supplied. The operation that limits the inrush current during this period is the first
The circuit operation is the same as that shown in the figure and will not be described here. On the other hand, a signal due to the closed state of the switch 3 is input to the delay circuit 3.

After a certain period of time after the signal is applied to the input, a signal is generated at the output and applied to the transistor 140, and the collector-emitter of the transistor 14 becomes conductive and the relay 5 is activated.
is excited and the relay contact 8 is closed, and the input power source and the load device 10 are connected through the relay contact 8 and a normal power supply state is established.

Next, we will explain how the charging current to the capacitor t15 changes after the start of charging, assuming that the capacitance of the capacitor 11 is (CuF), the resistance of the IJ coil 4 is (R2O), and the resistor 16 is ignored (current (1)). As time progresses, the flow becomes smaller.

For this reason, the first current flowing to the V-coil 4 also changes according to the value of equation (1), and the relay contact 6 becomes open after a period of time when the circulating current value becomes such that the relay contact 6 cannot be kept in a closed state. This time is determined by ensuring that the contacts of the relay coil 4 are closed, the DC value and its resistance, the power supply 4 voltage VCC, and the capacitance value of the capacitor 15. To set the time, increase or decrease the respective values of the power/den f15. It's the best. In this way, to set the inrush d current limit time according to the inrush lightning time when the load device 100 is turned on,
Capacity of Conde/115 and delay time of delay circuit 12 is 1I
This is possible by adjusting the illumination. Here, it is necessary to set the delay time of the delay circuit 12 so that the relay contact 8 is closed before the relay contact 6 is opened. Next, when the switch 6 is opened thereafter, the signal application to the base of the transistor 13 is stopped, and the collector-commission terminal of the transistor 13 becomes non-conductive. Here, the charging power of the capacitor 15 is discharged through the resistor 16. Also, the current to the relay coil 4 is now 1' (no longer flowing. At the same time, the current to the delay circuit 1 is no longer flowing.
Application of a signal to the input of transistor 2 is also stopped, a signal from its output is also stopped, and application of a signal to the pace of transistor 14 is also stopped, and the collector-emitter of transistor 14 becomes non-conductive. The voltage application to the relay 5 is then stopped, and the relay contacts 8 are opened. This rL causes the supply of input power to the load device i10 to be stopped. The role of the resistor 16 is to discharge the charging power of the capacitor 15, so it must be set to a resistance value that allows the charging power in the capacitor 15 to be completely discharged before the switch 3 is turned from the open state to the closed state. is necessary. Now, the problem explained in the circuits of Figures 1 and 2 was poor contact of the relay contacts and '4.
Relay contact 6 for electronic path and semiconductor short circuit mode
As for whether or not the capacitor y''15 remains closed, this circuit uses the charging current of the capacitor 15 to drive the relay contact 6 that passes current through the inrush current limiting resistor value. The contact will not close unless the charged #ItmC force is discharged.

In other words, once the collector-emitter of the transistor 13 becomes conductive, it once becomes non-conductive, and unless the capacitor f15 discharges and then becomes conductive, the relay contact 6 will not close. Is the relay contact 6 a resistor only if the closed state occurs within the time shown by equation (1)? Since the steady current of the VC load device 10 does not continue to flow, there is no need to increase the capacity of the resistor 9 or install a temperature sensor. An abnormality in which the relay contact 6 remains closed may occur if the capacitor 15 is short-circuited and the transistor 16 is short-circuited at the same time, but considering the probability of a double failure and short-circuit mode failure of the capacitor, it is almost impossible. I can say it.

〔Effect of the invention〕

According to the present invention, the load device is used as the inrush current limiting resistor during abnormal conditions, such as poor contact of contacts, non-operation of electronic circuits, and short-circuit mode failures of semiconductors for driving relays, which are particularly prone to failure among the components of inrush current limiting circuits. Since a steady current does not continue to flow, and the power capacity of the inrush current prevention resistor is increased, there is no need to detect the temperature of the resistor. In addition, the capacitor insertion also serves as a one-seven-watt multivibrator, so the one-shot multivibrator circuit shown in FIG. 4 becomes unnecessary, and the inrush current limiting circuit can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an inrush current limiting circuit using a conventional relay configuration, FIG. 2 is a diagram showing the operation of FIG. 1, and FIG. 3 is a diagram showing a conventional circuit in which the relay operation is configured using an electronic circuit. Fourth
5 is a circuit diagram showing an embodiment of the present invention, and FIG. 6 is an explanatory diagram of the operation. 1...Input terminal, 2...Input terminal, 5-channel power supply switch, 4...Relay coil, 5゛・
・Relay coil, 6...4 relay contact 7・
...4 relay contact, 8...5 relay contact 9
...Inrush current limiting resistance, 1o...Load device, 11.
・One 7W multivibrator circuit, 12...
Delay circuit, 13...Transistor, 14...Transistor, 15...Capacitor, 16...Resistor,
17, 18...Resistance. 1st leap fZ map vz-r4LQ gorge - ゝゝ8←--Ronie-10・：Hikaku Denkyu 3rd map 4th section 5th map

Claims (1)

[Claims] In an inrush current limiting circuit consisting of a resistor that limits the inrush current when the device is turned on, a relay contact connected in series with the resistor, and a relay contact that flows a steady current, one of the coils that operates the relay contact connected in series with the resistor. A capacitor is connected in series to the pole, a step voltage is applied by a switch element to the pole opposite to the connection between the other pole of the coil and the coil pole of the capacitor, and the charging current of the capacitor is caused to flow through the relay coil. An inrush current limiting circuit for an electronic device characterized by temporarily closing a contact.