JP2008306878A - Dc power switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power switch preventing a large rush current from a DC power supply to a load apparatus and power back-flow from the load apparatus to the DC power supply. <P>SOLUTION: First, a switch S2 is turned off so as to finish feeding. Charges accumulated in a capacitor C1 are discharged at a resistor R1 and the bias voltage of a transistor Q1 generated on the both ends of the resistor R1 begins to step down. The value of current via the transistor Q1 is gradually decreased. Finally, the transistor Q1 is put in an OFF state, and the switch S1 is concurrently turned off. Gradual reduction in power supply does not cause high counter-electromotive force at the load device 2, thereby preventing power back-flow to the DC power supply 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC power switch that can prevent a large inrush current from flowing from a DC power source to a load device and a reverse power flow from the load device to the DC power source.

  Conventionally, a power supply system using an alternating current power supply has been used, in which one-way power supply is performed.

  In recent years, there are demands for diversification of power supply methods and energy saving, and new power supply systems will be used in the future. That is, it is expected that a power supply system capable of distributed and bidirectional power supply using a small fuel cell, solar power generation, or thermal power generation technology is expected.

  FIG. 5 is a circuit diagram of a power feeding circuit in such a power feeding system.

  The DC power source 1 is expected to be used in such a power supply system. The DC power source 1 supplies power to the load device 2, and a switch 4 is inserted in the wiring therebetween. Although not shown, other load devices are similarly connected to the DC power source 1.

  By the way, in the AC power supply, since the magnitude of the output voltage changes, the inrush current to the load device may be reduced. However, since the DC power supply 1 always outputs a voltage within the nominal voltage range, a large inrush current always flows through the load device 2 when the switch 4 is turned on, regardless of the timing when the switch 4 is turned on. The cause of the inrush current is mainly the capacitor of the load device. In addition, there are many load devices having inverters, and there is a possibility that a large inrush current may flow regardless of the power consumption.

  As a result, the output voltage of the DC power supply 1 fluctuates, and other load devices may malfunction due to the voltage fluctuation and unnecessary electromagnetic waves due to such voltage fluctuation.

  FIG. 6 is a circuit diagram of a conventional power feeding circuit for preventing inrush current.

  Another switch 5 is inserted in the wiring between the DC power supply 1 and the load device 2, and a resistor R3 is connected in series to one of the terminals.

  In this power supply circuit, when the switch 5 is turned on before the switch 4 is turned on, the capacitor of the load device 2 is charged in advance. Accordingly, the current when the switch 4 is turned on can be lowered thereafter. A power supply circuit in which the function of the switch 4 is realized by a semiconductor may be used.

As a technique for preventing inrush current, a pseudo-inductance circuit is disclosed in Patent Document 1.
Japanese Patent No. 3881860

  Although the power supply circuit shown in FIG. 6 can limit the inrush current to a low level, it may cause inconvenience.

  For example, when the load device 2 has an inductive load such as a motor, a high back electromotive force is generated in the load device 2 when the switch 4 is turned off in order to end the power supply. Even though the resistor R3 is present, the back electromotive force increases because the change in the supplied power is abrupt.

  As a result, the output voltage of the DC power supply 1 fluctuates, and other load devices may malfunction due to the voltage fluctuation and unnecessary electromagnetic waves due to such voltage fluctuation.

  In addition, in a power supply circuit in which the function of the switch 4 is realized by a semiconductor, the semiconductor itself may malfunction due to a high back electromotive force in the load device 2.

  In addition, it is necessary to provide a storage battery (for example, a lead battery or a large-capacity capacitor) in the DC power source 1 in order to prevent voltage fluctuation.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a direct current power source capable of preventing a large inrush current from flowing from the direct current power source to the load device and a reverse power flow from the load device to the direct current power source. To provide a switch.

  In order to solve the above problems, the present invention of claim 1 is directed to a semiconductor element and a switch inserted in a positive or negative wiring between a DC power source and a load device, and a reverse current to the semiconductor element. A reverse current prevention semiconductor element connected in series to the semiconductor element for prevention, a resistive element connected in parallel between a bias control point of the semiconductor element and a reference point of the point, the resistance A capacitive element connected in parallel to the element, a resistive element having one end connected to the bias control point, a circuit connected in parallel to a series circuit of the two resistive elements, and a switch and a DC power supply connected in series A DC power switch characterized by comprising a bias circuit is provided as a solving means.

  The present invention of claim 2 is characterized in that the bias circuit includes a switch connected in parallel to the capacitive element and interlocked so that the on / off is reversed with the switch of the bias circuit. The DC power switch is the solution.

  According to the DC power supply switch of the present invention, a current flows through the series circuit of the DC power supply, the switch, the resistive element, and the capacitive element of the bias circuit, and there is a potential difference between both ends of the resistive element that generates the bias voltage of the semiconductor element. Although it is going to occur, since the capacitive element connected in parallel to the resistive element is in an uncharged state, the potential difference between both ends gradually increases after the switch is turned on. Thus, by gradually increasing the bias voltage of the semiconductor element, the value of the current that can be passed through the semiconductor element also gradually increases. Thereby, it can prevent that a big inrush current flows into a load apparatus.

  Further, when the switch of the bias circuit is turned off, the charge accumulated in the capacitive element is discharged by the resistive element connected in parallel, and the bias voltage of the semiconductor element generated at both ends of the resistive element starts to decrease. The value of the current that can be passed through the semiconductor element also gradually decreases. Eventually, the semiconductor element is turned off, and the switch inserted in the wiring at that time is turned off. Thus, since the supplied power gradually decreases, high back electromotive force is not generated in the load device, and power backflow to the DC power source connected to the wiring can be prevented.

  Also, when the switch connected in series to the DC power supply of the bias circuit is turned off and the interlocked switch is turned on, the charge accumulated in the capacitive element is discharged by the latter switch in a short time, and the bias voltage of the semiconductor element is also short. Decreases with time. The semiconductor element is also turned off in a short time, and the switch inserted in the wiring is turned off at that time. Since the power supply decreases in a short time, there is a possibility that a high back electromotive force may be generated in the load device, but even if this happens, the reverse current prevention semiconductor element prevents the power from flowing back to the DC power supply. can do.

  Therefore, according to the DC power supply switch of the present invention, the output voltage of the DC power supply connected to the wiring is stabilized, and other load devices are operated by voltage fluctuations that are problematic and unnecessary electromagnetic waves due to such voltage fluctuations. It is possible to prevent abnormalities. Therefore, the storage battery that is required to be provided in the DC power source can be made unnecessary or have a small capacity. Further, it is possible to prevent power backflow from the load device to the DC power source.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a circuit diagram of a power feeding circuit using a DC power switch according to the first embodiment.

  The DC power source 1 supplies power to the load device 2, and a DC power switch 3 is inserted into the positive-side wiring. The configuration in which the DC power switch 3 is provided on the positive-side wiring is employed when the negative-side wiring is grounded, although not shown.

  The DC power source 1 is, for example, a so-called 48V power source used in a communication station.

  The source of a transistor Q1, which is a power type N-channel MOSFET, is connected to the positive side of the load device 2. The cathode of a diode D1, which is a reverse current prevention semiconductor element for preventing reverse current of the transistor Q1, is connected to the drain of the transistor Q1. The positive electrode (shown by +) of the DC power supply 1 is connected to the anode of the diode D1 through the switch S1. A negative electrode (shown by −) of the DC power supply 1 is connected to the negative electrode side of the load device 2 by wiring. The bias circuit of the transistor Q1 is configured as follows. A resistor R1 that is a resistive element is connected in parallel between a gate that is a bias control point of the transistor Q1 and a source that is a reference point of the point, and a capacitor C1 that is a capacitive element is connected in parallel to the resistor R1. . One end of a resistor R2, which is a resistive element, is connected to the gate of the transistor Q1. The positive electrode of the DC power supply E1 is connected to the other end of the resistor R2 via the switch S2. The negative electrode of the DC power supply E1 is connected to the source of the transistor Q1.

  Next, the operation of this power feeding circuit will be described.

  Before power feeding, the switches S1 and S2 are turned off. When power feeding is started, the switch S1 is first turned on, and then the switch S2 is turned on.

  Then, a current flows through a series circuit of the DC power supply E1, the switch S2, the resistor R2, and the capacitor C1. A potential difference is generated between both ends of the resistor R1 that generates the bias voltage of the transistor Q1, but the capacitor C1 connected in parallel to the resistor R1 is in an uncharged state. Gradually grows. The time constant at that time is determined by the values of the resistor R2 and the capacitor C1. Thus, by gradually increasing the bias voltage of the transistor Q1 generated at both ends of the resistor R1, the value of the current that can be passed through the transistor Q1 also gradually increases. Thereby, it is possible to prevent a large inrush current from flowing to the load device 2. Further, when the bias voltage increases, the transistor Q1 is turned on. If transistors with low on-resistance are used for the transistor Q1 and the diode D1, the power loss in these elements can be made negligibly small.

  When power supply is ended, first, the switch S2 is turned off.

  Then, the charge stored in the capacitor C1 is discharged by the resistor R1, and the bias voltage of the transistor Q1 generated at both ends of the resistor R1 starts to decrease. The value of the current that can be passed through the transistor Q1 also gradually decreases. Eventually, the transistor Q1 is turned off, and at that time, the switch S1 is turned off. Thus, since the supplied power gradually decreases, high back electromotive force does not occur in the load device 2 and power backflow to the DC power source 1 can be prevented.

  Therefore, according to the direct-current power switch according to the first embodiment, the output voltage of the direct-current power supply 1 is stabilized, and other load devices are caused by voltage fluctuations that are a problem and unnecessary electromagnetic waves due to such voltage fluctuations. It is possible to prevent abnormal operation. Therefore, the storage battery that is required to be provided in the DC power source can be made unnecessary or have a small capacity. Since the supplied power gradually decreases, high back electromotive force is not generated in the load device, and power backflow to the DC power source connected to the wiring can be prevented.

[Second Embodiment]
FIG. 2 is a circuit diagram of a power feeding circuit using a DC power switch according to the second embodiment.

  As in the power supply circuit of the first embodiment, this power supply circuit is configured by inserting a DC power switch 3A into the positive-side wiring between the DC power supply 1 and the load device 2. The DC power switch 3A is formed by connecting in parallel a switch S3 that interlocks with the capacitor C1 of the DC power switch 3 according to the first embodiment so that the switch S2 is turned on and off. The configuration in which the DC power switch 3 </ b> A is provided on the positive-side wiring is adopted when the negative-side wiring is grounded although not shown.

  Next, the operation of this power feeding circuit will be described.

  Before power feeding, the switches S1, S2 and S3 are turned off. When power feeding is started, first, the switch S1 is turned on after the switch S1 is turned on.

  Similar to the first embodiment, a large inrush current is prevented from flowing into the load device 2.

  When power supply is terminated, first, the switch S2 is turned off, and the switch S3 is turned on in conjunction with it.

  The charge accumulated in the capacitor C1 is discharged in a short time by the switch S3, and the bias voltage of the transistor Q1 is also reduced in a short time. The transistor Q1 is also turned off in a short time, and the switch S1 is turned off at that time. Since the supplied power decreases in a short time, there is a possibility that a high back electromotive force is generated in the load device 2, but since the diode D1 is provided, the back electromotive force is prevented from flowing back to the DC power source 1. Can do.

  Therefore, according to the direct-current power switch according to the second embodiment, the output voltage of the direct-current power supply 1 is stabilized, and other load devices are caused by voltage fluctuations that have been a problem and unnecessary electromagnetic waves due to such voltage fluctuations. It is possible to prevent abnormal operation. Therefore, the storage battery that is required to be provided in the DC power source can be made unnecessary or have a small capacity. Further, even when a counter electromotive force is generated in the load device, the reverse current preventing semiconductor element can prevent the power from flowing back to the DC power source.

[Third Embodiment]
FIG. 3 is a circuit diagram of a power feeding circuit using a DC power switch according to the third embodiment.

  This power supply circuit is different from the power supply circuits of the first and second embodiments in that a DC power switch 3 </ b> C is inserted into a negative electrode wiring between the DC power supply 1 and the load device 2. The configuration in which the DC power switch 3B is provided on the negative electrode side wiring is employed when the positive electrode side wiring is grounded although not shown.

  The source of a transistor Q2, which is a power-type N-channel MOSFET, is connected to the negative electrode (shown by-) of the DC power supply 1. The cathode of a diode D2, which is a reverse current prevention semiconductor element for preventing reverse current of the transistor Q2, is connected to the drain of the transistor Q2. The negative side of the load device 2 is connected to the anode of the diode D2 via the switch S11. A positive electrode (indicated by +) of the DC power supply 1 is connected to the positive electrode side of the load device 2 by wiring.

  The bias circuit of the transistor Q2 is configured as follows. A resistor R11, which is a resistive element, is connected in parallel between a gate that is a bias control point of the transistor Q2 and a source that is a reference point of the point, and a capacitor C2 that is a capacitive element is connected in parallel to the resistor R11. . One end of a resistor R12, which is a resistive element, is connected to the gate of the transistor Q2. The positive electrode of the DC power supply E2 is connected to the other end of the resistor R12 via the switch S12. The negative electrode of the DC power supply E2 is connected to the source of the transistor Q2.

  Next, the operation of this power feeding circuit will be described.

  Before power feeding, the switches S11 and S12 are turned off. When power feeding is started, the switch S11 is first turned on, and then the switch S12 is turned on.

  Then, a current flows through a series circuit of the DC power supply E2, the switch S12, the resistor R12, and the capacitor C2. A potential difference is generated between both ends of the resistor R11 that generates the bias voltage of the transistor Q2. However, since the capacitor C2 connected in parallel to the resistor R11 is in an uncharged state, the potential difference between both ends is not changed after the switch S12 is turned on. Gradually grows. The time constant at that time is determined by the values of the resistor R12 and the capacitor C2. Thus, by gradually increasing the bias voltage of the transistor Q2 generated at both ends of the resistor R11, the value of the current that can be passed through the transistor Q2 also gradually increases. Thereby, it is possible to prevent a large inrush current from flowing to the load device 2. Further, when the bias voltage increases, the transistor Q2 is turned on. If transistors with low on-resistance are used for the transistor Q2 and the diode D2, the power loss in these elements can be made negligibly small.

  When power supply is terminated, first, the switch S12 is turned off.

  Then, the charge accumulated in the capacitor C2 is discharged by the resistor R11, and the bias voltage of the transistor Q2 generated at both ends of the resistor R11 starts to decrease. The value of the current that can be passed through the transistor Q2 also gradually decreases. Eventually, the transistor Q2 is turned off, and at that time, the switch S11 is turned off. Thus, since the supplied power gradually decreases, high back electromotive force does not occur in the load device 2 and power backflow to the DC power source 1 can be prevented.

  Therefore, according to the direct-current power switch according to the third embodiment, the output voltage of the direct-current power supply 1 is stabilized, and other load devices are caused by voltage fluctuations that have been a problem and unnecessary electromagnetic waves due to such voltage fluctuations. It is possible to prevent abnormal operation. Therefore, the storage battery that is required to be provided in the DC power source can be made unnecessary or have a small capacity. In addition, since the supplied power gradually decreases, high back electromotive force is not generated in the load device, and power backflow to the DC power source connected to the wiring can be prevented.

[Fourth Embodiment]
FIG. 4 is a circuit diagram of a power feeding circuit using a DC power switch according to the fourth embodiment.

  As in the power supply circuit of the third embodiment, this power supply circuit has a DC power switch 3 </ b> C inserted in the negative-side wiring between the DC power supply 1 and the load device 2. The DC power switch 3C is formed by connecting in parallel a switch S13 that is linked to the capacitor C2 of the DC power switch 3B according to the third embodiment so that the switch S12 is turned on and off. The configuration in which the DC power supply switch 3C is provided on the negative electrode side wiring is adopted when the positive electrode side wiring is not shown, but is grounded.

  Next, the operation of this power feeding circuit will be described.

  Before power feeding, the switches S11, S12 and S13 are turned off. When power feeding is started, first, the switch S11 is turned on and then the switch S12 is turned on.

  Similar to the third embodiment, a large inrush current is prevented from flowing into the load device 2.

  When power supply is ended, first, the switch S12 is turned off, and the switch S13 is turned on in conjunction with it.

  The charge stored in the capacitor C2 is discharged in a short time by the switch S13, and the bias voltage of the transistor Q2 is also reduced in a short time. The transistor Q2 is also turned off in a short time, and at that time, the switch S11 is turned off. Since the supplied power decreases in a short time, there is a possibility that high back electromotive force is generated in the load device 2. However, since the diode D2 is provided, the back electromotive force is prevented from flowing back to the DC power source 1. Can do.

  Therefore, according to the direct-current power switch according to the fourth embodiment, the output voltage of the direct-current power supply 1 is stabilized, and other load devices are caused by voltage fluctuations that are problematic and unnecessary electromagnetic waves due to such voltage fluctuations. It is possible to prevent abnormal operation. Therefore, the storage battery that is required to be provided in the DC power source can be made unnecessary or have a small capacity. Further, even when a counter electromotive force is generated in the load device, the reverse current preventing semiconductor element can prevent the power from flowing back to the DC power source.

  Although the DC power switch has been described above, an NPN bipolar transistor, a P-channel MOSFET, a PNP bipolar transistor, or the like may be used instead of the N-channel MOSFET.

  The capacitor may be replaced with another capacitive element that can be charged and discharged. Further, the resistor may be replaced with another resistive element having a resistance value. Further, the light emitting diode may be replaced with another light emitting element capable of emitting light such as a light bulb. The diode may be replaced with another reverse current prevention semiconductor element that can prevent reverse current.

It is a circuit diagram of the electric power feeding circuit using the direct-current power switch concerning a 1st embodiment. It is a circuit diagram of the electric power feeding circuit using the direct-current power switch which concerns on 2nd Embodiment. It is a circuit diagram of the electric power feeding circuit which uses the direct-current power switch concerning a 3rd embodiment. It is a circuit diagram of the electric power feeding circuit using the direct-current power switch which concerns on 4th Embodiment. It is a circuit diagram of the electric power feeding circuit in the conventional electric power feeding system. FIG. 6 is a circuit diagram of a conventional power feeding circuit for preventing inrush current.

Explanation of symbols

C1, C2 ... Capacitors D1, D2 ... Diodes 1, E1, E2 ... DC power supply Q1, Q2 ... Transistors R1, R2, R3, R11, R12 ... Resistors S1, S2, S3, S11, S12, S13 ... Switch 2 ... Load Device 3, 3A, 3B, 3C ... DC power switch

Claims (2)

A semiconductor element and a switch inserted in the positive or negative wiring between the DC power source and the load device;
A reverse current prevention semiconductor element connected in series to the semiconductor element to prevent reverse current to the semiconductor element;
A resistive element connected in parallel between the bias control point of the semiconductor element and a reference point of the point, a capacitive element connected in parallel to the resistive element, and a resistance connected at one end to the bias control point A DC power supply switch comprising: an element; and a bias circuit including a circuit formed by connecting the switch and a DC power supply in series and connected in parallel to a series circuit including the two resistive elements. The bias circuit includes:
The DC power switch according to claim 1, further comprising a switch connected in parallel to the capacitive element and interlocked so as to be turned on and off in reverse with the switch of the bias circuit.

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