JP2022146090A - Surge protection circuit for dc power distribution - Google Patents

Abstract

To provide a surge protection circuit for DC power distribution which can handle large currents and suppress follow currents.SOLUTION: In a surge protection circuit for DC power distribution 1 provided between a positive electrode terminal 31 and a negative electrode terminal 32, a gas discharge tube GDT12 is provided in series on a first current path 11 connecting the positive electrode terminal 31 and the negative electrode terminal 32, and a second current path 13 is provided in parallel with the first current path 11. A capacitor C14 and a semiconductor element 15, which is a thyristor, are provided in series on the second current path 13, a resistor R16 is provided in parallel with the capacitor C14, a current sensor 18 is connected to the first current path 11, and the output terminal of the current sensor 18 is connected to the semiconductor element 15 via a delay circuit in which a coil L19 and a capacitor C20 are connected in series.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a surge protection circuit using an SPD (Surge protective device) that protects equipment, devices, etc. from sudden high current/high voltage such as lightning.

2. Description of the Related Art Conventionally, there have been surge protection circuits using SPDs that protect equipment and devices from sudden large currents and large voltages (≈surges) such as lightning.

Surge protection circuits include those using a gas discharge tube (GDT) and those using a zinc oxide varistor (MOV).

For example, Patent Literature 1 discloses a configuration in which a thermal fuse that disconnects due to heat generated by deterioration of the varistor is integrally assembled with the zinc oxide varistor in order to prevent smoke and ignition due to thermal runaway of the zinc oxide varistor.

Japanese Patent Application Laid-Open No. 2003-229303

However, although the surge protection circuit using the gas discharge tube described above is compact and can handle a large current, in the case of a direct current circuit, a discharge (arc) continues to flow, resulting in damage to the circuit. "Follow-on" refers to a phenomenon in which, after the surge has ended, the discharge is maintained by the main power supply voltage of the device and the arc discharge in the gas discharge tube, and the current continues to flow in the circuit. AC power supplies (circuits) reach 0V due to zero crossing, but DC power supplies (circuits) do not reach 0V, so follow current countermeasures are required.

On the other hand, a surge protection circuit using a zinc oxide varistor does not generate a follow current, but is large in size and unsuitable for large currents. Also, the device itself is expensive.

Therefore, in order to deal with the above problems, it is an object of the present invention to provide a surge protection circuit for DC power distribution that can handle large currents and suppress follow currents.

In order to achieve the above object, the invention according to claim 1 is
A surge protection circuit for direct current distribution provided between a positive terminal and a negative terminal, comprising:
A gas discharge tube is provided in series on a first current path connecting the positive electrode terminal and the negative electrode terminal,
A second current path is provided in parallel with the first current path,
a capacitor and a semiconductor element are provided in series on the second current path;
A resistor is provided in parallel with the capacitor,
A current sensor is connected to the first current path, and the output terminal of the current sensor is connected to the semiconductor device via a delay circuit, in a surge protection circuit for DC power distribution.

Further, the invention according to claim 2 is
A surge protection circuit for direct current distribution provided between a positive terminal or a negative terminal and a reference potential point,
A gas discharge tube is provided in series on a first current path connecting the positive electrode terminal or the negative electrode terminal and the reference potential point,
A second current path is provided in parallel with the first current path,
a capacitor and a semiconductor element are provided in series on the second current path;
A resistor is provided in parallel with the capacitor,
A current sensor is connected to the first current path, and an output terminal of the current sensor is connected to the semiconductor device via a delay circuit, in a surge protection circuit for DC power distribution.

Further, the invention according to claim 3 is
3. The surge protection circuit for DC power distribution according to claim 1, wherein the current sensor is a current sensor using a Hall element.

In addition, the invention according to claim 4,
A surge protection circuit for DC power distribution according to any one of claims 1 to 3, wherein said delay circuit is an LC circuit in which a coil L and a capacitor C are connected in series.

Further, the invention according to claim 5 is
A surge protection circuit for direct current power distribution according to any one of claims 1 to 3, wherein said delay circuit is an RC circuit in which a resistor R and a capacitor C are connected in series.

Further, the invention according to claim 6 is
A surge protection circuit for DC power distribution according to any one of claims 1 to 5, wherein said semiconductor element is a thyristor.

INDUSTRIAL APPLICABILITY According to the present invention, a gas discharge tube that is compact, inexpensive, and capable of handling a large current while suppressing follow-current can be used in a surge protection circuit for a DC power distribution system. Also, in the present invention, the only component that deteriorates over time is the gas discharge tube, so the running cost can be reduced.

1 is a configuration diagram of a surge protection circuit for DC power distribution according to Embodiment 1 of the present invention; FIG. FIG. 4 is an explanatory diagram illustrating the operation of the DC power distribution surge protection circuit according to Embodiment 1 of the present invention; FIG. 4 is an explanatory diagram illustrating the operation of the DC power distribution surge protection circuit according to Embodiment 1 of the present invention; FIG. 4 is an explanatory diagram illustrating the operation of the DC power distribution surge protection circuit according to Embodiment 1 of the present invention; FIG. 4 is an explanatory diagram illustrating the operation of the DC power distribution surge protection circuit according to Embodiment 1 of the present invention; FIG. 4 is an explanatory diagram illustrating the operation of the DC power distribution surge protection circuit according to Embodiment 1 of the present invention; FIG. 6 is a configuration diagram of a surge protection circuit for DC power distribution according to another embodiment of the present invention;

(Embodiment example 1)
BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment according to the present invention will be described in detail below with reference to the accompanying drawings. However, the components described in this embodiment are merely examples, and the scope of the present invention is not limited to them. The surge protection circuit 1 of Embodiment 1 according to the present invention is provided to protect equipment and devices that receive DC power distribution from large currents and voltages such as lightning.

<Configuration of surge protection circuit 1 for DC power distribution>
A surge protection circuit 1 for DC power distribution according to Embodiment 1 is provided between a positive terminal 31 and a negative terminal 32 to which the main power supply voltage of the device is applied.

A gas discharge tube GDT 12 is provided in series on the first current path 11 connecting the positive terminal 31 and the negative terminal 32 .

The gas discharge tube GDT12 has a structure in which a gas is sealed in an insulator container 122 facing electrodes 121, and operates depending on the applied voltage. That is, even if a voltage lower than the threshold voltage is applied between the electrodes 121, the state of high impedance is maintained and no current flows between the electrodes 121. FIG. On the other hand, when a voltage higher than the threshold (such as an abnormally high voltage or high current (surge) generated suddenly by lightning or the like) is applied between the electrodes 121, the enclosed gas is ionized and the electrodes 121 An arc discharge occurs between them, and current flows to the ground side (negative terminal 32 in the first embodiment).

A second current path 13 is provided in parallel with the first current path 11, and a capacitor C14 and a semiconductor element 15 are provided in series on the second current path 13 in descending order of potential. A resistor R16 is provided in parallel with the capacitor C14. Specifically, a third current path 17 is provided in parallel with the second current path 13, and a resistor R16 is provided in series on the third current path 17. FIG.

A resistor R16 provided in parallel with the capacitor C14 is for consuming (discharging) the charge accumulated in the capacitor C14, and is, for example, a 1M (mega)Ω resistor. On the other hand, if the resistor R16 with an excessively large resistance value is used, the charge accumulated in the capacitor C14 cannot be consumed (discharged) until the next lightning strike, and the arc discharge of the gas discharge tube GDT12 cannot be extinguished.

A current sensor 18 is connected at a position on the first current path 11 where the potential is lower than that of the gas discharge tube GDT12. There are two current paths for outputting the current input to the current sensor 18. One of them, the fourth current path 21, is connected to the semiconductor element 15 via a delay circuit in which a coil L19 and a capacitor C20 are connected in series. It is connected to the. In the DC power distribution surge protection circuit 1 of Embodiment 1, the current sensor 18 is connected to the first current path 11 at a position where the potential is lower than that of the gas discharge tube GDT 12. However, it is not limited to this configuration. The current sensor 18 may be connected to the first current path 11 at a position having a higher potential than the gas discharge tube GDT 12 or at a position having the same potential.

The current sensor 18 is, for example, a current sensor using a Hall element, and converts the magnetic field generated around the current flowing in the first current path 11 into a voltage by the Hall effect of the Hall element and outputs the voltage. . Note that the output voltage is proportional to the current input to the current sensor 18 .

In the first embodiment, the current sensor 18 is a Hall element type current sensor. However, the current sensor 18 is not limited to this configuration. A configuration using an AC current transformer), a configuration using a DC CT (DC current transformer), or a configuration using a shunt resistor may be used. The shunt resistor should have a resistance value as low as possible, for example, several m (millimeters)Ω. Therefore, since the value of the voltage across the shunt resistor becomes small, an operational amplifier or the like capable of voltage amplification is provided together with the shunt resistor. The operational amplifier or the like detects the voltage of the shunt resistor, amplifies the voltage, and outputs it. Alternatively, if the voltage generated across the shunt resistor is large, the configuration may be such that only the shunt resistor is used without using an operational amplifier or the like.

A delay circuit in which the coil L19 and the capacitor C20 are connected in series serves to delay the voltage output from the current sensor 18 in terms of time.

If the voltage output from the current sensor 18 is delayed too much (=long delay time), the time for the current to flow through the gas discharge tube GDT 12 on the first current path 11 will be longer, and the gas discharge tube GDT 12 will be damaged due to overload. On the other hand, if the delay is insufficient (short delay time), the surge cannot be completely eliminated.

Therefore, the time constant of the delay circuit in which the coil L19 and the capacitor C20 are connected in series (=the amount representing the speed of change from the transient state to the steady state, the delay time) is set to, for example, 60 to 100 μ (micro) sec. However, coil L19 and capacitor C20 are used. If a coil with an inductance of 1 mH (=1 milliHenry) is used as the coil L19 and a capacitor with a capacitance of 0.1 μF (=0.1 micro farad) is used as the capacitor C20, the time constant is 100 μ (micro ) sec.

In Embodiment 1, the configuration using the LC circuit in which the coil L19 and the capacitor C20 are connected in series is shown as the delay circuit. If so, it is not limited to this configuration. For example, an RC circuit in which a resistor R and a capacitor C are connected in series may be used, or a circuit in which a reactor and a capacitor C are connected in series may be used. In the case of a configuration using an RC circuit, for example, a resistor with a resistance value of 1 KΩ (=1 kΩ) is used as the resistor R, and a capacitor with a capacitance of 0.1 μF (=0.1 microfarad) is used as the capacitor C. If used, the time constant would be 100 μ(micro)sec.

Further, in Embodiment 1, the semiconductor element 15 is a thyristor. The output of current sensor 18 (fourth current path 21) is connected to the gate of this thyristor (labeled "G" in FIG. 1). Note that the anode of the semiconductor element 15 (indicated by “A” in FIG. 1) is connected to the capacitor 14 on the second current path 13 .

In addition, although the configuration using a thyristor as the semiconductor element 15 is shown in the first embodiment, the configuration is not limited to this. For example, instead of thyristors, FETs (field effect transistors), bipolar transistors, LGBTs, and triacs may be used. In that case, the output terminal of the current sensor 18 is connected to the gate of this FET, the base of a bipolar transistor, the gate of an LGBT, or the gate of a triac. Also, the drain of the FET (in the case of N-channel), the collector of the bipolar transistor, the collector of the LGBT, or the main terminal of the triac is connected to the capacitor C14.

The fifth current path 22, which is the other of the current paths for outputting the current input to the current sensor 18, is connected to the cathode of the semiconductor element 15, which is a thyristor (indicated by "K" in FIG. 1). is connected to the second current path 13 at a lower position.

Between the connection point of the capacitor C20 on the fourth current path 21 and the connection point of the semiconductor element 15, and between the connection point of the capacitor C20 on the fifth current path 22 and the connection point of the second current path 13 A diode 24 is provided on the connected sixth current path 23 with the direction of the fourth current path 21 as the cathode. This diode 24 is for protecting the semiconductor element 15 from sudden voltage/current. More specifically, in Embodiment 1, a reverse voltage is applied from the cathode to the gate of the semiconductor element 15, which is a thyristor, so that a reverse voltage is not applied from the cathode (indicated by "K" in FIG. 1) side. to prevent the current from flowing.

The second current path 13 is connected to the first current path 11 at a position where the potential is lower than the location where the current sensor 18 is connected.

<Operation of surge protection circuit 1 for DC power distribution>
Next, the operation of the DC power distribution surge protection circuit 1 according to the first embodiment will be described with reference to FIGS.

When a surge suddenly occurs due to lightning or the like and a voltage exceeding the threshold value is applied between the electrodes 121 of the gas discharge tube GDT 12, as shown in FIG. is ionized, arc discharge occurs between the electrodes 121, and current flows from the positive terminal 31 to the negative terminal 32 on the ground side.

When current flows through the first current path 11 due to a surge, the current sensor 18 converts the current into a voltage and outputs the voltage, as shown in FIG. However, since the delay circuit in which the coil L19 and the capacitor C20 are connected in series is connected to the current sensor 18, the voltage is output to the gate of the semiconductor element 15, which is a thyristor, with a delay. The semiconductor element 15 to which the voltage is applied to the gate is turned on (the anode and the cathode are electrically connected).

As a result, as shown in FIG. 4, the voltage between the electrodes 121 of the gas discharge tube GDT12 associated with the first current path 11 is reduced to becomes 0V. When the voltage between the electrodes 121 becomes 0 V, the follow current based on the arc discharge disappears (=arc extinction).

After that, as shown in FIG. 5, even if a voltage is applied from the main power source, no current flows between the electrodes 121 of the gas discharge tube GDT12. 15 is in the ON state, current flows through the second current path 13 and the capacitor C14 is charged.

Then, as shown in FIG. 6, when the charging of the capacitor C14 is completed, the semiconductor element 15 is turned off (the anode and the cathode are in a non-conducting state). The charge accumulated in the capacitor C14 is consumed (discharged) by the resistor R16 provided in parallel.

In this way, the gas discharge tube GDT12, which is compact, inexpensive, and capable of handling a large current while suppressing the follow-current, can be used in a surge protection circuit for DC power distribution. Moreover, in the DC power distribution surge protection circuit 1 according to Embodiment 1, the only component that deteriorates over time is the gas discharge tube GDT 12, so the running cost can be reduced.

In addition, although the configuration in which the surge protection circuit 1 for DC power distribution is provided between the lines is shown in the first embodiment, the present invention is not limited to this configuration, and as shown in FIG. A surge protection circuit 1 for direct current power distribution may be provided at the positive electrode or the negative electrode and the reference potential point).

However, when the surge protection circuit 1 for DC power distribution is provided between ground, it is needless to say that detailed changes such as the orientation of the elements and addition/deletion of elements may be required.

For example, when a thyristor is used as the semiconductor element 15 and a surge protection circuit for DC power distribution according to the present invention is provided between the positive electrode and the reference potential point to ground, the configuration shown in FIG. 7 can be used as it is. However, in order to exhibit the function of the present invention not only between the positive electrode and the reference potential point to ground, but also between the negative electrode and the reference potential point to ground, a thyristor having a direction opposite to that of the thyristor related to the semiconductor element 15 must be placed on the circuit. should be added to

When a triac is used as the semiconductor element 15, the configuration shown in FIG. 7 can be used as it is regardless of whether it is between the positive electrode and the reference potential point to ground or between the negative electrode and the reference potential point to ground. However, the diode 24 need not be provided.

Reference Signs List 1: surge protection circuit for direct current distribution, 11: first current path, 12: gas discharge tube GDT, 121: electrode, 122: insulator container, 13: second current path, 14: capacitor C, 15: Semiconductor element 16: resistor R 17: third current path 18: current sensor 19: coil L 20: capacitor C 21: fourth current path 22: fifth current path 23: sixth current path, 24: diode, 31: positive terminal, 32: negative terminal

Claims (6)

A surge protection circuit for direct current distribution provided between a positive terminal and a negative terminal, comprising:
A gas discharge tube is provided in series on a first current path connecting the positive electrode terminal and the negative electrode terminal,
A second current path is provided in parallel with the first current path,
a capacitor and a semiconductor element are provided in series on the second current path;
A resistor is provided in parallel with the capacitor,
A surge protection circuit for DC power distribution, wherein a current sensor is connected to said first current path, and an output terminal of said current sensor is connected to said semiconductor element via a delay circuit. A surge protection circuit for direct current distribution provided between a positive terminal or a negative terminal and a reference potential point,
A gas discharge tube is provided in series on a first current path connecting the positive electrode terminal or the negative electrode terminal and the reference potential point,
A second current path is provided in parallel with the first current path,
a capacitor and a semiconductor element are provided in series on the second current path;
A resistor is provided in parallel with the capacitor,
A surge protection circuit for DC power distribution, wherein a current sensor is connected to said first current path, and an output terminal of said current sensor is connected to said semiconductor element via a delay circuit. 3. A surge protection circuit for DC power distribution according to claim 1, wherein said current sensor is a current sensor using a Hall element. 4. A surge protection circuit for DC power distribution according to claim 1, wherein said delay circuit is an LC circuit in which a coil L and a capacitor C are connected in series. 4. A surge protection circuit for DC power distribution according to claim 1, wherein said delay circuit is an RC circuit in which a resistor R and a capacitor C are connected in series. A surge protection circuit for DC power distribution according to any one of claims 1 to 5, characterized in that said semiconductor element is a thyristor.

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