JP2016025711A - Dc power reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC power reception device capable of safely and efficiently receiving DC power.SOLUTION: There is provided the DC power reception device that comprises: a delay circuit for delaying change in a first potential difference which is a potential difference between a positive side output of DC power and a neutral point, and a second potential difference which is a potential difference between the neutral point and a negative side output of the DC power; a comparison circuit which is provided at the subsequent stage of the delay circuit, has a predetermined hysteresis, and compares magnitudes of the first potential difference and the second potential difference; and a changeover circuit for performing, when a result of the comparison circuit's comparison shows that a difference between the first potential difference and the second potential difference is equal to or larger than a predetermined amount, performs changeover in such a way that DC power is received from the larger of the first potential difference and the second potential difference.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a DC power receiving device.

  By providing a storage battery, there is an uninterruptible power supply that can continue to supply power from a storage battery to a connected device for a predetermined time without power failure even if the power from the input power supply is interrupted. It has been. A technology has been proposed in which such a power supply device is expanded to a consumer unit and power is supplied to the consumer when a power supply abnormality such as a power failure or a shortage of storage battery capacity occurs (see Patent Documents 1 and 2). .

JP 2011-208771 A JP 2013-90560 A

  In the power supply system for supplying DC power, when supplying DC power with three wires of the positive electrode wire, the negative electrode wire, and the neutral wire, when receiving the power with the positive electrode wire and the negative electrode wire, the positive electrode wire or the negative electrode wire, There is a case where power is received using a neutral wire. However, when power is received using a positive or negative line and a neutral line, if a problem such as the interruption of the neutral line occurs, a voltage higher than the expected voltage is applied to the device that receives the DC power. It will be applied.

  In addition, when power is received using a positive or negative line and a neutral line, if power is continuously received from either the positive line or the negative line, the DC power supply side is unbalanced and power is transmitted. Inefficiency.

  Therefore, the present disclosure proposes a new and improved DC power receiving device that can receive DC power safely and efficiently.

  According to the present disclosure, a first potential difference that is a potential difference between a positive output of DC power and a neutral point, and a second potential difference that is a potential difference between the neutral point and the negative output of the DC power. A delay circuit that delays a change in potential difference; a comparison circuit that is provided at a subsequent stage of the delay circuit, has a predetermined hysteresis, and compares the magnitudes of the first potential difference and the second potential difference; When the difference between the first potential difference and the second potential difference is greater than or equal to a predetermined amount as a result of the comparison by the comparison circuit, switching is performed so that DC power is received from the larger one of the first potential difference or the second potential difference. There is provided a DC power receiving device including a switching circuit.

  As described above, according to the present disclosure, it is possible to provide a new and improved DC power receiving apparatus that can receive DC power safely and efficiently.

  Note that the above effects are not necessarily limited, and any of the effects shown in the present specification, or other effects that can be grasped from the present specification, together with or in place of the above effects. May be played.

It is explanatory drawing which shows the structural example of the DC power transmission / reception system 1 which concerns on one Embodiment of this indication. It is explanatory drawing which shows the example of the receiving circuit by an alternating current 3-wire type electric power supply system. It is explanatory drawing which shows the example of the receiving circuit by a direct current | flow three-wire type power supply system. FIG. 3 is an explanatory diagram illustrating a configuration example of a power receiving circuit 300 provided in a DC power receiving device 200 according to an embodiment of the present disclosure.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. One Embodiment of the Present Disclosure 1.1. Outline 1.2. Configuration example 2. Summary

<1. One Embodiment of the Present Disclosure>
[1.1. Overview]
Before describing an embodiment of the present disclosure, an outline of an embodiment of the present disclosure will be described.

  Each customer is equipped with a battery server with a storage battery, and power is stored in the storage battery using power generated by natural energy such as commercial power, solar power, wind power, geothermal heat, and the power stored in the storage battery is used. It is expected that mechanisms for operating electrical products will become increasingly popular in the future. Based on the spread of such a mechanism, as described above, when there is a shortage of power in a battery server of a certain consumer, the battery server of the consumer having a shortage of power from the battery server of the consumer with sufficient power. A system has been devised for accommodating power to a battery server. When power is supplied between consumers, it is desirable from the viewpoint of efficiency that supply with DC power is performed in consideration of power supply from storage batteries.

  There are various DC power supply methods, and among them, a DC three-wire power supply method in which DC power is transmitted through three wires of a positive electrode wire, a negative electrode wire, and a neutral wire has been studied. For example, a direct current three-wire power supply system in which a voltage of 100 V is applied to the positive line and a voltage of −100 V is applied to the negative line, and a voltage near 0 V is output by being grounded at somewhere on the neutral line can be considered. .

  In such a power supply system that supplies DC power using the DC three-wire power supply system, when DC power is supplied through three wires, that is, a positive electrode wire, a negative electrode wire, and a neutral wire, There are cases where the electric power is received using a positive line or a negative line and a neutral line. However, when power is received using a positive or negative line and a neutral line, if a problem such as the interruption of the neutral line occurs, a voltage higher than the expected voltage is applied to the device that receives the DC power. It will be applied.

  In addition, when power is received using a positive or negative line and a neutral line, if power is continuously received from either the positive line or the negative line, the DC power supply side is unbalanced and power is transmitted. The efficiency becomes worse.

  Accordingly, the present disclosure has intensively studied a technique that enables receiving DC power safely and efficiently when receiving DC power. As a result, as will be described below, the present disclosure person greatly increases the risk that a voltage higher than the rated voltage will be applied even when trouble such as interruption of the neutral line occurs when receiving DC power. We have devised a technology that can reduce and efficiently receive DC power.

  Heretofore, an overview of an embodiment of the present disclosure has been described. Subsequently, a configuration example of an embodiment of the present disclosure will be described.

[1.2. Configuration example]
FIG. 1 is an explanatory diagram illustrating a configuration example of a DC power transmission / reception system 1 according to an embodiment of the present disclosure. Hereinafter, a configuration example of the DC power transmission / reception system 1 according to an embodiment of the present disclosure will be described with reference to FIG.

  A DC power transmission / reception system 1 according to an embodiment of the present disclosure illustrated in FIG. 1 is a system intended to supply power by DC. As illustrated in FIG. 1, a DC power transmission / reception system 1 according to an embodiment of the present disclosure includes DC power supply devices 100a, 100b, and 100c, and DC power reception devices 200a to 200e. .

  In FIG. 1, the DC power supply apparatus 100a is illustrated as a battery server including a battery, the DC power supply apparatus 100b is illustrated as an electric vehicle, and the DC power supply apparatus 100c is illustrated as a solar cell panel. .

  In FIG. 1, the DC power receiving device 200a is a washing machine, the DC power receiving device 200b is a refrigerator, the DC power receiving device 200c is a television receiver, the DC power receiving device 200d is a personal computer, and the DC power receiving device 200e. Are respectively shown as electric lamps. The DC power receiving devices 200a to 200e are devices that operate by receiving DC power directly in the home. In the following description, when it is not necessary to distinguish the DC power receiving devices 200a to 200e, they may be simply referred to as the DC power receiving device 200.

  The DC power transmission / reception system 1 according to an embodiment of the present disclosure supplies DC power from the DC power supply devices 100 a, 100 b, 100 c to the DC power reception devices 200 a to 200 e through the DC bus line 10. In the present embodiment, the DC bus line 10 is composed of three wires: a positive wire, a neutral wire, and a negative wire. For example, the rated voltage of the positive line may be + 100V, and the rated voltage of the negative line may be −100V. Of course, it goes without saying that the rated voltages of the positive and negative wires are not limited to such examples.

  The DC power supply devices 100a, 100b, and 100c can be connected to the DC bus line 10 through the power supply connector 20, respectively. The DC power receiving devices 200a to 200e can be connected to the DC bus line 10 by DC plugs 30, respectively. The shape and other specifications of the power feeding connector 20 and the DC plug 30 may be any as long as they are configured so that DC power can be transmitted and received by the DC bus line 10.

  In the DC power transmission / reception system 1 according to the embodiment of the present disclosure illustrated in FIG. 1, only one of the DC power supply devices 100 a, 100 b, and 100 c that supplies DC power is supplied to the DC bus line 10. It may be configured to have a control right to control power transmission / reception. For example, when the DC power supply apparatus 100a supplies DC power to the DC power reception apparatus 200a through the DC bus line 10, the DC power supply apparatus 100a first arbitrates the acquisition of the control right with the DC power supply apparatuses 100b and 100c, If both the DC power supply devices 100b and 100c have no control right, the DC power supply device 100a may acquire the control right and then supply DC power to the DC power reception device 200a.

  In the DC power transmission / reception system 1 according to the embodiment of the present disclosure illustrated in FIG. 1, the neutral line to which the DC power supply device 100 a that is a battery server is connected is grounded at one point. In addition, the location where the neutral wire is grounded in the DC power transmission / reception system is not limited to the location shown in FIG. 1, but the DC power transmission / reception system as a whole can be at one point regardless of where it is grounded. Only grounded.

  FIG. 2 is an explanatory diagram illustrating an example of a power receiving circuit using an AC three-wire power supply method. FIG. 3 is an explanatory diagram showing an example of a power receiving circuit using a DC three-wire power supply system. In the power receiving circuit according to the AC three-wire power supply system shown in FIG. 2, the terminal that becomes 100 VAC as viewed from the neutral line protrudes from both sides. Since one of the phases is inverted with respect to the other, the voltage between both terminals is 200 V in total.

  On the other hand, in the DC three-wire power supply method shown in FIG. 3, the neutral line is set to 0V, the plus terminal and the minus terminal are output, and + 100V is received at the plus terminal and −100V is received at the minus terminal. Therefore, the direct current three-wire power supply system is configured such that the potential difference between the plus terminal and the minus terminal is 200V.

  The DC power receiving devices 200a to 200e receive power from the DC bus line 10 composed of three wires, a positive wire, a neutral wire, and a negative wire. The DC power receiving devices 200a to 200e may receive power through a positive electrode line and a negative electrode line, and may receive power through a positive electrode or negative electrode line and a neutral line. That is, if the rated voltage of the positive line is + 100V and the rated voltage of the negative line is −100V, there can be a device with a rated voltage of 200V and a device with a voltage of 100V.

  When the rated voltage of the positive line is + 100V and the rated voltage of the negative line is −100V, for example, a DC power receiving device 200d illustrated as a personal computer or a DC power receiving device 200e illustrated as a lamp is used. Suppose that the device receives power by the positive or negative wire and the neutral wire, that is, a device having a rated voltage of 100V.

  If 200 V DC power is accidentally received by both the positive line and the negative line to a device having such a rated voltage of 100 V, a voltage twice as high as the rated voltage is applied. Therefore, if a device having a rated voltage of 100 V receives 200 V DC power by both the positive and negative wires, the device may be damaged.

  In addition, when DC power is supplied from the positive electrode wire, the negative electrode wire, and the neutral wire, if power is continuously received from either the positive electrode wire or the negative electrode wire, the DC power supply side The balance will be lost and the transmission efficiency will deteriorate. For example, when the positive line voltage is +95 V and the negative line voltage is −100 V and power is received by the positive line and the neutral line, the voltage of the positive line further decreases and the DC power is supplied. The balance will be lost. In such a case, it is desirable that the power receiving side is automatically controlled so that power is received not by the positive electrode wire and the neutral wire but by the negative electrode wire and the neutral wire.

  Therefore, in the present embodiment, in a device that receives power through a positive or negative electrode and a neutral wire, the higher one of the voltages (absolute voltage values) of other terminals viewed from the neutral point is selected and connected. Configure as follows. Further, in the present embodiment, in a device that receives power through a positive or negative line and a neutral line, a circuit that detects a terminal having a high voltage is provided, the detection is delayed in the circuit, and hysteresis is provided. Configure to hold.

  In this way, it is configured to select and connect the higher voltage (absolute voltage value) of the other terminal viewed from the neutral point, and to configure the detection with a delay and hysteresis. Thus, according to the present embodiment, the device that receives power through the positive or negative electrode wire and the neutral wire safely receives DC power and suppresses frequent switching of terminals against instantaneous voltage fluctuations. It becomes possible.

  The configuration example of the DC power transmission / reception system 1 according to an embodiment of the present disclosure has been described above with reference to FIG. Subsequently, a configuration example of a power receiving circuit provided in the DC power receiving device according to an embodiment of the present disclosure will be described.

  FIG. 4 is an explanatory diagram illustrating a configuration example of the power receiving circuit 300 provided in the DC power receiving device 200 according to an embodiment of the present disclosure. The power receiving circuit 300 illustrated in FIG. 4 is a circuit that receives DC power transmitted through the DC bus line 10. Hereinafter, a configuration example of the power receiving circuit 300 provided in the DC power receiving device 200 according to an embodiment of the present disclosure will be described with reference to FIG.

  As illustrated in FIG. 4, the power receiving circuit 300 provided in the DC power receiving device 200 according to an embodiment of the present disclosure includes a comparator IC1 and relays RY1, RY1-1, and RY1-2. FIG. 4 also shows a DC main circuit 310 that operates by receiving direct-current power transmitted through the direct-current bus line 10 through a positive line or negative line and a neutral line. That is, the DC main circuit 310 operates at a rated voltage that is half of the rated voltage of the power supplied through the positive and negative lines. The power receiving circuit 300 shown in FIG. 4 is designed to receive a voltage up to +100 V with a positive line and a voltage up to −100 V with a negative line.

  The comparator IC1 is an element that compares voltages and changes the output according to the comparison result. In the present embodiment, the comparator IC1 compares an intermediate voltage obtained by dividing the voltage supplied by the positive and negative lines with resistors R1 and R2 and a neutral line voltage (neutral point). To do. In the present embodiment, the comparator IC1 compares the intermediate voltage obtained by dividing the voltage supplied by the positive and negative electrodes with a half of the resistors R1 and R2, and the neutral line voltage (neutral point). By doing so, the potential difference between the voltage of the positive line and the voltage of the neutral line is compared with the magnitude of the potential difference between the voltage of the neutral line and the voltage of the negative line. Then, the comparator IC1 outputs a result obtained by comparing a voltage intermediate between the voltages supplied through the positive line and the negative line with the voltage of the neutral line to the relay RY1. The neutral line is grounded at one point as shown in FIG. 4, and the voltage of the neutral line as a reference for voltage comparison basically does not change with the ground potential.

  The relay RY1 switches the relays RY1-1 and RY1-2 according to the output of the comparator IC1. If the result of comparing the intermediate voltage between the positive line and the negative line and the neutral line is 0 or more, the relay RY1 connects the positive line and GND to the DC main circuit 310. If the result is negative, the relay RY1 switches the relays RY1-1 and RY1-2 to connect the negative electrode line and GND to the DC main circuit 310. That is, if the intermediate voltage is equal to or higher than the neutral line voltage, the relay RY1 operates to connect the positive line and GND to the DC main circuit 310, and the intermediate voltage is the neutral line voltage. If it is lower, the relay RY1 operates to connect the negative line and GND to the DC main circuit 310.

  As described above, the comparator IC1 outputs to the relay RY1 the result of comparing the intermediate voltage supplied between the positive line and the negative line with the neutral line voltage. If the voltage of the DC bus line 10 frequently fluctuates, the result of comparing the voltage between the neutral line voltage and the intermediate voltage supplied by the positive and negative lines also changes frequently. If the result of comparing the intermediate voltage supplied between the polar line and the negative line with the voltage of the neutral line changes frequently, the switching operation by the relay RY1 also frequently occurs, and the switching operation is stable. I will not.

  Therefore, in the power receiving circuit 300 shown in FIG. 4, a capacitor C is provided on the input side of the comparator IC1. The capacitor C plays a role of slowing the voltage change on the input side of the comparator IC1 by the product of the resistance value of the resistor R1 and the capacitance of the capacitor C.

  Since the capacitor C is provided on the input side of the comparator IC1 and the voltage change on the input side of the comparator IC1 becomes slow, the power receiving circuit 300 suppresses the occurrence of instantaneous fluctuations in the input of the comparator IC1.

  In the power receiving circuit 300, since the voltage change on the input side of the comparator IC1 becomes slow, the output of the comparator IC1 does not change frequently, and the switching operation by the relay RY1 is prevented from being frequently performed, and the switching operation is performed. It can be stabilized.

  Note that the resistance value of the resistor R1 and the capacitance value of the capacitor C can be appropriately set according to design values such as a voltage value supplied by the positive and negative electrodes and a potential difference allowing switching. And is not limited to a specific value.

  The comparator IC1 has a hysteresis function. The comparator IC1 uses a hysteresis function to maintain a potential difference for a predetermined time when comparing the voltage between the voltage supplied by the positive line and the voltage supplied by the negative line with the voltage of the neutral line. If more than a predetermined amount is generated, the switching operation of the relays RY1-1 and RY1-2 can be controlled so that the relays RY1-1 and RY1-2 are switched.

  Note that the internal circuit configuration of the comparator IC1 for providing the comparator IC1 with a hysteresis function is not limited to a specific one. The hysteresis width when the comparator IC1 is provided with a hysteresis function is a value that can be appropriately set according to a design value such as a voltage value supplied through the positive line and the negative line, or a potential difference that allows switching. And is not limited to a specific value.

  The power receiving circuit 300 provided in the DC power receiving device 200 according to an embodiment of the present disclosure has a configuration as illustrated in FIG. 4, so that the voltage (an absolute value of the voltage) of other terminals viewed from the neutral point. ) Can be selected and connected.

  Further, the power receiving circuit 300 provided in the DC power receiving device 200 according to an embodiment of the present disclosure is configured to have a delay and a hysteresis in voltage detection as illustrated in FIG. DC power can be safely received by the DC main circuit 310, and frequent switching of the relays RY1-1 and RY1-2 can be suppressed against instantaneous voltage fluctuations.

  The configuration example of the power receiving circuit 300 provided in the DC power receiving device 200 according to the embodiment of the present disclosure has been described above with reference to FIG.

<2. Summary>
As described above, according to an embodiment of the present disclosure, when receiving DC power, there is a risk that a voltage higher than the rated voltage may be applied even when a trouble such as the interruption of a neutral wire occurs. There are provided a DC power receiving device 200 and a power receiving circuit 300 provided in the DC power receiving device 200 that can greatly reduce and efficiently receive DC power.

  In the power receiving circuit 300 according to an embodiment of the present disclosure, the comparator IC1 compares an intermediate voltage between the voltages supplied through the positive electrode line and the negative electrode line with the voltage of the neutral line. In addition, the power receiving circuit 300 according to an embodiment of the present disclosure outputs a result of comparing the voltage between the voltage supplied through the positive line and the negative line and the voltage of the neutral line from the comparator IC1 to the relay RY1. . And the power receiving circuit 300 which concerns on one Embodiment of this indication switches relay RY1-1, RY1-2 so that a voltage may be received from the one where a voltage (absolute value of a voltage) is higher according to the output of comparator IC1.

  The power receiving circuit 300 according to an embodiment of the present disclosure operates as described above, and can select and connect the higher voltage (absolute voltage value) of the other terminal viewed from the neutral point. it can. Since the power receiving circuit 300 according to an embodiment of the present disclosure selects and connects the higher voltage (absolute voltage value) of the other terminal viewed from the neutral point, the voltage balance on the DC power transmission side is selected. Can be automatically adjusted on the power receiving side.

  In addition, the power receiving circuit 300 according to an embodiment of the present disclosure includes a capacitor C on the input side of the comparator IC1 when selecting a higher voltage (absolute voltage value) of the other terminal viewed from the neutral point. The voltage change on the input side of the comparator IC1 is made slow. Since the voltage change on the input side of the comparator IC1 becomes slow, the power receiving circuit 300 according to an embodiment of the present disclosure suppresses the occurrence of instantaneous fluctuations in the input of the comparator IC1.

  In the power receiving circuit 300 according to the embodiment of the present disclosure, the output change of the comparator IC1 does not frequently change because the voltage change on the input side of the comparator IC1 becomes slow, and the switching operation by the relay RY1 is frequently performed. Can be prevented and the switching operation can be stabilized.

  The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

  Further, the effects described in the present specification are merely illustrative or exemplary and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
Delay is caused in the change of the first potential difference, which is the potential difference between the positive side output of the DC power and the neutral point, and the second potential difference, which is the potential difference between the neutral point and the negative side output of the DC power. A delay circuit,
A comparison circuit provided at a subsequent stage of the delay circuit, having a predetermined hysteresis, and comparing the magnitudes of the first potential difference and the second potential difference;
If the difference between the first potential difference and the second potential difference is greater than or equal to a predetermined amount as a result of the comparison by the comparison circuit, DC power is received from the larger one of the first potential difference or the second potential difference. A switching circuit for switching,
A DC power receiving device comprising:
(2)
The switching circuit receives power from a larger one of the first potential difference or the second potential difference when a difference between the first potential difference and the second potential difference continues for a predetermined time and exceeds the predetermined amount. The direct-current power receiving device according to (1), wherein the positive-side output and the negative-side output are switched.
(3)
The delay circuit is
A resistor that divides a potential difference between the positive output and the negative output;
A capacitive element provided in a preceding stage of the comparison circuit;
The DC power receiving device according to (1) or (2), including:
(4)
The comparison circuit according to (3), wherein an intermediate voltage obtained by dividing a voltage supplied by the positive electrode line and the negative electrode line by half with the resistor is compared with a voltage of the neutral line. DC power receiving device.
(5)
The DC power receiving device according to any one of (1) to (4), wherein the comparison circuit includes a comparator.
(6)
The DC power receiving device according to any one of (1) to (5), wherein the switching circuit switches so that DC power is received by any one of the positive output and ground or the negative output and ground.
(7)
The DC power receiving device according to (6), wherein the switching circuit includes a relay.
(8)
The power circuit according to any one of (1) to (7), further including a main circuit that operates by receiving DC power switched to the larger one of the first potential difference and the second potential difference by the switching circuit. DC power receiving device.

1: DC power transmission / reception system 10: DC bus line 20: Power feeding connector 30: DC plugs 100a to 100c: DC power feeding devices 200, 200a to 200e: DC power receiving device 300: Power receiving circuit 310: DC main circuit IC1: Comparator C: Capacitors R1, R2: Resistors RY1, RY1-2, RY1-3: Relay

Claims (8)

Delay is caused in the change of the first potential difference, which is the potential difference between the positive side output of the DC power and the neutral point, and the second potential difference, which is the potential difference between the neutral point and the negative side output of the DC power. A delay circuit,
A comparison circuit provided at a subsequent stage of the delay circuit, having a predetermined hysteresis, and comparing the magnitudes of the first potential difference and the second potential difference;
If the difference between the first potential difference and the second potential difference is greater than or equal to a predetermined amount as a result of the comparison by the comparison circuit, DC power is received from the larger one of the first potential difference or the second potential difference. A switching circuit for switching,
A DC power receiving device comprising:   The switching circuit receives power from a larger one of the first potential difference or the second potential difference when a difference between the first potential difference and the second potential difference continues for a predetermined time and exceeds the predetermined amount. The DC power receiving device according to claim 1, wherein the positive side output and the negative side output are switched so as to perform. The delay circuit is
A resistor that divides a potential difference between the positive output and the negative output;
A capacitive element provided in a preceding stage of the comparison circuit;
The DC power receiving device according to claim 1, comprising:   4. The comparison circuit according to claim 3, wherein the comparison circuit compares an intermediate voltage obtained by dividing the voltage supplied by the positive electrode line and the negative electrode line by half with the resistance, and the voltage of the neutral line. 5. DC power receiving device.   The DC power receiving apparatus according to claim 1, wherein the comparison circuit includes a comparator.   The DC power receiving apparatus according to claim 1, wherein the switching circuit performs switching so that DC power is received by any one of the positive output and ground or the negative output and ground.   The DC power receiving device according to claim 6, wherein the switching circuit is configured by a relay. 2. The DC power receiving apparatus according to claim 1, further comprising a main circuit that operates by receiving DC power switched to the larger one of the first potential difference and the second potential difference by the switching circuit.

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