JPH0944260A - Feeding polarity switching circuit for constant current feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a high voltage part and to simplify the switching of polarity by arranging a current detector on the high voltage output side of polarity changeover switch and providing a detected voltage polarity switcher to be operated by a polarity switching operating part. SOLUTION: Concerning the submarine repeater of submarine cable, a constant current is fed from a power transforming part 11, the voltage in proportion to the constant current and an output current is detected, and the output current is made into a constant current while being limited by the voltage provided in comparison with a reference voltage, then, the polarity of feeding current is switched corresponding to a signal from a polarity switching operating part 15 as required. At such a time, a current detector 22 is arranged on the high voltage output side of a polarity changeover switch 21 for switching the polarity of output current from the power transforming part 11, and a detected voltage polarity switcher 12 is provided for switching the polarity of voltage detected by the current detector 22 corresponding to the signal from the polarity switching operating part 15. Thus, the wiring length of the power transforming part 11 and the polarity changeover switch 21 can be shortened and the polarity of output voltage from the current detector 22 can be held equal with the polarity before the operation of the changeover switch 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power output polarity switching circuit for investigating a fault location of a submarine cable or the like of a power feeder for supplying a constant current power to a submarine repeater used for a submarine cable.

For submarine repeaters used for submarine cables,
A constant current power supply device that supplies constant current power has a function of switching the polarity of a power supply output. This is a function required to measure the current-voltage characteristics and search the cable laying position and locate the fault point when a cable fault occurs. The output voltage of the device is as high as about 5,000 to 10,000 volts, and the device is large due to the measures for insulation, and the manufacturing cost is increased.

Therefore, there is a strong demand for a power supply device having the same function, which can be miniaturized and which is low in cost.

[0004]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 9 is a first conventional example and shows an example of a circuit having the polarity switching function of the first conventional technique. In the figure, the portion of the connection line indicated by a thick line is a portion that needs to be treated as a high-voltage circuit and requires insulation.

In the circuit used for actual operation, for example, three output monitoring units 1 are assembled in parallel and used. However, in order to simplify the description, it is assumed that one device is used. The operation in the normal operating state is performed by the power conversion unit 11
Then, the input DC power supply is converted into AC, a high-voltage AC power supply is taken out, and rectified to obtain high-voltage DC. , The next filter 23 ₁ removes the AC component. Then, the following, for example, by the current detector 22 ₁ constituting a transformer, passing a high-voltage current to the primary side of the transformer, detects a voltage proportional to the high voltage current in the primary side transformer secondary.

The detected voltage is input to a current control error amplifier 13 composed of, for example, a differential amplifier, and compared with a predetermined reference voltage Vref ₁ , the high voltage DC detected by the current detector 22 ₁ is detected. If it decreases, the detection signal is fed back to the power conversion unit 11, and the power conversion unit 11 controls so that the high-voltage output DC increases.

A current detector 22 ₂ is connected to the other terminal of the filter 23 ₁ , and like the current detector 22 ₁ , a voltage corresponding to the detected load current is detected to monitor the load current. For example, when the detected voltage exceeds a certain range, an alarm is issued.

The output sides of the current detectors 22 and 27 are connected to the polarity changeover switch 21, which is shown in FIG.
It is switched to the solid line side as shown in. That is, the current detector 22 ₁ side is +, and the current detector 22 ₂ side is −.

A resistor 24 ₁ for extracting a voltage and a rectifier 28 ₁ are connected between the outputs of the polarity changeover switch 21, and the rectifier 28 ₁ detects a + voltage proportional to the output voltage of the power converter 11. To do.

The detected voltage is converted into a predetermined voltage value by the voltage detector 26 ₁ and input to the voltage control error amplifier 14 which is composed of, for example, a differential amplifier. In the voltage control error amplifier 14, if the high voltage detected by the voltage detector 26 ₁ decreases in comparison with the predetermined reference voltage Vref ₂ , the detection signal is fed back to the power conversion unit 11 and the power is converted. The converter 11 controls so that the high voltage output voltage increases.

Further, the voltage detected by the voltage detector 26 ₂ is used for voltage monitoring, and an alarm is issued when the detected voltage exceeds a certain range, for example. Further, the output of the polarity changeover switch 21 is connected to the filter 23 _2, high DC supplied to the load 30 is removed noise component and AC component is again supplied to the plurality of loads 30.

Here, for example, when an accident such as disconnection occurs in a submarine cable or the like, power supply is stopped, and in order to identify the accident occurrence place, the power supply unit 11 supplies a power supply voltage, for example, 5000 V for 10 minutes. A voltage reduced to about 1, for example, about 500 V is generated, and the reference voltage Vref _{1 of} the current control error amplifier 13 and the voltage control error amplifier 14 is
Vref ₂ , for example, 5V is also supplied at a predetermined voltage of about 1/10 of the reference voltage during operation, for example, 0.5V.

Then, the polarity of the polarity selector switch 21 is switched under the control of the polarity switching operation section 15, the current and voltage in each case are measured, and the failure location is specified from each measured value.

FIG. 10 shows an example of a circuit having a polarity switching function of the second conventional technique. The case of the second conventional technique is an example in which the high pressure portion in the first conventional example is further reduced. It is unavoidable that the voltage from the + output terminal of the power converter 11 to the load 30 is high, but between the − output terminal of the power converter 11 and the load 30,
In order to reduce the high voltage part as much as possible, the power converter 1
Current detector 22 connected to the negative output terminal side of 1
₂ is moved to the + output terminal side of the power conversion unit 11, and the polarity changeover switch 21 is moved immediately after the filter 23 ₁ .

As a result, the polarity changeover switch 21₁Switch
The current detector 22₁, 22 ₂Reverses the polarity of
In order to correct the₂Added
As a result, the power supply polarity is switched off in the same direction at two locations simultaneously.
It was necessary to change it, and switching was complicated.

In both the first and second conventional examples, the power converter 11
The output current droop control and alarm detection circuit that detects the output voltage of is required to have a rectifier circuit that makes the detection voltage a fixed direction regardless of the polarity of the power supply output, and further improves the circuit complexity and reliability. It had a bad influence on cost reduction.

[0017]

As described above, in the prior art, since the output voltage of the power feeding device for feeding the submarine repeater is high, there are many portions to be insulated, the device becomes large, and the cost is reduced. There was a problem of getting high.

Further, as in the second conventional example, there is a problem that the power supply polarity switching circuit becomes complicated although the high voltage portion is somewhat reduced. Further, in order to take out a voltage proportional to the output voltage, a resistor and a rectifier are used in the prior art, so that there is a problem that a leakage current of a diode forming the rectifier causes an adverse effect.

An object of the present invention is to solve the above problems, and to provide a power supply polarity switching circuit for a constant current power supply device in which the high voltage portion is reduced and the circuit power supply polarity is easily switched.

[0020]

In order to solve the above-mentioned problems, a submarine repeater of a submarine cable transmission system is fed with a constant current output from a power converter, and a voltage proportional to the constant current and an output voltage. And a voltage proportional to
In the power supply polarity switching circuit of the constant current power supply device that controls the output current to a constant current by controlling the voltage obtained by comparison with the reference voltage, and switches the polarity of the power supply current by the polarity switching instruction signal from the polarity switching operation unit when necessary. , A current detector for extracting a voltage proportional to the output current is arranged on the high-voltage output side of the polarity changeover switch for changing the polarity of the output current of the power conversion unit, and the polarity changeover instruction signal from the polarity changeover operation unit
The object can be achieved by adopting a configuration including a detection voltage polarity switching device that switches the polarity of the detection voltage of the current detector.

Further, a voltage dividing resistor for dividing the output voltage to obtain a voltage proportional to the output voltage of the power converter is provided between the output terminals of the polarity changeover switch, and a voltage detector is provided at a branch point of the resistor. Connecting.

The object can be achieved by connecting the output of the voltage detector to the detection voltage polarity switching device. Further, another current detector for performing current alarm detection may be arranged on the high-voltage output side of the power conversion unit, or the current detector for performing current alarm detection may be used for the low voltage of the power conversion unit. It may be arranged on the output side.

Further, the polarity changeover switch is provided with a changeover signal holding circuit for holding the polarity changeover signal from the polarity changeover operation section. The object can be achieved by sending the polarity switching signal held by the switching signal holding circuit to the detection voltage polarity switching device and operating the polarity switching switch itself.

Further, a switching signal transmission inhibiting circuit for inhibiting the transmission of the switching signal when the normal output polarity is provided may be provided between the polarity switching operation section and the polarity switching switch. Further, the detection voltage polarity switcher may be a photo MOS relay that is inoperative when the output polarity is normal and operable when the output polarity is inverted, or may be inoperative when the output polarity is inverted and operable when the output polarity is inverted. A relay may be used.

[0025]

[Function] Since the current detector for extracting the voltage proportional to the output current is arranged on the high voltage output side of the polarity changeover switch for changing the polarity of the output current of the power conversion unit, the high voltage output side of the polarity changeover switch becomes long, The wiring length of the output terminal of the power conversion unit and the polarity changeover switch can be shortened. In addition, since the detection voltage polarity changer is provided, the polarity of the output voltage of the current detector that is reversed when the polarity changeover switch is operated can be changed by changing the arrangement of the current detector on the high voltage output side of the polarity changeover switch. By the control from the switching operation unit, the polarity can be maintained at the same polarity as before the switch was operated.

Further, since the voltage dividing resistor is provided between the output terminals of the polarity changeover switch and the voltage detector is connected to the branch point of the resistor, the voltage proportional to the output voltage of the power converter is converted into the resistor. It can be taken out by a circuit that is simple by combining and does not generate a leakage current due to a diode as in the conventional example.

Further, since the output of the voltage detector is connected to the detection voltage polarity switching device, the polarity of the output of the current detector and the polarity of the output of the voltage detector can be switched simultaneously by the control from the polarity switching operation section. You can

Further, by disposing another current detector for detecting the current alarm on the high voltage output side of the power converter, the same current detector as the current detector for detecting the output current can be used. .

Alternatively, by disposing a current detector for detecting a current alarm on the low-voltage output side of the power converter, it is possible to prevent an increase in the length of the wiring for high-voltage countermeasure processing. Also,
The polarity changeover switch is equipped with a changeover signal holding circuit that holds the polarity changeover signal from the polarity changeover operation section, and the polarity changeover signal held by the changeover signal hold circuit is sent to the detection voltage polarity changeover device and the polarity changeover is performed. Since the switch itself is configured to operate, the polarity switching signal from the polarity switching operation unit erroneously disconnects the polarity switching signal from the polarity switching operation unit while the detection voltage polarity switching unit and the polarity switching switch are operating. Even then, the switching operation can be continued.

Further, by providing a switching signal transmission prohibiting circuit between the polarity switching operation section and the polarity switching switch, even if the polarity switching signal is erroneously transmitted from the polarity switching operation section during normal output polarity, switching is performed. It is possible to inhibit the polarity switching signal from being transmitted from the signal transmission inhibiting circuit to the polarity switching switch.

Further, as the detection voltage polarity switching device, a photoMOS relay or a general relay is used so as to be inoperative when the output polarity is normal and operable when the output polarity is inverted, so that the detection voltage polarity which is rarely used is used. It is possible to prevent unnecessary deterioration of the photo MOS relay or the general relay in the operating state of the switch.

[0032]

EXAMPLES Examples will be described with reference to FIGS. 2 is an embodiment of the first invention, FIG. 3 is an embodiment of the second invention, FIG. 3 is an embodiment of the third invention, and FIG. 5 is an embodiment of the fourth invention. 6 is an example of a polarity switching circuit, FIG. 7 is an example of the polarity switching circuit using a photo MOS relay, and FIG. 8 is a diagram showing an example of the polarity switching circuit using a relay contact.

In the figure, the same reference numerals as those in FIGS. 9 and 10 indicate the same things, 12 is a detection voltage polarity switching device, 15 is a polarity switching operation unit, 18 is a switching signal transmission inhibiting circuit, 25, R1 to R4.
Is a resistance, AMP is an operational amplifier, PC is a photocoupler, P
ML is a photo MOS relay, TR1 and 2 are MOSFETs
Transistor, RL is relay, RL ₁ is relay body, R
L ₂ is a relay contact.

First, an embodiment of the first invention will be described with reference to FIG. First, in a normal power supply state, the input low-voltage DC power supply is boosted to a high-voltage DC power supply by the power conversion unit 11 and output from the output terminal. Then, the output current has its AC component removed by the filter 23 ₁ , passes through the polarity switch 21, and is sent to the current detector 22 ₁ for constant current control and the current detector 22 ₂ for current alarm. Two
A low voltage proportional to the output current value is taken out by each of the current detectors 22 ₁ and 22 ₂ , one of which is sent to the detection voltage polarity switching device 12 ₁ and the other of which is sent to the detection voltage polarity switching device 12 ₂ .

The output current that has passed through the _two current detectors 22 ₁ and 22 ₂ has its AC component further removed by the filter 23 ₂ and is supplied to the load 30. In addition, a part of the output current that has passed through the _two current detectors 22 ₁ and 22 ₂ is shunted and a voltage detection circuit configured by resistors 24 ₁ and 25 ₁ and a resistor 2
After passing through 4 ₂ and the voltage detection circuit composed of the resistor 25 ₂ , the voltage is returned to the power conversion unit 11. Each voltage detection circuit extracts the voltage corresponding to the voltage output by the power conversion unit 11 and detects the voltage. is sent to vessel 26 _1, 26 _2, further one is sent to the detection voltage polarity switch 12 ₁ via a voltage detector 26 _1, and the other to detect voltage polarity switch 12 ₂ via a voltage detector 26 ₂ Sent.

The voltage from the current detector 22 ₁ and the voltage from the voltage detector 26 ₁ sent to the detected voltage polarity switcher 12 ₁ are respectively the current control error amplifier 13 and the voltage control error amplifier 14. To the reference voltages Vref ₁ and Vref ₂
The difference compared with is extracted and sent to the power conversion unit 11 for use as a control signal for keeping the output of the power conversion unit 11 constant.

The voltage from the current detector 22 ₂ and the voltage from the voltage detector 26 ₂ sent to the detected voltage polarity switcher 12 ₂ are sent to the current monitoring circuit 17 and the voltage monitoring circuit 16, respectively. It is used to monitor the output current and output voltage of the power converter.

When an accident such as a submarine cable occurs, the power conversion unit 1 is used to investigate the location of the failure.
The current and voltage output at 1 are reduced to about one-tenth of that during operation and supplied. Similarly, the reference voltages Vref ₁ and Vref of the current control error amplifier 13 and the voltage control error amplifier 14 are set.
_{2 is} also supplied with a predetermined voltage that is about 1/10 of the reference voltage during operation.

Then, the polarity of the polarity changeover switch 21 is changed under the control of the polarity changeover operation section 15, the current and voltage in each case are measured, and the failure point is specified from each measured value.

As shown in FIG. 6, the polarity changeover of the polarity changeover switch 21 is performed by the current detector 22 or the voltage detector 2.
The voltage from 6 is input to Vin ₂ , and the polarity switching operation unit 15
The switch element SW is driven by the polarity switching signal from to switch the switch contact to invert the output of the error amplifier AMP.

When the switch is off, a voltage having the same polarity as the voltage applied to Vin is the output V of the operational amplifier AMP.
Output to out. And when the switch is on,
The inverted voltage is output to the output Vout of the operational amplifier AMP.

In this circuit, when the detected voltage polarity from the current detector at the time of normal power supply output polarity is + Vin,
At this time, since the switch is off, the operation amplifier AM
The output voltage Vout of P, that is, the input voltage of the error amplifiers 13 and 14 is Vout =-(R2 / R1) * (+ Vin) + (1 + R2 / R1) * (+ Vin) = + Vin.

When the polarity of the power supply output is reversed, the switch is turned on. At this time, the flow direction of the output current is also reversed, so that the detection current and the detection voltage have the same polarity of −Vin.
Becomes Since the operational amplifier AMP operates as an inverting amplifier, its output voltage is Vout =-(R2 / R1) * (-Vin) = (R2 / R1) * (Vin).

If the constant is set so that R2 = R1, it becomes possible to send the detection voltage of the same polarity and the same voltage value to the error amplifiers 13 and 14 even if the power feeding polarity is switched, and the power feeding is performed. Even if the output polarity is switched, a feedback control system is configured and stable constant current control can be performed.

When the polarity of the polarity changeover switch 21 is reversed under the control of the polarity changeover operation section 15, the current detectors 22 ₁ and 22 _1
2 and the polarity of the low voltage proportional to the output current of the power converter 11 extracted from the voltage detectors 26 ₁ and 26 ₂ are also inverted, so that the polarity is inverted by the detection voltage polarity switchers 12 ₁ and 12 ₂ , respectively. It is necessary to put it back. Therefore, it is necessary to switch the polarity switch 21 and the detection voltage polarity switcher 12 simultaneously.

An example in which the detection voltage polarity switching device 12 is realized is, as a first method, the photo MOS shown in FIG.
There is a method using a relay and a method using a relay contact shown in FIG. 8 as a second method.

In the photo MOS relay PML of FIG. 7, when a polarity switching signal flows through the photo coupler PC, a current flows through the photoelectric element due to the output light of the light emitting diode of the photo coupler PC, and the MOSFET transistors TR1 and TR2.
Turns on, and the + side input of the arithmetic amplifier AMP becomes ground.

In the case of the relay contact shown in FIG. 8, the relay body R
When the polarity switching signal flows to L1, the relay contact RL2 operates and closes, so that the + side input of the operational amplifier AMP is grounded.

In any case, the relay RL is kept in the off state in the normal operation state and is used in the on state when the switching is required, thereby preventing the unnecessary deterioration of the life of the relay RL.

In the first embodiment, what requires high-voltage insulation treatment is the wiring in which the parts are shown by thick lines in FIG. 2 and the parts connected by the wiring, and
It is the same in the prior art that high-voltage insulation treatment is required for all from the side output terminal to the load, but the negative side of the power conversion unit 11 is only as much as the period up to the polarity changeover switch 21 is shortened. Fewer high voltage insulation procedures.

Further, in the conventional example, the voltage dividing circuit constituted by the resistors 24 ₁ and 25 ₁ and the voltage dividing circuit constituted by the resistors 24 ₂ and 25 ₂ are the polarity changeover switch 2
A rectifier was used in order to prevent the direction of the output voltage from changing even if 1 is operated to reverse the direction of the output current. However, because the detection voltage polarity switcher 12 is used to reverse the direction. The failure rate can be reduced as much as the fixed direction of the polarity of the detected voltage by rectification is no longer necessary.

Next, a second embodiment will be described with reference to FIG. The second embodiment differs from the first embodiment in that the current detector 22 ₂ is moved to the opposite output side of the polarity changeover switch 21.

Since the opposite output side of the polarity changeover switch 21 has a low voltage, there is no need for high-voltage insulation treatment, and the high-voltage insulation treatment is correspondingly less than in the first embodiment. Next, a third embodiment will be described with reference to FIG.

In the third embodiment, the polarity changeover switch 21 of the first embodiment is provided with a polarity changeover signal holding function for holding an input polarity changeover signal, and the polarity changeover switch 21 sends out the polarity changeover signal holding function. When the polarity switching signal is sent, the polarity switching switch 21 itself operates to switch the switch.

When the polarity switching signal output from the polarity switching operation section 15 is once received by the polarity switching signal holding function of the polarity switching switch 21 and the polarity switching signal input by the polarity switching signal holding function is held, the polarity switching signal is held. The holding function allows the polarity switching signal to be detected by two detection voltage polarity switching devices 12 ₁ and 12 _2.
Send to

After that, the polarity changeover switch 21 and the two detection voltage polarity changers 12 ₁ and 12 ₂ simultaneously perform a switch operation to invert the polarity of the voltage / current to be output. Since the polarity changeover switch 21 is a heavy unit because it is necessary to take measures against high voltage insulation, the polarity changeover operation unit 15 is a relatively light unit, so that a failure occurs in the submarine cable. Then, in order to identify the faulty part of the cable, the polarity changeover switch 21 is operated and in use,
If the polarity switching operation unit 15 is accidentally pulled out from the main body of the apparatus, the operation of the polarity switching switch 21 is canceled, which causes a trouble.

Therefore, even if the polarity switching operation section 15 is pulled out from the apparatus main body, the polarity switching switch 21 holds the polarity switching information, so that the operation of the polarity switching switch can be stabilized.

It should be noted that the output voltage detection circuit provided after the current detection unit 22 ₂ may be the same circuit as in the first and second embodiments, of course, but as in the conventional example, the rectifier 28 is used. Can also be used. In this case, the voltage extracted from the output voltage detection circuit is the polarity changeover switch 21.
Since it is always in a fixed direction regardless of the above operation, it is not necessary to use the detection voltage polarity switching device 12.

Next, a fourth embodiment will be described with reference to FIG. The fourth embodiment differs from the third embodiment in that the polarity switching signal output from the polarity switching operation section 15 is once sent to the polarity changeover switch 21 via the switching signal sending-out prohibiting circuit 18. It is a thing.

Here, the switching signal transmission prohibiting circuit 18 is a circuit for prohibiting the transmission of the polarity switching instructing signal even when the polarity switching instructing signal from the polarity switching operation section 15 is accepted at the normal output polarity. .

With such a configuration, when the polarity switching operation section 15 is mistakenly operated during normal output polarity, the polarity switching switch 21 operates and the polarity of the current / voltage supplied to the load is reversed. It may cause troubles such as load failure.

Therefore, even if the polarity switching operation section 15 is erroneously operated, the switching signal transmission prohibiting circuit 18 prohibits the transmission of the switching signal, so that the polarity switching switch 21 malfunctions at the normal output polarity. Can be prevented.

[0063]

As described above, according to the present invention,
The functions and characteristics are the same as those of conventional equipment,
Since the high pressure portion can be reduced, the device can be downsized and the cost can be reduced.

Further, in order to extract a voltage proportional to the output voltage, a resistor and a rectifier were used in the prior art, but since the voltage is simply divided by the combination of resistors, the adverse effect of the leakage current of the diode forming the rectifier is adversely affected. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention.

FIG. 2 is an embodiment of the first invention.

FIG. 3 is an embodiment of the second invention.

FIG. 4 is an embodiment of the third invention.

FIG. 5: Embodiment of the fourth invention

FIG. 6 is a polarity switching circuit example of a detection voltage polarity switching circuit.

7 is an example of a polarity switching circuit using a photo MOS relay in FIG.

FIG. 8 is an example of a polarity switching circuit using relay contacts in FIG.

FIG. 9 is a first conventional example.

FIG. 10 shows a second conventional example.

[Explanation of symbols]

 11 Output Monitor 12 Detection Voltage Polarity Switch 13 Current Control Error Magnifier 14 Voltage Control Error Magnifier 15 Polarity Switching Operation Section 16 Voltage Monitoring Circuit 17 Current Monitoring Circuit 18 Switching Signal Sending Inhibit Circuit 20 Output Monitoring Section 21 Polarity Switching Switch 22,27 Current detector 23 Filter 24,25, R1-3 Resistance 26 Voltage detector 28 Rectifier 30 Load PC Photo coupler PML Photo MOS relay RL relay RL1 Relay body RL2 Relay contact TR1, MOSFET transistor

Claims (8)

[Claims] 1. A submarine repeater of a submarine cable transmission system is fed with a constant current output from a power conversion unit, and a voltage proportional to the constant current and a voltage proportional to the output voltage are detected to obtain a reference voltage. In the power supply polarity switching circuit of the constant current power supply device, which controls the output current to a constant current by controlling the voltage obtained by comparison, and switches the polarity of the power supply current by the polarity switching instruction signal from the polarity switching operation unit when necessary. A current detector for extracting a voltage proportional to the output current is arranged on the high-voltage output side of the polarity selector switch for switching the polarity of the output current of the converter, and the polarity of the detected voltage is switched by the control from the polarity switching operation unit. A power supply polarity switching circuit for a constant current power supply device, which is configured to have a detection voltage polarity switching device. 2. The voltage dividing resistor according to claim 1, wherein the voltage dividing resistor is provided between the output terminals of the polarity changeover switch to obtain a voltage proportional to the output voltage of the power conversion unit, and the branch point of the resistor is provided. A voltage supply polarity switching circuit for a constant current power supply device, characterized in that a voltage detector is connected to, and the output of the voltage detector is connected to the detection voltage polarity switching device. 3. The power supply polarity switching circuit for a constant current power supply device according to claim 1, wherein another current detector for detecting a current alarm is arranged on the high-voltage output side of the power conversion unit. 4. The power supply polarity switching circuit for a constant current power supply device according to claim 2, wherein the current detector for detecting a current alarm is arranged on the low-voltage output side of the power conversion unit. 5. The polarity switching switch according to claim 1, further comprising a switching signal holding circuit that holds the polarity switching signal from the polarity switching operation unit, and the switching signal holding circuit holds the switching signal holding circuit. A power supply polarity switching circuit for a constant current power supply device, wherein the polarity switching signal is sent to the detection voltage polarity switching device and the polarity switching switch is operated. 6. The constant current according to claim 5, wherein a switching signal transmission prohibiting circuit that prohibits transmission of a switching signal when the output polarity is normal is provided between the polarity switching operation section and the polarity switching switch. Power supply polarity switching circuit for power supply equipment. 7. The detection voltage polarity switching device according to any one of claims 1 to 6, wherein the detection voltage polarity switching device is inoperative at a normal output polarity,
A power supply polarity switching circuit for a constant current power supply device, which uses a photoMOS relay capable of operating when the output polarity is reversed. 8. The detection voltage polarity switching device according to any one of claims 1 to 6, wherein the detection voltage polarity switching device is inoperative at a normal output polarity,
A power supply polarity switching circuit for a constant current power supply device, which uses a relay capable of operating when the output polarity is reversed.