KR100930983B1 - Power Line Discrimination Device with Ground Potential - Google Patents

Abstract

An apparatus for discriminating a power line having a ground potential from a pair of power lines for supplying an AC voltage of a single phase two-wire type is provided. The power line judging device having the ground potential includes: an operation power supply unit for converting a single-phase two-wire AC voltage into a DC voltage to charge the capacitor and discharging the voltage charged in the capacitor in response to the blocking of the AC voltage; A ground potential discrimination section setting unit connected between the pair of power lines and the operation power supply unit to supply or block the single-phase two-wire AC voltage to the operation power supply unit; An AC signal amplifier which is operated by a DC voltage output from the operation power supply unit and amplifies an AC signal loaded on any one of the pair of power lines in response to the AC voltage blocking of the ground potential discrimination section setting unit; The power line connected to an input terminal of the AC signal amplifier is grounded by comparing the voltage output from the AC signal amplifier with a reference voltage preset by the DC voltage. And a ground potential discrimination unit for discriminating whether or not it is a potential side line.

Electromagnetic waves, field waves, neutral lines, hot lines, shielded networks,

Description

Power line discrimination device having a ground potential {DEVICE FOR DISTINGUISHING OF POWER LINE HAVING EARTH POTENTIAL}

1A and 1B are equivalent circuits and voltage waveform diagrams for explaining a single-phase two-wire AC voltage supplied to domestic homes.

2 is a circuit diagram of an electrical product having a power line discriminating device having a ground potential according to a preferred embodiment of the present invention.

`` Explanation of symbols for main parts of drawings ''

100: ground potential power selection device, 110: power switch,

120: ground potential discrimination section setting unit, 130: operating power supply unit,

140: AC signal amplifier, 150: ground potential determination unit

200: electric mat part, 300: temperature control part.

The present invention relates to a power line detection device having a ground potential, and more particularly, to an apparatus for determining a power line having a ground potential in a pair of power lines for inputting a single-phase two-wire system AC voltage. It is about.

All electrical and electronic products (hereinafter referred to as "electrical appliances") operated by inputting alternating current volts are coupled to and supplied from a receptacle or power socket, an indoor electrical connection. It is provided with a power line code (power line code) for supplying to the internal circuit of the electrical appliance.

Generally, the receptacle or power socket is called an outlet, and the power line cord is composed of a plug inserted into the outlet and at least two power lines connected to the plug.

As described above, an electrical product that inputs an AC voltage through a power line cord is known to inevitably generate electromagnetic waves due to the current flowing through the power line and the operation of an internal circuit. Electromagnetic waves are divided into pulsed electric fields and magnetic-field waves, which are difficult to completely block with current technology, but they are shielding nets made of conductors inside electrical and electronic products. This technology is applied to most electrical and electronic products because it can be blocked by wrapping it and grounding the screening network.

At present, the power line cord provided in the electrical products produced in Korea is a groundless two-hole method having a pair of power lines and a plug without a ground wire, and a grounded three-hole method with a pair of power lines and a collecting line. have.

According to the Electrical Appliances and Safety Control Act, products whose body is made of metal, for example, electric washing machines, refrigerators, and irons, must have a pair of power lines and ground wires in order to protect life and property from the risk of electric shock and electric fire in the event of a short circuit. It is regulated to use grounded three-prong power line cord having a non-conductor, and when the body of electrical appliance is non-conductor such as plastic, the risk of electric shock or short-circuit is relatively small, so that the grounding two-prong power line cord can be used. Doing.

Examples of products using a non-grounded two-prong power line cord include nonconductive bodies such as hair dryers, radios, electric mats, electric blankets (or electric blankets), and electric mats. In the case of electric products using two-wire grounding type power line cords, the outside of the product is made of non-conductive material such as synthetic resin, fabric, leather, or artificial leather, so there is no risk of short circuit or electric shock. By using the human body in close contact with the human body, the electric wave generated by the heating element located inside the mat is directly affected.

It is reported that such electric waves can affect various diseases such as headache, vision loss, leukemia, brain tumor, brain wave accumulation in the human body, circulatory abnormalities, reproductive function destruction in men and induction of eye diseases.

Many technologies have been researched and developed to block electric waves that adversely affect the human body even when using a non-grounded two-prong power line cord. For example, a method of blocking electric waves using a neutral line of a single-phase two-wire power line cord composed of a hot line and a neutral line, that is, a ground power supply line, is used.

Referring to Figures 1a and 1b will be briefly described the principle of blocking the electric wave in the electrical appliances using a single-phase two-wire 220VAC (volts alternating current). Figure 1a is an equivalent circuit of a single-phase two-wire 220VAC supplied to the home of Korea, Figure 1b is a waveform diagram showing the flow of the current.

When an electric load is connected to both ends of the hot line HL and the neutral line NL of FIG. 1A to form a closed circuit, an AC current flows from D1 to D2 for 1/2 cycle. During the next 1/2 cycle, it flows in the direction of D2 to D1. At this time, the closed circuit connected to the live wire HL and the neutral wire NL is operated by 220VAC supplied for 1/2 cycle, and the potential of the neutral wire NL is actually maintained at OV (ground potential).

Therefore, if the voltage of the single-phase two-wire 220VAC can detect the ground potential side line, that is, the neutral line (NL) accurately, it can be easily removed by using this. For example, the internal circuit of the electric product is wrapped in a shielding net, and the shielding net is grounded to the ground potential side line to ground the electric wave generated from the inner circuit and cut off.

Neon lamps have been widely used as a common method for detecting ground potentials in single-phase two-wire 220VAC. Since the human body has earth ground potential, the high resistance is connected to one side of the neon lamp to make a touch terminal, and the other side of the neon lamp is in contact with the two strands of power lines, respectively. The power line on which the lamp is lit is detected as live, and the power line at which the neon lamp is not lit is detected as the ground potential side line (neutral line).

However, the ground potential side detection method has a risk of electric shock by the user directly contacting the contact terminal provided on one side of the neon lamp. For example, when a single-phase two-wire live wire is contacted with wet hands, the closed circuit is formed from live wire through neon lamp, high resistance, and human body, and the risk of electric shock cannot be completely avoided. There was a problem of violating the standard of the withstand voltage insulation test under the Electrical Appliances Safety Standard Act.

Conventional technology for detecting the ground potential side line from an outlet or a plug of a power line cord into which an AC voltage of a single-phase two-wire system is input is disclosed. It may be a representative example.

The ground wire detection technology disclosed in the registered patent includes two neon lamps of which one side is grounded, two fixed terms connected between the other side of the neon lamps and a single-phase two-wire type power line, and two detecting the lighting of the neon lamp. Photoconductive cells and a controller for outputting a switching control signal corresponding to the output of the photoconductive elements.

The ground line detection technology of the registered patent configured as described above cannot detect the ground potential side line in a state completely insulated from an AC voltage input by a single-phase two-wire type by using a neon lamp and a photoconductive element. In addition, the circuit configuration is complicated by configuring a microprocessor or a plurality of logic controllers that selectively drive switches connected to single-phase two-wire power lines in response to the outputs of two photoconductive elements.

Accordingly, an object of the present invention is to provide a power line discrimination apparatus having a ground potential for detecting the ground potential side line of a single-phase two-wire power line by a power output in an insulated state from the single-phase two-wire AC voltage.

Another object of the present invention is to charge a predetermined voltage by the input of the AC voltage supplied through the power line of the live and neutral wires connected in a single-phase two-wire type, and is input to any one of the single-phase two wires in a state insulated from the power line The present invention provides a device for determining whether a power line has a ground potential by the presence or absence of a voltage.

It is still another object of the present invention to provide a power line discrimination apparatus having a ground potential for easily discriminating and detecting which one of the single-phase two-wire systems is a neutral line by a very simple configuration.

The present invention for achieving the above object is a pair of power line for inputting a single-phase two-wire AC voltage; An operation power supply unit for converting a single-phase two-wire AC voltage into a DC voltage to charge the capacitor and discharging the voltage charged in the capacitor in response to the blocking of the AC voltage; A ground potential discrimination section setting unit connected between the pair of power lines and the operation power supply unit to supply or block the single-phase two-wire AC voltage to the operation power supply unit; An AC signal amplifier which is operated by a DC voltage output from the operation power supply unit and amplifies an AC signal loaded on any one of the pair of power lines in response to the AC voltage blocking of the ground potential discrimination section setting unit; The AC signal is operated by a DC voltage output from the operation power supply unit, and compares the reference voltage set by the DC voltage with the voltage output from the AC signal amplifier, when the output of the AC signal amplifier is lower than the reference voltage. Characterized in that the ground potential determination unit for discriminating the power line connected to the amplifier by the ground potential side line.

The ground potential determination section setting unit may be a pair of manual switches for supplying an AC voltage inputted through the pair of power lines to the operation power supply unit and cutting off the AC voltage supplied to the operation power supply unit by a user's selection.

The operation power supply unit is connected to both ends of a pair of power lines through the ground potential discrimination section setting unit, and outputs a rectified voltage for rectifying an input AC voltage to a predetermined constant voltage level and an AC voltage fixed by the constant voltage diode. And a rectifier circuit for charging the capacitive element connected to the node and discharging the charged voltage by blocking the AC voltage of the ground potential discrimination section setting unit to supply the operating voltages of the AC signal amplifier and the ground potential discriminator. It is done.

The AC signal amplifier is connected to any one of the pair of power lines, and the AC signal input unit inputs only an AC signal, and amplifies and outputs the AC signal output from the AC signal input unit by the voltage output from the rectifier circuit. It is characterized by consisting of an AC amplifier.

The ground potential discriminating unit divides the output of the rectifier circuit to set a reference voltage, a second rectifier rectifying the output of the AC signal amplifier, a voltage set from the set reference voltage and the second rectifier And a comparator for outputting a live voltage power line detection signal or a ground potential power line detection signal according to a comparison result, and an indicator connected to an output node and ground connected to the comparator, the indicator being lit in response to the live voltage power line detection signal. It is done.

Preferably, the pair of power lines and the front end are further connected to a power switch for connecting / blocking a single-phase two-wire AC voltage supplied from the outside.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings in which: FIG. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth. It should be noted that the embodiments of the present invention described below are merely for explaining the spirit of the present invention to those skilled in the art, and detailed descriptions of well-known functions and configurations in the art that may unnecessarily obscure the gist of the present invention are provided. Note that it is omitted.

2 is a circuit diagram of an electric product having a power line discriminating device having a ground potential according to an embodiment of the present invention, reference numeral 100 denotes a ground potential power line discriminating device, and reference numeral 200 denotes a heating element that generates heat by input of an AC voltage. (210), the electric mat unit consisting of a field thermistor 220 for sensing the heating temperature of the heating element 210 and the electric field shielding network 230 is connected to the power line (AC2) and wrapped in the heating element 220. . In addition, the reference numeral 300 is operated by an input of an operating power supply voltage VCC, and is supplied to the electric mat unit 200 from the pair of power lines AC1 and AC2 according to the output of the demister 220. Temperature control unit for controlling the amount of current.

2 and the detailed diagrams or circuit diagrams of the electric mat unit 200 and the temperature control unit 300 except for the ground potential power line discriminating apparatus 100 are obvious to those skilled in the art. Detailed description thereof is omitted.

2, reference numerals AC1 and AC2 denote a pair of power lines to which an AC voltage of a single-phase two-wire type is input. Therefore, when the power line AC1 is a hot line, another power line AC2 is a ground potential side line, that is, a neutral line, and when the power line AC1 is a neutral line, another power line AC2 is live. Becomes

Although not shown in FIG. 2, the pair of power lines AC1 and AC2 of FIG. 2 are coupled to a plug (not shown), and the plug is coupled to a power socket (also called a "outlet") to provide a pair of power. The AC voltage 220VAC of the single-phase two-wire system is input to the power lines AC1 and AC2.

When the switches SW1 and SW2 in the power switch 110 are “turned on” while the AC voltage 220VAC is input to the pair of power lines AC1 and AC2, the AC voltage 220VAC is set to the ground potential determination section 120. Are supplied to a pair of input terminals of the operation power supply unit 130 through a common terminal (Common: CO1, CO2) -normal cross terminal (Normal Close: NC1, NC2) of the switches SW2a and SW2b.

At this time, the resistor R1 in the operating power supply unit 130 is an inrush current limiting resistor, the capacitor C1 is for AC coupling, and between both terminals of the pair of input terminals connected to the pair of power lines AC1 and AC2. The zener diode ZD1 connected to the clamp clamps the voltage level of both terminals to a constant level (about 12V). The diode D1 in the operation power supply unit 130 rectifies the AC voltage of the power line AC1 fixed at a constant voltage level by the control diode AD1 to DC to output the first DC voltage VCC. At this time, the capacitor C2 connected to the cathode of the diode D1 is a smoothing capacitor to remove the pulse flow component included in the DC voltage rectified by the diode D1.

The first DC voltage VCC rectified and smoothed by the diode D1 and the capacitor C2 is supplied to the operating power supply voltage of the temperature controller 300, and the reverse voltage preventing diode D2 is provided through the resistor R2. Input is rectified. The second DC voltage VCC2 rectified by the diode D2 charges the capacitor C3 connected to the output node and at the same time, the operational amplifier OP1 and the ground potential determination unit 150 in the AC signal amplifier 140. Is supplied to the operating power supply of the comparator COMP1 in FIG. In this case, the capacitor C3 is designed to have a capacity of about 4 to 5 times the capacity of the capacitor C2, and the discharge time is set relatively long.

As described above, the first DC voltage VCC of a predetermined level (eg, 12VDC) is supplied to the temperature controller 300 by rectification and smoothing by the diode D1 and the capacitor C2 in the operation power supply unit 130. When 220VAC input through the pair of power lines AC1 and AC2 is supplied to the electric mat unit 200 through the temperature control unit 300, the electric mat unit 200 performs a normal heating function.

At this time, the shielding net 230 made of a conductive material surrounding the electric mat part 200 to block the electric field generated by the heating element (heating wire) 210 of the electric mat part 200 is connected through the terminal (G). It is connected in order of " resistance R11-switch SW2b in ground potential discrimination section setting unit 120-switch SW1b in power switch 110-power line AC2.

Therefore, if the power line AC2 to which the shielding network 230 is connected is a ground potential side line, that is, a neutral line, the electric field generated from the heating element 210 will be blocked through the shielding network 230 and the neutral line, but the hot line line), it is necessary to find out whether the power line AC2 is a neutral since the electric field is further increased.

In the AC signal amplifier 140 shown in FIG. 2, one side of the AC signal input including the resistor R3 and the capacitor C4 is connected to the front end of the switch SW2b in the ground potential discrimination section setting unit 120. The other side of the AC signal input device is connected to the non-inverting terminal (+) of the operational amplifier OP1 operated by the voltage rectified and smoothed by the diode D2 and the capacitor C3 of the operation power supply unit 130. .

In this case, the other side of the input resistor R5 having one side connected to the inverting terminal (−) of the operational amplifier OP1 is connected to the power line AC2 through the switch SW2b of the ground potential discrimination section setter 120. The feedback resistor R6 is connected between the inverting terminal (-) and the output terminal of the operational amplifier OP1. Therefore, since the non-inverting terminal (+) and the inverting terminal (-) of the operational amplifier OP1 are connected to the ground of the operation power supply unit 130 in common, they have the same potential, so that the amplification output of the operational amplifier OP1 is There will be no.

In addition, the inverting terminal (-) of the comparator COMP1 in the ground potential determining unit 150 is represented by the following equation 1 by the voltage divider R8 and R9 connected in series between both ends of the second DC voltage VCC2. The reference voltage Vref set as described above is input, and there is no output of the operational amplifier OP1, so that the output of the comparator COMP1 is output as logic "low", and the light emitting diode LED1 connected to the resistor R10 is turned off. Stay intact.

[Equation 1]

Vref = R9 / (R8 + R9) VCC2

Therefore, when the voltages of the single-phase two-wire type 200VAC are input to the pair of power lines AC1 and AC2 while the switches SW2a and SW2b located inside the initial ground potential determination section setting unit 120 are "on", Regardless of whether the potential of the power line AC2 is at the neutral line level or the hot line level, the output of the comparator COMP1 always remains "low" so that the light emitting diode LED1 is turned off. Keep it.
At this time, when the output of the comparator COMP1 is a logic "low", it is a ground potential power line detection signal that detects the power line AC2 as a ground potential power line. In contrast, when the output of the comparator COMP1 is output as a logic "high", the power line AC2 is disconnected. It is a live voltage power line detection signal detected by a live voltage power line.
In the above state, when the user presses the switches SW2a and SW2b in the ground potential discrimination section setting unit 120 configured as push switches, the switches SW2a and SW2b are respectively in an off state, that is, normal. A pair of common terminals COi (where i means 1 and 2) connected to the cross terminal NCi (where i means 1 and 2) are connected to a normal open terminal (NOi), respectively. It cuts the AC voltage of 220VAC supplied to the operation power supply unit 130 and the temperature control unit 300 from the power lines (AC1, AC2).

delete

When the ground potential determination section setting unit 120 cuts off the 200VAC AC voltage supplied to the operation power supply unit 130, the operation power supply unit 130 of FIG. 2 discharges the voltage charged in the capacitor C3 to the operational amplifier OP1. ), The comparator COMP1 and the reference voltage setting unit consisting of two resistors R8 and R9 connected in series supply an operating voltage. At this time, the operational amplifier OP1 in the AC signal amplifier 140 and the comparator COMP1 in the ground potential determination unit 150 may operate for about 10 seconds by the discharge voltage of the operation power supply unit 130. The capacity of C3) should be set appropriately.

Preferably, it is desirable to properly design the capacity of the resistor R2 and the capacitors C2 and C3 so that the charge of the capacitor C3 is fully charged within 1 second and the discharge lasts for about 10 seconds.

On the other hand, when the switches SW2a and SW2b in the ground potential discrimination section setting unit 120 are “off”, the input resistor R5 connected to the inverting terminal (−) of the operational amplifier OP1 in the AC signal amplifier 140. ) The other side is grounded, and is composed of a resistor (R3) and a capacitor (C4) so that the AC signal input unit only the AC signal input to the power line (AC2) non-inverting terminal (+) of the operational amplifier (OP1) By supplying to the operational amplifier OP1 outputs the amplified voltage Vo as shown in Equation 2 below.

[Equation 2]

Here, Vs is an AC signal input by the AC signal input unit R3 and capacitor C4.

In the above state, when the power line AC1 of the pair of power lines AC1 and AC2 is the neutral line and the ground potential of the neutral line and the power line AC2 is the hot line, the ratio of the operational amplifier OP1 The inverting terminal (+) outputs an AC voltage Vo amplified as shown in Equation 2 above with an AC signal of 60 Hz input through the path of “live line AC2-resistance R3-capacitor C4”.

The AC signal amplified and output from the operational amplifier OP1 is rectified by the diode D3 connected to the output node, and then smoothed by a smoothing circuit composed of a resistor R7 and a capacitor C5, so that the ratio of the comparator COMP1 is reduced. It is input to the inverting terminal (+). At this time, the level of the output voltage of the operational amplifier OP1 amplified by the voltage of the live AC signal is higher than the reference voltage Vref of Equation 1 described above.

Therefore, the output of the comparator COMP1 that inputs the reference voltage Vref and the output of the operational amplifier OP1 to the inverting terminal (-) and the non-inverting terminal (+), respectively, detects the power line AC2 as a live power line. By outputting a logic " high ", the light emitting diode LED1 connected to the output terminal thereof is turned on. At this time, the user checks the lighting state of the light emitting diode LED1 and recognizes that the power line AC2 is not a power line having a ground potential, that is, a neutral line. In other words, it recognizes that the power line cord has not been correctly inserted into the power socket to eliminate the field waves.

The user of the electrical appliance changes the direction of the plug of the power line cord, inserts it into the power socket, and then presses the switches SW2a and SW2b in the ground potential discrimination section setting unit 120 to “off” to determine whether the ground potential side line is once again. do.

At this time, the power line AC2 is a neutral wire in which the insertion direction of the plug is opposite to that described above, and the potential thereof is the ground potential. Therefore, the non-inverting terminal (+) of the operational amplifier OP1 in the AC signal amplifier 140 has no AC signal, and the input signal of the non-inverting terminal (+) of the comparator COMP1 of the discriminator 150 is If it is absent or very low, it becomes less than the reference voltage Vref set at the inverting terminal (−), so that the output of the comparator COMP1 is " low " and the light emitting diode LED1 connected to the output terminal is turned off.

As described above, the present earth potential determination device is able to accurately determine the earth potential of any power line of the pair of power lines for a few seconds while pressing the earth potential determination switch 150, thereby shielding the electrical mat 200 Since the ground potential is connected to the network 230, the electric field generated from the heating line 210 is blocked.

Although the configuration of the present invention has been described using an example of the electric mat for explanation, it can be applied to lighting equipment or home medical equipment for detecting the electric potential to cut off the electric field without connecting the ground wire separately.

In addition, in the configuration of the preferred embodiment of the present invention, the configuration of the ground potential determination section setting unit 120 has been described using a manual push switch, but may be used as long as insulation between input and output such as a relay or a solid state switch is possible. It should be noted.

For example, the switch (WS2a, SW2b) in the ground potential determination section setting unit 120 is the AC power input to the operation power supply for a predetermined time from the time when the AC voltage is supplied from the pair of power lines. You can use a timer relay with a pair of switches that shut off after supply. In the case of using such a timer relay, the user inserts the plug of the power line cord into the power socket (outlet) without having to operate the push button, and automatically connects the power switch 110 and the operation power supply unit 130 after a predetermined time. By cutting off and then returning (connecting) it has the advantage of not having to operate manually.

As described above, the grounding potential determining apparatus according to the present invention rectifies and charges an AC voltage input from the outside to supply operating power, and completely separates the AC voltage from the operating power and then uses the charged power to provide a battery ( As a method of discriminating ground potential as a separate power source using a battery) is used, unlike the method using a ground discrimination device and a double insulated transformer using a conventional human body, it is excellent in safety and accuracy, and thus a more accurate ground potential can be determined. have.

Claims (6)

In the device for determining the power line having a ground potential among a pair of power lines (AC1, AC2) for inputting a single-phase two-wire AC voltage (220VAC), The single-phase two-wire AC voltage 220VAC input to the pair of power lines AC1 and AC2 is converted into a DC voltage VCC and charged in the capacitor C3 connected to the output terminal thereof. An operation power supply unit 130 for discharging the voltage charged in the capacitor C3 in response to the blocking of 220VAC; A ground potential determination section connected between the pair of power lines AC1 and AC2 and a pair of input terminals of the operating power supply unit 130 to supply or cut off the AC voltage 220VAC to the operating power supply unit 130. A setting unit 120; An input of a switching path of one of the power lines AC1 and AC2 of the pair of power lines AC1 and AC2 which is operated by a DC voltage VCC output from the operation power supply unit 130 and connected to the ground potential determination section setting unit 120. An AC signal amplifier 140 for amplifying an AC signal at a terminal and an output terminal; Operated by a DC voltage (VCC) output from the operation power supply unit 130, the DC voltage is voltage-divided to set a reference voltage, and compares the reference voltage and the voltage output from the AC signal amplifier 140 As a result, the power line discrimination device having a ground potential, characterized in that it comprises a ground potential determination unit (150) for determining whether the power line connected to the input terminal of the AC signal amplifier (140) is a ground potential side line. The ground potential determining section setting unit 120 supplies an AC voltage 220VAC input to the pair of power lines AC1 and AC2 to the operation power supply unit 130 and is selected by a user. Power line discrimination device having a ground potential, characterized in that the pair of switches (SW2a, SW2b) for blocking the AC voltage supplied to the operating power supply 130. 3. The AC power supply unit 130 of claim 2, wherein the operation power supply unit 130 is connected to both ends of the pair of power lines AC1 and AC2 through the ground potential discrimination section setting unit 120 to a predetermined constant voltage level. The fixed voltage diode ZD1 to be fixed and the AC voltage fixed at the constant voltage level are rectified to charge the capacitor C3, and the capacitance is cut off by the AC voltage 220VAC of the ground potential discrimination section setting unit 120. And a rectifier circuit (R1, C1, D1, C2, R2, D2) for discharging the voltage charged in the device (C3) to supply the operating voltage of the AC signal amplifier 140 and the ground potential discriminator 150. A power line discrimination apparatus having a ground potential. The AC signal amplifier 140 is operated by a DC voltage VCC output from the rectifier circuits R1, C1, D1, C2, R2, and D2, and the pair of power lines AC1. , Non-inverting the signal of the common terminal COi of one of the switches SW2a and SW2b connected between the AC2 and the operation power supply unit 130 through the AC signal input devices R3 and R4. Input to the terminal and input the signal of the normal cross terminal (NCi) to the inverting terminal through the input resistor (R5), the inverting terminal and the output terminal in response to the blocking of the common terminal COi and the normal cross terminal (NCi) And an operational amplifier (OP1) for amplifying and outputting an AC signal input to the non-inverting terminal by a feedback resistor (R6) connected therebetween. 5. The DC voltage controller of claim 4, wherein the ground potential determination unit 150 has at least two resistors connected in series between the output terminals of the rectifier circuits R1, C1, D1, C2, R2, and D2. Reference voltage setters R8 and R9 for dividing the voltage to set the reference voltage, a second rectifier D3 rectifying the output of the AC signal amplifier OP1, the set reference voltage and the second rectifier D3. Is compared between the output node and the ground to the comparator COMP1 and the comparator COMP1 for comparing the voltage level output from the output voltage and outputting the live voltage power line detection signal and / or the ground potential power line detection signal according to the result. A power line discrimination device having a ground potential, characterized by comprising an indicator (LED1) that lights up in response to a power line detection signal. The single-phase two-wire AC voltage 220VAC supplied from the outside between the pair of power lines AC1 and AC2 and the common terminal COi of the pair of switches SW2a and SW2b. And a pair of power switches (SW1a, SW1b) for further connecting / blocking the power line discrimination device having a ground potential.

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