JPH01231616A - Line condition detector and electric device using the same - Google Patents

Abstract

PURPOSE:To decide whether line is ON or OFF, by judging whether or not the 2nd voltage based on the line voltage is over the predetermined rate against the 1st voltage based on the maximum voltage of the line. CONSTITUTION:When the voltage V1 of a voltage dividing circuit 10 exceeds the voltage V2 of a voltage holding circuit 12, an output is generated to a comparator Q3. In case three-phase AC voltage is applied normally to a line 1, the output V3 of the comparator Q3 becomes a pulse train of a specified cycle. Let the output voltage of a rectification circuit 10, i.e. the voltage at a point A be V0 and the forward voltage drop of a diode D8 be VD. The voltage V1 is a voltage value across a resistance R3 where the voltage V0 is divided by resistances R2 and R3. The voltage V2 is a value which the voltage across a resistance R5, where the voltage (V0-VD) is divided by resistances R4 and R5, is exponentially decreased with a time constant C2R5. A voltage attenuation detection circuit 14 therefore generates the output of a H level when V1>V2 regardless of the output voltage V0 of the rectification circuit. The ON or OFF state of the line 1 can thereby be discriminated, even if any load such as a motor, etc., to generate residual voltage is connected to the line 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a failure detection circuit in a contact welding state in a contact contactor or in a conductive state of a main circuit element in a solid state contactor. The present invention relates to a fault detection circuit suitable for detection.

[Conventional technology]

As described in Japanese Unexamined Patent Publication No. 61-220221, the conventional device is configured to detect a mismatch between the control voltage and the load-side voltage and to issue an output signal when the mismatch occurs.

[Problem to be solved by the invention]

The above conventional technology does not take into account the use of failure detection circuits over a wide voltage range; for example, if a 200V circuit is used in a 100V circuit, the control voltage and load side voltage will not match even if both are normal. There was a problem that the product could not be shared because it was considered a state.

An object of the present invention is to provide an electrical circuit state detection device that can be used in a wide voltage range, and can be used in common even at different voltages such as 100V and 200V, and an electrical device using the same.

[Means to solve the problem]

The above object includes a voltage holding means for detecting three phase voltages and generating and holding a first voltage based on the maximum voltage, and a voltage generating means for generating a second voltage based on the voltage of the electric circuit.
Comparing means for comparing the first voltage and the second voltage and determining means connected to the output of the comparing means are provided, and the comparing means is connected to the determining means when the second voltage value is When the voltage is equal to or higher than a predetermined ratio with respect to the first voltage value, the electric circuit is turned off.
generates a signal that is in the N state, and when the second voltage value is less than or equal to a predetermined ratio with respect to the first voltage value, the electric circuit is turned off.
Generates a signal that is in the F state, and determines whether the output of the comparison means is in the ON state, and determines whether the output of the comparison means is in the ON state.
This is achieved by configuring the circuit so that it is determined that the electrical circuit is abnormal when the two are different from each other.

[Effect]

The comparison means provided in the circuit state detection device compares a first voltage based on the maximum voltage of the circuit and a second voltage based on the voltage of the circuit, and determines whether the second voltage is higher than the first voltage. The electric circuit is turned on and off by determining whether the ratio is higher than a predetermined ratio.
Determine the condition. As a result, even if the voltage of the electric circuit differs, ON/OFF can be determined based on the ratio to the voltage. Furthermore, when one phase of the electrical circuit is in a non-conducting state, an output with a waveform different from that in the ON state is generated, so that an abnormality in the electrical circuit can be determined.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit state detection device according to a first embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

The circuit state detection device of this embodiment includes a rectifier circuit 10 connected to a three-phase circuit 1, a power supply circuit 12 connected to the rectifier circuit 10 and generating a substantially constant power supply voltage vCC, and a rectifier circuit 1
0 output voltage as input, and the power supply voltage ■ from the power supply circuit 12
The voltage attenuation detection circuit 14 is supplied with CC. The rectifier circuit 10 is a well-known three-phase bridge circuit formed by combining diodes D1 to D6. The power supply circuit includes a Zener diode ZD1 for generating a reference voltage and a Zener diode Z.
The additional resistance R1 of D1 and the base is a Zener diode zD
1, the collector is connected to the positive output of the rectifier circuit, and the emitter is connected to the negative output of the rectifier circuit via a diode D7 and a capacitor C1. The output vCC of the power supply circuit 12 is configured to be obtained from the anode side of a diode D7 connected in the forward direction to the emitter of the transistor Q1. The voltage attenuation detection circuit 14 includes a voltage divider circuit 10 as a voltage generating means consisting of resistors R2 and R3 connected in series, a diode D8, a resistor R4, and a diode D8 connected in series.
capacitor C2 connected in parallel with R5 and resistor R5
A voltage holding circuit 12 as a voltage holding circuit consisting of;
The voltage divided by the resistors R2 and R3 of the voltage dividing circuit and the voltage divided by the resistors R4 and R5 of the voltage holding circuit are each configured by a comparator Q2. Comparator Q2
is supplied with the power supply voltage VCC from the power supply circuit 12, the voltage 1 divided by the resistors R2 and R3 of the voltage dividing circuit is input to the positive side, and the voltage v2 divided by the resistors R4 and R5 of the voltage holding circuit is supplied. Each is supplied to the negative input.

As a result, as shown in FIG. 2(A), when the voltage v1 supplied by the voltage dividing circuit exceeds the voltage v2 supplied by the voltage holding circuit, an output is generated in the comparator Q3.
When the three-phase AC voltage is normally applied to the electric line 1, the output v3 of the comparator Q3 becomes a pulse train with a substantially constant period as shown in FIG. 2(B). Now, the output voltage of the rectifier circuit 10, that is, the voltage vO at point A, the diode D8
If the forward voltage drop is VD, then vl is the voltage across R3 when VO is divided by R2 and R3t', and v2 is the voltage value at both ends of R3 when vo-VD is divided by R4 and R5.
The value decreases exponentially with a time constant C2R5, with the peak at the voltage value ' across the line. The forward voltage drop VD of diode D8 is usually about 0.8V, so if the VO value is large and 0 can be ignored, v2 is the voltage across R5 when vO is divided by R4 and R5. As a peak value, the value decreases exponentially with a time constant C2R5.

Therefore, the voltage attenuation detection circuit 14 detects the rectifier circuit output voltage
Regardless of 0, when Vl>V2 holds, an H level output is generated.

As a result, vO changes to capacitor C as shown in Figure 3(A).
If the voltage drops faster than the discharge time constant of 2, the output 3 of the comparator Q2 remains at the L level.

Thereby, even if a load that generates residual voltage, such as a motor, is connected to the electric line 1, the ON/OFF state of the electric line 1 can be determined.

When there is an open phase in the electric line 1, the output of the rectifier circuit 10 has a large ripple as shown in FIG.
The output v3 of No. 2 generates a pulse train with a period different from that in the normal state and a different duty ratio. As a result, the circuit state detection device of this embodiment can determine whether the circuit is in a normal ON state or in an open phase state, regardless of the circuit voltage. To make this determination electrically, for example, output v3 is integrated by resistor R6 and capacitor C3 to convert it into a high or low voltage, and this voltage is determined by comparators Q3 and Q4 to determine whether it is high level, medium level, or low level. All you have to do is determine the level. Discrimination means 16
is configured like this, high level output in ON state, OF
It is possible to determine whether the electrical circuit is normal or abnormal by providing a low level output in the F state and a medium level output in the open phase state. Note that the voltage divided by the resistors R7 and R8 is set to be higher than the voltage divided by the resistors R9 and RIO. Further, Q5 is an AND circuit, and Q6 is a NOT circuit.

A second embodiment of the present invention will be described with reference to FIGS. 4 to 9.

This embodiment applies an uninvented method to a failure detection circuit for an electronic contactor.

The fourth part shows a block diagram of an electronic contactor equipped with a failure detection circuit in this embodiment, and its configuration includes an input circuit 121 connected to an input terminal 105, a control circuit 122 in the next stage, and a control circuit 122. Connected trigger circuit 12
3, a delay circuit 124, a connector 102 consisting of a main circuit element 125 energized by a trigger circuit 123, a rectifier circuit 141 that rectifies the load side voltage, and an internal circuit power supply circuit 1.
42, load side voltage attenuation detection circuit 143, and delay circuit 12
4, a smoothing circuit 144 driven by the signal state of the detection circuit 143, and a next-stage drive circuit 145.

The main parts of this embodiment will be explained with reference to FIG.

The rectifier circuit 141 is connected to each phase of the electric path, takes in the voltage of the electric path, rectifies it, and supplies it to the power supply circuit 142 and the attenuation detection circuit 143. The power supply circuit 142 is a constant voltage circuit, which converts the voltage supplied from the rectifier circuit 141 into a substantially constant voltage and supplies it to the failure detection circuit 143 and the relay 108 as a power supply voltage vCC.

The voltage attenuation detection circuit 143 includes resistors 172 and 173 that voltage divide the output of the rectifier circuit 141, an amplifier 171 whose non-inverting input terminal is connected to this voltage dividing point, and a diode 174 connected to the output terminal of the amplifier 171. , a capacitor 17G connected to a series circuit of a resistor 175, and a parallel circuit of a resistor 177. The positive terminal of a capacitor 176 is connected to an amplifier 17.
a peak hold circuit connected to the inverting input terminal of 1;
The amplifier 178 is connected to the output terminal of the amplifier 171, and is subjected to negative feedback so as to have a gain of 1, thereby operating as a voltage follower.

The smoothing circuit 144 consists of a diode 179, a resistor 180, and a capacitor 181 connected in series, and the delay circuit 124 is connected in parallel to a well-known delay circuit, a photocoupler light emitting section 107a connected to its output, and a capacitor 181 of the smoothing circuit 144. It consists of a series connection circuit of a resistor 182 and a light emitting section 107b.

The drive circuit 145 consists of a transistor 163 whose base is connected to the positive terminal of a capacitor 181 of the smoothing circuit 144 via a resistor 160, and a capacitor 161 and a resistor 162 whose base and emitter loads of the transistor 163 are respectively connected in parallel.

The collector of the transistor 163 of the drive circuit 145 is connected to the output terminal 106 of the failure detection circuit, and the output terminal 106 includes a series circuit of the relay 108 and a resistor 164, and a diode connected in parallel with this series circuit to form a flywheel circuit. 165 is connected.

Next, its operation will be explained. The alphabetic characters in the waveform in Figure 6 are number 5.
The waveform of the alphabetic part of the circuit diagram shown in the figure is shown.

When the main circuit element 125 is operating normally, the amplifier 171 of the attenuation detection circuit 143 outputs an output when the voltage at the non-inverting input terminal exceeds the voltage at the inverting input terminal for each ripple of the rectified waveform of the rectifier circuit 141. occurs. As a result, D
The part has a pulse output as shown in (1), but since the output of the control circuit 122 is at H level, the photocoupler 10
Since the light emitting section 107a of No. 7 emits light and the light receiving section 107b is conductive to sink the current, the E part waveform becomes L level as shown in (E). As a result, the output of the smoothing circuit 144 is L.
level, the transistor 163 of the drive circuit 145 connected thereto becomes non-conductive, and the relay 108 is not excited, indicating that the main circuit element 125 is in a normal state.

Next, when an OFF signal (H-+L in FIG. 6(A)) is output from the control circuit of the contactor 125 which is normally ON, the A section voltage attenuates. At this time, if a load that generates a residual voltage such as an electric motor is connected to the load side of the electric line 101, the voltage on the load side of the electric line 101 is attenuated as shown in (a), and after the release time is delayed, the delay circuit outputs Like H
-) becomes L.

As a result, the photocoupler light receiving section 107b is turned off, but the D section already has no pulse output and the capacitor 18
The potential of 1 remains at the L level as shown in (o) of the E part waveform. As a result, the relay 108 connected to the detection circuit output terminal 106 is not excited, indicating whether the main circuit element 125 is in a normal state.

Next, a case where the main circuit element 125 fails will be explained. When a semiconductor element is used as the main circuit element 125, a short-circuit mode failure occurs when a current exceeding the rating flows. In the case of three phases, when only one element is short-circuited, the load 103 is normally turned on and off by the other two elements, ensuring safety.

Next, if two of the main circuit elements 125 have a short-circuit failure, even if the remaining normal element is turned off, current will continue to flow to the load 103 in an open phase state through the two failed elements, creating a dangerous situation. There are cases.

In this case, the control circuit 122 sends an off signal (see FIG. 6).
When H-)L) of a) is output, the A part voltage becomes an open-phase (single-phase) waveform as shown in (force). After the delay time, when the delay circuit output becomes L level as shown in (T), the photocoupler light emitting section 107a is turned off, and the photocoupler light receiving section 10
7b is turned off. As a result, the capacitor] 81 of the smoothing circuit 144 becomes in a chargeable state, and the pulse waveform shown in FIG. As shown in FIG. 7E, the potential of the positive electrode of the capacitor 181 increases. This turns on transistor 163 of drive circuit 145 and energizes the coil of relay 108, indicating that main circuit element 125 is in a faulty state. Although not shown, the relay 108 is provided with a contact point. - For example, if a normally closed contact is used, this normally closed contact is connected to a magnetic trip device of a circuit breaker (not shown) installed above, and the circuit breaker interrupts the circuit when a fault is detected. You may also do so.

For example, when a normally closed contact is used, this normally closed contact may be connected to the coil of an electromagnetic contactor provided above, and the circuit may be interrupted by this electromagnetic contactor when a failure is detected. Further, these contacts may be used to turn on an indicator light or issue a warning using a buzzer or the like, if necessary.

According to this embodiment, there is no need to set a delay time, and the operation can be performed at the first peak of the load voltage at the time of a short-circuit failure, resulting in high speed. Also, it does not use a fixed voltage setting such as a Zener diode. Since the normal voltage is used as the reference voltage, it has the effect of being able to operate at high speed over a wide range of voltages, such as 100V to 200V. Note that if the Zener voltage is used as the reference voltage, the time it takes for the load voltage to decay to the reference voltage in the event of a failure differs depending on the voltage class, so it can only handle a narrow range of voltages, such as 100V,
It is not possible to obtain a device that can share 200V.

A modification of this embodiment will be explained with reference to FIGS. 7 to 9.

A first modification of this embodiment is shown in FIG.

In this modification, the smoothing circuit 144 in FIG.
It was set to 6. The latch circuit 146 may use a well-known thyristor, latch IC, or the like. Thereby, variations in operating time due to variations in capacitance can be eliminated, and accurate operating characteristics can be obtained.

A second modification of this embodiment is shown in FIG.

In this modification, a comparator 182 is added to the smoothing circuit 144, and since this modification has a high impedance input, it has the effect of reducing the ripple of the capacitor 181.

A third modification of this embodiment is shown in FIG.

In this modification, the voltage attenuation detection circuit itself has delay characteristics,
Similar functionality is obtained without using the delay circuit 124. The voltage attenuation detection circuit 148 in this modification example outputs the ON signal and OFF signal of the control circuit 122 to the photocoupler 107.
This signal makes the analog switch 190 conductive or non-conductive, and this state is transmitted to the voltage attenuation detection circuit 148 via a differential circuit connected in series with the analog switch 190. switch 1
91 to obtain a delay.

When the control circuit 122 outputs the ON signal, the C terminal of the analog switch 190 becomes LOW and i-.

Since the C terminal of the analog switch 191 also becomes LOW, and the I-O line becomes non-conductive, the peak hold circuit capacitor 176 in the next stage is charged to the peak voltage of the resistor 173.

Next, when the control circuit 122 outputs an OFF signal, the C terminal of the analog switch 190 becomes High, and conduction occurs between I and O. Therefore, the C terminal of the analog switch ]-91 is connected to the differential circuit capacitor 194 and the resistor 193. and 1
95 and a differentiating circuit configured with
The potential gradually decreases from the level and becomes Low after a certain period of time determined by the time constant of the differential circuit. Therefore analog switch 1
91 i-.

is conductive when the C terminal is High, that is, the comparator 1
Since the non-inverting input terminal 71 becomes approximately O, the potential of the capacitor 181 at the next stage becomes approximately O, and the output of the voltage attenuation detection circuit can be delayed until the analog switch 191 becomes non-conductive.

According to this embodiment, load voltage, three-phase two-element short circuit, three-phase three
Regardless of the element short circuit or the attenuation characteristics of the load residual voltage, the short circuit fault can always be detected at the first peak of the load voltage after the release time delay, so it can be applied to a wide range of voltages, such as 100V and 200V common. This has the effect of achieving a versatile failure detection circuit that can operate at high speed without adjustment for various loads.

A third embodiment of the present invention will be explained with reference to FIGS. 10 to 16.

In this embodiment, the present invention is applied to a reversible electronic contactor.

A conventional failure detection device is, for example, disclosed in Japanese Utility Model Application No. 61-15721.
As described in No. 4, when the load voltage and the conduction signal do not match, it is detected as a short-circuit failure of the element.

However, no consideration is given to failure detection of reversible electronic contactors, and if this is simply applied to reversible electronic contactors, for example, during forward rotation, the reverse contactor becomes a blade non-conducting input. However, since the load voltage is approximately the power supply voltage, when a fault detection circuit is built into the reversing contactor, there is a problem in that it generates a fault signal even if it is normal. Ta.

In this embodiment, when a fault detection circuit is installed in a contactor with a built-in fault detection circuit or in each contactor, the operation of the fault detection circuit of a non-conducting contactor is prohibited ( Or, failure can be detected by logical sum output of forward and reverse rotation and load voltage logic (there is a logical sum output; if the load voltage is cloudy, it will be an open fault, and if it is reversed, it will be a short circuit fault). This provides a failure detection circuit that can also be applied to reversible electronic contactors.

FIG. 10 shows an internal block diagram and reversible connections of a solid state contactor with a built-in failure detection circuit in this embodiment. Since the contactor 201 for forward rotation and the contactor 202 for reverse rotation are the same, the contactor for forward rotation will be explained. A power supply circuit 280 supplies power to an input circuit 281 and a control circuit 282. The input circuit 281 is composed of a circuit that smoothes ripples in the case of AC input, for example.

The control circuit 282 determines whether or not the input signal is within a predetermined voltage range, and determines whether the subsequent stage circuit operates or not.

One output of the control circuit 282 makes the main switching element 288 conductive via the gate circuit 283, and the other output is
The conduction and non-conduction signals are transmitted via the delay circuit 284 to a failure detection circuit 285, a reversible interlock circuit 287, and a failure detection interlock circuit 286.

Now, if the forward rotation input switch 206 is turned on, the reversible interlock circuit 287 is connected to the input circuit 291 of the reverse rotation contactor 202 or the control circuit 2 through the terminals 213 and 224.
92 or gate circuit 293. As a result, the reverse contactor 202 becomes non-conductive. Furthermore, the failure detection interlock circuit 286 is connected to the terminal 212.2.
26, the failure detection circuit 295 is locked, so only the normal rotation contactor 201 operates.

The internal circuit of the forward rotation contactor 201 is shown in FIG.

The failure detection circuit 285 is connected to the delay circuit via a photocoupler 217. In addition, in the failure detection circuit 285, D203 to D208 are rectifying diodes, and RY201
is a relay, and has a common contact 215c, a normally open contact 215a, and a normally closed contact 215b.

In FIG. 11, R201 to R211 are resistors, D2
01 is a diode bridge, D202 to D208 are diodes, C201 to C203 are capacitors, Q201 is a transistor, Q202 is a comparator, Q203 is an inverting circuit, Q204 is a buffer, Q205 to Q209 are photocouplers, and 211a.

211b is an input terminal for a control signal; 214a and 214b are input terminals for an interlock signal from a reversible interlock circuit of a reversing contactor; and 212a.

212b is the output terminal of the failure detection interlock circuit; 21
3'a and 213b are output terminals of the reversible interlock circuit;
216a and 216b are output terminals for a signal that locks the failure detection circuit of the reversing contactor in an inoperative state. Moreover, 283a, 283b, and 283c are gate circuits of the switching elements 288 of each phase of the electric circuit.

According to this embodiment, even if solid-state contactors with a built-in failure detection circuit are reversible, the failure detection circuits of each contact are locked, so that false detection will not occur.

FIG. 12 and FIG. 13 are diagrams showing implementation diagrams of this embodiment, in which the interlock signal transmission/reception terminal 212a.

212b, 213a, 213b, 214a, 214b,
, 216a, 216b are receptacles 215 for mounting printed circuit boards, and are connected to the other glue receptacle 252 with a flat cable 253.

According to this embodiment, the non-reversible type can be used alone, and the reversible type can easily be interlocked with a connector, and requires less mounting space than screw terminals. Can be done.

A first modification of this embodiment is shown in FIGS. 14 and 15.

In this modification, a forward rotation contactor and a reverse rotation contactor are mounted on the same heat sink, and interlock signals and the like are transmitted and received by photodiodes and phototransistors provided facing each other.

According to this modification, interlock can be established simply by providing the forward rotation contactor and the reverse rotation contactor adjacently.

A second modification of this embodiment is shown in FIG. 16.

In this modification, a reversible failure detection unit 208 is installed separately, and the detection is performed using the logic of the logical sum output of the forward rotation input and reverse rotation input and the load voltage. It is designed to detect a short circuit failure when voltage is present.

According to this modification, only one detection circuit is required, so it is economical.

According to this embodiment, a failure in the main switching element can be detected even in the case of a reversible type, so there is an effect of increasing the safety of the system.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an electric path state detection device that can be used in a wide voltage range and that can be used in common across different voltage ranges, and an electric device using the same.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing the configuration of a circuit state detection device in a first embodiment of the present invention, and FIG. 2(A). (B) is a diagram showing the input waveform and output waveform of the comparator in this example, and FIG. 3 (A). (B) is a diagram showing the input waveform and output waveform of the circuit state detection device when the circuit is normal and when the circuit has an open phase, respectively, and FIG. 4 is the circuit state detection device in the second embodiment of the present invention. FIG. 5 is an electric circuit diagram showing the specific structure of the failure detection circuit section in this embodiment.
Figures 6 (A) to (E) are Figure 5 A to (E) in normal cases.
Figures 6 (force) to (ri) are diagrams showing the waveforms of parts A, D, and E in Figure 5 at the time of failure, respectively. Figure 7 is the first modification of this embodiment. A block diagram showing the main parts of the example, FIG. 8 is an electric circuit diagram showing the main parts of the second modification of the present example, and FIG. 9 is an electric circuit diagram showing the main parts of the third modification of the present example. , FIG. 10 is a block diagram showing the configuration of an electronic contactor with a reversible interlock equipped with a failure detection circuit using a circuit state detection device according to a third embodiment of the present invention, and FIG. 11 shows the main parts of this embodiment. FIG. 12 is an electronic circuit diagram showing the wiring between each terminal when this embodiment is mounted, FIG. 13 is a perspective view showing the mounting state of this embodiment, and FIGS. 14 and 15. The figures are a plan sectional view and a front sectional view showing the main parts of the first modified example of the present embodiment, and the first modified example.
FIG. 6 is an electrical circuit diagram showing a second modification of this embodiment. 10.110: Voltage generation means, 12, 112: Voltage holding means, 162 discrimination means, 104.285.295: Failure detection circuit, 125.288.298: Opening/closing means, 144
: Control means, 145: Output means, 171, Q2: Comparison means ~〉〉〉 S 4 figures and a half! 6 Figure Sheep lI) Figure 2η 20! ; 20 Dosl Be FC

Claims (1)

[Claims] Voltage holding means for detecting the voltages of the first and third phase electric circuits and generating and holding a first voltage based on the maximum voltage, and generating a second voltage based on the voltage of the electric circuits. a voltage generating means for comparing the first voltage and the second voltage, a comparing means for comparing the first voltage and the second voltage, and a determining means connected to the output of the comparing means; The electric circuit is turned on when the second voltage value is equal to or higher than a predetermined ratio with respect to the first voltage value.
The determining means generates a signal indicating that the electric circuit is in an OFF state when the second voltage value is less than or equal to a predetermined ratio with respect to the first voltage value, and the determining means 1. An electrical circuit state detection device, characterized in that it is configured to determine that the electrical circuit is abnormal when the output of the electrical circuit is different from both an output in an ON state and an output in an OFF state. A switching means connected to a two- or three-phase electric circuit and controlled to be in either an ON state or an OFF state by a control signal, and a switching means provided on the secondary side of the switching means to detect a failure of the switching means. In an electrical device, the failure detection circuit includes voltage holding means for detecting the voltage of the electric line and generating and holding a first voltage based on the maximum voltage; a voltage generating means for generating a second voltage based on the voltage, a comparing means for comparing the first voltage and the second voltage, and an output of the comparing means is controlled based on a control signal of the opening/closing means. The comparison means includes a control means and an output means for generating an output based on the output of the control means, and the comparison means controls the electric circuit when the second voltage value is equal to or higher than a predetermined ratio with respect to the first voltage value. is configured to generate a signal indicating that the electric circuit is in an ON state and to generate a signal indicating that the electric circuit is in an OFF state when the second voltage value is less than a predetermined ratio with respect to the first voltage value, and the control means It is configured to transmit the output of the comparing means to the output means when a control signal for turning off the opening/closing means is given to the control means, and the output means generates an output to detect an abnormality in the opening/closing means. An electrical device configured to detect.