INTERFERENCE FILTER

Abstract

Interference suppression filter (15) for an electrical device (4) connected to an AC power supply (1), comprising a first electrode (3) connected to a ground of a power supply and a second electrode (2) not connected to the ground of the power supply, wherein the interference suppression filter (15) comprises: a first power supply line (5) which is connected to one of the first electrode (3) and the second electrode (2); a second power supply line (6) which is connected to the other from the first electrode (3) and the second electrode (2); a first Y-capacitor (7) which is connected to the first power supply line (5); a second Y-capacitor (9) connected to the second power supply line (6); a first relay (8) connected between the first Y-capacitor (7) and a ground of an electrical device; a second relay (10) which is connected between the second Y-capacitor (9) and the ground of the electrical device; a ground-side power supply line detection circuit (12) which is connected to the first power supply line (5) and the second power supply line (6) respectively, and detects a power supply line connected to the first electrode (3) from the first power supply line (5) and the second power supply line (6); and a control circuit (13) to determine whether a power supply line connected to the first electrode (3) is the first power supply line (5) or the second power supply line (6), based on a detection result by the ground-side power supply line detection circuit (12), which controls the first relay (8) to create a short circuit between the first Y-capacitor (7) and the ground of the electrical equipment when it is determined that the power supply line connected to the first electrode (3) is the first power supply line (5), and controls the second relay (10) to create a short circuit between the second Y-capacitor (9) and the ground of the electrical equipment when it is determined that the power supply line connected to the first electrode (3) is the second power supply line (6).

Description

TECHNICAL AREA

[0001] The present disclosure relates to a noise suppression filter. BACKGROUND ON THE STATE OF THE TECHNOLOGY

[0002] In an electrical device, a capacitor, designated as a Y-capacitor, can be connected between a plurality of power supply lines, each connected to any electrode from a plurality of electrodes of an alternating current supply, and a ground attached to the electrical device (hereinafter referred to as the electrical device ground). The Y-capacitor functions as a common-mode filter circuit that reduces common-mode interference generated outside the electrical device and mixed within the electrical device, using each electrode of the alternating current supply, each power supply line, and the electrical device ground as paths in that order.

[0003] Patent literature 1 describes a noise suppression device installed in an electrical device. The noise suppression device comprises two power supply lines, and a Y-capacitor is arranged between the two power supply lines and the electrical device's ground. Furthermore, the noise suppression device includes a changeover switch, which toggles the connection to one of the two power supply lines, arranged between the two power supply lines and the Y-capacitor. Accordingly, the power supply line connected to the Y-capacitor is switched. An AC power supply connected to the noise suppression device comprises a ground-side electrode connected to ground (hereinafter referred to as the power supply ground) and a non-ground-side electrode that is not connected to the power supply ground.

[0004] Which of the two power supply lines of the interference suppression device is connected to the ground electrode of the AC power supply and which is connected to the non-ground electrode of the AC power supply is not constant, as this is determined by the direction in which the mains plug, which connects the two power supply lines, is inserted into the mains socket. Therefore, the switch described above is used to switch the power supply line connected to the Y-capacitor.

[0005] As a further example, patent literature 2 discloses an electrical device equipped with a noise filter circuit containing two capacitors and a relay, wherein one of the capacitors is provided between a line with a power supply relay and a device ground, the other of the capacitors is provided between a line without a power supply relay and the device ground, and the relay switches the connection between a line without a power supply relay and the device ground via the capacitor.

[0006] As a further example, patent literature 3 discloses a noise filter with Y-capacitors connected between power supply lines and ground, and a switch located between a connection point of the Y-capacitors and ground.

[0007] As yet another example, patent literature 4 describes a passive filter circuit containing two chokes, a capacitor and a contactor connected in series with the capacitor. REFERENCE LIST PATENT LITERATURE Patent Literature 1: JP H11-88096 A Patent Literature 2: JP 2008-301585 A Patent Literature 3: JP 2005-184074 A Patent literature 4: EP 3785358 B1 SUMMARY OF THE INVENTIONAL PROBLEM

[0008] If, in the interference suppression device described in patent literature 1, the power supply line to be connected to the Y-capacitor is connected to the non-ground electrode of the AC power supply, applying an AC voltage to the Y-capacitor will generate a leakage current. Since there is a risk of electric shock to the human body, the leakage current must be kept below a certain value. In this case, the interference suppression device can reduce the leakage current to a certain value or less by switching the power supply line to be connected to the Y-capacitor to the power supply line connected to the ground electrode.However, the interference suppression device described in patent literature 1 has no specific configuration for switching the power supply line to be connected to the Y-capacitor, apart from the switch described above, and it is possible that such switching cannot necessarily be carried out.

[0009] The present disclosure was made to solve the above-mentioned problem, and one purpose of the present disclosure is to provide a technique capable of properly switching a power supply line to be connected to a Y-capacitor. SOLUTION TO THE PROBLEM

[0010] A noise suppression filter according to the present disclosure is a noise suppression filter for an electrical device connected to an AC power supply, comprising a first electrode connected to a ground of the power supply and a second electrode not connected to the ground of the power supply, wherein the noise suppression filter includes: a first power supply line connected to one of the first and the second electrodes; a second power supply line connected to the other of the first and the second electrodes; a first Y-capacitor connected to the first power supply line; a second Y-capacitor connected to the second power supply line; a first relay connected between the first Y-capacitor and the ground of the electrical device;a second relay connected between the second Y-capacitor and the ground of the electrical device, a ground-side power supply line detection circuit connected to both the first and second power supply lines, and a power supply line connected to the first electrode detecting from both the first and second power supply lines;and a control circuit to determine whether a power supply line connected to the first electrode is the first power supply line or the second power supply line, based on a detection result by the ground-side power supply line detection circuit, which controls the first relay to create a short circuit between the first Y-capacitor and the ground of the electrical equipment when it is determined that the power supply line connected to the first electrode is the first power supply line, and controls the second relay to create a short circuit between the second Y-capacitor and the ground of the electrical equipment when it is determined that the power supply line connected to the first electrode is the second power supply line. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0011] According to the present disclosure, it is possible to switch the power supply line connected to the Y-capacitor correctly. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram showing a configuration of an electrical device according to a first embodiment. Fig. Figure 2 is a flowchart showing a power supply line switching procedure through a noise suppression filter according to the first embodiment. Fig. Figure 3 is a block diagram showing the configuration of an electrical device according to a second embodiment. Fig. Figure 4 is a flowchart showing a power supply line switching procedure through a noise suppression filter according to the second embodiment. Fig. Figure 5 is a graph showing a voltage detected by an A / D converter, the operation of a relay and a current flowing through a Y capacitor in a configuration that differs from a configuration of a third embodiment. Fig. Figure 6 is a graph showing a voltage detected by an A / D converter, the operation of a relay and a current flowing through a Y capacitor in a configuration of the third embodiment. Fig. Figure 7 is a block diagram showing a configuration of an electrical device according to a fourth embodiment. Fig. Figure 8 is a flowchart showing a power supply line switching procedure through a noise suppression filter according to the fourth embodiment. Fig. Figure 9 is a block diagram showing a configuration of an electrical device according to a fifth embodiment. Fig. Figure 10 is a flowchart showing a power supply line switching procedure according to the fifth embodiment. Fig. Figure 11 is a block diagram showing a configuration of an electrical device according to a sixth embodiment. Fig. Figure 12 is a flowchart showing a power supply line switching procedure through a noise suppression filter according to the sixth embodiment. Fig. Figure 13 is a block diagram showing a configuration of an electrical device according to embodiments six to nine. Fig. Figure 14 is a flowchart showing a power supply line switching procedure through a noise suppression filter according to the seventh to ninth embodiments. Fig. 15A is a block representation which represents a hardware configuration for implementing functions of an installation-side power supply line detection circuit and a control circuit of an interference suppression filter according to the first to ninth embodiments. Fig. Figure 15B is a block diagram showing a hardware configuration for running software to implement the functions of the installation-side power supply line detection circuit and the control circuit of the interference suppression filter according to the first to ninth embodiments. DESCRIPTION OF THE EXECUTION FORMS

[0012] In order to explain the present disclosure in more detail, a method for carrying out the present disclosure is described below with reference to the attached drawings. First embodiment.

[0013] Fig. Figure 1 is a block diagram showing a configuration of an electrical device 4 according to a first embodiment. As in Fig. As shown in Figure 1, the electrical device 4 comprises an interference suppression filter 15 and a main circuit 14 of the electrical device. The interference suppression filter 15 comprises a power supply line 5, a power supply line 6, a Y-capacitor 7, a relay 8, a Y-capacitor 9, a relay 10, an X-capacitor 11, a ground-side power supply line detection circuit 12, and a control circuit 13.

[0014] An AC power supply 1, to which an electrical device 4 is connected, has an electrode 2 (second electrode) that is not connected to the ground of the power supply, and an electrode 3 (first electrode) that is connected to the ground of the power supply. In the first embodiment, the AC power supply 1 is a single-phase, two-wire power supply. The AC power supply 1 may include a transformer for conversion or the like. It should be noted that the first embodiment describes a configuration in which the AC power supply 1 is a single-phase, two-wire power supply and comprises two electrodes, electrode 2 and electrode 3.However, the AC power supply 1 only needs to contain at least a plurality of electrodes, and each of the plurality of electrodes is connected to the mass of the power supply, and the number of electrodes contained in the AC power supply 1 is not specifically limited.

[0015] Electrical device 4 is a device that operates with AC power supply 1. The type of electrical device 4 is not specifically restricted.

[0016] Power supply line 5 and power supply line 6 (the first power supply line and the second power supply line) of the interference suppression filter 15 are each a conductive wire for connection to the AC power supply 1. Power supply line 5 is connected to either electrode 2 or electrode 3. It should be noted that power supply line 5 in Fig. 1 is connected to electrode 2. The power supply line 6 is connected to either electrode 2 or electrode 3. That is, the power supply line 6 is connected to the other electrode, which is different from the electrode to which the power supply line 5 is connected. It should be noted that the power supply line 6 in Fig. 1 is connected to electrode 3.

[0017] It should be noted that the first embodiment describes a configuration in which the interference suppression filter 15 comprises two power supply lines, power supply line 5 and power supply line 6. However, the interference suppression filter 15 can comprise three or more power supply lines. The interference suppression filter 15 only needs to comprise at least the same number of power supply lines as the number of electrodes contained in the AC power supply 1.

[0018] The Y-capacitor 7 (first Y-capacitor or second Y-capacitor) is connected to the power supply line 5. More precisely, the Y-capacitor 7 is connected to a branch line of the branched power supply lines 5.

[0019] Relay 8 is connected between Y-capacitor 7 and the ground of the electrical device. That is, Y-capacitor 7 and relay 8 are connected in series. Relay 8 either creates a short circuit between Y-capacitor 7 and the ground of the electrical device or opens between Y-capacitor 7 and the ground of the electrical device. It should be noted that relay 8 remains open between Y-capacitor 7 and the ground of the electrical device until a signal is received from the control circuit 13, which will be described later. This means that relay 8 can only create a short circuit between Y-capacitor 7 and the ground of the electrical device when the coil inside relay 8 is energized.

[0020] The Y-capacitor 9 (first Y-capacitor or second Y-capacitor) is connected to the power supply line 6. More precisely, the Y-capacitor 9 is connected to a branch line of the branched power supply lines 6.

[0021] Relay 10 (first relay or second relay) is connected between Y-capacitor 9 and the ground of the electrical system. That is, Y-capacitor 9 and relay 10 are connected in series. Relay 10 (first relay or second relay) either creates a short circuit between Y-capacitor 9 and the ground of the electrical system or opens between Y-capacitor 9 and the ground of the electrical system. It should be noted that relay 10 remains open between Y-capacitor 9 and the ground of the electrical system until it receives a signal from control circuit 13, which will be explained later. That is, relay 10 can only create a short circuit between Y-capacitor 9 and the ground of the electrical system when the coil inside relay 10 is energized.

[0022] Specifically, with regard to the Y-capacitor 7 and the Y-capacitor 9, in a case where the capacitance value of the Y-capacitor 7 and the Y-capacitor 9 is C [F], an upper limit of a leakage current in the interference suppression filter 15 I [A] is, an angular frequency of the AC power supply is 1 ω [rad / s] and the power supply voltage of the AC power supply is 1 V [V], the capacitance value C [F] of the first Y-capacitor Y and of the second Y-capacitor 9 follows the formula (1). C≥Iω×V

[0023] However, the upper limit of the leakage current in the interference suppression filter 15 and the power supply voltage of the AC power supply 1 are each effective values. For example, if the upper limit of the leakage current in the interference suppression filter 15 is 1 mA, the angular frequency of the AC power supply 1 is 2π × 50 Hz [rad / s], and the power supply voltage of the AC power supply 1 is 100 V, then each of the capacitance values ​​of the Y-capacitor 7 and the Y-capacitor 9 is equal to or greater than 31.8 nF. In a case where, in addition to the Y-capacitor 7 and the Y-capacitor 9, there is a factor that generates a leakage current, or in a case where a leakage current is generated by applying a voltage with a different angular frequency than the angular frequency of the AC supply 1 to the Y-capacitor 7 and the Y-capacitor 9, it is necessary to lower the upper limit of the leakage current in the interference suppression filter 15.

[0024] It should be noted that in the first embodiment a configuration is described in which the interference suppression filter 15 comprises two Y-capacitors consisting of Y-capacitor 7 and Y-capacitor 9 and two relays consisting of relay 8 and relay 10, but the interference suppression filter 15 can also comprise three or more Y-capacitors and three or more relays. The interference suppression filter 15 only needs to include at least the same number of power supply lines as the number of electrodes contained in the AC power supply 1.

[0025] The X-capacitor 11 is connected between power supply line 5 and power supply line 6. More precisely, the X-capacitor 11 is connected between the other branch line of the branched power supply line 5 and the branch point of the branched power supply line 6.

[0026] The ground-side power supply line detection circuit 12 is connected to both power supply line 5 and power supply line 6. More precisely, the ground-side power supply line detection circuit 12 is connected to each of the other branches of the branched power supply lines 5 and the other branch of the branched power supply lines 6. The ground-side power supply line detection circuit 12 detects a power supply line (ground-side power supply line) connected to electrode 3 from power supply lines 5 and 6. The ground-side power supply line detection circuit 12 detects, for example, the voltage of the power supply line connected to electrode 3.

[0027] Control circuit 13 is connected to relay 8, relay 10, and the ground-side power supply line detection circuit 12. Based on the detection result of the ground-side power supply line detection circuit 12, control circuit 13 determines whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. If it is determined that the power supply line connected to electrode 3 is power supply line 5, control circuit 13 activates relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device.If, on the other hand, it is determined that the power supply line connected to electrode 3 is the power supply line 6, the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device.

[0028] The main circuit 14 of the electrical device includes all circuits required for the operation and the like of the electrical device 4, with the exception of the interference suppression filter circuit 15 described above.

[0029] The operation of the interference suppression filter 15 according to the first embodiment is described below with reference to the drawings. Fig. Figure 2 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the first embodiment.

[0030] As in Fig. As shown in Figure 2, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST1).

[0031] The control circuit 13 then starts operation (step ST2). It should be noted that at this point, the circuit operation that generates the strong disturbance has not yet started.

[0032] Next, the ground-side power supply line detection circuit 12 detects the power supply line connected to electrode 3 from power supply line 5 and power supply line 6 (step ST3). The ground-side power supply line detection circuit 12 outputs a detection result to the control circuit 13.

[0033] Next, the control circuit 13 determines, based on the detection result of the ground-side power supply line detection circuit 12, whether the power supply line 5 connected to the electrode 3 is a power supply line (a ground-side power supply line) (step ST4).

[0034] If it is determined that the power supply line 5 is the power supply line connected to the electrode 3 (YES in step ST4), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST5).

[0035] If it is determined that the power supply line 5 is not the power supply line connected to electrode 3 (NO in step ST4), the control circuit 13 activates the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device (step ST6). It should be noted that in the example of Fig. 1, since the power supply line 5 is not a power supply line connected to the electrode 3, the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device.

[0036] As the next step of step ST5 or step ST6, the main circuit 14 of the electrical device starts a switching operation (main operation of the electrical device 4) in which a relatively large disturbance is generated (step ST7).

[0037] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST8). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0038] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the first embodiment described above. (Effect 1)

[0039] Due to the operation of the interference suppression filter 15 described above, the Y-capacitor is only connected between the ground-side power supply line, which is connected to the ground of the power supply via electrode 3 of the AC power supply 1 and the ground of the electrical device, but not between the non-ground-side power supply line, which is not connected to the ground of the power supply, and the ground of the electrical device. The voltage fluctuation between the power supply line and the ground of the electrical device at the frequency of the AC power supply 1 is lower in the ground-side power supply line than in the non-ground-side power supply line.Therefore, for example, in a configuration where the Y-capacitor is connected to all power supply lines, the Y-capacitor is also connected to the non-ground-side power supply line, which exhibits a greater voltage fluctuation than the ground-side power supply line, thus increasing the leakage current. On the other hand, since the Y-capacitor in the interference suppression filter 15 according to the first embodiment can only be connected to the side of the ground-side power supply line where the voltage fluctuation is lower than on the non-ground-side power supply line, the leakage current can be significantly reduced. (Effect 2)

[0040] The interference suppression filter 15 according to the first embodiment adopts a configuration in which the ground-side power supply line detection circuit 12 and the control circuit 13 detect the power supply line connected to the ground of the power supply and switch the connection destination of the Y-capacitor based on the detection result. Therefore, even in a case where the interference suppression filter 15 is applied to the electrical equipment where a power supply line is not necessarily connected to a fixed terminal, such as when using an output plug for connection to the AC power supply 1, a connection destination of the Y-capacitor can be correctly selected. (Effect 3)

[0041] Since the Y-capacitor in the interference suppression filter 15 is connected to the ground-side power supply line according to the first embodiment, the impedance between the ground-side power supply line and the ground of the electrical device can be reduced. Furthermore, since the X-capacitor is connected between the power supply lines, the non-ground-side power supply line is also connected to the Y-capacitor via the X-capacitor. This reduces the impedance between the non-ground-side power supply line and ground. As a result, common-mode interference can be reduced without having to connect the Y-capacitor to all power supply lines. (Effect 4)

[0042] Common-mode interference contains a broad-frequency component, but increasing the capacitance of the Y-capacitor is effective in reducing a low-frequency component. Furthermore, increasing the number of turns in the common-mode choke, changing the core material, or similar modifications are effective. To reduce common-mode interference at a relatively low frequency, increasing the capacitance of the Y-capacitor also increases the leakage current. Therefore, there is an upper limit to the amount of capacitance that can be increased. Moreover, with the conventional interference suppression filter, where the common-mode choke is arranged with an increased number of turns, the cost of the component increases.In the interference suppression filter 15 according to the first embodiment, as described in (Effect 1), the voltage fluctuation between the power supply line and the ground of the electrical device at the frequency of the AC power supply 1 is smaller in the ground-side power supply line than in the non-ground-side power supply line. Therefore, even if the capacitance value of the Y-capacitor is larger than that of the conventional Y-capacitor, the capacitance value can be suppressed so that it lies within the upper limit of the leakage current, and the common-mode interference at a lower frequency than that of the conventional Y-capacitor can be reduced. Furthermore, since the component costs for the common-mode choke and the like can be reduced, the overall cost of the interference suppression filter can also be reduced. (Effect 5)

[0043] Once the connection between the Y-capacitor and the ground of the electrical device is established, the circuit operation is initiated, generating a relatively large disturbance. This allows the amount of common-mode interference generated to be suppressed until the Y-capacitor and the ground of the electrical device are connected.

[0044] The representative embodiment of the interference suppression filter 15 has been described above. The interference suppression filter 15 is applicable not only to single-phase AC power supplies but also to three-phase AC power supplies. A common-mode choke, a capacitor, an overvoltage protection element, a power supply disconnect relay, a fuse, or the like can be inserted into the circuit of the interference suppression filter 15 described above. The connection of the Y-capacitor to the ground of the electrical device can be made via a metal housing or similar component of the electrical device 4. Not only a mechanical relay but also a solid-state relay, a transistor, or the like can be used as a relay for connecting the Y-capacitor to the ground of the electrical device. A latching relay can be used for connecting the Y-capacitor to the ground of the electrical device.In this case, however, all Y-capacitors must be disconnected from the electrical equipment's ground when the power supply is switched on. If the reduction in common-mode interference is sufficient, the capacitance of the Y-capacitor can be made smaller than the capacitance value specified in formula (1). After the ground-side power supply line has been detected, the ground-side power supply line detection circuit 12 can be disconnected from the power supply line and the electrical equipment's ground.

[0045] As described above, the interference suppression filter 15 according to the first embodiment is the interference suppression filter 15 of the electrical device 4, which is connected to the AC power supply 1, comprising the electrode 3, which is connected to the ground of the power supply, and the electrode 2, which is not connected to the ground of the power supply, wherein the interference suppression filter comprises: the power supply line 5, which is connected to electrode 2 and electrode 3; the power supply line 6, which is connected to electrode 2 and electrode 3; the Y-capacitor 7, which is connected to power supply line 5; the Y-capacitor 9, which is connected to power supply line 6; the relay 8, which is connected between the Y-capacitor 7 and the ground of the electrical device; the relay 10, which is connected between the Y-capacitor 9 and the ground of the electrical device;the ground-side power supply line detection circuit 12, which is connected to the power supply line 5 and the power supply line 6 respectively, and which detects a power supply line connected to the electrode 3 from the power supply line 5 and the power supply line 6;and the control circuit 13 to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6, based on a detection result by the ground-side power supply line detection circuit 12, controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device when it is determined that the power supply line connected to electrode 3 is power supply line 5, and controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device when it is determined that the power supply line connected to electrode 3 is power supply line 6.;

[0046] According to the configuration above, the power supply line connected to electrode 3 is detected from power supply line 5 and power supply line 6, and based on the detection result, it is determined whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6, and a control is carried out to create a short circuit between the Y-capacitor connected to the power supply line identified as the power supply line connected to electrode 3 and the ground of the electrical device.Consequently, common-mode interference can be reduced by connecting the power supply ground, the power supply line, the Y-capacitor, and the ground of the electrical equipment. However, since the power supply line not connected to the power supply ground is not connected to the Y-capacitor, no leakage current is generated. Therefore, the power supply line connected to the Y-capacitor can be switched correctly.

[0047] In the interference suppression filter 15 according to the first embodiment, in a case where the capacitance value of the Y-capacitor 7 and the Y-capacitor 9 is C [F], the upper limit of the leakage current in the interference suppression filter 15 is I [A], the angular frequency of the AC power supply is 1 ω [rad / s] and the power supply voltage of the AC power supply is 1 V [V], the capacitance value C [F] of the Y-capacitor 7 and the Y-capacitor 9 each follows the formula (1) described above.

[0048] With the above configuration, it is possible to suppress the leakage current appropriately and at the same time to reduce the common-mode interference appropriately. Second embodiment.

[0049] In the first embodiment, the configuration in which the ground-side power supply line detection circuit 12 detects the ground-side power supply line was described. In a second embodiment, a configuration in which an A / D converter (analog-to-digital converter) detects a ground-side power supply line is described.

[0050] The second embodiment is explained below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0051] Fig. Figure 3 is a block diagram showing a configuration of an electrical device 4 according to the second embodiment. As in Fig. Figure 3 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, an A / D converter 12-1 and an A / D converter 12-2 (first analog-to-digital converter and second analog-to-digital converter). The A / D converter 12-1 has input terminals connected to the power supply line 5 and the ground of the electrical device, and an output terminal connected to the control circuit 13. The A / D converter 12-2 has input terminals connected to the power supply line 6 and the ground of the electrical device, and an output terminal connected to the control circuit 13.

[0052] The ground-side power supply line detection circuit 12 according to the second embodiment detects a voltage V1 between the power supply line 5 and the ground of the electrical device, and detects a voltage V2 between the power supply line 6 and the ground of the electrical device. More precisely, in the second embodiment, the A / D converter 12-1 in the ground-side power supply line detection circuit 12 detects the voltage V1 between the power supply line 5 and the ground of the electrical device, and the A / D converter 12-2 detects the voltage V2 between the power supply line 6 and the ground of the electrical device. The A / D converter 12-1 converts the detected voltage V1 into a digital signal and outputs the digital signal to the control circuit 13. The A / D converter 12-2 converts the detected voltage V2 into a digital signal and outputs the digital signal to the control circuit 13.

[0053] The control circuit 13 according to the second embodiment determines which of the amplitudes of voltage V1 and voltage V2, detected by the ground-side power supply line detection circuit 12, is smaller in order to determine whether the power supply line connected to electrode 3 (ground-side power supply line) is power supply line 5 or power supply line 6. Specifically, in the second embodiment, the control circuit 13 determines which of the amplitudes of voltage V1 detected by A / D converter 12-1 and voltage V2 detected by A / D converter 12-2 is smaller in order to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6.

[0054] If it is determined that the amplitude of voltage V1 is smaller than the amplitude of voltage V2, control circuit 13 activates relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that the amplitude of voltage V2 is smaller than the amplitude of voltage V1, control circuit 13 activates relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0055] The following describes the operation of the interference suppression filter 15 according to the second embodiment with reference to the drawings. Fig. Figure 4 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the second embodiment.

[0056] As in Fig. As shown in Figure 4, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrode 2 and the electrode 3 (step ST10).

[0057] The control circuit 13 then starts operation (step ST11).

[0058] Next, A / D converter 12-1 detects a waveform of the voltage V1 between power supply line 5 and the ground of the electrical device, and A / D converter 12-2 detects a waveform of the voltage V2 between power supply line 6 and the ground of the electrical device (step ST12). A / D converter 12-1 converts the detected voltage V1 into a digital signal and outputs the digital signal to control circuit 13. A / D converter 12-2 converts the detected voltage V2 into a digital signal and outputs the digital signal to control circuit 13.

[0059] Next, the control circuit 13 determines whether or not the amplitude of the voltage V1 detected by the A / D converter 12-1 is smaller than the amplitude of the voltage V2 detected by the A / D converter 12-2 (step ST13).

[0060] If it is determined that the amplitude of the voltage V1 detected by the A / D converter 12-1 is smaller than the amplitude of the voltage V2 detected by the A / D converter 12-2 (JA in step ST13), the control circuit 13 controls the relay 8 to create a short circuit between the Y capacitor 7 and the ground of the electrical device (step ST14).

[0061] If it is determined that the amplitude of the voltage V2 detected by the A / D converter 12-2 is smaller than the amplitude of the voltage V1 detected by the A / D converter 12-1 (NO in step ST13), the control circuit 13 controls the relay 10 to create a short circuit between the Y capacitor 9 and the ground of the electrical device (step ST15).

[0062] As the next step from step ST14 or step ST15, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST16).

[0063] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST17). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0064] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the first embodiment described above. (Effect 1)

[0065] By using the A / D converter for the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented by a simple circuit. (Effect 2)

[0066] By using the A / D converter for the ground-side power supply line detection circuit 12, the time of the zero crossing can be detected based on the waveform obtained from the A / D converter.

[0067] The representative embodiment of the interference suppression filter 15 has been described above. In addition to the configuration of the first embodiment and the configuration of the second embodiment, the following configuration can also be adopted. For example, a capacitor for isolation or similar purposes can be inserted between each A / D converter and the ground of the electrical device. The input unit of the A / D converter can be protected by a resistive voltage divider, an overvoltage protection element, a diode, or the like. A converter integrated into the control circuit 13 can be used as the A / D converter. In the second embodiment, the voltage is detected by the A / D converter. Alternatively, a resistor can be connected to the input unit to detect the current.In this case, the control circuit 13 can determine, based on the detected current, whether the power supply line connected to the electrode 3 is the power supply line 5 or the power supply line 6.

[0068] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the second embodiment detects the voltage V1 between the power supply line 5 and the ground of the electrical device and detects the voltage V2 between the power supply line 6 and the ground of the electrical device, and the control circuit 13 determines whether the power supply line connected to the electrode 3 is the power supply line 5 or the power supply line 6 by determining which is smaller by the amplitude of the voltage V1 and the amplitude of the voltage V2 detected by the ground-side power supply line detection circuit 12, and controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device when it is determined that the amplitude of the voltage V1 is smaller than the amplitude of the voltage V2.and controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device when it is determined that the amplitude of voltage V2 is smaller than the amplitude of voltage V1.

[0069] According to the configuration above, the detected voltage can be used to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched.

[0070] The ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the second embodiment comprises the A / D converter 12-1, which detects a voltage between the power supply line 5 and the ground of the electrical device, and the A / D converter 12-2, which detects a voltage between the power supply line 6 and the ground of the electrical device.

[0071] According to the configuration above, the voltage between the power supply line and the ground of the electrical device can be appropriately measured. Based on this measured voltage, it can then be appropriately determined whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Third embodiment.

[0072] In the first and second embodiments, the point in time at which the relay establishes a short circuit between the Y-capacitor and the ground of the electrical device is not specified. However, a third embodiment describes a configuration in which the relay establishes a short circuit between the Y-capacitor and the ground of the electrical device simultaneously with the point in time at which the voltage between the power supply line and the ground of the electrical device reaches zero (zero crossing time). It should be noted that the third embodiment also includes a description using a noise suppression filter 15.

[0073] If it is determined that the power supply line connected to electrode 3 is power supply line 5, a control circuit 13 according to the third embodiment controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device at a time when the voltage V1 detected by a ground-side power supply line detection circuit 12 reaches zero. If it is determined that the power supply line connected to electrode 3 is power supply line 6, the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time when the voltage V2 detected by the ground-side power supply line detection circuit 12 reaches zero.

[0074] More precisely, in the third embodiment, if it is determined that the power supply line connected to electrode 3 is power supply line 5, the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device at a time when the voltage V1 detected by the A / D converter 12-1 reaches zero. If it is determined that the power supply line connected to electrode 3 is power supply line 6, the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time when the voltage V2 detected by the A / D converter 12-2 reaches zero.

[0075] The following describes a specific example of a power supply line switching method using the interference suppression filter 15 according to the third embodiment. This specific example describes a case in which the control circuit 13 determines that the power supply line connected to the electrode 3 (ground-side power supply) is the power supply line 6 in the interference suppression filter 15 according to the second embodiment. It should be noted that the interference suppression filter 15 according to the first embodiment can also be used as long as zero-crossing detection is possible.

[0076] For comparison, a configuration is first described in which the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time that differs from the time at which the voltage V2 detected by the A / D converter 12-2 reaches zero. Fig. Figure 5 is a graph illustrating the voltage V2 detected by the A / D converter 12-2, the operation of the relay 10 and the current flowing through the Y-capacitor 9 in the configuration.

[0077] As in the graph above from Fig. As shown in Figure 5, due to parasitic inductance or similar of the power supply line 6, a small voltage is also generated between the power supply line 6 and the ground of the electrical device. As shown in the middle graph of Fig. As shown in Figure 5, the relay 10 creates a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time when the voltage V2 of the power supply line 6 reaches a maximum. As shown in the lower graph of Fig. As shown in 5, in this case a voltage is immediately applied to the Y-capacitor 9, and a current flows quickly.

[0078] Next, a configuration is described in which the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time when the voltage V2 detected by the ground-side power supply line detection circuit 12 reaches zero. Fig. Figure 6 is a graph showing the voltage V2 detected by the ground-side power supply line detection circuit 12, the operation of the relay 10 and the current flowing through the Y-capacitor 9 in the configuration.

[0079] As in the upper and middle graphs of Fig. As shown in Figure 6, the relay 10 creates a short circuit between the Y-capacitor 9 and the ground of the electrical device at a time when the voltage V2 of the power supply line 6 reaches zero. As shown in the lower part of Fig. As shown in Figure 6, in this case the voltage applied to the Y-capacitor 9 becomes gentle, and the current is reduced.

[0080] As described above, the third embodiment describes a configuration in which the relay 10 creates a short circuit between the Y-capacitor 9 and the ground of the electrical device in accordance with the zero-crossing time obtained from the voltage waveform and the like from the A / D converter 12-2. It should be noted that the same applies in a case where the power supply line 5 is a ground-side power supply line.

[0081] The following effect can be achieved by operating the interference suppression filter 15 according to the third embodiment described above. (Effect 1)

[0082] At the moment when the voltage of the power supply line reaches zero, the relay corresponding to the power supply line creates a short circuit between the Y-capacitor and the ground of the electrical device, so that the current does not flow quickly to the Y-capacitor and the generation of interference can be prevented.

[0083] The representative embodiment of the interference suppression filter 15 has been explained above. In addition to the configuration of the first embodiment and the configuration of the second embodiment, the following configuration can also be adopted. Taking into account the delay of the A / D converter, the control circuit, the transmission line, and the like, the time at which the relay creates a short circuit between the Y-capacitor and the ground of the electrical device can be before or after the time at which the voltage of the power supply line reaches zero. Alternatively, a detection circuit can be provided that detects the time at which the voltage of the power supply line reaches zero, and the relay can create a short circuit between the Y-capacitor and the ground of the electrical device depending on a signal from the detection circuit.

[0084] If, as described above, it is determined that the power supply line connected to electrode 3 is power supply line 5, the control circuit 13 in the interference suppression filter 15 according to the third embodiment controls the relay 8 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device at the time when the voltage V1 detected by the ground-side power supply line detection circuit 12 reaches zero, and if it is determined that the power supply line connected to electrode 3 is power supply line 6, the relay 10 creates a short circuit between the Y-capacitor 7 and the ground of the electrical device at the time when the voltage V2 detected by the ground-side power supply line detection circuit 12 reaches zero.

[0085] According to the configuration above, the relay corresponding to the power supply line creates a short circuit between the Y-capacitor and the ground of the electrical device at the moment when the voltage of the power supply line reaches zero, so that the current does not flow quickly to the Y-capacitor and the generation of interference can be prevented. Fourth embodiment.

[0086] In the first embodiment, the configuration in which the ground-side power supply line detection circuit 12 detects the ground-side power supply line was explained. In a fourth embodiment, a configuration in which a comparator detects a ground-side power supply line is described.

[0087] The fourth embodiment is explained below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0088] Fig. Figure 7 is a block diagram showing a configuration of an electrical device 4 according to the fourth embodiment. As in Fig. Figure 7 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is included in the electrical device 4, a comparator 12-3 and a comparator 12-4 (first comparator and second comparator) and a DC power supply 12-5.

[0089] Comparator 12-3 has one input terminal connected to both power supply line 5 and DC supply 12-5, one output terminal connected to control circuit 13, and one ground terminal connected to signal ground SG. Comparator 12-4 has one input terminal connected to both power supply line 6 and DC supply 12-5, one output terminal connected to control circuit 13, and one ground terminal connected to signal ground SG. A terminal of DC supply 12-5 not connected to comparator 12-3 or comparator 12-4 is connected to signal ground SG. Signal ground SG is connected to the ground of the electrical device.

[0090] The ground-side power supply line detection circuit 12 according to the fourth embodiment detects a result of the comparison of the voltage V1 between the power supply line 5 and the signal ground SG with a voltage Vref between the DC supply 12-5 and the signal ground SG, and detects a result of the comparison of the voltage V2 between the power supply line 6 and the signal ground SG with the voltage Vref between the DC supply 12-5 and the signal ground SG.Specifically, in the fourth embodiment, the comparator 12-3 in the ground-side power supply line detection circuit 12 detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the voltage Vref between the DC power supply 12-5 and the signal ground SG, and the comparator 12-4 detects the result of comparing the voltage V2 between the power supply line 6 and the signal ground SG with the voltage Vref between the DC power supply 12-5 and the signal ground SG. Vref is set to a value that is smaller than the amplitude of the power supply voltage of the AC power supply 1.

[0091] The comparator 12-3 outputs a signal 1 to the control circuit 13 when the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the voltage Vref between the DC power supply 12-5 and the signal ground SG. The comparator 12-4 outputs a signal 2 to the control circuit 13 when the voltage V2 between the power supply line 6 and the signal ground SG is equal to or greater than the voltage Vref between the DC power supply 12-5 and the signal ground SG.

[0092] The control circuit 13 according to the fourth embodiment determines, based on the comparison result between the voltage V1 and the voltage Vref detected by the ground-side power supply line detection circuit 12, and the comparison result between the voltage V2 and the voltage Vref, whether the power supply line (ground-side power supply line) connected to the electrode 3 is power supply line 5 or power supply line 6. More precisely, in the fourth embodiment, the control circuit 13 makes the following determination based on the presence or absence of the detection (output) of signal 1 by comparator 12-3, the presence or absence of the detection (output) of signal 2 by comparator 12-4, and the detection (output) times of signal 1 and signal 2 by comparator 12-3 and comparator 12-4 during a specific period.

[0093] (Condition 1) (a) no detection of signal 1 by comparator 12-3 and detection of signal 2 by comparator 12-4; or (b) Acquisition of signal 1 by comparator 12-3 and acquisition of signal 2 by comparator 12-4, and the acquisition time of signal 2 is longer.

[0094] If (condition 1) is met, the control circuit 13 determines that the power supply line 5 is a power supply line connected to the electrode 3.

[0095] (Condition 2) (a) Detection of signal 1 from comparator 12-3 and no detection of signal 2 from comparator 12-4, or (b) Detection of signal 1 by comparator 12-3 and detection of signal 2 by comparator 12-4, and the detection time of signal 1 is longer.

[0096] If (condition 2) is met, the control circuit 13 determines that the power supply line 6 is a power supply line connected to the electrode 3.

[0097] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0098] The operation of the interference suppression filter 15 according to the fourth embodiment will now be described with reference to the drawings. Fig. Figure 8 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the fourth embodiment.

[0099] As in Fig. As shown in Figure 8, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST20).

[0100] The control circuit 13 then starts operation (step ST21).

[0101] Next, comparator 12-3 detects the result of comparing the voltage V1 between power supply line 5 and signal ground SG with the voltage Vref between DC supply 12-5 and signal ground SG. Then, comparator 12-4 detects the result of comparing the voltage V2 between power supply line 6 and signal ground SG with the voltage Vref between DC supply 12-5 and signal ground SG (step ST22). Comparator 12-3 outputs a signal 1 to control circuit 13 if the voltage V1 between power supply line 5 and signal ground SG is equal to or greater than the voltage Vref between DC supply 12-5 and signal ground SG.The comparator 12-4 outputs the signal 2 to the control circuit 13 when the voltage V1 between the power supply line 6 and the signal ground SG is equal to or greater than the voltage Vref between the DC supply 12-5 and the signal ground SG.

[0102] Next, the control circuit 13 determines which of the conditions (condition 1) and (condition 2) are met, based on the presence or absence of the detection of signal 1 by the comparator 12-3, the presence or absence of the detection of signal 2 by the comparator 12-4, and the detection times of signal 1 and signal 2 by the comparator 12-3 and the comparator 12-4 during a certain period of time (step ST23).

[0103] If it is determined that (condition 1) is satisfied (condition 1 in step ST23), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST24).

[0104] If it is determined that (condition 2) is satisfied (condition 2 in step ST23), the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device (step ST25).

[0105] As the next step from step ST24 or step ST25, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST26).

[0106] Next, the main circuit 14 of the electrical device is disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST27). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0107] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the fourth embodiment described above. (Effect 1)

[0108] By using a comparator for the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented using a cost-effective component. (Effect 2)

[0109] By using the comparator for the ground-side power supply line detection circuit 12, the comparator detects the impulse disturbance only for a short time, even when the impulse disturbance is applied to the input of the comparator, and thus the comparison result between the voltage V1 or the voltage V2 and the voltage Vref is hardly affected.

[0110] The representative embodiment of the interference suppression filter 15 has been described above. In addition to the configurations of the first to third embodiments, the following configuration can also be adopted. For example, a capacitor or the like can be inserted between the signal ground SG and the ground of the electrical device to achieve isolation or the like. The input unit of the comparator can be protected by resistor voltage division, an overvoltage protection element, a diode, or the like. The comparator embedded in the control circuit 13 can be used. In the fourth embodiment, an example was described in which voltages are compared by a comparator, but a method for comparing currents by connecting a resistor to an input unit can also be used.For example, an optocoupler, a pulse transformer or the like can be inserted between the output unit of the comparator and the electrical device 13 to achieve isolation or the like.

[0111] In the fourth embodiment, the ground-side power supply line detection circuit 12 is equipped with two comparators. However, only one comparator can also be used, and whether the one comparator is connected to the power supply line 5 or the power supply line 6 can be switched by a switch or the like. If both signal 1 and signal 2 are detected and the detection times are the same, the control circuit 13 can short-circuit only a specific relay.

[0112] In the fourth embodiment, an additional Y-capacitor is inserted into each power supply line. Alternatively, two (or more) Y-capacitors can be inserted into each power supply line. In this case, a relay can be inserted into all Y-capacitors, or a common relay can be inserted into the Y-capacitors connected to the same power supply line.

[0113] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15, according to the fourth embodiment, compares the first voltage V1 between the power supply line 5 and the ground of the electrical equipment with the threshold voltage Vref, and outputs a first signal if the first voltage V1 is equal to or greater than the threshold voltage Vref, and compares the second voltage V2 between the power supply line 6 and the ground of the electrical equipment with the threshold voltage Vref, and outputs a second signal if the second voltage V2 is equal to or greater than the threshold voltage Vref, and the control circuit 13, if the first signal is not output by the ground-side power supply line detection circuit 12 and the second signal is output by the ground-side power supply line detection circuit 12 during a certain period of time,or if the first signal and the second signal are output by the ground-side power supply line detection circuit 12 and the output time of the second signal is longer than the output time of the first signal during a certain period, the relay 8 is controlled to create a short circuit between the Y-capacitor 7 and the ground of the electrical device, and if the first signal is output by the ground-side power supply line detection circuit 12 and the second signal is not output by the ground-side power supply line detection circuit 12 during a certain period, or if the first signal and the second signal are output by the ground-side power supply line detection circuit 12 and the output time of the first signal is longer than the output time of the second signal during a certain period, the relay 10 is controlled.to create a short circuit between the Y-capacitor 9 and the ground of the electrical device.

[0114] According to the configuration above, the detected voltage can be used to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched.

[0115] The ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the fourth embodiment comprises the comparator 12-3, the comparator 12-4 and the DC power supply 12-5; the comparator 12-3 comprises an input terminal, each connected to the power supply line 5 and a positive terminal of the DC power supply 12-5, and an output terminal, which is connected to the control circuit 13, and a ground terminal, which is connected to the ground of the electrical device; the comparator 12-4 comprises an input terminal, each connected to the power supply line 6 and a positive terminal of the DC power supply 12-5, an output terminal, which is connected to the control circuit 13, and a ground terminal, which is connected to the ground of the electrical device; the DC power supply 12-5 comprises a positive terminal,The comparator 12-3 is connected to the input terminal of comparator 12-3 and the input terminal of comparator 12-4, and has a negative terminal connected to the ground of the electrical device. Comparator 12-3 compares the first voltage V1 between power supply line 5 and the ground of the electrical device with a threshold voltage Vref output by DC power supply 12-5 and outputs the first signal from the output terminal if the first voltage V1 is equal to or greater than the threshold voltage Vref. Comparator 12-4 compares the second voltage V2 between power supply line 6 and the ground of the electrical device with a threshold voltage Vref output by DC power supply 12-5 and outputs the second signal from the output terminal if the second voltage V2 is equal to or greater than the threshold voltage Vref.

[0116] According to the configuration above, the voltage between the power supply line and the ground of the electrical device can be appropriately measured. Based on this measured voltage, it can then be appropriately determined whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Fifth embodiment.

[0117] In the first embodiment, the configuration in which the ground-side power supply line detection circuit 12 detects the ground-side power supply line was described. In a fifth embodiment, a configuration in which a transistor detects a ground-side power supply line is described.

[0118] The fifth embodiment is described below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0119] Fig. Figure 9 is a block diagram showing a configuration of an electrical device 4 according to the fifth embodiment. As in Fig. Figure 9 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, a transistor 12-7 and a transistor 12-8 (first transistor and second transistor), a resistor 12-9, a resistor 12-10 and a DC power supply 12-11. It should be noted that in the fifth embodiment, as an example, a case is described in which the transistor 12-7 and the transistor 12-8 are NPN transistors.

[0120] Transistor 12-7 has a base terminal connected to power supply line 5, a collector terminal connected to control circuit 13 and resistor 12-9, and an emitter terminal connected to signal ground SG. The terminal of resistor 12-9 on the side not connected to transistor 12-7 is connected to DC supply 12-11. Transistor 12-8 has a base terminal connected to power supply line 6, a collector terminal connected to control circuit 13 and resistor 12-10, and an emitter terminal connected to signal ground SG. The terminal of resistor 12-10 on the side not connected to transistor 12-8 is connected to DC supply 12-11.The DC power supply terminal 12-11 on the side not connected to transistors 12-7 and 12-8 is connected to signal ground SG. Signal ground SG is connected to the ground of the electrical device.

[0121] The ground-side power supply line detection circuit 12 according to the fifth embodiment detects a result of the comparison of the voltage V1 applied between the power supply line 5 and the signal ground SG (between the base and emitter of transistor 12-7) with the threshold voltage Vref of transistor 12-7. Furthermore, the ground-side power supply line detection circuit 12 according to the fifth embodiment detects a result of the comparison of the voltage V2 applied between the power supply line 6 and the signal ground SG (between the base and emitter of transistor 12-8) with the threshold voltage Vref of transistor 12-8.

[0122] Note that if the voltage V1 applied between power supply line 5 and signal ground SG is less than the threshold voltage Vref of transistor 12-7, transistor 12-7 switches to an OFF state (a state in which hardly any current flows between collector and emitter). If the voltage V1 applied between power supply line 5 and signal ground SG is equal to or greater than the threshold voltage Vref of transistor 12-7, transistor 12-7 switches to an ON state (a state in which a small current flows between collector and emitter). The threshold voltage Vref of transistor 12-7 is set to a value that is less than the amplitude of the power supply voltage of AC supply 1.

[0123] Similarly, if the voltage V2 applied between power supply line 6 and signal ground SG is less than the threshold voltage Vref of transistor 12-8, transistor 12-8 switches to an OFF state (a state in which hardly any current flows between collector and emitter). If the voltage V2 applied between power supply line 6 and signal ground SG is equal to or greater than the threshold voltage Vref of transistor 12-8, transistor 12-8 switches to an ON state (a state in which a small current flows between collector and emitter). The threshold voltage Vref of transistor 12-8 is set to a value that is less than the amplitude of the power supply voltage of AC supply 1.

[0124] Transistor 12-7 outputs signal 1 to control circuit 13 when the voltage V1 is equal to or greater than the threshold voltage Vref. Transistor 12-8 outputs signal 2 to control circuit 13 when the voltage V2 is equal to or greater than the threshold voltage Vref.

[0125] The control circuit 13 according to the fifth embodiment determines, based on the comparison between the voltage V1, which is detected by the ground-side power supply line detection circuit 12, and the voltage Vref, and the comparison between the voltage V2 and the voltage Vref, whether the power supply line (ground-side power supply line) connected to the electrode 3 is power supply line 5 or power supply line 6. More precisely, in the fifth embodiment, the control circuit 13 makes the following determination based on the presence or absence of the detection (output) of signal 1 by transistor 12-7, the presence or absence of the detection (output) of signal 2 by transistor 12-8, and the detection (output) times of signal 1 and signal 2 by transistor 12-7 and transistor 12-8 during a specific period.

[0126] (Condition 1) (a) no detection of signal 1 from transistor 12-7 and detection of signal 2 from transistor 12-8; or (b) Detection of signal 1 from transistor 12-7 and detection of signal 2 from transistor 12-8, and the detection time of signal 2 is longer.

[0127] If (condition 1) is met, the control circuit 13 determines that the power supply line 5 is a power supply line connected to the electrode 3.

[0128] (Condition 2) (a) no detection of signal 1 from transistor 12-7 and detection of signal 2 from transistor 12-8; or (b) Detection of signal 1 from transistor 12-7 and detection of signal 2 from transistor 12-8, and the detection time of signal 1 is longer.

[0129] If (condition 2) is met, the control circuit 13 determines that the power supply line 6 is a power supply line connected to the electrode 3.

[0130] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0131] The operation of the interference suppression filter 15 according to the fifth embodiment will now be described with reference to the drawings. Fig. Figure 10 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the fifth embodiment.

[0132] As in Fig. As shown in Figure 10, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST30).

[0133] The control circuit 13 then starts operation (step ST31).

[0134] Transistor 12-7 then detects the result of comparing the voltage V1 between power supply line 5 and signal ground SG (between base and emitter) with the threshold voltage Vref. Transistor 12-8 detects the result of comparing the voltage V2 between power supply line 6 and signal ground SG (between base and emitter) with the threshold voltage Vref (step ST32). Transistor 12-7 outputs signal 1 to control circuit 13 if the voltage V1 between power supply line 5 and signal ground SG is equal to or greater than the threshold voltage Vref. Transistor 12-8 outputs signal 2 to control circuit 13 if the voltage V2 between power supply line 6 and signal ground SG is equal to or greater than the threshold voltage Vref.

[0135] Next, the control circuit 13 determines which of the conditions (condition 1) and (condition 2) are met, based on the presence or absence of the detection of signal 1 by transistor 12-7, the presence or absence of the detection of signal 2 by transistor 12-8, and the detection times of signal 1 and signal 2 by transistor 12-7 and transistor 12-8 during a certain period of time (step ST33).

[0136] If it is determined that (condition 1) is satisfied (condition 1 in step ST33), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST34).

[0137] If it is determined that (condition 2) is satisfied (condition 2 in step ST33), the control circuit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device (step ST35).

[0138] As the next step from step ST34 or step ST35, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST36).

[0139] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST37). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0140] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the fifth embodiment described above. (Effect 1)

[0141] By using a transistor for the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented using a cost-effective component. (Effect 2)

[0142] By using the transistor for the ground-side power supply line detection circuit (12), the transistor detects the impulse disturbance only for a short time, even if the impulse disturbance is applied to the input of the transistor, so that the comparison result between the voltage V1 or the voltage V2 and the threshold voltage Vref is hardly affected.

[0143] The representative embodiment of the interference suppression filter 15 has been explained above. In addition to the configurations of the first through fourth embodiments, the following configuration can also be adopted. The input unit of the transistor can be protected, for example, by current limiting via a resistor, resistor voltage division, an overvoltage protection element, a diode, or the like. A resistor can be connected in series with the base terminal, or a resistor can be inserted between the base and emitter. In the fifth embodiment, a case is described as an example in which the transistor is an NPN transistor. However, the ground-side supply line detection circuit 12 can also be configured using a PNP transistor, provided that similar operation can be achieved.Furthermore, a field-effect transistor or the like can be used instead of the transistor, provided that the same function can be achieved. In the fifth embodiment, an example was described in which voltages are compared using a transistor, but a method can also be used in which a resistor is connected to an input unit to compare currents. For example, an optocoupler, a pulse transformer, or the like can be inserted between the output unit of the transistor and the control circuit 13 to achieve isolation or the like. In the fifth embodiment, the ground-side power supply line detection circuit 12 is equipped with two transistors.However, it is also possible to use only one transistor, and whether the one transistor is connected to the power supply line 5 or the power supply line 6 can be switched by a switch or the like.

[0144] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the fifth embodiment comprises transistor 12-7, transistor 12-8, resistor 12-9, resistor 12-10, and the DC power supply 12-11. Transistor 12-7 comprises a base terminal connected to the power supply line 5, a collector terminal connected to the control circuit 13 and a terminal of resistor 12-9, and an emitter terminal connected to the ground of the electrical device. Transistor 12-8 comprises a base terminal connected to the power supply line 6, a collector terminal connected to the control circuit 13 and a terminal of resistor 12-10, and an emitter terminal connected to the ground of the electrical device. Transistor 12-9 comprises a terminalthe collector terminal of transistor 12-7, and the other terminal connected to the positive terminal of the DC supply 12-11, and resistor 12-10 includes one terminal connected to the collector terminal of transistor 12-8, and the other terminal connected to the positive terminal of the DC supply 12-11, the DC supply 12-11 includes the positive terminal connected to the other terminal of resistor 12-9, and the other terminal of resistor 12-10, and the negative terminal connected to the ground of the electrical device, transistor 12-7 compares the first voltage V1 applied between the base terminal and the emitter terminal with the threshold voltage Vref of transistor 12-7, and outputs the first signal from the collector terminal,If the first voltage V1 is equal to or greater than the threshold voltage Vref of transistor 12-7, and transistor 12-8 compares the second voltage V2 applied between the base terminal and the emitter terminal with the threshold voltage Vref of transistor 12-8, and outputs the second signal from the collector terminal if the first voltage V2 is equal to or greater than the threshold voltage Vref of transistor 12-8.

[0145] According to the configuration above, the voltage between the power supply line and the ground of the electrical device can be appropriately measured. Based on this measured voltage, it can then be appropriately determined whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Sixth embodiment.

[0146] In the first embodiment, the configuration in which the ground-side power supply line detection circuit 12 detects the ground-side power supply line was explained. In a sixth embodiment, a configuration in which an optocoupler detects a ground-side power supply line is described.

[0147] The sixth embodiment is described below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0148] Fig. Figure 11 is a block diagram showing a configuration of an electrical device 4 according to the sixth embodiment. As in Fig. Figure 11 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, an optocoupler 12-12 and an optocoupler 12-13 (first optocoupler and second optocoupler). The optocoupler 12-12 has input terminals connected to the power supply line 5 and the signal ground SG, and an output terminal connected to the control circuit 13. The optocoupler 12-13 has input terminals connected to the power supply line 6 and the signal ground SG, and an output terminal connected to the control circuit 13. The signal ground SG is connected to the ground of the electrical device.

[0149] The ground-side power supply line detection circuit 12 according to the sixth embodiment detects a result of the comparison of the voltage V1 between the power supply line 5 and the signal ground SG with the threshold voltage Vref of the optocoupler 12-12, and detects a result of the comparison of the voltage V2 between the power supply line 6 and the signal ground SG with the threshold voltage Vref of the optocoupler 12-13. Vref is set to a value that is smaller than the amplitude of the power supply voltage of the AC power supply 1.

[0150] The optocoupler 12-12 outputs a signal 1 to the control circuit 13 when the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref. The optocoupler 12-13 outputs a signal 2 to the control circuit 13 when the voltage V2 between the power supply line 6 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0151] The control circuit 13 according to the sixth embodiment determines, based on the comparison result between the voltage V1, which is detected by the ground-side power supply line detection circuit 12, and the threshold voltage Vref, and the comparison result between the voltage V2 and the threshold voltage Vref, whether the power supply line (ground-side power supply line) connected to the electrode 3 is the power supply line 5 or the power supply line 6.More precisely, in the sixth embodiment, the control circuit 13 makes the following determination based on the presence or absence of the detection (output) of signal 1 by the optocoupler 12-12, the presence or absence of the detection (output) of signal 2 by the optocoupler 12-13, and the detection times (output) of signal 1 and signal 2 by the optocoupler 12-12 and the optocoupler 12-13 during a certain period of time.

[0152] (Condition 1) (a) no detection of signal 1 from optocoupler 12-12 and detection of signal 2 from optocoupler 12-13; or (b) Detection of signal 1 from optocoupler 12-12 and detection of signal 2 from optocoupler 12-13, and the detection time of signal 2 is longer.

[0153] If (condition 1) is met, the control circuit 13 determines that the power supply line 5 is a power supply line connected to the electrode 3.

[0154] (Condition 2) (a) no detection of signal 1 from optocoupler 12-12 and detection of signal 2 from optocoupler 12-13; or (b) Detection of signal 1 from optocoupler 12-12 and detection of signal 2 from optocoupler 12-13, and the detection time of signal 1 is longer.

[0155] If (condition 2) is met, the control circuit 13 determines that the power supply line 6 is a power supply line connected to the electrode 3.

[0156] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0157] The following describes the operation of the interference suppression filter 15 according to the sixth embodiment with reference to the drawings. Fig. Figure 12 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the sixth embodiment.

[0158] As in Fig. As shown in Figure 12, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST40).

[0159] The control circuit 13 then starts operation (step ST41).

[0160] The optocoupler 12-12 then detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the threshold voltage Vref. The optocoupler 12-13 detects the result of comparing the voltage V2 between the power supply line 6 and the signal ground SG with the threshold voltage Vref (step ST42). The optocoupler 12-12 outputs a signal 1 to the control circuit 13 if the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref. The optocoupler 12-13 outputs signal 2 to the control circuit 13 if the voltage V2 between the power supply line 6 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0161] Next, the control circuit 13, which is satisfied by the above-explained (condition 1) and (condition 2), determines, on the basis of the presence or absence of the detection (output) of signal 1 by the optocoupler 12-12, the presence or absence of the detection of signal 2 by the optocoupler 12-13 and the detection (output) times of signal 1 and signal 2 by the optocoupler 12-12 and the optocoupler 12-13 during a certain period of time (step ST43).

[0162] If it is determined that (condition 1) is satisfied (condition 1 in step ST43), the control unit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST44).

[0163] If it is determined that (condition 2) is satisfied (condition 2 in step ST43), the control unit 13 controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device (step ST45).

[0164] As the next step from step ST44 or step ST45, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST46).

[0165] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST47). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0166] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the sixth embodiment described above. (Effect 1)

[0167] By using an optocoupler for the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented using a cost-effective component. (Effect 2)

[0168] By using an optocoupler for the ground-side power supply line detection circuit 12, the optocoupler detects the impulse disturbance only for a short time, so that the comparison result between the voltage V1 or V2 and the threshold voltage Vref is hardly affected, even when the impulse disturbance is applied to the input of the optocoupler. (Effect 3)

[0169] The use of an optocoupler for the ground-side power supply line detection circuit 12 improves the insulation.

[0170] The representative embodiment of the interference suppression filter 15 has been described above. In addition to the configurations of the first to fifth embodiments, the following configuration can also be adopted. The input unit of the optocoupler can, for example, be protected by a resistive voltage divider, an overvoltage protection element, a diode, or the like. To prevent the optocoupler from illicitly lighting up, a resistor can be connected between the input terminals of the optocoupler. In the sixth embodiment, the voltage is compared by the optocoupler. Alternatively, the current can be compared by connecting a resistor to the input unit. In the sixth embodiment, the ground-side power supply line detection circuit 12 also includes two optocouplers.However, only one optocoupler can be used, and a switch or the like can be used to switch the power supply line 5 and the power supply line 6 to which the optocoupler is connected.

[0171] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the sixth embodiment comprises: the optocoupler 12-12 with an input terminal that is connected to the power supply line 5 and the ground of the electrical device, respectively, and an output terminal that is connected to the control circuit 13;and the optocoupler 12-13, comprising an input terminal, each connected to the power supply line 6 and the ground of the electrical device, and an output terminal, which is connected to the control circuit 13, the optocoupler 12-12 compares the first voltage V1 between the power supply line 5 and the ground of the electrical device with the threshold voltage Vref of the optocoupler 12-12, and outputs the first signal from the output terminal if the first voltage V1 is equal to or greater than the threshold voltage Vref of the optocoupler 12-12, and the optocoupler 12-13 compares the second voltage V2 between the power supply line 6 and the ground of the electrical device with the threshold voltage Vref of the optocoupler 12-13, and outputs the second signal from the output terminal if the second voltage V2 is equal to or greater than the threshold voltage Vref of the optocoupler 12-13.;

[0172] According to the configuration above, the voltage between the power supply line and the ground of the electrical device can be appropriately measured. Based on this measured voltage, it can then be appropriately determined whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Seventh embodiment.

[0173] In the second to sixth embodiments, the configuration was described in which the same circuit is inserted into both the power supply line 5 and the power supply line 6 in the ground-side power supply line detection circuit 12. A seventh embodiment describes a configuration in which a circuit is inserted only into the power supply line 5.

[0174] The seventh embodiment is described below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0175] Fig. Figure 13 is a block diagram showing a configuration of an electrical device 4 according to the seventh embodiment. As in Fig. Figure 13 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, comprising a detection circuit 12-14. The detection circuit 12-14 is the A / D converter 12-1 according to the second embodiment. The detection circuit 12-14 comprises an input terminal connected to the power supply line 5, a ground terminal connected to the signal ground SG, and an output terminal connected to the control circuit 13. The signal ground SG is connected to the ground of the electrical device.

[0176] The ground-side power supply line detection circuit 12 according to the seventh embodiment detects the voltage V1 between the power supply line 5 and the signal ground SG. More precisely, in the seventh embodiment, the detection circuit 12-14 (A / D converter 12-1) in the ground-side power supply line detection circuit 12 detects the voltage V1 between the power supply line 5 and the signal ground SG. The detection circuit 12-14 converts the detected voltage V1 into a digital signal and outputs the digital signal to the control circuit 13.

[0177] The control circuit 13 according to the seventh embodiment determines whether the power supply line (ground-side power supply line) connected to the electrode 3 is power supply line 5 or power supply line 6, based on the amplitude of the voltage V1 detected by the ground-side power supply line detection circuit 12. More precisely, in the seventh embodiment, the control circuit 13 compares the voltage V1 detected by the detection circuit 12-14 (A / D converter 12-1) with the threshold voltage Vref and determines that the signal 1 is output by the detection circuit 12-14 if the voltage V1 is equal to or greater than the threshold voltage Vref. Vref is set to half the amplitude of the power supply voltage of the AC power supply 1.

[0178] If it is determined that signal 1 is not output by the detection circuit 12-14 within a certain period of time, the control circuit 13 determines that power supply line 5 is a power supply line connected to electrode 3. If it is determined that signal 1 is output by the detection circuit 12-14 within a certain period of time, the control circuit 13 determines that power supply line 6 is a power supply line connected to electrode 3.

[0179] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0180] The following describes the operation of the interference suppression filter 15 according to the seventh embodiment with reference to the drawings. Fig. Figure 14 is a flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the seventh embodiment.

[0181] As in Fig. As shown in Figure 14, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST50).

[0182] The control circuit 13 then starts operation (step ST51).

[0183] The sensing circuit 12-14 (A / D converter 12-1) then detects a waveform of the voltage V1 between the power supply line 5 and the ground of the electrical device (step ST52). The A / D converter 12-1 converts the detected voltage V1 into a digital signal and outputs the digital signal to the control circuit 13.

[0184] The control circuit 13 then determines whether signal 1 was output by the detection circuit 12-14 within a specific time period (step ST53). More precisely, the control circuit 13 compares the voltage V1 detected by the detection circuit 12-14 within a specific time period with the threshold voltage Vref and determines that signal 1 is output by the detection circuit 12-14 if the voltage V1 is equal to or greater than the threshold voltage Vref.

[0185] If it is determined that signal 1 was not output by the detection circuit 12-14 within a certain time period (NO in step ST53), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST54).

[0186] If it is determined that signal 1 was output by the detection circuit 12-14 within a certain time period (JA in step ST53), the control circuit 13 controls the relay 10 to create a short circuit between the Y capacitor 9 and the ground of the electrical device (step ST55).

[0187] As the next step from step ST54 or step ST55, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST56).

[0188] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST57). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0189] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the seventh embodiment described above. (Effect 1)

[0190] By providing only one detection circuit in the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented cost-effectively.

[0191] The representative embodiment of the interference suppression filter 15 has been explained above. In addition to the configurations of the first through sixth embodiments, the following configuration can also be adopted. The input unit of the detection circuit can, for example, be protected by a resistive voltage divider, an overvoltage protection element, a diode, or the like. In the seventh embodiment, an example was described in which the voltages in the detection circuit are compared, but a method of connecting a resistor to the input unit and comparing the currents can also be used.The seventh embodiment describes an example where Vref is set to half the amplitude of the power supply voltage of AC power supply 1; however, other values ​​can also be used, provided that Vref is equal to or less than the amplitude of the power supply voltage of AC power supply 1. In the seventh embodiment, the detection circuit is connected only to the power supply line 5. The detection circuit can also be connected only to the power supply line 6.

[0192] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the seventh embodiment comprises the detection circuit 12-14 (analog-to-digital converter 12-1), comprising an input terminal connected to the power supply line 5, a ground terminal connected to the ground of the electrical device, and an output terminal connected to the control circuit 13, and detects the first voltage V1 between the power supply line 5 and the ground of the electrical device, the detection circuit 12-14 converts the detected first voltage V1 into a digital signal and outputs the digital signal to the control circuit 13, and the control circuit 13 compares the first voltage V1 detected by the detection circuit 12-14 with the threshold voltage Vref within the specified time period, and the relay 8 controlsto cause a short circuit between the Y-capacitor 7 and the ground of the electrical device if the first voltage V1 does not reach or exceed the threshold voltage Vref within the specified time period, and controls the relay 10 to cause a short circuit between the Y-capacitor 9 and the ground of the electrical device if the first voltage V1 reaches or exceeds the threshold voltage Vref within the specified time period.

[0193] According to the configuration above, the detected voltage can be used to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Eighth embodiment.

[0194] In the second to sixth embodiments, the configuration was described in which the same circuit is inserted into both the power supply line 5 and the power supply line 6 in the ground-side power supply line detection circuit 12. An eighth embodiment describes a configuration in which a circuit is inserted only into the power supply line 5.

[0195] The eighth embodiment is described below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0196] A block diagram representing a configuration of an electrical device 4 according to the eighth embodiment is identical to the one shown in Fig. 13. As in Fig. Figure 13 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, comprising a detection circuit 12-14. The detection circuit 12-14 is the comparator 12-3 and the DC power supply 12-5 in the fourth embodiment. The detection circuit 12-14 has an input terminal connected to the power supply line 5, a ground terminal connected to the DC power supply 12-5, and an output terminal connected to the control circuit 13. A terminal of the DC power supply 12-5, which is not connected to the comparator 12-3, is connected to the signal ground SG. The signal ground SG is connected to the ground of the electrical device.

[0197] The ground-side power supply line detection circuit 12, according to the eighth embodiment, detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the voltage Vref between the DC power supply 12-5 and the signal ground SG. More precisely, in the eighth embodiment, the detection circuit 12-14 in the ground-side power supply line detection circuit 12 detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the voltage Vref between the DC power supply 12-5 and the signal ground SG. Vref is set to a value that is smaller than the amplitude of the power supply voltage of the AC power supply 1. In the eighth embodiment, the voltage Vref between the DC power supply 12-5 and the signal ground SG is also referred to as the threshold voltage.

[0198] The detection circuit 12-14 outputs the signal 1 to the control circuit 13 when the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0199] According to the eighth embodiment, the control circuit 13 determines, based on the comparison between the voltage V1 detected by the ground-side power supply line detection circuit 12 and the threshold voltage Vref, whether the power supply line (ground-side power supply line) connected to electrode 3 is power supply line 5 or power supply line 6. More precisely, in the eighth embodiment, if signal 1 is not detected by the detection circuit 12-14 within a certain period of time, the control circuit 13 determines that power supply line 5 is a power supply line connected to electrode 3. If signal 1 is detected by the detection circuit 12-14 within a certain period of time, the control circuit 13 determines that power supply line 6 is a power supply line connected to electrode 3.

[0200] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0201] The following describes the operation of the interference suppression filter 15 according to the eighth embodiment with reference to the drawings. A flowchart showing the power supply line switching procedure through the interference suppression filter 15 according to the eighth embodiment is the same as in Fig. 14.

[0202] As in Fig. As shown in Figure 14, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST50).

[0203] The control circuit 13 then starts operation (step ST51).

[0204] The detection circuit 12-14 then detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the voltage (threshold voltage) Vref between the DC power supply 12-5 and the signal ground SG (step ST52). The detection circuit 12-14 outputs signal 1 to the control circuit 13 if the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0205] Subsequently, the control circuit 13 determines whether or not the signal 1 is detected (output) by the detection circuit 12-14 within a certain period of time (step ST53).

[0206] If signal 1 is not detected by the detection circuit 12-14 within the specified time period (NO in step ST53), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST54).

[0207] If signal 1 is detected by the detection circuit 12-14 within the specified time period (YES in step ST53), the control circuit 13 controls the relay 10 to create a short circuit between the Y capacitor 9 and the ground of the electrical device (step ST55).

[0208] As the next step from step ST54 or step ST55, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST56).

[0209] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST57). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0210] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the eighth embodiment described above. (Effect 1)

[0211] By providing only one detection circuit in the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented cost-effectively.

[0212] The representative embodiment of the interference suppression filter 15 has been explained above. In addition to the configurations of the first to seventh embodiments, the following configuration can also be adopted. The input unit of the detection circuit can, for example, be protected by a resistive voltage divider, an overvoltage protection element, a diode, or the like. The eighth embodiment described the example in which the voltages in the detection circuit are compared, but a method of connecting a resistor to the input unit and comparing the currents can also be used. The eighth embodiment described the configuration in which the detection circuit is connected only to the power supply line 5, but the detection circuit can also be connected only to the power supply line 6.

[0213] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the eighth embodiment comprises the detection circuit 12-14 with an input terminal connected to the power supply line 5, a ground terminal connected to the ground of the electrical device, and an output terminal connected to the control circuit 13, and detects the first voltage V1 between the power supply line 5 and the ground of the electrical device, and the detection circuit 12-14 compares the first voltage V1 with the threshold voltage Vref, and outputs the first signal from the output terminal if the first voltage V1 is equal to or greater than the threshold voltage Vref, and the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device.If the first signal from the detection circuit 12-14 is not output within the specified time period, and controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device, if the first signal from the detection circuit 12-14 is output within the specified time period.

[0214] According to the configuration above, the detected voltage can be used to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched. Ninth embodiment.

[0215] In the second to sixth embodiments, the configuration was described in which the same circuit is inserted into both the power supply line 5 and the power supply line 6 in the ground-side power supply line detection circuit 12. A ninth embodiment describes a configuration in which a circuit is inserted only into the power supply line 5.

[0216] The ninth embodiment is described below with reference to the drawings. It should be noted that the components which have the same functions as those described in the first embodiment are given the same reference numerals and are not described further.

[0217] A block diagram showing a configuration of an electrical device 4 according to the ninth embodiment is identical to the one shown in Fig. 13. As in Fig. Figure 13 shows a ground-side power supply line detection circuit 12 of an interference suppression filter 15, which is contained in the electrical device 4, comprising a detection circuit 12-14. The detection circuit 12-14 consists of the transistor 12-7, the resistor 12-9, and the DC power supply 12-11 in the fifth embodiment, or the optocoupler 12-12 in the sixth embodiment. The detection circuit 12-14 comprises an input terminal connected to the power supply line 5, a ground terminal connected to the signal ground SG, and an output terminal connected to the control circuit 13. The signal ground SG is connected to the ground of the electrical device.

[0218] The ground-side power supply line detection circuit 12 according to the ninth embodiment detects a result of the comparison of the voltage V1 between the power supply line 5 and the signal ground SG with the threshold voltage Vref of the detection circuit 12-14 (in particular transistor 12-7 or optocoupler 12-12). Vref is set to half the amplitude of the power supply voltage of the AC power supply 1.

[0219] The detection circuit 12-14 outputs the signal 1 to the control circuit 13 when the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0220] According to the ninth embodiment, the control circuit 13 determines, based on the comparison between the voltage V1 detected by the ground-side power supply line detection circuit 12 and the threshold voltage Vref, whether the power supply line connected to electrode 3 (ground-side power supply line) is power supply line 5 or power supply line 6. Specifically, in the ninth embodiment, if signal 1 is not detected by the detection circuit 12-14 within a certain period, the control circuit 13 determines that power supply line 5 is a power supply line connected to electrode 3. If signal 1 is detected by the detection circuit 12-14 within a certain period, the control circuit 13 determines that power supply line 6 is a power supply line connected to electrode 3.

[0221] If it is determined that power supply line 5 is the power supply line connected to electrode 3, control circuit 13 controls relay 8 to create a short circuit between Y-capacitor 7 and the ground of the electrical device. If it is determined that power supply line 6 is the power supply line connected to electrode 3, control circuit 13 controls relay 10 to create a short circuit between Y-capacitor 9 and the ground of the electrical device.

[0222] The following describes the operation of the interference suppression filter 15 according to the ninth embodiment with reference to the drawings. A flowchart showing a power supply line switching procedure through the interference suppression filter 15 according to the ninth embodiment is the same as the one shown in Fig. 14.

[0223] As in Fig. As shown in Figure 14, the power supply line 5 is connected to one of the electrodes 2 and 3, and the power supply line 6 is connected to the other of the electrodes 2 and 3 (step ST50).

[0224] The control circuit 13 then starts operation (step ST51).

[0225] The detection circuit 12-14 then detects the result of comparing the voltage V1 between the power supply line 5 and the signal ground SG with the threshold voltage Vref (step ST52). The detection circuit 12-14 outputs signal 1 to the control circuit 13 if the voltage V1 between the power supply line 5 and the signal ground SG is equal to or greater than the threshold voltage Vref.

[0226] Subsequently, the control circuit 13 determines whether or not the signal 1 is detected (output) by the detection circuit 12-14 within a certain period of time (step ST53).

[0227] If signal 1 is not detected by the detection circuit 12-14 within the specified time period (NO in step ST53), the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device (step ST54).

[0228] If signal 1 is detected by the detection circuit 12-14 within the specified time period (YES in step ST53), the control circuit 13 controls the relay 10 to create a short circuit between the Y capacitor 9 and the ground of the electrical device (step ST55).

[0229] As the next step from step ST54 or step ST55, the main circuit 14 of the electrical device starts the main operation of the electrical device 4 (step ST56).

[0230] The main circuit 14 of the electrical device is then disconnected from the AC power supply 1 to stop the main operation of the electrical device 4 (step ST57). At this point, the connection between the Y-capacitor 7 or the Y-capacitor 9 and the ground of the electrical device is released, since the excitation of the coil of the relay 8 or the relay 10 has stopped.

[0231] The following effects can be achieved by the components and operation of the interference suppression filter 15 according to the ninth embodiment described above. (Effect 1)

[0232] By providing only one detection circuit in the ground-side power supply line detection circuit 12, the interference suppression filter 15 can be implemented cost-effectively.

[0233] The representative embodiment of the interference suppression filter 15 has been explained above. In addition to the configurations of the first through eighth embodiments, the following configuration can also be adopted. The input unit of the detection circuit can, for example, be protected by a resistive voltage divider, an overvoltage protection element, a diode, or the like. The ninth embodiment described the example in which the voltages are compared by the detection circuit, but a method of connecting a resistor to an input unit and comparing the currents can also be used.In the ninth embodiment, an example was described in which Vref is set to half the amplitude of the power supply voltage of the AC power supply 1, but other values ​​can also be used, provided that Vref is equal to or less than the amplitude of the power supply voltage of the AC power supply 1. In the eighth embodiment, the configuration was described in which the detection circuit is connected only to the power supply line 5, but the detection circuit can also be connected only to the power supply line 6.

[0234] As described above, the ground-side power supply line detection circuit 12 in the interference suppression filter 15 according to the ninth embodiment comprises the detection circuit 12-14 with an input terminal connected to the power supply line 5, a ground terminal connected to the ground of the electrical device, and an output terminal connected to the control circuit 13, and detects the first voltage V1 between the power supply line 5 and the ground of the electrical device, and the detection circuit 12-14 compares the first voltage V1 with the threshold voltage Vref, and outputs the first signal from the output terminal if the first voltage V1 is equal to or greater than the threshold voltage Vref, and the control circuit 13 controls the relay 8 to create a short circuit between the Y-capacitor 7 and the ground of the electrical device.If the first signal from the detection circuit 12-14 is not output within the specified time period, and controls the relay 10 to create a short circuit between the Y-capacitor 9 and the ground of the electrical device, if the first signal from the detection circuit 12-14 is output within the specified time period.

[0235] According to the configuration above, the detected voltage can be used to determine whether the power supply line connected to electrode 3 is power supply line 5 or power supply line 6. Consequently, it is possible to create a short circuit between the Y-capacitor connected to the power supply line identified as the one connected to electrode 3 and the ground of the electrical device. That is, the power supply line connected to the Y-capacitor can be correctly switched.

[0236] The functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 are implemented by a processing circuit. That is, the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 comprise a processing circuit for executing the operations described in the Fig. 2, Fig. 4, Fig. 8, Fig. 10, Fig. 12 and Fig. 14. The processing circuit shown. The processing circuit can be dedicated hardware or a central processing unit (CPU) that executes a program stored in main memory.

[0237] Fig. Figure 15A is a block diagram showing a hardware configuration that implements the functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15. Fig. Figure 15B is a block diagram showing a hardware configuration that implements the functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15.

[0238] In a case where the processing circuit is a dedicated hardware processing circuit 20, as in Fig. As shown in Figure 15A, the processing circuit 20 corresponds, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof.

[0239] The functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 can be performed by separate processing circuits, or these functions can be performed together by one processing circuit.

[0240] Is the processing circuit one of the following? Fig. In the processor 21 shown in Figure 15B, the functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 are implemented by software, firmware or a combination of software and firmware.

[0241] The software or firmware is described as a program and stored in a working memory of 22.

[0242] The processor 21 reads the program stored in the main memory 22 and executes it, thereby realizing the functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15. That is, the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 contain the main memory 22 for storing a program that executes the processing of each input in the Fig. 2, Fig. 4, Fig. 8, Fig. 10, Fig. 12 and Fig. The step shown in 14 results when each of these functions is executed by processor 21.

[0243] These programs cause a computer to execute operations or procedures that are performed in the ground-side power supply detection circuit 12 and in the control circuit 13 of the interference suppression filter 15. The working memory 22 can be a computer-readable storage medium that stores a program that causes a computer to operate as the ground-side power supply detection circuit 12 and the control circuit 13 of the interference suppression filter 15.

[0244] Here, processor 21 refers, for example, to a central processing unit (CPU), a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a digital signal processor (DSP), or the like.

[0245] The working memory 22 corresponds, for example, to a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, a wipeable programmable read-only memory (EPROM) or an electrical EPROM (EEPROM), a magnetic disk such as a hard disk or a flexible disk, a flexible disk, an optical disk, a compact disk, a MiniDisc, a Compact Disc CD, a Digital Versatile Disc (DVD) or the like.

[0246] Some of the functions of the ground-side power supply line detection circuit 12 and the control circuit 13 of the interference suppression filter 15 can be performed by dedicated hardware, and some of them can be performed by software or firmware.

[0247] For example, the function of the ground-side power supply line detection circuit 12 is implemented by a processing circuit as dedicated hardware. In this case, the function of the control device 13 can be implemented by the processor 21, which executes a program stored in the main memory 22.

[0248] As described above, the processing circuit can implement any of the above-mentioned functions through hardware, software, firmware, or a combination thereof.

[0249] It should be noted that it is possible to freely combine any embodiment, to modify any components of any embodiment, or to omit any components in any embodiment. INDUSTRIAL APPLICABILITY

[0250] The interference suppression filter according to the present disclosure can correctly switch the power supply line connected to the Y-capacitor and can therefore be used in an electrical device. REFERENCE MARK LIST

[0251] 1: AC power supply, 2: Electrode, 3: Electrode, 4: Electrical device, 5: Power supply line, 6: Power supply line, 7: Y-capacitor, 8: Relay, 9: Y-capacitor, 10: Relay, 11: X-capacitor, 12: Ground-side power supply line detection circuit, 12-1: A / D converter, 12-2: A / D converter, 12-3: Comparator, 12-4: Comparator, 12-5: DC power supply, 12-7: Transistor, 12-8: Transistor, 12-9: Resistor, 12-10: Resistor, 12-11: DC power supply, 12-12: Optocoupler, 12-13: Optocoupler, 12-14: Detection circuit, 13: Control circuit, 14: Main circuit of electrical equipment, 15: interference suppression filter, 20: processing circuit, 21: processor, 22: main memory

Claims

[1] Noise filter (15) for an electrical device (4) connected to an AC power supply (1), comprising a first electrode (3) connected to a ground of a power supply and a second electrode (2) not connected to the ground of the power supply, the noise filter (15) comprising: a first power supply line (5) connected to one of the first electrode (3) and the second electrode (2); a second power supply line (6) connected to the other of the first electrode (3) and the second electrode (2); a first Y capacitor (7) connected to the first power supply line (5); a second Y capacitor (9) connected to the second power supply line (6); a first relay (8) connected between the first Y capacitor (7) and a ground of an electrical device; a second relay (10) connected between the second Y capacitor (9) and the ground of the electrical device; a ground-side power supply line detection circuit (12) connected to the first power supply line (5) and the second power supply line (6), respectively, and detecting a power supply line connected to the first electrode (3) from the first power supply line (5) and the second power supply line (6); and a control circuit (13) for determining whether a power supply line connected to the first electrode (3) is the first power supply line (5) or the second power supply line (6) based on a detection result by the ground-side power supply line detection circuit (12), which controls the first relay (8) to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device when it is determined that the power supply line connected to the first electrode (3) is the first power supply line (5), and controls the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device when it is determined that the power supply line connected to the first electrode (3) is the second power supply line (6). [2] Noise filter (15) according to claim 1, wherein in a case where a capacitance value of each of the first Y capacitor (7) and the second Y capacitor (9) is C [F], an upper limit of a leakage current in the noise filter (15) is I [A], an angular frequency of the AC power supply (1) is ω [rad / s], and a power supply voltage of the AC power supply (1) is V [V], a capacitance value C [F] of each of the first Y capacitor C≥Iω×V (7) and the second Y capacitor (9) follows the following formula (1). [3] Noise filter (15) according to claim 1, wherein the ground-side power supply line detection circuit (12) detects a first voltage between the first power supply line (5) and the ground of the electrical device and detects a second voltage between the second power supply line (6) and the ground of the electrical device, and the control circuit (13) determines whether the power supply line connected to the first electrode (3) is the first power supply line (5) or the second power supply line (6) by determining which of the amplitude of the first voltage and the amplitude of the second voltage detected by the ground-side power supply line detection circuit (12) is smaller, controlling the first relay (8) to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device when it is determined that the amplitude of the first voltage is smaller than the amplitude of the second voltage, and controlling the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device when it is determined that the amplitude of the first voltage is smaller than the amplitude of the second voltage. [4] Noise filter (15) according to claim 1, wherein the ground-side power supply line detection circuit (12) detects a first voltage between the first power supply line (5) and the ground of the electrical device and detects a second voltage between the second power supply line (6) and the ground of the electrical device, and the control circuit (13), when it is determined that the power supply line connected to the first electrode (3) is the first power supply line (5), controls the first relay (8) to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device at a time when the first voltage detected by the ground-side power supply line detection circuit (12) reaches zero, and when it is determined that the power supply line connected to the first electrode (3) is the second power supply line (6), controls the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device at a time when the second voltage detected by the ground-side power supply line detection circuit (12) reaches zero. [5] Noise filter (15) according to claim 3 or 4, wherein the ground-side power supply line detection circuit (12) comprises: a first analog / digital converter (12-1) for detecting a voltage between the first power supply line (5) and the ground of the electrical device; and a second analog / digital converter (12-2) for detecting a voltage between the second power supply line (6) and the ground of the electrical device. [6] Noise filter (15) according to claim 1, wherein the ground-side power supply line detection circuit (12) compares a first voltage between the first power supply line (5) and the ground of the electrical device with a threshold voltage, and outputs a first signal if the first voltage is equal to or greater than the threshold voltage, and compares a second voltage between the second power supply line (6) and the ground of the electrical device with the threshold voltage, and outputs a second signal if the second voltage is equal to or greater than the threshold voltage, and the control circuit (13), when the first signal is not output from the ground-side power supply line detection circuit (12) and the second signal is output from the ground-side power supply line detection circuit (12) during a certain period of time, or when the first signal and the second signal are output from the ground-side power supply line detection circuit (12) and an output time of the second signal is longer than an output time of the first signal during a certain period, the first relay (8) controls to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device, and when the first signal is output from the ground-side power supply line detection circuit (12) and the second signal is not output from the ground-side power supply line detection circuit (12) for a certain period of time, or when the first signal and the second signal are output from the ground-side power supply line detection circuit (12) and an output time of the first signal is longer than an output time of the second signal during a certain period, controls the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device. [7] Noise filter (15) according to claim 6, wherein the ground-side power supply line detection circuit (12) comprises a first comparator (12-3), a second comparator (12-4) and a DC power supply (12-5), the first comparator (12-3) has an input terminal connected to the first power supply line (5) and a positive terminal of the DC power supply (12-5), an output terminal connected to the control circuit (13), and a ground terminal connected to the ground of the electrical device, the second comparator (12-4) has an input terminal connected to the second power supply line (6) and a positive terminal of the DC power supply (12-5), an output terminal connected to the control circuit (13), and a ground terminal connected to the ground of the electrical device, the DC power supply (12-5) has a positive terminal connected to the input terminal of the first comparator (12-3) and the input terminal of the second comparator (12-4), and a negative terminal connected to the ground of the electrical device, the first comparator (12-3) compares the first voltage between the first power supply line (5) and the ground of the electrical device with a threshold voltage output from the DC power supply (12-5) and outputs the first signal from the output terminal when the first voltage is equal to or greater than the threshold voltage, and the second comparator (12-4) compares the second voltage between the second power supply line (6) and the ground of the electrical device with a threshold voltage output from the DC power supply (12-5), and outputs the second signal from the output terminal when the second voltage is equal to or greater than the threshold voltage. [8] Noise filter (15) according to claim 6, wherein the ground-side power supply line detection circuit (12) comprises a first transistor (12-7), a second transistor (12-8), a first resistor (12-9), a second resistor (12-10) and a DC power supply (12-11), the first transistor (12-7) has a base terminal connected to the first power supply line (5), a collector terminal connected to the control circuit (13) and a terminal of the first resistor (12-9), and an emitter terminal connected to the ground of the electrical device, the second transistor (12-8) has a base terminal connected to the second power supply line (6), a collector terminal connected to the control circuit (13) and a terminal of the second resistor (12-10), and an emitter terminal connected to the ground of the electrical device, the first resistor (12-9) has one terminal connected to the collector terminal of the first transistor (12-7) and the other terminal connected to a positive terminal of the DC power supply (12-11), the second resistor (12-10) has one terminal connected to the collector terminal of the second transistor (12-8) and the other terminal connected to a positive terminal of the DC power supply (12-11), the DC power supply (12-11) has a positive terminal connected to the other terminal of the first resistor (12-9) and the other terminal of the second resistor (12-10), and a negative terminal connected to the ground of the electrical device, the first transistor (12-7) compares the first voltage applied between the base terminal and the emitter terminal with a threshold voltage of the first transistor (12-7), and outputs the first signal from the collector terminal when the first voltage is equal to or greater than the threshold voltage of the first transistor (12-7), and the second transistor (12-8) compares the second voltage applied between the base terminal and the emitter terminal with a threshold voltage of the second transistor (12-8), and outputs the second signal from the collector terminal when the second voltage is equal to or greater than the threshold voltage of the second transistor (12-8). [9] Noise filter (15) according to claim 6, wherein the ground-side power supply line detection circuit (12) comprises: a first optocoupler (12-2) having an input terminal connected to the first power supply line (5) and the ground of the electrical device, and an output terminal connected to the control circuit (13); and a second optocoupler (12-13) having an input terminal connected to the second power supply line (6) and the ground of the electrical device, and an output terminal connected to the control circuit (13), the first optocoupler (12-12) compares the first voltage between the first power supply line (5) and the ground of the electrical device with a threshold voltage of the first optocoupler (12-12), and outputs the first signal from an output terminal when the first voltage is equal to or greater than the threshold voltage of the first optocoupler (12-12), and the second optocoupler (12-13) compares the second voltage between the second power supply line (6) and the ground of the electrical device with a threshold voltage of the second optocoupler (12-13), and outputs the second signal from an output terminal when the second voltage is equal to or greater than the threshold voltage of the second optocoupler (12-13). [10] Noise filter (15) according to claim 1, wherein the ground-side power supply line detection circuit (12) comprises an analog / digital converter (12-1) having an input terminal connected to the first power supply line (5), a ground terminal connected to the ground of the electrical device, and an output terminal connected to the control circuit (13), and detects a first voltage between the first power supply line (5) and the ground of the electrical device, the analog / digital converter (12-1) converts the detected first voltage into a digital signal and outputs the digital signal to the control circuit (13), and the control circuit (13) compares the first voltage detected by the analog / digital converter (12-1) with a threshold voltage within a certain period of time, and the first relay (8) controls to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device if the first voltage does not reach or exceed the threshold voltage within the specified period of time, and controlling the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device when the first voltage reaches or exceeds the threshold voltage within the specified period of time. [11] Noise filter (15) according to claim 1, wherein the ground-side power supply line detection circuit (12) comprises a detection circuit (12-14) having an input terminal connected to the first power supply line (5), a ground terminal connected to the ground of the electrical device, and an output terminal connected to the control circuit (13), and detects a first voltage between the first power supply line (5) and the ground of the electrical device, the detection circuit (12-14) compares the first voltage with a threshold voltage, outputs a first signal from the output terminal when the first voltage is equal to or greater than the threshold voltage, and the control circuit (13) the first relay (8) is controlled to cause a short circuit between the first Y capacitor (7) and the ground of the electrical device if the first signal from the detection circuit (12-14) is not output for a certain period of time, and controlling the second relay (10) to cause a short circuit between the second Y capacitor (9) and the ground of the electrical device when the first signal is output from the detection circuit during a certain period of time.

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