DEVICE FOR DETECTING FAILURE OF LIGHT CONTROL SHEET AND METHOD FOR DETECTING FAILURE OF LIGHT CONTROL SHEET

Abstract

To provide a device and method for detecting failure of light control sheets.SOLUTION: A light control sheet failure detection device is provided, comprising: a voltage application unit configured to apply a drive voltage VLD for driving a liquid crystal compound between transparent electrode layers 22, 23 of a light control sheet 20 provided with the liquid crystal compound between the transparent electrode layers 22, 23; a current detection circuit 35 and failure determination circuit 32 configured to detect presence / absence of micro short circuits between the transparent electrode layers 22, 23 on the basis of current flowed by the drive voltage; and a voltage modification unit configured to change the voltage between the transparent electrode layers 22, 23 from the drive voltage VLD to a repair voltage VLR that is higher than the drive voltage VLD when the presence of micro short circuits is detected by the failure determination circuit 32.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fault detection device for a light controlling sheet and a fault detection method for a light controlling sheet. [Background technology]

[0002] A polymer-dispersed light-controlling sheet includes a polymer compound layer between a first transparent electrode layer and a second transparent electrode layer. The polymer compound layer defines voids to be filled with a liquid crystal compound. The orientation state of the liquid crystal compound follows a change in voltage between the first transparent electrode layer and the second transparent electrode layer. A driving device for the light-controlling sheet changes the light-controlling sheet from transparent to opaque, or from opaque to transparent, by changing the voltage between the first transparent electrode layer and the second transparent electrode layer (see, for example, Patent Document 1).

[0003] When a structural abnormality such as a break or crack occurs in the transparent electrode layer, electrical characteristic values ​​such as resistance, voltage, and current change in the transparent electrode layer. A light-control sheet failure detection device detects that the electrical characteristic values ​​of the transparent electrode are not normal, indicating a failure of the light-control sheet (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-187775 A [Patent Document 2] JP 2018-41139 A Summary of the Invention [Problem to be solved by the invention]

[0005] Electrical failures, such as insulation or conduction abnormalities, can occur in various situations when manufacturing light-adjusting films, during installation, during use, etc. Technology that can assist in identifying the failed part will not only reduce the burden of repairs, but also increase the number of situations in which light-adjusting films can be used, thereby further promoting the spread of light-adjusting films.

[0006] For example, when manufacturing a light-adjusting sheet, the edge of the light-adjusting sheet is formed by a process of cutting a series of sheets to the product size. Or, when attaching a light-adjusting sheet to a transparent plate, the edge of the light-adjusting sheet is formed by a process of cutting the edge of the light-adjusting sheet along the transparent plate. At this time, since the thickness of the polymer compound layer is less than 1 mm, these cutting processes are carried out carefully so as not to cause a short circuit between the first transparent electrode layer and the second transparent electrode layer in a small portion of the transparent electrode layer.

[0007] The causes of short circuits will be further examined. For example, when manufacturing a light-adjusting sheet, conductive fine particles present in the manufacturing environment of the light-adjusting sheet become mixed into the polymer compound layer. The mixing of conductive fine particles is said to cause a short circuit between the first transparent electrode layer and the second transparent electrode layer in a very small area within the surface of the light-adjusting sheet. Furthermore, when using the light-adjusting sheet, moisture present in the environment in which the light-adjusting sheet is used adheres to the edge surface of the light-adjusting sheet. The adhesion of moisture is said to cause a ground fault in the transparent electrode in a very small area on the edge surface of the light-adjusting sheet.

[0008] For example, when connecting a driving circuit to a light-controlling sheet, if a mechanical load is applied to the wiring that connects the transparent electrode layer to the driving circuit, a force that peels the terminal from the transparent electrode layer and a force that distorts the connection between the terminal and the driving circuit are generated. The force that peels the terminal from the transparent electrode layer increases the contact resistance between the transparent electrode layer and the terminal. In addition, the force that distorts the connection between the terminal and the driving circuit increases the connection resistance between the terminal and the driving circuit. [Means for solving the problem]

[0009] A light-adjusting sheet fault detection device for solving the above problem includes a voltage application unit that applies a drive voltage between transparent electrode layers of a light-adjusting sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound, and a detection unit that detects a current flowing between the transparent electrode layers by application of the drive voltage and detects a fault in the light-adjusting sheet based on the detected current. The detection unit detects a first fault when the peak value of the current is equal to or smaller than a predetermined first threshold, and detects a second fault when the convergence value of the current is greater than a predetermined second threshold.

[0010] A light-adjusting sheet failure detection device for solving the above problem includes applying a drive voltage between transparent electrode layers of a light-adjusting sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound, detecting a current flowing between the transparent electrode layers due to the application of the drive voltage, and detecting a failure of the light-adjusting sheet based on the detected current. Detecting a failure of the light-adjusting sheet includes detecting a first failure when the peak value of the current is equal to or smaller than a predetermined first threshold, and detecting a second failure when the convergence value of the current is greater than a predetermined second threshold.

[0011] According to each of the above configurations, the peak value of the current flowing between the transparent electrode layers being equal to or lower than a predetermined first threshold value is detected as a first fault. This allows a fault resulting from a low peak value of the current flowing between the transparent electrode layers, such as an increase in the contact resistance between the transparent electrode layers and the wiring, or a decrease in the capacitance of the liquid crystal compound, to be detected as a fault in the light controlling sheet.

[0012] In addition, a second fault is detected when the convergence value of the current flowing between the transparent electrode layers is greater than a predetermined second threshold value. This allows a fault resulting from a high convergence value of the current flowing between the transparent electrode layers, such as a micro-short circuit between the transparent electrode layers, to be detected as a fault in the light control sheet.

[0013] From the above, for example, it becomes easy to identify the contact portion between the transparent electrode layer and the wiring as the failure occurrence portion, the liquid crystal compound as the failure occurrence portion, or the transparent electrode layer gap as the failure occurrence portion, etc. As a result, it is possible to assist in identifying the portion where the failure occurs in the light controlling sheet.

[0014] In the above-mentioned light controlling sheet fault detection device, the voltage application unit may supply a drive signal between the transparent electrode layers, the drive signal being an AC voltage with the drive voltage set to a peak-to-peak value, a predetermined period shorter than a half cycle of the drive signal being a first sampling period, a predetermined period shorter than a half cycle of the drive signal being a second sampling period, and the first sampling period and the second sampling period may start and end when the voltage application unit inverts the polarity of the drive voltage. The detection unit may use the current detected during the first sampling period as a sample and detect the peak value from the sample, and use the current detected during the second sampling period as a sample and detect the convergence value from the sample.

[0015] The liquid crystal compound functioning as a capacitance passes a current that rises sharply when a driving voltage is applied, and then passes a current that decays exponentially. According to the above configuration, a first sampling period suitable for detecting a peak value is determined. Also, a second sampling period suitable for detecting a convergence value is determined. Then, a peak value is detected for the detection current in the first sampling period, and a convergence value is detected for the detection current in the second sampling period. This allows both the peak value and the convergence value to be detected with high accuracy.

[0016] In the above-mentioned light controlling sheet fault detection device, the current flowing into one of the transparent electrode layers is a source current, and the current drawn out from the other transparent electrode layer is a sink current. The detection unit may detect a third fault as a difference between the source current and the sink current being equal to or greater than a third threshold. With this configuration, a fault resulting from a large difference between the sink current and the source current, i.e., a system leakage current, can be detected.

[0017] In the above-mentioned light-adjusting sheet fault detection device, the voltage application unit may stop applying voltage between the transparent electrode layers when the detection unit detects the first fault, and may apply a repair voltage higher than the driving voltage between the transparent electrode layers when the detection unit detects the second fault.

[0018] As described above, a fault resulting from a low peak value of the current flowing between the transparent electrode layers is, for example, an increase in the contact resistance between the transparent electrode layer and the wiring, or a decrease in the capacitance of the liquid crystal compound. An increase in the contact resistance or a decrease in the capacitance of the liquid crystal compound requires repair of the connection structure or replacement of the light-adjusting sheet itself. In this regard, if the voltage application unit is configured to stop applying voltage between the electrode layers when the detection unit detects the first fault, as in the above configuration, it is possible to prompt repair of the connection structure or replacement of the light-adjusting sheet itself.

[0019] On the other hand, a fault resulting from the convergence value of the current flowing between the transparent electrode layers being greater than the predetermined second threshold is, for example, a micro-short circuit between the transparent electrode layers. The micro-short circuit between the transparent electrode layers is melted by application of a repair voltage higher than the driving voltage. In this regard, if the above-mentioned configuration is such that a high repair voltage is applied when the second fault is detected, it is possible to perform repairs appropriate for the fault in the light control sheet, such as melting the micro-short circuit.

[0020] A light-adjusting sheet fault detection device for solving the above problem includes a voltage application unit that applies a drive voltage between transparent electrode layers of a light-adjusting sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound, and a detection unit that extracts a current flowing between the transparent electrode layers due to the application of the drive voltage during a predetermined sampling period and detects a fault in the light-adjusting sheet based on a current waveform that is the extracted sample. The detection unit identifies a first characteristic value derived from a contact resistance value between the transparent electrode layer and a wiring from the current waveform, detects the identified first characteristic value being outside a predetermined normal range as a first fault that is an increase in the contact resistance value, identifies a second characteristic value derived from a resistance value between the transparent electrode layers from the current waveform, and detects the identified second characteristic value being outside a predetermined normal range as a second fault that is a micro-short circuit between the transparent electrode layers.

[0021] A method for detecting a fault in a light-adjusting sheet for solving the above problem includes applying a driving voltage between transparent electrode layers of a light-adjusting sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound, extracting a current flowing between the transparent electrode layers due to the application of the driving voltage during a predetermined sampling period, and detecting a fault in the light-adjusting sheet based on the current waveform, which is the extracted sample. Detecting a fault in the light-adjusting sheet includes identifying a first characteristic value derived from a contact resistance value between the transparent electrode layer and a wiring from the current waveform, detecting the identified first characteristic value being outside a predetermined normal range as a first fault that is an increase in the contact resistance value, identifying a second characteristic value derived from a resistance value between the transparent electrode layers from the current waveform, and detecting the identified second characteristic value being outside a predetermined normal range as a second fault that is a micro-short circuit between the transparent electrode layers.

[0022] A liquid crystal compound that functions as a capacitor passes a current that rises sharply when a driving voltage is applied, and then the current passes so that it decays exponentially. Here, an increase in the contact resistance between the transparent electrode layer and the wiring lowers the peak value after the steep rise in current and slows the rate at which the current decays from the peak. A micro-short circuit between the transparent electrode layers increases the convergence value where the decay converges. In this regard, according to each of the above configurations, a first characteristic value derived from the contact resistance value is identified from the waveform of the current flowing between the transparent electrode layers. Then, the fact that the identified first characteristic value is outside the normal range is detected as a first fault, which is an increase in the contact resistance value. This makes it possible to identify the contact point between the transparent electrode layer and the wiring as the fault occurrence point. Also, a second characteristic value derived from the resistance value between the transparent electrode layers is identified from the current waveform. Then, the fact that the identified second characteristic value is outside the normal range is detected as a second fault, which is the presence of a micro-short circuit. This makes it possible to identify the presence of the fault occurrence point between the transparent electrode layers.

[0023] From the above, for example, it becomes easy to identify the contact part between the transparent electrode layer and the wiring as the failure occurrence part, or to identify the part between the transparent electrode layers as the failure occurrence part. As a result, it is possible to assist in identifying the part where the failure occurs in the light controlling sheet. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a block diagram showing the configuration of a power supply circuit. [Diagram 2] FIG. 2 is a circuit diagram showing the configuration of the drive voltage generating circuit. [Diagram 3] FIG. 3 is a timing chart showing the operation of the voltage application unit. [Figure 4] FIG. 4 is a block diagram illustrating an example of the configuration of the failure detection unit. [Diagram 5] FIG. 5 is a circuit diagram showing an example of a circuit of the failure detection unit. [Figure 6] FIG. 6 is a timing chart showing the operation of the failure detection unit. [Figure 7] FIG. 7 is a flowchart showing the operation of the power supply circuit. [Figure 8] FIG. 8 is a circuit diagram showing an equivalent circuit used in the circuit simulation. [Figure 9] FIG. 9 is a graph showing the change in the detection current over time. [Figure 10] FIG. 10 is a graph showing the relationship between the peak value and the contact resistance. [Figure 11] FIG. 11 is a graph showing the change in the detection current over time. [Figure 12] FIG. 12 is a graph showing the relationship between the convergence value and the peripheral resistance. [Figure 13] FIG. 13 is a graph showing changes in the detected current over time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of a fault detection device for a light controlling sheet and a fault detection method for a light controlling sheet will be described. The light-adjusting system includes a fault detection device for the light-adjusting sheet. The fault detection device for the light-adjusting sheet executes a fault detection method for the light-adjusting sheet. The light-adjusting system includes a power supply circuit 10 and a light-adjusting sheet 20. The power supply circuit 10 constitutes the fault detection device for the light-adjusting sheet and a drive device for the light-adjusting sheet.

[0026] [Composition of light control sheet] The light control sheet 20 includes a light control layer 21. The light control layer 21 includes a polymer compound layer and a liquid crystal compound held in the polymer compound layer. The liquid crystal compound is held in the light control layer 21 in a polymer dispersion type, a polymer network type, or a capsule type. The light control sheet 20 includes a first transparent electrode layer 22 and a second transparent electrode layer 23. The light control layer 21 is located between the first transparent electrode layer 22 and the second transparent electrode layer 23.

[0027] A driving voltage is applied between the first transparent electrode layer 22 and the second transparent electrode layer 23. The liquid crystal compound assumes a first alignment state when the driving voltage is applied, and assumes a second alignment state when the current is stopped.

[0028] The repair voltage is applied between the first transparent electrode layer 22 and the second transparent electrode layer 23. Any micro-short circuit that may occur in the light-adjusting sheet 20 is cut off by application of the repair voltage. An example of a micro-short circuit may occur inside the light-adjusting layer 21 or on the edge surface of the light-adjusting sheet 20. A micro-short circuit causes an excessive current to flow in the circuit of the light-adjusting system, but not enough to blow a fuse in the protection circuit of the light-adjusting system. A micro-short circuit causes an excessive current to flow in the light-adjusting layer 21, causing a difference in optical properties such as transmittance and haze.

[0029] The driving type of the light controlling sheet 20 is either a normal type or a reverse type. The normal type light controlling sheet 20 is transparent in a first state. The normal type light controlling sheet 20 is opaque in a second state. In contrast, the reverse type light controlling sheet 20 is opaque in the first state. The reverse type light controlling sheet 20 is transparent in the second state. The transparent light controlling sheet 20 has a higher light transmittance than the opaque light controlling sheet 20.

[0030] When the normal-type light-adjusting sheet 20 is opaque, the light transmittance of the light-adjusting sheet 20 has the lowest value within the driving range of the light-adjusting sheet 20. When the reverse-type light-adjusting sheet 20 is transparent, the light transmittance of the light-adjusting sheet 20 has the highest value within the driving range of the light-adjusting sheet 20.

[0031] When the normal-type light-adjusting sheet 20 is transparent, the light transmittance of the light-adjusting sheet 20 may be the highest value within the driving range of the light-adjusting sheet 20, or may be an intermediate value within the driving range of the light-adjusting sheet 20. When the reverse-type light-adjusting sheet 20 is opaque, the light transmittance of the light-adjusting sheet 20 may be the lowest value within the driving range of the light-adjusting sheet 20, or may be an intermediate value within the driving range of the light-adjusting sheet 20.

[0032] [Functional configuration of the power supply circuit] Next, the functional configuration of the power supply circuit 10 will be described. The power supply circuit 10 is connected to an external power supply 50. The external power supply 50 may be an AC power supply that outputs an AC voltage as a power supply voltage, or may be a DC power supply that outputs a DC voltage as a power supply voltage. An example of an AC power supply is a commercial power supply. An example of a DC power supply is a power supply for auxiliary equipment mounted on a mobile object.

[0033] The power supply circuit 10 converts a power supply voltage into a drive voltage and generates a drive signal from the drive voltage. The power supply circuit 10 converts a power supply voltage into a repair voltage and generates a repair signal from the repair voltage. The power supply circuit 10 supplies the drive signal to the light control sheet 20. The power supply circuit 10 determines whether or not there is a micro-short circuit, and when it determines that there is a micro-short circuit, it switches the supply of the drive signal to the supply of the repair signal. After supplying the repair signal for a predetermined time, the power supply circuit 10 switches the supply of the repair signal to the supply of the drive signal. Note that the power supply circuit 10 may switch the supply of the repair signal to the supply of the drive signal after executing the process of supplying the repair signal for a predetermined time a predetermined number of times.

[0034] The power supply circuit 10 detects at least one of a source current and a sink current as a detected current. The source current is a current flowing from the power supply circuit 10 to the light controlling sheet 20. The sink current is a current returning from the light controlling sheet 20 to the power supply circuit 10.

[0035] The power supply circuit 10 determines the presence or absence of a fault based on the instantaneous value of the detected current. The power supply circuit 10 identifies the type of fault based on the instantaneous value of the detected current. The types of fault are [A] to [C] below. The instantaneous value of the detected current is at least one of the peak value of the detected current and the convergence value of the detected current. The peak value is an example of a first characteristic value. The convergence value is an example of a second characteristic value. [A] System leakage current [B] High resistance of the transmission line or low capacitance of the liquid crystal / abnormality when inverted [C] Micro-short circuit / convergence anomaly

[0036] (A: System leakage) Deterioration of the members that electrically insulate the dimming system from the surrounding environment shorts the transmission path of the dimming system to the surrounding environment. For example, deterioration of the members that insulate each of the transparent electrode layers 22, 23 from the surrounding environment shorts each of the transparent electrode layers 22, 23 themselves to the surrounding environment. For example, deterioration of the members that insulate the wiring that connects each of the transparent electrode layers 22, 23 to the power supply circuit 10 from the surrounding environment shorts the wiring to the surrounding environment. In this way, the range in which the transmission path is shorted to the surrounding environment can expand as the dimming system deteriorates over time.

[0037] A short circuit in the transmission path in the dimming system may cause a portion of the current entering the first transparent electrode layer 22 and a portion of the current exiting the first transparent electrode layer 22 to leak from the dimming system. A short circuit in the transmission path in the dimming system may cause a portion of the current entering the second transparent electrode layer 23 and a portion of the current exiting the first transparent electrode layer 22 to leak from the dimming system.

[0038] Such a system leakage current may cause an abnormal current to flow between the first transparent electrode layer 22 and the power supply circuit 10, or between the second transparent electrode layer 23 and the power supply circuit 10, to the extent that the light control sheet 20 is driven. An event caused by a system leakage current appears as a difference between the source current and the sink current.

[0039] The power supply circuit 10 determines whether or not there is a system leakage current based on the difference between the source current and the sink current. For example, when the difference between the source current and the sink current is equal to or less than a predetermined third threshold, the power supply circuit 10 determines that there is no system leakage current. On the other hand, when the difference between the source current and the sink current is greater than the third threshold, the power supply circuit 10 determines that there is a system leakage current, which is an example of a third fault.

[0040] (B: Anomaly during inversion / high resistance of transmission line) The transmission path for electrically connecting the first transparent electrode layer 22 to the power supply circuit 10 changes its electrical characteristic values ​​due to various types of deterioration such as deterioration of the transmission material, deterioration of the electrical joint, etc. The transmission path for electrically connecting the second transparent electrode layer 23 to the power supply circuit 10 also changes its electrical characteristic values ​​due to various types of deterioration such as deterioration of the transmission material, deterioration of the electrical joint, etc.

[0041] Examples of characteristic values ​​in the transmission path of the light control system are the electrical resistance of the transmission member itself and the contact resistance between the transmission members. For example, the characteristic value of the wiring connecting each transparent electrode layer 22, 23 to the power supply circuit 10 is the resistance of the wiring itself. For example, the characteristic value between each transparent electrode layer 22, 23 and the wiring is the contact resistance between each transparent electrode layer 22, 23 and the wiring.

[0042] An increase in the resistance value in the transmission member or an increase in the contact resistance value between the transmission members increases the power consumption of the light control system and causes the light transmittance of the light control sheet 20 to deviate from its original value. Events caused by an increase in the resistance of the transmission member or an increase in the resistance between the transmission members appear as a decrease in the peak value of the source current or a decrease in the peak value of the sink current.

[0043] The power supply circuit 10 judges whether or not a high resistance occurs based on the peak value of the source current or the peak value of the sink current. For example, when the peak value of the source current is greater than a predetermined threshold, the power supply circuit 10 judges that a high resistance does not occur in the transmission path of the source current. On the other hand, when the peak value of the source current is equal to or less than the predetermined threshold, the power supply circuit 10 judges that a high resistance occurs in the transmission path of the source current. Also, for example, when the peak value of the sink current is greater than a predetermined threshold, the power supply circuit 10 judges that a high resistance does not occur in the transmission path of the sink current. On the other hand, when the peak value of the sink current is equal to or less than the predetermined threshold, the power supply circuit 10 judges that a high resistance occurs in the transmission path of the sink current.

[0044] (B: Abnormal when inverting / low liquid crystal capacity) Deterioration of the liquid crystal composition causes a decrease in capacitance due to the liquid crystal composition in the light control layer 21. The decrease in capacitance of the light control layer 21 increases the power consumption of the light control system and causes the light transmittance of the light control sheet 20 to deviate from its original value. The phenomenon caused by the decrease in capacitance due to the liquid crystal composition appears as a decrease in the peak value of the source current or a decrease in the peak value of the sink current.

[0045] The power supply circuit 10 judges whether or not a capacitance reduction has occurred based on the peak value of the source current or the peak value of the sink current. For example, when the peak value of the source current or the peak value of the sink current is greater than a predetermined threshold, the power supply circuit 10 judges that a capacitance reduction has not occurred in the dimming layer 21. On the other hand, when the peak value of the source current or the peak value of the sink current is equal to or less than the predetermined threshold, the power supply circuit 10 judges that a capacitance reduction has occurred in the dimming layer 21.

[0046] (C: Convergence anomaly / micro short circuit) When the first transparent electrode layer 22 is short-circuited to the second transparent electrode layer 23, an excessive current flows through the light control sheet 20 and the power supply circuit 10. In order to prevent the short-circuit current from flowing, the power supply circuit 10 may be provided with a fuse. The fuse is blown by the supply of a short-circuit current. However, the fuse's blowing current is set large so that the fuse is not blown by the supply of a ripple current. In this way, even if the power supply circuit 10 is provided with a fuse, the fuse's blowing characteristics are required to withstand the supply of a ripple current. As a result, the occurrence of a minute short-circuit current that does not blow the fuse still remains, regardless of the presence or absence of a fuse.

[0047] An event that generates a minute short circuit current is a short circuit in a minute part of the light-adjusting sheet 20. A short circuit in a minute part of the light-adjusting sheet 20 includes a short circuit between a part of the edge of the first transparent electrode layer 22 and the second transparent electrode layer 23, a short circuit between a part of the edge of the second transparent electrode layer 23 and the first transparent electrode layer 22, and a short circuit within the plane of the light-adjusting sheet 20 via conductive fine particles that are foreign matter. The occurrence of a minute short circuit current causes the light transmittance of the light-adjusting sheet 20 to differ from its original value. Furthermore, whether the deviation in light transmittance is visible or not, the continued occurrence of a minute short circuit current increases the power consumption of the light-adjusting sheet 20 to a considerable extent.

[0048] Such a micro-short circuit can cause an abnormal current to flow between the first transparent electrode layer 22 and the second transparent electrode layer 23, to the extent that the light control sheet 20 is driven. An event caused by a micro-short circuit appears as a leakage current value that is the convergence value of the source current, or a leakage current value that is the convergence value of the sink current.

[0049] The power supply circuit 10 judges whether or not a micro-short circuit exists based on the convergence value of the source current or the convergence value of the sink current. For example, when the convergence value of the source current or the convergence value of the sink current is equal to or less than a predetermined threshold, the power supply circuit 10 judges that a micro-short circuit does not exist. On the other hand, when the convergence value of the source current or the convergence value of the sink current is greater than the predetermined threshold, the power supply circuit 10 judges that a micro-short circuit exists.

[0050] [Electrical configuration of the power supply circuit] Next, a detailed electrical configuration of an example of the power supply circuit 10 will be described. The power supply circuit 10 includes a transformer circuit 11, a first boost circuit 12, a second boost circuit 13, a control power supply generating circuit 14, a timing control circuit 15, a drive voltage generating circuit 16, a switching circuit 17, a clock generating circuit 18, and a drive circuit 31. The drive circuit 31 includes a fault determination circuit 32, a fault state display circuit 33, and a current detection circuit 35.

[0051] The first boost circuit 12, the timing control circuit 15, the drive voltage generation circuit 16, and the current detection circuit 35 constitute a voltage application section. The timing control circuit 15 and the clock generation circuit 18 constitute a timing control section. The timing control section, the fault determination circuit 32, and the current detection circuit 35 constitute a fault detection section. The second boost circuit 13, the switching circuit 17, the timing control circuit 15, the drive voltage generation circuit 16, and the current detection circuit 35 constitute a voltage change section.

[0052] The transformer circuit 11 converts the output voltage of the external power supply 50 into an input voltage for the boost circuit. The transformer circuit 11 converts the output voltage of the external power supply 50 into an input voltage for the control power supply generating circuit 14. For example, when the output voltage of the external power supply 50 is an AC voltage of 100V, the transformer circuit 11 generates an input voltage for the first boost circuit 12, the second boost circuit 13, and the control power supply generating circuit 14 from the AC voltage of 100V.

[0053] The first boost circuit 12 generates a driving voltage VLD from the output voltage of the transformer circuit 11. The driving voltage VLD has a magnitude suitable for driving the light-controlling sheet 20 when no fault occurs. An example of the driving voltage VLD is 50 V. Driving the light-controlling sheet 20 transitions the light-controlling sheet 20 from the second state to the first state.

[0054] The second boost circuit 13 generates a repair voltage VLR from the output voltage of the transformer circuit 11. The repair voltage VLR is a voltage suitable for repairing a faulty light-control sheet 20. The repair voltage VLR is higher than the driving voltage VLD. A micro-short circuit in the light-control sheet 20 is cut off by application of the repair voltage VLR. An example of the repair voltage VLR is 80V.

[0055] The control power supply generating circuit 14 generates a voltage of a logic level from the output voltage of the transformer circuit 11. The control level is a magnitude suitable for the calculation of the timing control circuit 15. The control level is also a magnitude suitable for the calculation of the drive circuit 31. The logic level is lower than the drive level. An example of the logic level is 3.3V.

[0056] The timing control circuit 15 inverts the polarity of the voltage applied to the light-adjusting sheet 20 in the driving voltage generating circuit 16. The polarity inversion frequency of the voltage applied to the light-adjusting sheet 20 may be a low frequency of 1 Hz or more and 60 Hz or less, or may be a frequency higher than 60 Hz. The higher the polarity inversion frequency, the higher the power consumption of the light-adjusting system. The polarity inversion frequency of the voltage applied to the light-adjusting sheet 20 may be appropriately set based on the power consumption required for the light-adjusting system. In addition, the lower the polarity inversion frequency, the more likely it is that uneven distribution of impurities contained in the liquid crystal composition will occur. The polarity inversion frequency of the voltage applied to the light-adjusting sheet 20 may be appropriately set based on various physical property values ​​of the liquid crystal composition.

[0057] The timing control circuit 15 aligns the polarity reversal timing of the drive voltage generation circuit 16 with the sampling period of the current detection circuit 35. One example of the sampling period determines a period during which a sample is extracted to detect a peak value of the detected current. Another example of the sampling period determines a period during which a sample is extracted to detect a convergence value of the detected current. The peak value and convergence value of the detected current are examples of instantaneous values.

[0058] Because the light-adjusting layer 21 is a capacitive element, the peak value of the detected current appears immediately after a voltage is applied to the light-adjusting sheet 20. In other words, the peak value of the detected current appears immediately after the polarity reversal of the voltage applied to the light-adjusting sheet 20. The timing control circuit 15 refers to the timing of the polarity reversal of the voltage applied to the light-adjusting sheet 20, and aligns the timing immediately after the polarity reversal of the voltage applied to the light-adjusting sheet 20 with the start of sampling the peak value.

[0059] Since the light-adjusting layer 21 is a capacitive element, the convergence value of the sensed current appears immediately before the polarity reversal of the voltage applied to the light-adjusting sheet 20. The timing control circuit 15 refers to the timing of the polarity reversal of the voltage applied to the light-adjusting sheet 20, and aligns the timing immediately before the polarity reversal of the voltage applied to the light-adjusting sheet 20 with the end of sampling of the convergence value.

[0060] The timing control circuit 15 generates an internal clock signal for generating the inversion control signal SIGR. The timing control circuit 15 generates the inversion control signal SIGR from the internal clock signal. The timing control circuit 15 outputs the inversion control signal SIGR to the drive voltage generation circuit 16. The drive voltage generation circuit 16 inverts the polarity of the voltage applied to the light controlling sheet 20 based on the inversion control signal SIGR.

[0061] The drive voltage generating circuit 16 generates a drive signal SVD from the output voltage of the switching circuit 17. The drive voltage generating circuit 16 generates a repair signal SVR from the output voltage of the switching circuit 17. The drive signal SVD is an AC voltage signal. The drive signal SVD sets the drive voltage VLD to a peak-to-peak value, and repeats polarity inversion of the drive voltage VLD based on the inversion control signal SIGR. The repair signal SVR is an AC voltage signal. The repair signal SVR sets the repair voltage VLR to a peak-to-peak value, and repeats polarity inversion of the repair voltage VLR based on the inversion control signal SIGR.

[0062] The driving voltage generating circuit 16 supplies a driving signal SVD to the light controlling sheet 20 through the current detecting circuit 35. The driving voltage generating circuit 16 supplies a repair signal SVR to the light controlling sheet 20 through the current detecting circuit 35.

[0063] The switching circuit 17 inputs either the output voltage of the first boost circuit 12 or the output voltage of the second boost circuit 13 to the drive voltage generating circuit 16. The switching circuit 17 sets either the drive voltage VLD or the repair voltage VLR as the output level VD of the switching circuit 17.

[0064] The fault determination circuit 32 supplies a repair request signal SIGS to the switching circuit 17. In response to the supply of the repair request signal SIGS, the switching circuit 17 switches the output level VD from the drive voltage VLD to the repair voltage VLR. In response to the stop of the supply of the repair request signal SIGS, the switching circuit 17 switches the output level VD from the repair voltage VLR to the drive voltage VLD.

[0065] [Circuit configuration of voltage application section] Next, a circuit configuration of an example of a voltage application section included in the power supply circuit 10 will be described. 2, the drive voltage generating circuit 16 includes an H-bridge circuit. The H-bridge circuit includes a first switch SW1, a second switch SW2, a third switch SW3, and a fourth switch SW4. The H-bridge circuit is a parallel circuit including a series circuit including the first switch SW1 and the third switch SW3, and a series circuit including the second switch SW2 and the fourth switch SW4.

[0066] An input terminal of the H-bridge circuit is connected to an output terminal of the switching circuit 17. An output terminal of the H-bridge circuit is connected to a ground terminal of the power supply circuit 10. A connection point between the first switch SW1 and the third switch SW3 is connected to the second transparent electrode layer 23. A connection point between the second switch SW2 and the fourth switch SW4 is connected to the first transparent electrode layer 22.

[0067] As shown in FIG. 3, the first switch SW1 and the fourth switch SW4 are turned on at the same timing. The first switch SW1 and the fourth switch SW4 are turned off at the same timing. The second switch SW2 and the third switch SW3 are turned on at the same timing. The second switch SW2 and the third switch SW3 are turned off at the same timing. The states of the switches SW1, SW2, SW3, and SW4 are determined by polarity inversion signals. The on state of the first switch SW1 and the on state of the second switch SW2 are alternately repeated.

[0068] For example, the timing control circuit 15 outputs the inverted control signal SIGR so that the first switch SW1 and the fourth switch SW4 are in the ON state and the second switch SW2 and the third switch SW3 are in the OFF state from timing T1 to timing T2. When the first switch SW1 and the fourth switch SW4 are in the ON state, the second transparent electrode layer 23 is connected to the output level VD of the switching circuit 17. When the second switch SW2 and the third switch SW3 are in the OFF state, the first transparent electrode layer 22 is connected to the ground level GND.

[0069] For example, the timing control circuit 15 outputs the inverted control signal SIGR so that the first switch SW1 and the fourth switch SW4 are in the OFF state and the second switch SW2 and the third switch SW3 are in the ON state from timing T3 to timing T4. When the first switch SW1 and the fourth switch SW4 are in the OFF state, the second transparent electrode layer 23 is connected to the ground level GND. When the second switch SW2 and the third switch SW3 are in the ON state, the first transparent electrode layer 22 is connected to the output level VD of the switching circuit 17.

[0070] When the first switch SW1 and the fourth switch SW4 are in the off state and the second switch SW2 and the third switch SW3 are in the on state, the first transparent electrode layer 22 is connected to the output level VD of the switching circuit 17 and the second transparent electrode layer 23 is connected to the ground level GND. When the second switch SW2 and the third switch SW3 are in the off state and the first switch SW1 and the fourth switch SW4 are in the on state, the second transparent electrode layer 23 is connected to the output level VD of the switching circuit 17 and the first transparent electrode layer 22 is connected to the ground level GND.

[0071] The timing control circuit 15 outputs an inversion control signal SIGR so that a period in which the output level VD of the switching circuit 17 is connected to the second transparent electrode layer 23 and a period in which the output level VD of the switching circuit 17 is connected to the first transparent electrode layer 22 are alternately repeated.

[0072] The timing control circuit 15 applies the voltage converted into an AC voltage by the output of the inverted control signal SIGR to the light controlling sheet 20 as a drive signal SVD through the current detection circuit 35. The timing control circuit 15 also applies the voltage converted into an AC voltage by the output of the inverted control signal SIGR to the light controlling sheet 20 as a repair signal SVR through the current detection circuit 35.

[0073] [Circuit configuration of timing control section] Next, a circuit configuration of an example of a timing control section included in the power supply circuit 10 will be described. 1, the timing control circuit 15 outputs an inverted clock signal CLK1 and a reference clock signal CLK2 to the clock generation circuit 18. The inverted clock signal CLK1 and the reference clock signal CLK2 are internal clock signals for generating the inverted control signal SIGR.

[0074] The clock generating circuit 18 generates a first detection clock signal SMP1 and a second detection clock signal SMP2 from the inverted clock signal CLK1 and the reference clock signal CLK2. The first detection clock signal SMP1 defines a sampling period for detecting a peak value of the detection current. The second detection clock signal SMP2 defines a sampling period for detecting a convergence value of the detection current.

[0075] As shown in FIG. 6, the inverted clock signal CLK1 changes from high level to low level at the inversion timing of the inversion control signal SIGR, and changes from low level to high level at the next inversion timing. The reference clock signal CLK2 alternates between high level and low level at a period shorter than the inversion period of the inversion control signal SIGR. For example, the inverted control signal SIGR is generated by dividing the reference clock signal CLK2 by 4. The inverted control signal SIGR rises when the reference clock signal CLK2 falls. Also, the inverted control signal SIGR falls when the reference clock signal CLK2 falls.

[0076] The clock generating circuit 18 generates a latch output signal LTS1, a latch output inverted signal LTS2, a shift signal RMP1, a first detection clock signal SMP1, and a second detection clock signal SMP2.

[0077] The clock generating circuit 18 receives the inverted clock signal CLK1 as a data input and the reference clock signal CLK2 as a clock input, and generates a latch output signal LTS1 by latching the inverted clock signal CLK1 with the reference clock signal CLK2.

[0078] The clock generating circuit 18 generates the latch output inverted signal LTS2 by inverting the latch output signal LTS1. The clock generating circuit 18 generates the shift signal RMP1 by shifting the latch output signal LTS1 by a predetermined time shorter than 1 / 2 the period of the inverted clock signal CLK1. The shift amount of the shift signal RMP1 relative to the latch output signal LTS1 is, for example, three periods of the reference clock signal CLK2.

[0079] The clock generating circuit 18 generates a first detection clock signal SMP1 by logically multiplying the inverted clock signal CLK1 and the latch output inverted signal LTS2. The first detection clock signal SMP1 rises together with the rising edge of the inverted clock signal CLK1 and remains at a high level for a first sampling period TSM1, which is one period of the reference clock signal CLK2 and is shorter than half the period of the inverted clock signal CLK1.

[0080] The current detection circuit 35 regards the rising timing of the first detection clock signal SMP1 as the start of a sampling period for detecting a peak value, and the falling timing of the first detection clock signal SMP1 as the end of the sampling period for detecting a peak value.

[0081] The clock generating circuit 18 generates a second detection clock signal SMP2 by ANDing the inverted clock signal CLK1 and the shift signal RMP1. The second detection clock signal SMP2 maintains a high level for a second sampling period TSM2, which is one period of the reference clock signal CLK2 and is shorter than half the period of the inverted clock signal CLK1, prior to the falling edge of the inverted clock signal CLK1.

[0082] The current detection circuit 35 regards the rising timing of the second detection clock signal SMP2 as the start of a sampling period for detecting a convergence value, and the falling timing of the second detection clock signal SMP2 as the end of the sampling period for detecting a convergence value.

[0083] Then, the current detection circuit 35 detects the peak values ​​of the sensed currents IMA, IMB, IMC during the first sampling period TSM1 from the rising edge of the first detection clock signal SMP1. The fault determination circuit 32 determines that [B] reversal abnormality does not exist for the sensed currents IMA, IMC having peak values ​​larger than the first determination threshold Ith1. The range larger than the first determination threshold Ith1 is an example of a normal range. On the other hand, the fault determination circuit 32 determines that [B] reversal abnormality exists for the sensed current IMB having a peak value equal to or smaller than the first determination threshold Ith1. The first determination threshold Ith1 is an example of a first threshold.

[0084] Furthermore, the current detection circuit 35 detects the convergence values ​​of the sensed currents IMA, IMB, IMC during the second sampling period TSM2 from the rising edge of the second detection clock signal SMP2. The fault determination circuit 32 determines that [C] convergence abnormality does not exist for the sensed currents IMA, IMB having convergence values ​​equal to or less than the second determination threshold Ith2. The range equal to or less than the second determination threshold Ith2 is an example of a normal range. On the other hand, the fault determination circuit 32 determines that [C] convergence abnormality exists for the sensed current IMC having a convergence value greater than the second determination threshold Ith2. The second determination threshold Ith2 is an example of a second threshold.

[0085] [Functional configuration of the fault detection section] Next, a functional configuration of an example of a failure detection unit included in the power supply circuit 10 will be described. 1, the current detection circuit 35 detects at least one of the source current and the sink current as a detected current. The source current is a current flowing from the current detection circuit 35 to the light controlling sheet 20. The sink current is a current returning from the light controlling sheet 20 to the current detection circuit 35.

[0086] In order for the fault determination circuit 32 to determine the presence or absence of a system leakage current [A], the current detection circuit 35 detects the difference between the source current and the sink current relative to the other. In order for the fault determination circuit 32 to determine the presence or absence of an inversion abnormality [B], the current detection circuit 35 starts sampling the detection current from the rising edge of the first detection clock signal SMP1. Then, the current detection circuit 35 samples the detection current until the first sampling period TSM1 has elapsed, and detects a peak value from among the extracted detection current.

[0087] In order for the fault determination circuit 32 to determine the presence or absence of a convergence abnormality [C], the current detection circuit 35 starts sampling the detection current from the rising edge of the second detection clock signal SMP2. Then, the current detection circuit 35 samples the detection current until the second sampling period TSM2 has elapsed, and detects a convergence value from the extracted detection current.

[0088] For example, when the drive voltage generating circuit 16 includes an H-bridge circuit, the source current flows from the input terminal of the H-bridge circuit to the connection terminal between the first switch SW1 and the second switch SW2. The current detection circuit 35 detects the current flowing from the input terminal of the H-bridge circuit to the connection terminal between the first switch SW1 and the second switch SW2. When the drive voltage generating circuit 16 includes an H-bridge circuit, the sink current flows from the connection terminal between the third switch SW3 and the fourth switch SW4 to the output terminal of the H-bridge circuit. The current detection circuit 35 detects the current flowing from the connection terminal between the third switch SW3 and the fourth switch SW4 to the output terminal of the H-bridge circuit.

[0089] [A] The current detection circuit 35 simultaneously detects the source current and the sink current, and detects the difference between one of the source current and the sink current and the other. The fault determination circuit 32 determines whether the detected difference is greater than a predetermined third threshold value.

[0090] [B] The current detection circuit 35 has a sampling period of the source current designated by a first detection clock signal SMP1 input by the timing control circuit 15. The current detection circuit 35 detects a peak value from the source current during the first sampling period TSM1 designated by the first detection clock signal SMP1. The fault determination circuit 32 determines whether the detected peak value is greater than a predetermined first determination threshold Ith1 (see FIG. 6).

[0091] [C] The current detection circuit 35 has a source current sampling period designated by a second detection clock signal SMP2 input by the timing control circuit 15. The current detection circuit 35 detects a convergence value from the source current during the second sampling period TSM2 designated by the second detection clock signal SMP2. The fault determination circuit 32 determines whether the detected convergence value is greater than a predetermined second determination threshold Ith2 (see FIG. 6).

[0092] Even when an AC voltage is applied to the light controlling sheet 20, the current detection circuit 35 can detect the source current without changing the direction in which the source current flows. Also, the current detection circuit 35 can detect the sink current without changing the direction in which the sink current flows.

[0093] The clock generating circuit 18 may also shape the first detection clock signal SMP1 so that the first detection clock signal SMP1 rises with the falling edge of the inverted clock signal CLK1 and remains at a high level for a first sampling period TSM1. The current detection circuit 35 may receive the first detection clock signal SMP1 shaped in this way and detect a peak value of the sink current during a sampling period designated by the first detection clock signal SMP1. The fault determination circuit 32 may then determine whether the peak value of the sink current is greater than the first determination threshold Ith1. The power supply circuit 10 may also determine whether the peak value of the source current is greater than a predetermined first determination threshold Ith1 and whether the peak value of the sink current is greater than the first determination threshold Ith1.

[0094] The clock generating circuit 18 may also shape the second detection clock signal SMP2 so that the second detection clock signal SMP2 maintains a high level for a second sampling period TSM2 prior to the rising edge of the inverted clock signal CLK1. The current detection circuit 35 may receive the second detection clock signal SMP2 thus shaped and detect the convergence value of the sink current during the sampling period designated by the second detection clock signal SMP2. The fault determination circuit 32 may then determine whether the convergence value of the sink current is greater than a predetermined second determination threshold Ith2. The power supply circuit 10 may also determine whether the convergence value of the source current is greater than a predetermined second determination threshold Ith2 and whether the peak value of the sink current is greater than a predetermined second determination threshold Ith2.

[0095] [Example of fault detection unit configuration] Next, an example of the functional configuration of a failure detection unit included in the power supply circuit 10 will be described. 4, the power supply circuit 10 includes a first detection circuit 352, a second detection circuit 353, a difference detection circuit 354, a leakage current detection circuit 355, a first sampling circuit 356, and a first determination circuit 357. The power supply circuit 10 may further include a second sampling circuit 358 and a second determination circuit 359.

[0096] The first detection circuit 352, the second detection circuit 353, the difference detection circuit 354, the first sampling circuit 356, and the second sampling circuit 358 constitute the current detection circuit 35. The leakage current detection circuit 355, the first determination circuit 357, and the second determination circuit 359 constitute the fault determination circuit 32.

[0097] The first detection circuit 352, the second detection circuit 353, the difference detection circuit 354, and the leakage current detection circuit 355 detect the difference between one of the source current and the sink current and the other in order for the power supply circuit 10 to determine the presence or absence of a system leakage current [A], and output whether or not the detected difference is greater than a predetermined threshold value.

[0098] The first detection circuit 352 detects a source current entering the first transparent electrode layer 22 and a sink current leaving the first transparent electrode layer 22. The second detection circuit 353 detects a source current entering the second transparent electrode layer 23 and a sink current leaving the second transparent electrode layer 23.

[0099] The difference detection circuit 354 detects the difference between the source current entering the first transparent electrode layer 22 and the sink current exiting from the second transparent electrode layer 23. The difference detection circuit 354 detects the difference between the source current entering the second transparent electrode layer 23 and the sink current exiting from the first transparent electrode layer 22.

[0100] The leakage current detection circuit 355 compares the detection result of the difference detection circuit 354 with a predetermined threshold value and determines whether the detection result of the difference detection circuit 354 is greater than the predetermined threshold value. When the leakage current detection circuit 355 determines that the detection result of the difference detection circuit 354 is greater than the predetermined threshold value, it outputs [A] that a system leakage current has occurred. Conversely, when the leakage current detection circuit 355 determines that the detection result of the difference detection circuit 354 is equal to or less than the predetermined threshold value, it outputs [A] that a system leakage current has not occurred.

[0101] The first detection circuit 352 and the first sampling circuit 356 detect a peak voltage equivalent to the peak value from the temporal change in the detection current in order to determine the presence or absence of an abnormality during inversion [B] in the power supply circuit 10. For example, while the first detection clock signal SMP1 input to the clock generation circuit 18 is at a high level, the first sampling circuit 356 detects the peak voltage during that period from the detection current of the first detection circuit 352.

[0102] The first determination circuit 357 compares the peak value detected by the first sample extraction circuit 356 with the first determination threshold Ith1, and determines whether or not the peak value detected by the first sample extraction circuit 356 is greater than the first determination threshold Ith1. When the first determination circuit 357 determines that the peak value detected by the first sample extraction circuit 356 is greater than the first determination threshold Ith1, it outputs [B] that an inversion abnormality has occurred. Conversely, when the first determination circuit 357 determines that the peak value detected by the first sample extraction circuit 356 is equal to or less than the first determination threshold Ith1, it outputs [B] that an inversion abnormality has not occurred.

[0103] The first detection circuit 352 and the first sampling circuit 356 detect a convergence value from a temporal change in the detection current in order to determine the presence or absence of a convergence abnormality [C] in the power supply circuit 10. For example, during a period in which the second detection clock signal SMP2 input to the clock generation circuit 18 is at a high level, the first sampling circuit 356 detects a convergence value for that period from the detection current of the first detection circuit 352.

[0104] The first judgment circuit 357 compares the convergence value detected by the first sampling circuit 356 with the second judgment threshold Ith2, and judges whether or not the convergence value detected by the first sampling circuit 356 is greater than the second judgment threshold Ith2. When the first judgment circuit 357 judges that the convergence value detected by the first sampling circuit 356 is greater than the second judgment threshold Ith2, it outputs [C] that a convergence anomaly has occurred. Conversely, when the first judgment circuit 357 judges that the convergence value detected by the first sampling circuit 356 is equal to or less than the second judgment threshold Ith2, it outputs [C] that a convergence anomaly has not occurred.

[0105] The second detection circuit 353 and the second sampling circuit 358 may also detect a peak value from a change over time in the detection current in order to determine the presence or absence of an abnormality during reversal [B] in the power supply circuit 10. The second determination circuit 359 may also compare the peak value detected by the second sampling circuit 358 with the first determination threshold Ith1, and determine whether or not the peak value detected by the second sampling circuit 358 is greater than the first determination threshold Ith1.

[0106] The configuration further performing detection of inversion abnormality [B] by the second sampling circuit 358 and the second judgment circuit 359 increases the accuracy of the detection results compared to detection only by the first sampling circuit 356 and the first judgment circuit 357.

[0107] The second detection circuit 353 and the second sampling circuit 358 may also detect a convergence value from a temporal change in the detection current in order to determine the presence or absence of a convergence abnormality [C] in the power supply circuit 10. The second determination circuit 359 may also compare the convergence value detected by the second sampling circuit 358 with a second determination threshold Ith2, and determine whether or not the convergence value detected by the second sampling circuit 358 is greater than the second determination threshold Ith2.

[0108] The configuration that further detects convergence anomalies [C] by the second sampling circuit 358 and the second judgment circuit 359 increases the accuracy of the detected results related to convergence anomalies [C] compared to detection only by the second sampling circuit 358 and the second judgment circuit 359.

[0109] [Example of circuit configuration for fault detection section] Next, an example of the circuit configuration of the failure detection unit included in the power supply circuit 10 will be described. The circuit configuration example [B] for detecting an inversion anomaly can be realized by changing the difference detection circuit 354 in the circuit configuration example [A] for detecting a system leakage current to a circuit configuration that extracts a sample from the detected current. The circuit configuration example [C] for detecting a convergence anomaly can also be realized by changing the difference detection circuit 354 in the circuit configuration example [A] for detecting a system leakage current to a circuit configuration that extracts a sample from the detected current.

[0110] That is, an example of the first sampling circuit 356 and the first determination circuit 357 can be realized by changing the circuit configuration of the difference detection circuit 354 and the earth leakage detection circuit 355 to one that extracts a sample from the detected current. The second sampling circuit 358 and the second determination circuit 359 can also be realized by changing the circuit configuration of the difference detection circuit 354 and the earth leakage detection circuit 355 to one that extracts a sample from the detected current.

[0111] Therefore, the following mainly describes examples of first detection circuit 352, second detection circuit 353, difference detection circuit 354, and earth leakage detection circuit 355. Then, for first sampling circuit 356, first determination circuit 357, second sampling circuit 358, and second determination circuit 359, differences from difference detection circuit 354 and earth leakage detection circuit 355 will be mainly described.

[0112] 5, the first detection circuit 352 is a differential amplifier circuit. The first detection circuit 352 includes a first shunt resistor 2R0, a first operational amplifier 20P1, and resistors 2R1, 2R2, 2R3, and 2R4.

[0113] The inverting input terminal of the first operational amplifier 20P1 is connected to the first transparent electrode layer 22 via a first shunt resistor 2R0 and a resistor 2R1. The inverting input terminal of the first operational amplifier 20P1 is also connected to the output terminal of the first operational amplifier 20P1 via a resistor 2R2. The non-inverting input terminal of the first operational amplifier 20P1 is connected to the first transparent electrode layer 22 via a resistor 2R3. The non-inverting input terminal of the first operational amplifier 20P1 is also connected to a reference voltage via a resistor 2R4.

[0114] The first detection circuit 352 amplifies the voltage of the first shunt resistor 2R0 by a predetermined amplification factor to a first output voltage. The first detection circuit 352 outputs the first output voltage to the differential detection circuit 354. An output terminal 352A of the first detection circuit 352 is connected to the differential detection circuit 354 and a first sampling circuit 356.

[0115] The second detection circuit 353 is a differential amplifier circuit and includes a second shunt resistor 3R0, a second operational amplifier 30P1, and resistors 3R1, 3R2, 3R3, and 3R4.

[0116] The inverting input terminal of the second operational amplifier 30P1 is connected to the second transparent electrode layer 23 via a second shunt resistor 3R0 and a resistor 3R1. The inverting input terminal of the second operational amplifier 30P1 is also connected to the output terminal of the second operational amplifier 30P1 via a resistor 3R2. The non-inverting input terminal of the second operational amplifier 30P1 is connected to the second transparent electrode layer 23 via a resistor 3R3. The non-inverting input terminal of the second operational amplifier 30P1 is also connected to a reference voltage via a resistor 3R4.

[0117] The second detection circuit 353 amplifies the voltage of the second shunt resistor 3R0 by a predetermined amplification factor to a second output voltage. The second detection circuit 353 outputs the second output voltage to the differential detection circuit 354. An output terminal 353A of the second detection circuit 353 is connected to the differential detection circuit 354 and a second sampling circuit 358.

[0118] The difference detection circuit 354 is a differential amplifier circuit and includes a third operational amplifier 40P1, and resistors 4R1, 4R2, 4R3, and 4R4.

[0119] The inverting input terminal of the third operational amplifier 40P1 is connected to the output terminal of the second detection circuit 353 via a resistor 4R1. The inverting input terminal of the third operational amplifier 40P1 is also connected to the output terminal of the third operational amplifier 40P1 via a resistor 4R2. The non-inverting input terminal of the third operational amplifier 40P1 is connected to the output terminal of the first detection circuit 352 via a resistor 4R3. The non-inverting input terminal of the third operational amplifier 40P1 is also connected to a reference voltage via a resistor 3R4.

[0120] The difference detection circuit 354 amplifies the difference between the output voltage of the first detection circuit 352 and the output voltage of the second detection circuit 353 by a predetermined amplification factor to generate a difference voltage. The difference detection circuit 354 outputs the difference voltage to the leakage current detection circuit 355.

[0121] The leakage current detection circuit 355 is a comparison circuit that compares the output voltage of the difference detection circuit 354 with a leakage current reference voltage, which is a predetermined reference voltage. The leakage current detection circuit 355 includes a fourth operational amplifier 50P1, a resistor 5R1, a resistor 5R2, a variable resistor 5R3, and a resistor 5R4.

[0122] Resistor 5R2, variable resistor 5R3, and resistor 5R4 form a series resistor divider circuit. The output voltage of the resistor divider circuit varies depending on the resistance value of variable resistor 5R3. The output voltage of the resistor divider circuit is a leakage reference voltage and functions as a threshold for determining whether or not there is a leakage current in the system [A].

[0123] The inverting input terminal of the fourth operational amplifier 50P1 is connected to the connection terminal of the resistor 5R2 and the variable resistor 5R3. The non-inverting input terminal of the fourth operational amplifier 50P1 is connected to the output terminal of the difference detection circuit 354. The non-inverting input terminal of the fourth operational amplifier 50P1 is connected to the output terminal of the difference detection circuit 354 via the resistor 5R1.

[0124] The leakage current detection circuit 355 amplifies the difference between the output voltage of the difference detection circuit 354 and the leakage current reference voltage. When the output voltage of the difference detection circuit 354 is higher than the leakage current reference voltage, the leakage current detection circuit 355 outputs a high-level voltage. When the output voltage of the difference detection circuit 354 is lower than the leakage current reference voltage, the leakage current detection circuit 355 outputs a low-level voltage. When the leakage current detection circuit 355 outputs a high-level voltage, the fault determination circuit 32 determines that [A] system leakage has occurred. Conversely, when the leakage current detection circuit 355 outputs a low-level voltage, the fault determination circuit 32 determines that [A] system leakage has not occurred.

[0125] The first sampling circuit 356 and the second sampling circuit 358 each include a sample-and-hold circuit. The sample-and-hold circuits receive the first detection clock signal SMP1 and the second detection clock signal SMP2 as separate input clocks. The sample-and-hold circuits include a hold capacitor for holding the detection current. When the first detection clock signal SMP1 is at a high level, the sample-and-hold circuit holds, as a peak voltage, a peak value among the samples during the period when the first detection clock signal SMP1 is at a high level. When the second detection clock signal SMP2 is at a high level, the sample-and-hold circuit holds, as a convergence voltage, a convergence value among the samples during the period when the second detection clock signal SMP2 is at a high level.

[0126] The first determination circuit 357 and the second determination circuit 359 each include a comparison circuit. The comparison circuit of first determination circuit 357 is connected to the output terminal of first sampling circuit 356. The comparison circuit of first determination circuit 357 receives as input from first sampling circuit 356 the peak voltage held by first sampling circuit 356. The comparison circuit of first determination circuit 357 receives as input from first sampling circuit 356 the convergence voltage held by first sampling circuit 356.

[0127] The comparison circuit of the second judgment circuit 359 is connected to the output terminal of the second sampling circuit 358. The comparison circuit of the second judgment circuit 359 receives as input from the second sampling circuit 358 the peak voltage held by the second sampling circuit 358. The comparison circuit of the second judgment circuit 359 receives as input from the second sampling circuit 358 the convergence voltage held by the second sampling circuit 358.

[0128] The comparator circuit holds the peak voltage detected during the current first sampling period TSM1 until the next first sampling period TSM1 starts. After the current first sampling period TSM1 has elapsed and before the next first sampling period TSM1 starts, the comparator circuit amplifies the difference between the peak voltage detected during the current first sampling period TSM1 and a first fault reference voltage, which is a predetermined reference voltage. The first fault reference voltage used to generate the difference functions as a first determination threshold Ith1 for detecting an inversion anomaly [B].

[0129] The comparison circuit outputs a high-level voltage when the convergence voltage is higher than the first fault reference voltage. The comparison circuit outputs a low-level voltage when the peak voltage is lower than the first fault reference voltage. When the comparison circuit of the first judgment circuit 357 and the comparison circuit of the second judgment circuit 359 both output high-level voltages, the fault judgment circuit 32 judges that [B] inversion anomaly has not occurred. On the other hand, when the comparison circuit of the first judgment circuit 357 or the comparison circuit of the second judgment circuit 359 output low-level voltages, the fault judgment circuit 32 judges that [B] inversion anomaly has occurred.

[0130] The comparator circuit holds the convergence voltage detected in the current second sampling period TSM2 until the next second sampling period TSM2 starts. After the current second sampling period TSM2 has elapsed and before the next second sampling period TSM2 starts, the comparator circuit amplifies the difference between the convergence value detected in the current second sampling period TSM2 and a second fault reference voltage, which is a predetermined reference voltage. The second fault reference voltage used to generate the difference functions as a second determination threshold Ith2 for detecting a convergence abnormality [C].

[0131] The comparison circuit outputs a high-level voltage when the convergence value is higher than the second fault reference voltage. The comparison circuit outputs a low-level voltage when the convergence value is lower than the second fault reference voltage. When the comparison circuit of the first judgment circuit 357 and the comparison circuit of the second judgment circuit 359 both output a high-level voltage, the fault judgment circuit 32 judges that [C] a convergence anomaly has occurred. On the other hand, when the comparison circuit of the first judgment circuit 357 or the comparison circuit of the second judgment circuit 359 output a low-level voltage, the fault judgment circuit 32 judges that [C] a convergence anomaly has not occurred.

[0132] [Operation of power supply circuit 10] The power supply circuit 10 performs the above-mentioned processes of detecting a peak value, detecting a convergence value, judging the presence or absence of a fault based on a comparison between the peak value and a first judgment threshold Ith1, and judging the presence or absence of a fault based on a comparison between the convergence value and a second judgment threshold Ith2. The power supply circuit 10 includes a circuit that processes various processes by software. The power supply circuit 10 may include dedicated hardware such as an application specific integrated circuit (ASIC) that executes at least a part of the various processes. The power supply circuit 10 may also be configured as a circuit that includes one or more dedicated hardware circuits such as an ASIC, one or more processors that operate according to a computer program, or a combination of these. In the following, an example will be described in which a processor included in the power supply circuit 10 reads and executes a drive program stored in a readable medium included in the power supply circuit 10 to perform various processes.

[0133] 7, the processor of the power supply circuit 10 receives an operation instruction to drive the light controlling sheet 20, and drives the first boost circuit 12, the control power supply creating circuit 14, the timing control circuit 15, the drive voltage generating circuit 16, and the drive circuit 31. As a result, the processor of the power supply circuit 10 supplies the drive signal SVD, which is inverted in polarity based on the inversion control signal SIGR, to the light controlling sheet 20 (step S11).

[0134] The processor of the power supply circuit 10 drives the second boost circuit 13, the switching circuit 17, and the clock generation circuit 18 while supplying the drive signal SVD, and causes the fault determination circuit 32 to determine the presence or absence of a fault at a predetermined control period (step S12). That is, the processor of the power supply circuit 10 causes the fault determination circuit 32 to determine whether any of [A] system leakage, [B] inversion anomaly, and [C] convergence anomaly has occurred. The processor of the power supply circuit 10 continues to supply the drive signal SVD until a fault is detected by the fault determination circuit 32 (NO in step S12).

[0135] When the fault determination circuit 32 detects the [A] system leakage, the processor of the power supply circuit 10 causes the fault state display circuit 33 to display to the outside the fact that the [A] system leakage has occurred through the output of the fault determination circuit 32. When the fault determination circuit 32 detects the [B] reversal anomaly, the processor of the power supply circuit 10 causes the fault state display circuit 33 to display to the outside the fact that the [B] reversal anomaly has occurred through the output of the fault determination circuit 32 (step S18).

[0136] Next, when the fault determination circuit 32 detects [A] a system leakage current, the processor of the power supply circuit 10 controls the timing control circuit 15 and the drive voltage generation circuit 16 to stop the application of the drive signal SVD. When the fault determination circuit 32 detects [B] an inversion abnormality, the processor of the power supply circuit 10 controls the timing control circuit 15 and the drive voltage generation circuit 16 to stop the application of the drive signal SVD (step S19).

[0137] As a result, the processor of the power supply circuit 10 stops the supply of the drive signal SVD to the light controlling sheet 20 when at least one of [A] a system leakage current and [B] an inversion abnormality is detected.

[0138] On the other hand, when the fault determination circuit 32 detects only the convergence anomaly [C], the processor of the power supply circuit 10 causes the fault state display circuit 33 to externally display the fact that the convergence anomaly [C] has occurred (step S13). Also, the processor of the power supply circuit 10 clears an internal timer for timing the supply time Ta of the repair signal SVR (step S14).

[0139] The fault determination circuit 32 outputs a repair request signal SIGS and controls the switching circuit 17 so that the signal supplied to the light controlling sheet 20 is switched from the drive signal SVD to the repair signal SVR (step S15). In addition, the processor of the power supply circuit 10 starts to measure the supply time Ta of the repair signal SVR with an internal timer together with the output of the repair request signal SIGS by the fault determination circuit 32 (step S16). At this time, the display by the above-mentioned fault state display circuit 33 functions as a notification of the application of the repair voltage VLR, which is higher than the drive voltage VLD.

[0140] Next, the processor of the power supply circuit 10 continues to supply the repair signal SVR to the fault determination circuit 32 until the supply time Ta of the repair signal SVR elapses the set time Tp (NO in step S17). On the other hand, when the supply time Ta of the repair signal SVR reaches the set time Tp, the processor of the power supply circuit 10 causes the fault determination circuit 32 to stop outputting the repair request signal SIGS. Note that the set time Tp is a time obtained by testing or simulation as the time during which the supply of the repair signal SVR can break the micro-short circuit. Also, the set time Tp is a time that is preset in the processor of the power supply circuit 10. Then, the processor of the power supply circuit 10 switches the signal supplied to the light controlling sheet 20 from the repair signal SVR to the drive signal SVD (YES in step S17). As a result, the processor of the power supply circuit 10 supplies a repair signal SVR, and breaks the micro-short circuit that has occurred in the light controlling sheet 20.

[0141] [Decision threshold] Next, the change in the detection current over time will be explained using the results of a circuit simulation. Figure 8 shows the load circuit used in the circuit simulation to obtain the change in the detection current over time. The load circuit shows an equivalent circuit including the light-controlling sheet 20 and the resistance of the transmission line that connects the light-controlling sheet 20 to the power supply circuit 10.

[0142] 8, the load circuit includes a first terminal PaS and a second terminal PbS. The first terminal PaS is, for example, a terminal constituting the light controlling sheet 20, and is a terminal that connects the first transparent electrode layer 22 to the drive circuit 31. The second terminal PbS is, for example, a terminal constituting the light controlling sheet 20, and is a terminal that connects the second transparent electrode layer 23 to the drive circuit 31.

[0143] The load circuit includes a first wiring resistor R1S and a second wiring resistor R5S. The first wiring resistor R1S is a wiring resistor that connects the first transparent electrode layer 22 to the drive circuit 31. The second wiring resistor R5S is a wiring resistor that connects the second transparent electrode layer 23 to the drive circuit 31.

[0144] The load circuit includes a first ground resistor R12S and a second ground resistor R13S. The first ground resistor R12S is a resistor that connects the first transparent electrode layer 22 to a ground potential. The second ground resistor R13S is a resistor that connects the second transparent electrode layer 23 to a ground potential. The first ground resistor R12S and the second ground resistor R13S are generated by moisture or foreign matter that connects the transparent electrode layers 22 and 23 separately in the surrounding environment where the light control sheet 20 is installed.

[0145] The load circuit includes a first contact resistor R2S and a second contact resistor R6S. The first contact resistor R2S is a resistor connected in series to the first wiring resistor R1S and is a contact resistance between the first transparent electrode layer 22 and the wiring. The second contact resistor R6S is a resistor connected in series to the second wiring resistor R5S and is a contact resistance between the second transparent electrode layer 23 and the wiring.

[0146] The load circuit includes a first input end electrode resistance R3S and a first peripheral electrode resistance R4S. The first input end electrode resistance R3S and the first peripheral electrode resistance R4S are each resistances in a portion of the first transparent electrode layer 22. The first input end electrode resistance R3S and the first peripheral electrode resistance R4S form a series circuit that is an equivalent circuit of the first transparent electrode layer 22.

[0147] The load circuit includes a second input end electrode resistance R7S and a second peripheral electrode resistance R8S. The second input end electrode resistance R7S and the second peripheral electrode resistance R8S are each resistances in parts of the second transparent electrode layer 23. The second input end electrode resistance R7S and the second peripheral electrode resistance R8S form a series circuit that is an equivalent circuit of the second transparent electrode layer 23.

[0148] The load circuit includes an input end liquid crystal capacitance C1S, an internal liquid crystal capacitance C2S, and an edge liquid crystal capacitance C3S. The load circuit includes an input end liquid crystal resistance R9S, an internal liquid crystal resistance R10S, and an edge liquid crystal resistance R11S.

[0149] The input end liquid crystal capacitance C1S and the input end liquid crystal resistance R9S are a parallel circuit connecting the first transparent electrode layer 22 and the second transparent electrode layer 23, and connect the first contact resistance R2S and the second contact resistance R6S. The internal liquid crystal capacitance C2S and the internal liquid crystal resistance R10S are a parallel circuit connecting the first transparent electrode layer 22 and the second transparent electrode layer 23, and connect the first input end electrode resistance R3S and the second input end electrode resistance R7S. The edge liquid crystal capacitance C3S and the edge liquid crystal resistance R11S are a parallel circuit connecting the first transparent electrode layer 22 and the second transparent electrode layer 23, and connect the first peripheral electrode resistance R4S and the second peripheral electrode resistance R8S.

[0150] Using the above-mentioned equivalent circuit, a square wave was input between the first terminal PaS and the second terminal PbS, and the current flowing through the first wiring resistor R1S was set as the detection current, and the change in the detection current over time was obtained by circuit simulation. At this time, the driving signal SVD, which is a square wave, was set to 0V at the low level, 80V at the high level, and 50Hz (period TS = 20msec) at the frequency. In addition, the following reference values ​​were used as the characteristic values ​​of the circuit elements that make up the equivalent circuit. First wiring resistance R1S: 5Ω Second wiring resistance R5S: 5Ω 1st grounding resistance R12S: 500kΩ 2nd grounding resistance R13S: 500kΩ 1st contact resistance R2S: 20Ω 2nd contact resistance R6S: 20Ω First input electrode resistance R3S: 10Ω First peripheral electrode resistance R4S: 10Ω Second input terminal electrode resistance R7S: 10Ω Second peripheral electrode resistance R8S: 10Ω Input end LCD capacitance C1S: 10μF Internal liquid crystal capacitance C2S: 10μF Edge liquid crystal capacitance C3S: 10μF Input end liquid crystal resistance R9S: 500kΩ Internal LCD resistor R10S: 500kΩ Edge liquid crystal resistor R11S: 500kΩ

[0151] Fig. 9 shows the change over time of the detection current when the resistance value of the first contact resistor R2S is changed from the reference value to 100 Ω. That is, Fig. 9 shows the change over time of the detection current when the transmission line resistance increases [B].

[0152] As shown by the solid line in Fig. 9, when the resistance value of the first contact resistor R2S is a reference value, the sense current has a peak current value Ipk immediately after the inversion of the drive signal SVD. As shown by the dashed line in Fig. 9, when the resistance value of the first contact resistor R2S is 50Ω, which is higher than the reference value, the sense current in the inversion period TS has a lower peak current value immediately after the inversion of the drive signal SVD than when the resistance value of the first contact resistor R2S is the reference value. Also, as shown by the two-dot chain line in Fig. 9, when the resistance value of the first contact resistor R2S is 100Ω, which is even higher, the sense current has an even lower peak current value immediately after the inversion of the drive signal SVD.

[0153] 10, the peak current value Ipk of the detected current decreases as the resistance value of the first contact resistance R2S increases. In other words, an increase in the resistance value of the transmission member, such as the first contact resistance R2S, or an increase in the contact resistance value between the transmission members appears as a decrease in the peak value of the source current or a decrease in the peak value of the sink current.

[0154] The change in the sensed current over time when the capacitance value of the input end liquid crystal capacitance C1S was changed from 0 μF to the reference value also showed a similar tendency to the change in the resistance value of the first contact resistor R2S. In other words, the lower the capacitance value of the input end liquid crystal capacitance C1S, the lower the peak value of the sensed current immediately after the inversion of the drive signal SVD. This means that with regard to the capacitance value of the liquid crystal, a decrease in capacitance value appears as a decrease in the peak value of the source current or a decrease in the peak value of the sink current.

[0155] From the above, if the lower limit of the peak value when the resistance value in the transmission member, the contact resistance value between the transmission members, and the capacitance value of the liquid crystal are normal is set to the first judgment threshold value Ith1, it can be said that [B] whether or not an abnormality has occurred during inversion can be detected.

[0156] Fig. 11 shows the change in the detection current over time when the resistance value of the edge liquid crystal resistor R11S is changed from 0 Ω to the reference value. That is, Fig. 11 shows the change in the detection current over time when a micro-short circuit occurs [C].

[0157] As shown by the solid line in Fig. 11, when the resistance value of the edge liquid crystal resistor R11S is 0Ω, the detection current has an ultimate current value Isa just before the inversion of the drive signal SVD. As shown by the dashed line in Fig. 10, when the resistance value of the edge liquid crystal resistor R11S is 50Ω, which is higher than 0Ω, the detection current has an ultimate current value lower than that when the resistance value of the edge liquid crystal resistor R11S is 0Ω just before the inversion of the drive signal SVD. Also, as shown by the two-dot chain line in Fig. 11, when the resistance value of the edge liquid crystal resistor R11S is an even higher reference value, the detection current has an even lower ultimate current value just before the inversion of the drive signal SVD.

[0158] As shown in Fig. 12, the attained current value Isa of the detection current is lower as the resistance value of the edge liquid crystal resistor R11S is higher. In other words, the presence of a micro-short circuit, such as the edge liquid crystal resistor R11S, appears as an increase in the convergence value of the source current or an increase in the convergence value of the sink current.

[0159] From the above, it can be said that if the lower limit of the convergence value when a micro-short circuit is observed between the first transparent electrode layer 22 and the second transparent electrode layer 23 is set to the second judgment threshold Ith2, it is possible to detect whether or not an abnormality has occurred during reversal [C].

[0160] Fig. 13 shows the change over time in the detection current when the resistance value of the second ground resistor R13S is changed from 100 Ω to the reference value to 100 Ω. That is, Fig. 13 shows the change over time in the detection current when the transparent electrode layer is grounded.

[0161] As shown in Figure 13, when the resistance value of the second grounding resistor R13S is 100 Ω and when the resistance value of the second grounding resistor R13S is the reference value, they exhibit peak current values ​​that are equal to each other, and also have reached current values ​​Isa that are equal to each other.

[0162] From the above, it can be said that, whether the first transparent electrode layer 22 is grounded or the second transparent electrode layer 23 is grounded, the ground faults that occur separately do not affect the fault judgment results based on the peak value or the fault judgment results based on the convergence value.

[0163] According to the above embodiment, the following effects can be obtained. (1) The peak value of the detection current flowing between the first transparent electrode layer 22 and the second transparent electrode layer 23 being equal to or less than the first judgment threshold Ith1 is detected as an inversion abnormality [B]. As a result, a fault resulting from the peak value of the detection current being equal to or less than the first judgment threshold Ith1, that is, an increase in the contact resistance between each of the transparent electrode layers 22, 23 and the wiring is detected as an inversion abnormality [B]. Alternatively, a decrease in the capacitance of the liquid crystal compound is detected as an inversion abnormality [B].

[0164] (2) The fact that the convergence value of the detection current flowing between the first transparent electrode layer 22 and the second transparent electrode layer 23 is greater than the second judgment threshold Ith2 is detected as a convergence abnormality [C]. As a result, a malfunction resulting from the convergence value of the detection current being greater than the second judgment threshold Ith2, that is, a micro-short circuit between the transparent electrode layers 22 and 23 is detected as a malfunction of the light control sheet as a convergence abnormality [C].

[0165] From the above, it becomes easy to identify, for example, the contact portion between the transparent electrode layers 22, 23 and the wiring as the portion where the failure has occurred, the liquid crystal compound as the portion where the failure has occurred, or the gap between the transparent electrode layers 22, 23 as the portion where the failure has occurred. As a result, it is possible to assist in identifying the portion where the failure has occurred in the light controlling sheet 20.

[0166] (3) The light control layer 21, which functions as a capacitance, passes a current that rises sharply when the driving voltage VLD is applied, and then passes a current that decays exponentially. In this regard, the start of the first sampling period TSM1 is synchronized with the polarity reversal of the driving voltage VLD. This determines the first sampling period TSM1 suitable for detecting a peak value. The end of the second sampling period TSM2 is also synchronized with the polarity reversal of the driving voltage VLD. This determines the second sampling period TSM2 suitable for detecting a convergence value. Then, a peak value is detected for the sensed current in the first sampling period, and a convergence value is detected for the sensed current in the second sampling period. This allows both the peak value and the convergence value to be detected with high accuracy.

[0167] (4) As described above, the [B] inversion abnormality is caused by an increase in the contact resistance value or a decrease in the capacitance of the liquid crystal compound. An increase in the contact resistance value or a decrease in the capacitance of the liquid crystal compound requires repair of the connection structure or replacement of the light controlling sheet 20 itself. In this regard, when the failure determination circuit 32 detects the [B] inversion abnormality, the power supply circuit 10 stops supplying the drive signal SVD. This makes it easy to prompt repair of the connection structure between the connection terminal and the wiring, or replacement of the light controlling sheet 20 itself.

[0168] (5) As described above, the [C] convergence anomaly is caused by a micro-short circuit between the transparent electrode layers 22 and 23. The micro-short circuit between the transparent electrode layers 22 and 23 can be blown by applying a repair voltage VLR, which is higher than the driving voltage VLD, between the transparent electrode layers 22 and 23. In this regard, when the fault determination circuit 32 detects the [C] convergence anomaly, the power supply circuit 10 starts supplying a repair signal SVR. This makes it possible to perform repairs appropriate to the fault in the light control sheet so that the micro-short circuit is blown.

[0169] (6) The light control layer 21, which functions as a capacitive element, passes a current that rises sharply when the driving voltage VLD is applied, and then passes a current that decays exponentially. Here, an increase in the contact resistance between the transparent electrode layers 22, 23 and the wiring lowers the peak value after the sharp rise in the detection current and slows the rate at which the current decays from the peak. Also, a micro-short circuit between the transparent electrode layers 22, 23 increases the convergence value to which the decay converges.

[0170] In this regard, a peak value derived from the contact resistance value is identified from the waveform of the current flowing between the transparent electrode layers 22 and 23. When the identified peak value is equal to or less than the first determination threshold value Ith1, it is detected as an increase in the contact resistance value. This makes it possible to identify the contact area between the transparent electrode layers 22 and 23 and the wiring as the location where the failure has occurred.

[0171] (7) In addition, a convergence value derived from the resistance value between the transparent electrode layers 22 and 23 is identified from the current waveform. Then, the presence of a micro-short circuit is detected when the identified convergence value is greater than the second determination threshold value Ith2. This makes it possible to identify the presence of a fault occurrence site between the transparent electrode layers 22 and 23.

[0172] The above embodiment can be modified as follows. [External power supply] When the supply voltage of the external power supply 50 is a DC voltage of 24 V, the transformer circuit 11 converts the DC voltage to the input level of the control power supply generating circuit 14. The transformer circuit 11 outputs the converted DC voltage to each of the first boost circuit 12, the second boost circuit 13, and the control power supply generating circuit 14. Note that when the output voltage of the external power supply 50 is the input level of the boost circuit and the control power supply generating circuit 14, the transformer circuit 11 may be omitted, and the first boost circuit 12, the second boost circuit 13, and the control power supply generating circuit 14 may each be connected to the external power supply 50.

[0173] [Timing control circuit 15] The timing control circuit 15 uses a clock signal to generate the inversion control signal SIGR to align the polarity inversion timing of the drive voltage generation circuit 16 with the start of the first sampling period TSM1. On the other hand, the alignment of the polarity inversion timing of the drive voltage generation circuit 16 with the start of the first sampling period TSM1 can also be performed based on monitoring of the drive signal SVD by the clock generation circuit 18. That is, the clock generation circuit 18 may detect the timing of a zero cross in the drive signal SVD and align the detected timing with the start of the first sampling period TSM1.

[0174] The timing control circuit 15 uses a clock signal to generate the inversion control signal SIGR to align the polarity inversion timing of the drive voltage generation circuit 16 with the end of the second sampling period TSM2. On the other hand, the alignment of the polarity inversion timing of the drive voltage generation circuit 16 with the end of the second sampling period TSM2 can also be performed based on monitoring of the drive signal SVD by the clock generation circuit 18. That is, the clock generation circuit 18 may detect the timing of a zero cross in the drive signal SVD and align the detected timing with the end of the second sampling period TSM2.

[0175] [Repair signal SVR] The power supply circuit 10 may change the repair signal SVR into a DC voltage signal. For example, the fault determination circuit 32 may input a repair request signal SIGS to the timing control circuit 15 for a predetermined time each time a convergence abnormality [C] is detected. The timing control circuit 15 may stop outputting the inversion control signal SIGR when it receives the repair request signal SIGS. The drive voltage generation circuit 16 may output a DC voltage signal as the repair signal SVR when the input of the inversion control signal SIGR is stopped. The current detection circuit 35 continues to apply a repair voltage VLR to the short-circuited minute portion for a predetermined time as the supply of the DC voltage signal. This allows the insulation of the short-circuited minute portion to be performed in a short time compared to the supply of the repair signal SVR, which repeats polarity inversion.

[0176] For example, the fault determination circuit 32 may input a repair request signal SIGS to the drive voltage generation circuit 16 for a predetermined time each time a convergence abnormality [C] is detected. When the drive voltage generation circuit 16 receives the repair request signal SIGS, it may stop processing based on the inversion control signal SIGR and prioritize processing based on the repair request signal SIGS. The processing based on the repair request signal SIGS outputs the repair voltage VLR for a predetermined time. The current detection circuit 35 continues to apply the repair voltage VLR to the short-circuited minute portion for a predetermined time as a supply of a DC voltage signal. This allows the insulation of the short-circuited minute portion to be performed in a short time compared to the supply of a repair signal SVR in which the repair voltage VLR is repeatedly inverted.

[0177] [Determining whether repair is possible] The processor of the power supply circuit 10 may determine whether or not repair by supplying the repair signal SVR is possible based on the number of times the repair signal SVR is supplied. When the processor of the power supply circuit 10 determines that repair by supplying the repair signal SVR is impossible, the processor may cause the fault condition display circuit 33 to display the fact that repair by supplying the repair signal SVR is impossible.

[0178] According to this, when the application of the repair voltage VLR is not able to repair the micro-short circuit, the user can understand that the application of the repair voltage VLR is not able to repair the micro-short circuit, and therefore the user is prevented from unnecessarily repeating the application of the high-voltage repair voltage VLR.

[0179] For example, the processor of the power supply circuit 10 may count up the number of times the repair request signal SIGS is output when the previous repair request signal SIGS and the current repair request signal SIGS are consecutive in the fault determination cycle. That is, the processor of the power supply circuit 10 may count up the number of times the repair request signal SIGS is output when a fault is detected each time step S12 is executed. The processor of the power supply circuit 10 may determine that repair by supplying the repair signal SVR is possible until the number of times the repair request signal SIGS is output reaches a predetermined number. On the other hand, the processor of the power supply circuit 10 may determine that repair by supplying the repair signal SVR is impossible when the number of times the repair request signal SIGS is output reaches a predetermined number, and may stop supplying the repair signal SVR and the drive signal SVD.

[0180] As a result, when the micro-short circuit cannot be repaired by applying the repair voltage VLR, the application of voltage between the transparent electrode layers 22, 23 is stopped, thereby preventing voltage from being continuously applied between the transparent electrode layers 22, 23 in the presence of the micro-short circuit.

[0181] The processor of the power supply circuit 10 may determine whether or not repair by supplying the repair signal SVR is possible based on the supply time of the repair voltage VLR. When the processor of the power supply circuit 10 determines that repair by supplying a repair signal is impossible, it may cause the fault condition display circuit 33 to display the fact that repair by supplying the repair signal SVR is impossible.

[0182] According to this, when the application of the repair voltage VLR is not able to repair the micro-short circuit, the user can understand that the application of the repair voltage VLR is not able to repair the micro-short circuit, and therefore the user is prevented from unnecessarily repeating the application of the high-voltage repair voltage VLR.

[0183] For example, the processor of the power supply circuit 10 may calculate the total time for which the repair signal SVR has been supplied when the previous repair request signal SIGS and the current repair request signal SIGS are consecutive in the fault determination cycle. That is, the processor of the power supply circuit 10 may calculate the total supply time of the repair signal SVR when a fault is detected each time step S12 is executed. The processor of the power supply circuit 10 may determine that repair by supplying the repair signal SVR is possible until the total supply time of the repair signal SVR reaches a predetermined time. On the other hand, when the total supply time of the repair signal SVR reaches the predetermined time, the processor of the power supply circuit 10 may determine that repair by supplying the repair signal SVR is impossible and stop supplying the repair signal SVR and the drive signal SVD.

[0184] This also stops the application of voltage between the transparent electrode layers 22, 23 when the micro-short circuit cannot be repaired by applying the repair voltage VLR, thereby preventing voltage from being continuously applied between the transparent electrode layers 22, 23 when a micro-short circuit exists.

[0185] When the supply time Ta of the repair signal SVR reaches the set time Tp, the processor of the power supply circuit 10 causes the fault determination circuit 32 to stop outputting the repair request signal SIGS. Then, the processor of the power supply circuit 10 switches the signal supplied to the light controlling sheet 20 from the repair signal SVR to the drive signal SVD. At this time, if the fault determination circuit 32 does not detect a fault after the supply of the drive signal SVD, the processor of the power supply circuit 10 may cause the fault state display circuit 33 to display to the outside that the [C] convergence abnormality has been repaired, that is, that the repair of the micro short circuit has been completed.

[0186] This allows the user of the light-adjusting sheet 20 to know that the micro-short circuit has been repaired. The light-adjusting sheet fault detection device can also prompt the user to take action after the micro-short circuit has been repaired. As a result, the period during which the high-voltage repair voltage is applied can be made more appropriate, and the period during which the operation of the light-adjusting sheet is stopped for repairs can be made more appropriate.

[0187] [Failure judgment] The power supply circuit 10 may be configured to include a configuration for detecting [A] a system leakage current and a configuration for detecting [C] a convergence abnormality, and omit the configuration for detecting [B] a reversal abnormality. The power supply circuit 10 may be configured to include a configuration for detecting [B] a reversal abnormality and a configuration for detecting [C] a convergence abnormality, and omit the configuration for detecting [A] a system leakage current. The power supply circuit 10 may be configured to include a configuration for detecting [C] a convergence abnormality, and omit the configuration for detecting [A] a system leakage current and the configuration for detecting [B] a reversal abnormality.

[0188] The power supply circuit 10 may detect a micro-short circuit based on an electrical characteristic value other than the convergence value of the sensed current. For example, the power supply circuit 10 may use a change in the sensed current over time as the second characteristic value.

[0189] As shown in Fig. 11, the lower the resistance value of the edge liquid crystal resistor R11S, the shorter the period during which the detected current drops. Therefore, the power supply circuit 10 may set a threshold value to the length of the period during which the drop in the detected current per unit time is equal to or greater than a predetermined value, and may determine that no micro-short circuit exists when a current drop of equal to or greater than the predetermined value is detected for a period longer than the threshold value. The power supply circuit 10 may also determine that a micro-short circuit exists when the current drop of equal to or greater than the predetermined value is limited to a period equal to or less than the threshold value.

[0190] 11, the period during which a difference is observed in the convergence value of the detection current is longer than the period during which a difference is observed in the decrease per unit time of the detection current. Therefore, if the above-mentioned configuration detects a micro short circuit based on the convergence value of the detection current being greater than a threshold value, the presence of a micro short circuit can be detected with high accuracy.

[0191] The power supply circuit 10 may detect the high resistance of the transmission line based on an electrical characteristic value other than the peak value of the detected current. For example, the power supply circuit 10 may use a change in the detected current over time as the first characteristic value.

[0192] As shown in Fig. 9, the lower the resistance value of the first contact resistor R2S, the greater the drop in the detected current from the peak. Therefore, the power supply circuit 10 may set a threshold value for the drop in the detected current per unit time, and determine that no micro-short circuit exists when the drop per unit time is greater than the threshold value. The power supply circuit 10 may also determine that a micro-short circuit exists when the drop per unit time is equal to or less than the threshold value.

[0193] The fault condition display circuit 33 is an example of a notification section, and may notify the user of the occurrence of a fault by display and sound, or by sound only. [Fault detection device] The light adjusting sheet 20 may be attached to a transparent body, may be in a state before being attached to a transparent body, or may be in a state where it is inspected during the manufacturing process of the light adjusting sheet 20. The transparent body is, for example, a glass plate or a resin plate. The light adjusting sheet fault detection device may be applied to a light adjusting sheet drive device or may be applied to a light adjusting sheet inspection device. The light adjusting sheet fault detection method may be applied to a light adjusting sheet drive method or may be applied to a light adjusting sheet inspection method.

[0194] In addition, when the planar light-adjusting sheet 20 is attached to a curved transparent body, tension acts on the light-adjusting sheet 20 to narrow the gap between the transparent electrode layers 22, 23. Such tension is likely to cause micro-short circuits due to conductive foreign matter present in the gap between the transparent electrode layers 22, 23. For this reason, the light-adjusting sheet fault detection device and the light-adjusting sheet fault detection method target the light-adjusting sheet 20 attached to a curved transparent body, making the effect of breaking the micro-short circuit more pronounced. [Explanation of symbols]

[0195] SVD…Drive signal TSM1: First sampling period TSM2…Second sampling period VLD…Drive voltage VLR: Repair voltage 10…Power circuit 11...Transformer circuit 12...First boost circuit 13...Second boost circuit 14...Control power supply circuit 15...Timing control circuit 16...Drive voltage generation circuit 17...Switching circuit 18...Clock generation circuit 20...Light control sheet 21...Photochromic layer 22...First transparent electrode layer 23...Second transparent electrode layer 31...Drive circuit 32…Failure judgment circuit 33...Fault status indication circuit 35...Current detection circuit

Claims

1. A voltage application unit that applies a driving voltage between transparent electrode layers of a light control sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound; a detection unit that detects a current flowing between the transparent electrode layers due to application of the driving voltage and detects a failure of the light controlling sheet based on the detected current; The detection unit is Detecting, as a first fault, that the peak value of the current is equal to or less than a predetermined first threshold; and A second fault is detected when the convergence value of the current is greater than a second predetermined threshold value. Fault detection device for light control sheets.

2. The voltage application unit supplies a drive signal between the transparent electrode layers, the drive signal is an AC voltage with the drive voltage set to a peak-to-peak value; a predetermined period shorter than a half period of the drive signal is a first sampling period, a second sampling period, the second sampling period being shorter than a half period of the drive signal; the first sampling period starts and the second sampling period ends when the voltage application unit inverts the polarity of the driving voltage; The detection unit is detecting the peak value from a sample of the current sensed during the first sampling period; The current sensed during the second sampling period is sampled to detect the convergence value from among the samples. A fault detection device for a light controlling sheet according to claim 1.

3. A current flowing into one of the transparent electrode layers is a source current, The current drawn from the other transparent electrode layer is a sink current; The detection unit is A third fault is detected when the difference between the source current and the sink current is equal to or greater than a third threshold value. A fault detection device for the light controlling sheet according to claim 1 or 2.

4. The voltage application unit is When the detection unit detects the first fault, the application of a voltage between the transparent electrode layers is stopped; When the detection unit detects the second fault, a repair voltage higher than the driving voltage is applied between the transparent electrode layers. A fault detection device for a light controlling sheet according to any one of claims 1 to 3.

5. A voltage application unit that applies a driving voltage between transparent electrode layers of a light control sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound; a detection unit that samples a current flowing between the transparent electrode layers due to application of the driving voltage during a predetermined sampling period, and detects a fault in the light controlling sheet based on a current waveform that is the sample that is extracted; The detection unit is identifying a first characteristic value derived from a contact resistance value between the transparent electrode layer and a wiring from the current waveform, and detecting that the identified first characteristic value is outside a predetermined normal range as a first fault which is an increase in the contact resistance value; A second characteristic value derived from a resistance value between the transparent electrode layers is identified from the current waveform, and the identified second characteristic value being outside a predetermined normal range is detected as a second fault, which is the presence of a micro-short circuit between the transparent electrode layers. Fault detection device for light control sheets.

6. Applying a driving voltage between transparent electrode layers of a light control sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound; Detecting a current flowing between the transparent electrode layers due to application of the driving voltage, and detecting a failure of the light controlling sheet based on the detected current; Detecting a failure of the light adjusting sheet Detecting, as a first fault, that the peak value of the current is equal to or less than a predetermined first threshold; and A second fault is detected when the convergence value of the current is greater than a second predetermined threshold value. A method for detecting faults in light control sheets.

7. Applying a driving voltage between transparent electrode layers of a light control sheet having a liquid crystal compound between the transparent electrode layers to drive the liquid crystal compound; extracting a current flowing between the transparent electrode layers due to application of the driving voltage during a predetermined sampling period, and detecting a fault in the light-adjusting sheet based on a current waveform that is the extracted sample; Detecting a failure of the light adjusting sheet identifying a first characteristic value derived from a contact resistance value between the transparent electrode layer and a wiring from the current waveform, and detecting that the identified first characteristic value is outside a predetermined normal range as a first fault which is an increase in the contact resistance value; A second characteristic value derived from a resistance value between the transparent electrode layers is identified from the current waveform, and the identified second characteristic value being outside a predetermined normal range is detected as a second fault, which is the presence of a micro-short circuit between the transparent electrode layers. A method for detecting faults in light control sheets.

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