Driving circuit for driving electro-optical device

Abstract

A drive circuit for driving an electro-optical device, such as an optically switchable glazing (e.g. a glass panel provided with a PDLC or SPD layer), comprises a set of input terminals for receiving an alternating input voltage of a first frequency; a set of output terminals for supplying an alternating output voltage of a second frequency; a control circuit for generating a control signal in dependence on an input signal representative of a charging state of the electro-optical device; and a current direction circuit for controlling a current flow direction of a current in response to the control signal. The control circuit and the current direction circuit are thereby configured to control the second frequency such that deterioration of the electro-optical device is prevented while maintaining a low energy consumption.

Description

Technical Field

[0001] The present invention relates to a driving circuit for driving an electro-optic device, such as a switchable window glass comprising a polymer dispersed liquid crystal (PDLC) layer or a suspended particle device (SPD) layer. Background Technology

[0002] Open roof assemblies are well known in the art. Known open roof assemblies are arranged on the roof of a vehicle, with an opening provided within the roof. A movable closure member is selectively positioned in an open or closed position. In the open position, the interior of the vehicle is in open contact with the exterior, for example, to provide fresh air to the interior. In the closed position, the interior of the vehicle is enclosed and protected from, for example, rain and other external influences. In known open roof assemblies, the closure member may be (semi-)transparent to allow sunlight to enter the interior when the closure member is in the closed position.

[0003] In existing technologies, roof windows typically incorporate roll-up or movable light-blocking components to reduce the amount of light entering the passenger compartment. In recent years, the use of switchable glass (also known as, for example, smart glass) for light control has been considered. Switchable glass can be an electro-optical device, in which case the optical transparency of the glass can be altered by applying voltage or current.

[0004] Known electro-optic switchable glass technologies include polymer-dispersed liquid crystal (PDLC) technology and suspended particle device (SPD) technology. Both types of electro-optic window glass are preferably operated by applying an alternating current (AC) voltage, preferably an AC voltage without direct current, to prevent electrochemical decomposition.

[0005] Without applied voltage, the aforementioned electroluminescent window glass type remains blurred or darkened. Applying voltage increases transparency. Typically, 60V or higher AC voltage is applied to achieve maximum transparency. On the other hand, in vehicles, only a usable DC voltage of 12V from the battery is available. Therefore, it is necessary to convert the available DC voltage to AC voltage and to increase the voltage level. However, for safety reasons, it is preferable to use the lowest possible voltage in vehicles.

[0006] Furthermore, any electronic components used to generate and supply the driving voltage to the switchable glass should be securely arranged and should not occupy more space than strictly required, especially when the switchable glass is mounted on a moving closure in the vehicle's roof. Additionally, electromagnetic interference should be kept to a minimum.

[0007] US2019 / 0041668 discloses a switchable glass driving circuit in which a high-frequency AC input voltage is supplied to the driving circuit and generates a predetermined lower-frequency AC output voltage, which is supplied to the switchable glass. A drawback of the disclosed driving circuit is its limited ability to adapt to changing conditions (e.g., power supply voltage levels). Summary of the Invention

[0008] Therefore, the object of the present invention is to provide a simple and cost-effective drive circuit for electro-optic devices, which can be adapted to various situations.

[0009] In a first aspect, the objective is achieved in the drive circuit according to claim 1. The drive circuit for driving the electro-optical device includes: a set of input terminals for receiving an AC input voltage of a first frequency; a set of output terminals for supplying an AC output voltage of a second frequency; a control circuit that generates a control signal based on an input signal representing the charging state of the electro-optical device; and a current direction circuit for controlling the direction of current flow in response to the control signal. The control circuit and the current direction circuit of the drive circuit are thus configured to control the second frequency. This allows the drive circuit to change the second frequency to adapt to changing conditions while maintaining low power consumption by keeping the second frequency as low as possible.

[0010] According to the present invention, the charging state of the electro-optical device is monitored to switch the current direction. When the electro-optical device is charged to a certain level, the current direction is reversed. Reaching this charging level takes longer when the input voltage is low, and shorter when the input voltage level increases. To prevent degradation of the electro-optical device, the output voltage needs to periodically switch the current direction; however, power consumption increases with frequency. Therefore, the present invention provides a drive circuit to prevent degradation of the electro-optical device while reducing power consumption regardless of, for example, the actual input voltage level.

[0011] Furthermore, compared to the driving circuits of the prior art described above, the driving circuit according to the present invention does not require any clock signal, frequency signal, or any other type of timing signal to control the second frequency. This provides the advantage of a simpler and more cost-effective driving circuit.

[0012] In one embodiment, the first frequency is higher than the second frequency.

[0013] In one embodiment of the drive circuit, the control signal has two possible states and the current direction circuit is configured to allow current to flow in only one of the two possible directions depending on the actual state of the control signal. In such an embodiment, the level of the input circuit can have any value, while the control signal has a predetermined level. For example, the control signal can have one of the two possible states, but it is contemplated that more than two states can be used.

[0014] In a particular embodiment, the control circuit includes a bistable multivibrator circuit. For example, the bistable multivibrator circuit can be a trigger device. The bistable multivibrator circuit itself is known and changes its output signal when the input signal exceeds a predetermined level. In the drive circuit according to the invention, when charging the electro-optical device, the input signal can gradually change over time. Once the charging exceeds a predetermined level, the input signal exceeds the corresponding level, and the bistable multivibrator circuit changes the output signal, thereby causing a change in the current direction. After switching the current direction, the input signal begins to change again until the electro-optical device is charged to the predetermined level again, and so on.

[0015] As described herein, the control signal has at least two possible states. It should be noted that the control signal may include multiple output signals on a corresponding number of output terminals. Specifically, in one embodiment, the control signal includes two output signals, wherein in a first state, the first signal may be high and the second signal may be low, and in a second state, the first signal may be low and the second signal may be high.

[0016] In one embodiment, the control circuitry includes an integrator circuit, wherein the integrator circuitry is configured such that the voltage at one of the set of output terminals determines the charging of the integrator circuitry. Charging of the electro-optical device can be simulated by a representative integrator circuitry connected to the same output terminal. Therefore, the charging state of the integrator circuitry represents the charging state of the electro-optical device.

[0017] In another embodiment, the integrator circuit includes an RC integrator circuit, wherein a resistor and a capacitor are connected in series between two output terminals of the set of output terminals. The control circuit is configured to use the node voltage at the node between the resistor and the capacitor as the input voltage. As the capacitor is charged, the node voltage at the node between the capacitor and the resistor gradually changes, thereby representing the charging state of the capacitor, which in turn represents the charging state of the electro-optical device, as described above.

[0018] In a particular embodiment, the resistance of the resistor in the integrator circuit is selectable for controlling the second frequency. For example, the integrator circuit can be matched to a specific input voltage, a specific electro-optical device, or any other component through a calibration procedure. In a particular embodiment, the variable resistor can be controlled in response to certain characteristics or conditions. For example, if the electro-optical device exhibits temperature-dependent charging behavior, a temperature-dependent resistor can be used, or the control unit can control the variable resistor in response to a sensed temperature. Other characteristics affecting charging behavior can be used, and are obvious to those skilled in the art. In another approach, the second frequency can be monitored, and when the second frequency exceeds a predetermined range, the variable resistor can be controlled to bring the second frequency back into the predetermined range.

[0019] In one embodiment, the current direction circuit includes a first direction control element and a second direction control element, wherein the control signal determines which of the first and second direction control elements is capable of conducting current. For example, the direction control element may be a thyristor as a controllable diode, or a diode combined with a switch such as a MOSFET. Of course, any other circuit arrangement or electronic component for controlling the current direction may also be used.

[0020] In one embodiment, the control circuitry includes a microcontroller device configured to control the control signal based on the input signal. Using a microcontroller, any type of control method can be implemented. For example, using a current probe on one of the output terminals, the charging in the electro-optical device and the evolution of current over time during charging can be precisely monitored. Based on any predetermined desired considerations and assumptions, the control signal can be controlled and supplied to the current direction circuit.

[0021] In one embodiment, a voltage control circuit can be provided to control the output voltage level. The voltage control circuit can be arranged in any part of the drive circuit, or even as a separate circuit section. For example, the voltage control circuit can be configured and arranged to control the power supply voltage provided to the primary winding of a transformer, while the secondary winding of the transformer outputs the input voltage of the drive circuit. The voltage control circuit can even provide further control for managing and controlling the electro-optical device. In particular, by using a properly programmed microcontroller, complex schemes and procedures can be employed to balance charging with other requirements and characteristics. For example, electro-optical devices with different charging behaviors can be combined and controlled through a single drive circuit, or intermediate optical states, such as intermediate dimming states, can be provided and controlled.

[0022] In one embodiment, the drive circuit is coupled to at least one optically switchable film. In a particular embodiment, the drive circuit is coupled to multiple segments of one or more optically switchable films.

[0023] In one aspect, the invention provides an open roof assembly including a movable closure member, wherein the movable closure member includes an electro-optical device and wherein a transformer and a drive circuit for driving the electro-optical device according to claim 1 are mounted on the closure member. Selecting a suitable high-frequency input voltage allows the use of a small transformer. Such a small transformer can be mounted on the movable closure member. As a result, the power wiring to the closure member only needs to provide a low voltage to the closure member and generate and supply a high voltage only close to the electro-optical device. This arrangement of the circuit is particularly advantageous for safety reasons, because the electrical wiring between the vehicle body and the movable closure member only carries a safe voltage.

[0024] It should be noted that the aforementioned open roof assembly includes the drive circuit according to the invention. It is contemplated that the drive circuit could be any other drive circuit, provided it is configured to receive a relatively high frequency power supply voltage, allowing a small transformer to be used to increase the voltage from low to high. Furthermore, in addition to electro-optical devices, suitable high power supply voltages can be supplied to any other circuits or devices arranged on the movable enclosed member that require high voltages, by using a small transformer mounted on the enclosed member and, if necessary, providing a suitable drive circuit for adapting high frequency, high voltages to power supply voltages appropriate for specific circuits or devices.

[0025] In another aspect, the present invention provides a method according to claim 12. The method of driving an electro-optical device includes the steps of: receiving an AC input voltage of a first frequency at a set of input terminals; and generating an AC output voltage of a second frequency at a set of output terminals. The second frequency is controlled by the following steps: generating a control signal based on an input signal representing a charging state of the electro-optical device; and controlling the direction of current flow in response to the control signal.

[0026] In one embodiment, the method further includes the step of determining the actual conditions of the electro-optical device, wherein the step of generating an AC output voltage of a second frequency at the set of output terminals includes taking into account the actual conditions. For example, such actual conditions could be temperature. For instance, the switchable optical layer of a PDLC or SPD may exhibit electrical properties that depend on conditions such as temperature. When such condition dependence is taken into account, an optimal drive voltage or drive current can be obtained. Attached Figure Description

[0027] The further applicability of the invention will become apparent from the detailed description given below. However, it should be understood that while embodiments of the invention are shown, the detailed description and specific examples are given by way of illustration only, as various changes and modifications within the scope of the invention will become apparent to those skilled in the art upon reference to the accompanying drawings and this detailed description, wherein:

[0028] Figure 1A A perspective view of the roof with an open roof assembly is shown;

[0029] Figure 1B Show Figure 1A Exploded view of the open roof assembly;

[0030] Figure 2A A diagram showing a first embodiment of the drive circuit according to the present invention;

[0031] Figure 2B A diagram showing a second embodiment of the drive circuit according to the present invention is shown;

[0032] Figure 2C A diagram showing a third embodiment of the drive circuit according to the present invention;

[0033] Figures 3A-3C Show respectively according to Figure 2A A graph showing the input voltage and output voltage of either the first or second embodiment of 2B;

[0034] Figure 4A Showing according to Figure 2C The input voltage and output voltage curves of the third embodiment;

[0035] Figure 4B Showing according to Figure 2C The output current curve of the third embodiment;

[0036] Figure 4C Showing according to Figure 2C A charging curve of the third embodiment;

[0037] Figure 5A A diagram showing a fourth embodiment of the driving circuit according to the present invention;

[0038] Figure 5B A diagram showing a fifth embodiment of the drive circuit according to the present invention;

[0039] Figure 6 A diagram showing a sixth embodiment of the drive circuit according to the present invention;

[0040] Figure 7A diagram showing a seventh embodiment of the driving circuit according to the present invention;

[0041] Figure 8A A diagram showing an eighth embodiment of the drive circuit according to the present invention;

[0042] Figure 8B A diagram showing a ninth embodiment of the drive circuit according to the present invention; and

[0043] Figure 9 An exploded schematic diagram of an open roof assembly including a drive circuit according to the present invention is shown. Detailed Implementation

[0044] The invention will now be described with reference to the accompanying drawings, in which the same reference numerals are used to identify the same or similar elements in these views.

[0045] Figure 1A The diagram shows a roof 1 having an open roof assembly disposed therein. The open roof assembly includes a movable panel 2a and a fixed panel 2b. The movable panel 2a is also referred to as a closing member because it can move over a first roof opening 3a to open and close the first roof opening 3a. A wind deflector 4 is disposed at the front of the first roof opening 3a.

[0046] In the illustrated embodiment, the movable panel 2a can be in a closed position, whereby the movable panel 2a is positioned above and closes the first roof opening 3a and is therefore typically positioned within the plane of the roof 1. Further, the movable panel 2a can be in an inclined position, whereby the rear end RE of the movable panel 2a is raised compared to the closed position, while the front end FE of the movable panel 2a remains in the closed position. Further, the movable panel 2a can be in an open position, whereby the movable panel 2a slides open and the first roof opening 3a is partially or completely exposed.

[0047] It should be noted that the roof 1 shown corresponds to a passenger vehicle. However, the invention is not limited to passenger vehicles. It is also contemplated that any other type of vehicle may be equipped with a movable panel.

[0048] Figure 1B As shown Figure 1A The same roof shown has panels 2a and 2b. Specifically, although... Figure 1A The open roof assembly is shown in the open position, but Figure 1B This is an exploded view of the open roof assembly in its closed position. Further, in... Figure 1BThe exploded view shows the presence of a second roof opening 3b. The first and second roof openings 3a and 3b are disposed within the frame 5 of the open roof assembly. The edge 5a of the frame 5 defines the first roof opening 3a.

[0049] The second roof opening 3b is arranged below the fixed panel 2b to allow light to enter the vehicle's interior passenger compartment through the fixed panel 2b, assuming the fixed panel 2b is a glass panel or a similar transparent panel, for example, made of plastic or any other suitable material. The second roof opening 3b is optional with the transparent or translucent fixed panel 2b, and may be omitted in another embodiment of the open roof assembly.

[0050] The wind deflector 4 is typically made of a flexible material, such as a woven or nonwoven fabric with through-holes arranged therein, or a mesh or net. The flexible material is supported by a support structure 4a (e.g., a rod-like or tubular structure), which is hinged directly or indirectly to the frame 5 at a hinge 4b.

[0051] The wind deflector 4 is positioned in front of the first roof opening 3a and adapts to airflow when the movable panel 2a is in the open position. In its raised position, the wind deflector 4 reduces inconvenient noise caused by airflow during driving. When the movable panel 2a is in the closed or tilted position, the wind deflector 4 is held downward below the front end FE of the movable panel 2a.

[0052] Normally, when the movable panel 2a slides to the open position, the wind deflector 4 rises due to spring force, and when the movable panel 2a slides back to its closed position, the wind deflector 4 is pushed downward by the movable panel 2a. Figure 1A In the image, the movable panel 2a is shown in the open position, and the wind deflector 4 is shown in the raised position. Figure 1B In the image, the movable panel 2a is shown in a closed position, and the wind deflector 4 is correspondingly shown in a position in which it is held downward.

[0053] Figure 1B A drive assembly with a first guide assembly 6a, a second guide assembly 6b, a first drive cable 7, and a second drive cable 8 is further shown. The first and second guide assemblies 6a and 6b are arranged on corresponding side ends SE of the movable panel 2a and each may include a guide and a mechanism. The guide is coupled to the frame 5, and the mechanism includes movable parts and can slide within the guide. The first and second drive cables 7 and 8 are disposed between the mechanism of the corresponding guide assembly 6a and 6b and the electric motor 9.

[0054] Drive cables 7 and 8 connect electric motor 9 to the mechanisms of the corresponding guide components 6a and 6b, so that the mechanisms begin to move when the electric motor 9 is operated. Specifically, the electric motor 9 moves the core of the drive cables 7 and 8 to push or pull the mechanisms of the corresponding guides 6a and 6b. Such drive components are well known in the art and therefore will not be further described herein. However, any other suitable drive components may be used without departing from the scope of the invention. Moreover, in certain embodiments, the electric motor may be operatively arranged between the corresponding guides and the corresponding mechanisms of the guide components 6a and 6b, and in such embodiments, the drive components may be completely omitted.

[0055] In the illustrated embodiment, the guide components 6a, 6b can be initiated by raising the rear end RE of the movable panel 2a, thereby placing the movable panel 2a in an inclined position. Then, from the inclined position, the guide components 6a, 6b can begin to slide to place the movable panel 2a in an open position. However, the invention is not limited to such embodiments. For example, in another embodiment, the movable panel 2a can be moved to the inclined position by raising the rear end RE, and the open position can be achieved by first lowering the rear end RE and then sliding the movable panel 2a under the fixed panel 2b or under any other structure or element disposed behind the rear end RE of the movable panel 2a. In another exemplary embodiment, the movable panel 2a may only be movable between a closed position and an inclined position, or between a closed position and an open position.

[0056] In the illustrated embodiment, the electric motor 9 is mounted at the recess 10 near or below the front end FE of the movable panel 2a. In another embodiment, the electric motor 9 can be positioned at any other suitable location or orientation. For example, the electric motor 9 can be arranged near or below the rear end RE of the movable panel 2a or below the fixed panel 2b.

[0057] Control unit 11 is schematically shown and operatively coupled to electric motor 9. Control unit 11 can be any type of processing unit well known to those skilled in the art: a software-controlled processing unit or a dedicated processing unit, such as an ASIC. Control unit 11 can be a standalone control unit, or it can be operatively connected to another control unit, such as a multi-purpose vehicle control unit. In yet another embodiment, control unit 11 can be embedded in or be part of such a multi-purpose vehicle control unit. In essence, control unit 11 can be implemented by any control unit suitable for, capable of, and configured to perform operation of electric motor 9 and thus movable roof assembly.

[0058] According to Figure 1A and 1B An electro-optical device can be installed in the open roof assembly. For example, a PDLC or SPD transparency control layer can be embedded in the glass panel of the closed member 2a or the fixed panel 2b. Figure 2A A drive circuit 20 is shown for providing a suitable power supply voltage for such an electro-optical device 40.

[0059] like Figure 2A As shown, AC voltage source 16 provides AC voltage to the primary winding of transformer 18. AC voltage source 16 can be located in a vehicle and can be configured to provide a suitable AC voltage from, for example, a DC voltage from a vehicle battery. Any other AC voltage source 16 can also be used. The invention is not limited to AC voltage source 16. In a preferred embodiment, the AC voltage from AC voltage source 16 is a low voltage, but this is not necessary. Further, in a preferred embodiment, the frequency of the AC voltage is a relatively high frequency, preferably 500 Hz or higher, more preferably exceeding 1 kHz and possibly even exceeding 2 kHz, because the increase in frequency allows for a reduction in the size of transformer 18. If the size of transformer 18 is irrelevant in a particular application, the frequency of the AC voltage supplied by the AC voltage source can be irrelevant. Moreover, when using the drive circuit according to the invention, the specific frequency and frequency accuracy are generally less important because the drive circuit of the invention will automatically adapt to the frequency and amplitude of the supplied AC voltage, as explained below.

[0060] The secondary winding of transformer 18 is connected between the first input terminal 201 and the second input terminal 202 of drive circuit 20. The amplitude of the AC voltage supplied to the first input terminal 201 and the second input terminal 202 is determined by the winding ratio of the primary winding and the secondary winding of transformer 18 and the amplitude of the AC voltage supplied by AC voltage source 16, as is well known to those skilled in the art.

[0061] An electro-optic device 40 is connected between the first output terminal 206 and the second output terminal 207 of the driving circuit 20. The driving circuit 20 supplies an output voltage at these output terminals 206 and 207 to control the optical characteristics of the electro-optic device 40. If the electro-optic device 40 is a switchable PDLC or SPD layer, the output voltage is preferably a relatively low-frequency, high-voltage AC output voltage to prevent degradation of the switchable layer while maintaining low energy consumption.

[0062] The drive circuit 20 includes a current direction circuit 24 configured to allow current to flow only in a predetermined direction. Specifically, the current direction circuit 24 can be controlled by one or more signals that define which direction current flow is permitted. In the illustrated embodiment, the current direction circuit 24 includes a first thyristor 241 and a second thyristor 242, wherein the thyristors 241 and 242 are connected in anti-parallel. A high voltage is provided at the gate of the first thyristor 241 to switch one of the thyristors 241 and 242 to conduct, allowing the permitted current to flow in a first direction. Switching the high voltage to the gate of the second thyristor 242 allows the current to flow in the opposite second direction. It will be apparent to those skilled in the art that providing a high voltage to the gate of each thyristor 241 and 242 allows current in both directions, and switching the two gates to a sufficiently low voltage switches both thyristors 241 and 242 to non-conduct. Other embodiments of the current direction circuit 24 are also contemplated. For example, each thyristor 241, 242 can be replaced by a switch, and the diode or thyristor 241, 242 can be replaced by two MOSFETs connected in series, wherein the body diodes of the two MOSFETs are connected in anti-series configuration. This invention is not limited to a specific embodiment of the current direction circuit 24.

[0063] For example, it is further anticipated that the current direction circuit 24 is implemented such that a low control signal controls the current direction circuit 24 to allow current along a first direction, while a high control signal controls the current direction circuit 24 to allow current along the opposite second direction.

[0064] Control circuit 22 supplies control signals to current direction circuit 24, wherein the control signals may be implemented as a single voltage signal, multiple parallel voltage signals, or even multiplexed signals, depending on a specific embodiment of current direction circuit 24.

[0065] Control circuit 22 controls current direction circuit 24 in response to input signal 28. Input signal 28 represents the charging state of electro-optic device 40. Once electro-optic device 40 is (almost) fully charged, control circuit 22 switches the current direction.

[0066] The control circuit 22 can be implemented, for example, as a bistable multivibrator like a trigger. Essentially, the control circuit 22 has a predetermined number of output signals as control signals. For example, the control signals can have one of two voltage output levels: low voltage or high voltage. Once the input voltage exceeds a first threshold, the control signal becomes high voltage. Then, the current direction is switched and the input voltage decreases and its polarity is switched. Then, when the input voltage exceeds a second threshold, the control signal is switched to low voltage. Thus, the process repeats itself. The frequency of repetition is determined by the charging speed of the electro-optical device 40. Moreover, the frequency of repetition determines the AC frequency of the AC output voltage, which corresponds to the second frequency of the present invention.

[0067] As described above, the control signal output by control circuit 22 depends on the hysteresis loop. Other circuits besides a bistable multivibrator can be used, and this will be apparent to those skilled in the art. For example, a microprocessor may be suitable. Considering cost-effectiveness, a microprocessor may be preferred if further functions can be controlled by such a microprocessor.

[0068] Input signal 28 represents the charging state of electro-optical device 40. While deriving such a charging state directly from electro-optical device 40 may prove challenging within the scope of this invention, therefore, in the illustrated embodiment, an integrator circuit, such as RC circuit 26, is connected between the two output terminals 206, 207. RC circuit 26 includes resistor 262 and capacitor 261. Resistor 262 and capacitor 261 are connected in series via a node 263 between them. The node voltage at node 263 is used as input signal 28.

[0069] Similar to electro-optical device 40, capacitor 261 is charged by the output voltage at output terminals 206, 207. Choosing a suitable resistor for resistor 262 and a suitable capacitor for capacitor 261 provides a charging behavior that mimics the charging behavior of electro-optical device 40. The node voltage at node 263 then represents the charging state of electro-optical device 40. Based on this charging state, control circuitry 22 is configured to switch the current direction at an optimal time, maintaining low energy consumption under low-frequency AC output voltage conditions while preventing degradation of electro-optical device 40.

[0070] It should be noted that additional components or circuits can be added. For example, additional diodes or thyristors can be provided. Based on the operation of the current direction circuit 24 and the AC input voltage at input terminals 201, 202, no input voltage is applied for approximately 50% of the time. During the periods without input voltage, current flow may be generated in the circuit portion formed by the electro-optical device 40 and the RC circuit 26, thereby affecting the charging state of the electro-optical device 40 and the charging state of the RC circuit 26. Depending on the design and the selected characteristics of resistors and capacitors, adding an additional current direction circuit, such as the current direction circuit 24, to the aforementioned circuit portion may be preferable.

[0071] It should be further noted that in some embodiments, and in one or more of the embodiments described below, such additional current direction circuitry may be preferred or even necessary for proper operation. For example, in Figure 2C In the embodiments described below, multiple electro-optical devices 40a-40c are connected in parallel. The generated current may be large, making an additional current direction circuit 26 likely. In embodiments where multiple integrator circuits (e.g., RC circuits 26) are provided, the additional current direction circuit may be highly preferred.

[0072] like Figure 2B As shown, the RC circuit 26—or any other circuit providing the input signal 28—is not necessarily part of the drive circuit 20. For example, the drive circuit 20 may be provided with a third input terminal 203 for receiving the input signal 28. Such a design allows the drive circuit 20 to be manufactured independently of the characteristics of the electro-optical device 40 to be driven, since the RC circuit 26 can then be selected and connected.

[0073] For clarity, dashed boxes representing the drive circuit 20 and the corresponding terminals 201, 202, 203, 206, and 207 are omitted in the other figures, because the definitions and limitations of the drive circuit 20 and the corresponding terminals 201, 202, 203, 206, and 207 are obvious to those skilled in the art based on figures 2A and 2B. For example, it will be apparent to those skilled in the art that, in one embodiment, the transformer 18 may also be considered to form part of the drive circuit 20.

[0074] exist Figure 2C In the third embodiment shown, the drive circuit is connected to three electro-optical devices 40a, 40b, and 40c. These three electro-optical devices 40a, 40b, and 40c can be three physically separate devices, such as those embedded in three separate windows (e.g., side windows of a vehicle) or separate glass panels of an open roof assembly (see [link to relevant documentation]). Figure 1A and 1BIn the movable panel 2a and fixed panel 2b shown. In another or further embodiment, the three electro-optic devices 40a, 40b and 40c form segments of a physically single device, wherein the segments can be formed by applying segmented electrodes, thereby functionally dividing the single device into three individually controllable segments.

[0075] If the three electro-optical devices 40a, 40b, and 40c have similar charging behaviors, then a single RC circuit 26 will represent the charging state of each of the three electro-optical devices 40a, 40b, and 40c. Therefore, a single RC circuit 26 is sufficient.

[0076] Figures 3A-3C This illustrates the operation of the drive circuit. The input and output voltages generated in the simulation are plotted over time. The input voltage is plotted using dashed lines. For example, from... Figures 3A-3C As can be clearly seen from the curve, the input voltage has an AC frequency of 500Hz.

[0077] Draw the output voltage using a solid line. It should be noted that the output voltage shown is the voltage at the node of the RC circuit, representing the actual output voltage.

[0078] In this simulation, since the ratio of the number of primary windings to the number of secondary windings of the transformer is chosen to be 1, the maximum amplitude of the output signal is similar to the maximum amplitude of the input voltage. In a practical embodiment, these maximum amplitudes can be appropriately selected based on the available input voltage and the desired output voltage. For illustrative purposes only, the ratio is chosen to be 1 in this simulation.

[0079] exist Figure 3A In this circuit, the maximum amplitude of both the input and output signals is 38V. For example, at time 0.35s, the output voltage is approximately -38V, indicating that the electro-optical device 40 is almost fully charged, so it is recommended to switch the polarity to prevent degradation. Therefore, the current direction circuit is switched and the output voltage increases to approximately 28V in the first cycle of the AC input voltage. In the next cycle, the output voltage further increases to approximately 38V at time 0.375s. Then, the current direction is switched again and the output voltage drops to approximately -28V in the first cycle after the switch. This process repeats itself, thus generating an AC output voltage with an almost square wave shape at an AC frequency of approximately 20Hz.

[0080] When the AC input voltage amplitude is approximately 40V, the following is obtained: Figure 3B The curve. The shape of the output voltage remains the same as... Figure 3AThe output voltage has the same shape, but because the electro-optical device and RC circuit are charged more quickly to the level recommended for switching to prevent degradation, the AC frequency of the output voltage is significantly changed to approximately 29.4 Hz. Figure 3C As shown, with an AC input voltage amplitude of 42V or even higher, the AC frequency of the output voltage increases to approximately 38.5Hz.

[0081] exist Figure 4A In, it is shown Figure 2C The embodiments are defined as representative node voltages of the AC input and AC output voltages, where the dashed lines represent the AC input voltage at 500Hz and the amplitude at 40V over time. Solid lines represent the AC output voltage connected to an electro-optical device 40. Dashed lines correspond to embodiments with four parallel connections, and dotted dashed lines correspond to embodiments with eight parallel connections. (From...) Figure 4A It is clear that the number of connected electro-optical devices does not affect the AC frequency of the output voltage.

[0082] Figure 4B The output current depends on the number of electro-optical devices connected, where different lines correspond to... Figure 4A The lines shown. (As from...) Figure 4B It is evident that the increase in output current is proportional to the number of connected electro-optical devices, as can be expected.

[0083] Figure 4C This illustrates the charge applied according to the number of connected electro-optical devices, where different lines correspond to... Figure 4A and 4B The lines shown. (As from...) Figure 4C It is clearly visible and, as can be expected, that the amount of charge is proportional to the number of electro-optical devices or segments connected.

[0084] Figure 5A A fourth embodiment is shown, wherein the first switch 30a and the second switch 30b are respectively connected to the first electro-optical device 40a and the second electro-optical device 40b. Further, a first RC circuit 26a and a second RC circuit 26b are provided. It should be noted that, as described above, one or more additional current direction circuits may be required to prevent crosstalk and unwanted current generation.

[0085] The first and second switches 30a and 30b can be manually or electronically operated, and in the latter case, they can be operated by the control circuit 22, as shown by the continuous dashed lines. Although more control is possible in this embodiment, the switching of current direction is still performed simultaneously on the two electro-optical devices 40a and 40b.

[0086] exist Figure 5B In the fifth embodiment, the first and second electro-optical devices 40a and 40b can be switched individually using first and second current direction circuits 24a and 24b, respectively. In this embodiment, the control circuit 22 is configured to control each current direction circuit 24a and 24b using a separate control signal having at least three possible states: in a first state, one of the thyristors is switched on; in a second state, the other of the thyristors is switched on; and in a third state, neither of the thyristors is switched on. As described above, additional current direction circuits can be added to prevent unwanted current flow between the electro-optical devices 40a and 40b and the RC circuits 26a and 26b during periods when no current can flow from the transformer 18 to the electro-optical devices 40a and 40b and the RC circuits 26a and 26b.

[0087] Figure 5B The fifth embodiment enables the complete independent driving and control of each electro-optical device 40a, 40b. The polarity of the AC output voltage can be switched in a timely manner to reduce peak current, thereby reducing the peak load on the AC voltage source 16.

[0088] The integrator RC circuit 26 in the above embodiment can be implemented in different ways. Figure 6 In the sixth embodiment, the integrating circuit 26 includes a current detection circuit 32, such as a current probe or a resistor with low resistance combined with a voltage sensor. Suitable circuitry, such as a microprocessor or suitable analog circuitry, is configured to integrate the current over time to determine the amount of charge supplied to the electro-optic device 40. The integrating circuit 26 further generates and outputs an input signal 28 corresponding to the detected amount of charge.

[0089] In this sixth embodiment, particularly if the integrating circuit 26 includes a microcontroller for integrating the current, the input signal 28 can be implemented as a signal with two possible states, such as a high state and a low state, where the low state indicates that the current direction should be maintained to charge the electro-optical device 40 and the high state indicates that the current direction should be reversed. Furthermore, the integrating circuit 26 can be combined with the control circuit 22 in a single microprocessor.

[0090] More generally, the present invention is not limited to any particular embodiment of the control circuit 22 or the manner in which the input signal 28 is generated. Therefore, any integration of the control circuit 22 and any circuitry used to generate the input signal 28 is contemplated.

[0091] Figure 7A seventh embodiment is shown, wherein the RC circuit 26 is provided with a variable resistor 264 having a variable resistance. Using a manually controllable resistor, the drive circuit can be configured to operate with a wide variety of electro-optical devices, wherein the charging of the integrating RC circuit 26 can be adapted to the connected electro-optical device 40 by adjusting the resistance of the variable resistor 264.

[0092] In a particular embodiment, the variable resistor 264 may have an electronically controllable resistance. In such an embodiment, the control circuit 22 may be configured to control the resistance of the variable resistor 264. For example, the charging characteristics of the electro-optic device 40 may not be constant, and may depend on temperature. To compensate for varying charging behavior, the control circuit 22 may adjust the resistance of the variable resistor 264 in response to a detected temperature.

[0093] It should be noted that, particularly for open-roof components of vehicles, a wide range of operating temperatures can occur. On a sunny summer day, the temperature at the roof can rise to approximately 80 degrees Celsius, while in winter, it can drop to -30 degrees Celsius or even lower. Therefore, if temperature dependence exists, the drive circuit may be preferred to adapt the drive current (e.g., the AC frequency of the drive current) to the actual temperature. Of course, such an adaptive drive circuit is not limited to the drive circuit according to the present invention. Other drive circuits can also be configured to adapt to actual conditions and circumstances related to the charging behavior of the electro-optical device 40. For example, the drive circuit disclosed in US2019 / 0041668 can be configured to adjust the AC frequency of the output voltage in response to certain conditions.

[0094] Of course, similar results can be achieved in other embodiments. For example, capacitor 261 may have a variable capacitance, or integrator 26 may be implemented in different ways to adapt input signal 28 to the varying charging behavior of electro-optic device 40.

[0095] To provide more control over the charging behavior of the electro-optical device 40, Figure 8A and 8B The eighth and ninth embodiments are respectively provided with controllable voltage amplitudes. Such controllable voltage amplitudes can be used to provide intermediate states of the electro-optic device 40, for example, providing a semi-transparent state instead of only providing a completely transparent state or a completely opaque state.

[0096] exist Figure 8A In the eighth embodiment, the control circuit 22 is operatively connected to the AC voltage source 17, wherein the output voltage amplitude of the AC voltage source 17 can be changed.

[0097] exist Figure 8BIn the ninth embodiment, an additional voltage regulation circuit 34 is included in the drive circuit 20. This voltage regulation circuit 34 may be preferred compared to the eighth embodiment if the AC voltage source 16 does not have a controllable AC voltage amplitude, for example, if it is arranged relatively far from the drive circuit 20. The voltage regulation circuit 34 can take any suitable form. Alternatively or additionally, the transformer 18 can be implemented as, for example, an autotransformer, wherein the connection to the second winding is adaptable so that the number of windings in the second winding is variable.

[0098] The voltage can be progressively controllable, or it can be controlled to one of a finite number of possible amplitudes. Furthermore, the voltage amplitude can be electronically controlled by control circuit 22 or another control circuit, or it can be manually controllable.

[0099] Figure 9 Showing the open roof component Figure 1B An exploded view is shown. In the open roof assembly shown, the movable enclosure 2a is provided with a switchable glass panel, wherein the switchability is provided, for example, by a PDLC layer stacked between two glass layers. The PDLC layer forms an electro-optic device controlled by a drive unit 42, wherein the drive unit 42 includes a transformer and a drive circuit according to the invention. The AC power supply voltage can be provided by the control unit 11 on a power cable 44, or it can be supplied on a separate cable. The cable between the control unit 11 and the drive unit 42 can also be used to provide user control signals, such as signals for turning the PDLC on or off. In another embodiment, there may be no operational connection between the control unit 11 and the drive unit 42, for example if the user interaction module is located on or in the enclosure 2a, so that only the AC power supply voltage for operation is required.

[0100] Considering the high voltage required to drive the electro-optic PDLC layer as described above, arranging the transformer on the enclosure member 2a offers advantages in terms of safety. However, the invention is not limited to any embodiment in which the transformer is small and arranged on a movable enclosure member. On the other hand, it should also be noted that placing the transformer on a movable enclosure member does not necessarily require the drive circuit according to the invention, and other drive circuits for reducing the AC frequency of the output voltage can also be used to achieve the advantages of arranging the transformer on the enclosure member. Furthermore, it should be noted that the same advantage is achieved by arranging the transformer and drive circuit on a fixed glass panel or any other type of glass panel, thereby keeping the length of the high-voltage cable shorter.

[0101] Specific embodiments of the invention have been disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the invention, which can be implemented in various forms. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as the basis for the claims and as a representative basis for teaching those skilled in the art to utilize the invention in various ways with any suitable specific structure contemplated. In particular, features set forth and described in the individual dependent claims may be applied in combination, and thus any advantageous combinations of such claims are disclosed.

[0102] Furthermore, it is anticipated that structural elements can be generated by applying three-dimensional (3D) printing technology. Therefore, any reference to structural elements is intended to cover any computer-executable instructions that instruct a computer to generate such a structural element using 3D printing technology or similar computer-controlled manufacturing techniques. Additionally, any such reference to structural elements is also intended to cover a computer-readable medium carrying such computer-executable instructions.

[0103] Furthermore, the terms and phrases used herein are not limiting but rather provide an understandable description of the invention. When used herein, the term "a" is defined as one or more. When used herein, the term "multiple" is defined as two or more. When used herein, the term "another" is defined as at least a second or more. When used herein, the term "comprising" and / or "having" is defined as including (i.e., open-ended language). When used herein, the term "connection" is defined as a connection, but not necessarily a direct connection.

[0104] Therefore, the invention has been described, and it will be apparent that the invention can be varied in many ways. Such modifications should not be considered as departing from the spirit and scope of the invention, and all such modifications, which will be apparent to those skilled in the art, are intended to be included within the scope of the following claims.

Claims

1. A driving circuit (20) for driving an electro-optical device (40), the driving circuit (20) comprising: • A set of input terminals (201, 202) for receiving an AC input voltage of a first frequency. • A set of output terminals (206, 207) for supplying AC output voltage at a second frequency; • Control circuit (22), which generates a control signal based on the input signal (28); as well as • Current direction circuit (24), which is used to control the current flow direction between the input terminals (201, 202) and the output terminals (206, 207) in response to the control signal; The characteristic feature is that the input signal represents the monitored charging state of the electro-optic device (40), and the control circuit (22) and the current direction circuit (24) are thus configured to control the second frequency based on the monitored charging state of the electro-optic device.

2. The driving circuit (20) according to claim 1, characterized in that, The first frequency is higher than the second frequency.

3. The driving circuit (20) according to claim 1, characterized in that, The control signal has two possible states, and the current direction circuit (24) is configured to allow the current to flow in only one of the two possible directions depending on the actual state of the control signal.

4. The driving circuit (20) according to claim 3, characterized in that, The control circuit (22) includes a bistable multivibrator circuit.

5. The driving circuit (20) according to claim 1, characterized in that, The control circuit (22) includes an integrator circuit (26) configured such that the voltage at one of the output terminals of the set of output terminals (206, 207) determines the charge on the integrator circuit (26).

6. The driving circuit (20) according to claim 5, characterized in that, The integrator circuit (26) includes an RC integrator circuit, wherein a series connection of a resistor (262) and a capacitor (261) is connected between two output terminals of the set of output terminals (206, 207), and wherein the control circuit (22) is configured to use the node voltage at the node (263) between the resistor (262) and the capacitor (261) as the input voltage.

7. The driving circuit (20) according to claim 6, characterized in that, The resistance of the resistor (262) can be selected to control the second frequency.

8. The driving circuit (20) according to claim 1, characterized in that, The current direction circuit (24) includes a first diode (241) and a second diode (242), wherein the control signal determines which of the first diode (241) and the second diode (242) can conduct current.

9. The driving circuit (20) according to claim 1, characterized in that, The control circuit (22) includes a microcontroller device configured to control the control signal according to the input signal (28).

10. The driving circuit (20) according to claim 1, characterized in that, The drive circuit (20) is connected to at least one optically switchable film.

11. The driving circuit (20) according to claim 10, characterized in that, The drive circuit (20) is connected to multiple segments of one or more optically switchable films.

12. An open roof assembly including a movable closure member (2a), wherein the movable closure member (2a) includes an electro-optic device (40), a transformer (18), and a drive circuit (20) for driving the electro-optic device (40) according to claim 1, and wherein the transformer (18) and the drive circuit (20) are mounted on the closure member (2a).

13. A method for driving an electro-optical device (40), the method comprising: • Receives an AC input voltage of a first frequency at a set of input terminals (201, 202); as well as • Generates a second frequency AC output voltage at a set of output terminals (206, 207); The second frequency is controlled by the following steps based on the charging state monitored by the electro-optical device: • Generate a control signal based on the input signal (28), the input signal representing the monitored charging state of the electro-optical device; and • In response to the control signal, control the direction of current flow between the input terminals (201, 202) and the output terminals (206, 207).

14. The method according to claim 13, characterized in that, The input signal (28) is generated by an integrator circuit (26) including an RC integrator circuit, wherein a resistor (262) and a capacitor (261) are connected in series, wherein the resistance of the resistor (262) is selectable for controlling the second frequency, and the method includes an additional step of calibrating the resistance of the resistor (262) to mimic the charging behavior of the electro-optic device (40).

15. The method according to claim 13, characterized in that, The method further includes the step of determining the actual conditions of the electro-optical device (40), and wherein the step of generating the AC output voltage of the second frequency at the set of output terminals (206, 207) includes taking into account the actual conditions.

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