WO2024118563A1

WO2024118563A1 - Driver circuit, optical system using the driver circuit, and method to control optical device

Info

Publication number: WO2024118563A1
Application number: PCT/US2023/081277
Authority: WO
Inventors: Ami Hazani
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2022-11-30
Filing date: 2023-11-28
Publication date: 2024-06-06
Anticipated expiration: 2025-05-30

Abstract

A driver circuit, suitable for an optical system, that includes at least one substrate having an adjustable optical characteristic, includes an input voltage source, an inverter, and a controller. The input voltage source is configured to supply adjustable input voltage. The inverter is electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage according to the input voltage, an amplitude of the AC output voltage correlating to a level of the input voltage. The controller is electrically coupled to the inverter and is configured to control the duty ratio of the AC output voltage when the adjustable input voltage is equal to or lower than a threshold.

Description

DRIVER CIRCUIT, OPTICAL SYSTEM USING THE DRIVER CIRCUIT, AND

METHOD TO CONTROL OPTICAL DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63/434,205 filed December 21, 2022, and U.S. Provisional Application No. 63/428,777 filed November 30, 2022, the content of each of which is incorporated herein by reference in their entirety.

TECHNICAL FIELD

[0002] This disclosure is generally related to a driver circuit, and more particularly to a driver circuit that may be configured to drive an optical system.

BACKGROUND

[0003] Smart windows can be driven to control its optical characteristic, such as tint level. Certain kinds of smart windows can be embedded with different types of material, such as liquid crystal. These smart windows are responsive to the voltage, current, or different kinds of electrical signal(s). To drive the windows to reach a different tint level, a wide range of the driver’s output may be needed, and sometime, it can be challenging to implement this wide range of driver’s output.

SUMMARY

[0004] This summary is a brief description of certain aspects of this disclosure. It is not intended to limit the scope of this disclosure.

[0005] An embodiment of this disclosure provides a driver circuit, including: an input voltage source, configured to supply an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage in response to the input voltage, an amplitude of the AC output voltage is dynamically correlated to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control the duty ratio of the AC output voltage when the adjustable DC input voltage is equal to or lower than a threshold.

[0006] Another embodiment of this disclosure provides a driver circuit, including: a substrate, have an adjustable optical characteristic; a driver circuit electrically coupled to the substrate to adjust the optical characteristic, the driver circuit comprising: an input voltage source supplying an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage in response to the input voltage, an amplitude of the AC output voltage is dynamically correlated to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control the duty ratio of the AC output voltage when the adjustable input voltage is equal to a minimum operating voltage of the inverter.

[0007] Another embodiment of this disclosure provides an optical system, including: a substrate, have an adjustable optical characteristic; a driver circuit electrically coupled to the substrate to adjust the optical characteristic, the driver circuit comprising: an input voltage source supplying an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage in response to the input voltage, an amplitude of the AC output voltage is dynamically correlated to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control the duty ratio of the AC output voltage when the adjustable input voltage is equal to or lower than a threshold.

[0008] Still another embodiment of this disclosure provides a method to control an optical device, including: receiving a control signal; adjusting an amplitude of an alternating current (AC) output voltage provided for driving a substrate to control the substrate according to the control signal; determining whether an amplitude of an input voltage is equal to or less than a threshold value; and adjusting a duty ratio of the AC output voltage when the amplitude of DC input voltage is equal to or less than the threshold value.

[0009] Still another embodiment of this disclosure provides an electronic apparatus, including a memory storing one or more programs and a processor electrically coupled to the memory and configured to execute the one or more programs to perform any method or step or their combination in this disclosure.

[0010] Still another embodiment of this disclosure provides non-transitory computer- readable storage medium, storing one or more programs, the one or more program being configured to, when executed by a processor, cause to perform any method or step or their combination in this disclosure.

[0011] The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various exemplary embodiments of the present disclosure are described in detail below with reference to the following drawings. The drawings are provided for purposes of illustration only and merely depict exemplary embodiments of the present disclosure to facilitate the understanding of the present disclosure. Therefore, the drawings should not be considered as limiting of the breadth, scope, or applicability of the present disclosure. It should be noted that for clarity and ease of illustration these drawings are not necessarily drawn to scale.

[0013] Fig. 1 shows an optical system with adjustable optical characteristics including an embodiment of a driver circuit, as set forth in one or more embodiments of the present disclosure;

[0014] Fig. 2 shows an exemplary driver circuit configured to output AC output voltage, in accordance with one or more embodiments of the present disclosure; [0015] Fig. 3 shows an exemplary inverter circuit implemented with an H-bridge circuit, in accordance with one or more embodiments of the present disclosure;

[0016] Fig. 4 shows an exemplary AC output voltage from an embodied driver circuit, in accordance with one or more embodiments of the present disclosure;

[0017] Fig. 5 shows an exemplary wave form for generating a command in the driver circuit, in accordance with one or more embodiments of the present disclosure;

[0018] Fig. 6 shows another exemplary driver circuit with a detector, in accordance with one or more embodiments of the present disclosure; and

[0019] Fig. 7 shows an example operational flow diagram method, according to one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

[0020] Smart window technology can use liquid crystal material, or other kinds of material, whose transparency can be adjusted according to the electrical characteristic applied on it. The systems and method disclosed herein allow these kinds of smart windows to be driven by lower AC (Alternating Current) RMS voltage to allow a low power consumption solution that is also much more responsive to optical characteristic control / voltage changes (has a shorter response time). To drive the smart window at different optical characteristics, such as tint levels or color, a wide range of AC RMS voltages ranging from zero voltage to the maximum allowed voltage may be provided.

[0021] Fig. 1 shows an optical system with adjustable optical characteristics (such as tint levels or colors) in accordance with one or more embodiments of the present disclosure. The system includes a remote control application 210, an internet router 220, and a control panel 230. The control panel 230 may be used to control multiple sets of optical devices 240, such as smart windows. The smart windows may have a substrate that can carry the suitable material (such as liquid crystal material) to adjust the tint level of the optical devices 240. For example, a smart window may have two substrate sandwiching liquid crystal material therebetween. The control panel 230 can output different kinds of driving voltage or current to change the status of the material and the optical characteristics, and thereby, the tint levels may be adjusted. The remote control application 210 can be configured to give the command to the respective optical devices 240. The command can be provided to the local control panel 230, such that the local control panel 230 can provide the corresponding commands, or driving signals, to the optical devices 240. The local control panel 230 can also receive inputs directly from a user, and the commands or driving signals can be generated in response to the inputs from the local user. The remote control application 210 can have a wireless or wired communication with the optical devices 240 (e.g., via the internet router 220). The control panel 230 can also provide the commands or control signals to the smart windows in a wired or wireless manner. In an implantation, the application 210 can provide the command via wireless or non-wireless communication via the control panel 230 or directly to the driver circuit 100 as a local communication or as a remote communication via the cloud (such as internet or web application).

[0022] Fig. 2 shows an exemplary driver circuit 100 according to one or more embodiments of the present disclosure. The driver circuit 100 can be implemented in the control panel 230, or can be implemented as an intermediate device between the control panel 230 and the optical devices 240. Also, the driver circuit 100 can be implemented on the group of the optical devices 240, and a group of the optical devices 240 can share one driver circuit 100.

[0023] For example, each optical device 240 (e.g., a smart window) can be provided with one driver circuit 100. In this case, the driver circuit 100 may provide one output for the optical device 240. The driver circuit 100 may communicate with a control system, such as the control panel 230 and/or the remote control application 210 to drive the optical device 240 according to the command from the control system. Alternatively, the driver circuit 100 may be configured to drive a group of optical devices 240. As shown in Fig. 2, in this case as an example, the driver circuit 100 may provide multiple outputs to each optical device 240. It is noted that a group of optical devices 240 may also share a single output from the driver circuit 100. As an example, the driver circuit 100 may be configured with the control panel 230, and as another example, the driver circuit 100 may be separately configured with the control panel 230. Either implementation can be configured to drive a single optical device 240 or to drive a group of optical devices 240. The various exemplary implementations above can also be combined or otherwise modified. While the components in Fig. 1 are configured in an exemplary arrangement, but the different components can be integrated together or alternatively implemented by multiples components.

[0024] The driver circuit 100 may include one or more input voltage sources 110 supplying input voltage Vcc (or respective Vccl~Vcc4 in a multiple input system), one or more inverter(s) 120, and one or more controller(s) 130. The input voltage source 110 may be a DC voltage source configured to dynamically supply adjustable DC input voltage Vcc based on a DC or AC input supply 111. The inverter 120 is electrically coupled to the DC input voltage source 110 to receive the DC input voltage Vcc, and the inverter 120 is configured to generate an alternating current (AC) output voltage Vout according to the DC input voltage provided by input voltage source 110. In other examples, the input voltage source(s) 110 may receive an AC input supply, which is converted to the DC input voltage Vcc. The amplitude of the AC output voltage Vout may be dynamically correlate to a level of the DC input voltage Vcc. The controller 130 is electrically coupled to the inverter 120 and is configured to dynamically control the duty ratio of the AC output voltage Vout when certain conditions are met, for example, when the adjustable DC input voltage Vcc is equal to or lower than a predetermined threshold value, meaning that a duty ratio control can be enabled when the DC input voltage is equal or is lower compared to the threshold value. As an example, the DC input voltage source Vcc is supplied by the input voltage sources 110 via a voltage converter 112, electrically coupled to the inverter 120. The voltage converter 112 can be a step down voltage converter, a DC to DC voltage converter, or a step down DC to DC voltage converter, a step up voltage converter, an AC to DC voltage converter, or other types of voltage converters. The amplitude of the output AC output voltage Vout can be, as an example, in a positive or negative correlation to the voltage level of the DC input voltage Vcc.

[0025] For example, the inverter 120 can be an H-bridge circuit 302 as shown in Fig. 3 in accordance with one or more embodiments of the present disclosure. The H-bridge circuit 302 includes four transistors Q1-Q4 (304) and a gate driver 306 to drive the transistors Q1-Q4 (304). When transistor QI and Q3 are turned on and Q2 and Q4 are turned off, the AC output voltage Vout is about Vcc, assuming the transistors are idea switches. In implementations, there may be some voltage drop between the transistors. Alternatively, when transistor QI and Q3 are turned off and Q2 and Q4 are turned on, the Vout is about - Vcc. As explained, the actual output in implementations may have some voltage drop between the transistors. The pair of QI and Q3 and the other pair of Q2 and Q4 may be turned on and off alternatingly, such that the Vout can be an AC voltage, between approximately +Vcc and -Vcc. As an example, the AC output voltage can be a rectangular wave. As explained above, the DC input voltage Vcc may be adjustable by dynamically adjusting the output of the input voltage source 110, Vcc, therefore, the amplitude of the AC output voltage Vout can be adjustable by adjusting the voltage level of DC input voltage Vcc. Additionally, to ensure the zero average output voltage Vout, the voltage of the capacitive load can be discharged to zero or near zero voltage during the “Off’ time of the duty cycle, in addition to control the duty cycle of the “On” time of the duty cycle. This technique can be implemented by turning off QI and Q2 and turning on Q3 and Q4 at the same time or the opposite.

[0026] While dynamically adjusting the voltage level the input voltage Vcc can adjust the amplitude of the AC output voltage Vout to generate an AC voltage with different amplitudes, the adjustable range of DC input voltage Vcc may be limited due to the nature of the inverter. Using the H-bridge circuit 302 as an example, to keep the transistor working, there may be a minimum Vcc voltage level, which can be, for example, the threshold voltage of the transistor. Therefore, there is an H-Bridge minimum operating voltage (or inverter minimum operating voltage) that is required to operate the H-bridge circuit 302. On the other hand, the device, such as a smart window, may need a smaller AC voltage amplitude to reach a specific tint level, which may require a DC input voltage Vcc level less than the minimum Vcc voltage level. Therefore, another technique may be implemented to extend the dynamically adjustable range of the DC input voltage level Vcc.

[0027] As an example, with reference to Figs. 2 and 3, the controller 130 may be used to provide a command Tc to the inverter 120, such that the duty ratio of the AC output voltage Vout can be dynamically adjusted. The command Tc can implement, for example, a PWM (Pulse Width Modulation) control, so as to control the duty ratio of the AC voltage at a predetermined period. For example, the controller 130 can be a timing circuit that is based on 100 Hz operation divide by two frequency dividers. The two dividers can provide 50Hz control signal with a 50% duty cycle. In an example, when the DC input voltage Vcc is equal to or lower than a threshold value (or at any circumstance the circuit reaches it limit to provide desired output without the duty ratio control), the duty ratio control of the controller 130 can step in to adjust the duty ratio of the AC output voltage Vout in order to simulate an AC output voltage Vout having a lower amplitude, while the peak value of the AC output voltage Vout stays at a minimum value the H-bridge 302 can provide (because the amplitude of the DC input voltage Vcc has reach an lowest acceptable value). The threshold value can be, but not necessarily, the H-Bridge minimum operating voltage. Instead, the threshold value can be a value determined based on the need of the circuit or the intended driving performance. For example, the threshold value for the controller 130 to turn on the duty ratio control can be higher than the threshold voltage of the transistors of the H-bridge 302. In another example, the threshold value can be the minimum operating voltage of the H-bridge. Additionally, the threshold value is not necessary a fixed value or a single value, it can be a set of values and/or dynamically adjustable value(s) used to decide whether to enable a duty ratio control of the AC output voltage Vout.

[0028] Once the duty ratio control is enabled, the duty ratio of the AC output voltage Vout can be dynamically adjusted according to the tint control signal (Tic) as the controller 130 may receive a tint control signal Tic’. Once the duty ratio control scheme is enabled, the duty ratio of the AC output voltage Vout may be smaller than the original duty ratio when the DC input voltage Vcc is above the threshold value and when the duty ratio control is disabled. Therefore, the AC output voltage Vout may have a first duty ratio when the DC input voltage Vcc is greater than the threshold value and a second duty ratio when the DC input voltage Vcc is less than the threshold value. The first duty ratio can be greater than the second duty ratio. In an example, the first duty ratio of the AC output voltage can be 50%, and the second duty ratio, when the duty ratio control is implemented, can be less than 50%. [0029] According to an implementation, the controller 130 can be a timing logic. The command Tc provided by the controller 130 can be one or more digital signal(s). The inverter 120 may further include the gate driver 306 (as shown in Fig. 3), which is configured to convert the command Tc into gate signals C1-C4 to drive the gate of the transistors Q1-Q4 (304) to generate an AC output voltage with a proper duty ratio. Alternatively, the command Tc can be used to control the inverter 120, such as transistors included in the inverter 120, without intermediate circuitry such as the gate driver 306. In examples, the command Tc can include a set of signals that can directly control the gates of the transistor of the H-bridge. The driver circuit 100 may further include a converter 150, which can be configured to receive the DC or AC input supply 111 and convert the DC or AC input supply 111 as a suitable power source for other circuit component (s) in the driver circuit 100.

[0030] Fig. 4 shows an exemplary wave form of the AC output voltage in accordance with one or more embodiments of the present disclosure. In this example, the AC output voltage can be a rectangular wave. Exemplarily, the AC output voltage may be controlled by the controller 130 to have a positive level (e.g., about +Vcc), a negative level (e.g., about - Vcc), and an intermediate level (e.g., about 0V), where about is +/- ,2V. The AC output voltage may be maintained at the intermediate level by the controller 130 for a predetermined time period (e.g., Td) when the AC output voltage Vout transitions between the positive level and the negative level. As explained above, the positive level and the negative level, defining the amplitude of the AC output voltage can be adjustable by, for example, adjusting the voltage level of the DC input voltage Vcc. In some applications, the device driven by the driver circuit 100 can be of a substantially capacitive characteristic; therefore, the switch from the first polarity to the second polarity of the voltage across the capacitive component may cause a high peak of charging or discharging currents. The driver circuit 100 can output the AC output voltage Vout having the intermediate voltage level between the transition of two polarities, so as to reduce the peak charging or discharging current. As an example, the period Td may be long enough to allow the driven device to be substantial discharged or charged. In some case, the Td may be longer, or shorter, or be set to zero.

[0031] In an embodiment, a resistance can be added between the load, such as a smart window, and the output port of the driver circuit 100. Thereby, the output voltage Vout is provided to a series of a resistance and a capacitance, which can reduce the large peak charging and discharging current.

[0032] As shown in Figs. 1 and 2, the driver circuit 100 may include multiple inverters

120. Each inverter 120 can be used to generate respective AC output voltages Vout. Each of the AC output voltages can be used to drive one or more respective devices, such as one or more smart windows. Additionally, the driver circuit 100 can include multiple input voltage sources 110, such as converters 112, each outputting respective DC input voltage Vcc for a corresponding inverter 120. Similarly, the controller 130 can output respective command Tc for each inverter 120, such that the duty ratio of each AC output voltage Vout of the respective inverter 120 can be controlled separately. It should be noted that while each inverter 120 can have its own command Tc and input voltage sources 110 that supplies the respective DC input voltage Vcc. In examples, one or more inverters 120 can share the same command Tc and/or the DC input voltage Vcc provided from a shared input voltage source 110. Further, while the exemplary drawings shows four output voltages Vout and four converters 112 and inverters 120, the number of the outputs is not limited by this example. [0033] As shown in Fig. 2, the driver circuit may receive a tint control signal Tic from a control panel 230. The tint control signal Tic can be an analog signal or a digital signal. The tint control signal Tic can be a set of separate signals for respective optical devices. The tint control signal Tic can be output by a digital to analog converter. The tint control signal Tic can be provided, as one or more PWM signals, to one or a set of low pass filters (LPF) 135, respectively, before it is used to drive the converter to provide the DC input voltage.

Alternatively, the one or more PWM signals with the low pass filter(s) can be replaced with a digital to analog converter (DAC), which may receive one or a set of digital tint control signal(s) Tic and provide one or a set of converted analog tint control signal(s) to the respective DC-DC voltage converter. It should be noted that the above disclosure just named a few examples that may be used to generate the control signals, and the other implementation may be used to generate compatible control signals.

[0034] As shown in Fig. 5, which shows an exemplary wave form for generating a command in the driver circuit, in accordance with one or more embodiments of the present disclosure, the controller 130 may generate an analog saw tooth signal Tsw as a reference signal. The reference signal may be compared with the converted tint signal Tic’ received by the controller so as to generate the command Tc from the controller. The command Tc may be used to control the duty ratio of the inventor(s).

[0035] Fig. 6 shows another driver circuit example according to one or more embodiments of the present disclosure. In this embodiment, while most of the structure and function of the driver circuit has been explained above, the driver circuit 100 in this embodiment may further include a detector. The detector 140 is electrically coupled to the input voltage source 110 and configured to detect an output current of the input voltage source 110. For example, the detector 140 can be a load current sensor or an inrush current pulses detector. The detector 140 can be implemented by a hall sensor or other kinds of current detectors. The detection result can be provided to a visual indicator, such as an LED, a micro controller or other user interface or controller for monitoring and/or control purposes. If the driver circuit 100 has multiple output AC voltage ports, each supply input voltage Vcc can be coupled to a detector 140 or multiple detectors 140 to detect the respective output current.

[0036] Fig. 7 illustrates an example operational flow diagram method to control an optical device according to one or more embodiments of the present disclosure. The example includes:

SI 10: Receiving a control signal;

S120: Adjusting an amplitude of an alternating current (AC) output voltage provided for driving a substrate to control the substrate according to the control signal;

S130: Determining whether an amplitude of a DC input voltage is equal to or lower than a threshold value; and

S140: Adjusting a duty ratio of the AC output voltage when the amplitude of DC input voltage is equal to or lower than the threshold value.

[0037] At SI 10, a control signal, such as an optical characteristic control signal, a tint level control signal, or a actuation control signal, may be provided in response to a user instruction from a control panel 230 or other sources.

[0038] At S120, the system may adjust an amplitude of an AC output voltage provided for driving a substrate to control the tint level of the substrate according to the tint control signal. As explained above, the amplitude of the AC output voltage can be controlled or adjusted, for example, by adjusting a DC input voltage.

[0039] At S130, the system may calculate whether an amplitude of a DC input voltage is equal to or lower than a threshold value, and if so, the system may at S140 adjust a duty ratio of the AC output voltage Vout, such that the AC output voltage Vout can simulate a voltage having a lower average amplitude by reducing the duty ratio.

[0040] Further, an example operational method may include maintaining a voltage level of the AC output voltage at an intermediate level for a period when the AC output voltage transitions between a positive level and a negative level. The duty ratio of the AC output voltage can be adjusted according to the tint control level, to provided required averaged AC output voltage level to the driven device. As an example, the waveform of the AC output voltage is shown in Fig. 4.

[0041] Further, an example operational method may include maintaining a duty ratio of the AC output voltage while adjusting the amplitude of the AC output voltage according to the tint control signal.

[0042] According to one embodiment, this disclosure further provides a device including: means for receiving a tint control signal; means for adjusting an amplitude of an alternating current (AC) output voltage provided for driving a substrate to control the tint level of the substrate according to the tint control signal; means for determining whether an amplitude of a DC input voltage is equal to or lower than a threshold value; and means for adjusting a duty ratio of the AC output voltage when the amplitude of DC input voltage is equal to or lower than the threshold value.

[0043] The methods, devices, processing, circuitry, and logic described above may be implemented in many different ways and in many different combinations of hardware and software. For example, all or parts of the implementations may be circuitry that includes an instruction processor or controller, such as a Central Processing Unit (CPU), microcontroller, or a microprocessor; or as an Application Specific Integrated Circuit (ASIC), Programmable Logic Device (PLD), or Field Programmable Gate Array (FPGA); or as circuitry that includes discrete logic or other circuit components, including analog circuit components, digital circuit components or both; or any combination thereof. The circuitry may include discrete interconnected hardware components or may be combined on a single integrated circuit die, distributed among multiple integrated circuit dies, or implemented in a Multiple Chip Module (MCM) of multiple integrated circuit dies in a common package, as examples.

[0044] Accordingly, the circuitry may store or access instructions for execution, or may implement its functionality in hardware alone. The instructions may be stored in a tangible storage medium that is other than a transitory signal, such as a flash memory, a Random Access Memory (RAM), a Read Only Memory (ROM), an Erasable Programmable Read Only Memory (EPROM); or on a magnetic or optical disc, such as a Compact Disc Read Only Memory (CDROM), Hard Disk Drive (HDD), or other magnetic or optical disk; or in or on another machine-readable medium. A product, such as a computer program product, may include a storage medium and instructions stored in or on the medium, and the instructions when executed by the circuitry in a device may cause the device to implement any of the processing described above or illustrated in the drawings.

[0045] The implementations may be distributed. For instance, the circuitry may include multiple distinct system components, such as multiple processors and memories, and may span multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be logically and physically organized in many different ways, and may be implemented in many different ways. Example implementations include linked lists, program variables, hash tables, arrays, records (e.g., database records), objects, and implicit storage mechanisms. Instructions may form parts (e.g., subroutines or other code sections) of a single program, may form multiple separate programs, may be distributed across multiple memories and processors, and may be implemented in many different ways.

Example implementations include stand-alone programs, and as part of a library, such as a shared library like a Dynamic Link Library (DLL). The library, for example, may contain shared data and one or more shared programs that include instructions that perform any of the processing described above or illustrated in the drawings, when executed by the circuitry. [0046] In some examples, each unit, subunit, and/or module of the system may include a logical component. Each logical component may be hardware or a combination of hardware and software. For example, each logical component may include an application specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA), a digital logic circuit, an analog circuit, a combination of discrete circuits, gates, or any other type of hardware or combination thereof. Alternatively or in addition, each logical component may include memory hardware, such as a portion of the memory, for example, that comprises instructions executable with the processor or other processors to implement one or more of the features of the logical components. When any one of the logical components includes the portion of the memory that comprises instructions executable with the processor, the logical component may or may not include the processor. In some examples, each logical component may just be the portion of the memory or other physical memory that comprises instructions executable with the processor or other processor to implement the features of the corresponding logical component without the logical component including any other hardware. Because each logical component includes at least some hardware even when the included hardware comprises software, each logical component may be interchangeably referred to as a hardware logical component.

[0047] A second action may be said to be "in response to" a first action independent of whether the second action results directly or indirectly from the first action. The second action may occur at a substantially later time than the first action and still be in response to the first action. Similarly, the second action may be said to be in response to the first action even if intervening actions take place between the first action and the second action, and even if one or more of the intervening actions directly cause the second action to be performed. For example, a second action may be in response to a first action if the first action sets a flag and a third action later initiates the second action whenever the flag is set.

[0048] To clarify the use of and to hereby provide notice to the public, the phrases "at least one of <A>, <B>, . . . and <N>" or "at least one of <A>, <B>, . . . <N>, or combinations thereof or "<A>, <B>, . . . and/or <N>" are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, ... and N. In other words, the phrases mean any combination of one or more of the elements A, B, ... or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed. [0049] Various exemplary embodiments of the present disclosure are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the present disclosure. The present disclosure is not limited to the exemplary embodiments and applications described and illustrated herein. Additionally, the specific order and/or hierarchy of steps in the methods disclosed herein are merely exemplary approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present disclosure. Thus, those of ordinary skill in the art would understand that the methods and techniques disclosed herein present various steps or acts in exemplary order(s), and the present disclosure is not limited to the specific order or hierarchy presented unless expressly stated otherwise.

[0050] This disclosure is intended to cover any conceivable variations, uses, combination, or adaptive changes of this disclosure following the general principles of this disclosure, and includes well-known knowledge and conventional technical means in the art and undisclosed in this application. For example, a disclosure of a sub-combination can be applied to a variety of disclosed combination in the present disclosure. Two sub-combinations as disclosed can be combined to form a new combination. A method in the present disclosure can be implemented by or implemented on each disclosed device, if applicable.

[0051] It is to be understood that this disclosure is not limited to the precise structures or operation described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope of this application. The scope of this application is subject only to the appended claims.

Claims

CLAIMS What is claimed is:

1. A driver circuit, comprising: an input voltage source, configured to supply an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage according to the input voltage, an amplitude of the AC output voltage correlating to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control a duty ratio of the AC output voltage when the adjustable input voltage is equal to or lower than a threshold value.

2. The driver circuit of claim 1, wherein the alternating current (AC) output voltage is a rectangular wave, the input voltage source is a direct current (DC) input voltage source, and the inverter comprises H bridge circuitry.

3. The driver circuit of claim 1, wherein the input voltage source comprises a DC to DC convertor and is configured to convert a DC source voltage to the input voltage.

4. The driver circuit of any one of claims 1 to 3, wherein the AC output voltage has a first duty ratio when the input voltage is greater than the threshold value and a second duty ratio when the input voltage is less than the threshold value, the first duty ratio being greater than the second duty ratio.

5. The driver circuit of claim 4, wherein the second duty ratio is less than 50%.

6. The driver circuit of any one of claims 1 to 3, wherein the controller is configured to control the inverter to generate the AC output voltage having a positive level, a negative level, and an intermediate level, the AC output voltage maintained by the controller at the intermediate level for a predetermined time period when the AC output voltage transitions between the positive level and the negative level.

7. The driver circuit of any one of claims 1 to 3, further comprising a detector, electrically coupled to the input voltage source to detect an output current of the input voltage source.

8. The driver circuit of any one of claims 1 to 3, wherein the input voltage source and the controller are further configured to receive an optical characteristic control signal, a level of the input voltage dynamically adjusted by the input voltage source in response to the optical characteristic control signal, and the controller is configured to adjust the duty ratio of the AC output voltage according to the optical characteristic control signal.

9. The driver circuit of claim 8, wherein the optical characteristic control signal is used to control a tint level of an optical device.

10. The driver circuit of any one of claims 1 to 3, wherein the inverter comprises an H-bridge circuit and the threshold value is about the minimum operating voltage of the H- bridge.

11. An optical system, comprising: at least one substrate, have an adjustable optical characteristic; a driver circuit electrically coupled to the at least one substrate to adjust the optical characteristic, the driver circuit comprising: an input voltage source supplying an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate a first alternating current (AC) output voltage in response to the input voltage, an amplitude of the first AC output voltage is dynamically correlated to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control a duty ratio of the first AC output voltage when the adjustable input voltage is equal to or lower than a threshold value.

12. The optical system of claim 11, wherein the alternating current (AC) output voltage is a rectangular wave, the input voltage source is a direct current (DC) input voltage source, and the inverter comprises an H bridge circuitry.

13. The optical system of claim 12, wherein the input voltage source comprises a DC to DC convertor and is configured to convert a DC source voltage to the input voltage.

14. The optical system of any one of claims 11-13, wherein the first AC output voltage has a first duty ratio when the input voltage is greater than the threshold value and a second duty ratio when the input voltage is less than the threshold value, the first duty ratio being greater than the second duty ratio.

15. The optical system of claim 14, wherein the second duty ratio is less than 50%.

16. The optical system of any one of claims 11-13, wherein the controller is configured to control the inverter to generate the first AC output voltage having a positive level, a negative level, and an intermediate level, the first AC output voltage maintained by the controller at the intermediate level for a predetermined time period when the first AC output voltage transitions between the positive level and the negative level.

17. The optical system of any one of claims 11-13, wherein the driver circuit further comprising a detector, electrically coupled to the voltage source to detect an output current od the input voltage source.

18. The optical system of any one of claims 11-13, wherein the input voltage source and the controller are further configured to receive an optical characteristic control signal, a level of the input voltage dynamically adjusted by the input voltage source in response to the optical characteristic control signal, and the controller is configured to adjust the duty ratio of the first AC output voltage according to the optical characteristic control signal.

19. The optical system of claim 18, wherein the optical characteristic is a tint level of the at least one substrate.

20. The optical system of any one of claims 11-19, wherein the at least one substrate is a substrate of a window.

21. The optical system of any one of claims 11-19, further comprising a control panel, in communication with the driver circuit and configured to provide an optical characteristic control signal, wherein the driver circuit is configured to generate the first AC output voltage according to the optical characteristic control signal.

22. The optical system of any one of claims 11-19, wherein the at least one substrate is plural, and the driver circuit is configured to drive the plurality of substrates.

23. The optical system of claim 22, wherein the driver circuit is further configured to generate one or more second AC output voltages, and the first AC output voltage and the one ore more second AC output voltages correspond to the respective substrates.

24. The optical system of claim 22, wherein the driver circuit is configured to drive the plurality of substrates with the first AC output voltage.

25. A method to control an optical system, comprising: receiving a control signal; adjusting an amplitude of an alternating current (AC) output voltage provided for driving a substrate to control the substrate according to the control signal; determining whether an amplitude of an input voltage is equal to or less than a threshold value; and adjusting a duty ratio of the AC output voltage when an amplitude of input voltage is equal to or less than the threshold value.

26. The method of claim 25, further comprising maintaining a voltage level of the AC output voltage at an intermediate level for a period when the AC output voltage transitions between a positive level and a negative level.

27. The method of any one of claims 25-26, further comprising maintaining a duty ratio of the AC output voltage while adjusting the amplitude of the AC output voltage according to the control signal.

28. The method of any one of claims 25-26, wherein the control signal is a tint control signal used to control a tint level of the optical system.

29. A driver circuit, comprising: an input voltage source, configured to supply an adjustable input voltage; an inverter, electrically coupled to the input voltage source and configured to generate an alternating current (AC) output voltage according to the input voltage, an amplitude of the AC output voltage correlating to a level of the input voltage; and a controller, electrically coupled to the inverter and configured to control a duty ratio of the AC output voltage when the adjustable input voltage is equal to a minimum operating voltage of the inverter.