Optical Filter Control via PWM and Polarity Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control systems for variable transmittance optical filters face challenges such as accumulation of electrical charge, limited control over operative states, and inability to maintain intermediate transmittance levels, especially due to factors like ambient light and temperature, and rely solely on forward polarity voltage application.
Innovation Solution
A control system comprising a controller, memory, and switching circuitry that transitions the optical filter assembly between states by applying voltage signals with pulse width modulation, polarity switching, and short-circuiting or open-circuiting the terminals, utilizing a light sensor for feedback to manage transmittance and address residual charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If voltage is applied across the optical filter terminals to transition to a faded state, then transmittance increases, but electrical charge accumulates on the terminals
Solution Approach 1:
The control system applies voltage in periodic pulses rather than continuously. The controller activates the optical filter in alternating cycles of application and removal, which allows the filter to reach desired transmittance levels while preventing permanent charge accumulation on the terminals. This periodic on/off cycling resolves the contradiction by achieving the desired optical state without the harmful side effect of sustained charge buildup.
Solution Approach 2:
The control system performs preliminary charge management by removing voltage before transitioning to the faded state. The controller first removes applied voltage to eliminate residual charges, then activates the optical filter only when needed. This preliminary action prevents charge accumulation from the outset while still enabling the filter to achieve high transmittance when required.
2Illumination intensity
If voltage is continuously applied to maintain faded state, then transmittance is maintained, but power consumption increases
Solution Approach 1:
The control system uses periodic pulsing to maintain the faded state rather than continuous voltage application. The controller activates voltage in controlled pulses that are sufficient to maintain transmittance, then removes it during off-periods. This approach maintains the desired optical state while dramatically reducing overall power consumption compared to continuous operation.
Solution Approach 2:
The optical filter assembly serves itself by automatically returning to the dark state when voltage is removed. The system leverages the filter's inherent property of automatically darkening without voltage, eliminating the need for continuous power consumption to maintain the faded state. The filter self-regulates its optical state based on voltage presence.
3Ease of operation
If voltage polarity is not switched, then control is simplified, but residual charges affect transition performance
Solution Approach 1:
The control system implements periodic polarity switching in a structured sequence: forward voltage application, then reverse polarity application. This periodic alternation between polarities effectively manages residual charges by clearing them through the reverse polarity phase, thereby maintaining reliable transition performance without permanently complicating the control mechanism.
Solution Approach 2:
The control system applies reverse polarity voltage after forward polarity voltage. By inverting the voltage polarity, the system counteracts and removes residual charges that accumulated during forward voltage application. This inversion technique restores clean transition conditions while maintaining a relatively simple overall control structure.
4Speed
If transition time is reduced by applying higher voltage, then response speed improves, but power consumption increases
Solution Approach 1:
The control system uses periodic high-voltage pulses to achieve fast transitions only when needed, rather than continuously applying high voltage. The controller activates high voltage in brief pulses that rapidly transition the optical filter between states, then removes it during off-periods. This achieves improved transition speed while limiting overall power consumption to only the brief moments when high voltage is actually required for rapid switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables precise control over the optical filter's transmittance, reduces transition times, and extends the filter's lifespan by effectively managing residual charges and adapting to ambient conditions, while reducing power consumption and maintaining desired operative states.
Implementation Method 1
The optical filters comprise a switching material that comprises one or more chromophores that have electrochromic and photochromic properties
Implementation Method 2
The optical filters comprise a switching material that comprises one or more chromophores that have electrochromic and photochromic properties
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
An optical filter and control system (40) suitable for a dimmable room window comprises a hybrid photochromic-electrochromic optical filter assembly (46) whose transmittance is variable, a controller (48) coupled to it which controls its transmittance (32) and a memory unit (49) coupled to the controller (48) which stores the statements and instructions to be executed by the controller (48) in order to switch the optical filter assembly (46) between operating states. The controller (48) is adapted to maintain the optical filter assembly (46) in a "hold mode" by supplying a pulse-width-modulated (PWM) voltage signal across it so that its transmittance (32) is held both at a certain average value (which can correspond to an intermediate operating state between the fully dark and fully light states) and at a certain variance; the average value of the transmittance (32) being held between lower (33) and upper (34) transmittance thresholds.