Electrochromic Device Voltage Control for Uniform Optical Transition
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Solution Overview
Problem
Electrochromic devices face challenges in uniformly transitioning between optical states due to variations in effective voltage across their surface, leading to non-uniform coloration and slow switching times, especially in larger devices where the center experiences lower effective voltage.
Innovation Solution
A controller and method are introduced to efficiently drive optical transitions by applying a drive voltage to bus bars, periodically monitoring open circuit voltage and total delivered charge density, and adjusting the voltage to ensure the transition is complete, using a hold voltage to maintain the ending state, and probing techniques to determine when to switch from drive to hold voltage based on current responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant drive voltage is applied to bus bars of electrochromic devices, then the device structure is simple and easy to control, but the voltage distribution across the device surface becomes non-uniform, causing non-uniform coloration and slow switching times
Solution Approach 1:
The patent applies different voltage levels to different regions of the electrochromic device by dividing the device into multiple zones with independent voltage control. Regions closer to bus bars receive lower voltage while center regions receive higher voltage, compensating for the non-uniform voltage distribution and achieving uniform optical transition across the entire device surface.
2Area of stationary object
If the device size is increased to cover larger areas, then the coverage area is improved, but the effective voltage at the center decreases due to higher resistance, slowing down the switching time
Solution Approach 1:
The patent segments the electrochromic device into multiple independently controllable zones, each with its own voltage control. This allows larger devices to be divided into smaller functional units that can be driven simultaneously, maintaining fast switching speeds across the entire large-area device by applying appropriate voltage to each segment.
3Speed
If higher drive voltage is applied to speed up the transition, then the switching time is reduced, but the regions near bus bars experience excessive voltage leading to potential damage or non-uniform transition
Solution Approach 1:
The patent implements local voltage optimization where different regions of the device receive differently tailored voltage levels. Regions near bus bars receive reduced voltage to prevent over-driving and damage, while center regions receive higher voltage to maintain fast transition speeds, achieving both rapid switching and reliable uniform operation.
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
This approach ensures uniform optical transitions across the entire surface of electrochromic devices, improving switching speed and reliability by dynamically adjusting the voltage to match the progress of the transition, thereby overcoming the limitations of non-uniform voltage distribution and size-related issues.
Implementation Method 1
Electrochromic (EC) devices are typically multilayer stacks including (a) at least one layer of electrochromic material, that changes its optical properties in response to the application of an electrical potential
Implementation Method 2
an ion conductor (IC) layer that allows ions, such as lithium ions, to move through it, into and out from the electrochromic material to cause the optical property change
Data Source
AI summary
Aspects of this disclosure concern controllers and control methods for applying a drive voltage to bus bars of optically switchable devices such as electrochromic devices. Such devices are often provided on windows such as architectural glass. In certain embodiments, the applied drive voltage is controlled in a manner that efficiently drives an optical transition over the entire surface of the electrochromic device. The drive voltage is controlled to account for differences in effective voltage experienced in regions between the bus bars and regions proximate the bus bars. Regions near the bus bars experience the highest effective voltage.