Electrochromic Window Voltage Control for Uniform Tint Transitions
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Solution Overview
Problem
Existing electrochromic devices face challenges in efficiently driving optical transitions across varying sizes and regions, leading to non-uniform transitions and inefficiencies.
Innovation Solution
A method and apparatus for controlling optical transitions in electrochromic devices by adjusting drive parameters based on charge delivery and optical state, without considering open circuit voltage, to ensure uniform transitions across the device surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive voltage is applied to all regions of the electrochromic device, then the control system is simple, but the optical transition is non-uniform across the device surface
Solution Approach 1:
The electrochromic device is divided into multiple regions (first region near first bus bar, second region near second bus bar, and third region in between) with different drive voltages applied to each region. This segmentation allows uniform optical transition control across the device surface by compensating for the voltage drop that occurs with distance from the bus bars.
Solution Approach 2:
Different drive voltages are applied to different regions of the electrochromic device based on their distance from the bus bars. The first and second regions receive higher drive voltages than the third region, creating local quality variations that compensate for the non-uniform voltage distribution and achieve uniform optical transition across the entire device.
2Speed
If high drive voltage is applied to speed up optical transition, then the switching speed increases, but excessive current flow may damage the device
Solution Approach 1:
The drive voltage is dynamically adjusted based on the distance from the bus bars and the current state of the electrochromic device. The controller applies different drive voltages to different regions, with higher voltages to regions farther from bus bars, and adjusts the voltage over time during the transition process to achieve uniform switching without excessive current that could damage the device.
Solution Approach 2:
The controller monitors the optical transition progress and adjusts the drive voltage accordingly. By measuring the actual transition state and comparing it to the desired state, the controller can optimize the drive voltage to achieve uniform transition while preventing excessive current flow that would compromise device reliability.
3Productivity
If different sized devices transition simultaneously, then the system responds quickly to commands, but faster devices may overshoot while slower devices remain incomplete
Solution Approach 1:
The controller determines the expected transition time for each device based on its size and characteristics before initiating the transition. For faster devices, the controller applies a preliminary reduced drive voltage or introduces a time delay to prevent overshooting, while slower devices receive higher drive voltages to catch up, ensuring all devices reach their target optical states simultaneously without mismatch.
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
Enables efficient and uniform optical transitions in electrochromic devices by optimizing drive parameters, allowing for simultaneous transitions and minimizing non-uniformities.
Implementation Method 1
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
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. In some cases, feedback may be used to monitor an optical transition. In these or other cases, a group of optically switchable devices may transition together over a particular duration to achieve approximately uniform tint states over time during the transition.