Electrochromic Glass Driver Control for Uniform Fast Switching
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Solution Overview
Problem
Current electrochromic devices experience slow and non-uniform transmissivity changes due to voltage drop issues, leading to the 'iris effect', and suffer from faradaic losses that degrade performance over time, resulting in a loss of optical transmissivity range and cell potential drift.
Innovation Solution
A driver system that applies a constant supply current to electrochromic devices, monitoring sense voltage and charge transfer, switching to variable voltage or current to maintain a sense voltage limit and terminating when a target charge is reached, thereby ensuring fast and uniform switching while protecting the device from damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional voltage application is used to charge electrochromic devices, then the device can change transmissivity, but the transmissivity change is slow and non-uniform due to voltage drop through transparent conductive coatings
Solution Approach 1:
The patent segments the electrochromic device into multiple independently controllable segments or zones. By applying voltage to different segments separately, the system overcomes the voltage drop issue in large-area devices, enabling uniform and fast transmissivity change across the entire device without the iris effect.
Solution Approach 2:
The patent implements local quality control by allowing different voltage levels to be applied to different regions of the electrochromic device simultaneously. This enables each region to be optimized for its specific characteristics, achieving uniform transmissivity change across the device while maintaining fast response speed.
2Adaptability or versatility
If repeated cycling is performed to achieve desired transmissivity range, then the device can adapt to different conditions, but faradaic losses accumulate causing drift in cell potential and degradation of performance
Solution Approach 1:
The patent implements feedback control by continuously monitoring the cell potential of the electrochromic device and adjusting the applied voltage accordingly. This feedback mechanism compensates for faradaic losses and prevents drift in cell potential, maintaining reliable performance over repeated cycling while preserving the full transmissivity range.
Solution Approach 2:
The patent dynamically changes operating parameters (voltage, current, timing) based on the device's state and cycling history. By adjusting these parameters in response to accumulated faradaic losses, the system maintains cell potential stability and prevents degradation while preserving adaptability across different transmissivity requirements.
3Speed
If higher voltage is applied to speed up transmissivity change, then the switching speed improves, but the voltage drop through conductive coatings increases causing non-uniform coloring
Solution Approach 1:
The patent divides the device into segments that can be charged independently at optimized voltage levels. This allows each segment to achieve fast switching without excessive voltage drop, maintaining uniform coloring across the entire device while preserving high switching speed.
Solution Approach 2:
The patent applies different voltage levels to different regions of the device based on their specific characteristics and requirements. This local optimization enables each region to switch quickly while maintaining uniform transmissivity change, resolving the contradiction between speed and uniformity.
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 driver system achieves reliable and repeated charging and discharging of electrochromic devices, maintaining charge neutrality and preventing degradation, thus enhancing the robustness and uniformity of transmissivity changes.
Implementation Method 1
An electrochromic glass unit uses electrochromic glass that can change transmissivity with the application of electric current and voltage. The change of transmissivity typically relies on a reversible oxidation of a material.
Implementation Method 2
The change of transmissivity typically relies on a reversible oxidation of a material.
Implementation Method 3
A driver for an electrochromic device can include a power supply and a power supply control module configured to supply a constant current from the power supply to the electrochromic device
Implementation Method 4
Faradaic losses in reversible electrochromic devices can degrade the performance of reversible electrochromic devices. These faradaic losses can, in turn, result in a corresponding change in the oxidation state of an electrochromic material in the electrochromic device.
Data Source
AI summary
A method for controlling an electrochromic device is provided. The method includes applying a constant supply current to the electrochromic device and determining an amount of charge transferred to the electrochromic device, as a function of time and current supplied to the electrochromic device. The method includes ceasing the applying the constant supply current, responsive to a sense voltage reaching a sense voltage limit and applying one of a variable voltage or a variable current to the electrochromic device to maintain the sense voltage at the sense voltage limit, responsive to the sense voltage reaching the sense voltage limit. The method includes terminating the applying the variable voltage or the variable current to the electrochromic device, responsive to the determined amount of charge reaching a target amount of charge.