Electrochromic Device Voltage Ramp Control
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Solution Overview
Problem
Conventional methods for driving electrochromic devices are inadequate for large sizes, as they either slow down switching speed or lead to premature device degradation, due to issues with ion movement, electrical potential, and sheet resistance of transparent conductor layers.
Innovation Solution
A method involving a ramp function to apply voltage to bus bars of electrochromic devices, followed by reducing voltage and current delivery, with a profile shaped according to the reduced magnitude voltage, to achieve efficient and safe transitions between optical states without damaging the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional driving profiles are used with sufficiently low voltages to avoid device damage, then device reliability is maintained, but switching speed becomes slow
Solution Approach 1:
The patent applies dynamic voltage control by transitioning from a constant low voltage to a ramped voltage profile. The controller dynamically adjusts the voltage applied to the electrochromic device, starting at a lower voltage to avoid immediate damage, then progressively increasing to a higher voltage to accelerate ion movement and switching speed, thereby resolving the contradiction between reliability and switching speed.
Solution Approach 2:
The patent changes the voltage parameter over time using a ramp function. The voltage transitions from an initial safe level to a higher operational level, allowing the system to exploit higher voltages for faster switching while maintaining device integrity through controlled progression. This parameter change strategy enables both fast switching and device protection.
2Speed
If higher voltages are applied to increase switching speed, then switching speed improves, but device degradation occurs prematurely
Solution Approach 1:
The patent applies a preliminary action by first establishing a safe voltage level before increasing to higher voltages. The ramp function ensures that high voltage is not applied abruptly but is progressively introduced after the device has had time to adapt and the initial ion movement has been established safely. This preliminary low-voltage phase protects the device while still achieving fast switching.
Solution Approach 2:
The patent provides beforehand cushioning by using a ramped voltage profile that gradually increases the voltage stress on the device. This gradual progression acts as a cushion, preventing sudden high-voltage shocks that would cause immediate degradation. The ramp function smooths the transition, allowing the device to withstand higher voltages without premature failure.
3Area of stationary object
If voltage is applied across large electrochromic devices, then the entire surface can be driven, but voltage distribution becomes non-uniform due to sheet resistance
Solution Approach 1:
The patent applies local quality by recognizing that different regions of the large electrochromic device require different voltage levels due to sheet resistance effects. The ramp function allows the controller to account for spatial variations in voltage distribution, effectively applying tailored voltage profiles to different regions of the device to achieve uniform performance across the entire large surface area.
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 enables faster switching speeds and extended device lifespan by maintaining effective voltage within a safe range across the entire surface of large electrochromic devices, improving performance without risking degradation.
Implementation Method 1
at least one electrochromic material, that changes its optical properties, such as visible light transmitted through the layer, in response to the application of an electrical potential
Implementation Method 2
an ion conductor (IC), which allows ions (e.g. Li+) to move through it, into and out from the electrochromic material to cause the optical property change
Data Source
AI summary
Controllers and control methods apply a drive voltage to bus bars of a thin film optically switchable device. The applied drive voltage is provided at a level that drives a transition over the entire surface of the optically switchable device but does not damage or degrade the device. This applied voltage produces an effective voltage at all locations on the face of the device that is within a bracketed range. The upper bound of this range is associated with a voltage safely below the level at which the device may experience damage or degradation impacting its performance in the short term or the long term. At the lower boundary of this range is an effective voltage at which the transition between optical states of the device occurs relatively rapidly. The level of voltage applied between the bus bars is significantly greater than the maximum value of the effective voltage within the bracketed range.