Electrochromic Window PWM Control for Precise Voltage Transitions
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Solution Overview
Problem
Existing technologies face challenges in efficiently integrating and controlling optically-switchable devices like electrochromic windows, particularly in terms of organizing, powering, and managing their transitions to optimize energy efficiency and aesthetic purposes.
Innovation Solution
A window controller that generates pulse-width-modulated signals to drive optically-switchable devices, utilizing a command-voltage generator and pulse-width-modulated-signal generator to adjust duty cycles and voltages across conductive electrode layers, integrated with a network controller for centralized control and feedback-based adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional voltage control methods are used for electrochromic windows, then the control system is simple, but energy efficiency is poor and transition control is imprecise
Solution Approach 1:
The patent applies pulse-width modulation (PWM) to convert a simple DC voltage source into a time-varying control signal. The controller generates periodic pulses with adjustable duty cycles to drive the electrochromic window, enabling precise control over the coloring and bleaching transitions. This periodic action allows efficient energy usage by applying voltage only when needed for state transitions, rather than maintaining continuous voltage.
Solution Approach 2:
The controller dynamically adjusts the duty cycle of PWM signals based on the desired optical state and transition requirements. By varying the pulse width dynamically, the system can precisely control the rate and extent of electrochromic transitions, enabling both fast switching and gradual transitions as needed. This dynamic control improves energy efficiency by matching power delivery to actual device needs.
2Speed
If high voltage is applied to achieve fast transitions, then transition speed increases, but energy consumption increases
Solution Approach 1:
The PWM controller applies high voltage in short periodic pulses rather than continuously. During each pulse, high voltage drives fast ion transport for rapid transitions. Between pulses, the voltage is reduced or eliminated, allowing the electrochromic material to maintain its state without continuous energy input. This periodic high-voltage application achieves fast transitions while minimizing overall energy consumption.
Solution Approach 2:
The controller maintains the electrochromic window in its desired state by applying low-duty-cycle PWM signals that provide just enough voltage to counteract leakage currents and maintain the colored or bleached state. This continuous low-level control ensures the window remains in the desired state without requiring continuous high voltage, thus maintaining transition readiness while minimizing energy consumption.
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 control of electrochromic windows, optimizing energy usage and aesthetic properties by adjusting voltage and duty cycles, and integrating with building management systems for holistic energy management.
Implementation Method 1
Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in one or more optical properties when stimulated to a different electronic state. For example, the electrochromic material can be stimulated by an applied voltage.
Implementation Method 2
a pulse-width-modulated-signal generator configured to generate a pulse-width-modulated signal based on the command voltage signal. The pulse-width-modulated signal is configured to drive an optically-switchable device
Implementation Method 3
Tungsten oxide is a cathodic electrochromic material that undergoes a coloration transition—transparent to blue—by electrochemical action via intercalation of positive ions into the tungsten oxide matrix with concurrent charge balance by electron insertion.
Data Source
AI summary
This disclosure provides a window controller that includes a command-voltage generator that generates a command voltage signal, and a pulse-width-modulated-signal generator that generates a pulse-width-modulated signal based on the command voltage signal. The pulse-width-modulated signal drives an optically-switchable device. The pulse-width-modulated signal comprises a first power component having a first duty cycle and a second power component having a second duty cycle. The first component delivers a first pulse during each active portion of the first duty cycle, and the second component delivers a second pulse during each active portion of the second duty cycle. The first pulses are applied to a first conductive layer and the second pulses are applied to a second conductive layer. The relative durations of the active portions and the relative durations of the first and second pulses are adjusted to result in a change in an effective DC voltage applied across the optically-switchable device.