Galvanic Isolation in Electrochromic Glass Control via Low-Voltage Transformer
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Solution Overview
Problem
Existing methods for controlling electro-optical objects like electrochromically tinted glass panes in vehicles face a risk of user injury and malfunctions due to galvanic coupling of high-voltage potentials with the vehicle's electrical system, primarily caused by the use of DC/AC boost converters.
Innovation Solution
The use of a low-voltage transformer, controlled by a microcontroller, eliminates the need for a DC/AC boost converter, ensuring galvanic isolation and allowing for individual adjustment of transmittance through a sine-weighted pulse width modulation switching pattern, with a MOSFET bridge circuit for signal conversion and filtering of high-frequency interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC/AC boost converter is used to convert low AC voltage to operating voltage, then the required operating voltage (approx. 160V at 50Hz) can be generated, but galvanic coupling occurs between the control voltage and the vehicle's electrical system, leading to safety risks and potential malfunctions
Solution Approach 1:
The patent introduces a galvanically isolated voltage converter that acts as an intermediary between the low-voltage control system and the high-voltage electro-optical object. This converter transforms the control voltage into the required operating voltage while maintaining galvanic isolation, thus eliminating the harmful galvanic coupling effect. The converter includes a primary winding connected to the control voltage and a secondary winding connected to the electro-optical object, with the transformation achieved through electromagnetic induction rather than direct galvanic connection.
Solution Approach 2:
The patent replaces the conventional DC/AC boost converter (which creates galvanic coupling) with an alternative voltage conversion system based on electromagnetic induction. This substitution eliminates the direct electrical connection while maintaining the voltage transformation function, thereby resolving the contradiction between achieving required operating voltage and avoiding galvanic coupling.
2Object-affected harmful factors
If a low-voltage transformer with galvanic isolation is used, then safety is improved by eliminating galvanic coupling, but additional conversion stages and components are required
Solution Approach 1:
The patent combines multiple functions into a single galvanically isolated voltage converter: voltage transformation, galvanic isolation, and frequency conversion. By merging these functions into one integrated component rather than using separate stages, the system achieves safety through galvanic isolation while minimizing the overall complexity of the conversion system.
Solution Approach 2:
The galvanically isolated voltage converter is designed to perform multiple functions simultaneously: it transforms voltage levels, provides galvanic isolation for safety, and can adapt to different operating conditions. This multi-functionality reduces the need for additional specialized components, thereby managing device complexity while achieving safety goals.
3Ease of operation
If individual control of each glass pane is implemented using a microcontroller, then precise adjustment of transmittance is achieved, but the control system becomes more complex
Solution Approach 1:
The patent uses a microcontroller to digitally control the voltage applied to each electro-optical object, enabling precise adjustment of transmittance by changing voltage parameters. The microcontroller can independently adjust the magnitude and timing of voltage pulses for each glass pane, providing individual control while managing complexity through software-based parameter management rather than additional hardware for each pane.
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 solution provides safe, cost-effective control of electro-optical objects by isolating control voltage from on-board voltage, reducing the risk of injury and malfunctions, while enabling precise adjustment of transmittance and monitoring for fault conditions.
Implementation Method 1
a low-voltage transformer being integrated into the circuit, by means of which the electro-optical object can be controlled
Implementation Method 2
an electrochromically tinted glass pane in a motor vehicle, the transmittance of the electro-optical object being changed by applying an electrical AC voltage
Data Source
Figure 1
AI summary
The invention relates to a method for controlling an electro-optical object, in particular an electrochromically tinted glass pane in a motor vehicle, wherein the transmittance of the electro-optical object is changed by applying a voltage. In order to develop a method of the type mentioned at the beginning in such a way that galvanic isolation of the control voltage and the vehicle electrical system voltage in a motor vehicle is ensured, the control of the electro-optical object according to the invention is performed by means of a low-voltage transformer (10) and the low-voltage transformer (10) is controlled by a digital signal, which is produced by a microcontroller (2).