Capacitive Insulation for Vehicle Electrical Systems
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Solution Overview
Problem
The high cost of galvanic isolation in electrical systems for motor vehicles, particularly in high voltage applications like 48V systems, which is necessary to maintain a leakage current of less than 1 µA between low voltage (12V) and high voltage (48V) circuits, is a significant challenge.
Innovation Solution
An electrical system that uses capacitive insulation instead of galvanic insulation, comprising a capacitive element connecting points of different potential between two electrical circuits powered by different voltages, along with a temperature measurement device that includes a voltage generator, acquisition device, and calculation unit to estimate temperature, and optionally a filtering device to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation is used to maintain leakage current below 1 µA between low voltage and high voltage circuits, then the required electrical safety standard is met, but production costs increase significantly
Solution Approach 1:
The patent replaces galvanic isolation (a physical/electrical isolation mechanism) with a capacitive coupling mechanism. The capacitive element provides the necessary electrical separation between low voltage and high voltage circuits while allowing signal transmission, thereby reducing costs associated with traditional galvanic isolation components.
Solution Approach 2:
The patent changes the electrical parameters by using a capacitive element with specific capacitance value (typically 1-100 nF) to control the leakage current. By carefully selecting the capacitance value and operating frequency, the system achieves the required <1 µA leakage current while eliminating the need for expensive galvanic isolation hardware.
2Ease of manufacture
If capacitive insulation is used instead of galvanic insulation, then production costs are reduced, but ensuring adequate insulation between circuits becomes more challenging
Solution Approach 1:
The capacitive element acts as an intermediary component between low voltage and high voltage circuits. It provides the necessary electrical separation while allowing controlled signal transmission, serving as a cost-effective alternative to galvanic isolation that maintains insulation effectiveness through its capacitive coupling mechanism.
Solution Approach 2:
The patent employs dynamic control through the capacitive coupling, where the insulation effectiveness is maintained through the frequency-dependent characteristics of the capacitor. The system dynamically responds to different signal frequencies, providing adequate insulation at operating frequencies while allowing signal transmission, thus ensuring reliability without galvanic isolation.
3Temperature
If temperature measurement is implemented in the electrical system, then thermal monitoring capability is improved, but system complexity and component count increase
Solution Approach 1:
The capacitive element serves multiple functions: it provides insulation between circuits, enables signal transmission, and acts as part of the temperature sensing mechanism. By using the existing capacitive coupling structure for temperature measurement purposes, the patent avoids adding separate temperature sensing components, thereby maintaining system simplicity while achieving thermal monitoring capability.
Solution Approach 2:
The patent merges the temperature measurement function with the existing capacitive insulation structure. The capacitive element's properties are utilized for both electrical isolation and temperature sensing, combining multiple functions into a single component to reduce overall system complexity and component count.
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 reduces production costs by eliminating the need for expensive galvanic insulation while maintaining the required leakage current levels and enabling accurate temperature measurement within the electrical system.
Implementation Method 1
a capacitive element connecting a point of first potential of the first electrical circuit to a point of second potential of the second electrical circuit
Data Source
Figure 1~2
Figure 3~4b
Figure 5
AI summary
The invention relates to an electrical system (10) particularly for a motor vehicle, comprising: a first electrical circuit (12) having a first ground (GND1) and powered by a first voltage (V1) at a first power supply terminal (B1), a second electrical circuit (14) having a second ground (GND2) separate from the first ground (GND1) and powered by a second voltage (V2) different from the first voltage (V1) at a second power supply terminal (B2), and a capacitive element (20) connecting a first potential point (A) of the first electrical circuit (12) to a second potential point (B) of the second electrical circuit (14).