Capacitive Isolation Circuit With Frequency Raising for DC Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic transformers used for electrical insulation between AC and DC voltage sources in electric or hybrid vehicles are bulky, heavy, and costly, making them difficult to integrate into electrical circuits.
Innovation Solution
An electrical circuit using a capacitive transformer with a frequency-raising stage comprising controllable electronic switches to increase the frequency of AC current flowing through capacitors, reducing their size and cost, and eliminating the need for a magnetic core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic transformer is used for electrical insulation between AC and DC voltage sources, then electrical insulation is achieved, but the device becomes bulky, heavy, and costly
Solution Approach 1:
The patent replaces the magnetic transformer (mechanical/electromagnetic system with magnetic core) with an electronic insulation system using capacitors and electronic switches. This substitution eliminates the need for bulky magnetic cores while achieving the same electrical insulation function through electronic switching and capacitive coupling.
Solution Approach 2:
The patent changes the operating frequency parameter by using a frequency-raising stage that converts low-frequency AC (e.g., 50/60 Hz) to high-frequency AC. This frequency transformation allows the use of smaller capacitors that can achieve the required insulation capacitance with reduced physical size, thereby reducing overall device weight.
2Reliability
If a magnetic transformer is used for electrical insulation, then insulation is provided, but the device complexity and cost increase
Solution Approach 1:
The patent divides the insulation function into separate modular components: capacitors for insulation, electronic switches for frequency conversion, and control circuitry. This segmentation allows each component to be optimized independently and facilitates easier integration into the overall circuit design compared to a monolithic magnetic transformer.
Solution Approach 2:
The electronic insulation system performs multiple functions: electrical insulation, frequency conversion, and voltage regulation. By combining these functions into a single integrated circuit architecture, the patent reduces overall device complexity compared to using separate components for each function.
3Reliability
If capacitors are used in a capacitive transformer with network-frequency AC current, then insulation is achieved, but the capacitors become large and expensive
Solution Approach 1:
The patent applies frequency transformation to convert low-frequency AC current to high-frequency AC current before it passes through the capacitors in the capacitive transformer. Since capacitor size is inversely proportional to operating frequency, this parameter change dramatically reduces the physical size and cost of the required capacitors while maintaining the same insulation performance.
4Speed
If a frequency-raising stage with rectifier and inverter is used, then frequency conversion is achieved, but the cost and complexity increase
Solution Approach 1:
The patent extracts and eliminates the rectifier stage from the traditional frequency conversion system. By using a direct frequency-raising approach with electronic switches that operate directly on the AC input, the system achieves frequency conversion without the intermediate DC link required by rectifier-inverter architectures, thereby reducing component count and simplifying the overall circuit.
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 capacitive transformer is smaller and less costly, allowing for efficient insulation and reducing the complexity and cost of the frequency-raising stage, while improving its efficiency and enabling integration into compact electrical circuits.
Implementation Method 1
a capacitive transformer formed using a plurality of capacitors, which is arranged so as to electrically insulate the input from the first output of the circuit
Implementation Method 2
a frequency-raising stage arranged between the input of the circuit and the capacitive transformer so that the capacitors of the capacitive transformer are in a circuit portion that has flowing through it an AC current at a frequency that is greater than that of the AC network, the frequency-raising stage comprising a first branch comprising two controllable electronic switches arranged in series
Data Source
AI summary
An electrical circuit for charging a DC voltage source from an AC voltage network. The circuit includes an input that is able to receive an AC voltage from the voltage network, and a first output able to be connected to the DC voltage source. An insulating stage formed using a plurality of capacitors is arranged so as to electrically insulate the input from the first output of the circuit. A frequency-raising stage is arranged between the input of the circuit and the insulating stage so that the capacitors of the insulating stage are in a circuit portion that has flowing through it an AC current at a frequency that is greater than that of the AC network.