Capacitive Isolation Circuit for Leakage Current Suppression
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Solution Overview
Problem
Conventional isolation transformers face challenges in enhancing electric isolation between the primary and secondary sides due to parasitic capacitance, leading to leakage currents and limitations in size reduction and power transmission efficiency.
Innovation Solution
The method involves an isolation transmission circuit with capacitors, rectifier, and inverter circuits, along with a common mode suppressing circuit and power factor correction, to suppress leakage currents and improve power transmission efficiency by using capacitive elements and resonance inductors to enhance isolation and adjust output voltages/currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation transformer is used to implement electric isolation, then electric isolation between primary and secondary sides is achieved, but parasitic capacitance causes leakage current and limits size reduction
Solution Approach 1:
The patent changes the operating frequency parameter from conventional 50/60 Hz to high frequency (e.g., 20 kHz or higher). This frequency transformation reduces the reactance of parasitic capacitance (Xc = 1/(2πfC)), thereby reducing leakage current while maintaining isolation. The high-frequency operation enables thinner isolation barriers while controlling leakage within safety limits.
Solution Approach 2:
The patent employs dynamic frequency adjustment and adaptive control mechanisms. The system can dynamically adjust the operating frequency based on load conditions and isolation requirements, optimizing the balance between leakage current suppression and power transmission efficiency. This dynamic adaptation allows the isolation barrier thickness to be optimized for each operating condition.
2Reliability
If double insulation scheme is applied to enhance electric isolation, then leakage current is suppressed, but device size cannot be reduced
Solution Approach 1:
By transforming to high-frequency operation, the patent reduces the required insulation thickness. At high frequencies, the reactance of parasitic capacitance is sufficiently low that thinner isolation barriers can maintain acceptable leakage current levels. This eliminates the need for bulky double insulation structures while achieving equivalent or superior isolation performance.
Solution Approach 2:
The patent replaces mechanical/physical insulation structures (thick barriers, double insulation layers) with an electrical solution based on high-frequency operation and active control. Instead of relying on physical distance and material thickness for isolation, the system uses frequency-domain separation and dynamic compensation to achieve isolation with minimal physical barrier thickness.
3Reliability
If conventional isolation transformer is used, then electric isolation is provided, but copper and iron losses reduce power transmission efficiency
Solution Approach 1:
The patent changes the operating frequency to high frequency, which reduces the required transformer size and associated copper losses (I²R losses). The high-frequency operation enables smaller winding cross-sections and reduced core volume, directly reducing both copper and iron losses. Additionally, the reduced leakage current at high frequency improves overall power transmission efficiency.
4Reliability
If isolation transformer with parasitic capacitance is used, then isolation is provided, but leakage current increases and safety is compromised
Solution Approach 1:
The patent transforms the operating frequency to high frequency, which fundamentally changes the behavior of parasitic capacitance. While the capacitance value remains the same, its reactance (Xc = 1/(2πfC)) is dramatically reduced at high frequencies, allowing the parasitic capacitance to pass less current for the same voltage stress. This parameter transformation maintains isolation while suppressing leakage current to safe levels.
Solution Approach 2:
The patent converts the harmful effect of parasitic capacitance into a beneficial one. By operating at high frequency, the system exploits the frequency-dependent behavior of capacitance to reduce its harmful leakage effect. The same parasitic capacitance that would be problematic at 50/60 Hz becomes advantageous at high frequencies, enabling thinner isolation barriers with controlled leakage.
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 effectively reduces leakage currents, enhances electric isolation, and increases power transmission efficiency, enabling the development of lighter, more efficient electric products with improved safety and performance.
Implementation Method 1
providing an isolation transmission circuit having at least one capacitor; providing electric isolation between a first side and a second side of the isolation transmission circuit
Implementation Method 2
connecting a capacitor of the isolation transmission circuit to a resonance inductor in series to increase power transmission efficiency
Data Source
AI summary
A method and apparatus used for electric isolation transmission are provided. The method includes: providing an isolation transmission circuit having at least one capacitor; and implementing electric isolation between the primary side and secondary side, and suppressing leakage currents generated between the primary side and secondary side and transmitting power. The apparatus includes the isolation transmission circuit that is manufactured by capacitor(s). The apparatus can be applied to light-weight power sources providing AC/DC outputs with high efficiency, adapters, or related products. In addition, the apparatus has a reduced size and higher power transmission efficiency.