RF Energy Feed Tuning Circuit for Leakage Current Cancellation
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Solution Overview
Problem
Existing energy conveying devices for radiofrequency (RF) and microwave electromagnetic energy suffer from leakage currents due to stray capacitance, which violates safety standards like BS EN 60601-2-2:2009.
Innovation Solution
The integration of a series-connected inductor and capacitor between one line of the RF/microwave bipolar feed and ground/neutral, forming a resonant circuit aligned with the frequency of the conveyed energy, effectively reduces leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation transformer is used to isolate the bipolar feed from ground and neutral, then electrical isolation is improved, but leakage capacitance increases
Solution Approach 1:
A tuning circuit comprising an inductor and capacitor connected in series is introduced as an intermediary element between the bipolar feed line and ground/neutral. This tuning circuit acts as a mediator that transforms the harmful leakage capacitance into a beneficial resonant circuit, where the inductor and capacitor work together to cancel out the unwanted capacitive coupling at the operating frequency.
Solution Approach 2:
The invention converts the harmful leakage capacitance introduced by the isolation transformer into a beneficial effect by creating a resonant circuit. The tuning circuit is designed so that its resonant frequency matches the operating frequency, causing the leakage capacitance to be cancelled out through resonance, thereby transforming a harmful factor into a solution.
2Object-affected harmful factors
If the leakage capacitance is reduced to meet safety standards, then patient safety is improved, but device complexity increases
Solution Approach 1:
The invention changes the electrical parameters of the system by introducing a tuning circuit with specific inductance and capacitance values. These parameters are carefully selected to create a resonant circuit whose frequency matches the operating frequency, thereby changing the overall impedance characteristics and canceling leakage current without requiring complete redesign of the isolation transformer.
3Object-affected harmful factors
If a series-connected inductor and capacitor are added to form a resonant circuit, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The tuning circuit with the series-connected inductor and capacitor serves multiple functions simultaneously: it acts as a resonant circuit to cancel leakage capacitance, provides impedance matching, and maintains electrical isolation. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving leakage current reduction.
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 configuration significantly reduces or cancels leakage currents, ensuring compliance with safety standards by minimizing power leakage through the 200Ω test resistor.
Implementation Method 1
The inductor unit has a tuning inductance such that the tuning circuit and the first leakage capacitance form a resonant circuit having a resonance frequency that is aligned with the first frequency
Data Source
AI summary
An energy conveying device for conveying radiofrequency electromagnetic energy or microwave electromagnetic energy. The device comprises: a first conductive line and a second conductive line configured to convey radiofrequency electromagnetic energy or microwave electromagnetic energy having a first frequency. Also, the device comprises: an electrical element providing a first leakage capacitance. The first leakage capacitance is between the first conductive line and a ground or between the second conductive line and the ground. Further, the device comprises: a tuning circuit including an inductor unit and a capacitor unit having a ground capacitance. The inductor unit and the capacitor unit are connected in series between the ground and either the first conductive line or the second conductive line. The inductor unit has a tuning inductance such that the tuning circuit and the first leakage capacitance form a resonant circuit having a resonance frequency that is aligned with the first frequency.