Variable Capacitance Device for Wireless Energy Transfer
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Solution Overview
Problem
Existing tunable circuit components face limitations in dynamic range, precision, and power losses, particularly in high power applications like wireless power transfer systems, where impedance matching is challenging due to large voltage swings and varying load impedances.
Innovation Solution
A dynamically tunable circuit element comprising a variable capacitance device with capacitors and switches, controlled by a circuitry that adjusts capacitance based on zero voltage conditions, using control signals to optimize capacitance and reduce power losses, allowing for precise impedance matching across a wide range of values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing tunable circuit components are used in high power wireless power transfer systems, then impedance matching can be achieved, but the components suffer from limited dynamic range, imprecise tuning capabilities, and high power losses
Solution Approach 1:
The patent divides the single tunable capacitor into multiple discrete capacitor segments (first capacitor, second capacitor, third capacitor) that can be independently switched. This segmentation allows for finer control over the total capacitance value, improving tuning precision while distributing power losses across multiple smaller components rather than a single component operating at its limits.
Solution Approach 2:
The patent implements dynamic switching of capacitor segments based on real-time detection of voltage conditions and power transfer parameters. The controller dynamically adjusts which capacitor segments are connected to the circuit, enabling adaptive impedance matching that responds to changing load conditions, thereby optimizing both tuning precision and power efficiency under varying operating conditions.
2Adaptability or versatility
If existing tunable circuit components are used, then some impedance matching is possible, but the dynamic range of adjustable values is limited
Solution Approach 1:
By segmenting the capacitance into multiple discrete units (first capacitor with first value, second capacitor with second value, third capacitor with third value), the system achieves a wider effective dynamic range through combinatorial switching. Different combinations of segments provide finely spaced adjustable values across an extended range, simultaneously improving both dynamic range and tuning precision.
Solution Approach 2:
The patent changes the effective capacitance parameter by selectively connecting different capacitor segments in series or parallel configurations through the switching circuit. This allows the total capacitance to be dynamically adjusted across a wide range of values with fine resolution, expanding the dynamic range while maintaining precise control over the impedance matching parameter.
3Device complexity
If conventional switching control is used without zero voltage detection, then circuit operation is simpler, but voltage and current stresses on components increase
Solution Approach 1:
The patent incorporates feedback by detecting the voltage conditions across capacitor segments and using this information to control the switching timing. The controller monitors the actual voltage state and adjusts the switching signals accordingly, creating a closed-loop control system that ensures switches operate at optimal moments (zero voltage crossing), thereby reducing voltage and current stresses on components while maintaining manageable circuit complexity.
Solution Approach 2:
The system performs preliminary detection of voltage conditions before executing the switching action. By detecting when the voltage across a capacitor segment reaches zero before triggering the switch, the system prepares and times the switching event to occur at the optimal moment, preventing high voltage or current stress conditions that would occur with conventional non-synchronized switching.
4Power
If impedance matching is performed with large voltage swings, then power transfer capability is maintained, but existing tunable components become unusable
Solution Approach 1:
The patent segments the high voltage capacitor into multiple lower-voltage capacitor units that can be switched in series or parallel configurations. This allows the system to handle high power transfer requirements (large voltage swings) by distributing the voltage stress across multiple components rather than requiring a single high-voltage component, thereby improving reliability and component usability in high power applications.
Solution Approach 2:
The patent dynamically reconfigures the capacitor segment connections based on the operating conditions and voltage levels. During high power transfer with large voltage swings, the controller can switch between different capacitor segment combinations to maintain appropriate voltage distribution across components, preventing any single component from experiencing excessive stress and thus maintaining reliability under varying power conditions.
Data Source
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AI summary
A variable capacitance device. The device includes a first capacitor, a first switch, a second capacitor, a second switch, and control circuitry. The control circuitry is configured to adjust respective capacitances of the first and second capacitors by causing a first control signal to be applied to the first-switch control terminal for a duration of time in response to detecting a zero voltage condition across the first switch, and by causing a second control signal to be applied to the second-switch control terminal for the duration of time in response to detecting a zero voltage condition across the second switch.