Wireless Power Transmitter Circuit Impedance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless power transmitter circuits face high power loss due to impedance mismatch when the relative position between the rechargeable device and the resonant transmitter circuit changes, requiring high input voltage and power to maintain constant current or power control.
Innovation Solution
A wireless power transmitter circuit with a power converter, inverter, LC circuit, and control circuit that adjusts the impedance of a variable capacitor to maintain impedance matching, using a capacitance adjustment signal to control the coil current and output power, thereby reducing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the relative position between the rechargeable device and the resonant transmitter circuit changes, then the reflection impedance changes, but the power loss increases due to impedance mismatch
Solution Approach 1:
The patent applies a variable capacitor circuit that can dynamically adjust its capacitance value in response to changes in the reflection impedance. The control circuit monitors the impedance conditions and modifies the capacitance accordingly, transforming a static circuit into a dynamic one that adapts to varying positions of the rechargeable device, thereby maintaining impedance matching and reducing power loss.
Solution Approach 2:
The patent changes the electrical parameter (capacitance) of the variable capacitor circuit to compensate for impedance variations. By adjusting the capacitance value, the circuit modifies its reactive component to counteract changes in the reflection impedance, maintaining optimal power transfer conditions despite position changes of the rechargeable device.
2Measurement precision
If high input voltage and power are used to maintain constant current or power control, then the control precision improves, but the power loss increases
Solution Approach 1:
The patent implements a control circuit that continuously monitors the operating conditions (current, power, impedance) and provides feedback to adjust the variable capacitor circuit. This closed-loop feedback mechanism enables precise constant current or power control by making real-time adjustments to the capacitance, achieving accurate control without requiring excessive input voltage or power that would cause additional losses.
3Speed
If the reactance of the LC circuit is increased to improve resonance, then the resonant frequency improves, but the impedance mismatch becomes more serious
Solution Approach 1:
The patent creates a composite resonant circuit by combining the fixed LC circuit with a variable capacitor circuit. This composite structure allows the system to benefit from the resonant frequency characteristics of the LC circuit while adding the adaptability of the variable capacitor to compensate for impedance variations, achieving both good resonance performance and impedance matching across different operating conditions.
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 solution enables efficient wireless power transmission by maintaining constant current and power control without additional power loss, optimizing power conversion efficiency by ensuring impedance matching.
Implementation Method 1
an LC circuit, which includes an inductor and a capacitor, and is coupled to the power inverter circuit, wherein an reactance of the LC circuit is substantially zero, and the LC circuit is configured to operably convert the AC output current to a coil current
Implementation Method 2
a resonant transmitter circuit, which includes at least one transmitter coil and a variable capacitor circuit, wherein the coil current flows through the at least one transmitter coil to generate a resonant wireless power
Data Source
AI summary
A wireless power transmitter circuit includes a power converter circuit, a power inverter circuit, an LC circuit, a resonant transmitter circuit, and a control circuit. The LC circuit includes an inductor and a capacitor, wherein an reactance of the LC circuit is substantially zero. The LC circuit is for converting the AC output current to a coil current. The resonant transmitter circuit includes at least one transmitter coil and a variable capacitor circuit, wherein the coil current flows through the at least one transmitter coil to generate a resonant wireless power. The control circuit generates a capacitance adjustment signal for adjusting an impedance of the variable capacitor circuit, such that the resonant transmitter circuit substantially operates in an impedance matched condition.