Switch Mode RF Generator for Wireless Charging
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Solution Overview
Problem
Existing wireless charging systems face challenges in maintaining constant current behavior over varying load impedance conditions, leading to inefficiencies and increased costs due to the reliance on slow and complex feedback systems in power amplifiers.
Innovation Solution
A switch mode power amplifier with a synthesized output network that automatically adjusts to provide constant RF current without feedback, using a combination of impedance transformation and filtering to align with the highest gradient path of the constant power contour, thereby simplifying system design and improving performance over a large load impedance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback system is used to maintain constant current behavior in power amplifiers, then current stability is improved, but system complexity and response time are worsened
Solution Approach 1:
The patent extracts and eliminates the feedback control system from the power amplifier design. By using a Class E switch mode PA topology with carefully selected output network components (inductors and capacitors), the system achieves constant current behavior inherently without requiring feedback loops, sensors, or control circuitry.
Solution Approach 2:
The power amplifier circuit is designed to self-regulate its output current through its inherent electrical characteristics. The Class E topology with specific L and C values creates a circuit that naturally maintains constant current over varying load conditions without external control or monitoring mechanisms.
2Reliability
If a feedback system is used to maintain constant current behavior in power amplifiers, then current stability is improved, but response speed is worsened
Solution Approach 1:
The feedback loop is completely removed from the system. The Class E power amplifier with its specific output network design provides instantaneous constant current behavior that responds immediately to load changes without the delay inherent in feedback measurement, processing, and correction cycles.
3Reliability
If conventional Class D switch mode PA topology with variable supply voltage is used, then constant current behavior is achieved, but manufacturing complexity and cost are increased
Solution Approach 1:
The patent removes the variable supply voltage control mechanism and feedback system from the Class D topology. Instead, it adopts a fixed voltage Class E topology with a passive output network consisting of fixed inductors and capacitors, dramatically simplifying the manufacturing process and reducing component count while maintaining constant current performance.
4Reliability
If feedback control is implemented to handle extreme load conditions, then current stability is improved, but system cost is increased
Solution Approach 1:
The power amplifier circuit inherently handles extreme load conditions through its Class E topology and output network design. The circuit automatically adapts to varying load impedances without requiring expensive feedback control hardware, sensors, or microcontroller-based control systems.
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 superior constant current behavior, reduces costs, and enhances functionality across a wide range of load impedance variations, ensuring compliance with regulatory standards for wireless power transfer systems.
Implementation Method 1
a transmitter (Tx) coil configured to generate a magnetic field
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A device for wirelessly charging a battery includes a power amplifier (116) having a transmitter coil generating a magnetic field for wirelessly charging a battery. A low pass filter arrangement (204) is electrically coupled to an output of the power amplifier. A band stop filter is electrically coupled to an output of the low pass filter arrangement. An output of the band stop filter is electrically coupled to a resistive load associated with the battery. The low pass filter arrangement and the band stop filter are configured to transform a load impedance associated with the transmitter coil to produce a current at the output of the power amplifier that remains substantially constant in response to changes in the load impedance.