Regulated Load Modulation Circuit for Wireless Charging
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Solution Overview
Problem
Magnetic resonance wireless charging systems face challenges in accurately detecting a valid power receiving unit during the initialization phase due to variations in load impedance caused by objects with conductive metal or non-valid coils, leading to non-compliance with target power ranges during load modulation signaling.
Innovation Solution
A load modulation circuit with a controllable current source and sensor circuit that dynamically adjusts the duty cycle of a switch based on rectified voltage to maintain the change in total conducting power within a predetermined target range, using multiple branches with different resistances and a pulse width modulation circuit to ensure compliance with specifications like A4WP's 0.5 W<ΔP<1.1 W.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a PTU uses a short beacon period for rapid detection, then detection speed is improved, but detection accuracy deteriorates due to insufficient time to distinguish valid PRUs from false objects
Solution Approach 1:
The system employs periodic beacon periods with alternating durations (short and long beacons) to systematically probe for PRUs. The short beacon enables rapid initial detection, while the long beacon provides extended measurement time for accurate validation, resolving the contradiction between speed and precision through time-division periodic action.
Solution Approach 2:
The beacon period duration is dynamically adjusted based on detection needs. The system transitions from short beacons during initial scanning to long beacons during validation phases, allowing the detection parameters to adapt to different operational stages and resolve the speed-accuracy tradeoff.
2Reliability
If load modulation signaling power is increased to improve signal reliability, then signaling reliability is improved, but compliance with target power range specifications deteriorates
Solution Approach 1:
The system continuously monitors the actual power consumption during load modulation signaling and compares it against the target power range (0.5W-1.1W per A4WP specification). Based on this feedback, the system dynamically adjusts the load modulation depth and duration to maintain compliance while ensuring reliable signal transmission, resolving the contradiction between reliability and precision.
Solution Approach 2:
The system dynamically changes load modulation parameters (depth, duration, timing) based on measured power consumption and communication needs. By adjusting these parameters within the constrained power range, the system maintains both reliability and specification compliance simultaneously.
3Measurement precision
If the system uses multiple beacon periods for accurate PRU detection, then detection accuracy is improved, but initialization time increases
Solution Approach 1:
The initialization process uses a structured sequence of periodic beacons with alternating durations. Short beacons enable rapid initial detection to quickly identify potential PRUs, while long beacons provide accurate validation only when needed. This periodic structure reduces total initialization time compared to using only long beacons, while maintaining detection accuracy through selective use of extended measurement periods.
Solution Approach 2:
The system performs preliminary detection using short beacons to quickly identify candidate PRUs before committing to longer validation beacons. This preliminary action filters out false objects early, reducing the need for extended verification and thereby reducing total initialization time while maintaining accuracy.
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 effectively regulates load modulation signaling, ensuring that the change in conducting power remains within the specified range, even with substantial variations in rectified voltage, thus enhancing the accuracy and compliance of wireless charging systems.
Implementation Method 1
a resonator circuit configured to resonate based on a received charging power and produce a resonance output signal based thereon
Implementation Method 2
a rectifier circuit configured to receive the resonance output signal and convert the resonance output signal to a rectified voltage signal
Data Source
AI summary
A load modulation circuit includes a resonator circuit configured to resonate based on a received charging power and produce a resonance output signal based thereon, and a rectifier circuit configured to receive the resonance output signal and convert the resonance output signal to a rectified voltage signal. The load modulation circuit further includes a sensor circuit configured to sense the rectified voltage signal and generate a control signal based on the rectified voltage signal and a target power range associated with a change in conducting power of the load modulation circuit during a load modulation. Lastly, the load modulation circuit includes a controllable current source circuit configured to generate a controlled current based on the control signal, wherein the controlled current modulates a load of the load modulation circuit while concurrently maintaining a change in total conducting power at an output of the rectified circuit within the target power range.