Wireless Power Receiver Control Circuit for Qi Communication Stability
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Solution Overview
Problem
In wireless power supply systems conforming to the Qi standard, sudden changes in charging current can lead to deviations in rectified voltage, disrupting communication between the power transmitter and receiver, and potentially causing feedback loop cutoffs due to adverse effects on AM modulation using backscatter modulation.
Innovation Solution
A control circuit in the power receiver that includes a charging control unit and a power control unit, which adjusts the charging current in a stepwise manner and maintains it until the rectified voltage difference from the target value is within a predetermined threshold, preventing sharp changes and stabilizing communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging current is increased to improve charging speed, then the productivity is improved, but the rectified voltage deviates from the target value causing communication disruption
Solution Approach 1:
The charging control unit dynamically adjusts the charging current based on real-time rectified voltage measurements. When the rectified voltage deviates from the target value, the system automatically reduces the charging current to restore voltage stability, ensuring continuous communication while maintaining efficient charging when conditions permit
Solution Approach 2:
The system implements a feedback mechanism where the charging control unit continuously monitors the rectified voltage and compares it against the target value. Based on this feedback, the charging current is adjusted in real-time to maintain voltage within acceptable ranges, preventing communication disruption while optimizing charging speed
2Speed
If the charging current is changed abruptly to improve response time, then the speed is improved, but the rectified voltage waveform changes adversely affecting AM modulation
Solution Approach 1:
The charging control unit implements dynamic current adjustment that responds to voltage deviations while maintaining waveform stability. The control algorithm adjusts current in a controlled manner that prevents abrupt changes, thereby avoiding waveform distortion that would interfere with AM modulation of communication signals
Solution Approach 2:
The system prepares for potential voltage deviations by implementing proactive current adjustment. When voltage begins to deviate from the target value, the charging control unit anticipates further deviation and adjusts the current beforehand to prevent waveform distortion and communication interference
3Productivity
If the charging current is maintained at high levels to improve power transmission efficiency, then the productivity is improved, but the rectified voltage deviates causing feedback loop cutoff
Solution Approach 1:
The charging control unit continuously adapts the charging current based on rectified voltage conditions. When voltage deviation threatens feedback loop continuity, the system dynamically reduces current to maintain stable operation, ensuring uninterrupted communication and control while maximizing power transmission efficiency when conditions allow
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 solution stabilizes communication between the power transmitter and receiver by preventing significant deviations in rectified voltage and waveform changes, ensuring continuous and reliable power transmission.
Implementation Method 1
The reception coil 302 receives the electric power signal S2 from the transmission coil 202
Implementation Method 2
The rectifier circuit 304 and the capacitor 306 rectify and smooth a current S4 induced at the reception coil 302 according to the electric power signal S2, thereby converting the current S4 into a DC voltage
Implementation Method 3
The control signal S3 is transmitted from a reception coil 302 (secondary coil) to the transmission coil 202 in the form of an AM (Amplitude Modulation) modulated signal using backscatter modulation
Implementation Method 4
The control signal S3 is transmitted from a reception coil 302 (secondary coil) to the transmission coil 202 in the form of an AM (Amplitude Modulation) modulated signal using backscatter modulation
Data Source
AI summary
A rectifier circuit is coupled to a reception coil, and generates a rectified voltage. A charger circuit receives the rectified voltage, and charges a secondary battery. A modulator coupled to the reception coil modulates a voltage or a current applied to the reception coil based on a control value, and transmits a control packet including the control value to a wireless power transmitter. A charging control unit controls a charging current supplied from the charger circuit to the secondary battery. A power control unit generates a control error value indicating a power transmission rate for the wireless power transmitter, based on the difference between the present rectified voltage and its target value, and outputs the control error value as the control value to the modulator. When the absolute value of the difference is smaller than a predetermined threshold value, the charging control unit changes the charging current.