Wireless Inductive Power Transmitter Control Loop for Load Modulation
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Solution Overview
Problem
Existing wireless power transfer systems face suboptimal performance and communication issues due to the conflict between maintaining constant transmit coil current and using load modulation, particularly in resonant mode where fast and large coil current changes can lead to faulty operations or malfunctions.
Innovation Solution
A power transmitter with a control loop that is active during communication time intervals, featuring an attenuated loop response for small coil current errors and a stronger response for larger errors, allowing simultaneous active power control and load modulation communication, thus mitigating the conflict between power control and communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a control loop is used to maintain constant transmit coil current for stable power transfer, then power transfer stability is improved, but load modulation communication becomes difficult due to suppressed current variations
Solution Approach 1:
The control loop dynamically adjusts its response based on the operating mode. During communication time intervals, the loop response is attenuated to allow load modulation current variations to pass through to the transmitter for detection. Outside communication intervals, the full loop response is applied to maintain constant current and stable power transfer. This dynamic adjustment of control loop characteristics resolves the contradiction between stability and communication capability.
Solution Approach 2:
The system periodically switches between communication time intervals and non-communication time intervals. During communication intervals, load modulation is enabled with attenuated control loop response. During non-communication intervals, full power control is applied. This periodic switching allows both communication and stable power transfer to occur at different times, resolving the fundamental conflict between these two functions.
2Loss of information
If the control loop response is strongly attenuated during communication intervals to enable load modulation, then communication capability is improved, but power transfer control and stability deteriorate
Solution Approach 1:
The control loop's response characteristic is dynamically adjusted based on the timing interval. During communication intervals, the loop response is selectively attenuated to permit load modulation signals to manifest as current variations that can be detected by the transmitter. Outside these intervals, the full control response is restored to maintain constant current and ensure stable power transfer. This dynamic adjustment resolves the contradiction by applying different control strengths at different times.
3Adaptability or versatility
If resonant mode is used to achieve larger distance and positioning freedom, then adaptability is improved, but coil current becomes highly sensitive to load variations causing malfunctions
Solution Approach 1:
The control loop continuously monitors the transmit coil current and provides feedback control to counteract load variations. In resonant mode, where current is highly sensitive to load changes, the control loop detects current deviations and adjusts the drive signal to maintain constant current. This feedback mechanism compensates for the inherent sensitivity of resonant mode, ensuring reliable operation despite positioning freedom and distance variations.
Solution Approach 2:
The system changes the control loop response parameter (loop response attenuation) based on the operating conditions and timing intervals. During communication intervals in resonant mode, the loop response is attenuated to allow load modulation detection. Outside communication intervals, the full control response is applied to counteract load variations and maintain stable operation. This parameter adjustment resolves the contradiction between adaptability and reliability.
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 approach enables improved power transfer performance, reduced sensitivity to fast load variations, and stable control, while allowing efficient communication and power control in both inductive and resonant modes, preventing potential malfunctions caused by large coil current changes.
Implementation Method 1
power is inductively transferred from a transmitter coil in a power transmitter device to a receiver coil in the individual devices
Implementation Method 2
a resonance circuit comprising a transmitter coil for generating a power transfer signal
Data Source
AI summary
A power transmitter (101) inductively transferring power to a power receiver (105) comprises a resonance circuit (201) comprising a transmitter coil (103). A driver (203) generates a drive signal for the resonance circuit (201) and a data receiver (513) receives messages load modulated onto a power transfer signal by the power receiver (105) during communication time intervals. An error unit (507) determines a coil current error and a control loop (511) controls the current through the transmitter coil (103) in response to the coil current error with the control loop (511) being active during the communication time intervals. A loop response of the control loop is attenuated for coil current errors in a reduced control range relative to coil current error indications outside the reduced control range, where the reduced control range includes a zero coil current error.