Wireless Charging PWM Timing Near Zero-Crossings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multiple pulse width modulation (M-PWM) and sinusoidal pulse width modulation (S-PWM) in wireless charging systems result in spurious zero-crossings due to low power and current levels near polarity changes, leading to undesirable voltage fluctuations and complexity in demodulation processes.
Innovation Solution
Modify the M-PWM driver signal by reducing the interval between zero-crossings and the closest pulses, such as broadening or adjusting the timing of pulses near zero-crossings, to prevent polarity changes and spurious zero-crossings, thereby enhancing energy transfer efficiency and simplifying demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If M-PWM or S-PWM signal is used in wireless power transfer, then the average current in the digital PWM signal varies in line with the modulating wave, but the receiver waveform has additional or spurious zero-crossings due to low power and current levels near polarity changes
Solution Approach 1:
The patent applies preliminary action by modifying the PWM driver signal in advance before it causes spurious zero-crossings. Specifically, the interval between zero-crossings and adjacent pulses is adjusted beforehand to ensure sufficient energy transfer that prevents voltage polarity bouncing, thereby eliminating spurious zero-crossings before they can occur in the receiver waveform
Solution Approach 2:
The patent changes the temporal parameters of the PWM signal by reducing the interval between zero-crossings and adjacent pulses. This parameter modification increases the energy delivered during critical transition periods, preventing the voltage across the receiving coil from bouncing around zero and causing spurious zero-crossings
2Use of energy by moving object
If the interval between zero-crossing and adjacent pulses is reduced, then energy transfer to the receiving coil is increased, but the pulse width modulation complexity increases
Solution Approach 1:
The patent applies local quality by making modifications only to specific portions of the PWM signal - namely the intervals adjacent to zero-crossings - rather than changing the entire signal structure. This localized approach increases energy transfer where needed while minimizing overall signal complexity and maintaining the fundamental PWM structure
3Device complexity
If spurious zero-crossings are reduced, then demodulation process is simplified and communication protocol accuracy is improved, but the control precision required for pulse interval adjustment increases
Solution Approach 1:
The patent employs feedback mechanisms to achieve the required control precision for pulse interval adjustment. By monitoring the actual waveform characteristics and comparing them against desired outcomes, the system can dynamically adjust the interval modifications to eliminate spurious zero-crossings while maintaining accurate control without excessive complexity
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
Increased energy transfer and reduced spurious zero-crossings improve the stability of the voltage across the receiving coil, facilitating accurate frequency determination and simplified demodulation for communication protocols.
Implementation Method 1
using the modified M-PWM driver signal to open and close a switch in a wireless power transfer charging circuit
Implementation Method 2
energy, which is transferred to a coil in a receiving device by means of wireless power transfer from the wireless charging circuit
Data Source
AI summary
Transferring wireless power using a multiple pulse width modulation M-PWM driver signal includes generating the multiple PWM driver signal such that the pulse width varies in accordance with the magnitude of a periodic modulating curve. The M-PWM driver signal adjacent a zero-crossing of the periodic modulating wave is modified by reducing an interval between the zero-crossing and at least one pulse of the M-PWM driver signal closest to the zero-crossing. The modified M-PWM driver signal is used to open and close a switch in a wireless power transfer charging circuit.