Wireless Power Transfer Using Transmitter Coil Voltage Sensing
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Solution Overview
Problem
Current wireless power transfer systems face challenges in maintaining robust data reception and preventing dead spots due to low signal amplitude and distortion under misaligned conditions, particularly in automotive applications with stringent vibration requirements, and the cost and complexity of current sensing circuitry.
Innovation Solution
A wireless power transfer system utilizing transmitter coil voltage sensing, which includes a DC-to-AC power inverter, a transmitter tuned circuit with a series-connected capacitor and coil, a voltage sampling circuit, and a data communications circuit for modulating and demodulating voltage control data, allowing for efficient power control and data transmission without the need for current sensing circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensing circuitry such as current transformer (CT) is used to detect transmitter coil current, then power transfer control and communication can be achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent introduces voltage sensing as an intermediary measurement method instead of directly sensing current. By measuring the voltage across the transmitter coil and using the known impedance relationship, the system derives current information indirectly. This mediator approach (voltage measurement) replaces the complex direct current sensing circuitry while maintaining the necessary control and communication functions.
Solution Approach 2:
The patent replaces the mechanical/electrical current sensing system (current transformer) with an electrical voltage sensing system. By substituting the measurement domain from current to voltage, the system eliminates the need for bulky and expensive current transformers, reducing device complexity while achieving the same control objective through electrical parameter transformation.
2Power
If current sensing circuitry with sufficient current carrying capacity is provided, then maximum power transfer can be controlled, but cost becomes significant
Solution Approach 1:
The patent employs inexpensive voltage sensing components (voltage divider, ADC) instead of expensive current transformers. The voltage sensing circuit uses simple resistive dividers and standard analog-to-digital converters that are far cheaper than current sensing equipment with sufficient power handling capacity. This substitution maintains full power transfer control capability while dramatically reducing component cost.
Solution Approach 2:
The patent changes the measurement parameter from current to voltage. By measuring voltage across the transmitter coil and using the relationship I = V/Z (where Z is impedance), the system controls maximum power transfer without requiring current-sensing-capable components. This parameter transformation allows using low-cost voltage measurement electronics instead of expensive high-current sensing circuitry.
3Adaptability or versatility
If transmitter coil current is used as reference for power control, then power level can be adjusted according to receiver feedback, but hardware requirements increase
Solution Approach 1:
The patent makes the voltage sensing circuit serve multiple functions: it provides the reference for power level adjustment, enables communication packet detection, and supports adaptive power control. By using voltage as a universal reference parameter, the system achieves adaptability in power control without requiring separate current sensing hardware, communication detection circuitry, and power management components.
Solution Approach 2:
The patent merges the functions of power control reference, communication detection, and power level adjustment into a single voltage sensing system. Instead of having separate current sensing circuitry for power control and separate detection mechanisms for communication, the voltage across the transmitter coil serves as a unified reference for all these functions, reducing overall hardware requirements while maintaining adaptability.
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 reduces hardware requirements, achieves robust wireless charging control under various conditions, and provides a compact, cost-effective implementation by using transmitter coil voltage for communication and power control, effectively addressing misalignment issues and reducing the risk of transmitter shutdown.
Implementation Method 1
A Qi wireless power transfer system consists of a transmitter and a receiver magnetically coupled together with inductive coils
Implementation Method 2
A circuit for sampling voltage on the transmitter power coil is provided, by which amplitude and phase of the voltage may be determined
Data Source
AI summary
In a wireless power transfer system for supplying power to a wireless device, e.g., charging a battery, wireless power transmitter coil voltage is used in place of coil current for communication and power control reference. The transmitter coil voltage waveforms provide phase information, with reference to the pulse width modulation (PWM) waveforms, that can be used to demodulate digital packet communication from a wireless power receiver used to provide a voltage to a device. The DC voltage amplitude of the wireless power transmitter coil is used for controlling the power injected to the wireless power receiver coil, while the phase of the transmitter coil voltage PWM signal is used for demodulation of signal packets from the wireless power receiver to control the transmitter coil voltage and thereby wireless power transfer to the power receiver.