Wireless Power Transmitter Current Detection Circuit
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Solution Overview
Problem
In wireless power transmission, the efficiency of power delivery to a resonator is hindered by changes in impedance due to environmental factors, leading to reduced output power, and existing current detection methods are inefficient, affecting the accuracy of current measurement.
Innovation Solution
A current detection circuit and method that measures the voltage corresponding to the current output to the resonator, using a differential current detection configuration with multiple resistors to extract the voltage component proportional to the AC/RF current while minimizing interference from load changes, allowing for precise current measurement and power adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple current detection method is used, then the device complexity is reduced, but the measurement precision of current deteriorates due to impedance changes and resistor interference
Solution Approach 1:
The detection circuit is segmented into multiple functional components: a differential amplifier stage that separates voltage measurement from current measurement, individual resistors (Rs1, Rs2) for each phase, and a controller that processes signals independently. This segmentation allows each component to perform its specific function optimally, improving measurement precision while keeping the overall circuit manageable through modular design
Solution Approach 2:
Resistors Rs1 and Rs2 are introduced as intermediary elements between the power transmission unit and the detection circuit. These resistors convert the difficult-to-measure current into easily measurable voltage drops, while the differential amplifier acts as an intermediary that eliminates the influence of these resistors from the final measurement, thereby improving accuracy without requiring direct current measurement
2Loss of energy
If power transmission efficiency is improved by accurate current measurement, then the loss of energy is reduced, but the device complexity increases due to the need for precise detection circuits
Solution Approach 1:
The controller receives voltage measurement values from the detection circuit and uses this feedback to adjust the power transmission in real-time. When impedance changes are detected through the measured voltage, the controller automatically adjusts the transmission power to maintain optimal efficiency, creating a closed-loop system that reduces energy loss through continuous optimization
Solution Approach 2:
The system dynamically changes the power transmission parameters (voltage, current, frequency) based on the measured voltage values and detected impedance changes. By adjusting these parameters in response to environmental conditions, the system maintains high transmission efficiency without requiring overly complex detection hardware
3Measurement precision
If the influence of resistors is eliminated for accurate load change detection, then the measurement precision is improved, but the device complexity increases due to the differential detection configuration
Solution Approach 1:
The differential amplifier configuration inherently handles asymmetry in the circuit by measuring the difference between two symmetric channels. Even though the physical circuit is symmetric with matching resistors and components, the differential measurement approach asymmetrically processes the signals to cancel out common-mode errors including resistor influences, thereby improving measurement precision
Solution Approach 2:
Each phase (positive and negative) has its own dedicated resistor and measurement path with locally optimized components. The differential amplifier selectively processes only the differential signal while rejecting common-mode signals, giving each part of the circuit a specific local function that contributes to overall measurement 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
This approach enhances the accuracy of current detection and power transmission efficiency by isolating the desired voltage component from interference, enabling effective power adjustment based on measured current values, thus improving the overall performance of wireless charging systems.
Implementation Method 1
measuring a voltage value corresponding to a current that is output to the power transmission unit
Data Source
AI summary
A wireless power transmitter and a method for detecting a change in load during wireless charging in the wireless power transmitter is provided. The wireless power transmitter includes a power transmission unit configured to transmit power to a wireless power receiver, a current detection unit configured to measure a voltage value corresponding to a current that is output to the power transmission unit while the power is transmitted from the power transmission unit, and a controller configured to adjust the power transmitted by the power transmission unit based on the measured voltage value.