Wireless Power Transfer Current Sensing for Rectifier Control
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in accurately controlling synchronous rectifiers in high magnetic AC fields, leading to switching errors and increased losses, particularly when dealing with high currents required for charging Li-Ion batteries.
Innovation Solution
A current sensing arrangement that produces a current sense signal based on the AC current flowing from the secondary resonator to the output stage, allowing for enhanced control of the controllable rectifier, reducing errors and losses by sensing high currents rather than small voltages, and using a two-stage current transformer configuration for high accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wireless power transfer systems use conventional voltage sensing methods to control synchronous rectifiers, then the control circuit is simple, but switching errors and losses increase in high magnetic AC fields
Solution Approach 1:
The patent introduces a current sensing arrangement that senses AC current as an intermediary parameter instead of directly sensing voltage. This current sense signal serves as a mediator that is more reliable for controlling synchronous rectifiers in high magnetic AC fields, where voltage sensing becomes inaccurate due to electromagnetic interference.
Solution Approach 2:
The patent replaces the conventional voltage sensing method with a current sensing method. By substituting the sensing target from voltage to current, the system achieves more reliable control of synchronous rectifiers in high magnetic AC fields, as current sensing is less susceptible to electromagnetic interference.
2Measurement precision
If wireless power transfer systems sense small voltages for rectifier control, then the control circuit is simple, but switching errors increase in high magnetic AC fields
Solution Approach 1:
The current sense signal acts as an intermediary that is less affected by magnetic field interference. By sensing current instead of voltage, the system obtains a more accurate control signal that is not as susceptible to electromagnetic interference in high magnetic AC fields.
Solution Approach 2:
The patent converts the challenge of high magnetic AC fields into a benefit by using current sensing. While voltage sensing suffers from magnetic field interference, current sensing through the secondary resonator provides a stable reference that is actually enhanced by the same magnetic environment, turning the harmful magnetic field into a useful sensing mechanism.
3Loss of energy
If wireless power transfer systems use conventional rectifier control methods, then the system is simple, but energy losses increase due to switching errors
Solution Approach 1:
The patent implements a feedback mechanism where the current sense signal from the secondary resonator is used to control the synchronous rectifier switching. This feedback loop ensures that the rectifier switches are controlled based on actual current conditions, reducing switching errors and energy losses while maintaining system efficiency.
Solution Approach 2:
The patent replaces conventional voltage-based control with current-based control for the synchronous rectifier. This substitution reduces switching errors and energy losses by using a control signal (current sense signal) that is more accurate and less susceptible to interference in the high magnetic AC field environment.
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
The solution reduces switching errors and losses in wireless power transfer systems, enabling more reliable and efficient charging of high-capacity batteries with high c-rates by accurately controlling the power transfer based on sensed AC currents.
Implementation Method 1
a primary resonator for receiving the primary AC power and inducing a magnetic field
Implementation Method 2
a secondary resonator for converting the power received through the magnetic field to a secondary AC power
Data Source
Figure 1~5
Figure 6~10
Figure 11~12
AI summary
In a wireless power transfer arrangement (1) power is wirelessly transferred from a primary side (2) to a secondary side (3) across an airgap (8) by means of a primary resonator (6) that generates a magnetic field (9) and a secondary resonator (10) that receives the power by picking up the magnetic field (9). The secondary side (3) includes an output stage (11) that receives the AC power provided by the secondary resonator (10) and generates a DC output (13) to be provided to a load. A current sensing arrangement (18) senses the AC current flowing from the secondary resonator (10) to the output stage (11) and provides a current sense signal (16) to a power transfer controller (15) that controls the power transfer of the wireless power transfer arrangement (1) based on the current sense signal (16). And the current sense signal (16) is provided to a switching controller (20) that controls the switching of a synchronous rectifier of the output stage (11) that converts the AC power (12) provided by the secondary resonator (10) to the DC output (13).