Secondary Side Modulation for Wireless PFC
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Solution Overview
Problem
Traditional wireless charging systems require a Power Factor Correction (PFC) circuit, which complicates the structure and increases costs, whereas the goal is to achieve PFC through secondary side modulation without an extra PFC circuit.
Innovation Solution
A wireless electric energy transmission system that omits the traditional PFC circuit by converting grid voltage into a 100 Hz voltage through uncontrolled rectification and uses an active full-bridge rectification structure at the secondary side, achieving PFC solely through secondary side modulation by controlling phase shift angles α, β, and γ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a traditional PFC circuit is added to the wireless charging system, then the power factor is improved, but the device complexity and cost increase
Solution Approach 1:
The patent merges the PFC function with the existing secondary side rectifier by utilizing the same switching devices (Q1-Q4) and inductor (L1) to perform both rectification and power factor correction. The rectifier operates in a specific mode where its switching actions naturally shape the input current to be in phase with the input voltage, achieving PFC without requiring a separate PFC circuit stage.
Solution Approach 2:
The secondary side rectifier is designed to serve dual purposes: traditional rectification of the high-frequency AC voltage and power factor correction of the primary side input current. By controlling the rectifier's switching phase and duty cycle, the system simultaneously achieves both functions using a single circuit configuration, eliminating the need for dedicated PFC components.
2Device complexity
If secondary side modulation is used to achieve PFC, then the device complexity is reduced, but the control complexity increases
Solution Approach 1:
The control system employs feedback mechanisms to detect the phase relationship between the input voltage and current, and adjusts the rectifier's switching phase angle accordingly. By monitoring the input current waveform and comparing it with the input voltage, the controller dynamically regulates the rectifier operation to maintain unity power factor, compensating for variations in load and grid conditions.
Solution Approach 2:
The patent achieves PFC by dynamically changing the switching phase angle and duty cycle parameters of the secondary side rectifier. Instead of adding complex hardware, the system modulates the timing and duration of the rectifier's switching operations to shape the input current waveform, using parameter adjustment rather than structural complexity to achieve the desired power factor correction.
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 simplifies the system structure, enhances efficiency, and reduces costs while maintaining a high power factor, as the 50 Hz harmonic wave of the input current is in phase with the input voltage after EMI filtering.
Implementation Method 1
a grid voltage is turned into a 100 Hz voltage through uncontrolled rectification to directly supply power to an inverter of a primary side
Implementation Method 2
wireless electric energy transmission system
Implementation Method 3
an active full-bridge rectifying structure is adopted at a secondary side
Data Source
AI summary
Disclose is a wireless electric energy transmission system for realizing PFC through secondary side modulation. According to the system, on the basis of a traditional wireless charging system topology, a traditional PFC circuit is removed, a grid voltage is turned into a 100 Hz voltage through uncontrolled rectification to directly supply power to an inverter of a primary side of a wireless charging system; an active full-bridge rectifying structure is adopted at a secondary side, and the PFC function is achieved only through secondary side modulation, wherein under the situation that a phase shift angle α of the inverter of the primary side is given.