High-Frequency AC-DC Converter Resonant Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional high-frequency AC to DC conversion systems suffer from poor power factor, high conduction loss, and electromagnetic interference due to distorted current, making them inefficient for high-frequency wireless power transfer applications.
Innovation Solution
The proposed solution employs a resonant technique to shape the line current sinusoidally and operate semiconductor devices at the fundamental frequency of the AC source, using a half-wave rectifier with an inductive-capacitive load and a switched capacitor bank to achieve power factor correction and output voltage regulation, with a control scheme realized by simple operational amplifiers and digital logic gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a diode rectifier with capacitor is used for AC to DC conversion, then the circuit is simple, but the power factor is poor and current is highly distorted
Solution Approach 1:
A resonant inductor is introduced as an intermediary component between the AC source and diode rectifier. This inductor shapes the input current waveform to be sinusoidal and in phase with the voltage, acting as a mediator that eliminates current distortion and improves power factor without complicating the overall circuit structure significantly
Solution Approach 2:
The invention changes the operating parameters by operating the resonant inductor at the fundamental frequency of the AC source rather than using high-frequency switching. This parameter change allows the system to achieve power factor correction while avoiding the complexities of high-frequency switching circuits
2Object-generated harmful factors
If a boost converter is used for power factor correction, then the current waveform is sinusoidal and in phase with voltage, but the switching frequency must be many times higher than the AC system frequency
Solution Approach 1:
Instead of using high-frequency switching to shape the current waveform, the invention inverts the approach by using a resonant inductor operated at the fundamental AC frequency to naturally shape the current. This reverses the conventional wisdom that high-frequency switching is necessary for current shaping
Solution Approach 2:
The resonant inductor operates periodically at the fundamental frequency of the AC source, synchronizing its operation with the voltage cycles. This periodic operation at the fundamental frequency eliminates the need for high-frequency switching while maintaining sinusoidal current waveform quality
3Object-generated harmful factors
If switching frequency is increased to tens of megahertz for current shaping, then the current waveform can follow voltage, but switching loss becomes significant and efficiency is sharply reduced
Solution Approach 1:
The invention changes the critical parameter of switching frequency from tens of megahertz to the fundamental AC frequency (50/60 Hz or similar). This dramatic parameter reduction eliminates significant switching losses while maintaining the ability to control and shape the current waveform through resonant operation
4Object-generated harmful factors
If conventional PFC technology is used in high frequency AC system, then current shaping is achieved, but EMI, thermal, insulation and isolation problems become difficult to solve
Solution Approach 1:
The invention extracts and eliminates the high-frequency switching stage from the system, retaining only the essential resonant inductor operated at fundamental frequency. This extraction removes the source of EMI, thermal, and insulation problems while preserving the current shaping capability through resonant operation
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 reduces switching losses, improves power factor to near unity, and enhances energy efficiency while minimizing electromagnetic interference, making it suitable for high-frequency AC to DC conversion in wireless power transfer systems.
Implementation Method 1
Based on the resonant technique, the line current is shaped to be sinusoidal and is forced to follow the line voltage
Implementation Method 2
the AC power output from the receiver is first converted to a DC voltage. The simplest approach is to use a diode rectifier
Implementation Method 3
use a diode rectifier with a capacitor connected at the DC output side
Data Source
Figure 1(a)~2(b)
Figure 3~4(c)
Figure 5(a)~5(b)
AI summary
A high-frequency AC-DC power converter takes an input AC signal and converts it to an output DC signal. The converter has at least two front-end rectifier diodes arranged as a full wave rectifier of the input AC signal. A first inductor positioned at the output of the full wave rectifier. An output capacitor is connected across a load for the converter. There are at least one additional inductor and one additional capacitor. A switching circuit selectively forms different LC resonant circuits with the inductors and capacitors during a cycle of the input AC signal to form a AC-DC power converter.