Single-Stage Soft-Switching AC-DC Converter Topology
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Solution Overview
Problem
Conventional transformer isolated AC-DC converters are bulky, inefficient, and generate high electromagnetic interference due to their two-stage design and hard-switching conditions, which limits their efficiency and power density, especially in applications like battery-powered vehicles where compactness and efficiency are crucial.
Innovation Solution
A single-stage soft-switching AC-DC converter with a high frequency transformer and bi-directional switches, such as IGBTs or MOSFETs, that eliminates the intermediate DC link and reduces switching losses by operating at soft-switching conditions, minimizing dv/dt and di/dt, and utilizing transformer leakage inductance for energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional two-stage PWM converter design is used, then galvanic isolation and voltage conversion are achieved, but the converter volume and weight increase
Solution Approach 1:
The patent combines the rectifier and transformer isolation stages into a single integrated circuit topology. The bi-directional switches and leakage inductance are merged with the transformer primary winding, eliminating the need for separate rectifier circuits and DC-link capacitors, thus reducing overall converter volume while maintaining galvanic isolation through the high-frequency transformer.
Solution Approach 2:
The patent transitions from conventional low-frequency power transformation to high-frequency operation. By operating the transformer at high frequency, the required transformer size and volume are dramatically reduced while maintaining the same power transfer capability and galvanic isolation function.
2Power
If a conventional two-stage PWM converter design is used, then voltage conversion is achieved, but the converter weight increases
Solution Approach 1:
The patent merges the rectifier function and transformer isolation function into a single integrated stage. The bi-directional switches connected to the transformer primary winding serve both rectification and isolation purposes simultaneously, eliminating redundant components and reducing overall converter weight.
Solution Approach 2:
The patent changes the operating frequency parameter from conventional low frequency to high frequency. This parameter change enables significant reduction in transformer size and weight while maintaining the required voltage conversion capability through high-frequency magnetic transformation.
3Productivity
If hard-switching conditions are used, then power conversion is achieved, but switching losses increase
Solution Approach 1:
The patent converts the typically harmful leakage inductance into a beneficial resonant element. By utilizing the leakage inductance in conjunction with capacitance to create soft-switching resonant conditions, the circuit achieves zero-voltage or zero-current switching, eliminating switching losses while maintaining effective power conversion.
4Productivity
If conventional PWM switching is used, then power conversion speed is achieved, but electromagnetic interference increases
Solution Approach 1:
The patent converts the leakage inductance, which can cause voltage spikes and EMI in conventional circuits, into a beneficial resonant element that enables soft-switching. This resonant soft-switching approach maintains high power conversion speed while significantly reducing electromagnetic interference by eliminating hard switching transients.
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 results in a more compact, efficient, and low-EMI AC-DC converter with improved power density and reduced volume and weight, suitable for battery-powered vehicles and other applications requiring galvanic isolation and high voltage gain, while minimizing switching losses and electromagnetic interference.
Implementation Method 1
a transformer having a primary side and a secondary side
Implementation Method 2
The transformer primary winding may include one of a center-tapped winding or two separate windings
Data Source
AI summary
An alternating current-to-direct current (AC-DC) converter is provided. The converter may include a transformer having a primary side and a secondary side. A first bi-directional switch and a first inductor may be connected in series between a positive terminal of an AC source and a first terminal of the primary side of the transformer. A second bi-directional switch and a second inductor may be connected between the positive terminal of the AC source and a second terminal of the primary side of the transformer and connected in parallel with the first bi-directional switch.