T-Type LCL Resonant Converter for Full-Range Soft Switching
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Solution Overview
Problem
High-frequency isolated DC-DC resonant converters, such as DAB converters, face challenges in maintaining soft switching across a full power range due to voltage mismatches, leading to efficiency losses, and existing solutions like TPS control increase complexity without achieving soft switching for all switches.
Innovation Solution
A T-type LCL resonant converter with a soft switching modulation method that adjusts pulse widths and current phases to achieve symmetrical and square waveforms, enabling soft switching operations for all switching transistors across the full power range, minimizing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If DAB converters are used to achieve galvanic isolation and high switching frequency, then converter efficiency is improved, but soft switching is lost when voltage mismatch occurs
Solution Approach 1:
The patent changes the circuit topology parameters by introducing a T-type bridge configuration on the primary side with two series resonant inductors and a resonant capacitor, transforming the circuit from a standard DAB to a T-type LCL resonant converter. This parameter change enables the circuit to maintain soft switching capability across the full power range while preserving high efficiency
2Reliability
If TPS control is used to extend soft switching power range, then soft switching is achieved under light loads, but control complexity increases sharply
Solution Approach 1:
The patent simplifies the control parameters by using a fixed phase shift of π/2 between primary and secondary bridges, eliminating the need for complex multi-phase shift control. The T-type topology inherently provides soft switching capability, so simple phase shift control is sufficient to achieve full power range soft switching without increasing control complexity
3Use of energy by moving object
If series resonant converters or LLC resonant converters are used to improve efficiency, then converter efficiency is improved, but soft switching cannot be achieved under full power range
Solution Approach 1:
The patent segments the resonant circuit into two series resonant inductors (Lr1 and Lr2) with a resonant capacitor, forming a T-type LCL resonant tank. This segmentation allows the circuit to achieve full power range soft switching while maintaining high efficiency, overcoming the limitations of conventional series or parallel resonant converters
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 T-type LCL resonant converter with the proposed soft switching modulation method maintains unit power factor operations, reduces conduction losses, and improves efficiency by ensuring soft switching for all transistors, thus enhancing the converter's performance across the full power range.
Implementation Method 1
the resonant tank includes a first resonant inductor L1, a second resonant inductor L2, and a resonant capacitor C disposed at a primary side
Implementation Method 2
a high-frequency transformer, and a secondary side half bridge connected in that order; the primary full bridge includes a switching transistor S1, a switching transistor S2, a switching transistor S3, and a switching transistor S4
Data Source
AI summary
A T-type inductor-capacitor-inductor (LCL) resonant converter and its soft switching modulation method under a full power range. A full bridge inverter circuit is provided at a primary side of a T-type inductor-capacitor-inductor (LCL) resonant converter. The full bridge inverter circuit includes four metal-oxide-semiconductor (MOS) transistors. A half bridge rectifier circuit is provided at a secondary side of the T-type LCL resonant converter, and the half bridge rectifier circuit includes two MOS transistors and two equalizing capacitors. The soft switching modulation method for the T-type LCL resonant converter under a full power range is provided based on the T-type LCL resonant converter. The soft switching modulation method requires all switching transistors to operate at a duty cycle of 50% within one cycle. A high-frequency alternating voltage of the primary side has a symmetrical waveform, and a high-frequency alternating voltage of the secondary side has a square waveform.