Isolated Full-Bridge Converter Clamping for High-Voltage Mode Switching
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Solution Overview
Problem
Conventional isolated full-bridge converters face challenges in operating efficiently at high input voltages due to unbalanced MOSFET losses and high blocking voltages when switching between full-bridge and half-bridge modes, leading to increased transformer flux and rectifier semiconductor stress.
Innovation Solution
The implementation of a selective operation mode for the isolated full-bridge converter, utilizing a frequency-doubler half-bridge modulation that balances loss distribution across transistors and employs a clamping technique to reduce transformer cross-section and rectifier blocking voltage, allowing for smoother transitions between operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If half-bridge mode is used to increase operating range at high input voltages, then operating range is improved, but MOSFET loss distribution becomes unbalanced
Solution Approach 1:
The patent implements dynamic switching between full-bridge and half-bridge modes based on operating conditions. The converter can transition from full-bridge mode (where all four MOSFETs are actively switched) to half-bridge mode (where two MOSFETs are continuously on and two are switched), optimizing the loss distribution and operating range dynamically according to the input voltage and load conditions.
Solution Approach 2:
The patent changes the operational parameters of the converter by adjusting the switching patterns of MOSFETs. In full-bridge mode, all MOSFETs switch with 50% duty cycle, while in half-bridge mode, the duty cycles are adjusted to 100% for continuous MOSFETs and variable for pulsed MOSFETs, thereby changing the electrical parameters to optimize performance across different operating conditions.
2Adaptability or versatility
If conventional morphing modulation is used to switch between full-bridge and half-bridge modes, then mode switching capability is improved, but rectifier blocking voltage and transformer flux increase
Solution Approach 1:
The patent applies preliminary clamping action to the transformer before mode transitions occur. By pre-clamping the transformer flux using auxiliary windings and diodes, the system prevents excessive flux buildup during the transition from full-bridge to half-bridge mode, thereby limiting the peak blocking voltage that rectifier MOSFETs must withstand.
Solution Approach 2:
The patent introduces clamping circuits with auxiliary windings and diodes as intermediary elements between the main transformer windings and the rectifier stage. These intermediary components provide a controlled path for flux during mode transitions, preventing direct stress on the rectifier MOSFETs and allowing smoother transitions with reduced voltage spikes.
Data Source
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AI summary
The invention concerns a Full-Bridge Converter (1) that is capable to provide different operation and transition modes that lead to reduced losses and stressing of the components of the Full-Bridge Converter (1). This is achieved by a clamping circuit and applying specific switching patterns to the transistors (S1, S2, S3, S4) of a full bridge of the Full-Bridge Converter (1).