Full-Bridge Resonant Converter Interleaving for Soft MOSFET Switching
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Solution Overview
Problem
Existing full-bridge resonant converters face issues with high switching losses, temperature rise, and efficiency decrease due to hard switching of MOSFETs under light load or low voltage conditions, leading to component damage and reduced service life.
Innovation Solution
An interleaved control method with asymmetric and non-complementary characteristics for the full-bridge resonant converter, where switches are operated in alternating patterns to achieve soft switching and reduce switching losses, dispersing heat and avoiding temperature concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional full-bridge resonant converter control is used, then the converter can operate under various load conditions, but MOSFET switching losses increase and efficiency decreases under light load or low voltage conditions
Solution Approach 1:
The patent applies dynamic control by switching between two different operating modes: Mode 1 uses asymmetric non-complementary interleaved control where Q1 and Q3 are turned on first, while Mode 2 uses symmetric complementary interleaved control where all switches are turned on simultaneously. This dynamic adaptation allows the converter to optimize switching losses under light load conditions while maintaining efficient operation under heavy load conditions, directly resolving the contradiction between reducing switching losses and maintaining productivity.
Solution Approach 2:
The patent changes the switching control parameters by introducing asymmetric duty cycles and phase shifts between bridge arms. Specifically, it employs different turn-on timings for Q1/Q3 versus Q2/Q4 in Mode 1, and adjusts the interleaving phase difference dynamically. These parameter changes enable soft switching conditions under light load, reducing MOSFET switching losses while maintaining the required power conversion productivity.
2Reliability
If MOSFETs are operated in hard switching mode, then the control is simple, but temperature rises and component service life decreases
Solution Approach 1:
The patent dynamically switches between Mode 1 (asymmetric non-complementary interleaved control) and Mode 2 (symmetric complementary interleaved control) based on operating conditions. Under light load conditions, Mode 1 creates overlapping conduction periods where Q1/Q3 turn on before Q2/Q4, enabling soft switching and reducing MOSFET temperature. This dynamic mode switching maintains reliability by avoiding hard switching temperature stress while preserving component service life.
Solution Approach 2:
The patent implements periodic interleaved control where the two bridge arms operate with phase shifts. In Mode 1, the asymmetric interleaving creates periodic soft switching opportunities that reduce peak temperatures. In Mode 2, the symmetric complementary interleaving distributes thermal stress periodically across all switches. This periodic action prevents temperature concentration and extends component service life.
3Loss of energy
If asymmetric non-complementary interleaved control is used, then switching losses are reduced, but the control complexity increases
Solution Approach 1:
The patent segments the control into two distinct modes with clear operational boundaries. Mode 1 (asymmetric non-complementary interleaved control) is activated under light load conditions to reduce switching losses, while Mode 2 (symmetric complementary interleaved control) handles heavy load conditions. This segmentation allows the complex asymmetric control to be applied only when necessary, reducing overall control complexity while maintaining switching loss reduction benefits.
Solution Approach 2:
The control system automatically selects between Mode 1 and Mode 2 based on real-time operating conditions without requiring complex external intervention. The asymmetric non-complementary interleaved control in Mode 1 self-adjusts the switching sequences to achieve soft switching, reducing switching losses while the embedded control logic manages the complexity internally, making the increased control complexity transparent to the user.
4Productivity
If burst mode is used under light load, then efficiency is improved, but output transient ripples increase
Solution Approach 1:
The patent dynamically transitions between burst mode and continuous interleaved control based on load conditions. Under light load, it employs asymmetric non-complementary interleaved control (Mode 1) that maintains continuous operation with reduced switching losses, avoiding the transient ripples of burst mode while preserving efficiency. The dynamic adaptation allows the system to maintain output stability by preventing the on-off cycling characteristic of burst mode, thus eliminating transient ripples while keeping efficiency high.
Data Source
AI summary
A method of controlling a full-bridge resonant converter includes steps of: operating a first upper switch in a first control action during a first time interval; operating a first lower switch in a second control action during the first time interval; operating a second upper switch in a third control action during the first time interval; operating a second lower switch in a fourth control action during the first time interval; operating the first upper switch in the fourth control action during a second time interval after the first time interval; operating the first lower switch in the third control action during the second time interval; operating the second upper switch in the second control action during the second time interval; operating the second lower switch in the first control action during the second time interval.