Dynamic LC Tank Circuits for Phase-Shift Converter ZVS
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Solution Overview
Problem
Conventional PWM converters face limitations in operating at higher switching frequencies due to circuit parasitics, which lead to increased switching losses and reduced efficiency, and resonant converters suffer from increased conduction losses and variable frequency operation disadvantages.
Innovation Solution
The implementation of intelligently-selectable LC tank circuits in full-bridge phase-shift power converters, which are added or removed based on load conditions to maintain zero-voltage switching (ZVS), minimizing the impact on overall efficiency by using the minimum number of LC tank circuits for the shortest duration necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent LC tank circuits are added to maintain zero-voltage switching, then ZVS is achieved under all load conditions, but RMS current of main power switching increases reducing efficiency
Solution Approach 1:
The system dynamically activates or deactivates specific LC tank circuits based on detected load conditions. Under light load conditions, the first LC tank circuit is activated to maintain ZVS. Under heavy load conditions, the first LC tank circuit is deactivated and the second LC tank circuit is activated, thereby adapting the circuit configuration to minimize RMS current and maximize efficiency at each operating point.
Solution Approach 2:
The patent segments the load operating range into different regions (light load and heavy load) and assigns different LC tank circuits to different segments. This segmentation allows each tank circuit to be optimized for its specific operating range, preventing the inefficiencies that would result from using a single permanent tank circuit configuration for all loads.
2Power
If higher switching frequencies are used to achieve higher power density, then power density increases, but circuit parasitics cause increased switching losses and component stresses
Solution Approach 1:
The patent converts the harmful effect of circuit parasitics (which worsen at higher switching frequencies) into a beneficial effect by using resonant techniques. The LC tank circuits are designed to resonate at the higher switching frequency, transforming the parasitic inductance and capacitance from sources of loss into components that enable zero-voltage switching and reduce overall switching losses despite the higher frequency 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 allows for efficient ZVS maintenance across a wide range of load conditions while minimizing additional losses, enhancing the power conversion circuit's efficiency and reducing component stresses.
Implementation Method 1
one or more resonant LC tank circuits configured to be selectively coupled to the output nodes in response to load conditions so as to maintain zero voltage switching of the switching devices
Data Source
AI summary
This disclosure relates to improved designs for phase-shift power converters, and, in particular, full bridge converters. Phase-shift power converters may lose Zero-Voltage-Switching (ZVS) under some load conditions, e.g., light load conditions—which can result in large switching losses. In order to avoid these losses, additional LC tank circuits may be added into the system to generate an amount of negative current needed to maintain ZVS. However, permanently adding such LC tank circuits into the system will reduce the system's efficiency. By intelligently adjusting the number (and particular combination) of LC tank circuits included in the system at a given time, ZVS may be maintained under all load conditions, while the impact of the additional LC tank circuits on the converter's overall efficiency may be limited, e.g., by employing the minimum number of LC tank circuits for the minimum amount of time needed to maintain ZVS.