LLC Resonant Converter Hybrid Mode Control for Wide Voltage Range
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Solution Overview
Problem
Current LLC resonant converters face challenges with wide battery voltage ranges, leading to large burst mode intervals and insufficient voltage supply for inverters, especially during bidirectional operations, resulting in high output voltage ripple and increased complexity due to open-loop control methods.
Innovation Solution
A hybrid mode control method that dynamically switches between burst, PWM, PFM, and PSM modes based on load and voltage conditions, using fixed or variable duty cycles and frequencies to stabilize output voltage and maintain voltage gain, particularly in charging and discharging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LLC resonant converter operates in burst mode to handle wide voltage range, then the voltage gain is improved, but the output voltage ripple becomes too large and the burst mode interval becomes too large
Solution Approach 1:
The patent implements dynamic mode switching between burst mode, PWM mode, and PFM mode based on real-time operating conditions (input voltage, output voltage, load). This dynamic adjustment allows the system to operate in burst mode for high voltage gain when needed, while switching to PWM or PFM modes to reduce output voltage ripple under different conditions, thereby resolving the contradiction between voltage gain and ripple suppression
Solution Approach 2:
The patent changes operational parameters (switching frequency, duty cycle, and control mode) based on the operating state. By adjusting these parameters dynamically, the system achieves high voltage gain in burst mode when required, while transitioning to other modes with different parameter characteristics to minimize output voltage ripple, thus resolving the technical contradiction
2Power
If the voltage gain is increased through delay time control to supply sufficient voltage to inverter, then the voltage supply capability is improved, but the software complexity increases due to open-loop table lookup method
Solution Approach 1:
The patent employs closed-loop feedback control where the controller continuously monitors output voltage and adjusts the switching signals accordingly. This feedback mechanism eliminates the need for complex open-loop table lookup methods while maintaining accurate voltage supply capability, as the system automatically adapts to changing conditions through real-time measurement and adjustment
Solution Approach 2:
The patent extracts the complex table lookup logic and replaces it with a simpler feedback-based control algorithm. By removing the unnecessary complexity of pre-computed tables and conditional logic, the system achieves the same voltage supply capability through a more straightforward feedback control mechanism, thereby reducing software complexity
Data Source
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AI summary
A hybrid mode control method includes steps of: controlling an LLC resonant converter to operate in a burst mode when the LLC resonant converter is in a light load (S11, S21). Afterward, controlling the LLC resonant converter operating in a PWM mode as a load of the LLC resonant converter increases or an output voltage increases in a charging control (S12), or controlling the LLC resonant converter operating in a PFM mode as the load increases or the input voltage decreases in a discharging control (S22). Afterward, controlling the LLC resonant converter to operate in the PFM mode as the load of the LLC resonant converter further increases or the output voltage further increases in the charging control (S13), or controlling the LLC resonant converter operating in a PSM mode as the load further increases or the input voltage further decreases in the discharging control (S23).