LLC Resonant Converter Input Voltage Calibration
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Solution Overview
Problem
Current LLC resonant converter designs rely on empirical approaches that do not achieve high efficiency across all load conditions and output voltages due to tolerances in resonant inductor and capacitor values, using worst-case conditions and look-up tables or closed-loop resonant frequency adjustments.
Innovation Solution
A method and system where a controller calculates the input voltage mathematically based on output voltage, load current, and component tolerances, operating the LLC converter in an open loop mode at a nominal resonant frequency and measuring the output voltage to compare with the calculated value, using a mathematical equation to optimize bus voltage and compensate for tolerances without frequency measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an empirical approach using worst-case conditions is used to determine input voltage, then the converter can accommodate all component tolerances, but efficiency is not achieved at all load conditions and output voltages
Solution Approach 1:
The patent changes the control parameter from fixed worst-case input voltage to dynamically calculated input voltage based on actual operating conditions (output voltage, load current, frequency). This allows the system to adapt to real component values rather than designing for extreme tolerances, improving efficiency while maintaining reliability through continuous adjustment.
Solution Approach 2:
The system implements feedback by measuring actual output voltage and load current, then using these measurements to calculate and adjust the optimal input voltage. This closed-loop approach ensures the converter operates at peak efficiency while still accommodating component variations through real-time compensation.
2Ease of operation
If a look-up table method is used to determine input voltage, then the converter operates at nominal resonant frequency, but efficiency is compromised compared to mathematical optimization
Solution Approach 1:
The patent replaces the discrete look-up table method with a continuous mathematical calculation system. Instead of selecting from pre-defined voltage values based on frequency tables, the system calculates optimal input voltage using mathematical relationships involving output voltage, load current, and frequency, providing smoother and more precise efficiency optimization.
3Reliability
If closed-loop resonant frequency adjustment is used, then the converter adapts to component tolerances, but system complexity increases
Solution Approach 1:
The patent extracts the frequency measurement function from the control loop, using only the nominal resonant frequency value while calculating optimal input voltage mathematically based on other measurable parameters (output voltage, load current). This removes the need for complex frequency sensing and adjustment hardware while still adapting to component tolerances through mathematical compensation.
4Loss of energy
If mathematical calculation of input voltage is implemented, then efficiency is optimized across operating conditions, but measurement and calculation complexity increases
Solution Approach 1:
The patent makes the existing output voltage and load current measurements serve dual purposes: they are used for normal control functions and simultaneously for calculating optimal input voltage. This eliminates the need for separate measurement systems, as the same sensors and ADCs used for basic control are leveraged for efficiency optimization through mathematical calculation.
Data Source
AI summary
Methods and systems for calibrating an inductor-inductor-capacitor (LLC) resonant converter are provided herein. The method includes calculating input voltage mathematically as a function of at least one of an output voltage, a load current, and tolerances of components of the LLC resonant converter and operating the LLC resonant converter in an open loop mode at a nominal resonant frequency. The method also includes measuring output voltage of the LLC resonant converter and comparing the measured output voltage to the calculated input voltage.