LLC DC-DC Converter Input Voltage Control via Lookup Tables
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Solution Overview
Problem
Existing methods for controlling the DC voltage at the input of LLC DC-to-DC converters in electric battery chargers for electric vehicles are not satisfactory, as they are complex, expensive, and require recalculating transfer functions for each operating point change, especially when the output voltage varies over a wide range.
Innovation Solution
A method for controlling the frequency of the input voltage of a DC current to DC current converter by defining maximum and minimum control frequency values, setpoint voltage, and error limits, calculating a control frequency based on measured voltage within these limits, and using a proportional-integral controller for precise convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transfer function methods are used to control DC voltage at the input of LLC DC-to-DC converters, then control precision can be achieved, but the system becomes complex and expensive requiring recalculations for each operating point change
Solution Approach 1:
The patent segments the control process into two distinct parts: a simple frequency measurement stage and a lookup table-based control stage. Instead of using complex transfer function calculations for every operating point, the system pre-calculates control parameters and stores them in lookup tables, dividing the complex control problem into manageable segments that can be executed efficiently
Solution Approach 2:
The patent applies preliminary action by pre-calculating the control parameters and storing them in lookup tables before actual operation. The transfer function calculations are performed in advance during system initialization or parameter changes, rather than being recalculated for every operating point change during runtime, thus eliminating the need for repeated complex computations
2Adaptability or versatility
If complex control methods with recalculated transfer functions are used, then adaptability to different operating points is improved, but computation time and cost increase significantly
Solution Approach 1:
The patent pre-calculates control parameters for various operating conditions and stores them in lookup tables. When the operating point changes, the system simply looks up the pre-computed parameters rather than recalculating transfer functions, maintaining adaptability while dramatically reducing computation time
Solution Approach 2:
The patent creates simplified copies of the control parameters in the form of lookup tables that contain pre-computed values. Instead of performing complex transfer function calculations during operation, the system uses these copied parameter sets, which can be quickly retrieved and applied without significant computation time
3Power
If frequency control is used to regulate DC bus voltage, then the gain of DC-to-DC can be adjusted, but the control method becomes complex when output voltage varies over wide range
Solution Approach 1:
The patent replaces complex mechanical-style transfer function calculations with a simpler electronic lookup table system. Instead of performing analog-like mathematical operations for every control decision, the system uses digital lookup tables that provide direct parameter retrieval, substituting complex computational mechanics with simpler data access operations
Solution Approach 2:
The patent changes the control parameter from continuous transfer function calculations to discrete lookup table entries. By organizing control parameters as selectable entries based on operating conditions rather than continuous mathematical functions, the system simplifies the control method while maintaining the ability to adjust gain across wide voltage ranges
Data Source
AI summary
A method for controlling the input voltage frequency of a DC-DC converter includes calculating a control frequency value of the DC-DC converter. If the measured voltage is greater than the upper voltage limit, the control frequency corresponds to the minimum control frequency. If the measured voltage is less than the lower voltage limit, the control frequency corresponds to the maximum control frequency. If the measured voltage is between the upper voltage limit and the lower voltage limit, the control frequency corresponds to an average frequency calculated as a function of the difference between the setpoint voltage value and the measured voltage, upper error values and lower error values, and maximum and minimum control frequency values.