OBC LLC Converter Resonance Frequency Control
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Solution Overview
Problem
Existing on-board charger (OBC) systems for eco-friendly vehicles face efficiency issues due to variations in resonance circuit elements, leading to suboptimal operation of LLC converters, which affects the overall electric efficiency of the vehicle.
Innovation Solution
A method and system that control the DC link voltage of the OBC to ensure the LLC converter operates at a resonance frequency by detecting switching and conduction times, determining the operating frequency region, and adjusting the input voltage accordingly to maintain resonance frequency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a DC link voltage variable map is used based on design values, then the OBC can operate at maximum efficiency under ideal conditions, but efficiency varies significantly when element errors occur in the resonance tank
Solution Approach 1:
The patent implements a feedback control mechanism that detects the actual resonance frequency through switching turn-on time and diode conduction time measurements, then adjusts the DC link voltage to maintain operation at the resonance frequency despite element value variations. This closed-loop feedback ensures consistent efficiency across different sample variations.
Solution Approach 2:
The patent dynamically adjusts the DC link voltage parameter based on detected operating conditions and determined frequency regions. By changing this key parameter in response to actual performance data rather than relying on fixed design values, the system maintains optimal efficiency despite manufacturing tolerances in resonance tank elements.
2Adaptability or versatility
If the LLC converter operates away from resonance frequency due to element errors, then the system can tolerate manufacturing variations, but efficiency decreases and charging time increases
Solution Approach 1:
The system uses feedback from timing measurements to detect deviations from resonance frequency and automatically adjusts operating parameters to return to optimal efficiency, thereby maintaining high productivity despite manufacturing variations in resonance tank elements.
Solution Approach 2:
The patent transitions from a static DC link voltage map based on design values to a dynamic control system that continuously adapts the operating voltage based on actual resonance frequency detection. This dynamic adjustment maintains peak efficiency across varying operating conditions and sample variations.
3Loss of energy
If the DC link voltage is controlled to maintain resonance frequency operation, then efficiency is improved, but the system complexity increases due to additional detection and control mechanisms
Solution Approach 1:
The system performs self-diagnosis and self-adjustment by detecting its own resonance frequency through timing measurements of existing switching and diode operations, then autonomously adjusts the DC link voltage to maintain optimal operation without requiring external calibration or complex additional hardware.
Solution Approach 2:
The patent makes existing timing measurement circuits serve dual purposes: their original function plus resonance frequency detection. By utilizing existing operational data for multiple functions, the system achieves sophisticated control without proportionally increasing hardware complexity.
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 improves the efficiency of the OBC, reduces efficiency differences between samples, and enhances the electric efficiency of the vehicle by maintaining optimal LLC converter operation, thereby reducing charging time and improving overall system quality.
Implementation Method 1
The LLC converter reaches maximum efficiency when the resonant tank operates at a resonance frequency fo
Data Source
AI summary
A method of controlling an on-board charger (OBC) and an OBC system are capable of improving efficiency of the OBC by controlling a DC link voltage such that a DC-DC LLC converter of an ecofriendly vehicle always operates at a resonance frequency. The method includes: detecting a switching turn-on time of a switching unit and a conduction time of a diode, comparing the switching turn-on time with the conduction time, comparing a point of time when the switching unit is turned on with a point of time when the diode becomes conductive, determining an operating frequency region of the switching unit, and controlling a voltage of an input terminal of the LLC converter such that a switching frequency of the switching unit is in a resonance frequency region of the LLC converter according to the determined operating frequency region.