Vehicle Battery Charging Circuit for Solar-Only Auxiliary Charging
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Solution Overview
Problem
Conventional solar cell systems for eco-friendly vehicles often lead to resonance issues with FET-side parasitic capacitors and transformers, causing continuous charging of OBC link capacitors, which reduces efficiency and may result in overcharge problems, necessitating the use of relays that further degrade efficiency.
Innovation Solution
A vehicle battery charging system incorporating an integrated converter with a common transformer and power factor correction device, along with a switching device that connects the solar cell only during auxiliary battery charging, preventing link capacitor overcharge by generating a discharge path through the solar cell converter and utilizing a solar loop power structure to optimize efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay is used to prevent link capacitor overcharge, then the overcharge problem is solved, but OBC efficiency decreases
Solution Approach 1:
The patent extracts and removes the relay component from the system by implementing a control method that uses the existing switching device to create a discharge path for the link capacitor. This eliminates the need for additional protective components while maintaining overcharge prevention functionality.
Solution Approach 2:
The switching device is made multi-functional by enabling it to perform both its primary function of switching between integrated converter and external power/solar cell, and an additional function of creating a discharge path for the link capacitor during solar cell charging mode. This universal approach eliminates the need for dedicated protective relays.
2Productivity
If conventional solar cell system is used, then solar cell can charge auxiliary battery, but resonance occurs causing link capacitor continuous charging
Solution Approach 1:
The patent applies preliminary anti-action by proactively creating a discharge path for the link capacitor before overcharge conditions develop. The control method detects solar cell charging mode and immediately activates the discharge path through the switching device, preventing resonance-induced overcharge before it occurs.
Solution Approach 2:
The switching device acts as an intermediary element that mediates between the solar cell converter and the link capacitor. By controlling the switching device to create a discharge path, the system safely dissipates excess energy from the link capacitor during solar cell charging, preventing harmful resonance effects.
3Loss of energy
If integrated converter structure is used, then power conversion efficiency is improved, but link voltage overcharge problem occurs due to transformer structure
Solution Approach 1:
The patent implements feedback control by continuously monitoring the charging mode and link capacitor voltage status. When solar cell charging mode is detected, the control method activates the discharge path through the switching device, creating a feedback loop that maintains link voltage within safe operating limits while preserving the integrated converter's efficiency benefits.
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
Prevents link capacitor overcharge without degrading OBC efficiency, reduces the need for additional relays, and optimizes solar cell charging converter efficiency, thereby enhancing overall system performance and reducing costs and weight.
Implementation Method 1
a solar cell that converts sunlight into electrical energy
Implementation Method 2
resonance of an FET-side parasitic capacitor of an OBC output terminal and a transformer inductor may occur
Data Source
AI summary
A vehicle battery charging system includes a main battery, an auxiliary battery, an integrated converter that includes a high voltage charging device that supplies power to the main battery and a low voltage charging device that supplies power to the auxiliary battery, a solar cell that converts sunlight into electrical energy, a solar cell converter that converts an output of the solar cell into a voltage corresponding to a voltage of the auxiliary battery and outputs the converted voltage to the auxiliary battery, and a switching device that switches between the integrated converter and external power and the integrated converter and the solar cell, wherein the switching device connects the integrated converter and the solar cell in a solar cell only charging mode in which the auxiliary battery is charged by the solar cell.