Variable Link Voltage Charging Apparatus for Battery Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing charging apparatuses for electric vehicles have inefficiencies in charging direct current batteries from alternating current power supplies, particularly in achieving high input power for rapid charging and maintaining efficiency across varying battery voltages.
Innovation Solution
A charging apparatus with a first converter unit for direct current voltage conversion and a second converter unit that operates in two modes: a fixed voltage mode for a predetermined time and a variable voltage mode increasing to the charge completion voltage, optimizing the link voltage and switching operations to maintain efficiency and reduce losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a resonant DC-DC converter is used to charge the battery, then conversion efficiency is improved, but the current capacity becomes large when charging at maximum power with low battery voltage
Solution Approach 1:
The patent applies dynamics by making the input voltage to the resonant DC-DC converter variable rather than fixed. The voltage is dynamically adjusted based on the battery charging state: a first voltage is applied initially, then switched to a second voltage (higher than the first) when the battery voltage reaches a predetermined threshold. This dynamic voltage adjustment allows the system to maintain high conversion efficiency while reducing the current capacity requirement of the resonant converter, thereby resolving the technical contradiction between efficiency and power handling capability.
2Device complexity
If a fixed input voltage is applied to the resonant DC-DC converter, then the converter design is simplified, but charging efficiency decreases as battery voltage increases
Solution Approach 1:
The patent implements dynamics by transitioning from a fixed input voltage design to a variable input voltage design. The control unit switches between a first voltage (for lower battery voltages) and a second voltage (for higher battery voltages) based on real-time battery voltage detection. This dynamic approach maintains optimal conversion efficiency across the entire charging range while the control logic remains relatively simple, effectively balancing device complexity and charging efficiency.
Solution Approach 2:
The patent applies parameter changes by modifying the input voltage parameter of the resonant DC-DC converter based on the battery charging state. When the battery voltage reaches a predetermined value, the input voltage parameter is changed from the first voltage to the second voltage (which is higher). This parameter adjustment ensures that the converter operates at optimal efficiency points throughout the charging process, resolving the contradiction between simplified design and maintained efficiency.
3Productivity
If maximum input power is used for charging, then charging time is reduced, but the current capacity requirement increases when battery voltage is low
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the input voltage to the resonant DC-DC converter based on the battery voltage level. During early charging when battery voltage is low, a first voltage is applied. When battery voltage reaches a predetermined threshold, the input voltage is dynamically increased to a second voltage. This dynamic adjustment enables the system to deliver maximum charging power throughout the process while avoiding excessive current capacity requirements in the resonant converter, thereby achieving fast charging without proportionally increasing converter complexity and cost.
Data Source
AI summary
An object of the present invention is to provide a charging apparatus having high efficiency of charging a battery by inputting an alternating current voltage. A charging apparatus that charges a direct current battery includes a step-down converter unit to which a direct current voltage from a power supply is input and that converts the direct current voltage, and when a voltage of the direct current battery is between a predetermined first voltage smaller than a charge completion voltage of the direct current battery and the charge completion voltage, a variable voltage that increases from the first voltage to the charge completion voltage in accordance with charging of the direct current battery is input to the step-down converter unit.