PWM Current Control Apparatus for Lithium Battery Charging
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Solution Overview
Problem
The existing rectifiers lack a current control function, making it difficult to safely replace lead storage batteries with lithium secondary batteries in applications like electric vehicles, due to the high current flow during charging, which can lead to battery failure.
Innovation Solution
A current control apparatus that generates a pulse width modulation (PWM) signal to control a P-channel field effect transistor (FET), reducing the current value and preventing sudden high current flow from the rectifier to the battery, using a switch control signal and a buck converter to smooth the current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rectifier is used to charge a lithium secondary battery, then charging capability is provided, but large current suddenly flows to the battery causing battery failure
Solution Approach 1:
The current control apparatus is activated before charging begins to gradually increase the current from zero to the target charging current. This preliminary action prevents sudden current surge that would otherwise damage the battery, while still enabling full charging capability to be achieved.
Solution Approach 2:
The current control apparatus acts as an intermediary device between the rectifier and the lithium secondary battery. It controls the P-channel FET to regulate current flow, serving as a protective mediator that prevents direct connection of high current to the battery while maintaining charging functionality.
2Use of energy by moving object
If lead storage battery is replaced with lithium secondary battery, then energy efficiency is improved, but current control function is required which existing rectifier lacks
Solution Approach 1:
The current control apparatus integrates multiple functions including current regulation, battery protection, and charging control into a single device. This multi-functional design provides the necessary current control capability for lithium batteries while maintaining compatibility with existing rectifier systems, making the replacement feasible without completely redesigning the charging infrastructure.
3Quantity of substance
If multiple batteries are connected in parallel for high capacity, then capacity is increased, but current control becomes difficult
Solution Approach 1:
The current control apparatus independently controls the current distribution to each battery connected in parallel. By segmenting the current control function for each battery string, the system can manage multiple high-capacity batteries without the current control complexity that would otherwise arise from parallel connections.
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
Effectively controls the current flow to the battery, preventing failure and enabling safe replacement of lead storage batteries with lithium secondary batteries, while maintaining high capacity and energy efficiency.
Implementation Method 1
control a P-channel field effect transistor (FET) through a switch control signal corresponding to the PWM signal
Implementation Method 2
decrease a current value of a current passing through the P-channel FET, and provide the current having the decreased current value to a battery
Data Source
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AI summary
Disclosed are an apparatus and a method for controlling electric currents. The apparatus for controlling electric currents according to the present invention includes: a pulse width modulation (PWM) signal generating unit configured to generate a PWM signal; a first switch unit connected with the PWM signal generating unit, and configured to receive the PWM signal and generate a switch control signal corresponding to the PWM signal; a second switch unit connected with the first switch unit, and configured to receive the switch control signal and connect or block a flow of a current from a rectifier to a battery according to the switch control signal; and a current decreasing unit connected with the second switch unit, and configured to decrease a current value of a current passing through the second switch unit and provide the battery with a current having the decreased current value.