Battery Current Limiting Circuit Using MOSFETs and an Inductor
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Solution Overview
Problem
Current battery technologies face challenges in managing inrush and outrush currents, which can lead to system failures, damage, and reduced performance due to the lack of effective current limiting mechanisms, particularly in electric vehicles with high-voltage batteries and capacitive loads.
Innovation Solution
The implementation of a circuit apparatus comprising a battery, a resistive load, a switch (MOSFETs), an inductor, and a control circuit that regulates the switch based on voltage across the resistor to control current flow, using a comparator and gate driver to manage inrush and outrush currents by opening or closing the switch when voltage thresholds are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limiting mechanism is implemented using traditional circuit breakers or fuses, then inrush and outrush currents are limited, but system complexity and cost increase
Solution Approach 1:
The patent replaces mechanical current limiting devices (circuit breakers, fuses) with an electronic control system using MOSFETs, inductors, and control circuits. This substitution eliminates mechanical moving parts and complex trip mechanisms while achieving current limiting through electronic switching controlled by voltage detection across a sense resistor.
Solution Approach 2:
The patent changes the operating parameters of the MOSFET switch by dynamically adjusting its on/off state based on detected voltage thresholds. The control circuit monitors voltage across the sense resistor and switches the MOSFET on when voltage is below a threshold and off when it exceeds the threshold, thereby controlling current flow without mechanical intervention.
2Device complexity
If no current limiting mechanism is used, then device complexity is reduced, but inrush and outrush currents cause system failures and damage
Solution Approach 1:
The patent introduces a sense resistor as an intermediary element that enables current monitoring without significantly impacting the main current path. By placing a small resistor in series and monitoring the voltage drop across it, the system can detect current levels and trigger the MOSFET switch to limit inrush and outrush currents while maintaining overall circuit simplicity.
Solution Approach 2:
The control circuit is configured to detect voltage thresholds in advance and preemptively switch the MOSFET on or off to prevent harmful current spikes. When voltage across the sense resistor approaches the threshold, the control circuit prepares to switch, thereby preventing inrush or outrush currents before they can cause damage.
3Device complexity
If a simple resistive limit is used for current control, then circuit complexity is minimized, but current ripple and performance are degraded
Solution Approach 1:
The patent transforms the static resistive current limiting into a dynamic control system using a MOSFET switch controlled by voltage detection. The system dynamically adjusts current flow by switching the MOSFET on and off based on real-time voltage measurements across the sense resistor, thereby maintaining low complexity while significantly improving current control performance and reducing ripple.
Solution Approach 2:
The control circuit implements periodic switching of the MOSFET based on voltage threshold detection. By continuously monitoring the voltage across the sense resistor and switching the MOSFET at appropriate intervals, the system achieves smooth current control with reduced ripple, outperforming simple resistive limiting while maintaining circuit simplicity.
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 solution effectively limits inrush and outrush currents, preventing system failures and damage, while reducing complexity and cost, and allowing for safe operation even with reduced-capacity parallel groups by ensuring controlled current flow and ripple reduction.
Implementation Method 1
an inductor; wherein the switch, the resistor, and the inductor are coupled in series between the battery and the resistive load
Implementation Method 2
a switch comprising a first transistor and a second transistor... the first transistor is a first MOSFET; and the second transistor is a second MOSFET
Implementation Method 3
a resistor; wherein the switch, the resistor, and the inductor are coupled in series between the battery and the resistive load
Data Source
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AI summary
The present application relates to an apparatus (200) capable of limiting discharge currents from a battery. The apparatus comprises: a battery (202); a resistive load (204); a switch (208) comprising a first transistor (F2) and a second transistor (F3); a resistor (R4); an inductor (L3); and a control circuit (GD2); wherein the switch, the resistor, and the inductor are coupled in series between the battery and the resistive load; and wherein the control circuit controls the switch based on a voltage across the resistor.