Inductive Current Limiting for Battery Charging Circuits
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Solution Overview
Problem
Existing charging circuits for loads with low internal resistance, such as batteries, often require expensive and bulky resistors to manage current, which are sensitive to variations and have limited pre-charge attempts before overheating, making them inefficient and prone to failure.
Innovation Solution
A charging circuit utilizing an inductance instead of a resistor to limit current, with a switch and diode to control current flow, and a control circuit to manage switching based on current and voltage sensors to maintain optimal operation and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a resistor is used to limit current during charging, then the current is limited to safe levels, but the resistor is bulky, expensive, and dissipates energy as heat
Solution Approach 1:
The patent changes the fundamental parameter from resistive current limiting to inductive current limiting. By using an inductor instead of a resistor, the current limiting mechanism changes from dissipative (I²R losses) to reactive (energy storage in magnetic field), fundamentally altering how energy is handled in the circuit while maintaining current protection functionality
Solution Approach 2:
The patent converts the harmful effect of high inrush current into a beneficial controlled charging process. The inductor's natural property of opposing current changes is used to gently limit current, while the stored magnetic energy is later converted to useful charging current, turning what would be waste heat into useful energy delivery
2Productivity
If a resistor is used for pre-charging, then current is limited, but the resistor overheats after limited pre-charge attempts
Solution Approach 1:
The patent changes the thermal parameter behavior by replacing the resistive element with an inductive element. The inductor does not convert electrical energy to heat in the same way a resistor does, eliminating the overheating problem while maintaining the ability to control charging current for rapid charging
Solution Approach 2:
The patent converts the potential harm of excessive current (which would cause overheating) into a controlled energy storage process. The inductor stores energy in its magnetic field during the charging phase, and this stored energy is then released to continue charging the load, turning what would be thermal damage into productive energy transfer
3Reliability
If switched charging with relay and resistor is used, then current is limited, but the circuit becomes sensitive to variations and requires component matching
Solution Approach 1:
The patent makes the inductor serve multiple functions: it limits inrush current, stores energy during the charging cycle, and provides continuous current to the load. This multi-functionality eliminates the need for separate resistors and relays, simplifying the circuit while improving robustness against component variations
Solution Approach 2:
The patent extracts and eliminates the unnecessary resistor and relay components from the circuit. By using only the inductor for current limiting and energy storage, the circuit becomes simpler with fewer components that could vary or fail, while maintaining all necessary protective and charging functions
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 efficiently limits current to prevent overheating, allows for faster charging while maintaining current within safe levels, and reduces energy dissipation, enhancing the circuit's efficiency and longevity.
Implementation Method 1
a connecting element comprising a first inductance connector and a second inductance connector for connecting an inductance
Implementation Method 2
a diode element connected to the first inductance connector and the second output terminal such that when the first switch is switched on, current flowing through the switch is prevent from flowing from the switch to the second output terminal via the diode element
Data Source
AI summary
A charging circuit includes first and second input terminals connecting the circuit to first and second supply terminals, respectively, of a DC power source, first and second output terminals providing an output voltage to a load to be charged, a first switch between the first and second input terminals, a current sensor between the first input terminal and the first output terminal in series with the first switch, a connecting element having first and second inductance connectors for connecting an inductance, the first inductance connector connected to the switch and the second inductance connector connected to the first output terminal, and a diode element connected to the first inductance connector and the second output terminal. The first switch and the current sensor are arranged to be connected to a control circuit arranged for controlling operation of the first switch in response to a signal received from the current sensor.