MOSFET Inrush Current Limiter for Low-Voltage EMC Operation
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Solution Overview
Problem
Conventional inrush current limiters designed for high voltage systems malfunction when the supply voltage is lowered below a certain level, leading to erroneous operations during electromagnetic compatibility (EMC) tests.
Innovation Solution
An inrush current limiter that includes a transistor with a gate driver and feedback portion, along with a mode controller, to gradually increase the voltage and stabilize it, ensuring normal operation across a wide voltage range, including during EMC tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional inrush current limiter designed for high voltage systems is used, then it can effectively limit inrush current at high voltages, but it causes erroneous operation when the supply voltage is lowered below a certain level
Solution Approach 1:
The patent implements dynamic operation mode switching based on voltage levels. The mode controller detects the input voltage level and dynamically switches between a first operation mode (for high voltage normal operation) and a second operation mode (for low voltage EMC test conditions). This dynamic adaptation allows the inrush current limiter to maintain reliability across the full voltage range from 7V to 58.5V, resolving the contradiction between high-voltage effectiveness and low-voltage operational failure.
Solution Approach 2:
The patent changes the operational parameters of the inrush current limiting circuit based on voltage conditions. By detecting voltage levels and switching operation modes, the circuit adjusts its behavior to suit different voltage environments. This parameter change approach enables the circuit to operate reliably both at high voltages during normal operation and at low voltages during EMC testing, expanding the operation voltage range while maintaining reliability.
2Reliability
If the inrush current limiter operates in a fixed high voltage mode, then it provides stable current limiting at high voltages, but it cannot function properly during EMC tests with lowered supply voltage
Solution Approach 1:
The patent employs dynamic mode switching to adapt the current limiting characteristics to the operating voltage. The mode controller continuously monitors the input voltage and switches between operation modes to maintain stable current limiting across the full voltage range. This dynamic adjustment ensures that the circuit provides reliable current limiting both at high voltages during normal operation and at low voltages during EMC tests, resolving the contradiction between stability and adaptability.
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
The proposed solution improves the operational voltage range of the inrush current limiting circuit, enabling normal system operation even in EMC test environments by preventing sudden current fluctuations and ensuring reliable transistor turn-on at lower voltages.
Implementation Method 1
The gate driver may include a first resistor connected in parallel between the source and gate of the transistor, and a first capacitor
Implementation Method 2
The gate driver may further include a Zener diode that is connected between the source and gate of the transistor and limits a voltage between the source and gate of the transistor
Implementation Method 3
The mode controller may include a comparator, wherein the comparator may include: a first input terminal to which a comparison voltage corresponding to the input voltage is input, a second input terminal to which a reference voltage is input, and an output terminal that outputs an output signal corresponding to a comparison result of voltages input through the first and second input terminals
Implementation Method 4
The mode controller may include a fourth resistor and a fifth resistor that are connected in series, and may further include a voltage divider circuit that outputs the comparison voltage divided from the input voltage to the first input terminal
Data Source
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AI summary
Exemplary embodiments of the present invention relate to an inrush current limiter and a system including the same. The inrush current limiter includes: a first input node and a second input node that receive an input voltage from a power source; a first output node and a second output node that are connected with a load; an inrush current limiting portion that includes a transistor connected between the first input node and the first output node, and turns on the transistor when a voltage level of the input voltage is higher than a first level and limits an inrush current by controlling time until the transistor is turned on after application of the input voltage; a switch that is connected between a control terminal of the transistor and the second input node; and a mode controller that turns on the switch when the voltage level of the input voltage is lower than a second level that is lower than the first level.