Current Control Circuit for Hot-Swap Inrush Management
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Solution Overview
Problem
Current current control circuits face challenges in managing inrush currents during hot-swapping and power line disturbances, leading to power dissipation issues and noise generation, particularly with large power FETs and switch mode control methods.
Innovation Solution
A current control circuit with a switching means providing controllable resistance, using a processing means to select between linear and switch mode operations based on detected states, keeping output current below a threshold and controlling switching to minimize power dissipation and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear mode control is used with power FET to provide load current slew rate control and peak current limiting, then current control during hot-swap is improved, but power dissipation increases and large expensive power FETs are needed
Solution Approach 1:
The patent implements dynamic mode selection that automatically switches between linear mode and switch mode control based on real-time detection of circuit state (hot-swap condition vs. normal operation). This dynamic adaptation allows the system to use linear mode only when necessary for hot-swap protection, while using switch mode for normal operation, thereby reducing overall power dissipation while maintaining current control reliability during hot-swap events
Solution Approach 2:
The patent changes the operating parameters of the power FET by switching between two distinct control modes: linear mode (with high duty cycle and controlled slew rate) for hot-swap conditions, and switch mode (with pulsed operation and lower average current) for normal operation. This parameter change allows the same power FET to operate efficiently under different conditions, reducing the need for oversized devices
2Loss of energy
If switch mode control is used to decrease transistor power losses, then power dissipation is reduced, but large amount of conducted or radiated noise is generated
Solution Approach 1:
The patent applies different control qualities to different operational contexts: switch mode control (with its noise characteristics) is used for normal operation where power efficiency is paramount, while linear mode control (with its smoother current profile) is used for hot-swap conditions. The system locally adapts the control quality based on the specific operational requirement, balancing noise and power trade-offs
3Reliability
If large power FETs are used to stay within safe operating area during large disturbances, then reliability is improved, but device size and cost increase
Solution Approach 1:
The patent uses dynamic mode selection to adapt the power FET's operating characteristics in real-time. During hot-swap events, linear mode provides controlled current slew rate that keeps the FET within safe operating area. During normal operation, switch mode reduces average current stress. This dynamic operation allows the use of smaller, less expensive power FETs while maintaining reliability across all conditions
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 solution reduces maximum power dissipation in power FETs and minimizes noise generation, effectively managing inrush currents and power line disturbances while maintaining system uptime.
Implementation Method 1
a switching means (104) connected to the input terminal (101) via a current detection means (105), and to an output terminal (102) via an output circuit (107), wherein the switching means (104) is configured to provide a controllable resistance
Data Source
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Figure 5a~5d
AI summary
A method and a current control circuit 100 therefor. The method for a current control circuit 100 comprising determining 201 a state of the current control circuit 100, select 202 a first mode of operation 203 if the determined state is a first state indicative of a hot plug-in of the input terminal 101 to a connectable DC voltage bus. The method further comprises selecting 202 a second mode of operation 204 if the determined state is a second state different from the first state. The method further comprises controlling 205 the output current using the selected mode of operation.