Current Limiting Mechanism for Docking Station Fault Protection

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Solution Overview

Problem

Existing power supply systems for electronic devices, particularly in docking stations, face issues with excessive current draw due to short circuit faults caused by conductive debris, leading to prolonged power pulsing and potential damage to connectors and inrush current control circuits.

Innovation Solution

A current limiting mechanism responsive to power supply output voltage is implemented, disconnecting the docking station from the power supply when a fault is detected, with a threshold current value set below normal charging levels, using a voltage-sensitive entity and FET switches to prevent current flow during faults, and disabling the mechanism when the voltage exceeds a specified value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the over-current shutdown threshold is set high to avoid false shutdowns during normal operation, then the reliability of power supply operation is improved, but the connectors and inrush control circuit components can become damaged by excessive current during fault conditions

Engineering Contradiction:

Improvepower supply operation reliabilityVSAvoidconnector and component damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a preliminary protective action by placing a fuse in series with the power supply output before the docking station. This fuse is specifically selected to blow at a current level below the shutdown threshold, creating a preliminary failure mode that prevents higher current damage to connectors and control circuit components while avoiding false shutdowns during normal operation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the power supply is designed to pulse on and off to detect and respond to faults, then the power supply attempts to protect itself from excessive current, but the pulsing can continue for very long periods when conductive debris causes short circuit faults

Engineering Contradiction:

Improvefault protection responseVSAvoidpower pulsing duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The fuse provides a preliminary, definitive protective action that permanently opens the circuit when excessive current is detected. This preliminary failure mode prevents the power supply from entering prolonged pulsing cycles, as the blown fuse immediately and permanently disconnects the power supply from the docking station, eliminating the need for continuous on-off cycling to detect the fault.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If the inrush control circuit uses power transistors to limit inrush current, then the connectors are protected from pitting during normal operation, but the transistors can overheat and fail when excessive current is drawn during fault conditions

Engineering Contradiction:

Improveconnector pittingVSAvoidpower transistor temperature

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The fuse acts as a preliminary protective element that opens the circuit before excessive current can reach levels that would cause power transistor overheating. By being positioned in series before the inrush control circuit, the fuse creates a fail-safe mechanism that prevents the transistors from being subjected to sustained excessive current conditions that would lead to thermal failure.

Inventive Principle:

Principle #10Preliminary action

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 prevents excessive current flow, reducing the risk of connector damage and prolonged power pulsing, while ensuring safe operation by shutting off the power supply during faults and allowing normal charging currents to flow without interference.

Implementation Method 1

a voltage sensitive current limiting entity operates the first switch device to prevent current flow through the path

Methodology Applied

Scientific EffectVoltage sensitivity detection: Electric Field

Implementation Method 2

A first switch device is located along a current path extending from the power supply to the charging station, to regulate current flow through the path

Methodology Applied

Scientific EffectField effect transistor conductivity control: Conduction (electrical)

Data Source

PatentUS7656628B2Apparatus for providing fault protection in a circuit supplying power to an electronic device

Publication Date: 2010.02.02 TOSHIBA GLOBAL COMMERCE SOLUTIONS HLDG

AI summary

Apparatus is provided to limit the current drawn from a power supply output connected to furnish power to a docking station or electronic device, when a fault connects the output to ground or other docking connection. The power supply is disconnected when such fault is present during power-up. In one embodiment, the apparatus controllably limits current delivered to a docking station and a mobile device connected thereto. The apparatus includes a switch device located along a current path extending between the power supply and docking station, to regulate current flow. A current limiting entity operates the switch device to prevent current flow, when the fault affects the circuit, and current through the path exceeds a pre-specified threshold level. The pre-specified current threshold level can be less than the current level provided to the docking station and mobile device without said fault. A disabling component de-activates the current limiting entity, when current is flowing to the charging station but the current is unaffected by the fault.