Current Limiting MOSFET for LED Backlight Overcurrent Protection
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Solution Overview
Problem
Portable information handling systems with LED backlights lack effective protection and monitoring against overcurrent faults, which can lead to system shutdowns and increased power consumption due to the simplicity of boost regulators compared to CCFL inverters.
Innovation Solution
A current limiting MOSFET is integrated between the power source and the boost regulator to detect and prevent overcurrent events, cutting off power to the LED backlight system and providing a flag to the embedded controller for fault notification, thus offering protection and monitoring without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuse is used to detect overcurrent faults, then fault detection is achieved, but the system is disabled and no feedback is provided
Solution Approach 1:
The patent implements feedback by having the embedded controller receive notifications of backlight faults through the power regulation monitor, allowing the system to detect and report faults without disabling itself. This resolves the contradiction by providing both fault detection and continuous system operation with information feedback.
Solution Approach 2:
The power regulation monitor acts as an intermediary between the backlight circuit and the embedded controller, transferring fault information without requiring the system to shut down. This mediator enables fault detection while maintaining system operation and providing feedback information.
2Reliability
If a switch is integrated in the boost regulator to turn off on overcurrent, then protection is provided, but cost and power consumption increase
Solution Approach 1:
The embedded controller performs the protection function by monitoring current through the power regulation monitor and shutting off power to the backlight when overcurrent is detected. This self-service approach eliminates the need for an expensive, power-consuming switch in the boost regulator while maintaining protection capabilities.
Solution Approach 2:
The embedded controller, which already manages other system functions, is extended to handle backlight overcurrent protection. This multi-functional use of existing components provides protection without adding dedicated expensive components or increasing overall power consumption.
3Reliability
If a switch is integrated in the boost regulator to turn off on overcurrent, then protection is provided, but cost increases
Solution Approach 1:
The embedded controller provides the protection function that would otherwise require a dedicated switch component, eliminating the need for expensive custom switches in the boost regulator. This reduces manufacturing cost while maintaining protection capabilities through software-controlled monitoring and shutdown.
Solution Approach 2:
Instead of using an expensive physical switch component, the system uses a software-based protection mechanism in the embedded controller that replicates the protection function. This virtual copy of the switch functionality achieves the same protective effect at lower cost.
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 provides reliable fault protection and monitoring for LED backlight systems, preventing overcurrent damage, reducing power consumption, and enabling fault reporting, even if the backlight fails, at a lower cost compared to traditional solutions.
Implementation Method 1
A current limiting MOSFET is disposed on the motherboard between the power source and the boost regulator. At a predetermined current limit, the current limiting MOSFET cuts off power to the boost regulator.
Data Source
AI summary
A current limiting MOSFET monitors power applied to a direct current boost regulator that powers an LED backlight to automatically shut off power to the boost regulator if the current exceeds a predetermined amount. An embedded controller interfaces with the current limiting MOSFET for normal control of operation of the boost regulator by turning the MOSFET on and off. An overcurrent alert is communicated from the MOSFET to the embedded controller if the current exceeds the predetermined amount so that the embedded controller shuts off power to the boost regulator and indicates the failure to an end user.