Overcurrent Protection Circuit for LED Backlight Modules
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Solution Overview
Problem
Conventional overcurrent protection mechanisms in LED backlight modules fail to prevent power devices from operating at higher than rated power, leading to potential overheating and fire risks due to their reliance on a single maximum current threshold.
Innovation Solution
An overcurrent protection circuit incorporating both peak value and average value overcurrent protection modules, where the peak value module detects voltage at a node connected to a detection resistor and generates a turning-off signal if it exceeds a threshold, and the average value module detects average voltage over a switching period, forming a logic AND with the peak value module to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single maximum current threshold is used for overcurrent protection, then the device complexity is reduced, but the reliability of preventing power device damage deteriorates
Solution Approach 1:
The overcurrent protection function is segmented into two independent protection modules: peak value overcurrent protection module and average value overcurrent protection module. Each module monitors a different aspect of current characteristics (peak vs. average), allowing comprehensive protection without requiring a single complex protection mechanism. This segmentation enables the system to protect against both instantaneous overcurrents and sustained overcurrents that exceed rated power.
2Ease of operation
If the current threshold is set to the maximum current value, then the ease of operation is improved, but the temperature control of power devices deteriorates
Solution Approach 1:
The protection mechanism changes from using a single current threshold parameter to using two distinct parameters: peak current threshold and average current threshold. By monitoring both the peak current (for instantaneous protection) and average current (for sustained power control), the system can prevent power devices from operating beyond their rated power and resulting high temperatures, while maintaining simple threshold-based operation.
3Device complexity
If only peak current detection is used, then the device complexity is reduced, but the prevention of rated power exceedance deteriorates
Solution Approach 1:
The system implements dual feedback mechanisms: peak value feedback through the peak value overcurrent protection module that monitors instantaneous current spikes, and average value feedback through the average value overcurrent protection module that monitors sustained current levels. Both feedback paths independently monitor their respective current characteristics and can trigger protection actions, ensuring comprehensive rated power protection through multiple feedback channels.
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
Effectively prevents the power device from exceeding rated power, thereby preventing overheating and potential fires by ensuring the switch is turned off when either threshold is exceeded, ensuring safe operation of the LED backlight module.
Implementation Method 1
a first end of the switch is electrically connected to a first end of the detection resistor, a second end of the detection resistor is electrically connected to ground
Data Source
AI summary
The present invention discloses an overcurrent protection circuit for a light source driving module and a related backlight module. The overcurrent protection circuit includes an average value overcurrent protection circuit for detecting an average voltage at a node where the switch is connected to the detection resistor and generating the turning-off signal to turn off the switch when the average voltage is larger or equal to a threshold average voltage, wherein the average voltage is formed by an average current of the switch. Through the above-mentioned mechanism, the present invention can prevent the working power of a power device from being larger than its rated power. Therefore, it also prevents the power device from catching a fire due to a potential high temperature.