LED Backlight Driving Circuit Short Circuit Protection
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Solution Overview
Problem
In liquid crystal display (LCD) devices with LED backlights, short circuits in the LED lightbar reduce overall brightness and can damage the constant current chip and related circuit boards due to the inability to switch off the current effectively.
Innovation Solution
An LED backlight driving circuit with a comparison module that monitors the output voltage of the LED lightbar and controls the constant current chip to switch off the current when the voltage exceeds a preset reference voltage, using a comparator and adjustable resistors to implement LED short circuit protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant current chip is used to control the LED lightbar, then the brightness can be adjusted effectively, but the chip cannot switch off the current when LEDs are short-circuited, causing damage
Solution Approach 1:
The patent introduces a comparison module as an intermediary between the LED lightbar and the constant current chip. This module monitors the voltage across the LED lightbar and compares it with a reference voltage, then controls the switch based on the comparison result. When a short circuit occurs, the voltage drops below the reference level, triggering the switch to open and protect the chip, thus resolving the contradiction between ease of brightness control and chip protection reliability.
2Power
If one or more LEDs are short-circuited, then the voltage across the LED lightbar changes, but the constant current chip cannot detect this condition to protect itself
Solution Approach 1:
The patent implements a feedback mechanism where the comparison module continuously monitors the voltage across the LED lightbar and feeds this information back to control the switch. When LEDs are short-circuited, the voltage changes are detected through this feedback loop, and the comparison module responds by adjusting the switch state to protect the constant current chip, thereby solving the detection difficulty.
3Device complexity
If no protection circuit is added, then the circuit remains simple, but LED short circuits can damage the constant current chip and circuit board
Solution Approach 1:
The patent applies preliminary action by pre-configuring the comparison module and switch to automatically respond to short circuit conditions before damage can occur. The comparison module is set up with a reference voltage that triggers protective action when the LED lightbar voltage deviates due to short circuits, enabling preemptive protection without requiring complex additional circuits or manual intervention.
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 damage to the constant current chip and circuit boards by switching off the LED lightbar when a short circuit is detected, maintaining brightness and ensuring user comfort by preventing increased voltage from affecting the backlight module.
Implementation Method 1
a comparison module that receives an output voltage of the LED lightbar. When the output voltage of the LED lightbar is greater than a preset reference voltage, the comparison module controls the constant current chip to switch off the current of the LED lightbar
Data Source
AI summary
A light emitting diode (LED) backlight driving circuit includes an LED lightbar, and a constant current chip that controls current flowing through the LED lightbar. The LED backlight driving circuit further includes a comparison module that receives an output voltage of the LED lightbar. When the output voltage of the LED lightbar is greater than the preset reference voltage, the comparison module controls the constant current chip to switch off the current of the LED lightbar.