LED Backlight Driving Circuit Voltage Equalization
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Solution Overview
Problem
Existing LED backlight drivers for LCDs face inefficiencies due to voltage differences between LED strings, leading to increased temperature and reduced power supply efficiency, as they require constant current control to maintain consistent brightness across strings.
Innovation Solution
A method and circuit that regulate the current and duty cycle of each LED string to equalize voltages and ensure consistent brightness, using a current regulation module and duty-cycle regulation module to adjust currents and duty cycles, allowing for real-time power supply adjustments and switching to constant-current control when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current control is used to ensure consistent LED brightness across strings, then LED brightness consistency is improved, but voltage differences between LED strings cause increased temperature and reduced power supply efficiency
Solution Approach 1:
The patent applies local quality by allowing different current values for different LED strings based on their individual voltage characteristics. Instead of forcing uniform current across all strings, each string receives customized current control tailored to its specific electrical properties, thereby eliminating unnecessary energy loss while maintaining brightness consistency through duty cycle adjustment.
Solution Approach 2:
The patent changes the control parameters from uniform constant current to differentiated current values combined with duty cycle modulation. By adjusting both the current magnitude and duty cycle for each LED string according to its voltage characteristics, the system achieves brightness consistency without the energy waste associated with forcing uniform current across strings with different voltage requirements.
2Reliability
If uniform current is applied to all LED strings, then LED brightness consistency is maintained, but voltage differences cause increased temperature in the constant-current control circuit
Solution Approach 1:
The patent implements local quality by assigning different current values to different LED strings based on their individual voltage characteristics. This localized current control eliminates the need for the constant-current control circuit to compensate for voltage differences, thereby reducing the temperature rise in the control circuit while still achieving consistent LED brightness through duty cycle adjustment.
3Loss of energy
If differentiated current control is used for each LED string to compensate voltage differences, then power supply efficiency is improved, but system complexity increases
Solution Approach 1:
The patent applies universality by using a single control circuit that performs multiple functions: it detects voltage differences, determines appropriate current values, and adjusts duty cycles for each LED string. This multi-functional approach achieves differentiated current control and brightness consistency without requiring separate complex control circuits for each LED string, thereby limiting the increase in system complexity.
Solution Approach 2:
The patent employs feedback mechanisms where the control circuit continuously monitors voltage differences between LED strings and automatically adjusts current values and duty cycles accordingly. This closed-loop feedback control enables automatic compensation for voltage variations without requiring manual intervention or complex external control systems, thereby achieving improved power efficiency with manageable system complexity.
Data Source
AI summary
The present invention discloses a LED backlight driving method, a LCD device and a LED backlight driving circuit, wherein the LED backlight driving method comprises the following steps: regulating the current of each LED string so that the voltages of all LED strings are equal; and regulating the duty cycle of the current of the corresponding LED string so that the effective value of the current of each LED string meets the preset requirement of brightness. The present invention solves the problem of consumption caused by voltage difference by regulating the current through the current regulation module to ensure that the voltages of all the LED strings are equal, and ensures the brightness consistency by regulating the duty cycle through the duty-cycle regulation module so that the effective value of the currents of all the LED strings are equal.