Backlight Driving Circuit Voltage Balancing for LCD Modules
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Solution Overview
Problem
In LCD devices with LED backlight modules, the unequal voltages across multiple LED lightbars cause temperature increases in the control IC of the backlight drive converter, necessitating costly thermal management solutions like thermal pads or bare copper.
Innovation Solution
A backlight driving circuit with LED lightbars in parallel connection, each coupled with a variable current circuit containing adjustable resistors to balance voltage differences, and an isolating switch to prevent damage from short circuits, reducing voltage differences applied to the control IC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LED lightbars are connected in parallel with a common converter, then the backlight module can provide sufficient illumination, but the voltage differences among LED lightbars cause current generation and temperature increase in the control IC
Solution Approach 1:
The patent divides the backlight system into independent drive circuits, with each LED lightbar having its own dedicated drive circuit instead of sharing a common converter. This segmentation isolates the voltage differences to individual circuits, preventing current generation between lightbars and reducing heat accumulation in the control IC.
2Temperature
If thermal pads or bare copper are added to the converter to solve temperature problems, then the control IC temperature can be reduced, but the manufacturing cost increases
Solution Approach 1:
The patent extracts the temperature problem source by separating each LED lightbar into its own drive circuit, eliminating the need for thermal management components like thermal pads or bare copper. This extraction approach solves the heating issue at its source rather than adding corrective components, thereby reducing manufacturing cost.
3Temperature
If variable resistors are added to balance voltage differences, then the control IC temperature can be reduced, but the device complexity increases
Solution Approach 1:
The patent employs adjustable variable resistors in each drive circuit that can be dynamically tuned to match the specific voltage characteristics of each LED lightbar. This dynamic adjustment capability allows the system to adapt to voltage variations without requiring complex control logic or multiple fixed resistor combinations, thereby managing complexity effectively.
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 configuration maintains consistent voltages across the control IC, reducing power consumption and heat production, thereby lowering the temperature of the control IC and minimizing energy consumption.
Implementation Method 1
the variable current circuit is provided with adjustable variable resistors used for balancing the voltage difference between the LED lightbars
Implementation Method 2
when the LED lightbar(s) is short-circuited, the isolating switch is disconnected, thereby preventing all the branch voltages from being applied onto the control IC
Data Source
AI summary
The invention provides a backlight driving circuit, an LCD device, and a manufacturing method thereof. The backlight driving circuit includes at least two LED lightbars arranged in parallel connection, the output end of each of the LED lightbars is coupled with a variable current circuit, and the variable current circuit is provided with adjustable variable resistors used for balancing the voltage difference between the LED lightbars. In the invention, because the adjustable variable resistors are arranged in the variable current circuit which is connected in series with the LED lightbars, the resistance of the adjustable variable resistors can be adjusted according to the resistance of different LED lightbars before being used; thus, the total voltage of each LED lightbar and the variable resistor connected with ed LED lightbars in series can keep consistent. Therefore, the voltages of all the pins of the control IC coupled into the driver converter can be consistent, and no additional current can be generated in the control IC because no voltage differences exist between pins basically; thus, the power consumption of the control IC is reduced, and the heat productivity of the control IC is reduced, thereby reducing the temperature of the control IC.