Backlight Driving Circuit Multiplexing for High Brightness
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Solution Overview
Problem
Conventional backlight driving methods require a large number of LED driving circuits, leading to increased cost and PCB size, and are not suitable for small-size products, especially in AR & VR applications where high instantaneous brightness is needed to prevent dizziness caused by liquid crystal deflection.
Innovation Solution
A backlight driving circuit that includes a control sub-circuit, a selection sub-circuit with multiplexers (MUXs), and a driving sub-circuit, which reduces the number of driving sub-circuits by multiplexing the turning-on of rows of light sources using timing voltage signals with preset delays, allowing for efficient control of light source arrays with fewer driver ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a direct type backlight is adopted to improve working currents of LEDs, then brightness is improved, but device complexity and cost increase
Solution Approach 1:
The backlight is divided into multiple light source arrays with rows and columns of LED light sources. The selection sub-circuit selectively activates specific rows based on timing voltage signals, segmenting the backlight control into manageable units that can be independently controlled to achieve high brightness without requiring all LEDs to be driven at maximum current simultaneously.
Solution Approach 2:
The patent employs sequential row activation using timing voltage signals with different delays. Each row is activated in a periodic sequence controlled by the control sub-circuit, allowing the backlight to achieve high instantaneous brightness during active periods while maintaining lower average power consumption and reduced complexity compared to driving all LEDs continuously at high current.
2Illumination intensity
If working current of LEDs is increased to improve brightness, then illumination intensity is improved, but power consumption increases
Solution Approach 1:
The control sub-circuit activates different rows of light sources sequentially using timing voltage signals rather than continuously driving all LEDs. This periodic activation allows individual rows to receive higher current for bright illumination during their active period, while the overall power consumption is reduced because not all LEDs are active simultaneously.
Solution Approach 2:
The control sub-circuit outputs timing voltage signals with preset delays before activating each row, preparing the selection sub-circuit to switch between rows in advance. This preliminary timing control ensures that high current is applied only when needed for brightness, rather than continuously, thereby reducing overall power consumption.
3Illumination intensity
If a large number of LED driving circuits are used, then brightness control is improved, but PCB size increases
Solution Approach 1:
The selection sub-circuit uses multiplexers that can selectively connect different rows of light sources to the driving circuits. This multi-functional approach allows a smaller number of driver ICs to control a larger number of LED rows by time-multiplexing the connections, reducing the PCB area required compared to having dedicated driving circuits for each LED or LED group.
Solution Approach 2:
The patent introduces a time dimension to the control architecture by sequentially activating different rows over time. This temporal multiplexing allows the system to control many more light sources than the number of physical driver ICs, effectively adding a time-based dimension to the control space and reducing the spatial requirements on the PCB.
4Ease of manufacture
If conventional backlight driving methods are used, then cost is reduced, but adaptability to small-size products decreases
Solution Approach 1:
The backlight is segmented into multiple rows that can be independently controlled through the selection sub-circuit. This segmentation allows the system to be configured for different sizes and applications by selectively activating appropriate rows, making it adaptable to small-size products like AR/VR headsets while maintaining cost-effectiveness through shared driving circuits.
Solution Approach 2:
The driving circuit architecture is designed to be universal and scalable. The same basic structure of control sub-circuit, selection sub-circuit with multiplexers, and driving sub-circuit can be applied to various product sizes by adjusting the number of rows and columns. This multi-functionality allows cost-effective implementation across different product form factors including small-size applications.
Data Source
AI summary
The present disclosure relates to a backlight driving circuit, a backlight driving method, a backlight device and a display device. A backlight driving circuit for driving a light source array, comprising: a control sub-circuit for outputting a control signal and different timing voltage signals; a driving sub-circuit for providing data signals to the light source array according to the control signal; and a selection sub-circuit that corresponds to rows in the light source array, wherein the selection sub-circuit is configured to control the turning-on of light sources of the corresponding rows in the light source array according to the timing voltage signals outputted by the control sub-circuit.