Low Cost LED Driver with Serial Bus for Local Dimming
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Solution Overview
Problem
Current LED backlight systems for LCDs and TVs with local dimming capability are costly, complex, and inflexible, requiring numerous discrete components and high-pin-count packages, which lead to overheating and reduced performance.
Innovation Solution
A distributed LED driver system using a serial lighting interface (SLI) bus with integrated current sink MOSFETs and functional latches, eliminating discrete MOSFETs and enabling scalable, low-pin-count packaging, precise current control, and fault detection without a central controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete MOSFETs and high-pin-count packages are used for LED driver circuits, then precise current control and local dimming capability are achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent integrates current sink MOSFETs directly into the LED driver IC, merging previously discrete components into a unified integrated circuit. This consolidation maintains precise current control functionality while reducing overall device complexity and eliminating the need for high-pin-count packages by incorporating power switching elements within the driver chip itself.
Solution Approach 2:
The integrated LED driver IC performs multiple functions including current regulation, pulse control, fault detection, and local dimming coordination through a single device. This multi-functional approach replaces multiple discrete components (MOSFETs, resistors, capacitors, control logic) with a universal integrated solution that handles all backlight control tasks.
2Illumination intensity
If more LED strings are used for local dimming, then display performance and contrast ratio improve, but power dissipation and overheating increase
Solution Approach 1:
The patent implements pulse-width modulation (PWM) control for LED strings, switching them on and off in rapid periodic cycles to achieve desired brightness levels. This periodic switching allows precise control of average power delivery to each LED string, enabling local dimming zones to operate at reduced power consumption while maintaining high contrast ratios through selective illumination of different display regions.
3Device complexity
If integrated LED driver circuits are used, then component count and cost are reduced, but thermal management becomes more challenging
Solution Approach 1:
The patent extracts heat-generating MOSFET functions from external discrete components and integrates them into the LED driver IC. While this reduces component count, it concentrates thermal load within the integrated circuit. The solution addresses this through efficient thermal design of the IC package and heat dissipation pathways, managing the extracted thermal function within the integrated structure.
4Adaptability or versatility
If high-pin-count packages are used for LED drivers, then functionality and control capability are enhanced, but manufacturing cost and assembly complexity increase
Solution Approach 1:
The patent combines multiple control functions and power switching elements into a single integrated LED driver IC with reduced pin count. By merging discrete MOSFETs, control logic, and current regulation circuits into one device, the solution maintains full local dimming control capability while significantly reducing the number of required package pins and simplifying the bill of materials for manufacturing.
Data Source
AI summary
An LED driver IC for driving external strings of LEDs includes a prefix register and a data register connected in series with each other and with the prefix and data registers in other driver ICs. The prefix and data registers of the driver ICs are connected in a daisy chain arrangement with an interface IC. The interface IC loads data identifying a functional latch into the prefix register and data defining a functional condition into the data register of each driver IC. The data in the data register is then transferred to the functional latch to control the functional condition within the LED driver IC.