LED Display Panel Drive Method Using Multi-Level PWM
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Solution Overview
Problem
Existing LED drive modes for outdoor LED display panels suffer from nonlinear lighting output, leading to unstable illumination and reduced luminous efficiency, particularly in switch pulse width modulation modes.
Innovation Solution
A multi-level pulse width modulation drive method is implemented, where a FPGA controller converts HDMI/DVI signals into RGB signals, divides them into independent code streams, and uses parallel LED drive modules to periodically switch between two direct currents, adjusting the duty cycle to maintain a constant average current, enhancing luminous efficiency while enabling linear dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If switch pulse width modulation mode is used to drive LED array, then the illumination output can be adjusted linearly by adjusting duty cycle, but the luminous efficiency of LED is reduced
Solution Approach 1:
The patent applies periodic switching of direct currents to drive the LED array. By periodically switching between high level DC current and low level DC current (multi-level PWM), the system achieves both linear dimming control through duty cycle adjustment and maintains higher luminous efficiency compared to traditional single-level PWM by keeping the LED continuously conducting
Solution Approach 2:
The patent changes the driving parameters by using multiple current levels (high level DC current and low level DC current) instead of traditional binary PWM switching. This parameter change allows the LED to operate in a more efficient conduction state while still achieving linear dimming through duty cycle control of the periodic switching
2Loss of energy
If analog or direct current drive mode is used to drive LED array, then the luminous efficiency is highest and color stability is optimal, but the illumination output varies nonlinearly and cannot dim linearly
Solution Approach 1:
The patent introduces periodic switching of direct currents (multi-level PWM) to maintain the continuous conduction state of LED while enabling linear dimming control. This periodic action allows the system to retain the high luminous efficiency of DC drive mode while adding the linear dimming capability through duty cycle adjustment of the periodic switching between high and low current levels
3Ease of operation
If traditional PWM mode switches between zero current and high current, then linear dimming is achieved, but the LED operates in discontinuous conduction mode reducing luminous efficiency
Solution Approach 1:
The patent uses periodic switching between multiple direct current levels (high level and low level) rather than switching between high current and zero current. This multi-level periodic switching maintains continuous LED conduction while enabling linear dimming through duty cycle control, thereby improving luminous efficiency compared to traditional discontinuous conduction PWM
Solution Approach 2:
The patent dynamically switches between multiple current levels (high level DC current and low level DC current) in a periodic manner. This dynamic multi-level switching allows the LED to maintain continuous conduction state for higher efficiency while still achieving linear dimming control through adjustable duty cycles of the periodic switching
Data Source
AI summary
A drive method and system for an LED display panel. The method comprises: converting an HDMI/DVI video signal into an RGB signal; dividing the RGB signal into N independent code streams and re-ranking same; and periodically switching a direct current provided to an LED display module (30) at least between a first current I1 and a second current I2. The system comprises an FPGA controller (20), and a video signal decoder (10), a first external memory (41), a second external memory (42) and an LED display module (30) which are respectively connected to the FPGA controller (20). The FPGA controller (20) comprises N LED drive modules (231-23N) which are connected in parallel. The drive method and system can enhance the luminous efficacy of an LED, and can also conduct linear dimming on the LED.