LED Driver Voltage Clamp for Illumination Uniformity
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Solution Overview
Problem
LED systems in display applications face non-uniformity in illumination due to delays between activations of LEDs, leading to a lack of uniformity, especially in low grayscale conditions, caused by varying driver voltages between activated and deactivated states.
Innovation Solution
Incorporating a voltage clamp in the LED driver system to maintain a constant amplitude difference of the driver voltage between activated and deactivated states, ensuring equal activation times for all LEDs in a column and thus achieving uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sequential activation of LEDs is used to reduce power consumption and enable scanning, then power efficiency is improved, but delays between activations cause non-uniformity in illumination intensity across the display
Solution Approach 1:
The voltage clamp is activated before the LED to pre-establish a constant voltage level at the intermediate node. This preliminary voltage establishment ensures that when the LED activates, it experiences consistent voltage conditions, eliminating delays and non-uniformity in illumination intensity across sequentially activated LEDs
Solution Approach 2:
The voltage clamp maintains a constant voltage level (parameter) at the intermediate node regardless of sequential activation timing. By fixing this voltage parameter, the system eliminates variations in activation timing that cause illumination non-uniformity while preserving sequential activation for power efficiency
2Object-affected harmful factors
If sequential scanning of LED rows is implemented to reduce EMI and improve response time, then EMI emissions are reduced, but delays between row activations cause non-uniformity especially in low grayscale conditions
Solution Approach 1:
The voltage clamp establishes a constant voltage level at the intermediate node before each LED activation in the sequential scanning sequence. This preliminary voltage stabilization ensures that all LEDs across different rows experience identical voltage conditions, eliminating non-uniformity in low grayscale conditions while maintaining the sequential scanning benefits
Solution Approach 2:
The voltage clamp creates an equipotential condition at the intermediate node by maintaining constant voltage regardless of which row is currently being scanned. This equipotential approach ensures that all LEDs in the array experience the same voltage environment, eliminating position-dependent non-uniformity across sequentially activated rows
Data Source
AI summary
One example includes a light-emitting diode (LED) system. The LED system includes an LED array comprising a plurality of LEDs that are each activated via an LED current provided therethrough to provide illumination. The system also includes an LED controller configured to sequentially activate the plurality of LEDs via at least one LED driver system configured to selectively provide the LED current through each sequential one of the plurality of LEDs in an activated state in response to an activation signal. The at least one LED driver system includes a voltage clamp configured to maintain a substantial constant amplitude difference of a driver voltage associated with the LED current from the activated state to a deactivated state.