Matrix LED Driver Switching Sequence for Supply Jitter Noise
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Solution Overview
Problem
Matrix LED drivers experience periodic supply jitter-induced noise due to abrupt changes in total current, leading to electromagnetic interference and discomfort for users.
Innovation Solution
A noise reduction circuit incorporating a pseudo random number generator, up counter, and matrix switch controllers, which generates a randomly changing sequence of power-on signals for matrix switches, eliminating periodic abruptness in total current and reducing noise energy by distributing it across different frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If matrix switches are turned on sequentially during one cycle of scan clock, then LED array can be driven with relaxed lead requirements, but periodic abrupt change in total current causes supply jitter-induced noise
Solution Approach 1:
The patent applies pseudo-random periodic action by generating pseudo-random numbers at regular intervals (every scan clock cycle) to determine switch activation sequences. This transforms the fixed periodic switching pattern into a pseudo-random pattern that maintains timing regularity while eliminating predictable periodicity in current draw, thereby reducing electromagnetic interference from supply jitter noise.
2Measurement precision
If PWM current signals with different duty ratios are used for different current channels, then illumination control precision is improved, but total current shows abrupt periodic changes
Solution Approach 1:
The patent changes the temporal distribution parameter of switch activation by introducing pseudo-random timing offsets. Each switch controller activates its associated switches at different times within the scan clock cycle based on pseudo-random numbers, which spreads out the current draw transitions and eliminates the synchronized abrupt changes that occur when all switches transition at the same time.
3Device complexity
If matrix switches are turned on periodically, then scanning control is simplified, but noise energy concentrates at fixed frequency
Solution Approach 1:
The patent introduces dynamic timing offsets to the otherwise static scanning control pattern. The pseudo-random number generator creates varying time offsets that are applied to different switch controllers, making the switching pattern dynamic and adaptive rather than fixed. This dynamic approach spreads noise energy across a broader frequency spectrum while maintaining the simplified scanning control architecture.
Data Source
AI summary
A noise reduction circuit for a matrix LED driver includes a pseudo random number generator, an up counter, a clock module, and a plurality of matrix switch controllers. The matrix switch controllers and the up counter randomly change a power-on sequence applied across matrix switches in the matrix LED driver according to working random numbers generated by the pseudo random number generator. The circuit prevents jitter-induced noise from periodically reoccurring at the power source of the matrix LED driver, thereby reducing noise energy.