Programmable LED Dimming Interface Modulation Conversion
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Solution Overview
Problem
Existing LED dimming technologies, such as PWM and PAM, face issues with electromagnetic interference (EMI), flickering at low light intensities, and require high-resolution digital-to-analog converters (DACs) that occupy large space and consume significant power, making them inefficient for high-resolution dimming.
Innovation Solution
A programmable LED dimming interface that converts between different modulation formats, including PWM, PAM, and DC, using high-order delta-sigma modulation to generate dimming signals, reducing the need for high-resolution DACs and precision timers, and incorporating dithering for improved EMI performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM modulation is used for LED dimming, then dimming functionality is achieved, but electromagnetic interference (EMI) and flickering occur at low frequencies
Solution Approach 1:
The patent changes the modulation frequency parameter to operate above the LED flicker fusion threshold (typically >200Hz), and adjusts the duty cycle parameter to achieve desired dimming levels while maintaining stable operation. By optimizing these parameters, the system achieves smooth dimming without visible flicker or excessive EMI.
Solution Approach 2:
The patent employs periodic pulse-width modulation where the LED is switched on and off at high frequency with varying duty cycles. This periodic action above the human visual threshold creates the perception of continuous dimming without actual flicker, while the high-frequency operation reduces EMI compared to lower frequency alternatives.
2Measurement precision
If high-resolution DACs are used to support high-resolution dimming, then dimming precision is improved, but chip area and power consumption increase
Solution Approach 1:
The patent segments the dimming control into two parts: a coarse control achieved through PWM duty cycle adjustment and a fine control achieved through frequency modulation. This segmentation allows the system to achieve high effective resolution without requiring a single high-resolution DAC, instead using two lower-resolution components working together.
Solution Approach 2:
The patent adds the frequency dimension to the traditional duty-cycle-only PWM approach. By modulating both duty cycle and frequency, the system creates an additional control dimension that effectively multiplies the resolution capability, achieving what would otherwise require a high-resolution DAC using only moderate-resolution components.
3Measurement precision
If high-resolution DACs are used for high-resolution dimming, then dimming precision is improved, but power consumption increases
Solution Approach 1:
The patent divides the resolution requirement between two functions: duty cycle control for coarse adjustment and frequency control for fine adjustment. This segmentation allows each component to operate at lower resolution, significantly reducing the power consumption associated with high-resolution DAC operation while maintaining the same effective dimming precision.
4Adaptability or versatility
If a universal LED dimming interface is designed to support multiple modulation formats, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent designs a unified PWM interface that can operate in multiple modes: standard PWM dimming, frequency-modulated PWM for high-resolution control, and combinations thereof. This multi-functionality allows the same hardware interface to support various dimming requirements without requiring separate dedicated circuits for each modulation scheme, managing complexity while maintaining versatility.
Data Source
AI summary
Described herein is an apparatus including, a decoder that is configured to decode a digital control code. The digital control code corresponds to an intensity level control code of a plurality of LEDs. The apparatus includes a modulator that modulates a combination of the decoded control code and a dither signal, wherein the combined signal has a first modulation format. The apparatus also includes a converter that generates a dimming control signal by converting the first modulation format associated with the combined signal to a programmable second modulation format.