LED Dimmer Circuit Event-Based Flicker-Free Control
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Solution Overview
Problem
Current LED dimming techniques face challenges such as flicker, loss of linearity, and resolution at deep dimming ratios, thermal runaway, and difficulty in maintaining color quality across varying temperatures, especially in high-performance backlighting and CRI/CCT applications, due to limitations in PWM and analog dimming methods.
Innovation Solution
A dimmer circuit and method that integrates analog, digital, and firmware modules to achieve flicker-free dimming with high linearity and resolution, allowing programmable dimming profiles and modulation of light color with intensity, while preventing output voltage spikes through a flexible event-based processing system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used to achieve deep dimming ratios, then light intensity can be reduced to very low levels, but flicker and loss of linearity occur
Solution Approach 1:
The patent dynamically adjusts the PWM switching frequency based on the dimming ratio. At deep dimming ratios, the switching frequency is increased to maintain sufficient ON-time for accurate current measurement while keeping the OFF-time short enough to achieve the desired dimming effect. This dynamic frequency adjustment prevents flicker and maintains linearity across the full dimming range.
Solution Approach 2:
The patent changes the PWM switching frequency parameter adaptively according to the dimming ratio. When deep dimming is required, the switching frequency is increased from typical values (e.g., from 100Hz to several kHz) to ensure that the product of frequency and duty cycle maintains adequate ON-time for measurement accuracy while achieving the target low light output.
2Object-affected harmful factors
If external filtering components are added to eliminate noise in dimming signal, then noise is reduced, but system cost and resolution are compromised
Solution Approach 1:
The patent replaces external analog filtering components with a digital signal processing approach. The dimming signal is sampled and processed through digital filtering algorithms implemented in the control circuitry. This digital approach eliminates the need for bulky external capacitors and inductors while preserving full dimming resolution and providing adaptive noise rejection that can be tuned through software.
3Reliability
If temperature sensing and current throttling are implemented to prevent thermal runaway, then LED safety is improved, but light intensity stability deteriorates due to flashing
Solution Approach 1:
The patent implements preliminary thermal management by continuously monitoring LED temperature and predicting thermal trends before thermal runaway occurs. The system uses temperature sensors and thermal modeling to anticipate overheating conditions and proactively adjusts the PWM duty cycle to prevent temperature excursions, avoiding the need for reactive current throttling that causes visible flashing.
Solution Approach 2:
The patent employs a closed-loop feedback system that continuously monitors LED temperature, current draw, and PWM duty cycle. The control algorithm dynamically adjusts the dimming signal based on real-time thermal conditions, smoothing out transitions and maintaining stable light output while preventing thermal runaway. The feedback loop operates at a higher frequency than the PWM dimming signal, enabling fine-grained thermal management without visible effects.
Data Source
AI summary
A dimmer circuit (100) and a dimming method for an event based integrated driver system for a light emitting diode lighting application is disclosed. Dimmer circuit (100) includes a front end module for receiving an external dimming input in an analog domain, a digital domain or software domain and for operating a dimming output; an event generator for generating a plurality of events in a prioritized manner to trigger a respective response through front end module; and a firmware module configured for storing instructions for processing the plurality of events in the prioritized manner and for processing each response to implement a functionality in dimming output, where front end module, event generator and firmware module communicate with each other to generate dimming output of the one or more LEDs, and the dimming output has at least one of a linear profile, a non linear profile, a custom profile or combinations thereof.