Multi-Slope Dimming Control for Flicker-Free Triac Lighting
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Solution Overview
Problem
High-Performance dimmers face challenges with slow response times and overshoot/undershoot issues when using phase-cut Triac dimmers, leading to flickering and flashing due to complex instantaneous current changes and power supply oscillations.
Innovation Solution
A multi-slope power supply system that uses adaptive slew-rates to control power supply transitions, eliminating overshoot and undershoot by comparing dimmer levels with inflection points and generating control signals to manage slew-rates, thereby reducing flickering and flashing during fast transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase-cut Triac dimmers are used for control, then dimming capability is achieved, but overshoot and undershoot occur during fast transitions
Solution Approach 1:
The patent implements dynamic slew-rate adjustment by comparing the instantaneous dimmer level with inflection points and selecting different slew-rates accordingly. The system transitions from a fixed slew-rate approach to a dynamic multi-slope approach where the slew-rate changes based on the dimmer level, eliminating overshoot and undershoot during fast transitions while maintaining dimming capability.
Solution Approach 2:
The patent changes the parameter of slew-rate from a fixed value to a variable parameter that depends on the dimmer level. By defining multiple inflection points and associating different slew-rates with different ranges of dimmer levels, the system optimizes the transition characteristics dynamically, preventing voltage instability during dimming operations.
2Speed
If fast power supply transitions are implemented, then responsiveness is improved, but overshoot and flickering occur
Solution Approach 1:
The system dynamically adjusts the transition speed (slew-rate) based on the operating point. When the dimmer level is below the first inflection point, a faster slew-rate is used for quick response. When the dimmer level exceeds the inflection point, a slower slew-rate is applied to prevent overshoot. This dynamic adjustment maintains both fast responsiveness and voltage stability.
Solution Approach 2:
The patent segments the dimming range into multiple regions defined by inflection points, with each region having its own optimized slew-rate. This segmentation allows the system to apply different transition speeds appropriate for each operating region, achieving fast transitions when safe and slower transitions when approaching stability limits.
3Reliability
If multi-slope control with inflection points is implemented, then overshoot is eliminated, but system complexity increases
Solution Approach 1:
The patent manages complexity by organizing the control logic around clearly defined inflection points and associated slew-rates. The controller compares the dimmer level with inflection points and selects the appropriate slew-rate from a predefined set, creating a structured and manageable control system that achieves voltage stability without excessive complexity.
Data Source
AI summary
A method of controlling a power supply electrically coupled to a dimmer and a light source includes receiving a plurality of sample values corresponding to dimmer levels, comparing a sample value of the plurality of sample values with one or more inflection points, the one or more inflection points being associated with a plurality of slew-rates, identifying a particular slew-rate among the plurality of slew-rates based on the comparison, and generating a control signal based on the particular slew-rate for transmission to the power supply.