Solid State Lighting Deep Dimming via Phase Detection Shutdown
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Solution Overview
Problem
Conventional dimmers have limitations in achieving minimum light levels below 5% and maximum light levels above 100% with solid-state lighting systems, as they require a minimum current to function, leading to flicker and reduced light output efficacy.
Innovation Solution
A power converter system with a phase detector, processing unit, and switch that detects rising edges of voltage waveforms and deactivates the power converter for a predetermined shutdown period, allowing for deep dimming by preventing power delivery during this time, thereby extending the range of light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional dimmers are used with solid state lighting systems, then the lighting system can be dimmed, but the minimum light level cannot go below 5% and maximum light level cannot exceed 100% due to minimum current requirements
Solution Approach 1:
The system performs preliminary action by detecting the zero-crossing points of the AC waveform and using this information to control the power converter's shutdown timing. The processor shuts down the power converter for a predetermined period after each zero-crossing detection, which prevents the converter from operating during critical portions of the waveform and enables deep dimming while avoiding flicker.
Solution Approach 2:
The system implements periodic action by continuously monitoring the AC waveform for zero-crossing points and repeatedly applying the shutdown period after each detection. This periodic shutdown mechanism ensures consistent deep dimming operation throughout the AC cycle, maintaining reliability while extending the light output range.
2Illumination intensity
If the power converter operates continuously to maintain light output, then lighting capability is preserved, but minimum current requirements cause flicker and limit deep dimming capability
Solution Approach 1:
The system extracts the harmful operation period from the AC waveform by identifying zero-crossing points and removing power delivery during the subsequent predetermined period. This extraction of the problematic operational window eliminates flicker while preserving light output control capability through the remaining waveform portions.
Solution Approach 2:
The system converts the harmful minimum current requirement into a beneficial control mechanism by using zero-crossing detection to precisely timing the power converter shutdown. The constraint that causes flicker is transformed into the basis for a reliable dimming control strategy that extends the operational range.
3Illumination intensity
If conventional dimmers chop voltage waveforms to reduce power, then dimming is achieved, but fixed minimum RMS output voltages limit the minimum light level to above 30%
Solution Approach 1:
The system implements dynamics by replacing the fixed minimum voltage constraint of conventional dimmers with a dynamic control mechanism. The processor adjusts the power converter's operation in real-time based on zero-crossing detection, enabling the minimum light level to extend to 0% while maintaining control through adaptive shutdown timing rather than fixed voltage thresholds.
Data Source
AI summary
Disclosed are devices and related methods for optimally extending the range of light output of solid-state light sources, particularly at minimum light levels, through a power converter that includes a phase detector, a processing unit and a switch. The phase detector is configured to receive a voltage signal and to detect rising edges of waveforms of the voltage signal. The processing unit is configured to initiate a predetermined shutdown period in response to each detected rising edge. The switch is configured to provide a control signal that deactivates the power converter during the shutdown period, preventing the power converter from providing power to the solid state light unit during the shutdown period.