Phase Angle Detection Circuit for Solid State Lighting Dimmers
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Solution Overview
Problem
Solid state lighting loads, such as LEDs, experience flicker and operational issues when used with conventional phase chopping dimmers due to asymmetrical waveforms caused by insufficient load current and power supply problems, leading to compatibility issues between dimmers and solid state lighting load drivers.
Innovation Solution
A system and method for detecting asymmetrical waveforms in the input mains voltage signal by measuring phase angles of a dimmer connected to a power converter, with a phase angle detection circuit implementing corrective actions, such as adjusting the power converter's operating point or shutting it down, when the difference between consecutive half cycles exceeds a threshold, to ensure symmetric waveforms and stable light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional phase chopping dimmers are used with solid state lighting loads, then dimming functionality is achieved, but asymmetrical waveforms cause flicker and operational issues
Solution Approach 1:
The system performs preliminary detection of waveform asymmetry by measuring phase angles before the flicker problem manifests. The control circuit detects asymmetrical waveforms caused by insufficient load current and proactively implements corrective actions, such as adjusting the power converter operating point or shutting it down, to prevent flicker and operational issues before they occur.
Solution Approach 2:
The system establishes a feedback loop where the control circuit continuously monitors the phase angles of consecutive half cycles of the input mains voltage signal. By comparing the difference between measured phase angles and determining waveform symmetry, the system receives feedback on its own operation and automatically adjusts or shuts down the power converter to correct asymmetrical waveforms and eliminate flicker.
2Stability of the object's composition
If phase angle detection and corrective actions are implemented, then waveform symmetry is improved, but device complexity increases
Solution Approach 1:
The system replaces complex mechanical or hardware-based waveform correction mechanisms with electronic detection and control methods. The control circuit uses digital processing to measure phase angles, compare consecutive half cycles, and implement corrective actions through electronic control of the power converter, simplifying the overall system while achieving waveform symmetry.
Data Source
Figure 1A~1C
Figure 2~3B
Figure 4
AI summary
A system is provided for controlling power delivered to a solid state lighting load. The system being intended to be connected to voltage mains through a dimmer 204 configured to adjustably dim light output of the solid state lighting load. The system comprises a power converter and a phase angle detection circuit. The power converter 220, 620 is configured to drive the solid state light load in response to a rectified input voltage signal originating from the voltage mains. The phase angle detection circuit 210, 610 is configured to detect a phase angle of the dimmer having consecutive half cycles of the input voltage signal, to determine a difference between the consecutive half cycles, and to implement a corrective action when the difference is greater than a difference threshold, indicating asymmetric waveforms of the input voltage signal.