Dimmer Circuit Switching Dummy Load for LED Stability
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Solution Overview
Problem
Existing dimmer circuits face challenges when used with light emitting diode (LED) light sources, as they do not draw sufficient current for correct operation, leading to inefficiencies and potential flicker due to insufficient load and resonant frequencies.
Innovation Solution
A circuit with a switch that automatically engages and disengages a first load at predetermined times relative to the zero-crossing of the input signal, providing a dynamic load to support dimmer operation and mitigate resonant frequencies, and optionally incorporating a second load for triac dimmer support, allowing for efficient operation across various dimming levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional dimmer circuit is used with LED light sources, then the dimmer can control brightness, but the LED does not draw sufficient current for correct dimmer operation
Solution Approach 1:
A dummy load circuit is introduced as an intermediary component to provide additional current draw from the dimmer. This dummy load acts as a mediator between the LED driver and dimmer, ensuring the dimmer receives sufficient current for proper operation while the LED remains the primary lighting source.
Solution Approach 2:
The dummy load is dynamically controlled through a switch that activates it only during specific portions of the AC waveform when the LED driver current is insufficient. This dynamic activation ensures adequate total current draw without continuously dissipating power through the dummy load.
2Reliability
If a dummy load is continuously engaged to provide sufficient current draw, then dimmer operation is stabilized, but power dissipation increases
Solution Approach 1:
The dummy load operates periodically rather than continuously, being activated only during specific intervals of the AC waveform when additional current is needed. This periodic operation maintains dimmer stability while minimizing unnecessary power dissipation in the dummy load.
Solution Approach 2:
The dummy load provides excessive current draw only when necessary, rather than maintaining a constant current. This partial action approach ensures adequate current for dimmer operation during critical periods while avoiding continuous power waste.
3Reliability
If the dummy load provides excessive current draw, then dimmer operation is ensured, but flicker may occur due to resonant frequencies
Solution Approach 1:
The resistance value of the dummy load is carefully selected to provide sufficient current draw without creating excessive total current that would excite resonant frequencies. By optimizing this parameter, the system maintains reliable dimmer operation while avoiding the harmful flicker effect.
Solution Approach 2:
The potential harmful effect of excessive current draw causing resonance and flicker is converted into a benefit by carefully controlling the dummy load current to be sufficient for dimmer operation but limited enough to avoid resonant frequencies, thus eliminating the harm while maintaining the benefit.
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3~5
AI summary
A circuit for connecting to a dimmer, the circuit configured to receive an input signal from the dimmer. The circuit comprises a first load and a switch. The switch is operable to automatically engage the first load at a predetermined time from a zero-crossing of the input signal and automatically disengage the first load at other times.