Bidirectional AC Dimmer Circuit for Flicker-Free Load Compatibility
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Solution Overview
Problem
Existing dimmers are limited in their compatibility with various types of loads, particularly failing to maintain efficient power supply to loads with changing impedance and polarity, leading to errors in phase detection and potential operational issues like blinking or flicker.
Innovation Solution
A dimmer design featuring a bidirectional switch, phase detector, and controller that modulates the switch's conduction states based on detected AC voltage phases and dimming levels, ensuring power supply during both halves of the AC cycle and reducing conduction losses, while using a mask processor to minimize phase detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional dimmer design with unidirectional power supply is used, then circuit simplicity is maintained, but load compatibility is limited and phase detection errors occur
Solution Approach 1:
The dimmer circuit is designed to handle both half-cycles of AC voltage symmetrically, enabling it to work with various load types including LED lights, fluorescent lamps, and incandescent bulbs. The bidirectional switch and dual-phase detection system provide universal compatibility across different load impedances and polarities.
Solution Approach 2:
The AC cycle is divided into two separate half-cycles, with independent power supply paths and phase detection for each half. This segmentation allows the circuit to process positive and negative half-cycles separately, improving adaptability to different load characteristics while maintaining manageable circuit complexity through modular design.
2Ease of operation
If power supply is interrupted during half cycles, then phase control is achieved, but control power supply stability deteriorates
Solution Approach 1:
While the bidirectional switch interrupts power to the load for phase control, the control power supply circuit maintains continuous operation by drawing power during both half-cycles through the bidirectional switch. This ensures the microcontroller and phase detection circuits remain continuously powered, maintaining system reliability and stability throughout the dimming operation.
3Measurement precision
If conventional phase detection method is used, then circuit simplicity is maintained, but phase detection precision deteriorates due to errors
Solution Approach 1:
The phase detection circuit uses feedback from the bidirectional switch states and voltage sensing to accurately determine the phase angle of both half-cycles. The microcontroller processes feedback signals from both positive and negative half-cycles, enabling precise phase detection that adapts to different load conditions and minimizes detection errors.
Solution Approach 2:
The phase detection circuit performs preliminary detection of voltage zero-crossings and phase angles before the bidirectional switch executes the dimming control. This preliminary action allows the system to pre-calculate the appropriate switching timing, improving phase detection accuracy and enabling smooth transitions without flicker or instability.
4Adaptability or versatility
If bidirectional switch with both half-cycle conduction is used, then load compatibility and power supply stability are improved, but conduction losses increase
Solution Approach 1:
The bidirectional switch operates in periodic cycles, conducting during both positive and negative half-cycles of the AC waveform. By synchronizing the switching action with the periodic AC waveform and using pulse-width modulation, the system achieves effective dimming control while distributing conduction losses evenly across both half-cycles, preventing excessive heating in any single direction.
Data Source
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AI summary
A dimmer compatible with more kinds of loads is provided. A bidirectional switch (2) is switched so as to conduct and interrupt a bidirectional current between a pair of input terminals (11, 12). A power supply (5) is electrically connected between the pair of input terminals (11, 12) and produces control power by electric power from an AC power supply (8). A controller (6) receives the control power from the power supply (5) to be activated. The controller (6) causes the bidirectional switch (2) to be in an off-state from a start point of a half cycle of AC voltage (Vac) to a first time point when first time elapses. The controller (6) causes the bidirectional switch (2) to be in an on-state from the first time point to a second time point when second time according to the dimming level elapses. The controller (6) causes the bidirectional switch (2) to be in an off-state from the second time point to an end point of the half cycle.