Line Voltage Detection Circuit for TRIAC Dimmer Compatibility
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Solution Overview
Problem
Conventional TRIAC dimmers are incompatible with LED light sources due to the capacitive and inductive load presented by LED circuits, which are different from the resistive load expected by legacy TRIAC dimmers, leading to incompatibility and issues with dimming and controlling LEDs.
Innovation Solution
A line voltage detection circuit with digital filter modules is used to detect the presence and type of TRIAC dimmer, allowing for effective dimming and control of LEDs by determining the chopped input signal and adjusting the power level based on the detected voltage and frequency thresholds, and by discharging a capacitor to reduce impedance and prevent flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional TRIAC dimmers are used with LED light sources, then the dimming function can be provided, but the incompatibility due to different load characteristics causes operation failures and flickering
Solution Approach 1:
The system performs preliminary detection of the input signal characteristics (voltage thresholds, frequency, chopping pattern) before attempting to dim the LED. This preliminary action allows the controller to identify whether a TRIAC dimmer is present and adjust its operation accordingly, preventing the incompatibility issues that would otherwise occur
Solution Approach 2:
The system changes its operating parameters based on the detected input signal characteristics. By detecting the chopped AC current pattern and voltage thresholds, the controller adapts its dimming algorithm to match the specific TRIAC dimmer behavior, enabling compatible operation between the dimmer and LED light source
2Ease of operation
If the input signal is chopped by TRIAC to control LED power, then dimming function is achieved, but detection of the chopped signal becomes more difficult
Solution Approach 1:
The system uses feedback from the detected input signal characteristics to adjust its detection and control strategy. By monitoring the chopped AC current pattern and comparing it against expected TRIAC dimming patterns, the system can reliably identify the presence of a TRIAC dimmer and adapt its operation accordingly
Solution Approach 2:
The system performs preliminary detection of the input signal characteristics (voltage thresholds, frequency, chopping pattern) before attempting to dim the LED. This preliminary action allows the controller to identify whether a TRIAC dimmer is present and adjust its operation accordingly
Data Source
AI summary
A first filter outputs a first signal in response to receiving an input signal. The first signal has a first state in response to the input signal reaching a first threshold voltage on a leading edge of the input signal, and a second state in response to the input signal reaching the first threshold voltage on a trailing edge of the input signal. A second filter outputs a second signal in response to receiving the input signal. The second signal has the first state in response to the input signal reaching a second threshold voltage on the leading edge of the input signal, and the second state in response to the input signal reaching the second threshold voltage on the trailing edge of the input signal. A detection circuit determines, based on times when the first and second thresholds are reached, whether the input signal is received from a triac.