LED Dimming Mode Detection Circuit for TRIAC Compatibility
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Solution Overview
Problem
Existing LED lighting systems with TRIAC dimmers face inaccuracies in dimming mode detection, particularly in trailing edge dimming mode, leading to incorrect control of the bleeder circuit and potential power loss, due to the difficulty in distinguishing between trailing edge dimming and non-dimming modes.
Innovation Solution
A dimming mode detection circuit that includes leading edge and trailing edge detection circuits to generate specific signals based on the time length of voltage intervals between sine half-wave cycles, accurately determining the operating mode of the LED lighting system, thereby preventing mistaken triggering of the non-dimming mode and improving bleeder circuit control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing dimming mode detection methods are used, then the system can operate with TRIAC dimmers, but the detection accuracy is insufficient leading to incorrect mode identification
Solution Approach 1:
The detection circuit is divided into separate leading edge detection and trailing edge detection modules. Each module independently analyzes specific voltage waveform characteristics (rising edges vs. falling edges), allowing accurate identification of different dimming modes without interference between detection functions.
Solution Approach 2:
The patent introduces an intermediary detection mechanism that monitors the voltage waveform across the TRIAC dimmer and uses this information to indirectly determine the dimming mode. This intermediary detection approach allows the system to identify dimming modes without directly interfering with the dimmer operation.
2Loss of energy
If trailing edge dimming mode is not accurately detected, then the system maintains simplicity, but power loss occurs due to incorrect bleeder circuit control
Solution Approach 1:
The detection circuit utilizes the existing voltage waveforms present in the circuit during normal operation to automatically identify the dimming mode. The system serves itself by using its own operational characteristics as the detection signal, eliminating the need for external detection equipment or additional sensors.
Solution Approach 2:
The detection method monitors changes in voltage waveform parameters (such as the presence or absence of specific rising or falling edges) to determine the dimming mode. By detecting parameter changes in the existing voltage signal rather than adding new signals, the system achieves accurate detection without increasing overall system complexity.
3Measurement precision
If the detection circuit cannot distinguish between trailing edge dimming and non-dimming modes, then the circuit design remains simple, but the system experiences incorrect mode triggering
Solution Approach 1:
The detection circuit dynamically adapts its detection strategy based on the operational state of the system. It continuously monitors voltage waveforms and adjusts its interpretation based on the detected patterns, allowing it to correctly identify trailing edge dimming mode even when the waveform characteristics vary during operation.
Solution Approach 2:
The detection circuit operates periodically by monitoring voltage waveforms at specific intervals corresponding to the AC line frequency and dimmer operation cycles. This periodic detection approach allows the system to accumulate sufficient information over multiple cycles to accurately distinguish between trailing edge dimming and non-dimming modes.
Data Source
AI summary
A dimming mode detection circuit for an LED lighting system that receives an alternating current input voltage and generates a bus voltage to drive an LED load, the dimming mode detection circuit including: a leading edge detection circuit configured to generate a leading edge detection signal by detecting a leading edge of a first voltage representative of the bus voltage in one sine half-wave cycle, in order to determine whether the LED lighting system operates in a leading edge dimming mode; and a trailing edge detection circuit configured to generate a trailing edge detection signal in accordance with a time length of a first interval from a first value of the first voltage in a previous sine half-wave cycle to a second value of the first voltage in a next sine half-wave cycle, in order to determine whether the LED lighting system operates in a trailing edge dimming mode.