LED Driver Phase Control Circuit for Flicker Elimination
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Solution Overview
Problem
Conventional E-transformers designed for halogen lamps cause flicker when used to drive LED strings due to their lower power levels, leading to inefficient LED dimming.
Innovation Solution
A control circuit for LED drivers that includes a phase detector, step-up and step-down stages, and logical units to generate control signals for power switches, enabling precise regulation of the driving voltage and current to the LED string, using a pre-E-transformer with triac for phase cut dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional E-transformers designed for halogen lamps are used to drive LED strings, then the existing transformer structure can be utilized, but flicker occurs due to mismatched power levels
Solution Approach 1:
The patent implements dynamic control of the E-transformer operation by introducing a control circuit that dynamically adjusts the switching timing of power switches based on detected phase information and voltage thresholds. This dynamic adaptation allows the transformer to operate reliably with LED strings by preventing flicker through real-time parameter adjustment, while maintaining compatibility with the existing transformer structure.
2Adaptability or versatility
If phase cut dimming with triac is used, then LED dimming function is achieved, but flicker occurs due to power level mismatch
Solution Approach 1:
The patent employs feedback mechanisms where the control circuit continuously monitors the input signal phase, intermediate node voltage, and LED string current. Based on this feedback, the controller adjusts the switching timing of power switches to maintain stable operation during dimming. The feedback loop ensures that dimming is achieved through controlled power switch timing rather than simple triac phase cutting, eliminating flicker while preserving the dimming function.
Solution Approach 2:
The control circuit performs preliminary detection of the input signal phase and voltage conditions before activating the power switches. By detecting phase information in advance and determining optimal switching timing based on voltage thresholds, the system prepares the power conversion process to avoid flicker conditions, ensuring smooth dimming operation from the outset.
3Device complexity
If conventional E-transformer operation is used, then simple control is maintained, but flicker and inefficient dimming occur
Solution Approach 1:
The control circuit is segmented into distinct functional modules: a phase detector for extracting phase information, a voltage detection unit for monitoring intermediate node voltage, a control unit for determining switching timing, and drive circuits for actuating power switches. This segmentation allows each module to perform its specific function efficiently, managing overall complexity while achieving reliable flicker-free operation through coordinated module interaction.
Data Source
AI summary
A LED driver, a LED driving method and a controller for LED driver are discussed in the present invention. The LED driver detects the phase of the input signal which is phase cut by a triac from a pre-E-transformer. The LED driver regulates the current flowing through the LED strings by varying the phase of the input signal.