LED Drive Circuit Phase Angle Control TRIAC Stability
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Solution Overview
Problem
Conventional LED illumination systems using a.c. power supplies experience flickering and inefficiency when connected to phase control type light adjusters, particularly due to rapid changes in current and TRIAC instability, which leads to unstable light adjustment and increased power consumption.
Innovation Solution
An LED drive circuit with a phase angle detection portion, reference voltage generation, and current draw-out mechanism that independently controls current based on detected phase angles, preventing TRIAC turn-off and optimizing current flow to alleviate flickering and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a phase control type light adjuster is connected to an LED illumination apparatus using a.c. power supply, then light adjustment control can be performed using existing facilities, but flickering and TRIAC instability occur due to rapid current changes
Solution Approach 1:
The patent introduces an LED drive circuit as an intermediary device between the phase control type light adjuster and the LED illumination apparatus. This drive circuit includes a rectifier bridge, smoothing capacitor, and control circuit that processes the phase-controlled a.c. voltage before supplying it to the LEDs, thereby isolating the TRIAC from direct interaction with the LED load and preventing instability and flickering while maintaining compatibility with existing light adjusters
2Use of energy by moving object
If the phase angle of the light adjuster is increased to reduce brightness, then power consumption is reduced, but the current becomes lower than the hold current causing TRIAC turn-off and flickering
Solution Approach 1:
The patent employs a feedback mechanism where the control circuit continuously monitors the current flowing through the LED string and the phase angle of the input voltage. Based on this feedback, the control circuit dynamically adjusts the switching timing and duty cycle of the power switch to maintain stable current flow above the TRIAC hold current threshold, preventing unintended TRIAC turn-off while still achieving power consumption reduction through phase angle control
Solution Approach 2:
The patent implements dynamic control of the power switch timing and duration based on the detected phase angle. As the phase angle changes to adjust brightness, the control circuit dynamically modifies the switching parameters to ensure the current remains sufficient to keep the TRIAC latched on, adapting the system behavior in real-time to maintain stability across different brightness levels
3Use of energy by moving object
If LEDs are connected in series to achieve desired illuminance, then power consumption is reduced, but the circuit becomes more sensitive to current variations and TRIAC instability
Solution Approach 1:
The patent incorporates a smoothing capacitor that charges during the conduction period and discharges during the non-conduction period, providing beforehand cushioning by maintaining a relatively stable voltage across the series-connected LED string despite variations in the phase-controlled input current. This energy storage mechanism cushions the circuit against current variations that would otherwise cause TRIAC instability, enabling the use of series-connected LEDs for reduced power consumption
Data Source
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AI summary
An LED drive circuit which is connectable to a phase control type light adjuster, including: a first reference voltage generation portion that generates a first reference voltage; a second reference voltage generation portion that generates a second reference voltage according to a phase angle of the light adjuster; an input voltage detection portion that detects a size relationship between an input voltage and a threshold value voltage; a current draw-out portion that draws out a current in accordance with the first reference voltage or the second reference voltage from an electricity supply line that supplies electricity to an LED drive portion; and a switch portion that in accordance with a detection result by the input voltage detection portion, performs switching between an output from the first reference voltage generation portion to the current draw-out portion and an output from the second reference voltage generation portion to the current draw-out portion.