LED Current Drive Circuit for Triac Dimmer Flicker Prevention
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Solution Overview
Problem
Existing LED drive circuits are not compatible with triac dimmers, leading to flickering issues due to the triac dimmer being turned on and off during dimming processes with small duty cycles of PWM dimming signals, as the input current exceeds or falls below the holding current of the triac dimmer.
Innovation Solution
A current drive circuit that includes a current generation circuit and an input current regulation circuit, which generates a drive current based on a PWM dimming signal and regulates the operation state of the triac dimmer by controlling the duty cycle, ensuring the triac dimmer is turned off before the holding current is reached, thereby preventing flickering. This is achieved through a combination of a switch-type or constant current linear drive circuit and an input current regulation circuit that compares the duty cycle to a threshold, cutting off the input current path when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the LED drive circuit uses a PWM dimming signal with small duty cycle, then the dimming effect is improved, but the triac dimmer turns on and off during dimming causing flickering
Solution Approach 1:
The input current regulation circuit proactively regulates the input current to the triac dimmer before the triac can turn off during dimming. By controlling the input current to remain above the holding current threshold throughout the PWM dimming cycle, the triac maintains its on-state and prevents flickering, allowing small duty cycles to be used without instability.
2Use of energy by moving object
If the input current to triac dimmer is reduced for energy efficiency, then energy consumption is improved, but the triac dimmer turns off during operation causing flickering
Solution Approach 1:
The system dynamically adjusts the input current parameter to maintain it above the triac's holding current threshold. The input current regulation circuit monitors and regulates the input current to the triac dimmer, ensuring it remains sufficiently high to keep the triac in its on-state, thereby preventing flickering while still allowing energy-efficient operation at reduced power levels.
3Adaptability or versatility
If the LED drive circuit is made compatible with triac dimmer, then adaptability is improved, but the circuit complexity increases due to input current regulation
Solution Approach 1:
The input current regulation circuit serves multiple functions simultaneously: it regulates the input current to the triac dimmer to prevent flickering, works with both PWM dimming signals and triac dimming, and maintains compatibility across different operating conditions. This multi-functionality achieves triac dimmer compatibility without proportionally increasing overall circuit complexity.
Data Source
AI summary
A current drive circuit applied in an LED drive circuit that is compatible with a triac dimmer and is configured to generate a direct current bus voltage includes: a current generation circuit configured to receive the direct current bus voltage, and to generate a drive current based on a PWM dimming signal, in order to drive an LED load; and an input current regulation circuit configured to generate a regulation signal based on a duty cycle of the PWM dimming signal, in order to control an operation state of the triac dimmer.