Bleed Switch Controller for TRIAC Dimmer Flicker and Efficiency
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Solution Overview
Problem
The use of TRIAC dimmers for controlling LED lamps can lead to flicker due to insufficient bleed current, which worsens the efficiency of AC-DC converters when the TRIAC's on-time is short, necessitating a solution to maintain a constant current flow.
Innovation Solution
A power supply system incorporating a bleed switch controller that generates control signals to manage the bleed switch's operation, turning it off during certain time durations and on during others, with varying current levels to optimize power distribution and prevent flicker, including a sampler, inverter, clock generator, and amplifier for generating appropriate control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant bleed current is maintained to prevent LED flicker, then flicker is prevented, but the efficiency of the AC-DC converter deteriorates
Solution Approach 1:
The patent applies periodic action by controlling the bleed switch to operate in alternating cycles: turning on during the TRIAC off-time to provide bleed current and prevent flicker, and turning off during the TRIAC on-time to improve converter efficiency. This periodic switching resolves the contradiction by providing bleed current only when necessary rather than continuously.
Solution Approach 2:
The patent implements dynamics by making the bleed switch control dynamic rather than static. The bleed switch controller adjusts the bleed current based on real-time TRIAC state detection, transitioning between on and off states to adapt to changing operating conditions, thereby preventing flicker during off-periods while maintaining efficiency during on-periods.
2Power
If the TRIAC on-time is reduced to control power to the LED lamp, then power control is achieved, but flicker is caused due to insufficient bleed current
Solution Approach 1:
The patent introduces an intermediary component - the bleed switch controller - that mediates between the TRIAC power control and the bleed current requirement. This controller detects TRIAC off-events and activates the bleed switch during these periods, ensuring sufficient bleed current is provided whenever the TRIAC is off, thereby preventing flicker while maintaining power control capability.
Solution Approach 2:
The patent applies preliminary action by proactively activating the bleed switch in anticipation of LED flicker conditions. The controller detects TRIAC off-time and immediately provides bleed current during this period, preventing the flicker condition before it occurs rather than reacting after flicker is detected.
3Reliability
If the TRIAC on-time is increased to maintain constant current, then flicker is prevented, but power control capability is reduced
Solution Approach 1:
The patent applies segmentation by dividing the control function into two separate components: the TRIAC handles power control during its on-periods, while the bleed switch handles constant current maintenance during off-periods. This segmentation allows each component to optimize its function without compromising the other, enabling both power control and flicker prevention to coexist.
Data Source
AI summary
A power supply has a TRIAC dimmer, and an AC-DC converter connected to the TRIAC dimmer. The AC-DC converter has a power switch, a bleed switch, and a controller. The controller turns off the bleed switch in a first time duration and turns on the bleed switch in a second time duration. Magnitude of a current of the power switch in the first time duration is larger than magnitude of a current of the power switch in the second time duration. Magnitude of a current of the bleed switch in a third time duration within the second time duration is smaller than magnitude of a current of the bleed switch in a fourth time duration within the second time duration.