SMPS Bleeder Circuit for TRIAC Dimmer Flickering
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Solution Overview
Problem
LED lamps experience flickering and dimming control issues when used with conventional TRIAC dimmers due to insufficient current supply and varying performance characteristics of TRIAC dimmers from different manufacturers, leading to compatibility challenges.
Innovation Solution
A switched mode power supply with a bleeder circuit and automatic power factor correction is introduced to maintain a current flow equal to or greater than the TRIAC holding current, ensuring compatibility with TRIAC dimmers and reducing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LED lamps are used to replace conventional incandescent or halogen lamps with TRIAC dimmers, then energy efficiency is improved, but light flickering occurs due to insufficient current supply
Solution Approach 1:
The patent applies preliminary action by providing a compensation current before the TRIAC current drops below the holding current threshold. The controller monitors the TRIAC current and activates the compensation current source proactively to maintain the total current above the holding current, preventing flickering before it occurs. This is evident in the circuit where the compensation current is supplied through resistors R1 and R2 when the TRIAC current becomes insufficient.
2Ease of operation
If TRIAC dimmers are used for brightness control, then dimming capability is improved, but compatibility issues arise due to varying performance characteristics of TRIAC dimmers from different manufacturers
Solution Approach 1:
The patent achieves universality by designing a power supply circuit that can work with TRIAC dimmers from different manufacturers. The controller is configured to monitor TRIAC current and automatically adjust compensation current to maintain operation above the holding current threshold, making the system compatible with various TRIAC dimmer performance characteristics. This multi-functional approach allows the same circuit to adapt to different TRIAC dimmer specifications.
3Reliability
If compensation current is provided to maintain TRIAC holding current, then light flickering is reduced, but power loss in the bleeder circuit increases
Solution Approach 1:
The patent applies partial action by providing compensation current only when necessary - specifically when the TRIAC current drops below the holding current threshold. The controller monitors the TRIAC current and activates the compensation current source only during these critical periods, rather than continuously. This reduces power loss in the bleeder circuit while still preventing flickering when needed.
4Device complexity
If LED lamps directly replace conventional lamps, then simplicity is maintained, but flickering occurs due to insufficient current to sustain TRIAC holding current
Solution Approach 1:
The patent introduces an intermediary compensation current source between the power supply and the TRIAC dimmer. This compensation current acts as a mediator that supplements the LED lamp current when it becomes insufficient to maintain TRIAC conduction. The intermediary circuit includes compensation current sources and control logic that automatically activate when needed, resolving the flickering issue without requiring complete redesign of the lighting system.
Data Source
AI summary
A bleeder circuit is provided in a switched mode power supply (SMPS) that provides a compensation current when the loop current drops below the holding current of the TRIAC to alleviate light flickering problem. Further, automatic power factor correction is also provided in embodiments of the invention, which enables the output current to be in phase with the input voltage. The power factor correction not only improves the efficiency of the power supply, it can also reduce the compensation current and the duration in which compensation current flows, thereby reducing the power loss in the bleeder circuit.