LED Driver Bleeder Circuit for Silicon-Controlled Dimmer Flicker
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Solution Overview
Problem
LED drivers using silicon-controlled dimmers face issues with flickering due to leakage currents, which cause errors in conduction angle and result in inconsistent dimming, leading to inefficiencies and reduced system performance.
Innovation Solution
Incorporating a bleeder circuit and controller in the LED driver to manage the DC bus voltage by drawing a bleed current before the silicon-controlled dimmer is turned on, and cutting off the bleed path when it is on, thereby stabilizing the conduction angle and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a silicon-controlled dimmer is used for LED dimming control, then dimming functionality is achieved, but leakage currents cause conduction angle errors and flickering
Solution Approach 1:
The bleeder circuit is activated before the silicon-controlled dimmer to pre-discharge the capacitor and establish a known initial state. This preliminary action ensures that when the dimmer turns on, the conduction angle is accurately determined without interference from residual charges or leakage currents, thereby resolving the reliability issue while maintaining dimming functionality
2Ease of operation
If leakage current is present in the silicon-controlled dimmer, then dimming is achieved, but conduction angle error increases causing flickering
Solution Approach 1:
The bleeder circuit intentionally creates a controlled leakage path that compensates for the harmful leakage currents in the silicon-controlled dimmer. By providing a known, controllable leakage mechanism, the circuit converts the harmful effect of leakage into a beneficial compensation mechanism, eliminating flickering while preserving dimming control
3Device complexity
If DC bus voltage is not stabilized before silicon-controlled dimmer turn-on, then circuit simplicity is maintained, but conduction angle accuracy deteriorates
Solution Approach 1:
The bleeder circuit performs a preliminary voltage stabilization action before the silicon-controlled dimmer operates. This pre-action ensures the DC bus voltage is at the correct level when the dimmer turns on, enabling accurate conduction angle measurement without requiring complex continuous voltage regulation circuitry throughout the entire operation cycle
4Stability of the object's composition
If bleed path is continuous, then DC bus voltage stability is improved, but power loss increases
Solution Approach 1:
The bleeder circuit operates periodically rather than continuously, activating only when needed to stabilize the DC bus voltage before silicon-controlled dimmer turn-on. This periodic operation maintains voltage stability when required while minimizing power loss during normal operation, resolving the contradiction between stability and energy efficiency
Data Source
AI summary
An apparatus can include: a bleeder circuit coupled to a DC bus of an LED driver having a silicon-controlled dimmer; the bleeder circuit being configured to control a voltage of the DC bus to vary in a predetermined manner by drawing a bleed current through a bleed path when in a first mode, and to cut off the bleed path when in a second mode; and a controller configured to control the bleeder circuit to be in the first mode before the silicon-controlled dimmer is turned on.