LED Lighting Bleeder Control for Small-Angle Triac Dimming
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Solution Overview
Problem
The continuous generation of a bleed-off current to maintain a triac dimmer's turn-on state results in significant loss and reduced efficiency when the turn-on angle is small, especially when the turn-on angle is less than 90 degrees, as it fails to detect the LED load current accurately.
Innovation Solution
A lighting circuit with a turn-on angle detection circuit and a bleeder circuit that controls the bleeder's operation based on detected turn-on angles and LED load current, turning off the bleeder when unnecessary to avoid continuous bleed-off current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bleeder circuit continuously generates bleed-off current to maintain the triac dimmer turn-on state, then the triac dimmer remains reliably on, but significant energy loss occurs and system efficiency decreases
Solution Approach 1:
The bleeder circuit is transformed from a static continuously-on state to a dynamic state that adapts to operating conditions. The control circuit dynamically switches the bleeder circuit on or off based on real-time detection of turn-on angle and LED load current, making the system flexible and condition-dependent rather than fixed
Solution Approach 2:
A feedback mechanism is implemented where the control circuit continuously monitors the turn-on angle and LED load current, then uses this information to control the bleeder circuit operation. This closed-loop feedback allows the system to automatically adjust bleed-off current generation based on actual operating conditions, eliminating the need for continuous current when not required
2Loss of energy
If the bleeder circuit is turned off when LED load current is sufficient, then energy loss is reduced, but the triac dimmer may fail to remain on when turn-on angle is small
Solution Approach 1:
The control circuit performs preliminary detection of turn-on angle and LED load current before making decisions about the bleeder circuit operation. By detecting conditions in advance and predicting whether the LED current will be sufficient to maintain the triac on, the system can proactively control the bleeder circuit to prevent energy loss while ensuring reliable operation
Solution Approach 2:
The system replaces the traditional mechanical/electrical approach of continuous bleed-off current with an intelligent control system that uses detection circuits and control logic to substitute the function of continuous current with conditional, intelligent decision-making about when current is actually needed
Data Source
AI summary
A lighting circuit and a control method thereof are provided. The lighting circuit includes a triac dimmer connected between an alternating current (AC) input power supply and a rectifier circuit, where the rectifier circuit is configured to output a bus voltage after phase cutting, and further includes a turn-on angle detection circuit configured to detect a turn-on state of the triac dimmer and output a first detection signal that represents a relationship between a turn-on angle of the triac dimmer and a first angle, and a bleeder circuit connected to the rectifier circuit and configured to control turn-off time of the bleeder circuit based on the first detection signal and a sampling signal representing a current of a light-emitting diode (LED) load.