LED Lamp Controller for Triac Dimmer Holding Current Compensation
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Solution Overview
Problem
Triac-based dimmers prematurely shut down when the current through them drops below the holding current value, leading to abnormal light flicker and reduced efficacy, especially when dealing with mixed loads of LED-based lamps.
Innovation Solution
A controller is used to detect the leading edge of the dimmer phase-cut voltage and control the lamp current to prevent the dimmer current from undershooting the holding current value, ensuring continuous conduction and maintaining the intended dimming level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If triac-based dimmers are used to control LED lighting, then energy savings and long life are achieved, but premature shutdown and abnormal light flicker occur when current drops below holding current value
Solution Approach 1:
The controller proactively generates compensation current before the dimmer current can drop below the holding current threshold. By detecting the leading edge of the dimmer phase-cut voltage and calculating the required compensation current based on the difference between holding current and expected load current, the system prevents premature triac shutdown before it occurs, eliminating light flicker and ensuring continuous conduction.
2Adaptability or versatility
If mixed loads of LED-based lamps are connected to triac-based dimmers, then lighting versatility is improved, but current undershoot causes premature shutdown and reduced efficacy
Solution Approach 1:
The controller continuously monitors the dimmer current by detecting the leading edge of the phase-cut voltage and calculating the actual current based on the known triac holding current threshold. When the calculated current approaches or drops below the holding current value, the controller automatically generates compensation current to maintain the current above the threshold, creating a closed-loop feedback system that ensures stable operation with mixed LED loads.
3Ease of operation
If dimmer current is allowed to drop below holding current value, then simple control is maintained, but premature shutdown occurs causing abnormal light flicker
Solution Approach 1:
The controller acts as an intermediary between the triac-based dimmer and the LED load. It injects compensation current through the dimmer circuit to prevent the total current from dropping below the triac holding current threshold. This intermediary action maintains continuous triac conduction without requiring changes to the simple dimmer operation or the LED driver circuitry, eliminating light flicker while preserving ease of operation.
Data Source
AI summary
In at least one embodiment, a system and method provide current compensation in a lighting system by controlling a lamp current to prevent a current through a triac-based dimmer from undershooting a holding current value. In at least one embodiment, at least one of the lamps includes a controller that controls circuitry in the lamp to draw more lamp current for a period of time than needed to illuminate a brightness of the lamp at a level corresponding to particular phase-cut angle of the supply voltage. By drawing more current than needed, the controller increases the dimmer current during the period of time to prevent the dimmer current from falling below the holding current value. In at least one embodiment, the period of time corresponds to a compensating pulse of the lamp current at a time when the dimmer current would otherwise fall below the holding current value.