Auto-Selecting Holding Current Circuit for TRIAC Stability
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Solution Overview
Problem
Conventional adaptive bleeder circuits are not applicable to TRIACs with different holding-current values, leading to inefficiencies in maintaining normal operation of TRIAC dimmable LED drivers.
Innovation Solution
An auto-selecting holding current circuit that includes a first sensor module to detect current drop times, a second sensor module to output critical current signals, and a reference voltage selecting circuit to dynamically adjust the bleeder circuit's output, ensuring the input current through the TRIAC remains greater than or equal to its holding-current value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional adaptive bleeder circuit is used to maintain TRIAC operation, then the TRIAC can remain turned on, but the circuit is not applicable to TRIACs with different holding-current values
Solution Approach 1:
The patent implements dynamic adaptability by detecting the actual holding current value of the TRIAC and automatically adjusting the bleeder circuit's current output in real-time. The control circuit continuously monitors the TRIAC's holding current characteristic and modifies the bleeder current accordingly, transforming a static fixed-current circuit into a dynamic adaptive system that can handle different TRIAC types.
Solution Approach 2:
The patent employs feedback mechanisms where the control circuit detects the TRIAC's holding current value and uses this information to regulate the bleeder circuit's current output. The detection result feeds back to the control circuit, which then adjusts the bleeder current to maintain optimal TRIAC operation, creating a closed-loop control system that adapts to different TRIAC characteristics.
2Reliability
If a constant resistor is used in the bleeder circuit to extract current from input voltage, then the TRIAC can be maintained turned on, but the current cannot be dynamically compensated for the exact amount the TRIAC lacks
Solution Approach 1:
The patent replaces the static constant resistor with a dynamic current adjustment mechanism. The control circuit actively regulates the bleeder current based on real-time detection of the TRIAC's holding current value, enabling precise dynamic compensation rather than fixed current extraction. This allows the system to provide exactly the amount of current needed to maintain TRIAC operation.
Solution Approach 2:
The patent changes the current parameter of the bleeder circuit dynamically based on the detected TRIAC holding current value. Instead of using a fixed resistor value, the system adjusts the bleeder current magnitude according to the specific TRIAC's characteristics, optimizing the current compensation for each different TRIAC type and operating condition.
3Use of energy by moving object
If the input voltage and input current of the illuminator are decreased to lower luminance, then energy can be saved, but the current flowing through the TRIAC becomes smaller than the holding-current value causing misfire and flicker
Solution Approach 1:
The patent extracts current from the input voltage through the bleeder circuit and directs it specifically to the TRIAC to supplement the load current. This separated current path allows the illuminator to operate at lower current for energy saving while the bleeder circuit independently provides the necessary holding current to the TRIAC, preventing misfire and flicker during dimmed operation.
Solution Approach 2:
The bleeder circuit acts as an intermediary element between the input voltage and the TRIAC. It extracts current from the input voltage and delivers it to the TRIAC, serving as a mediator that ensures the TRIAC receives sufficient holding current even when the illuminator's operating current is reduced for energy saving purposes.
Data Source
AI summary
An auto-selecting holding current circuit is applicable to a converter. A primary side of the converter has a Triode for Alternating Current (TRIAC) and a bleeder circuit. The auto-selecting holding current circuit includes a first sensor module, a second sensor module and a reference voltage selecting circuit. The first sensor module detects an input current drop time or an input voltage drop time to output a sense signal. The second sensor module receives a current detector signal and outputs a critical current signal to detect a holding-current value range of the TRIAC. The reference voltage selecting circuit outputs a reference current signal to the bleeder circuit, and the reference current signal corresponds to a holding-current value of the TRIAC. Therefore, the bleeder circuit maintains normal operation of the TRIACs with different holding-current values.