Non-Inductive LED Driver with Triac Dimming Feedback
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Solution Overview
Problem
Conventional AC dimming circuits for LED lighting systems suffer from flickering, high energy waste, and increased size and cost due to the use of inductive components, which are unsuitable for low current LEDs, leading to inefficient and unreliable dimming performance.
Innovation Solution
A non-inductive dimmable semiconductor lamp driver using a triac dimming circuit with a full wave diode bridge and two closed-loop feedback control systems to regulate the luminance and holding current, eliminating flickering and reducing energy waste, while maintaining a compact size and low cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional converter circuitry with inductive elements is used for high current LEDs, then the operating voltage can be brought down from line voltage, but the circuit size increases and reliability decreases due to bulky inductive components
Solution Approach 1:
The patent removes inductive elements (energy storage inductors) from the converter circuitry, replacing them with capacitive energy storage. This extraction of the problematic inductive component directly reduces circuit size and improves reliability while maintaining the voltage conversion function through a different technical approach.
Solution Approach 2:
The patent changes the fundamental parameter of energy storage from inductive (magnetic field) to capacitive (electric field). This parameter change allows the same voltage conversion function to be achieved without bulky inductors, thereby reducing circuit size and component count.
2Power
If conventional converter circuitry is used in triac-dimmed circuits, then voltage conversion is achieved, but the circuit draws no current at some portions of power line cycle causing unacceptable lamp pulsing and flickering
Solution Approach 1:
The patent implements feedback control mechanisms that monitor the current draw and adjust the converter operation to ensure continuous current flow through the triac dimmer. This feedback ensures the holding current requirement is met throughout the entire power line cycle, eliminating the pulsing and flickering that occurs with conventional open-loop converter designs.
Solution Approach 2:
The patent ensures continuous current draw from the power line by implementing control logic that prevents the converter from stopping operation during portions of the AC cycle. This continuity of useful action maintains the holding current through the triac, ensuring stable dimming operation without flicker.
3Power
If conventional converter circuitry is used, then voltage conversion is achieved, but peak current draw is high with high total harmonic distortion and low power factor limiting the number of LED lamps that can be connected
Solution Approach 1:
The patent employs periodic switching action with controlled duty cycles to shape the current draw waveform. By using pulse-width modulation or similar periodic control techniques, the converter draws current in a more sinusoidal pattern that reduces harmonic distortion and improves power factor, allowing more lamps to be connected to the same dimmer circuit.
4Loss of energy
If low current LEDs are used with a capacitor in the driver circuit to smooth rectifier output, then energy efficiency is improved, but the capacitor causes the lamp to draw insufficient holding current causing unacceptable flicker
Solution Approach 1:
The patent uses dynamic control of the converter circuit to adjust its operation based on real-time conditions. The converter dynamically modulates its current draw to simultaneously maintain capacitor charging (for efficiency) and ensure sufficient holding current flow through the triac, preventing the flicker problem that occurs with static capacitor-only designs.
Data Source
AI summary
An inductorless LED driver powers a string of low current LEDs. A phase controlled triac dimmer, serially connected to a full-wave rectifier circuit, performs as an LED current and triac holding current control element. The output of the full-wave rectifier circuit is divided into two circuit paths; the first path provides power to drive a string of serially-connected low-current LEDs, and the second path connects to a dynamic load, which supplies a holding current that flows through the triac dimmer. There are two feedback control systems; the first regulates the luminance of the LEDs; the second regulates the triac holding current to eliminate lamp flicker.