Dimmable LED Driver SCR Control Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED drivers with electronic transformers face challenges in maintaining minimum load current and achieving accurate dimming for LED lights, often resulting in flickering or strobe effects due to LC resonance and inefficiencies caused by dummy loads.
Innovation Solution
A dimmable LED driver design incorporating a silicon-controlled rectifier (SCR), electronic transformer, and rectifier bridge, with a power stage circuit and input current control circuit that generates a square wave input current during SCR on-time and maintains zero current during off-time, ensuring a constant peak value meets the minimum load current requirement and allows for precise dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large filter capacitor is used in conventional LED drivers, then the circuit can maintain voltage stability, but LC resonance causes uncontrollable current through SCR, resulting in LED strobe effects
Solution Approach 1:
The patent removes the large filter capacitor from the circuit to eliminate the source of LC resonance. Instead of using a capacitor-based filtering approach, the invention employs active current control circuitry to achieve voltage stability without the harmful resonant effects that cause uncontrollable SCR current and LED strobe effects.
Solution Approach 2:
The patent replaces the passive mechanical/electrical filtering system (large filter capacitor) with an active control system. The input current control circuit actively regulates the current waveform to be square-shaped during SCR on-time, substituting the need for large energy-storing capacitors with intelligent control that prevents resonance while maintaining stability.
2Reliability
If a dummy load (resistors) is added to improve SCR controllability, then current controllability improves, but circuit efficiency decreases due to power consumption on the dummy load
Solution Approach 1:
The patent makes the LED load itself serve the dual function of being both the light source and the load that provides necessary current draw during SCR conduction. The control circuit ensures the LED load current meets the minimum load requirement, eliminating the need for separate dummy loads that would waste energy while providing the same controllability benefit.
Solution Approach 2:
The patent makes the LED load multi-functional: it serves as both the primary light-output device and the load that provides necessary current draw for SCR controllability. By controlling the LED current to maintain minimum load requirements during SCR on-time, the system achieves both dimming functionality and reliable SCR operation without energy-wasting dummy loads.
3Reliability
If electronic transformer minimum load current is maintained, then electronic transformer operation is stable, but accurate dimming for LED load becomes difficult to achieve
Solution Approach 1:
The patent employs dynamic control where the input current is actively adjusted during each SCR conduction period. The control circuit generates square-wave current profiles with controlled peak values that adapt to maintain minimum load current requirements while allowing the LED output to be precisely dimmed through SCR triggering angle control, achieving both stability and dimming accuracy simultaneously.
Solution Approach 2:
The patent uses periodic square-wave current pulses during SCR on-time to maintain minimum load current. By delivering controlled current peaks at appropriate intervals during each AC cycle, the system ensures continuous electronic transformer operation while the variable duty cycle and triggering angle enable precise dimming control of the LED load.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures stable operation of the electronic transformer, prevents LED flickering, and enhances circuit efficiency by maintaining a constant LED load current and broad dimming range without the need for a dummy load.
Implementation Method 1
a silicon-controlled rectifier (SCR), an electronic transformer, and a rectifier bridge configured to convert an AC voltage to a DC voltage signal
Implementation Method 2
a power stage circuit configured to receive the DC voltage signal, and to output a constant current to drive an LED load
Implementation Method 3
an input current control circuit configured to receive an input current of the first power stage circuit and the first output voltage, and to generate a first control signal to control the input current as a square wave signal during an on time of the SCR, and the input current is maintained as substantially zero during an off time of the SCR
Data Source
AI summary
Disclosed are dimmable LED driver circuits and methods. A dimmable LED driver can include: an SCR, an electronic transformer, and a rectifier bridge to convert an AC voltage to a DC voltage signal; a power stage circuit that receives the DC voltage signal, and outputs a constant current to drive an LED load, where the power stage circuit includes first and second power stage circuits, the first power stage circuit receiving the DC voltage signal, and generating a first output voltage to the second power stage; and an input current control circuit that receives an input current of the first power stage circuit and the first output voltage, and generates a first control signal to control the input current as a square wave signal during an on time of the SCR, and the input current is substantially zero during an off time of the SCR.