Series-Connected Current Sources for LED Voltage Management
Solution Overview
Problem
Existing solid-state lighting systems face challenges in efficiently controlling current through LED strings due to voltage deviations caused by component tolerances and temperature variations, which can exceed the voltage ratings of individual current sources, limiting their modular use across various LED voltage levels.
Innovation Solution
The implementation of series-connected current source circuits in parallel with LED strings, coupled with a voltage control circuit that adjusts current reference signals nonlinearly and uses voltage limiters such as diodes to manage voltages across the current sources, ensuring consistent current levels and preventing voltage exceedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If series-connected current sources are used to drive long LED strings with high forward voltages, then the ability to drive high-voltage LED strings is improved, but the voltage across individual current sources may exceed their voltage ratings
Solution Approach 1:
The LED string is divided into multiple segments, each driven by a separate current source. By connecting current sources in series, the system can handle higher total voltages while each individual current source operates within its voltage rating. The voltage control circuit further segments the voltage control function across multiple operational amplifiers, each managing a portion of the total voltage.
Solution Approach 2:
The system dynamically adjusts the reference current parameters based on the actual voltage conditions across each current source. The voltage control circuit monitors voltage drops and modifies current reference signals accordingly, allowing the system to adapt to varying voltage conditions and prevent any single current source from exceeding its voltage rating.
2Reliability
If voltage control circuits are added to manage voltages across current sources, then voltage rating compliance is improved, but the system complexity increases
Solution Approach 1:
The voltage control circuit implements feedback by monitoring the voltage across each current source and adjusting the reference current signal accordingly. Operational amplifiers compare the actual voltage with a reference voltage and generate correction signals to maintain voltage within acceptable ranges, creating a closed-loop control system that automatically compensates for voltage deviations.
Solution Approach 2:
The voltage control circuit acts as an intermediary between the power supply and the current sources. It processes voltage information and transforms it into appropriate current reference signals, mediating the interaction between voltage constraints and current control requirements without requiring direct modification of the current source circuits themselves.
3Stability of the object's composition
If current reference signals are adjusted nonlinearly based on voltages, then current consistency across current sources is improved, but the control circuit complexity increases
Solution Approach 1:
The system replaces complex mechanical or manual adjustment mechanisms with electronic voltage-controlled current adjustment. By using operational amplifiers and voltage-dependent current sources, the system achieves nonlinear current adjustment through electronic means, which is more precise and easier to control than mechanical alternatives.
Solution Approach 2:
The reference current parameters are dynamically changed based on voltage conditions. The system transforms voltage information into corresponding current adjustments through the voltage control circuit, allowing nonlinear adjustment of current references to maintain consistency across series-connected current sources operating under different voltage conditions.
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 allows for the efficient driving of long LED strings with high forward voltages without exceeding component voltage ratings, enabling modular use of current sources tailored to the LED string characteristics, thereby improving energy efficiency and extending the lifespan of LED lighting systems.
Implementation Method 1
The voltage control circuit may include respective voltage limiters coupled across respective ones of the current control circuits. The voltage limiters may include, for example, respective diodes coupled across respective ones of the current control circuits.
Data Source
AI summary
An apparatus includes a plurality of series-connected current control circuits configured to control a current therethrough responsive to at least one current reference signal and to be coupled in parallel with a load, such as a string of LEDs. The apparatus further includes a voltage control circuit configured to control respective voltages across respective ones of the current control circuits. In some embodiments, the voltage control circuit may be configured to individually adjust responses of the current control circuits responsive to the voltages across the current control circuits. In further embodiments, the voltage control circuit may include respective voltage limiters coupled across respective ones of the current control circuits.