LED Dimming Circuit Reference Control for Voltage Mismatch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multiple strings of light emitting diodes (LEDs) are difficult to balance in terms of power, with voltage binning techniques often resulting in significant voltage differences due to individual LED voltage variations, making uniform dimming or brightening challenging.
Innovation Solution
A balance circuit is employed that generates a reference voltage to control current through a first component string and tracks this current through additional strings using resistors and field effect transistors, ensuring uniform current distribution across all strings, allowing for simultaneous dimming or brightening of LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If voltage binning is employed to equalize LED string voltages, then voltage matching between strings is improved, but significant voltage differences still occur due to cumulative individual LED voltage variations
Solution Approach 1:
The patent implements feedback by measuring the actual voltage of each LED string and using this information to adjust the drive current dynamically. The controller monitors voltage variations and modifies current distribution to compensate for cumulative LED voltage differences, achieving uniform power distribution across all strings despite individual LED variations.
Solution Approach 2:
The system changes the operating parameters by adjusting drive currents dynamically rather than relying on fixed voltage binning. By varying current levels based on real-time voltage measurements, the system compensates for cumulative voltage variations and achieves uniform power distribution across LED strings with different voltage characteristics.
2Device complexity
If individual LED voltage variations are tolerated, then device complexity is reduced, but uniform dimming and brightening across multiple LED strings becomes difficult to achieve
Solution Approach 1:
The patent implements a universal control system that manages multiple LED strings with different voltage characteristics through a single controller. This multi-functional controller adjusts drive currents to different strings based on their individual requirements, enabling uniform dimming and brightening across all strings while accommodating individual LED variations without requiring separate control circuits for each string.
Solution Approach 2:
The system transitions from static voltage binning to dynamic current adjustment. The controller continuously monitors voltage variations and dynamically modifies drive currents to maintain uniform power distribution during dimming and brightening operations, enabling ease of operation despite individual LED voltage differences.
3Manufacturing precision
If tight voltage binning is applied to LED strings, then initial voltage matching is improved, but current distribution uniformity deteriorates due to cumulative voltage variations
Solution Approach 1:
The system uses feedback to monitor actual voltage distribution across LED strings and adjusts drive currents accordingly. Even with tight voltage binning, the feedback mechanism detects cumulative voltage variations and compensates by modifying current distribution, maintaining current uniformity throughout operation despite initial voltage matching efforts.
Solution Approach 2:
The system changes operating parameters by dynamically adjusting drive currents based on real-time voltage measurements. This allows the system to maintain current distribution uniformity even when tight voltage binning is applied, as the current levels are continuously optimized to compensate for cumulative voltage variations across multiple LEDs in each string.
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 that all LED strings are dimmed or brightened evenly, maintaining current ratios within 1% tolerance, regardless of variations in input current, thereby addressing the issue of voltage differences and achieving uniform lighting control.
Implementation Method 1
an operational amplifier which receives the reference voltage at one or more of its inputs and has an output coupled to a gate of the field effect transistor
Implementation Method 2
a field effect transistor having a drain coupled to the second component string, an operational amplifier which receives the reference voltage at one or more of its inputs and has an output coupled to a gate of the field effect transistor
Implementation Method 3
a reference stage having an output node on which a reference voltage is generated to control current through a first component string and a first resistor connected to the first component string
Implementation Method 4
A current through the first component string is uniformly tracked by the tracking current through the second component string
Data Source
AI summary
A balance circuit includes a reference circuit configured to generate current through strings of light emitting diodes (LEDs). The reference circuit includes a first string of LEDs in series coupled to a collector node of a first transistor. A base drive current resistor is connected between the collector node and a base node of the first transistor. A base emitter resistor is connected between the base node and an emitter of the first transistor such that a reference voltage is generated on the base node during operation. Another stage receives the reference voltage to generate a tracking current through a second transistor and a second string of LEDs connected to a base of the second transistor, wherein a current through the first string of LEDs is uniformly tracked by the tracking current through the second string of LEDs.