LED Current Control Circuit with Parallel Current Mirrors
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Solution Overview
Problem
Existing LED control circuits face challenges in maintaining consistent current across multiple strings of LEDs connected in parallel, leading to varying brightness levels due to manufacturing variances, which requires multiple ICs and complicates applications.
Innovation Solution
A method and circuit that generates a reference current, uses a current mirror to set matching drive currents through each LED string, and employs a voltage regulator to ensure consistent brightness across all LEDs, allowing a single IC to control multiple LED strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple ICs are used to control multiple LED strings, then current control capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a universal current control IC that can control multiple LED strings through parallel current mirror circuits. The same IC architecture handles any number of LED strings by replicating the current mirror topology, eliminating the need for different ICs for different string counts and reducing overall system complexity.
Solution Approach 2:
The patent divides the current control function into independent parallel current mirror circuits, where each mirror handles one LED string. This segmentation allows the IC to scale to multiple strings without increasing the complexity of individual control paths, as each segment operates independently but identically.
2Manufacturing precision
If multiple ICs are used to control multiple LED strings, then current matching between strings is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple current control functions into a single IC by implementing parallel current mirror circuits within one device. This consolidation maintains precise current matching between all LED strings while reducing the total number of ICs required, thereby lowering manufacturing costs and assembly complexity.
Solution Approach 2:
The patent uses current mirror circuits that replicate the reference current across multiple parallel paths. Each mirror copies the reference current to its corresponding LED string, ensuring identical current levels without requiring separate calibration or multiple expensive ICs, thus achieving precision at lower cost.
3Device complexity
If a single IC controls multiple LED strings, then device complexity is reduced, but maintaining matched current across strings becomes difficult
Solution Approach 1:
The patent employs current mirror circuits that inherently provide feedback mechanisms. The mirror transistors automatically adjust their operation to maintain equal current levels across all parallel LED strings, compensating for variations and ensuring precise current matching without complex external control circuits.
Solution Approach 2:
The patent uses matched transistor pairs in the current mirror circuits where physical manufacturing variations are minimized through careful device selection and pairing. By controlling the transistor parameters (such as threshold voltage and transconductance) to be closely matched, the circuit maintains precise current division ratios across multiple strings despite normal manufacturing tolerances.
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 enables consistent brightness across multiple LED strings using a single integrated circuit, reducing the need for multiple ICs and simplifying applications by maintaining matched currents and brightness levels.
Implementation Method 1
generating an output current based on the first current... the output current is mirrored to generate each load current
Data Source
AI summary
Embodiments of the present invention include circuits and methods for electrical current control. In one embodiment, a regulator provides power to the anode end of a set of LED strings. A current setting circuit derives its current from a current reference and generates multiple matching currents that drive the low side (cathode end) of the set of LED strings. The current setting circuit also contains a feedback signal to the regulator that helps maintain a desired voltage level to the anode end of the LED strings. This embodiment is designed to be expandable and drive any number of LED strings. The present invention may be implemented with a high or low side driver scheme to drive the current. Also, the present invention may be implemented with bipolar, nmos, pmos, or any device that operates as a transistor.