Low-Overhead Current Generator for LED Lighting Circuits
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Solution Overview
Problem
Conventional LED lighting systems face inefficiencies due to high overhead voltage drops and quiescent current consumption, which degrade system efficiency and scalability, and display poor differential non-linearity (DNL) performance, especially when handling multiple LED strings.
Innovation Solution
A lighting system with a programmable current source using variable resistance elements and feedback circuits that minimize overhead by controlling resistance values, reducing quiescent current consumption and improving DNL performance, while maintaining accurate pulse width modulation (PWM) control, through the use of triode region transistor operation and mixed thermometric and binary coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional IDAC current generators are used for each LED string, then current control is achieved, but overhead voltage drop and power dissipation increase
Solution Approach 1:
Multiple IDAC current generators are merged into a single shared current generator that serves all LED strings. This consolidation eliminates redundant circuitry, reduces total overhead voltage drop, and decreases power dissipation while maintaining precise current control through shared feedback mechanisms.
Solution Approach 2:
A single current generator is designed to serve multiple LED strings simultaneously, making it a universal component. This multi-functional approach reduces the total number of current generators needed, thereby reducing overall power dissipation and overhead voltage drop across the system.
2Ease of operation
If multiple IDAC current generators are used for multiple LED strings, then individual current control is achieved, but device complexity and circuit area increase
Solution Approach 1:
Individual current control for multiple LED strings is achieved by merging multiple IDAC generators into one shared generator with common feedback control. This approach maintains the ability to independently control each LED string's current while significantly reducing circuit complexity and the number of discrete components required.
Solution Approach 2:
A shared feedback mechanism monitors and regulates the current for each LED string individually, enabling precise control without requiring separate feedback circuits for each string. This feedback approach simplifies the overall circuit architecture while maintaining individual string control capability.
3Power
If conventional current generators with saturation region operation are used, then current sourcing is achieved, but overhead voltage drop increases
Solution Approach 1:
The current generator transitions from saturation region operation to triode region operation, changing the operational parameters of the transistor. This parameter change enables the generator to source current with minimal overhead voltage drop, as triode region operation allows for lower voltage operation while maintaining current sourcing capability.
Data Source
AI summary
This application relates to a lighting system comprising a plurality of light emitting diode, LED, circuits, and a power source for providing a drive voltage to the plurality of LED circuits. For each LED circuit, the lighting system comprises a first variable resistance element connected between the respective LED circuit and ground, and a first feedback circuit configured to control a voltage at a first node between the respective LED circuit and the respective first variable resistance element to a first voltage. The lighting system further comprises a current source and a second variable resistance element connected between the current source and ground, wherein each first variable resistance element is configured to attain a resistance value depending on a resistance value attained by the second variable resistance element.