Minimum Voltage Detector Circuit for LED Strings
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Solution Overview
Problem
Existing minimum voltage detection circuits are limited in their ability to detect the minimum voltage across a large number of LED strings, which can lead to inefficiencies in current matching and voltage regulation, and lack effective fault detection for short or open circuits in multi-string LED applications.
Innovation Solution
A minimum voltage detector circuit utilizing a plurality of voltage comparators with a replica circuit to maintain the output transistor in an active state, allowing for detection of the minimum voltage across multiple LED strings and incorporating fault detection capabilities to identify short or open circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing minimum voltage detection circuits are used, then the circuit structure is simple, but the ability to detect minimum voltage across a large number of LED strings is limited
Solution Approach 1:
The detection circuit is divided into multiple independent voltage comparator modules, each responsible for comparing the voltage of a specific LED string. Each module includes an amplifier and a replica circuit, allowing the system to scale to detect voltages across many LED strings by simply adding more modular units rather than redesigning the entire circuit.
Solution Approach 2:
The voltage comparator modules are designed with universal functionality to handle multiple detection tasks. Each comparator can detect minimum voltage, and the same modular structure supports fault detection for both short circuits and open circuits across different LED strings, making the circuit multi-functional and adaptable to various detection needs.
2Reliability
If voltage comparators are used to detect minimum voltage, then current matching and voltage regulation improve, but the circuit complexity increases
Solution Approach 1:
The use of multiple voltage comparators is justified by segmenting the detection function across independent modular units. Each comparator handles a specific LED string, enabling parallel voltage comparison without requiring complex sequential processing, thus improving reliability through distributed detection while keeping individual module complexity low.
Solution Approach 2:
The voltage comparators provide feedback signals based on voltage comparisons, enabling the system to identify the minimum voltage among multiple LED strings. This feedback mechanism allows for automatic current matching and voltage regulation by comparing actual voltages against reference levels and adjusting accordingly, enhancing system reliability through closed-loop control.
3Reliability
If fault detection capability is added to detect short or open circuits, then system reliability improves, but the device complexity increases
Solution Approach 1:
The same voltage comparator modules that detect minimum voltage are also utilized for fault detection of short and open circuits. By monitoring the output states and comparison results of these universal modules, the system can identify various fault conditions without adding dedicated fault detection hardware, thereby maintaining reliability improvement while minimizing additional complexity.
Solution Approach 2:
The voltage comparator circuit performs self-diagnosis by monitoring its own operation and output states. When a short or open circuit occurs in an LED string, the comparator's voltage comparison function automatically detects the anomaly through its existing voltage sensing and comparison mechanism, enabling fault detection without requiring separate diagnostic circuitry.
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
Enables efficient detection of minimum voltage across a significantly larger number of LED strings, improving current matching and voltage regulation, while also detecting faults such as short or open circuits, thereby enhancing the reliability and efficiency of LED-based backlight systems.
Implementation Method 1
A minimum voltage detector circuit is disclosed. In one embodiment, a circuit includes a plurality of light-emitting diode (LED) strings each having a plurality of series-coupled LEDs. The circuit further includes a minimum voltage detector circuit having a plurality of voltage comparators.
Data Source
AI summary
A minimum voltage detector circuit is disclosed. The circuit includes a plurality of LED strings each having a plurality of series-coupled LEDs. The minimum voltage detector circuit is configured to detect a minimum voltage from among the plurality of LED strings, and also to perform open/short detection among the plurality of LED strings. The minimum voltage detector circuit includes a plurality of voltage comparators and correspondingly coupled replica circuits. Each of the voltage comparators includes an amplifier having a first input coupled to a cathode of a last LED of one of the plurality of LED strings, an output, and a second input coupled to the output. Each voltage comparator further includes a replica circuit coupled to the amplifier. The replica circuit is configured to maintain an output transistor of the amplifier in an active state when the amplifier is in an unbalanced state.