LED Short Circuit Detection via Voltage Differential Thresholding
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Solution Overview
Problem
Detecting short circuit failures in LED chains is challenging due to the subtle changes in voltage, making it difficult to identify defective LEDs in series connections without interrupting the entire chain.
Innovation Solution
A circuit and method that determine the maximum and minimum voltages across series load voltages and compare them with a threshold voltage to detect if the maximum exceeds the minimum by a predefined value, indicating a short circuit condition, allowing for effective fault detection without requiring additional pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LEDs are connected in series to form LED chains to match supply voltages, then the circuit can operate with commonly used supply voltages (12V, 24V, 42V), but detecting short circuit failures becomes difficult because only the defective LED stops radiating without interrupting the current for the whole chain
Solution Approach 1:
The patent segments the LED chain into multiple groups by inserting switching elements (transistors) between series-connected LEDs. Each group can be independently controlled and tested. By activating one group at a time while others remain off, the system can isolate and detect short circuits in specific segments without affecting the entire chain, thus resolving the detection difficulty while maintaining series connection for voltage compatibility
Solution Approach 2:
The patent changes the operational state parameters of LEDs by controlling their on/off status through switching elements. During fault detection, the system transitions from normal operation mode (all LEDs on) to detection mode (groups of LEDs activated sequentially). This parameter change enables voltage measurement across specific segments to identify short circuits, solving the detection problem while preserving the series connection architecture for supply voltage matching
2Reliability
If fault detection is implemented in driver circuits to detect defective LEDs, then reliable operation can be ensured, but the device complexity increases due to additional detection circuitry and control mechanisms
Solution Approach 1:
The patent implements multi-functionality in the driver circuit by integrating fault detection capabilities into the existing LED control architecture. The same switching elements and control logic used for LED dimming and sequencing are also employed for fault detection. This universal approach enables reliable short circuit detection without adding separate dedicated detection circuitry, thus maintaining reliability while minimizing device complexity
Solution Approach 2:
The system performs self-diagnosis by utilizing its own control mechanisms and power supply for fault detection. The driver circuit uses its existing transistors, resistors, and voltage sources to measure segment voltages and identify short circuits. This self-service approach eliminates the need for external detection equipment or additional pins, ensuring reliable fault detection while keeping the circuit design simple and compact
Data Source
AI summary
A method and circuit are described in which a maximum voltage is determined from among a plurality of series load voltages, where each series load voltage of the plurality of series load voltages is a voltage defined by a corresponding series of N loads of a plurality of series of N loads, where N is an integer greater than one. Also, a minimum voltage may be determined from among the plurality of series load voltages. Next, the maximum voltage from among the plurality of series load voltages may be compared with the minimum voltage from among the plurality of series load voltages to make a determination as to whether the maximum voltage from among the plurality of series load voltages exceeds the minimum from among the plurality of series load voltages by a threshold voltage. Then, an indication can be output based on the results of the determination.