A Simple Short Detection and Current Regulation Circuit for LED Driving Circuit

Background/Objectives: LED short and current imbalance problems generate the over currents in the LED strings and they damage the LED back light system. To solve these problems, this paper proposes a new simple short detection and current regulation circuit for LED driving circuit. Methods/Statistical analysis: The proposed circuit is composed of a bipolar junction transistor (BJT), anop-amp, three resistors, a capacitor, and two diodes. It can reduce the current imbalance among the LED string by using the negative feedback technique, and protect a LED driving circuit and LEDs from a LED short problem by controlling the BJT operation. Findings: To verify the analysis and effectiveness of the proposed circuit, it was tested on three LED strings by using the PSIM simulator. In simulation, it reduced the current deviation among LED strings from 33 % to~ 0 %, and protected the LED driving circuit and LEDs from a LED short problem. Application/Improvements: The proposed circuit has the simpler structure and fewer components than the existing LED short circuits.