| Title |
A Novel LED Short Detection Method for LED Driving Circuit |
| DOI |
http://doi.org/10.5207/JIEIE.2020.34.4.045 |
| Keywords |
Current Regulation; LED Driving Circuit; LED Short Detection; LED String |
| Abstract |
If some LEDs are shorted, overcurrent flows through an LED string consisting of multiple LEDs connected in series. In the LED driving circuit, a current regulator with semiconductor devices such as transistors can protect overcurrent but it generates heat in semiconductor devices, which can damage the LED driving circuit and LED string. In this paper, a novel LED short detection circuit is proposed to solve the LED short problem. The proposed circuit consists of an comparator and a MOSFET and operates in combination with a current regulator. It detects when the LED is shorted and then opens the transistor in current regulator so that the LED current does not flow. To verify the operation and effectiveness of the proposed circuit, a prototype of current regulator and short detection circuit was fabricated and tested by connecting to three LED strings. At LED diving voltage of 18V, The LED currents of all LED strings were 38.7mA∼39.1mA by the constant current operation of current regulators. When a LED is shorted in any LED string and the proposed circuit is not used, the collector-emitter voltage of the transistor in the current regulator was increased to 4.23V and the power consumption of 164.5mW is generated in the transistor. However, when using the proposed circuit, it protects the LED string and LED driving circuit by opening the transistor so that the LED current does not flow. |