Design and Implementation of a High Efficiency Power Supply of LED Dynamic Display Board

• Main Authors: Yong-chin Lee, 李勇進
• Other Authors: Nan-Ming Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/6jmz4n

碩士 === 國立臺灣科技大學 === 電機工程系 === 99 === 　　The main purpose of this thesis is to investigate and implement a high efficiency power supply for LED dynamic display board. LED driver circuits are designed with improvement of LED voltage feedback circuits. Only one control IC is used in the two power stage structure of the LED power supply. The front-end part of the converter is a boost power factor corrector (PFC). The second power stage is a half-bridge LLC resonant converter. The control method of the second stage uses open loop control. The driving signal of its power switch is driven synchronously with the boost power factor corrector. The half-bridge resonant converter is operated in fixed frequency mode at the first resonant frequency. The power supply can reduce switching loss and conduction loss to achieve high conversion efficiency. Furthermore, the feedback voltage of the output voltage control circuit is taken from the tertiary winding of the LLC converter transformer. This method needs no isolation circuit between primary and secondary windings of the transformer, so that the power supply cost can be reduced. 　　In LED driver circuit design, references [1] proposed the LED voltage feedback control circuit. It is applied to LED display board circuit design. Since the forward voltages are different between red LED and blue or green LED, this research uses two driving circuits to drive R and GB LED separately. Moreover, the voltage feedback circuit is improved. When an LED dynamic display board is under dimming control condition, there was an excess voltage drop of approximately 0.7V. This design reduces the excess voltage and improves the speed response of the voltage feedback circuit so that the buck converter output voltages can provide more appropriate voltages to drive red, green and blue LEDs of the LED dynamic display board to reduce the power loss of it.