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Guangzhou, China

Liu C.-H.,National Chiao Tung University | Hsieh C.-Y.,National Chiao Tung University | Hsieh Y.-C.,National Chiao Tung University | Tai T.-J.,Richtek Ltd. | Chen K.-H.,National Chiao Tung University
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2010

A successive approximation register (SAR) is utilized to control adaptive off-time order to regulate accurate light-emitting diode (LED) current and improve efficiency of LED driver. The proposed SAR-controlled adaptive off-time technique without the external sensing resistor can sense the current flowing through LEDs during the turning on of the N-type power MOSFET, as well as provide adaptive off-time depending on the input voltage and the numbers of LED, to obtain an accurate LED current. Experimental results show the inductor current ripple is kept within ±15% of the DC current. As a result, line regulation is guaranteed this proposed design. © 2010 IEEE. Source

Lin R.-L.,National Cheng Kung University | Liu S.-Y.,Leadtrend Inc. | Lee C.-C.,Richtek Ltd. | Chang Y.-C.,National Cheng Kung University
IEEE Transactions on Industry Applications | Year: 2013

This paper presents the Taylor series expression based light-emitting-diode (LED) model for the analysis of the LED driver system. In order to precisely describe the nonlinear V-I curve of LEDs, Taylor series can be utilized to express the Shockley equation of LEDs for the derivations of the dc and small-signal equivalent models. Based on the proposed LED models, the LED array with M paralleled strings of N LEDs in series can be constructed. Furthermore, the equivalent resistances of the N × M LED array can be derived. Finally, one LED array with eight paralleled strings of 15 LEDs in series is constructed to verify the equivalent small-signal resistance with the measured results. © 1972-2012 IEEE. Source

Hung C.-Y.,Richtek Ltd. | Hung C.-Y.,Tunghai University | Kao T.-C.,Richtek Ltd. | Kao T.-C.,Tunghai University | And 7 more authors.
Electronics Letters | Year: 2014

A simple scheme is proposed to increase the hold voltage and not change the original trigger voltage of a silicon-controlled rectifier (SCR) to enhance its latch-up immunity without changing the device dimensions. It is found that using the lightly doped P-diffusion instead of the highly doped P+ diffusion as the P emitter of the anode can increase the hold voltage of an SCR. © 2014 The Institution of Engineering and Technology. Source

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