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Browsing by Author "Hsieh, Yu-Chiao"

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    High-Efficiency Slope Compensator (HSC) with Input-Independent Load Condition Identification in Current Mode DC/DC Buck Converters
    (2009)
    Lai, Wei-Jen
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    Chen, Chi-Lin
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    Hsieh, Yu-Chiao
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    Chen, Ke-Horng
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    電控工程研究所
    A high-efficiency slope compensator (HSC) is presented to achieve power reduction in current-mode control and provide input-independent load condition identification for mode switch in hybrid PWM/PFM system. That is, according to load condition, an adaptive mode transition can be decided by the HSC circuit and not varied by the variation of input voltage. Therefore, for a hybrid PWM/PFM system, the power conversion efficiency can be kept high over a wide load range. Besides; the pulse-ramp slope compensation technique prevents the current-mode DC-DC converter from having the sub-harmonic oscillation problem and reduces power dissipation of the slope compensator. Simulation results show that the mode transition is accurately decided at the optimum point without being affected by the variation of input voltage. The power conversion efficiency is improved about 5% in PWM/PFM transition region.
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    SAR-Controlled Adaptive Off-Time Technique Without Sensing Resistor for Achieving High Efficiency and Accuracy LED Lighting System
    (2010-06-01)
    Liu, Chao-Hsuan
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    Hsieh, Chun-Yu
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    Hsieh, Yu-Chiao
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    Tai, Ting-Jung
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    Chen, Ke-Horng
    A successive approximation register (SAR) is utilized to control adaptive off-time in 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 in this proposed design.