Browsing by Author "Lai, Wei-Jen"

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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
;
Chen, Chi-Lin
;
Hsieh, Yu-Chiao
;
Chen, Ke-Horng
;
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.
Low voltage active pressure sensor based on polymer space-charge-limited transistor
(2009-12-21)
Chao, Yu-Chiang
;
Lai, Wei-Jen
;
Chen, Chun-Yu
;
Meng, Hsin-Fei
;
Zan, Hsiao-Wen
Low voltage active pressure sensor is realized by vertically stacking a pressure sensitive rubber on a polymer space-charge-limited transistor. The sensor can be turned on and off by modulating the metal-grid base voltage within the range of 3 V. The output current is irrelevant to the pressure as the sensor is off. As the sensor is turned on, the output current values can be used to monitor the pressure. Reversible pressure sensing characteristics is observed below the pressure of 7.11 psi. The response time of the sensor to the pressure is as short as 22 ms. (C) 2009 American Institute of Physics. [doi:10.1063/1.3266847]
Zero current detection technique for fast transient response in buck DC-DC converters
(2008)
Chen, Chi-Lin
;
Lai, Wei-Jen
;
Liu, Ter-Hsing
;
Chen, Ke-Horng
;
電控工程研究所
A load dependent zero-current detector is proposed in this paper for speeding up the transient response when load current changes from heavy to tight loads. The fast transient control signal determines how long the reversed inductor current according to sudden load variations. At the beginning of load variation from heavy to tight loads, the sensed voltage compared with higher voltage to discharge the overshoot output voltage for achieving fast transient response. Besides, for an adaptive reversed current period, the fast transient mechanism is turned off since the output voltage is rapidly regulated back to the acceptable level. Simulation results demonstrate that the ZCD circuit permits the reverse current flowing back into n-type power MOSFET at the beginning of load variations. The settling time is decreased to about 35 mu s when load current suddenly changes from 500mA to 10 mA.