Browsing by Author "Yang, Chih-Yu"

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A Charge-Recycling Buck-Store and Boost-Restore (BSBR) Technique With Dual Outputs for RGB LED Backlight and Flashlight Module
(2009-08-01)
Hsieh, Chun-Yu
;
Yang, Chih-Yu
;
Chen, Ke-Horng
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A boost converter with buck-store and boost-restore (BSBR) technique fabricated by 0.25 mu m CMOS BCD process can provide different supply voltages to drive series red, green, and blue LEDs in sequence for reducing the power consumption on the constant current generator. The proposed technique not only stores and restores extra energy during the transient time of the reference tracking response to improve the efficiency but also enhances the reference tracking response to greatly reduce load transition time. Experimental results show that the period of reference tracking response can be improved. When the load current is 100 mA, the periods of reference down-tracking and up-tracking are smaller than 10 and 20 mu s, respectively. Furthermore, this technique can also provide a regulated voltage to drive the subblock implemented in the liquid crystal display system. The maximum efficiency of charge recycling is up to 94%, and the maximum efficiency of this boost converter is 94.5%. Experimental results demonstrate fast and efficient reference tracking performance is achieved by the proposed BSBR technique.
A Charge-Reservoir with Buck-Store and Boost-Restore (BSBR) Technique for High Efficient Conversion and Low Cost Solution of RGB LED Display Panels
(2009)
Hsieh, Chun-Yu
;
Yang, Chih-Yu
;
Huang, Ming-Hsin
;
Li, Don-Hwan
;
Chen, Chi-Lin
A boost converter with buck-store and boost-restore (BSBR) technique fabricated by 0.25 mu m CMOS BCD process can provide different supply voltages to drive series RGB LEDs in sequence for reducing the power consumption on the constant current generator. The proposed technique not only stores and restores extra charge during the transient time of the reference tracking response to improve the efficiency but also enhances the reference tracking response to greatly reduce load transition time. Experimental results show that the period of reference-tracking response can be improved. When the load current is 100mA, the periods of reference down-tracking and up-tracking are smaller than lops and 20 mu s, respectively. Furthermore, this technique also can provide a regulated voltage to drive the sub-block implemented in the LCD system. The maximum efficiency of charge recycling is up to 94% and the maximum efficiency of this boost converter is 92.5%. Experimental results demonstrate fast and efficient reference tracking performance is achieved by the proposed BSBR technique.
A Low-Dropout Regulator With Smooth Peak Current Control Topology for Overcurrent Protection
(2010-06-01)
Hsieh, Chun-Yu
;
Yang, Chih-Yu
;
Chen, Ke-Horng
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The proposed low-dropout (LDO) regulator with a smooth peak current control (SPCC) circuit can be simultaneously controlled by using an error amplifier to regulate output voltage and a peak current controller as a means to limit its current level. The SPCC circuit can be switched smoothly between these two control mechanisms by detecting the information of load current and the dropout voltage. Measured results show that overcurrent protection can make the pass device operate as a current source while the load current exceed the peak current level. Moreover, the control mechanism can return to error amplifier control when load current becomes smaller than the limiting current, thus ensuring output voltage to be close to the rated value. Output voltage is stable and varies smaller than 15 mV when a 160 mA load current step or a 2 V supply voltage step is placed on this LDO regulator.
A Novel Wireless Photoplethysmography Blood-Flow Volume Sensor for Assessing Arteriovenous Fistula of Hemodialysis Patients
(2017-12-01)
Chiang, Pei-Yu
;
Chao, Paul C. -P.
;
Tarng, Der-Cherng
;
Yang, Chih-Yu
;
電控工程研究所
A novel blood-flow volume (BFV) sensor is presented for assessing quality of arteriovenous fistula in hemodialysis patients via noninvasive reflectance-type photoplethysmography (PPG). BFV is nowadays in clinic practices evaluated using an ultrasound Doppler monitor, which is expensive, bulky, and can only be operated by well-trained medical personnels. This study is devoted to develop a low-cost, small-sized, portable, and easy-to-use PPG sensor that is capable of continuous measurement of BFV. New designs of front-end analog circuits, signal processing, and an intelligent neural network calibration method are employed to finally achieve high correlation (R-2 = 0.7176), as opposed to the ultrasound Doppler monitor, with the root-mean-squared errors successfully controlled under 289 ml/min.
A Photovoltaic System with Analog Maximum Power Point Tracking and Grid-Synchronous Control
(2012)
Huang, Tzu-Chi
;
Lee, Yu-Huei
;
Du, Ming-Jhe
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Hsieh, Chun-Yu
;
Yang, Chih-Yu
A low cost maximum power point tracking (MPPT) technique is proposed in this paper for high power efficiency in photovoltaic systems to track the maximum power point (MPP). Compared to the various studies of the MPPT topologies, the proposed implementation is achieved by monitoring the power slope conditions of solar panels. The post grid-connected DC-AC inverter helps feedback the transformative power for providing AC power. Experiment results demonstrate the rapid tracking operation of MPP and a high tracking effectiveness of 97.3%.
A Portable, Wireless Photoplethysomography Sensor for Assessing Health of Arteriovenous Fistula Using Class-Weighted Support Vector Machine
(2018-11-01)
Chao, Paul C. -P.
;
Chiang, Pei-Yu
;
Kao, Yung-Hua
;
Tu, Tse-Yi
;
Yang, Chih-Yu
A portable, wireless photoplethysomography (PPG) sensor for assessing arteriovenous fistula (AVF) by using class-weighted support vector machines (SVM) was presented in this study. Nowadays, in hospital, AVF are assessed by ultrasound Doppler machines, which are bulky, expensive, complicated-to-operate, and time-consuming. In this study, new PPG sensors were proposed and developed successfully to provide portable and inexpensive solutions for AVF assessments. To develop the sensor, at first, by combining the dimensionless number analysis and the optical Beer Lambert's law, five input features were derived for the SVM classifier. In the next step, to increase the signal-noise ratio (SNR) of PPG signals, the front-end readout circuitries were designed to fully use the dynamic range of analog-digital converter (ADC) by controlling the circuitries gain and the light intensity of light emitted diode (LED). Digital signal processing algorithms were proposed next to check and fix signal anomalies. Finally, the class-weighted SVM classifiers employed five different kernel functions to assess AVF quality. The assessment results were provided to doctors for diagonosis and detemining ensuing proper treatments. The experimental results showed that the proposed PPG sensors successfully achieved an accuracy of 89.11% in assessing health of AVF and with a type II error of only 9.59%.
Highly Efficient Analog Maximum Power Point Tracking (AMPPT) in a Photovoltaic System
(2012-07-01)
Yang, Chih-Yu
;
Hsieh, Chun-Yu
;
Feng, Fu-Kuei
;
Chen, Ke-Horng
;
電控工程研究所
A compact-size analog maximum power point tracking (AMPPT) technique is proposed in this paper for high power efficiency in the photovoltaic (PV) system. Combining existing MPPT approaches, we present a fast and accurate tracking performance. Here, a wide-range current multiplier, which tracks the maximum power point (MPP) in the solar power system, is implemented to detect the power slope condition of the solar panel. Experimental results show that the proposed technique can rapidly track the MPP with a high tracking accuracy of 97.3%. Furthermore, the proposed system can connect to the grid-connected inverter to supply ac power.
Machine Learning Classification for Assessing the Degree of Stenosis and Blood Flow Volume at Arteriovenous Fistulas of Hemodialysis Patients Using a New Photoplethysmography Sensor Device
(2019-08-01)
Chiang, Pei-Yu
;
Chao, Paul C. -P.
;
Tu, Tse-Yi
;
Kao, Yung-Hua
;
Yang, Chih-Yu
The classifier of support vector machine (SVM) learning for assessing the quality of arteriovenous fistulae (AVFs) in hemodialysis (HD) patients using a new photoplethysmography (PPG) sensor device is presented in this work. In clinical practice, there are two important indices for assessing the quality of AVF: the blood flow volume (BFV) and the degree of stenosis (DOS). In hospitals, the BFV and DOS of AVFs are nowadays assessed using an ultrasound Doppler machine, which is bulky, expensive, hard to use, and time consuming. In this study, a newly-developed PPG sensor device was utilized to provide patients and doctors with an inexpensive and small-sized solution for ubiquitous AVF assessment. The readout in this sensor was custom-designed to increase the signal-to-noise ratio (SNR) and reduce the environment interference via maximizing successfully the full dynamic range of measured PPG entering an analog-digital converter (ADC) and effective filtering techniques. With quality PPG measurements obtained, machine learning classifiers including SVM were adopted to assess AVF quality, where the input features are determined based on optical Beer-Lambert's law and hemodynamic model, to ensure all the necessary features are considered. Finally, the clinical experiment results showed that the proposed PPG sensor device successfully achieved an accuracy of 87.84% based on SVM analysis in assessing DOS at AVF, while an accuracy of 88.61% was achieved for assessing BFV at AVF.
Observing topotactic phase transformation and resistive switching behaviors in low power SrCoOx memristor
(2020-06-01)
Lo, Hung-Yang
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Yang, Chih-Yu
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Huang, Guan-Ming
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Huang, Chih-Yang
;
Chen, Jui-Yuan
Recently, complex oxides have been shown to be promising candidate in dielectric materials of resistive random access memory (RRAM). However, the detailed switching information of complex oxide RRAM is still insufficient, and direct observation of the whole switching process is required to figure out the mechanism. In this study, we deposited SrCoOx (SCO) on a niobium-doped SrTiO3 substrate as the dielectric layer via pulsed laser deposition (PLD). The novel SCO device possesses excellent RRAM properties, high cycling endurance, a long data retention time, and uniform distributions of the high resistance state (HRS) and low resistance state (LRS) resistance and Set/Reset voltage. Furthermore, the switching mechanism was investigated by using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), which showed that the switching behavior resulted from the topotactic phase transformation. In addition, the whole switching process was observed through in situ TEM, and the results strengthened the findings of the ex situ experiment. The discussion of this switching behavior provides support for a novel aspect of the RRAM switching mechanism and also a new option for the dielectric material in RRAM.
Quality Evaluation via PPG on the AVFs of Hemodialysis Patients Based on Both Blood Flow Volume and Degree of Stenosis
(2019-01-01)
Chiang, Pei-Yu
;
Chao, Paul C. -P.
;
Tu, Tse-Yi
;
Kao, Yung-Hua
;
Yang, Chih-Yu
The classifier of support vector machine (SVM) learning for assessing quality of arteriovenous fistula (AVF) at hemodialysis (HD) patients using a new photoplethysmography (PPG) sensor are presented in this work. Based on current medical standard, there are two important indices for assessing AVF quality, the blood flow volume (BFV) and the degree of stenosis (DOS). In current clinical practice, BFV and DOS of AVFs are assessed by using an ultrasound Doppler machine, which is bulky, expensive, hard-to-use and time-consuming. Therefore, a new PPG sensor module is designed to provide patients and doctors an inexpensive and small-sized solution to assess AVF quality. The readout of the sensor is successfully optimized to increase the signal to noise ratio (SNR) and reduce the environment interference, the readout circuitries are designed to fit the full dynamic range of analog-digital converter (ADC) and to filter out the noise. To assess quality of AVF, three different machine learning classifiers are developed, where the input features are selected based on optical Beer Lambert's law and hemodynamic model. Finally, the clinical experiment results show that the proposed PPG sensor successfully achieves an accuracy of 87.838% in assessing AVF quality based on satisfactory DOS and BFV measured.
The Anastomotic Angle of Hemodialysis Arteriovenous Fistula Is Associated With Flow Disturbance at the Venous Stenosis Location on Angiography
(2020-07-23)
Yang, Chih-Yu
;
Li, Ming-Chia
;
Lan, Chien-Wen
;
Lee, Wang-Jiun
;
Lee, Chen-Ju
The juxta-anastomotic stenosis of an arteriovenous fistula (AVF) is a significant clinical problem in hemodialysis patients with no effective treatment. Previous studies of AV anastomotic angles on hemodynamics and vascular wall injury were based on computational fluid dynamics (CFD) simulations using standardized AVF geometry, not the real-world patient images. The present study is the first CFD study to use angiographic images with patient-specific outcome information, i.e., the exact location of the AVF stenotic lesion. We conducted the CFD analysis utilizing patient-specific AVF geometric models to investigate hemodynamic parameters at different locations of an AVF, and the association between hemodynamic parameters and the anastomotic angle, particularly at the stenotic location. We analyzed 27 patients who used radio-cephalic AVF for hemodialysis and received an angiographic examination for juxta-anastomotic stenosis. The three-dimensional geometrical model of each patient's AVF was built using the angiographic images, in which the shape and the anastomotic angle of the AVF were depicted. CFD simulations of AVF hemodynamics were conducted to obtain blood flow parameters at different locations of an AVF. We found that at the location of the stenotic lesion, the AV angle was significantly correlated with access flow disturbance (r= 0.739;p< 0.001) and flow velocity (r= 0.563;p= 0.002). Furthermore, the receiver operating characteristic (ROC) curve analysis revealed that the AV angle determines the lesion's flow disturbance with a high area under the curve value of 0.878. The ROC analysis also identified a cut-off value of the AV angle as 46.5 degrees, above or below which the access flow disturbance was significantly different. By applying CFD analysis to real-world patient images, the present study provides evidence that an anastomotic angle wider than 46.5 degrees might lead to disturbed flow generation, demonstrating a reference angle to adopt during the anastomosis surgery.
Theoretical developments and clinical experiments of measuring blood flow volume (BFV) at arteriovenous fistula (AVF) using a photoplethysmography (PPG) sensor
(2018-11-01)
Chiang, Pei-Yu
;
Chao, Paul C. -P.
;
Yang, Chih-Yu
;
Tarng, Der-Cherng
;
電子工程學系及電子研究所
A new theoretical developments of measuring blood flow volume at arteriovenous fistula (AVF) using a photoplethysmography (PPG) sensor is presented in this work. The mathematical equation is derived under the practical perspective, aiming at applying to small-size, portable, inexpensive and easy-to-use PPG sensor, in order to replace bulky, expensive Doppler machines which is the commonly used instruments for accessing AVF noninvasively nowadays. Furthermore, a new, portable and wireless PPG sensor with ambient light compensation and motion artifact detection, is designed for performing clinical validation of the proposed equation. After neural network calibration with the gold standard, dilution concentration sensor, the experiment result reveals that the PPG sensors implementing the proposed equation successfully achieve much higher correlation (R-2=0.8064) and much lower error (RMSE=171.68ml/min, MAPE=15.84%) compared to the commercial Doppler machine and other previous works.