Browsing by Author "Chang, Chun-Kai"

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A new single inductor bipolar multi-output (SIBMO) DC-DC converter driven by constant on-time with improved performance
(2016-06-01)
Chao, Paul C. P.
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Chang, Chun-Kai
;
Cheng, Chun-Kai
;
Trong-Hieu Tran
;
Sauter, Thilo
This study is dedicated to design and realization of a new single inductor bipolar multi-output (SIBMO) DC-DC converter with performance improvement. A bandgap is first designed to offer a stable input bias with capability to work against inevitable input voltage variations for avoiding possible p-n breakdowns. A new drive technique based on constant on-time (COT) is developed for the designed SIBMO with assistance from level shifters and zero current detection circuits to drive MOS devices. The designed circuit is capable of boosting input voltage 2.8 V to four bipolar outputs of +6, -6, +12 and -12 V. The COT proposed herein adopts a new technique of time multiplexing to offer stable multi-outputs with an off-chip inductor for fast switchings. This new COT is different from the conventional pulse width modulation which usually operates with fixed frequencies. The COT is particularly favorable in regards of crossing regulation and high transfer efficiency in cases of unbalanced loads. The proposed SIBMO and COT are applicable to drive systems of organic light-emitting diodes, optical sensors, and portable electronic devices, displays, etc. The designed on-chip SIBMO and COT are fabricated via the TSMC 0.25 A mu m high-voltage CMOS process. Experimental results clearly show the capability of the designed SIBMO chip to offer four bipolar, stabilized output voltages with a total power consumption minimized to 320 mW and the switching frequency varying from 650 to 500 kHz. Most importantly, the maximum efficiency reaches 83.1 %.
A new single inductor bipolar multi-output (SIBMO) DC-DC converter driven by constant on-time with improved performance
(2016-06)
Chao, Paul C. P.
;
Chang, Chun-Kai
;
Cheng, Chun-Kai
;
Trong-Hieu Tran
;
Sauter, Thilo
This study is dedicated to design and realization of a new single inductor bipolar multi-output (SIBMO) DC-DC converter with performance improvement. A bandgap is first designed to offer a stable input bias with capability to work against inevitable input voltage variations for avoiding possible p-n breakdowns. A new drive technique based on constant on-time (COT) is developed for the designed SIBMO with assistance from level shifters and zero current detection circuits to drive MOS devices. The designed circuit is capable of boosting input voltage 2.8 V to four bipolar outputs of +6, -6, +12 and -12 V. The COT proposed herein adopts a new technique of time multiplexing to offer stable multi-outputs with an off-chip inductor for fast switchings. This new COT is different from the conventional pulse width modulation which usually operates with fixed frequencies. The COT is particularly favorable in regards of crossing regulation and high transfer efficiency in cases of unbalanced loads. The proposed SIBMO and COT are applicable to drive systems of organic light-emitting diodes, optical sensors, and portable electronic devices, displays, etc. The designed on-chip SIBMO and COT are fabricated via the TSMC 0.25 A mu m high-voltage CMOS process. Experimental results clearly show the capability of the designed SIBMO chip to offer four bipolar, stabilized output voltages with a total power consumption minimized to 320 mW and the switching frequency varying from 650 to 500 kHz. Most importantly, the maximum efficiency reaches 83.1 %.
A New Single Inductor Bipolar Multiple Output (SIBMO) Boost Converter using Pulse Frequency Modulation (PFM) Control for OLED Drivers and Optical Transducers
(2015)
Chang, Chun-Kai
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Su, Chung-Hsin
;
Kao, Yung-Hua
;
Yu, Ming-Hung
;
Sauter, Thilo
This study proposes a single-inductor bipolar multiple-output (SIBMO) boost converter utilizing pulse frequency (PFM) control for organic light-emitting diode (OLED) drivers and optical transducers. The purpose of the converter designed herein is to provide multiple voltage sources with opposite polarities to meet the requirements of various applications such as OLEDs or optical transducers. The bipolar voltage sources are essential for offering alternating driving voltages to extend the lifetime of OLEDs. The converter boosts the input of 2.8 V to two positive and two negative outputs, i.e., +12 V, +6 V, -12 V, and -6 V. Different from the commonly-used pulse width modulation (PWM), the constant on-time (COT) approach is adopted herein with a dynamic charging algorithm to automatically adjust the operating frequency, thus profiting from less circuit complexity, improvement of cross regulation, and high transfer efficiency in unbalanced load cases. The total maximum output power is 320 mW, as the switching frequency varies from 650 kHz to 0 Hz, and the maximum efficiency reaches 83.1% by simulation. The converter was fabricated by TSMC 0.25 mu m 1P3M high voltage CMOS technology for verification.
A New Single Inductor Bipolar Multiple Output (SIBMO) On-Chip Boost Converter Using Ripple-based Constant On-time Control for LCD Drivers
(2014-01-01)
Chang, Chun-Kai
;
Su, Chung-Hsin
;
Chao, Paul C. -P.
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A constant on-time (COT) single-inductor bipolar multiple-output (SIBMO) on-chip boost converter is proposed for LCD drivers in this study. The converter is designed for biasing some analog and digital circuits fabricated on glass substrates for benefits of extending the life of LCD. These circuits on glass require bipolar high voltages for drive LCDs. The converter boosts the input of 2.8V to two positive outputs and two negative outputs, +12V, +6V,-12V and -6V, respectively. Different from the commonly-used pulse width modulation (PWM), the constant on-time (COT) is adopted herein by a dynamic charging algorithm whose frequency is adapted to the varied output voltage level, thus enjoying the merit of less circuit complexity and a smaller chip area. The COT is in this study further developed to a ripple-based one for achieving applicability even with unbalanced output loads with high efficiency. While total maximum output power is 260mw and the switching frequency varies from 500 kHz to 650 kHz, the maximum efficiency reaches 82.4%. The converter is fabricated by TSMC 0.25 mu m 1P3M high voltage CMOS technology for verification.
A New Single Inductor Bipolar Multiple Output (SIBMO) On-Chip Boost Converter Using Ripple-based Constant On-time Control for LCD Drivers
(2014)
Chang, Chun-Kai
;
Su, Chung-Hsin
;
Chao, Paul C. -P.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A constant on-time (COT) single-inductor bipolar multiple-output (SIBMO) on-chip boost converter is proposed for LCD drivers in this study. The converter is designed for biasing some analog and digital circuits fabricated on glass substrates for benefits of extending the life of LCD. These circuits on glass require bipolar high voltages for drive LCDs. The converter boosts the input of 2.8V to two positive outputs and two negative outputs, + 12V, + 6V, -12V and -6V, respectively. Different from the commonly-used pulse width modulation (PWM), the constant on-time (COT) is adopted herein by a dynamic charging algorithm whose frequency is adapted to the varied output voltage level, thus enjoying the merit of less circuit complexity and a smaller chip area. The COT is in this study further developed to a ripple-based one for achieving applicability even with unbalanced output loads with high efficiency. While total maximum output power is 260mw and the switching frequency varies from 500 kHz to 650 kHz, the maximum efficiency reaches 82.4%. The converter is fabricated by TSMC 0.25 mu m 1P3M high voltage CMOS technology for verification.
A New Small-Sized Pierce Crystal Oscillator Readout with Novel on-Chip All-Digital Temperature Sensing and Compensation
(2014)
Peng, Hsuan-Wen
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Su, Chung-Hsin
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Chao, Paul C. -P.
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Hsieh, Jing-Wen
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Chang, Chun-Kai
This paper presents a 16-MHz digital-controlled crystal oscillator and a time-domain temperature sensor design to achieve a high precision temperature-compensated crystal oscillator in a low-power mobile device. The digital-controlled crystal oscillator is based on Pierce topology with two 8-bit switched-capacitor arrays and the temperature of it is measured by time-domain temperature sensor. For noise reduction, the supply voltages of digital-controlled crystal oscillator and time-domain temperature sensor are regulated at 1.2 V by using two on-chip low-dropout regulators. The proposed circuit design has been successfully fabricated by using TSMC 0.18-mu m CMOS process, where the active area is 0.516 mm(2). The measured start-up time of fabricated 8-bit digital-controlled crystal oscillator is about 0.35 ms and the measured phase noise of 1 kHz offset at 25 degrees C is -119.93 dB/Hz. With temperature compensation, the frequency deviation of it is within +/- 0.08 ppm over -40 degrees C to 85 degrees C. The measured effective temperature resolution of time-domain temperature sensor is 0.45 degrees C/LSB and the measured error is within -6.3 degrees C to 7.1 degrees C at 10 Hz conversion rate. The measured current consumption of chip is about 2 mA.
Achieving Maximum Power Efficiency of a Novel Rectifier Charge Pump by Impedance Matching in an Energy Harvester Suited for Self-Powered Sensors
(2013)
Chao, Paul C. -P.
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Chiang, Chao-Te
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Huang, Tzu-Chia
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Chang, Chun-Kai
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電機工程學系
A new rectifier (AC-DC) charge pump with impedance matching is proposed in this study for maximizing power transfer efficiency in an energy harvester circuitry equipping self-powered sensors. In addition to the rectifier charge pump, there are power management circuits, a low dropout regulator and a battery charger to complete the energy harvester circuitry module for self-power sensors. The proposed circuit is suitable for harvesting the low-frequency vibration energy in portable medical sensors or low-power high-frequency RFID sensors. In the harvester circuit, the rectifier charge pump operated in dual phase is proposed to preform efficient conversion of vibratory AC powers to DC by means of automatic switchings and capacitors. To optimize the charge pump circuit, a charging equivalent model is first derived, where all capacitances are optimized to derive maximum average energy stored in capacitors and then transferred to loadings. The design rules are distilled based on rigorous analysis, and the capacitances are optimized based on the relation between the energy stored in capacitances and inherent electronic properties of the harvester. The chips with optimized capacitances are fabricated by the TSMC 0.35um process for verification. It is shown theoretically and experimentally that implementation of the proposed optimized circuit is able to harvest more power than un-optimized.
Hybrid light-emitting devices by incorporating WO3 nanorod arrays as the electron transport layer and PEIE as the buffer layer
(2018-01-01)
Chang, Chun-Kai
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Wang, Szu-Ping
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Yang, Sheng-Hsiung
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Puaud, Apolline
;
Thien-Phap Nguyen
In this research, we demonstrate novel inverted light-emitting devices based on n-typed tungsten trioxide (WO3) nanostructures. Two different types of WO3 nanostructures, including nanocluster layer (NCL) and nanorod arrays (NAs), were grown on the indium-tin oxide (ITO) substrates by the hydrothermal method. An ultra-thin polyethylenimine ethoxylated (PEIE) layer was deposited on top of WO3 nanostructures as the buffer layer for improving device performance. Inverted devices with the configuration of ITO/WO3 NCL or NAs/PEIE/poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/WO3 film/Au were constructed and evaluated. The best device based on WO3 NAs with height of 300 nm showed a max brightness of 3079 cd/m(2) and current efficiency of 0.22 cd/A. Our observation and results open up new opportunities to fabricate hybrid light-emitting devices. (C) 2017 Elsevier Ltd. All rights reserved.
Improving efficiency of InGaN/GaN multiple quantum well solar cells using CdS quantum dots and distributed Bragg reflectors
(2013-10-01)
Tsai, Yu-Lin
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Lin, Chien-Chung
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Han, Hau-Vei
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Chang, Chun-Kai
;
Chen, Hsin-Chu
This work demonstrates hybrid InGaN/GaN multiple quantum well (MQW) solar cells with enhanced power conversion efficiency using colloidal CdS quantum dots (QDs) and back-side distributed Bragg reflectors (DBRs). CdS QDs can absorb ultraviolet (UV) photons, which are strongly absorbed by indium tin oxide (ITO), and they emit photons with a longer wavelength. This process improves the collection of photon-generated carriers and is known as the luminescence down-shifting (LDS). Accordingly, CdS QDs can compensate for the poor utilization of UV photons in an ITO layer, enhancing the external quantum efficiency (EQE) in the UV range. The DBRs on the back of the solar cells can reflect photons of longer wavelengths back into the absorber layer, increasing the EQE (380-440 nm). The combination of CdS QDs and DBRs results in broadband EQE enhancement, and yields an overall power conversion efficiency that is 20.7% better than that of a reference device without CdS QDs and DBRs. (C) 2013 Elsevier B.V. All rights reserved.
Modal Linewidth Dependent Transmission Performance of 850-nm VCSELs With Encoding PAM-4 Over 100-m MMF
(2017-10-01)
Kao, Hsuan-Yun
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Chi, Yu-Chieh
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Peng, Chun-Yen
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Leong, Shan-Fong
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Chang, Chun-Kai
By changing the transverse-mode spectral linewidth of vertical cavity surface emitting lasers (VCSELs) at 850 nm, the directly encoded four-level pulse amplitude modulation data transmission performance over 100-m-long OM4 multimode fiber (MMF) are demonstrated and compared. The multi-mode VCSEL chip with the largest aperture of 11 mu m reveals the widest spectral linewidth and the highest optical power, but provides the smallest modulation bandwidth to support only 44-and 28-Gb/s data rates for back-to-back (BtB) and 100-m OM4 MMF transmission cases, respectively. By shrinking the aperture size to reduce transverse-mode number, the few-mode VCSEL with the strongest throughput power enables a BtB transmission capacity as high as 52 Gb/s. However, its modal dispersion induced after OM4 MMF transmission inevitably degrade the data rate to 32 Gb/s. In contrast, the single-mode VCSEL with the smallest aperture of 3 mu m reveals the highest modulation bandwidth and negligible modal dispersion to show competitive BtB transmission capacity with that of the few-mode VCSEL. In particular, the single-mode VCSEL successfully achieves a data rate of 34 Gb/s with a power penalty as low as 1.4 dB, after 100-m OM4 MMF transmission.
Novel hybrid light-emitting devices based on MAPbBr(3) nanoplatelets:PVK nanocomposites and zinc oxide nanorod arrays
(2018-01-01)
Wang, Szu-Ping
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Chang, Chun-Kai
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Yang, Sheng-Hsiung
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Chang, Che-Yu
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Chao, Yu-Chiang
In this research, we demonstrate inverted perovskite light-emitting devices (PeLEDs) based on zinc oxide nanorod arrays (ZnO NAs) as the electron transport layer and methylammonium lead bromide nanoplatelets (MAPbBr(3) NPLs) as the emissive material for the first time. The polyethyleneimine ethoxylated (PEIE) was inserted between the ZnO NAs and the MAPbBr(3) NPLs layer to reduce the energy barrier and improve the electron injection efficiency. Besides, different weight ratios of poly(N-vinylcarbazole) (PVK) were blended with MAPbBr(3) NPLs to make evenly dispersed nanocomposite films, thereby enhancing the performance of devices. Meanwhile, the photoluminescence of MAPbBr(3) NPLs:PVK nanocomposite film was increased due to reduced self-quenching and prolonged carrier lifetime. Inverted PeLEDs with the configuration of ITO/PEIE-modified ZnO NAs/MAPbBr(3) NPLs: PVK/TFB/Au were fabricated and evaluated, using TFB as the hole transport layer. The current density of the devices containing PVK matrix was significantly suppressed compared to those without PVK. Herein, the best device revealed a max brightness of 495 cd m(-2) and a low turn-on voltage of 3.1 V that shows potential use in light-emitting applications.
Unified Designs for High Performance LDPC Decoding on GPGPU
(2016-12-01)
Lai, Bo-Cheng Charles
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Lee, Chia-Ying
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Chiu, Tsou-Han
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Kuo, Hsien-Kai
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Chang, Chun-Kai
Modern GPGPU\'s have enabled massively parallel computing with programmability that can exploit the highly parallel nature of LDPC decoding. Previous works customized the design on a GPGPU towards specific execution attributes of a particular LDPC decoding matrix. Supporting different LDPC decoding matrices requires either substantial rework on the current program, or a brand new parallel design. This paper proposes two unified designs that can achieve high performance for both regular and irregular LDPC decoding on a GPGPU. The first design introduces a node-based scheme with a versatile translation array mechanism that can efficiently handle the complex data access patterns of different LDPC decoding matrices. The second design proposes an edge-based parallel paradigm that uses more intuitive data layout. More edges than nodes in a Tanner graph also give the edge-based design higher computation parallelism when there are limited concurrent codewords. With the proposed unified designs, designers can be ignorant of the types of LDPC matrices and achieve high performance LDPC decoding. The experiments on a GTX 470 GPGPU have demonstrated up to 134.56x runtime improvement, when compared with designs on a high-end CPU. The maximum throughput can reach 80.25 Mbps. When compared with the previous customized designs, the proposed systematic designs can reach better performance while relieving the effort of customization.
Virtual-view-based Stereo Video Composition
(2013)
Chang, Chun-Kai
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Hang, Hsueh-Ming
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Given two sets of videos captured by two sets of multiple cameras, we like to combine them to create a new stereo scene with the foreground objects from one set of video and the background from the other set. We address the camera parameter mismatch and camera orientation mismatch problems in this paper. We propose a floor model to adjust the camera orientation. Once we pick up the landing point (of foreground) in the background scene, we need to adjust the background camera parameters (position etc.) to match the foreground object. The depth information is needed in the above calculation. Thus, new background scenes may have to be synthesized based on the calculated virtual camera parameters and the given background pictures. Plausible results are demonstrated using the proposed algorithms.