Browsing by Author "Chou, Po-Chien"

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A Novel Seesaw Swivel Actuator Design and Fabrication
(2010-07-01)
Chou, Po-Chien
;
Lin, Yu-Cheng
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
Many small form factor optical pickup heads based on the swing arm design utilize piezoelectricity or slim plate of metal to perform focusing action. The seesaw type actuator is a new driving mechanism used for swiveling the entire optical pickup heads devices. The configuration of the seesaw swivel actuator has unique features including a rotary actuator for coarse and fine tracking and a seesaw arm for swiveling along a pivot instead of a hinge to permit a tilt focus movement. In this paper, a biaxial voice coil motor (VCM) combining the swing type tracking VCM and seesaw type focusing VCM in the rear of the swing arm is proposed. This seesaw swing arm actuator is fabricated and evaluated in dynamic experiments. The performance of the biaxial VCM is verified through simulation by finite-element methods, and the effectiveness is confirmed by experimental procedures and parametric design optimization.
Adaptive ZPETC Method for Dual-Stage Actuator Controller Design In Miniaturized Optical Disc Drive
(2008)
Cheng, Stone
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Chou, Po-Chien
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機械工程學系
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Department of Mechanical Engineering
A swing-arm/PZT dual-stage actuator is designed to provide high performance solution to realize precise tracking and focusing operation of miniaturized optical disc drive (mini-ODD). Because of its dual-stage mechanical characteristics can perform the focusing action smoother and more precise for better fault and error tolerance, the servo system to control such a dual-stage system tends to be more effective than a conventional single-stage ODD system. However, it is not enough to restrain the unwanted outside disturbance. Therefore, the zero phase error tracking controller (ZPETC), as proposed by Tomizuka (1987), which is very sensitive to improve the modeling error in motion control is used for this dual-stage miniaturized actuator. This paper presents an adaptive ZPETC method in dual-stage actuator design to achieve better focusing performance.
All GaN-on-Si High Power Module Design and Performance Evaluation
(2013)
Cheng, Stone
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Wang, Chieh-An
;
Chou, Po-Chien
;
Chieng, Wei-Hua
;
Chang, Edward Yi
This paper presents a 270-V, 56-A GaN power module with three AlN substrates are prepared for the module. Each substrate is composed of three parallel connected GaN chips which incorporates six 2-A AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) cells. The substrate layout inside the module is designed to reduce package parasitic. The devices are wire-bonded in parallel connection to increase the power rating. The packaged GaN HEMTs exhibit the pulsed drain current of 0.435 A/mm. Both DC and pulsed current-voltage (ID-VDS) characteristics are measured for different connection and sizes of devices, at various of power densities, pulse lengths, and duty factors. The other static parameters like threshold voltage and leakage currents were extracted to show how these parameters would scale as the devices are paralleled. Performance of multiple chip GaN power module package is studied. Experimental results demonstrated the ability to parallel nine GaN HEMTs die together and to verify the current sharing during the dynamic switching to attain high-current capacities.
Bias- and Temperature-Assisted Trapping/De-trapping of R-ON Degradation in D-mode AlGaN/GaN MIS-HEMTs on a Si substrate
(2017-01-01)
Zhang, Jin-Ming
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Hsieh, Ting-En
;
Wu, Tian-Li
;
Chen, Szu-Hao
;
Chen, Shi-Xuan
In this study, we investigate the R-ON degradation in D-mode AlGaN/GaN MIS-HEMTs on a Si substrate via an accelerated step stress at different temperatures. We have observed a three-phase R-ON degradation behavior, which is highly correlated with a drain bias and back gate bias. First, the R-ON degradation increases till a peak value when the drain bias increases. Second, when the drain bias increases further, the R-ON degradation is reduced. Third, the R-ON degradation slowly increases again. R-ON degradation is characterized with different temperatures, the results show that 1) high temperature leads to a smaller R-ON degradation compared to the result at room temperature and 2) high temperature shifts the peak of the R-ON degradation at a lower drain bias. A possible mechanism that the trapping and de-trapping could occur due to the high temperature and high drain bias is proposed to explain the observed results.
Channel temperature measurement in hermetic packaged GaN HEMTs power switch using fast static and transient thermal methods
(2017-08-01)
Chen, Szu-Hao
;
Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
A GaN-based power device is a superior component for high-frequency and high-efficiency applications and especially for applications that involve megahertz power conversion. In this work, a fast process of static thermal resistance (R (th)) and transient thermal impedance (Z (th)) measurements are made and analyzed to determine the thermal characteristics of the channel temperature of a hermetically packaged GaN power device. Five temperature-sensitive parameters (TSPs) are measured at temperatures from 20 to 160 A degrees C. Measurements and statistical analyses included variations with temperature of on-resistance (R (on)), saturation drain current (I (Dsat)), drain conductance (g (d)), threshold voltage (V (th)), and knee voltage (V (knee)). The statistical analyses revealed the relationships between the heating curve parameter (R (on)) and the cooling curve parameters (V (knee), I (Dsat), g (d), and V (th)). The average thermal resistance values are extracted as follows: Maximum R (th) is 2.99 A degrees C W-1, minimum R (th) is 2.92 A degrees C W-1, and the variation among the five TSPs is < 3%. Conventional optical-based techniques such as infrared (IR) and micro-Raman thermography are destructive to packaged devices. Therefore, this study developed the two reliable and fast non-destructive methods for estimating channel temperature with the following features: (1) They elucidate static and transient characteristics; (2) they involve heating and cooling; and (3) they evaluate transient thermal impedance (TTI) and safe operating area (SOA). The heating curve method has advantages over cooling curve method in terms of capturing time (40 vs. 400 s, respectively), and a lower power excitation is required to obtain the transient channel temperature response.
Chunk-based Resource Allocation Under User Rate Constraints in Multiuser MIMO-OFDM Systems
(2012-01-01)
Chou, Po-Chien
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Ma, Chun-Ying
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Huang, Chia-Chi
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電信工程研究所
;
Institute of Communications Engineering
In multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MU MIMO-OFDM) systems, the communication resource needs to be efficiently allocated on subcarriers such that the quality-of-service (QoS) of each user can be satisfied. A low complexity chunk-based resource allocation algorithm with low signaling overhead is proposed to minimize the total transmit power under the constraint of each user's data rate. The channel estimation error is considered in the resource allocation problem. Simulation results show that the performance degradation with respect to subcarrier-based water-filling method is small and the effect of channel estimation error is negligible. Meanwhile, computation complexity is nearly in the same order and signaling overhead is reduced.
Comprehensive dynamic on-resistance assessments in GaN-on-Si MIS-HEMTs for power switching applications
(2018-05-01)
Chou, Po-Chien
;
Hsieh, Ting-En
;
Cheng, Stone
;
del Alamo, Jesus A.
;
Chang, Edward Yi
This study comprehensively analyzed the reliability of trapping and hot-electron effects responsible for the dynamic on-resistance (Ron) of GaN-based metal-insulator-semiconductor high electron mobility transistors. Specifically, this study performed the following analyses. First, we developed the on-the-fly Ron measurement to analyze the effects of traps during stress. With this technique, the faster one (with a pulse period of 20 ms) can characterize the degradation; the transient behavior could be monitored accurately by such short measurement pulse. Then, dynamic Ron transients were investigated under different bias conditions, including combined off state stress conditions, back-gating stress conditions, and semi-on stress conditions, in separate investigations of surface-and buffer-, and hot-electron-related trapping effects. Finally, the experiments showed that the Ron increase in semi-on state is significantly correlated with the high drain voltage and relatively high current levels (compared with the off-state current), involving the injection of greater amount of hot electrons from the channel into the AlGaN/insulator interface and the GaN buffer. These findings provide a path for device engineering to clarify the possible origins for electron traps and to accelerate the development of emerging GaN technologies.
Design and characterization of a 200 V, 45 A all-GaN HEMT-based power module
(2013-11-03)
Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
Emerging gallium nitride (GaN)-based high electron mobility transistor (HEMT) technology has the potential to make lower loss and higher power switching characteristics than those made using traditional silicon (Si) components. This work designed, developed, and tested an all-GaN-based power module. In a 200 V, 45 A module, each switching element comprises three GaN chips in parallel, each of which includes six 2.1 A AlGaN/GaN-on-Si HEMT cells. The cells are wire-bonded in parallel to scale up the power rating. Static I-D-V-DS characteristics of the module are experimentally obtained over widely varying base plate temperatures, and a low on-state resistance is obtained at an elevated temperature of 125 degrees C. The fabricated module has a blocking voltage exceeding 200 V at a reverse-leakage current density below 1 mA/mm. Two standard temperature measurements are made to provide a simple means of determining mean cell temperature in the module. Self-heating in AlGaN/GaN HEMTs is studied by electrical analysis and infrared thermography. Electrical analysis provides fast temperature overviews while infrared thermography reveals temperature behavior in selected active regions. The current distribution among cells was acceptable over the measured operating temperature range. The characterization of electrical performance and mechanical performance confirm the potential use of the packaged module for high-power applications. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
Enhanced lateral heat dissipation packaging structure for GaN HEMTs on Si substrate
(2013-03-01)
Cheng, Stone
;
Chou, Po-Chien
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Chieng, Wei-Hua
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Chang, E. Y.
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機械工程學系
This work presents a technology for packaging AlGaN/GaN high electron mobility transistors (HEMTs) on a Si substrate. The GaN HEMTs are attached to a V-groove copper base and mounted on a TO-3P leadframe. The various thermal paths from the GaN gate junction to the case are carried out for heat dissipation by spreading to protective coating; transferring through the bond wires; spreading in the lateral device structure through the adhesive layer, and vertical heat spreading of silicon chip bottom. Thermal characterization showed a thermal resistance of 13.72 degrees C/W from the device to the TO-3P package. Experimental tests of a 30 mm gate-periphery single chip packaged in a 5 x 3 mm V-groove Cu base with a 100 V drain bias showed power dissipation of 22 W. (c) 2012 Elsevier Ltd. All rights reserved.
Enhancement of Optical Adaptive Sensing by Using a Dual-Stage Seesaw-Swivel Actuator with a Tunable Vibration Absorber
(2011-05-01)
Chou, Po-Chien
;
Lin, Yu-Cheng
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
Technological obstacles to the use of rotary-type swing arm actuators to actuate optical pickup modules in small-form-factor (SFF) disk drives stem from a hinge's skewed actuation, subsequently inducing off-axis aberrations and deteriorating optical quality. This work describes a dual-stage seesaw-swivel actuator for optical pickup actuation. A triple-layered bimorph bender made of piezoelectric materials (PZTs) is connected to the suspension of the pickup head, while the tunable vibration absorber (TVA) unit is mounted on the seesaw swing arm to offer a balanced force to reduce vibrations in a focusing direction. Both PZT and TVA are designed to satisfy stable focusing operation operational requirements and compensate for the tilt angle or deformation of a disc. Finally, simulation results verify the performance of the dual-stage seesaw-swivel actuator, along with experimental procedures and parametric design optimization confirming the effectiveness of the proposed system.
Enhancement of PZT embedded swing arm actuator using integrated read/write performance and actuation
(2012-04-01)
Lin, Yu-Cheng
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Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
The current technological challenges associated with the rotary-type seesaw arm actuator for small-form-factor (SFF) disk drives are the small skew focusing, which causes off-axis aberrations and reduces optical quality. This article develops a novel design for a seesaw arm actuator and suspension assembly that is based on a micro-PZT actuator to position pickup head. Dual-stage actuation relaxes the dynamic requirement on the focusing stroke. The proposed actuator with a tilt-compensation mechanism uses a PZT bender to drive pickup head focusing. This combined system, optical module and dual stage actuator, is effectively self-aligned the optical axis for read/write performance in both experiment and simulation result. Finite element modeling and dynamic measurements reveal significant improvements in the actuator bandwidth with and without micro-PZT actuator compensation.
Evaluation and Reliability Assessment of GaN-on-Si MIS-HEMT for Power Switching Applications
(2017-02-01)
Chou, Po-Chien
;
Chen, Szu-Hao
;
Hsieh, Ting-En
;
Cheng, Stone
;
del Alamo, Jesus A.
This paper reports an extensive analysis of the physical mechanisms responsible for the failure of GaN-based metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs). When stressed under high applied electric fields, the traps at the dielectric/III-N barrier interface and inside the III-N barrier cause an increase in dynamic on-resistance and a shift of threshold voltage, which might affect the long term stability of these devices. More detailed investigations are needed to identify epitaxy- or process-related degradation mechanisms and to understand their impact on electrical properties. The present paper proposes a suitable methodology to characterize the degradation and failure mechanisms of GaN MIS-HEMTs subjected to stress under various off-state conditions. There are three major stress conditions that include: V-DS = 0 V, off, and off (cascode-connection) states. Changes of direct current (DC) figures of merit in voltage step-stress experiments are measured, statistics are studied, and correlations are investigated. Hot electron stress produces permanent change which can be attributed to charge trapping phenomena and the generation of deep levels or interface states. The simultaneous generation of interface (and/or bulk) and buffer traps can account for the observed degradation modes and mechanisms. These findings provide several critical characteristics to evaluate the electrical reliability of GaN MIS-HEMTs which are borne out by step-stress experiments.
Evaluation of thermal performance of all-GaN power module in parallel operation
(2014-09-05)
Chou, Po-Chien
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Cheng, Stone
;
Chen, Szu-Hao
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交大名義發表
;
機械工程學系
This work presents an extensive thermal characterization of a single discrete GaN high-electron-mobility transistor (HEMT) device when operated in parallel at temperatures of 25 degrees C-175 degrees C. The maximum drain current (I-D (max)), on-resistance (R-ON), pinch-off voltage (V-p) and peak transconductance (g(m)) at various chamber temperatures are measured and correlations among these parameters studied. Understanding the dependence of key transistor parameters on temperature is crucial to inhibiting the generation of hot spots and the equalization of currents in the parallel operation of HEMTs. A detailed analysis of the current imbalance between two parallel HEMT cells and its consequential effect on the junction temperature are also presented. The results from variations in the characteristics of the parallel-connected devices further verify that the thermal stability and switching behavior of these cells are balanced. Two parallel HEMT cells are operated at a safe working distance from thermal runaway to prevent destruction of the hottest cell. (C) 2014 Elsevier Ltd. All rights reserved.
Evaluation of thermal performance of packaged GaN HEMT cascode power switch by transient thermal testing
(2016-04-05)
Chen, Szu-Hao
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Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
In this investigation, thermal transient measurements and analyses are used to study the thermal performance of a cascoded GaN power device. The method is based on the thermal characterization of the on-resistance (R-on) of the device and the synchronized current-voltage characteristics under continuous operation. The changes in R-on with temperature (25 degrees C-180 degrees C) are measured, statistically studied, and correlations investigated. The proposed method for estimating transient thermal impedance has the following characteristics: (1) it is robust and reproducible; (2) it yields a heating curve to prevent overheating for the device under test (DUT); (3) it provides in-situ current-voltage characterization; (4) it includes a transient offset correction for initial transient electrical disturbances (such as current collapse); (5) it optimizes a compact thermal model; (6) it is sensitive to package structure and design variables. This monitoring of thermal impedance variation provides a simple and fast non-destructive method for analyzing power switching devices during thermal testing. Satisfactory experimental results confirm the feasibility of in-situ current-voltage characterization and the real power varies with the thermal impedance. (C) 2015 Elsevier Ltd. All rights reserved.
GaN HEMTs Power Module Package Design and Performance Evaluation
(2013-01-01)
Ho, Chung-Hsiang
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Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
This paper described the electronic performance of power module packaged high-power AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrate. Twelve GaN HEMTs chips are mounted on AlN substrate. Each device is wire-bonded in parallel connection to increase the power rating. Both DC and pulsed current-voltage (ID-VDS) characteristics are measured with different connection and sizes of devices, at various power densities, pulse lengths, and duty factors. The packaged GaN HEMTs exhibit the pulsed drain current, 0.43 A/mm. The performance of packaged multichip GaN HEMTs power module is studied. The GaN HEMTs power module exhibit a drain current of 23.04 A, which indicates that connecting GaN HEMTs devices in parallel can effectively increase the drain current.
GaN HEMTs Power Module Package Design and Performance Evaluation
(2013-01-01)
Ho, Chung-Hsiang
;
Chou, Po-Chien
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
This paper described the electronic performance of power module packaged high-power AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrate. Sixteen GaN chips are mounted on one AlN substrate. There are three AlN substrate in one module. Each device is wire-bonded in parallel connection to increase the power rating. Both DC and pulsed current-voltage (ID-VDS) characteristics are measured for different connection and sizes of devices, at various of power densities, pulse lengths, and duty factors. We found some conditions that makes the parallel connection difference down to zero. According that, The GaN has maxima drain current=5.98A(98.8%).
In Depth Thermal Analysis of Packaged GaN on Si Power Devices
(2013)
Wang, Chieh-An
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Chou, Hsin-Ping
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Cheng, Stone
;
Chou, Po-Chien
;
機械工程學系
AlGaN/GaN high electron mobility transistors (HEMTs) are one of the prospective candidates for high switching frequency power electronics applications thanks to its wide band gap (3.4eV), high breakdown voltage, large critical electric field, high carrier mobility, and the inherent high speed characteristics. With the high power densities that AlGaN/GaN HEMTs are capable of reaching, heat dissipation is a crucial issue. This paper presents the thermal analysis of packaging development, the device is attached on a V-groove copper base, and mounted on TO-3P leadframe to enhance Si substrate thermal dissipation. The effects of structure design and fabrication processes on the device performance as well as thermal resistance were studied. In addition, micro-Raman/Infrared (IR) thermography was used to investigate temperature profiles and hot spot of the devices. Simulations provide key insights into device operation and the thermal mechanisms that affect reliability. After incorporating self-heating effect in calculations of current-voltage characteristics, our results agreed well with experimental data.
Investigation on the Parallel Operation of AII-GaN Power Module and Thermal Performance Evaluation
(2014-01-01)
Cheng, Stone
;
Chou, Po-Chien
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents a 270-V, 56-A GaN power module with three AIN substrates are prepared for the module. Each substrate is composed of three parallel connected GaN chips which incorporates six 2-A AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) cells. The devices are wire-bonded in parallel connection to increase the power rating. The packaged GaN HEMTs exhibit the pulsed drain current of 0.435 A/mm. Both DC and pulsed current-voltage (ID-VDs) characteristics are measured for different connection and sizes of devices, at various power densities, pulse lengths, and duty factors. The static parameters of threshold voltage and leakage currents were extracted to show how these parameters would scale as the devices are paralleled. Performance of multiple chip GaN power module package and thermal evaluation is studied. Experimental results demonstrated the ability to parallel nine GaN HEMTs die together and to verify the current sharing during the dynamic switching to attain high-current capacities.
Miniaturized suspension structure for precise flying height positioning measurement using a swing arm actuator with a holographic optical element module sensor
(2011-03-01)
Chou, Po-Chien
;
Lin, Yu-Cheng
;
Cheng, Stone
;
機械工程學系
;
Department of Mechanical Engineering
This work presents a means of active actuation of the suspension structure with a holographic optical element (HOE) for the small-form-factor optical-disk drives. The proposed HOE module sensor is mounted on a swing arm swivel-drive mechanism with unique features, including a rotary actuator for tracking and a swing arm nutates along a pivot for focusing. The fabrication methodology for a cantilever-beam-like structure with HOE module sensor is investigated. Furthermore, the performances of optical module with swing arm-swivel actuation are experimentally evaluated to demonstrate the effectiveness of precise flying height positioning measurement method. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3549259]
Novel packaging design for high-power GaN-on-Si high electron mobility transistors (HEMTs)
(2013-04-01)
Cheng, Stone
;
Chou, Po-Chien
;
機械工程學系
;
Department of Mechanical Engineering
This study describes the development of packaging for high-power AlGaN/GaN high electron mobility transistors (HEMTs) on a silicon substrate. A transistor is attached to a V-grooved copper base, and mounted on a TO-3P lead-frame. Unlike flipchip or copper-molybdenum-copper (CMC)-based packaging technology, which is popular in the GaN HEMT industry, the proposed packaging structure is implemented on the periphery of the surface of the device to promote thermal dissipation from the Si substrate. The various thermal paths from the GaN gate junction to the case dissipate heat by spreading it to a protective coating; transferring it through bond wires; spreading it laterally throughout the device structure through an adhesive layer, and spreading it vertically through the bottom of the silicon chip. The effects of the design of the structure and its fabrication process on the performance of the device and its thermal resistance were studied. Thermal characterization reveals that the thermal resistance from the GaN chip to the TO-3P package was 13.72 degrees C/W. Self-heating in AlGaN/GaN device structures was measured by infrared (IR) thermography and micro-Raman spectroscopy. Experimental results indicated that a single chip that was packaged in a 5 x 3 mm V-grooved Cu base with a total gate-periphery of 30 mm had a power dissipation of 22 W with a drain bias of 100 V. Both DC and pulsed current voltage (I-D-V-DS) characteristics are measured for a range of transistor structures and sizes, at various of power densities, pulse lengths, and duty factors. These are compared with measured channel temperature profiles. (C) 2012 Elsevier Masson SAS. All rights reserved.