Po-Chien Chou

A Novel Seesaw Swivel Actuator Design and Fabrication

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.

Optimization of Seesaw Swing Arm Actuator Design for Small Form Factor Optical Disk Drive

Many small form factor (SFF) optical pickup heads based on the swing arm design utilize a piezoelectric material or the slim metal plate to perform the focusing action. The seesaw-type actuator is a new mechanism used in the focusing action for SFF optical data storage devices. The swing arm nutates along a pivot instead of a hinge in the vertical movement. In this paper, an optimized design of a biaxial voice coil motor (VCM), in which the tracking and focusing VCMs are combined in the rear of the swing arm, is proposed. Simulation and experiment results demonstrate the effectiveness of the proposed design methodology by showing that the stress magnitude distribution characteristics, mechanism stiffness, and driving stability of the optimized design are enhanced in comparison with those of the original. # 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.052502 Optical disk drives are one of the most popular systems for information storage. Obtaining the required high track density and accurate focusing requires a high-precision servo system. The micro-optical disk drive (ODD) can be a solution for compact size and portability. The development of a micro-optical head with a swing arm actuator is significant for new optical storage technology. Rather than a mechanism design of a swing arm, most research work has focused on the micro-optical system design required to provide the optical characteristics. A swing-arm-type rotary actuator has advantages over a linear actuator in terms of fast access time, slim shape, mobility, and high mechanical performance. Several papers on slider design or improvements of ODD systems have been introduced. 1,2) However, the important mechanical issues regarding the design of the suspension, swing arm, and the air gap between the magnets and yoke have not been discussed in the literature. In this paper, a new design that uses a biaxial voice coil motor (VCM) and multi segmented magnet arrays (MSMA) with numerical simulations are presented to evaluate the electromagnetic performance. We designed a seesaw mechanism of a rotary type miniaturized actuator with a focusing mechanism with sufficient mechanical bandwidth for a micro-ODD. 3,4) In DataPlay’s patents and other typical focusing mechanism designs, a hinged plate with a coil mounted for focusing is controlled by a VCM driver. However, the thin metal hinge is weak and tends to fracture with repeated operations. 5) To resolve this problem, the proposed design replaces the hinge spring with a seesaw movement. The initial seesaw actuator was designed on the basis of electromagnetic (EM) and structural analyses for both focusing and tracking actuators. Each mechanical part is designed to satisfy the requirements of the servo control performance and dynamic characteristics. 6,7) To maximize the seesaw actuator driving force, a magnetic circuit with a fan-shaped magnet was suggested for the voice coil motion. A combination of three fan-shaped magnets and a ring tracking yoke was used in the actuator magnetic circuit. The new mechanism was also optimized to obtain high seesaw arm stiffness and improved swinging performance within the mechanical tolerances using the proposed design procedure based on finite element (FE) and EM analyses. To estimate the swing stability of the

Adaptive ZPETC method for dual-stage actuator controller design in miniaturized optical disc drive

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.

Enhancement of Optical Adaptive Sensing by Using a Dual-Stage Seesaw-Swivel Actuator with a Tunable Vibration Absorber

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.

In depth thermal analysis of packaged GaN on Si power devices

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.

GaN HEMTs power module package design and performance evaluation

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%).

Miniaturized suspension structure for precise flying height positioning measurement using a swing arm actuator with a holographic optical element module sensor

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.

Power conditioning applications of 700V GaN-HEMTs cascode switch

A hybrid cascoded GaN switch configuration is demonstrated in power conversion applications. A novel metal package is proposed for the packaging of a D-mode GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) cascoded with an integrated power MOSFET and a Schottky barrier diode. The normally-off cascode circuit provides a maximum drain current of 14.6 A and a blocking capability of 700 V. Analysis of 200 V/ 1 A power conversion characteristics are discussed and show the excellent switching performance in load circuits. Switching characteristics of the integral SiC Schottky barrier diode are also demonstrated. Finally, a flyback AC-DC converter is used to evaluate the benefit of GaN cascode switches. These results show that high-voltage GaN-HEMTs can be switching devices for an ultralow-loss converter circuit.

Investigation on the parallel operation of All-GaN power module and thermal performance evaluation

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 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.

All GaN-on-Si high power module design and performance evaluation

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.