• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1232-1234
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• 2003

The push pull forward converter is a very suitable circuit for low output voltage, high output current applications with a wide input voltage range. This converter can be miniaturized by integrate magnetic components such as the output inductor, the transformer and the input inductor. We considered of the efficiency for the push pull forward converter. Developed the push pull forward converter rating are of $36{\sim}72V$ input and 3.3V/30A output. In this converter. the efficiency was measured by 76.4% at full load and 82.95% at half load. The maximum efficiency is up to 83.% at 200kHz, 11A output.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.6
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• pp.592-597
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• 2005

The push pull forward converter is suitable in a low output voltage, a high output current applications with wide input voltage ranges. All magnetic components including output inductor, transformer and input filter can be integrated into single EI/EE core. The integrated push pull forward converter is considered through the comparison of efficiency according to the circuit parameters. The Nicera company's 5M FEE18/8/10C and NC-2H FEI32/8/20 cores are used for the transformer. The integrated push pull forward converter ratings are of $36\~72V$ input and 3.3V/30A output. In case that NC-2H FEI32/8/20 core used in the converter, the efficiency is measured up to $83.5\%$ at the switching frequency 200 kHz and the 11A load. The efficiencies of $76.4\%$ at a full load and $82.95\%$ at a half load are measured.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.36-39
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• 2003

The push pull forward converter is a very suitable circuit for low output voltage, high output current applications with a wide input voltage range. All the magnetic components (output inductor, transformer, input filter) can be integrated into a single core. The integrated magnetics can reduce the number of the magnetic components. Developed the push pull forward converter rating are of 36 $\~$72V input and 3.3V/30A output. In this converter, the efficiency was measured by $76.4\%$ at full load and 82.95$\%$ at full load. The maximum efficiency is up to 83.$\%$ at 200kHz switching frequency, l1A output.

• Journal of Power Electronics
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• v.14 no.3
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• pp.444-457
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• 2014

This paper presents the design and realization of a digital PV simulator with a Push-Pull Forward (PPF) circuit based on the principle of modular hardware and configurable software. A PPF circuit is chosen as the main circuit to restrain the magnetic biasing of the core for a DC-DC converter and to reduce the spike of the turn-off voltage across every switch. Control and I/O interface based on a personal computer (PC) and multifunction data acquisition card, can conveniently achieve the data acquisition and configuration of the control algorithm and interface due to the abundant software resources of computers. In addition, the control program developed in Matlab/Simulink can conveniently construct and adjust both the models and parameters. It can also run in real-time under the external mode of Simulink by loading the modules of the Real-Time Windows Target. The mathematic models of the Push-Pull Forward circuit and the digital PV simulator are established in this paper by the state-space averaging method. The pole-zero cancellation technique is employed and then its controller parameters are systematically designed based on the performance analysis of the root loci of the closed current loop with $k_i$ and $R_L$ as variables. A fuzzy PI controller based on the Takagi-Sugeno fuzzy model is applied to regulate the controller parameters self-adaptively according to the change of $R_L$ and the operating point of the PV simulator to match the controller parameters with $R_L$. The stationary and dynamic performances of the PV simulator are tested by experiments, and the experimental results show that the PV simulator has the merits of a wide effective working range, high steady-state accuracy and good dynamic performances.

• Journal of Power Electronics
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• v.17 no.1
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• pp.20-30
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• 2017

A novel zero-voltage-switching (ZVS) push-pull forward converter with a parallel resonant network is presented in this paper. The novel topology can provide a releasing loop for the energy storage in a leakage inductor for the duration of the power switching by the resonant capacitors paralleled with the primary windings of the transformer. Then the transformer leakage inductor is utilized to be resonant with the parallel capacitor, and the ZVS operation is achieved. This converter exhibits many advantages such as lower duty-cycle losses, limited peak voltage across the rectifier diodes and a higher efficiency. Furthermore, the operating principles and key problems of the converter design are analyzed in detail, and the ZVS conditions are derived. A 500W experimental converter prototype has been built to verify the effectiveness of the proposed converter, and its maximum efficiency reaches 94.8%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.99-104
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• 2006

A semi-Lagrangian finite element scheme with objective time stepping algorithm for solving viscoelastic flow problem is presented. The convection terms in the momentum and constitutive equations are treated using a quasi-monotone semi-Lagrangian scheme, in which characteristic feet on a regular grid are traced backwards over a single time-step. Concerned with the generalized midpoint rule type of algorithms formulated to exactly preserve objectivity, we use the geometric transformation such as pull-back, push-forward operation. The method is applied to the 4:1 planar contraction problem for an Oldroyd B fluid for both creeping and inertial flow conditions.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.5
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• pp.536-541
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• 1988

The push-pull current-fed DC-to-DC converter has only one energy storage reactor in series with the input for any number of outputs. It is considered that this property of the converter has considerable advantages over other multiple-output circuits. The steady state characteristics of the converter with two outputs is analyzed. It is known that the voltage difference between the two outputs appears by existing the 2nd winding resistance of transformer and there is a region of the duty ratio in which the voltage difference of the converter is smaller than that of the forward converter.

• ETRI Journal
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• v.25 no.1
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• pp.25-33
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• 2003

This paper describes interactive dynamic simulation schemes for articulated bodies in virtual environments, where user interaction is allowed through a haptic interface. We incorporated these schemes into our dynamic simulator I-GMS, which was developed in an object-oriented framework for simulating motions of free bodies and complex linkages, such as those needed for robotic systems or human body simulation. User interaction is achieved by performing push and pull operations with the PHANToM haptic device, which runs as an integrated part of I-GMS. We use both forward and inverse dynamics of articulated bodies for the haptic interaction by the push and pull operations, respectively. We demonstrate the user-interaction capability of I-GMS through on-line editing of trajectories for 6-dof (degrees of freedom) articulated bodies.

• Journal of Power Electronics
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• v.18 no.2
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• pp.407-417
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• 2018

A novel family of Buck mode three-level direct ac converters with a high frequency link is proposed. These converters can transfer an unsteady high ac voltage with distortion into a regulated sinusoidal voltage with a low THD at the same frequency. The circuit configuration is constituted of a three-level converter, high frequency transformer, cycloconverter, as well as input and output filters. The topological family includes forward, push-pull, half-bridge, and full-bridge modes. In order to achieve a reliable three-level ac-ac conversion, and to overcome the surge voltage and surge current of the cycloconverter, a phase-shifted control strategy is introduced in this paper. A prototype is presented with experimental results to demonstrate that the proposed converters have five advantages including high frequency electrical isolation, lower voltage stress of the power switches, bi-directional power flow, low THD of the output voltage, and a higher input power factor.

• Journal of Technology Innovation
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• v.7 no.1
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• pp.14-35
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• 1999

This paper presents the relationship between the pace of structural change and the magnitude of employment growth in the manufacturing sector in OECD countries. To measure the pace of structural change, the compositional change index in value-added in manufacturing sector is introduced. For mid to long-term there seems to be a positive relationship between the pace of structural change and the magnitude of employment growth. In those countries with higher value of the compositional index, the employment growth in manufacturing sector was generally higher. To analyse the characteristics of structural change in manufacturing sector, this paper classifies manufacturing industries into groups: one based on technology, one on orientation, one on wages and one on skills. The international comparison of manufacturing sector's employment patterns based on above four classifications are presented. International comparison suggests that Korean manufacturing sector move into jobs with more skills and knowledge The structural change of SMEs and large firms are compared based on above four classification methods. It is shown that SMEs' employment in low value sectors, that is low-technology, labor-intensive, tow-wage, and unskilled sectors, have risen faster than SMEs' employment in high-technology, science-based, high-wage and skilled sectors. Large firms' employment have been mainly increased in high value sectors. However, the employment growth of both large and small firms have been concentrated on production worker-intensively-using sectors, i.e. unskilled sectors. This widened the wage differential of production workers by firm sizes and concurrently led to severe shortage of production workers for SMEs, which has little ability to pay high wage to production workers because they usually belong to low-wage sectors. Korea need to push SMEs forward to high value sectors. The premise of that is, however, to pull large firms out of production worker-intensively-using sectors.