• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.39-43
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• 2009

In order to develop piezoelectric inverter module for CCFL driving, Rosen-type multilayer piezoelectric transformer was fabricated. The output power and efficiency of mutilayer piezoelectric transformer according to the variation inner electrode layer were investigated. Mutilayer piezoelectric transformer was fabricated conventional mutilayer ceramic method using PZT base ceramics. Also, piezoelectric inverter module was adopted driving circuit with half-bridge type. The piezoelectric inverter module was set up with input voltage 12.5 V, switching frequency 104.3 KHz. The results showed the value of step-up ratio 100, efficiency 87% at load resistance of $100k{\Omega}$.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.242-249
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• 2011

The proposed converter has easy device selection for high step-up and high power applications since boost half bridge and voltage doubler cells are connected, respectively, in parallel and series in order to increase output power and voltage. Especially, optimized design of high frequency transformers is possible owing to reduced turn ratio and eliminated dc offset, and distributed power through three cores is beneficial to low profile and thermal distribution. The proposed converter does not necessitate start-up circuit and additional clamp circuit due to the use of whole duty range between 0 and 1 and is suitable for applications with wide input voltage range. Also, high efficiency can be achieved since ZVS turn on of switches are achieved in wide duty cycle range and ZCS turn on and off of diodes are achieved. The proposed converter was validated through 5 kW prototype.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.16-21
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• 2008

In this study the effects of swelling and fixing agent for the cotton side of polyester/cotton blended fabrics and the thermosol temperature on the dyeing properties and fastness. were investigated, when the polyester/cotton blended fabrics were dyed with a disperse dye which was able to dye both side of fiber by one bath one step thermosol process. The obtained results are as follows; The dye adsorption decreased with the increase of cotton blend ratio in polyester/cotton blended fabrics, when the ratio of swelling and fixing agent for cotton side was constant. As the thermosol temperature increased up to $210^{\circ}C$, the dye adsorption were increased, but that effect was less significant when the cotton blend ratio was higher.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1629-1638
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• 2016

Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, high-efficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.11-13
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• 2019

This paper proposes a novel high step-up non-isolated DC-DC converter, suitable for regulating dc bus in various inherent low voltage micro sources especially for photovoltaic (PV) and fuel cell sources. This novel high voltage Non-isolated Boost DC-DC converter topology is best replacement, where high voltage conversion ratio is required without the transformer and also need continuous input current. Since the proposed topology utilizes the stack-based structure, the voltage gain, and the efficiency are higher than other conventional non-isolated converters. Switches in this topology is easier to control since its control signal is grounding reference. Also, there is no need of extra gate driver and extra power supply for driver circuit, which reduces the cost and size of system. In order to show the feasibility and practicality of the proposed topology principle operation, steady state analysis and simulation result is presented and analyzed in detail. To verify the performance of proposed converter and theoretical analysis 360W laboratory prototype is implemented.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1536-1544
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• 2018

The existing 24-pulse autotransformer rectifier unit (ATRU) needs interphase reactors for parallel work of the rectifier bridges, and its output voltage cannot be regulated. Aiming at these problems, a step-up and step-down asymmetrical 24-pulse ATRU is proposed in this paper. The connections and turns ratios among transformer windings are well designed. In addition, a 15-degree phase difference is formed between two of the 24 voltage vectors produced by the transformer, which makes the four rectifier bridge groups produce a 24-pulse DC voltage without interphase reactors. Meanwhile, by adding extended winding to each phase of the transformer, wide-range regulation of the ATRU output voltage can be realized, and the reasonable voltage regulation range is between 0.2 and 1.6. The superposition of the voltage vectors and the principle of the voltage regulation are analyzed in detail. Furthermore, the turns ratio of the windings, winding current, output voltage, and kilovolt-ampere rating are all derived. Finally, the simulations and experiments are carried out, and the correctness of the principle and theoretical analysis of the new 24-pulse ATRU are verified.

• Journal of Power Electronics
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• v.18 no.2
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• pp.343-355
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• 2018

A wide-voltage-conversion range bidirectional DC-DC converter is proposed in this paper. The topology is comprised of one typical LC energy storage component and a special common grounded asymmetric H-bridge with four active power switches/anti-parallel diodes. The narrow output PWM voltage is generated from the voltage difference between two normal (wider) output PWM voltages from the asymmetric H-bridge with duty cycles close to 0.5. The equivalent switching frequency of the output PWM voltage is double the actual switching frequency, and a wide step-down/step-up ratio range is achieved. A 300W prototype has been constructed to validate the feasibility and effectiveness of the proposed bidirectional converter between the variable low voltage side (24V~48V) and the constant high voltage side (200V). The slave active power switches allow ZVS turn-on and turn-off without requiring any extra hardware. The maximum conversion efficiency is 94.7% in the step-down mode and 93.5% in the step-up mode. Therefore, the proposed bidirectional topology with a common ground is suitable for energy storage systems such as renewable power generation systems and electric vehicles with a hybrid energy source.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.5
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• pp.193-200
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• 2004

In this study, we propose a small high voltage power supply, which uses a half-bridge ZCS resonant and Cockroft-Walton circuit as its ESP (Electrostatic Precipitator). This power supply transfers energy from the ZCS resonant inverter to the step-up transformer. The transformer secondary is then applied to the Cockroft-Walton circuit for generating high voltage as a discharging source of electrodes. It is highly efficient because its amount of switching losses are reduced by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step up transformer secondary combined with the Cockroft-Walton circuit. Using this power supply, experiments have been carried out as a function of the switching frequency and duty ratio in order to investigate the smoke removal characteristics. From these results, the best operational condition is obtained at the switching frequency of 9 kHz and the duty ratio of 50% in this ESP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.195-198
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• 2004

In this paper, the disk-type piezoelectric transformer for the high power was investigated with the variation of road resistance. The diameter and thickness of a disk-type piezoelectric transformer was 50mm and 4.5mm, respectively. The piezoelectric transformer was composed to PZT-PMN-PSN. The ratio of driving electrode and generating electrode ranges from 1.4:1 to 3:1. The poling direction of driving part and generating part are the same. A voltage step-up ratio increased with increasing the load resistance, $R_L$, so it reached 60 times under no road resistance. also, the maximum efficiency of 97% was obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.852-856
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• 2000

In this paper, we investigated the output power, step-up ratio and efficiency properties of piezoelectric transformer with dielectric and piezoelectric characteristics of manufactured ceramics. The piezoelectric transformers with $2.0$\times$10$\times$48[$mm^3$] size were fabricated and its electrical properties were measured. When output power of 6W was constantly maintained, T2 piezoelectric transformer showed the minimum temperature rise of $9(^{\circ}C)$ at $150(K\Omega)$ load resistance. However, T1 piezoelecric transformer showed the temperature rise of $7.2(^{\circ}C)$ at $200(K\Omega)$ load resistance. The 6[w] CCFL (Cold Cathode Fluorescent Lamp) was successfully driven by T1 and T2 piezoelectric transformer but, its temperature rise $\Delta$T[$^{\circ}C)$] was generated more than $20(^{\circ}C)$. It is concluded that we have to design the piezoelectric transformers so that its output impedance correspond to the load impeadance, including any stray capacitance.