• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.564-571
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• 2001

This paper presents the VLSI design of highly efficient low voltage DC/DC converter for portable devices. All active devices are integrated on a single chip using a standard 0.65$\mu\textrm{m}$ CMOS process. The converter operates at the switching frequency of 1MHz for reducing the size of passive elements and uses a ZVS for minimizing the switching loss at high frequency. Simulation results show that the circuit can achieve a 95% efficiency when the output voltage is controlled to be 2V with the load of lW.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.275-278
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• 2008

In this paper, I propose the full CMOS FLL(frequency locked loop) circuit. The proposed FLL circuit has a simple structure which contains a FVC(frequency-to-voltage converter), an operational amplifier and a VCO(voltage controlled oscillator). The operation of FLL circuit is based on frequency comparison by the two FVC circuit blocks. The locking time of FLL is short compared to PLL(phase locked loop) circuit because the output signal of FLL is synchronized only in frequency. The circuit is designed by 0.35${\mu}m$ process and simulation carried out with HSPICE. Simulation results are shown to illustrate the performance of the proposed FLL circuit.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.3
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• pp.266-274
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• 1991

This paper proposed the resonant DC-DC converter with constant switching frequency. Its output is controlled by the auxiliary switch which is attached in conventional MRC circuits. The average output voltage is equal to the average voltage of the auxiliary switch. If the on time of the auxiliary switch is short, output voltage is decreased. Because of using the multi resonant method, the power loss from the parasitic elements can be decreased. Experimental performance of DF ZVS Forward MRC topology with switching frequency of 1MHz is presented.

• Journal of Power Electronics
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• v.18 no.4
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.2
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• pp.63-68
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• 2017

This paper proposes a new non-isolated DC conversion circuit topology of the voltage source coupled inductor series resonant high-frequency PFM controlled boost chopper type DC-DC power converter using two in one IGBT power module, which can efficiently operate under a principle of zero current soft switching for wide output regulation voltage setting ranges and wide fluctuation of the input DC side voltage as well as the load variation ranges. Its steady state operating principle and the output voltage regulation characteristics in the open-loop-based output voltage control scheme without PI controller loop are described and evaluated from theoretical and experimented viewpoints. Finally, in this paper the computer-aided simulation steady-state analysis and the experimental results are presented in order to prove the effectiveness and the validity of voltage regulation characteristics of the proposed series resonant zero current soft switching boost chopper type DC-DC power converter circuit using IGBTs which is based on simple pulse frequency modulation strategy more than, 20kHz.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.616-621
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• 2005

We considered of the buck and half bridge series DC-DC converter. It has good applications in areas with low voltage/high current, wide input voltage. The buck converter ratings and the half bridge converter ratings are $36\~72V$ input and 22V/5A output, $19\~24V$ input and 3.3V/30A output, respectively. Developed the buck and half Bridge series DC-DC converter ratings are of $36\~72V$ input and 3.3V/30A output. The buck converter is operated with zero voltage switching process to reduce the switching losses. The $80.1\%\~97.6\%$ of the efficiency is measured at $18.4{\mu}H$ output filter inductance of buck converter. In the half bridge converter, the $86\%\~96.4\%$ efficiency is measured at 150kHz switching frequency with PQI core. In the case of synchronized the buck and half bridge DC-DC converter, the measured efficiency is higher than that of the unsynchronized converter. In the synchronized converter, the maximum efficiency is measured up to $92.3\%$ with PQI core at 150kHz. 7A output.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.80-86
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• 2022

In this paper, the optimal design and circuit simulation verification results of an LLC resonant half-bridge dc-dc converter using a steady-state model with internal loss resistance are reported. Above all, the input/output voltage gain and frequency characteristic equations in the steady-state were derived by reflecting the internal loss resistance in the equivalent circuit. Based on the results, an LLC resonant half-bridge dc-dc converter with an input voltage of 360-420V, an output voltage of 54V, and a maximum power of 3kW was designed, and to verify the design, the PSIM circuit simulation was executed to compare and analyze the result. In particular, the operating range of the converter could be drawn from the frequency characteristic graph of the voltage gain, and when the converter was operated under light and maximum load conditions, it was confirmed that similar results were obtained by comparing simulation results and calculation results in the switching frequency characteristic graph. In addition, the change of the switching frequency with respect to the load current at each input voltage was compared with the calculated value and the simulation result. As a result, it was possible to confirm the usefulness of the analysis result reflecting the internal loss resistance proposed in this paper and the process of the optimal design.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.498-506
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• 2022

This study proposes a design methodology for bidirectional, series-resonant, dual-active bridge (SRDAB) converters. The circuit parameters of the SRDAB converters are designed by considering the output power and efficiency of the converter. The proposed method can be used to design a high-power, high-efficiency SRDAB converter. A voltage controller is employed to manipulate the output voltage of the converter, and the controller gains are selected using the transfer function and frequency response of the controller. Simulation results show that the output power of the designed SRDAB converter is 2 kW per converter module as designed. In addition, the performance of the voltage controller is evaluated using the simulation and experimental results. The output voltage follows the reference voltage within 10 ms under the step change of the reference command. The output voltage also follows the reference voltage under the step load change. The efficiency of the designed SRDAB converter is 95.6%.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.8
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• pp.423-429
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• 2006

Recently, the high frequency isolated boost DC/DC converter has been widely used for the PCS (Power Conditioning System) system because of its small size and low cost. However, the high frequency isolated boost DC/DC converters applied the conventional voltage-fed converter and current-fed converter have the problems such as the high conduction losses and the surge voltage due to the high circulating current and the leakage inductance, respectively. To overcome this problems, in this paper the secondary LLC resonant converter is proposed, and the experimental results of the secondary LLC series resonant converter for boost DC/DC converter are verified on the simulation based on the theoretical analysis and the 700W experimental prototype.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.