• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.97-104
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• 2017

In the present industrial field, the demand for the development of the solar power source device and the charging device for the solar cell is gradually increasing. The solar charger is largely divided into a DC-DC converter that converts the voltage generated from the sunlight to a charging voltage, and a battery and a charger that are charged with an actual battery. The conventional charger topology is used either as a Buck converter or a Boost converter alone, which has the disadvantage that the battery can not always be charged to the desired maximum power as input and output conditions change. Although studies using a topology capable of boosting and stepping have been carried out, Buck-Boost converters or Sepic converters with relatively low efficiency have been used. In this paper, we propose a new Buck Boost combination power converter topology structure that can use Buck converter and Boost converter at the same time to improve inductor current ripple and power converter efficiency caused by wide voltage control range like solar charger.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.7
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• pp.1349-1355
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• 2009

This paper is studied on a novel power factor correction (PFC) AC-DC converter of high efficiency by soft switching technique. The input current waveform in the proposed converter is got to be a sinusoidal form composed of many a discontinuous pulse in proportion to the magnitude of a ac input voltage under the constant switching frequency. Therefore, the input power factor is nearly unity and the control method is simple. The proposed converter adding an electric isolation operates with a discontinuous current mode (DCM) of the reactor in order to obtain some merits of simpler control, such as fixed switching frequency, without synchronization control circuit used in continuous current mode (CCM). To achieve the soft switching (ZCS or ZVS) of control devices, the converter is constructed with a new loss-less snubber for a partial resonant circuit. It is that the switching losses are very low and the efficiency of the converter is high, Particularly, the stored energy in a loss-less snubber capacitor recovers into input side and increases input current from a resonant operation. The result is that the input power factor of the proposed converter is higher than that of a conventional PFC converter. This paper deals mainly with the circuit operations, theoretical, simulated and experimental results of the proposed PFC AC-DC converter in comparison with a conventional PFC AC-DC converter.

• Journal of IKEEE
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• v.17 no.3
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• pp.284-293
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• 2013

This paper describes a DC-DC boost converter for thermoelectric energy harvesting. The designed converter boosts the VDD through a start-up block from a low-output voltage of a thermoelectric device and the boosted VDD is used to operate the internal control block. When the VDD reaches a predefined value, a detector circuit makes the start-up block turn off to minimize current consumption. The final boosted VOUT is achieved by alternately operating the DC-DC converter for VDD and the main DC-DC converter for VOUT according to the comparator outputs. Simulation results shows that the designed converter generates 2.65V from an input voltage of 200mV and its maximum power efficiency is 63%. The area of the chip designed using a 0.35um CMOS process is $1.3mm{\times}0.7mm$ including pads.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.6
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• pp.25-32
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• 2011

This paper proposes high efficiency current-mode DC-DC buck converter that are suitable for portable devices. The current-mode DC-DC buck converter using adjustable Dead-time control method improves the power efficiency 2~5%. The buck converter has been implemented with a standard 0.35${\mu}m$ CMOS process. The size of this chip is 0.97$mm^2$. The input range of the fabricated DC-DC buck converter is 2.5V~3.3V, and the output is 1.8V. The maximum loading current of the converter is 500mA and the peak efficiency is 93% at 200mA loads.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.89-93
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• 2017

This paper introduces an energy harvesting system that generates energy by collecting multi-band RF signals using buck-boost DC-DC converter. In an environment where the resistance of load using the collected electric energy is constantly changing, a buck-boost DC-DC converter is used in which the input resistance of the DC-DC converter does not change even if the load resistance changes. Since the frequency band of the input RF signal varies, the rectifier is designed for each band so that multiple bands can be processed, and a matching circuit is added to each band in front of the rectifier. For a rectifier to collect very small RF signals, a circuit is designed so that a constant voltage is obtained according to a very small input signal by devising a method of continuously accumulating the voltages collected and generated in each band. It is confirmed that the output efficiency can reach up to 20% even for the RF signal having the input of -20 dBm.

• Journal of IKEEE
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• v.14 no.2
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• pp.90-97
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• 2010

The high efficiency power management IC(PMIC) with DTMOS(Dynamic Threshold voltage MOSFET) switching device and DTMOS Error Amplifier is presented in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. Dynamic Threshold voltage CMOS(DT-CMOS) with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuits consist of a saw-tooth generator, a band-gap reference circuit, an DT-CMOS error amplifier and a comparator circuit as a block. the proposed DT-CMOS Error Amplifier has 72dB DC gain and 83.5deg phase margin. also Error Amplifier that use DTMOS more than CMOS showed power consumption decrease of about 30%. DC-DC converter, based on Voltage-mode PWM control circuits and low on-resistance switching device is achieved the high efficiency near 96% at 100mA output current. And DC-DC converter is designed with Low Drop Out regulator(LDO regulator) in stand-by mode which fewer than 1mA for high efficiency.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.40-41
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• 2016

The inverter resistance welder requires AC/DC converter of high efficiency because the converter changes a commercial ac power source to low voltage dc power source. Harmonic components that occur in the conversion process of converter decrease system power factor and deal great damage in electric power system. To improve such problems, this paper proposes a high efficiency AC/DC converter for inverter resistance welder. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit. As a result, the proposed AC/DC converter obtains low switching power loss and high efficiency.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1293-1302
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• 2018

Multiport power converters have recently become popular to researchers and engineers. However, more improvements are required in terms of their soft-switching operation, bidirectional operation, and integration. In this study, a bidirectional three-port three-switch DC-DC converter is proposed. The converter contains a low-current ripple port and ripple-free current port. Through the integrated structure, utilization of a coupled inductor, and a new switching strategy, the aforementioned specifications are achieved. A modified switching strategy is also utilized in the converter, which has resulted in the bidirectional operation of the converter between ports. Finally, a comprehensive analysis is presented, and the converter characteristics are validated by experimental results.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.432-433
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• 2018

A new DC-DC converter circuit for LVDC(Low Voltage Direct-Current) distribution is proposed. DC-DC converter consists of two stage which are voltage balancer and converter stage. The balancing circuit adjust balance input voltage of converter circuit and compensate for unbalanced loads and short circuits. The converter circuit control the bipolar output voltage ${\pm}750V$. Simulation is carried out for this DC-DC converter system.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.169-176
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• 2005

In this paper, a DC and small-signal AC modeling for the active-clamp, ful1-bridge boost converter is described. Based on the operation principle, the ac part of the converter can be replaced by a dc counterpart. Then, a conceptual equivalent circuit is derived by rearranging the switches. The equivalent circuit for this converter consists of CCM(Continuous conduction mode) boost and DCM(Discontinuous conduction mode) buck converter. The analyses for the equivalent CCM boost and DCM buck converter are done using the model of PWM switch. The theoretical modeling results are confirmed through experiment or SIMPLIS simulation.