• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.305-308
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode rectifiers is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode rectifiers and guarantee zero-current -switching(ZCS) of the switch over the wide load range The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. IN addition control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations.

• ETRI Journal
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• 제42권5호
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• pp.790-798
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• 2020

Herein, a low-ripple coarse-fine digital low-dropout regulator (D-LDO) without ringing in the transient state is proposed. Conventional D-LDO suffers from a ringing problem when settling the output voltage at a large load transition, which increases the settling time. The proposed D-LDO removes the ringing and reduces the settling time using an auxiliary power stage which adjusts its output current to a load current in the transient state. It also achieves a low output ripple voltage using a comparator with a complete comparison signal. The proposed D-LDO was fabricated using a 65-nm CMOS process with an area of 0.0056 μ㎡. The undershoot and overshoot were 47 mV and 23 mV, respectively, when the load current was changed from 10 mA to 100 mA within an edge time of 20 ns. The settling time decreased from 2.1 ㎲ to 130 ns and the ripple voltage was 3 mV with a quiescent current of 75 ㎂.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2531-2533
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• 2001

This paper describes a low noise and high efficiency analog-digital switching mixed mode battery charger for production facilities of Li-Ion batteries. The requirements for battery chargers for production facilities are very strict. The accuracy of output voltage and output current should be below 0.1% with very low ripple current. Therefore analog type linear regulators are widely used for battery charger in spite of their inefficiency and bulkiness. We combined linear regulator as a voltage source with digital switching converter as a dependent current source. Low current ripple and high accuracy are obtained by linear regulator while high efficiency is achieved by digital switching converter. Experimental results show that proposed method has 0.1% ripple and 90% efficiency at an output current of 1A for a battery voltage of 4V.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.19-21
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• 2006

This paper presents the control method that inverter output keeps to linear to reference voltage of Synchronous Reluctance Motor using DC Link voltage Synthesis. The Inverter output voltage cannot be displayed to linear about inverter reference voltage if Real DC Link voltage is different from DC Link voltage of PWM amplitude. Also, the overmodulation that there is linearity broken if reference voltage is out of range that inverter can output voltage. Torque ripple generates the vibration and noise of a motor. This paper proposes the control method so that torque ripple decreases and the linearity of inverter output keeps using the DC Link voltage Synthesis.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.572-574
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• 2005

In this paper, a compensation scheme for the effect of dc-link ripple voltages on output voltage of two-leg and three-phase PWM inverters is proposed, without which compensation scheme the three-phase output voltage and current are much distorted. The proposed scheme has been verified by experimental results.

• 한국정보통신학회논문지
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• 제12권11호
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• pp.2015-2021
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• 2008

최근 태양광 발전시스템 등 낮은 전압을 발생하는 전원소스를 이용하여 높은 승압효과를 얻기 위한 멀티레벨 인버터에 대한 관심이 높아지고 있다. 본 연구에서는 DC/DC의 출력전압 리플 저감을 위한 새로운 구조의 다중레벨 DC/DC 컨버터를 제안한다. 제안된 컨버터는 Buck컨버터를 직렬로 연결하여 다중전압을 발생하는 구조를 취함으로 기존의 Buck 컨버터에 비하여 출력 전압의 리플을 저감할 수 있었다. 또한 FPGA 기반 멀티레벨 인버터용 스위칭 함수를 구현하고자 하였다.

• 전력전자학회논문지
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• 제18권1호
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• pp.91-102
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• 2013

This paper proposes the improved LCCT(Inductor-Capacitor-Capacitor-Trans) Z-source DC-DC converter (Improved LCCT ZSDC) which can generate the bipolar output voltages according to duty ratio D. The proposed converter has the characteristic and structure of Quasi Z-source DC-DC converter(Quasi ZSDC) and conventional LCCT Z-source DC-DC converter(LCCT ZSDC). To confirm the validity of the proposed method, PSIM simulation and a DSP based experiment were performed for each converter. In case which the input DC voltage is 70V, the bipolar output DC voltage of positive 90V and negative 50V could generate. Also, as comparison result of the capacitor voltage ripple in Z-network and the input current under the same condition for each converter, the voltage stress and the capacitor voltage in Z-network of the proposed method were lower compared with the conventional methods. Finally, the efficiency for each method was investigated according to load variation and duty ratio D.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권12호
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• pp.813-820
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode converter is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode converter and guarantee zero-current-switching(ZCS) of the switch over the wide load range. The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. In addition, control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations and experiments.

• Journal of Power Electronics
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• 제15권6호
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• pp.1468-1479
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• 2015

Renewable energy resources such as wind and photovoltaic power generation systems demand a high step-up DC-DC converters to convert the low voltage to commercial grid voltage. However, the high step-up converter using a transformer has limitations of high voltage stresses of switches and diodes when the transformer winding ratio increases. Accordingly, conventional studies have been applied to series-connect multioutput converters such as forward-flyback and switched-capacitor flyback to reduce the transformer winding ratio. This paper proposes new single-ended converter topologies of an isolation type and a non-isolation type to improve power efficiency, cost-effectiveness, and output ripple. The first proposal is an isolation-type charge-pump switched-capacitor flyback converter that includes an extreme-ratio isolation switched-capacitor cell with a chargepump circuit. It reduces the transformer winding number and the output ripple, and further improves power efficiency without any cost increase. The next proposal is a non-isolation charge-pump switched-capacitor-flyback tapped-inductor boost converter, which adds a charge-pump-connected flyback circuit to the conventional switched-capacitor boost converter to improve the power efficiency and to reduce the efficiency degradation from the input variation. In this paper, the operation principle of the proposed scheme is presented with the experimental results of the 100 W DC-DC converter for verification.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.234-238
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• 1999

In order to radiate X-ray, the low ripple stabilized high voltage DC over the range of 40KV to 150KV is directly inflicted to X-ray tube. The energy characteristics of the radiated X-ray depend on the pulsating waveforms of the DC voltage supplied X-ray tube. In general, the low ripple voltage waveforms with fast rising times are required to increase with the dosage per unit time lest the exposure time should be longer in orde that the motion artifacts of an object may be eliminated in actual. The conventional types of X-ray generators were bulky in physical size and heavy in weight, and the control accuracies of the output voltages were not always satisfactory. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing new power semiconductor devices. To decreasing the volume and the weight of high voltage transformer, and to stabilize ripple, a high frequency PWM inverter is connected between DC source and high voltage transformer. This paper describes the output characteristics according to stabilize ripple of X-ray tube voltage and compared the reproducibility, direcibility and doesage.