• 대한전자공학회논문지SD
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• 제49권8호
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• pp.35-40
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• 2012

DC-DC 컨버터에서 넓은 범위의 부하에 대하여 높은 효율을 유지하기 위해서는 PWM과 PFM을 함께 사용하는 듀얼 모드 제어 방식이 흔히 사용된다. 듀얼 모드 벅 컨버터는 부하 조건에 따라서 PWM이나 PFM을 선택해서 동작하므로, 모드 제어를 위한 부가 회로로 인하여 칩 면적이 증가하고 제어 방식이 변경되는 구간에서는 최적화된 효율을 얻을 수 없다. 본 논문에서는 전류 모드의 PWM 제어 회로에서 사용하는 발진기 대신에 PLL 기반의 발진기를 사용함으로써 추가적인 제어 회로 없이 PWM과 PFM의 통합된 제어 방식으로 동작하는 벅 컨버터를 제안함으로써 듀얼 모드 벅 컨버터의 단점을 해결했다. 제안한 통합 제어 방식의 벅 컨버터는 PSIM 시뮬레이션을 통하여 검증하였으며, 설계된 벅 컨버터 회로를 Cadence Spectre로 시뮬레이션 결과 250mA의 부하에서 최대 효율은 94.7%이고 10mA의 경부하에서 효율은 85.4%이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1599-1610
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• 2019

Intelligent services have expanded as Internet of Things (IoT) technology has evolved and new requirements emerge to accommodate various services. One new requirement is transmitting data over long distances with low-power. Researchers have developed low power wide area (LPWA) network technology to satisfy the requirement; this can improve IoT network infrastructure and increase the range of services. However, network coverage expansion causes several problems. The traffic load is concentrated at a specific gateway, which causes network congestion and leads to decreased transmission efficiency. Therefore, the approach proposed in this paper attempts to recognize and then avoid congestion through gateway channel hopping. The LPWA network employs multiple channels, so wireless channel hopping is available in a gateway. Devices that are not delay sensitive wait for the gateway to reappear on their wireless channel; delay sensitive devices change the wireless channel along the hopping gateway. Thus, the traffic load and congestion in each wireless channel can be reduced improving transmission efficiency. The proposed approach's performance is evaluated by computer simulation and verified in terms of transmission efficiency.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.279-282
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• 2005

Recently, due to the launching of digital broadcasting service, a demand of PDP TV with large screen size is sharply rising. PDP power module is mainly divided into power factor correction (PFC) stage and sustaining power stage. Especially, sustaining power module has pulsating load characteristics. So, the hard switching at light load condition causes low efficiency and thermal problem. Therefore, a new power conversion circuit for sustaining power module of 60' PDP is proposed whose ZVS is obtained by additional ZVS tank. This paper presents properties of the proposed converter through mode analysis, numerical analysis. And a 900w prototype for sustaining power module of 60' PDP is produced to verify the analytic results. As an experimental results, ZVS is achieved from full load to 10% load variation and more than 92% of high efficiency is obtained at 10% load condition.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.100-108
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• 2016

This paper presents a simple high efficiency full-bridge DC-DC converter using a series resonant capacitor. The proposed converter achieves the zero voltage switching of the primary switches under a wide range of load conditions and reduces the high circulating current in the freewheeling mode using the leakage resonant inductance and the series resonant capacitor. Thus, the proposed converter overcomes the drawbacks of the conventional full-bridge DC-DC converter and improves its overall system efficiency. Its structure is simplified by using the leakage inductance of the transformer as the resonant inductance and omitting the DC output filter inductance. Also it can operate over a wide range of input voltages. In this paper, the operational principle, analysis and design example are described in detail. Finally, the experimental results from a 650W (24V/27A) prototype are demonstrated to confirm the operation, validity and features of the proposed converter.

• Journal of Power Electronics
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• 제15권1호
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• pp.65-77
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• 2015

Resonant converters are well suited for induction heating (IH) applications due to their advantages such as efficiency and power density. The control systems of these appliances should provide smooth and wide power control with fewer losses. In this paper, a simple phase locked loop (PLL) based variable duty cycle (VDC) pulse density modulation (PDM) power control scheme for use in class-D inverters for IH loads is proposed. This VDC PDM control method provides a wide power control range. This control scheme also achieves stable and efficient Zero-Voltage-Switching (ZVS) operation over a wide load range. Analysis and modeling of an IH load is done to perform a time domain simulation. The design and output power analysis of a class-D inverter are done for both the conventional pulse width modulation (PWM) and the proposed PLL based VDC PDM methods. The control principles of the proposed method are described in detail. The validity of the proposed control scheme is verified through MATLAB simulations. The PLL loop maintains operation closer to the resonant frequency irrespective of variations in the load parameters. The proposed control scheme provides a linear output power variation to simplify the control logic. A prototype of the class-D inverter system is implemented to validate the simulation results.

• 한국정보통신학회논문지
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• 제20권9호
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• pp.1763-1770
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• 2016

본 논문에서는 넓은 출력 부하 전력에서도 동작하는 하이브리드 변환기를 제안했다. 스위치드 커패시터 변환기는 높은 부하 전력에서 효율이 낮고, 낮은 부하 전력에서는 효율이 높다. 반대로, 벅 변환기는 높은 부하 전력에서는 효율이 높고, 낮은 부하 전력에서는 효율이 낮다. 제안된 하이브리드 변환기는 스위치드 커패시터 변환기와 벅 변환기를 혼합했다. 낮은 부하 전력에서는 스위치드 커패시터 변환기를 동작시키고, 높은 부하에서는 벅 변환기를 동작시켜, 넓은 출력 부하 전력에서 전력 효율을 향상시켰다. 제안된 하이브리드 변환기는 $0.18{\mu}m$ CMOS 공정으로 구현되었다. 하이브리드 변환기의 출력 부하 전력 범위는 0.05~100mW 이며, 벅 변환기와 스위치드 커패시터 변환기에서 각각 93%와 77%의 최대 전력 효율을 가진다.

• Journal of Power Electronics
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• 제17권1호
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• pp.11-19
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• 2017

This paper proposes a dc/dc converter for electric vehicle onboard chargers using a secondary resonant tank. To attain soft switching characteristics, such as zero voltage switching, magnetizing inductance has been used at the primary side of the transformer. The leakage inductance of the transformer is used as a resonant inductor on the secondary side to avoid the use of a separate inductor as resonance. The proposed converter is applicable for a wide load range. A 6.6KW prototype has been implemented for a wide range of load variations (250V, 330V, 360V, and 413V). A maximum efficiency of 97.4% is achieved at 413V.

• 전력전자학회논문지
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• 제10권6호
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• pp.578-586
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• 2005

최근 디지털 방송의 시행에 따라 평판디스플레이(FPD)의 수요가 증가하고 있다. 그 중에서도 PDP는 대화면, 고감도, 넓은 시야각, 얇은 두께 등의 장점을 가지기 때문에 다른 FPD 매체들에 비해 경쟁력이 있다. 그리고 최근 PDP 패널의 공정 간소화로 인해 PDP 패널의 제작 비용이 감소하는 추세에 있기 때문에 대화면용 PDP에 관심이 집중되고 있다. 따라서 본 논문에서는 넓은 영전압 스위칭 범위를 갖는 대화면용 PDP 유지전원단을 위한 고효율 전력 변환회로를 제안하고 여러 가지 구동 신호를 인가하여 제안된 회로의 동작을 분석하였다. 기존의 42" PDP는 낮은 부하조건에 대해서 ZVS가 이루어지지 않게 되는데 시간에 따라서 급격하게 변하는 PDP의 부하 특성 때문에 많은 열이 발생하게 된다. 그러나 제안된 60" PDP 회로의 경우, 부가적으로 ZVS를 위한 에너지를 공급해 줄 수 있는 회로를 달아주었기 때문에 넓은 ZVS 영역을 갖게 된다. 그리고 이러한 장점 때문에 스위칭 손실이 감소하여 기존의 컨버터에 비해서 높은 효율을 기대할 수 있을 뿐만 아니라 심각한 열 문제가 없이 안정적인 조건에서 동작하는 것이 가능해 진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.182-185
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• 2005

This paper presents a new voltage current driven method for the synchronous rectifier (SR) in a flyback topology. The proposed synchronous rectfier of voltage-current driven can operate at wide load range with high efficiency. The gate voltage of FET in the synchronous rectifier is easily controlled by resistor ratio. regardless of line and load fluctuation. The 200W (l2V/17A) prototype is built and achiveved efficiency as high as 90% at 4A, 93.2% at 7A and full load.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.231-234
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• 2003

This paper presents a novel high frequency transformer linked full-bridge type soft-switching phase-shift PWM control scheme DC-DC power converter, which can be used as power conditioner fur small-scale fuel cell power generation system. Using full-bridge soft-switching DC-DC converter topology makes possible to use low voltage high performance MOSFETs to achieve high efficiency of the power conditioner. A tapped inductor filter is implemented in the proposed soft-switching converter topology to achieve soft-switching PWM constant high frequency operation for a wide load variation range. to minimize circulating and idling currents without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching DC-DC converter is verified in laboratory level experiment with 1 kW 100kHz breadboard setup using power MOSFETs. Actual efficiency of 94-96$\%$ is obtained for the wide load range