• Journal of Power Electronics
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• 제14권5호
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• pp.890-898
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• 2014

Critical conduction mode boost power factor correction converters operating at the boundary of continuous conduction mode and discontinuous conduction mode have been widely used for power applications lower than 300W. This paper proposes an enhanced variable on-time control method for the critical conduction mode boost PFC converter to improve the total harmonic distortion characteristic. The inductor current, which varies according to the input voltage, is analyzed in detail and the optimal on-time is obtained to minimize the total harmonic distortion with a digital controller using a TMS320F28335. The switch on-time varies according to the input voltage based on the computed optimal on-time. The performance of the proposed control method is verified by a 100W PFC converter. It is shown that the optimized on-time reduces the total harmonic distortion about 52% (from 10.48% to 5.5%) at 220V when compared to the variable on-time control method.

• Journal of Power Electronics
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• 제10권2호
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• pp.132-137
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• 2010

Interleaving techniques are widely used to reduce input/output ripples and to increase the power capacity of boost converters operating in critical conduction mode. Two types of phase-shift control schemes are studied in this paper, the turn-on time shifting method and the turn-off time shifting method. It is found that although the turn-off time shifting method exhibits better performance, it suffers from sub-harmonic oscillations at high input voltages. To solve this problem, an intensive quantitative analysis of the sub-harmonic oscillation phenomenon is made in this paper. Based upon that, a novel modified turn off time shifting control scheme for interleaved boost converters operating in critical conduction mode is proposed. An important advantage of this scheme is that both the master phase and the slave phase can operate stably in critical conduction mode without any oscillations in the full input voltage range. This method is implemented with a FPGA based digital PWM control platform, and tests were carried out on a two-phase interleaved boost PFC converter prototype. Experimental results demonstrated the feasibility and performance of the proposed phase-shift control scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.129-133
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• 2005

This paper discusses DC/DC converter modeling using average model of switch and critical characterist. Average model of switch approach is expended to the modeling of boundary conduction mode DC/DC converters that operate at the boundary between Continuous Conduction Mode(CCM) and Discontinuous Conduction Mode(DCM). Frequency responses predicted by the average model of switch are verified by simulation and experiment.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.601-608
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• 2005

This paper presents a novel single-stage high-power-factor electronic ballast for fluorescent lamps operating in critical conduction mode. The proposed topology is based on integration of boost converter as power factor corrector(PFC) and a half-bridge high frequency parallel resonant inverter into a single stage. The input stage of the boost converter is operating in critical conduction mode for positive and negative half cycle voltage respectively at line frequency(60Hz). So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. The simulated and experimental results for 100W fluorescent lamps operating at 42kHz switching frequency and 220V line voltage have been obtained. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, fluorescent lamp and DC-DC converter etc.

• 한국산학기술학회논문지
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• 제11권7호
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• pp.2570-2578
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• 2010

본 논문에서는 임계전류도통모드로 동작하는 디지털제어 단상 역률개선(PFC; power-factor correction) 컨버터를 제안한다. 제안한 컨버터는 PFC를 위하여 DC-DC 부스트 컨버터 구조를 이용하며 인덕터전류를 임계도통모드로 동작시킨다. 또한 제안한 컨버터는 마이컴을 이용하여 디지털적으로 제어되기 때문에 제어회로는 간단해지고 컨버터는 더욱 효과적으로 동작한다. 본 논문에서는 먼저 제안한 컨버터의 동작원리를 설명하고 회로를 해석한다. 그리고 본 논문은 제안한 컨버터의 구현방법을 소프트웨어와 회로설계 부분으로 구분하여 구체적인 설계예와 함께 설명한다. 또한 설계된 회로파라미터에 의한 프로토타입 컨버터의 실험결과로 제안한 컨버터가 단상 PFC 컨버터로써 좋은 동작 특성을 가지고 있음을 보인다.

• 조명전기설비학회논문지
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• 제22권6호
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• pp.34-43
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• 2008

상태 공간 평균화 모델은 강압형, 승압형 및 승 강압형 DC/DC 컨버터에 적용이 가능하며, 특별한 계산이 필요 없는 높은 정밀도가 증명된 모델이다. 이러한 모델은 전류연속모드(CCM) DC/DC 컨버터에서 확립되었으며, 본 논문에서는 컨버터의 전류연속모드(CCM) 모델로부터 의미 있는 결론을 유도하고자 한다. 본 논문에서는 스위치 평균모델을 이용한 DC/ DC 컨버터의 전류불연속모드(DCM) 모델링 및 임계특성에 관하여 논하였다. 스위치 평균 모델은 전류연속모드(CCM)와 전류불연속모드(DCM) 사이의 DC/DC 컨버터의 경계 조건에 대한 모델로부터 유추할 수 있으며, 시뮬레이션과 실험에 의해서 스위치의 평균 모델의 주파수 응답 특성을 예측할 수 있었다. 본 연구에서는 MOSFET를 사용하여 입력전압 15[V], 출력전압 24[V], 출력전력 24[W]급 시스템을 제작하여 실험하였다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2310-2318
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• 2018

Critical conduction mode (CRM) operation is more efficient than continuous conduction mode (CCM) operation at low power levels because of the valley switching of switches and elimination of the reverse recovery losses of boost diodes. When using a sensorless digital control method, an error occurs between the actual and the estimated current. Because of the error, it operates as CCM or discontinuous conduction mode (DCM) during CRM operation and also has an adverse effect on THD of input current. In this paper, a current sensorless technique is presented in an inverter system using a bridgeless boosted power factor correction converter, and a compensation method is proposed to reduce CRM calculation error. The validity of the proposed method is verified by simulation and experiment.

• 전자공학회논문지
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• 제50권8호
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• pp.151-161
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• 2013

본 논문에서는 입력전압을 감지하지 않는 전류연속/임계동작모드 active power factor correction(PFC) circuit을 제안하였다. 기존의 입력전압을 감지하지 않는 PFC circuit의 경우 출력전류가 낮은 경 부하 조건에서 DCM 동작을 수행하고, 이에 따라 PF가 감소하는 문제가 발생한다. 제안한 PFC circuit은 70KHz의 주파수로 CCM 동작을 수행하고, 경 부하 조건에서 최대 200KHz까지 스위칭 주파수가 가변되는 CRM 동작을 수행하도록 하였다. 이를 통해 경 부하 조건에서 PF가 감소하는 문제를 해결하였다. PFC controller IC는 $0.35{\mu}m$ BCDMOS 공정을 이용하여 제작하였으며, 240W급 PFC prototype을 제작하여 실험하였다. 제안한 PFC circuit은 기존의 PFC circcuit 대비 최대 10%의 역률이 향상되었고, IEC 61000-3-2 Class D 규격에 따른 경 부하 조건에서는 최대 4% 역률이 향상되었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.147-148
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• 2011

In this paper, implementation of digital control for critical conduction mode power factor correction (PFC) rectifier is presented. Critical conduction mode is widely used in medium and low power conversion application due to its minimized MOSFET turn-on loss and diode reverse-recovery problem. However, it needs additional zero current detection circuit and maximum frequency limit to properly turn the MOSFET on and avoid the excessive switching loss in light load operation. This paper explains the digital IC implementation and verifies its operation with 200-W prototype PFC rectifier.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1126-1128
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• 2001

A single-stage high-power-factor electron ic ballast operating in critical conduction mode is presented in this paper. The proposed topology is based on integration of a boost-like converter and a LCC Type half-bridge serial resonant inverter. The power-factor-correction(PFC) stage is a boost-like converter operating in critical conduction mode for positive and negative half cycle voltage respectively at line frequency (60Hz) so that a high power factor is achieved naturally. The simulated and experimental results for 100w fluorescent lamps operating at 42kHz switching frequency and 220V line voltage have been obtained.