• Journal of Power Electronics
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• 제13권4호
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• pp.592-599
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• 2013

This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 $V_{rms}$) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.79-86
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• 2013

In order to analyze the electrical performance of ZnO surge arresters stressed by the combined DC and AC voltages that are generated in DC/AC converter systems, the leakage current properties of ZnO surge arrester blocks deteriorated by impulse currents were investigated. The test specimens were deteriorated by the 8/$20{\mu}s$ impulse current of 2.5kA and the leakage currents flowing into the deteriorated zinc oxide(ZnO) arrester blocks subjected to the combined DC and power frequency AC voltages are measured. As a result, the leakage currents flowing through deteriorated ZnO surge arrester blocks were higher than those flowing through the fine ZnO surge arrester blocks and the larger the injection number of 8/$20{\mu}s$ impulse current of 2.5kA is, the greater the leakage current is. The leakage current-voltage curves(I-V curves) of the fine and deteriorated ZnO surge arrester blocks stressed by the combined DC and AC voltages show significant difference in the low conduction region. Also the cross-over phenomenon is observed at the voltage close to the knee of conduction on plots of I-V curves.

• Journal of Power Electronics
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• 제15권2호
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• pp.356-365
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• 2015

This paper presents a new single phase front-end ac-dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.266-269
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• 2000

This paper presents a novel single-stage unity power factor converter which features the reduced switching losses by zero-voltage switching and zero-current switching (ZVZCS). Hence the turn-on and turn-off losses of switches are sufficiently reduced. And the reduced conduction losses are achieved by the elimination of one leg of front-end rectifier. And low on-resistance MOSFETs (Synchronous Rectifier) are used in the rectifier at the secondary side of high frequency transformer instead of diodes. Theoretical analysis simulated results of a AC to DC 150W(5V, 30A) converter are presented.

• Journal of Power Electronics
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• 제3권4호
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• pp.249-258
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• 2003

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.286-288
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• 2007

The proposed method offers an improved control method for high power density AC/DC adapter by using more energy efficient electrical equipments. Power factor corrector (PFC) topology is based on boost topology with boundary conduction mode (BCM). DC/DC topology is based on half-bridge topology with newly introduced off-time control method, which helps to reduce size of the semiconductor and the magnetic devices. Test results with 85W AC/DC adapter (18.5V/4.6A) design shows that the measured efficiency is 90% with power density of $36W/in^3$. It also show low no load power consumption of about 0.5W.

• 수산해양교육연구
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• 제9권2호
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• pp.209-221
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• 1997

This paper presents a soft switching unity power factor PWM rectifier, which features reduced conduction losses and soft switching with no auxiliary switches. The soft switching are achieved by using a simple commutation circuit with no auxiliary switches, and reduced conduction loses are achieved by employing a single converter, instead of a typical front end diode rectifier followed by a boost rectifier. Furthermore, thanks to good features such as simple PWM control at constant frequency, low switch stress and low VAR rating of commutation circuits, it is suitable for high power applications. The principle of operation is explained in detail, and major characteristics analysis and experimental results of the new converter also included.

• 전력전자학회논문지
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• 제23권5호
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.610-614
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• 2004

Recently, an active-clamp, full-bridge boost converter has been actively studied for high-power applications such as power factor correction and battery discharger. However, DC and AC modeling for this converter has not conquered. In this paper, a DC and small-signal AC modeling for the active-clamp, full-bridge boost converter is described. Based on the operation principle, the ac part of the converter can be replaced by a do 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.