ZCS and ZVS power factor correction

This paper proposes a new passive snubber cell for an AC-DC power factor correction (PFC) converter circuit suitable for high power applications. The switch is made to turn ON under zero current switching (ZCS) and turn OFF under zero voltage switching (ZVS) conditions by the proposed passive snubber components. The snubber cell comprises of minimum components with load independent operations. The snubber cell is incorporated into the conventional AC-DC boost PFC converter to achieve a good power factor of near unity, regulated output DC voltage, sinusoidal input current, and low voltage and current stress on all the semiconductor components used. In this paper, the simulation results are provided for the proposed converter topology in detail with modes and governing equations.

In this paper, a single-stage bidirectional isolated direct-matrix-based AC-DC converter with a power factor correction is proposed. This AC-DC converter can control not only the DC output voltage or current, but also the AC grid current with a single conversion stage, which helps to achieve a higher power density with a lower complexity. A modulation scheme that can achieve a zero voltage switching (ZVS) or zero current switching (ZCS) operation in all switches is developed. Hence, the switching frequency of the converter can be increased higher, leading to the smaller passive components. The proportional-resonant (PR) controller is utilized to achieve the unity power factor and low total harmonic distortion (THD) current. The proposed topology has been verified by simulation results for a 3.3 kW system.

Bridgeless Cuk PFC converter with full load range soft switching operation by using a simple auxiliary circuit

This paper presents a dimmable charge-pump driver to power light-emitting diodes (LEDs) with power factor correction (PFC) and Zero Voltage Switching (ZVS). The proposed LED driver does not utilize electrolytic capacitors, providing a high useful lifetime, and it can stabilize the output current in open loop control without needing current sensors, which reduces the cost. The output power is proportional to the switching frequency, which allows the LEDs dimming. A prototype with 22 W was implemented and experimental results were discussed. The prototype presented a power factor of 0.996 and an efficiency of 89.5 %. The driver output power was reduced by more than 40% through the switching frequency while varying of 53 kHz to 30 kHz and the converter has continues to operate in ZVS.

A novel soft-switching single-phase three-arm AC voltage regulator (SSTAVR) is proposed in this paper. The proposed AC voltage regulator (AVR) uses a three-arm topology that operates as a rectifier and an inverter. The rectifier arm is switched at high switching frequency, to perform power factor correction and simultaneously transfer the power demand for the load to the DC link capacitor. The inverter arm is also switched at high switching frequency, for regulation of the output voltage. In order to achieve low switching losses and high efficiency, the common arm is switched at the line frequency. Using simple resonant units, the rectifier arm and the inverter arm are operated at zero-voltage-switching (ZVS) turn-on, while the auxiliary switches are operated at zero-current-switching (ZCS) turn-off. The three-arm topology reduces the number of switching devices. As a result, the system is also more reliable and cheaper. The proposed AVR can deliver a sinusoidal input current with unity power factor and good output voltage regulation. A unipolar PWM scheme reduces the input current and the output voltage harmonics. Some simulation results for the proposed SSTAVR, rated at 500 W and operated at 40 kHz, are presented for verification.

A novel approach of power factor correction (PFC) with a high-frequency resonant energy tank for the DC-link inverter is proposed. As compared with the conventional PFC techniques, this approach is advantageous of lower current stress, lower switching losses, and higher control flexibility. With carefully designed circuit parameters, the proposed topology can exhibit high power factor. The adopted PFC circuit is implemented on a series-parallel load resonant inverter as an illustrative example. The experimental results are provided to validate the theoretical analyses. It is proven that the PFC circuit can achieve nearly unity power factor and very low harmonic distortion

본 논문에서는 영전압 스위칭(ZVS)과 전류불연속 모드(DCM)에 의한 새로운 고효율의 DC-DC 컨버터에 대해 연구된다. 일반적으로 고효율의 컨버터를 만들기 위해서는 전력변환기내에 사용된 반도체 스위칭 소자의 손실을 최소화하여 이루어진다. 제안한 컨버터는 DCM에 의하여 스위치의 턴-온 동작을 영전류 스위칭(ZCS)으로 만들고, 또한 새로운 유사공진 회로를 접목하여 컨버터의 고효율을 실현시킨다. 제안한 컨버터에 사용된 제어용 스위칭 소자들은 유사공진 기법에 의해 소프트 스위칭, 즉 ZVS와 ZCS으로 동작시키고, 이에 따른 제어용 스위칭 소자들은 전압과 전류의 스트레스 없이 동작한다. 그 결과 제안한 컨버터는 스위칭 손실의 저감에 의해 고효율로 구동된다. 제안한 DCM-ZVS 컨버터의 소프트 스위칭 동작과 시스템 효율은 디지털 시뮬레이션과 실험결과를 통해 그 타당성이 입증된다. This paper is study on a new high efficiency DC-DC converter of discontinuous conduction mode (DCM) with zero voltage switching (ZVS). The converters of high efficiency are generally made that the power loss of the used semiconductor switching devices is minimized. The proposed converter is accomplished that the turn-on operation of switches is on zero current switching (ZCS) by DCM. The converter is also applicable to a new quasi-resonant circuit to achieve high efficiency converter. The control switches using in the converter are operated with soft switching, that is, ZVS and ZCS by quasi-resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the converter is high. The soft switching operation and the system efficiency of the proposed DCM-ZVS converter are verified by digital simulation and experimental results.

The paper presents a single-stage high-power-factor electronic ballast for metal halide lamps. The proposed ballast integrates a buck-boost converter, a buck converter and a full-bridge inverter into a single power conversion circuit. The buck-boost converter served as a power-factor corrector (PFC) is designed to operate at discontinuous conduction mode (DCM) to achieve nearly a unity power factor at the input line. By adjusting the duty-ratio of the active switches of the PFC, the lamp power is remained at rated value for universal input voltage ranged from 90 V rms to 264 V rms . The four active switches of the full-bridge inverter, an inductor and a capacitor form a bidirectional buck converter which supplies a low frequency square-wave current for the lamp at to avoid the lamp from happing acoustic resonance. The circuit operation is analyzed in detail to derive the design equations. A prototype electronic ballast for a 70 W metal halide lamp is built and tested. Experimental measurements are provided to verify that the proposed ballast has the merits of a nearly unity input power factor, high circuit efficiency and the metal halide lamp is free of acoustic resonance.

The inherent dead angles of the input line current in buck power factor correction (PFC) converter deteriorates the power factor (PF). This article introduces a new bridgeless single-phase buck (PFC) converter with reduced components. This converter is designed to operate in discontinuous conduction mode (DCM) to achieve inherent PFC with a simple structure. The DCM operation gives additional advantages, such as low turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> losses and reduced complexity of the control circuitry. Unlike the buck PFCs, in which dead angle is the main drawback, in the proposed converter the PF is improved and the dead angle is eliminated by applying an auxiliary switch. Besides, the efficiency is further improved by employing the bridgeless structure. The switching losses are eliminated due to achieved zero current switching (ZCS) at the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> of the main switches, and also ZCS at the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and zero voltage switching at turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> of the auxiliary switch. The proposed topology is successfully implemented on a 120 W prototype converter at 110 Vrms input voltage and 48 V output voltages, and its performance is experimentally verified. The results show the total harmonic distortion of 5.3% and efficiency of 93.1% at the rated load.

In this paper, a modified SEPIC converter is presented to function as a power factor corrector (PFC). The modified SEPIC-type PFC not only can achieve unity power factor but reduce dc-link voltage to release component stresses. Therefore, it is suitable for high line-voltage applications. A soft-switching cell composed of an active switch and an inductor-capacitor resonant circuit is embedded into the PFC to obtain zero-voltage switching (ZVS) feature. As a result, the efficiency of the converter is improved significantly. Operation principles are discussed in detail and conceptual key waveforms are also shown in this paper. A prototype is designed, analyzed and implemented. The simulation results and practical measurements have verified the feasibility of the proposed modified soft-switching SEPIC converter.

The series resonant, parallel loaded LLC with voltage in- and output has widely been studied and used for DC-DC power conversion applications. In contrast, this paper considers the standard LLC in the AC-DC case, which means a far wider input voltage range from the peak mains down to approximately zero. Beside the question whether and how the standard LLC converter can handle the resulting large gain ratios e.g., in the context of a power factor correction (PFC) application, it needs to be explored whether zero-voltage switching (ZVS) can always be achieved, especially regarding the highly nonlinear output capacitances of superjunction MOSFETs. To comprehensively deal with the variety of operation conditions, the converter design choices and the inverter devices, an analytical description is preferred over approaches merely based on circuit simulations. Thereto, a system of equations firstly describes the ideally switching steady state. This model is linked to a linearized inverter transition model for ZVS assessment is used to refine the solution space for the converter design. Three ways to extract that inverter model from the MOSFETs' output CV-characteristic are compared that all can predict ZVS but differ in complexity.

A novel three-phase full-bridge power factor corrector is presented in this paper. The corrector operates in discontinuous conduction mode (DCM), the peak of input current follows the input voltage automatically. It can achieve zero-voltage-switching (ZVS) for the leading-leg switches and zero-current-switching (ZCS) for the lagging-leg switches without adding any auxiliary device. Due to the adoption of high frequency transformer, the electrical isolation between input and output sides and output voltage regulation could be achieved. The corrector is very suitable for charging systems. It can reduce the voltage stress of the switches of the DC/DC converters used in the later stage as well as achieve a high power factor (PF) in the input side. Some introduction and analysis about the corrector has been given. Finally, the analysis on this corrector has been verified through simulation and experiment.

This paper provides a novel soft-switching half-bridge power factor corrector (PFC) with output voltage balance control using zero-current-switching (ZCS) auxiliary resonant circuits. In proposed soft-switching PFC, ZCS's on the active switches are achieved without additional current stress. The steady-state analysis is performed for operation illustration and the small-signal analysis is also built up for output regulation control. An average-current-mode for power factor correction is utilized to control the proposed soft-switching half-bridge PFC in the continuous conduction mode. The balance control technique is designed to overcome the two output capacitor voltage imbalance that is inherent in half-bridge topology. The operational principles, design considerations and realizations are discussed and verified. The prototype specification of the proposed soft-switching half-bridge PFC is rated at 400W and operates at 30kHz, with an input ac voltage of 110V rms and a regulated output voltage 400V dc , for experiments to verify the theoretic analysis.

The use of silicon carbide diodes as alternatives to standard silicon power diodes in a zero-voltage switched (ZVS) 800W boost power factor correction (PFC) converter is examined experimentally. The PFC circuit examined is a part of a base station power supply. Efficiency improvement by using SiC diodes in hard-switched PFC boost power converters has been demonstrated by others, and is considered by many to be an ideal solution. Incorporating SiC diodes in a ZVS topology further improves the performance of the topology. Comparisons are made between ZVS circuits using standard silicon power diodes and an equivalent circuit using SiC diodes. Simplification of the overall circuit, improvement in operating efficiency and improvements in line conducted EMC performance are observed. The paper concludes that the use of SiC diodes in high wattage applications can further improve performance characteristics of ZVS PFC boost converters.

This paper presents a new modulation method for the cycloconverter stage of the high frequency (HF) link AC-DC rectifier. The method takes advantage of the parasitic parameters of the circuit to provide zero current switching (ZCS) for the AC-and zero voltage switching (ZVS) of the DC-side transistors. Regulation with the power factor correction (PFC) is ensured using only one control variable and no external auxiliary or snubber circuits are required. Moreover, 1/4 of the AC-side transistors are operating with fundamental frequency. The proposed modulation strategy and its design constraints are analysed mathematically and verified with the simulation model of 1 kW, 230 VAC/48 VDC HF-link converter.