单相两级有源功率因数校正变换器的研究

文中对两级有源功率因数校正变换器进行研究,设计了一台510W两级式开关电源。该电源前级采用平均电流控制的Boost型PFC电路,实现功率因数校正;后级采用不对称半桥型DC／DC变换器,实现开关管的零电压开关。控制电路采用PFC／PWM复合控制芯片ML4824,缩小电源体积。通过实验证实该开关电源具有高功率因数与高效率的特点。     

ZVZCS single-stage PFC AC-to-DC half-bridge converter

A zero-voltage- and zero-current-switched single-stage AC-to-DC half-bridge converter with high power factor is presented to reduce the switching losses and to achieve sinusoidal, unity power factor input currents. The single-stage approach, which combines a boost converter used as power-factor correction with a half-bridge converter used as DC-to-DC conversion into one power stage, has a simple structure and low cost. At the same time, the switching losses could be considerably reduced, because the switches of the proposed converter are designed to be turned on at zero voltage and off at zero current. Detailed analysis and experimental results are presented on the proposed converter, which is operated at constant switching frequency and in discontinuous conduction mode     

Single-stage electronic ballast with high-power factor

This article proposes a single-stage electronic ballast circuit with high-power factor. The proposed circuit was derived by sharing the switches of the power factor correction (PFC) and the half-bridge LCC resonant inverter. This integration of switches forms the proposed single-stage electronic ballast, which provides an almost unity power factor and a ripple-free input current by using a coupled inductor without increasing the voltage stress. In addition, it realises zero-voltage-switching (ZVS) by employing the self-oscillation technique. The saturable transformer constituting the self-oscillating drive limits the lamp current and dominates the switching frequency of the ballast. Therefore, the proposed single-stage ballast has the advantage of high-power factor, high efficiency, low cost and high reliability. Steady-state analysis of the PFC and the half-bridge LCC resonant inverter are described. The results of experiments performed using a 30 W fluorescent lamp are also presented to confirm the performance of the proposed ballast.     

A single-stage power factor correction AC/DC converter based on zero voltage switching full bridge topology with two series-connected transformers

A single-stage power factor correction ac/dc converter based on zero voltage switching (ZVS) full bridge topology with two series-connected transformers is proposed in this paper. The proposed converter offers a very wide ZVS range due to the configuration of two series-connected transformers. It features a high efficiency over wide load ranges. Furthermore, it shows the low voltage stress on a dc link capacitor. The proposed converter also gives the high power factor and low input current harmonics complied with IEC 61000-3-2 Class D requirements by integrating a boost stage operated in a discontinuous current mode. The ZVS conditions, large signal modeling, and design procedure are discussed in detail. Experimental results are presented to show the validity of the proposed converter.     

一种有源钳位的半桥Boost变换器的研究

Boost电路和半桥、全桥电路相结合的电流馈电DC-DC变换器被广泛地使用在UPS、燃料电池等低输入电压、高输出电压的系统中。文中介绍了一种新型的有源钳位电路,在实现有源钳位的同时对所有的开关管实现了ZVS开通,提高了变换器的效率。     

Zero-voltage-switching half-bridge DC-DC converter with modified PWM control method

Asymmetric control scheme is an approach to achieve zero-voltage switching (ZVS) for half-bridge isolated dc-dc converters. However, it is not suited for wide range of input voltage due to the uneven voltage and current components stresses. This paper presents a novel "duty-cycle-shifted pulse-width modulated" (DCS PWM) control scheme for half-bridge isolated dc-dc converters to achieve ZVS operation for one of the two switches without causing the asymmetric penalties in the asymmetric control and without adding additional components. Based on the DCS PWM control scheme, an active-clamp branch comprising an auxiliary switch and a diode is added across the isolation transformer primary winding in the half-bridge converter to achieve ZVS for the other main switch by utilizing energy stored in the transformer leakage inductance. Moreover, the auxiliary switch also operates at ZVS and zero-current switching (ZCS) conditions. Furthermore, during the off-time period, the ringing resulted from the oscillation between the transformer leakage inductance and the junction capacitance of two switches is eliminated owing to the active-clamp branch and DCS PWM control scheme. Hence, switching losses and leakage-inductance-related losses are significantly reduced, which provides the converter with the potential to operate at higher efficiencies and higher switching frequencies. The principle of operation and key features of the proposed DCS PWM control scheme and two ZVS half-bridge topologies are illustrated and experimentally verified.     

Boost Converter With Coupled Inductors and Buck–Boost Type of Active Clamp

This paper proposes a boost converter with coupled inductors and a buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate the voltage spike that is induced by the trapped energy in the leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio even under high step-up applications, reducing voltage and current stresses significantly. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching, switching loss can be reduced, and conversion efficiency therefore can be improved significantly. A 200 W prototype of the proposed boost converter was built, from which experiment results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively. It is relatively feasible for low-input-voltage applications, such as fuel cell and battery power conversion.     

Design of a power-factor-correction converter based on half-bridgetopology

A single-stage AC/DC converter based on a half-bridge topology suitable for low-power-level applications is proposed. The proposed converter has high power factor, low harmonic distortion, and tight output regulations. An asymmetrical control and synchronous rectification are employed to reduce the switching and rectification losses, respectively. The modeling and detailed analysis are performed to derive the design equations. Based on these design equations, a prototype converter has been designed and tested by experiment. This prototype meets the IEC 61000-3-2 regulations with near-unity power factor and high efficiency     

A Three-Level Resonant Single-Stage Power Factor Correction Converter: Analysis, Design, and Implementation

This paper presents a new single-stage power factor correction ac/dc converter based on a three-level half-bridge resonant converter topology. The proposed circuit integrates the operation of the boost power factor preregulator and the three-level resonant dc/dc converter. A variable-frequency asymmetrical pulsewidth modulation controller is proposed for this converter. This control technique is based on two integrated control loops: the output voltage is regulated by controlling the switching frequency of the resonant converter, whereas the dc-bus voltage and input current are regulated by means of duty cycle control of the boost part of the converter. This provides a regulated output voltage and a nearly constant dc-bus voltage regardless of the loading condition; this, in turn, allows using smaller switches and consequently having a lower on resistance helping to reduce conduction losses. Zero-voltage switching is also achieved for a wide range of loading and input voltage. The resulting circuit, therefore, has high conversion efficiency making it suitable for high-power wide-input-voltage-range applications. The effectiveness of this method is verified on a 2.3-kW 48-V converter with input voltage (90–265 Vrms).      

SVM控制的复合有源箝位ZVS三相PFC变换器

采用复合有源箝位（CAC）的三相功率因数校正变换器，应用改进的空间矢量控制策略，所有的主开关和辅助开关均为零电压开关，有效的抑制了桥臂开关反并联二极管的反向恢复电流，减少反向恢复损耗。而且，具有开关器件电压应力较低，开关频率固定，输入波形质量好的特点。研制了一台基于DSP控制的10kW实验样机，分析了软开关过程及条件，得到了变换器效率同电路谐振参数之间的关系曲线。测量了软开关变换器的传导干扰频谱，验证了软开关变换器较硬开关变换器有更好的电磁兼容性。     

A leakage-inductance-based ZVS two-inductor boost converter with integrated magnetics

A two-inductor boost converter topology has conduction loss and transformer utilization advantages in converting low-voltage higher current inputs to high output voltages. In this letter, a new zero-voltage switching (ZVS) two-inductor boost converter with integrated magnetics is proposed. In the new topology, the two current source inductors, a resonant inductor and a two-winding transformer, are integrated into one single magnetic core with three windings. Two windings simultaneously perform the functions of the current source inductors and the transformer primary. The transformer leakage inductance forms the resonant inductance. This leads to a much more compact converter design with a significant reduction in the number of core and winding components. A theoretical analysis establishes the operating point of the ZVS converter. Both of the theoretical and experimental waveforms, including flux waveforms for the legs of the integrated core structure, are presented at the end of the letter.     

A Variable Frequency Phase-Shift Modulated Three-Level Resonant Single-Stage Power Factor Correction Converter

This paper presents a new single-stage three-level resonant power factor correction ac-dc converter suitable for high power applications (in the order of multiple kilowatts) with a universal input voltage range (90–265 Vrms). The proposed topology integrates the boost input power factor preregulator with a half-bridge three-level resonant dc-dc converter. The converter operation is controlled by means of a combination of phase-shift and variable frequency control. The phase-shift between the switch gate pulses is used to provide the required input current shaping and to regulate the dc-bus voltage to a set reference value for all loading conditions, whereas, variable frequency control is used to tightly regulate the output voltage. An auxiliary circuit is used in order to balance the voltage across the two dc-bus capacitors. Zero voltage switching (ZVS) is also achieved for a wide range of loading and input voltage by having a lagging resonant current in addition to the flowing of the boost inductor current through the body diodes of the upper pair of switches in the free wheeling mode. The resulting circuit, therefore, has high conversion efficiency and lower component stresses making it suitable for high power, wide input voltage range applications. The effectiveness of the proposed converter is verified by analysis, simulation, and experimental results.      

A digital power factor correction (PFC) control strategy optimized for DSP

A predictive algorithm for digital control power factor correction (PFC) is presented in this paper. Based on this algorithm, all of the duty cycles required to achieve unity power factor in one half line period are calculated in advance by digital signal processors (DSP). A boost converter controlled by these precalculated duty cycles can achieve sinusoidal current waveform. One main advantage is that the digital control PFC implementation based on this control strategy can operate at a high switching frequency which is not directly dependent on the processing speed of DSP. Input voltage feed-forward compensation makes the output voltage insensitive to the input voltage variation and guarantees sinusoidal input current even if the input voltage is distorted. A prototype of boost PFC controlled by a DSP evaluation board was set up to implement the proposed predictive control strategy. Both the simulation and experimental results show that the proposed predictive strategy for PFC achieves near unity power factor.     

Coupled Inductor Incorporated Boost Half-Bridge Converter With Wide ZVS Operation Range

A new boost half-bridge (BHB) converter is presented. It is composed of an additional diode and a coupled winding to the boost inductor of the BHB converter. Using the transferring of a boost inductor current to the coupled winding, the cancellation of zero-voltage-switching (ZVS) current, which always occurs in a conventional one, is prevented. Therefore, the ZVS operation is easily achieved by the leakage inductor current of the transformer. Furthermore, since the negatively built-up leakage inductor current of the boost winding helps the ZVS operation throughout a wide load range, the ZVS operation is always guaranteed.      

A single-switch continuous-conduction-mode boost converter with reduced reverse-recovery and switching losses

A single-switch continuous-conduction-mode boost converter with reduced reverse-recovery and switching losses is proposed. By utilizing the leakage inductances of a pair of coupled inductors and two additional rectifiers, the turn-off rates (di/dt) of the boost output rectifier and the additional rectifiers are slowed down to reduce the reverse-recovery loss. The boost power transistor is also operated under a low-voltage turn-on condition to reduce the switching loss. Experimental results are presented to confirm the theoretical analysis and the performance of the proposed converter.     

Interleaved ZVS Converter With Ripple-Current Cancellation

In this paper, an interleaved soft-switching converter with ripple-current cancellation is presented to achieve zero- voltage-switching (ZVS) turn-on and load current sharing. In order to achieve ZVS turn-on, an active snubber is connected in parallel with the primary winding of the transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance at the transition interval is used to realize ZVS turn-on of all switches. In order to achieve three-level pulsewidth-modulation (PWM) scheme, an addition fast-recovery diode is used in the converter. Three-level PWM scheme can reduce the ac ripple current on the output inductor such that the output inductor can be reduced. The current-doubler rectifier is adopted in the secondary side of the transformer to reduce the transformer secondary-winding current and output voltage ripple by canceling the current ripple of two output inductors. The output voltage is controlled at the desired value using the interleaved PWM scheme. These features make the proposed converter suitable for the dc-dc converter with high output current. The operation principles, steady state analysis, and design equations of the proposed converter are provided in detail. Finally, experiments based on a 600-W (12 V/50 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.     

A 1-MHz Zero-Voltage-Switching Asymmetrical Half-Bridge DC/DC Converter: Analysis and Design

The asymmetrical half-bridge (AHB) topology discussed in this paper is one of the complementary driven pulse-width modulated converter topologies, which presents an inherent zero-voltage switching (ZVS) capability. In the previous work, the ideal operation of the converter and the ZVS realization process have been analyzed. However, the influence of the circuit parasitics on the output voltage drop and the design constraints of the circuit parameters to ensure the ZVS operation have not been investigated. The minimum load needed to ensure the ZVS operation is also not readily available. This paper presents a detailed and practical design for a 1-MHz AHB converter. A revised voltage transfer ratio of the converter is derived considering the influence of circuit parasitics and the ZVS transition. Two circuit parameters responsible for maintaining the ZVS operation are the transformer leakage inductance and the interlock delay time between the gate signals of two switches. A design method of the two parameters is proposed, which can ensure the ZVS transition. The possible ZVS range of the load variation is also investigated. A 50-W AHB converter with 1-MHz switching frequency was constructed, and a maximum efficiency of 91% was achieved.     

A Novel High-Frequency Transformer-Linked Soft-Switching Half-Bridge DC–DC Converter With Constant-Frequency Asymmetrical PWM Scheme

This paper presents a novel soft-switching half-bridge dc–dc converter with high-frequency link. The newly proposed soft-switching dc–dc converter consists of a single-ended half-bridge inverter controlled by an asymmetrical pulsewidth-modulation scheme and a center-tapped diode rectifier. In order to attain the wide range of soft commutation under constant switching frequency, the single active edge-resonant snubber cell composed of a lossless inductor and a switched capacitor is employed for the half-bridge inverter leg, providing and assisting zero-current-switching operations in the switching power devices. The practical effectiveness of the proposed soft-switching dc–dc converter is demonstrated by the experimental results from an 800 W–55 kHz prototype. In addition, the feasibility of the dc–dc converter topology is proved from the viewpoints of the high efficiency and high power density.      

ZVT-PWM boost converter for unity power factor applications

A new single-phase ZVT-PWM boost converter with an active snubber is proposed to achieve unity power factor operations for a wide load range. The unique location of the resonant inductor and capacitor ensures that low switching stress and commutation losses are obtained in the converter. The proposed converter is suitable for high power factor correctors     

Single-stage line-coupled half-bridge ballast with unity power factor and ripple-free input current using a coupled inductor

A single-stage line-coupled half-bridge ballast with unity power factor and ripple-free input current using a coupled inductor is proposed. The proposed power-factor-correction circuit can achieve unity power factor and ripple-free input current using a coupled inductor. A saturable transformer constituting the self-oscillating drive limits the lamp current and dominates the switching frequency of the ballast. The proposed ballast has high energy efficiency, low cost, and high reliability compared to the conventional high-power-factor electronic ballasts. Experimental results obtained on a 30-W fluorescent lamp is discussed.