Input impedance analysis of single-phase PFC converters

The input impedance of single-phase boost power factor corrected (PFC) AC-DC converters is modeled and analyzed in this paper. A large-signal model is presented for the input impedance which overcomes the limitations of traditional piece-wise linearized models. The model is valid at frequencies ranging from the crossover frequency of the output voltage loop to half the switching frequency of the converter. Experimental results from a boost single-phase PFC converter are provided to validate the model. Input characteristics of typical boost PFC converters, such as input impedance dipping, leading phase of the input current, and responses to distorted input voltages are studied by using the model. A simple compensation technique to reduce the dipping in the input impedance, thereby improving converter performance and minimizing the potential for undesirable interactions with the input filter or the ac source, is also presented.     

On the zero-crossing distortion in single-phase PFC converters

Input current distortion in the vicinity of input voltage zero crossings of boost single-phase power factor corrected (PFC) ac-dc converters is studied in this paper. Previously known causes for the zero-crossing distortion are reviewed and are shown to be inadequate in explaining the observed input current distortion, especially under high ac line frequencies. A simple linear model is then presented which reveals two previously unknown causes for zero-crossing distortion, namely, the leading phase of the input current and the lack of critical damping in the current loop. Theoretical and practical limitations in reducing the phase lead and increasing the damping factor are discussed. A simple phase compensation technique to reduce the zero-crossing distortion is also presented. Numerical simulation and experimental results are presented to validate the theory.     

Duty-ratio feedforward for digitally controlled boost PFC converters

When a "classical" current control scheme is applied, the line current of a boost power-factor-correction (PFC) converter leads the line voltage, resulting in a nonunity fundamental displacement power factor and in important zero-crossing distortion in applications with a high line frequency (e.g., 400-Hz power systems on commercial aircraft). To resolve this problem, a current-control scheme is proposed using duty-ratio feedforward. In this paper, the input impedance of the boost PFC converter for both the classical current-loop controller and the controller using duty-ratio feedforward are derived theoretically. A comparison reveals the advantages of the proposed control scheme: a low total harmonic distortion of the line current, a resistive input impedance, virtually no zero-crossing distortion, and a fundamental displacement power factor close to unity. The theoretical results obtained are verified using an experimental setup of a digitally controlled boost PFC converter.     

一种用于单相Boost型PFC中的数字预测算法

本文提出了用于数字控制PFC中的一种新颖的数字控制算法,称为预测算法。它可以得到较高的PF值,并且随着输入电压或者负载电流的变化有近似最快的动态响应。对于一个确定的系统,预测算法根据系统当前的状态参数,可以估算出输出电压和电感电流在下一个开关周期的变化趋势,并且得到一组完美跟踪输入电压轨迹最优的控制序列。在多种仿真条件下的仿真结果证实了预测算法的有效性。当输入电压从90V到265V,负载电流从20%~100%范围变化时,PF值都大于0.998。启动时间和恢复时间分别约为0.1s和0.02s,且无超调。实验结果也验证了设计的有效性。     

A sampling algorithm for digitally controlled boost PFC converters

Digital control of a boost power factor correction (PFC) converter requires sampling of the input current. As the input current contains a considerable amount of switching ripple and high frequency switching noise, the choice of the sampling instant is very important. To avoid aliasing without employing a (very) high sampling frequency, the sampling is synchronized with the pulse width modulation (PWM). Sampling algorithms employing this technique successfully reject the input current ripple but are not immune to the high frequency switching noise present on all sampled signals. Therefore, a new sampling algorithm, called alternating-edge-sampling and intended for center-based or symmetric PWM, is deduced with as most important features: switching noise immunity, straightforwardness, accurate measurement of the averaged input current and the need for only few processor cycles. The operating principle, design issues and a theoretical study of the input current error induced by the sampling algorithm due to sampling instant timing errors are derived. All theoretical results are validated experimentally for a digitally controlled boost PFC converter switching at 50 kHz.     

High static gain single-phase PFC based on a hybrid boost converter

In this paper, a single-phase unity power factor rectifier, based on a hybrid boost converter, resulting from the integration of a conventional dc–dc boost converter and a switched-capacitor voltage doubler is proposed, analysed, designed and tested. The high-power rectifier is controlled by two feedback loops with the same control strategy employed in the conventional boost-based rectifier. The main feature of the proposed rectifier is its ability to output a dc voltage larger than the double of the peak value of the input line voltage, while subjecting the power switches to half of the dc-link voltage, which contributes to reducing the cost and increasing the efficiency. Experimental data were obtained from a laboratory prototype with an input voltage of 220 Vrms, line frequency of 60 Hz, output voltage of 800 Vdc, load power of 1000 W and switching frequency of 50 kHz. The efficiency of the prototype, measured in the laboratory, was 96.5% for full load and 97% for half load.     

Comprehensive review of high power factor ac-dc boost converters for PFC applications

High power factor rectifiers have been consolidated as an effective solution to improve power quality indices in terms of input power factor correction, reduction in the total harmonic distortion of the input current and also regulated dc voltages. Within this context, this subject has motivated the introduction of numerous converter topologies based on classic dc-dc structures associated with novel control techniques, thus leading to the manufacturing of dedicated integrated circuits that allow high input power factor by adding a front-end stage to switch-mode converters. In particular, boost converters in continuous current mode (CCM) are widely employed since they allow obtaining minimised electromagnetic interference levels. This work is concerned with a literature review involving relevant ac-dc single-phase boost-based topologies with high input power factor. The evolution of aspects regarding the conventional boost converter is shown in terms of improved characteristics inherent to other ac-dc boost converters. Additionally, the work intends to be a fast and concise reference to single-phase ac-dc boost converters operating in CCM for engineers, researchers and experts in the field of power electronics by properly analysing and comparing the aforementioned rectifiers.     

Dynamics and control of ZCZVT boost converters

In this paper, the small-signal mathematical model of a zero-current-zero-voltage-transition (ZCZVT) soft-switching boost power converter is proposed. It shows that the ZCZVT boost converter exhibits better dynamic behavior than the conventional pulsewidth modulated boost converter. The input-to-output voltage conversion ratio of the ZCZVT soft-switching converters lies in a range which is related to the load. Based on the derived model, a classical controller and a modified integral variable structure controller are designed to achieve output voltage regulation and line voltage disturbance rejection. The experimental results regarding converters performances for two controllers are compared by experimental results.     

交错并联PFC变换器的预测控制研究

针对交错并联图腾柱PFC拓扑在电感电流连续导电模式CCM(Continue Conduction Mode)下,占空比预测控制中系统存在二次谐波以及特定次谐波的问题,设计对特定频率谐波有良好跟踪特性的PR控制器,补偿占空比预测控制的谐波分量。同时,在电压外环中设计陷波器,对特定次谐波进行滤波和反馈补偿。仿真实验结果证明,基于PR控制器与陷波器的占空比预测控制系统,在保留了系统快速动态性的基础上,输入电流很好的得到滤波,电流的THD(Total Harmonic Distortion)值明显减小,谐波含量降低,提高了输入电能的质量,实现PFC功能。     

Third-harmonic supply current minimization in single-phase AC/DC converters

One effect of the second-harmonic in the load-side current ripple of a single-phase AC/DC converter is to introduce an unwanted third-harmonic into the supply-side current. Although this can be neither eliminated nor reduced by either conventional selective harmonic or natural sinusoidal PWM strategies, it is shown that the use of a modified switching function in the selective strategy enables a considerable reduction to be achieved. Possible applications for the new strategy include single-phase AC/DC converter-fed DC drives and converters providing a DClink for inverter-fed DC drives.     

Techniques for minimizing the input current distortion ofcurrent-controlled single-phase boost rectifiers

Techniques for minimizing the input current distortion of current-controlled single-phase boost rectifiers are described. The switching patterns of several boost rectifiers are examined to identify the nature of their input current waveforms. This analysis is used to examine the low-frequency current distortion levels, and hence the power quality, associated with the rectifiers. A PWM (pulse width modulation) strategy that selectively switches between positive unipolar PWM and negative unipolar PWM, called phase-adjusted unipolar PWM, is shown to produce the lowest current distortion levels. A novel two-switch asymmetrical half-bridge rectifier is presented that draws an input current at a unity fundamental power factor and with the same low distortion as obtained with the four-switch H-bridge rectifier. The operation of the various rectifiers is examined with reference to theoretical predictions, circuit simulations, and experimental results. This analysis is used to compare the performances of the various rectifier switching patterns     

Optimal current programming in three-phase high-power-factorrectifier based on two boost converters

Current programming in a three-phase high-power-factor rectifier based on two boost converters is discussed in this paper. It is shown that the converter currents can be expressed in terms of two mutually related auxiliary functions. The auxiliary functions are related to the input current spectrum. Optimal auxiliary functions that eliminate harmonics of the input currents are derived. A method to generate reference signals for the optimal current programming is proposed. Experimental results confirming the proposed concepts are presented     

Switch failure diagnosis based on inductor current observation for boost converters

Face to the growing number of applications using DC–DC power converters, the improvement of their reliability is subject to an increasing number of studies. Especially in safety critical applications, designing fault-tolerant converters is becoming mandatory. In this paper, a switch fault-tolerant DC–DC converter is studied. First, some of the fastest Fault Detection Algorithms (FDAs) are recalled. Then, a fast switch FDA is proposed which can detect both types of failures; open circuit fault as well as short circuit fault can be detected in less than one switching period. Second, a fault-tolerant converter which can be reconfigured under those types of fault is introduced. Hardware-In-the-Loop (HIL) results and experimental validations are given to verify the validity of the proposed switch fault-tolerant approach in the case of a single switch DC–DC boost converter with one redundant switch.     

Low-power variable frequency PFC converters

Based on the SinoMOS 1 μm 40 V CMOS process, a novel power factor corrention (PFC) converter with a low-power variable frequency function is presented. The circuit introduces a multi-vector error amplifier and a pro-grammable oscillator to achieve frequency modulation, which provides a rapid dynamic response and precise output voltage clamping with low power in the entire load. According to the external load variation, the system can modulate the circuit operating frequency linearly, thereby ensuring that the PFC converter can work in frequency conversion-mode. Measured results show that the normal operating frequency of the PFC converter is 5-6 kHz, the start-up current is 36 μA, the stable operating current is only 2.43 mA, the efficiency is 97.3%, the power factor (PF) is 0.988, THD is 3.8%, the load adjust rate is 3%, and the linear adjust rate is less than 1%. Both theoretical and practical results reveal that the power consumption of the whole supply system is reduced efficiently, especially when the load varies. The active die area of the PFC converter chip is 1.61×1.52 mm~2.     

低功耗变频PFC转换器的研究

基于SinoMOS 1µm 40V CMOS工艺,设计实现了一种新颖的低功耗变频PFC转换器。电路采用多矢量误差运放和可编程锯齿波振荡器结构,以获得可调频率,为PFC系统提供了快速的动态响应和精确的输出电压嵌位,同时实现了低功耗。系统能够根据外接负载的变化情况而线性调整电路的工作频率,保证PFC芯片工作在变频模式下,因此当负载变化时,整个电源系统的功率损耗能有效降低,从而提高有用功率。测试结果表明：系统正常工作频率为5~6kHz,启动电流36µA,稳定工作电流2.43mA,功率校正因数值为0.988,线性调整率小于1%。理论和实际结果均显示整个电源系统的功耗被有效降低,尤其当负载变化时。芯片有效面积为1.61mm×1.52mm。     

Voltage loop of boost PWM DC-DC converters with peak current-mode control

A new transfer function from control voltage to duty cycle, the closed-current loop, which captures the natural sampling effect is used to design a controller for the voltage-loop of a pulsewidth modulated (PWM) dc-dc converter operating in continuous-conduction mode (CCM) with peak current-mode control (PCM). This paper derives the voltage loop gain and the closed-loop transfer function from reference voltage to output voltage. The closed-loop transfer function from the input voltage to the output voltage, or the closed-loop audio-susceptibility is derived. The closed-loop transfer function from output current to output voltage, or the closed loop output impedance is also derived. The derivation is performed using an averaged small-signal model of the example boost converter for CCM. Experimental verification is presented. The theoretical and experimental results were in good agreement, confirming the validity of the transfer functions derived.     

Power-efficient gate control of synchronous boost converters with high output voltage

A half output voltage swing gate driving scheme is presented for high voltage single chip DC/DC converters. In the proposed scheme the energy for the PMOS gate drive is reused for the NMOS gate drive, and switching loss is reduced. A high speed and area-efficient high voltage level shifter is also realised. A prototype is implemented using a 0.5 mum 40 V power BiCMOS process     

DC voltage sensorless single-phase PFC converter

We propose a simple DC voltage sensorless single phase PFC converter by detecting an AC line voltage waveform. Both DC voltage and AC current sensors used in the conventional PFC converter are not required to construct the control system. The conventional converter circuit with a boost chopper circuit in the DC side from a rectifier circuit is used as the main PFC converter circuit. In the control system, the circuit parameters such as a series inductance L and equivalent load resistance value R/sub d/ are used to generate the sinusoidal current waveform. The DC voltage is directly controlled by the command input signal k/sub d/(=E/sub d//E/sub a/) for the boost chopper circuit. The DC voltage regulation is small because of the feed forward control for the AC line voltage E/sub a/ and no dependence of the circuit parameters. The sinusoidal current waveform in phase with the AC line voltage can be obtained. The feasibility of the proposed control system is verified by some simulation and experimental results.     

H∞ control applied to boost power converters

The controller in a pulse-width-modulation (PWM) power converter has to stabilize the system and guarantee an almost constant output voltage in spite of the perturbations in the input voltage and output load over as large a bandwidth as possible. Boost and flyback power converters have a right-half-plane zero (RHPZ) in their transfer function from the duty cycle to the output voltage, which makes it difficult to achieve the aforementioned goals. Here, the authors propose to design a controller using H^∞ control theory, via the solution of two algebraic Riccati equations. The almost optimal H^∞ controller is of the same order as the converter and has a relatively low DC gain. The closed-loop characteristics of a typical low-power boost power converter with four different control schemes were compared by computer simulation. The H^∞ control was found to be superior in a wide frequency range, while being outperformed by the others at extremely low frequencies. Good agreement was found between simulation results and experimental measurements     

Current control with fast transient for three-phase AC/DC boost converters

This letter introduces a new synchronous reference frame hysteresis control of a three-phase ac/dc boost converter that is demonstrated to have excellent transient behavior when compared with previous fast methods based on regular proportional plus integral control with cross-coupling terms. Finally, the control software program and a comparison of results are shown.