Analysis of a soft-switched PFC boost converter using analog and digital control circuits

This work presents a comparison between analog and digital (PIC16c73a) control types applied to the boost converter with a nondissipative snubber. Both control types use the bang-bang hysteresis current waveshaping control technique in order to achieve a quasi-unity power factor. The analog control applied presented a high power factor (0.998), high efficiency (92.87%), and low harmonic distortion [total harmonic distortion of current (THDI =2.84% and total harmonic distortion of current (THDV) =2.83%]. The digital control presented a high power factor (0.990), high efficiency (92.46%), and low harmonic distortion (THDI=5.09% and THDV=2.84%).     

Proposal of a Soft-Switching Single-Phase Three-Level Rectifier

This paper is concerned with the study of a single-phase boost-type three-level rectifier. The converter is supposed to present high input power factor, low current harmonics, low total harmonic distortion, and simple control scheme. In order to minimize switching losses, a passive nondissipative snubber is associated with the aforementioned converter. The theoretical analysis, design procedure, and analytical results regarding a 1.2-kW prototype are presented to validate the proposal.     

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     

A bidirectional AC-DC power converter with power factor correction

This paper presents new operation and performance of a thyristor-based AC-DC current-controlled boost-type converter that allows bidirectional power handling capability and provides input power factor correction and a near-sinusoidal input current waveform. The new converter can reduce harmonic pollution and disturbance on the supply mains. The feature of bidirectional power flow allows the stored energy in loads, such as motors, to regenerate back to the supply source, leading to an increase in overall energy efficiency and possibly a reduction in the size of the DC link capacitor. The operation is confirmed with the successful implementation of an experimental prototype     

Input power factor control of AC-DC series resonant DC linkconverter using PID operation

This paper proposes a method of power factor control for the three-phase input current of AC-DC series resonant DC link power converter systems. The proposed system has fast response, using high frequency resonance, soft switching (zero current switching), and natural commutation of thyristor switches. By implementing the PID operation strategy for switching control, the system performs reliable operation in the input power factor control, and the elimination of higher harmonic components can be achieved dramatically. The numerical and experimental results are presented in this paper     

Magnetic-coupled high power factor converter with low line currentharmonic distortions for power factor correction and fast outputresponse

A new magnetic-coupled high power factor converter (MCHPFC) with a single switch/single stage is proposed. The proposed converter gives good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows that the IEC555-2 requirements are met satisfactorily with nearly unity power factor. A proposed MCHPFC is particularly suited for low-power-level power supply applications     

Analysis and design of a practical discontinuous-conduction-modeBIFRED converter

Impending international standards on harmonic current levels drawn by single-phase mains-operated equipment have created a need for low-cost off-line power-factor-corrected switched-mode power supply topologies in the power range up to a few hundred watts. The boost integrated/flyback rectifier/energy storage/DC-DC converter (BIFRED) is one such topology which shows promise in this regard. In particular, the discontinuous-conduction-mode (DCM) BIFRED avoids the light-load high-voltage stress problem associated with the continuous-conduction-mode design, while still achieving the combined advantages of a low-cost single-stage topology with high displacement factor and low total harmonic distortion. In this paper, a practical DCM BIFRED converter with integrated low-loss snubber is investigated from both power and small-signal control perspectives. Design equations are given to ensure DCM operation under closed-loop output voltage control, in which switch duty cycle is varying. Experimental results on a prototype converter are also presented     

Step-Up/Step-Down DC–DC ZVS PWM Converter With Active Clamping

This paper presents a regenerative step-up/step-down DC-DC zero-voltage-switching pulsewidth-modulation converter with active clamping. The switch losses are reduced due to the implementation of a simple active snubber circuit that provides soft commutation in all the switches of the converter. The theoretical analysis, basic equations, design methodology, and experimental results are shown in this paper. A control methodology to assure the output voltage regulation is also proposed. The main advantages of the proposed power converter are the small number of components, simplicity of the controller, robustness, small weight and size, and high efficiency.     

A unity power factor resonant AC/DC converter for high-frequencyspace power distribution system

This paper presents analysis and design of a resonant AC/DC converter topology, suitable for use in an advanced single-phase, sine-wave voltage, high-frequency power distribution system of the type that was proposed for a 20 kHz space station primary electrical power distribution system. The converter comprises a transformer, a double-tuned resonant network comprising of series- and parallel-tuned branches, a controlled rectifier, and an output filter. Symmetrical phase control technique that generates fundamental AC current in phase with the input voltage is employed. Steady-state analysis of the converter in continuous current mode of operation is provided, and the performance characteristics presented. The proposed converter has close-to-unity rated power factor (greater than 0.98), a wide range of output voltage control (0%-100%), low total harmonic distortion in input current (less than 8%), and high conversion efficiency. Finally, selected experimental results of a bread-board converter are presented     

Analysis and optimization of a nondissipative LC turn-offsnubber

A nondissipative LC turn-off snubber is used to reduce the voltage stress on a switching transistor, which is caused by the energy stored in the transformer leakage inductance. A detailed analysis of the fundamental characteristics of a buck-boost converter with an LC snubber is given, clarifying the effect of the snubber capacitance. In particular, it is found that the transformer current increases with the snubber capacitance, the transistor surge voltage and power loss are evaluated, and the optimum value of the snubber capacitance is derived. The most effective value of the snubber inductance is also discussed     

A digitally controlled switch mode power supply based on matrix converter

High power telecommunication power supply systems consist of a three-phase switch mode rectifier followed by a dc/dc converter to supply loads at -48 V dc. These rectifiers draw significant harmonic currents from the utility, resulting in poor input power factor with high total harmonic distortion (THD). In this paper, a digitally controlled three-phase switch mode power supply based on a matrix converter is proposed for telecommunication applications. In the proposed approach, the matrix converter directly converts the low frequency (50/60Hz, three-phase) input to a high frequency (10/20kHz, one-phase) ac output without a dc-link. The output of the matrix converter is then processed via a high frequency isolation transformer to produce -48V dc. Digital control of the system ensures that the output voltage is regulated and the input currents are of high quality under varying load conditions. Due to the absence of dc-link electrolytic capacitors, power density of the proposed rectifier is expected to be higher. Analysis, design example and experimental results are presented from a three-phase 208-V, 1.5-kW laboratory prototype converter.     

A single-switch AC-DC converter with power factor correction

A new single-stage, single-switch power factor correction converter with output electrical isolation is proposed in this paper. The topology of this converter is derived by combining a boost circuit and a forward circuit in one power stage. To improve the performance of the AC-DC converter (i.e., good power factor correction, low total harmonic distortion (THD) and low DC bus voltage), two bulk storage capacitors are adopted. Its excellent line regulation capability makes the converter suitable for universal input application. Due to its simplified power stage and control circuit, this converter presents a better efficiency, lower cost and higher reliability. Detailed steady state analysis and design procedure are presented. To verify the performance of the proposed converter, a design example along with P-simulation program with integrated circuit emphasis (PSPICE) simulation and experimental implementation are given. The measured power factor and efficiency are 99% and 87% at low line (i.e. 110 VAC) operation, and 95% and 81% at high line (i.e. 220 VAC) operation, respectively     

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.      

A high-performance ZVS full-bridge DC-DC 0-50-V/0-10-A power supplywith phase-shift control

This paper presents a high-performance DC-DC switching mode power supply designed to deliver a regulated 0-50 V/0-10 A output. The proposed power supply is based on a modified version of the zero-voltage switching (ZVS) full-bridge (FB) phase-shift DC-DC converter, which incorporates commutation auxiliary inductors to provide ZVS for the entire load range as well as a commutation aid circuit to clamp the output diode voltage. The control strategy is based on two control loops operating in cascade mode. The inner loop maintains a regulated output current, whereas the external voltage loop regulates the output voltage, independently of load and input-voltage changes. In order to obtain a high-reliability converter, the control circuit has been implemented using just two integrated circuits (ICs). The phase-shift regulator UC3875 IC generates the gate drive signal to the MOSFET's. The control loop regulators are implemented using the TL074 IC. A theoretical analysis was conducted, and experimental results were obtained for a 0-50 V/0-10 A power supply operating at 100 kHz     

A Nonisolated Single-Phase UPS Topology With 110-V/220-V Input–Output Voltage Ratings

A circuit configuration of a single-phase nonisolated online uninterruptible power supply (UPS) with 110-V/220-V input–output voltage ratings is proposed, allowing the bypass operation without a transformer even if the input voltage is different from the output voltage. The converter consists of an ac–dc/dc–dc three-level boost converter combined with a double half-bridge inverter. In this type of configuration size, cost and efficiency are improved due to the reduced number of switches and batteries, and also, no low-frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate at high frequency by using a passive nondissipative snubber circuit in the boost converter and insulated-gate bipolar-transistor switches in the double half-bridge inverter, with low conduction losses, low tail current, and low switching losses. Principle of operation and experimental results for a 2.6-kVA prototype are presented to demonstrate the UPS performance.      

Low-harmonic GTO converter for fundamental power factorcompensation

A low-harmonic GTO (gate turn-off) thyristor AC-to-DC converter with line current lead-lag phase shift control ability is proposed and analyzed. The converter can be used either as a low-harmonic GTO-controlled rectifier or a fundamental input power factor compensator in a power supply system. The effect of PWM (pulse width modulation) current phase number on the harmonic contents and converter output voltage control range is investigated. Lower order input current harmonics are eliminated over a wide range, using a specially designed PWM current pattern. The effect of the PWM current pulse number on the power factor compensation characteristic is investigated     

New conceptual three-phase current-fed soft switching pulse width modulation converter with switched capacitor type resonant dc link

This paper presents a novel prototype of three-phase current-fed PWM converter with a switched capacitor type resonant dc link snubber circuit, which can basically operate under a principle of zero current soft switching commutation. The optimum PWM pattern-based control scheme proposed by the authors is effectively applied for this active converter. In this paper, the steady-state operating principle of a new converter circuit treated here is described. The practical design procedure of this converter is discussed from a theoretical point of view. The feasible experiment to confirm zero current soft switching commutation of this converter is concretely implemented and evaluated herein.     

An improved ZCT-PWM DC-DC converter for high-power and frequency applications

In this paper, an improved active resonant snubber cell that overcomes most of the drawbacks of the normal zero-current transition (ZCT) pulsewidth-modulation (PWM) dc-dc converter is proposed. This snubber cell is especially suitable for an insulated gate bipolar transistor (IGBT) PWM converter at high power and frequency levels. The converter with the proposed snubber cell can operate successfully with soft switching under light-load conditions and at considerably high frequencies. The operation principles, a detailed steady-state analysis, and a snubber design procedure of a ZCT-PWM buck converter implemented with the proposed snubber cell are presented. Theoretical analysis is verified with a prototype of a 5-kW and 50-kHz IGBT-PWM buck converter. Additionally, at 90% output power, the overall efficiency of the proposed soft switching converter increases to about 98% from the value of 91% in the hard-switching case.     

Evaluating Voltage Notch Problems Arising from AC/DC Converter Operation

This paper analyzes the voltage notches in ac/dc converters and the problems that they create. Voltage notch disturbs the voltage's waveform and excites the natural frequencies of the system. In some systems, these excisions create considerable high-frequency oscillations in the voltages of the converter and the adjacent buses; this can damage capacitor banks, create parallel resonance, and generate radio disturbances. This paper analyzes the effect of snubber circuits on the voltage oscillations that arise from commutation. It also presents the theoretical foundation and analytical derivation that are used to calculate notch depth and the frequency of oscillations. To achieve accurate and applicable results, various loads of the converter, the dc current ripple, and the characteristic impedance of the system are considered. Several experimental results are shown in order to illustrate the effects of changes in the system and converter parameters on the voltage waveform of the converter. Computer simulations and experimental results indicate the accuracy of the theoretical relations. The proposed equations make it possible to effectively study the harmonic and power quality in networks that include high-power converters.