L.C. de Freitas

A high-power high-frequency ZCS-ZVS-PWM buck converter using a feedback resonant circuit

A buck DC-DC power converter using a novel lossless commutation cell for high switching frequency and high power operation is presented. The proposed cell consists of a main switch and an auxiliary switch, with ZVS (zero voltage switched) and ZCS (zero current switched) switching characteristics, respectively. The converter control using this cell is realized by the PWM technique, with constant switching frequency operation. The complete operation principles, theoretical analysis, relevant equations, state space phase, simulation, and experimental results for the buck converter are presented. >

A novel family of DC-DC PWM converters using the self-resonance principle

Obtaining soft-switching operation for PWM power converters, except for a few cases, has required either high switch voltage stresses or high switch current stresses, or both. This paper presents a new class of commutation self-resonant PWM power convertor that overcomes this great disadvantage as well as being able to operate without switching losses in high switching frequencies for a wide line and load range. The circuit diagram and the phase-plane of each power converter of a family of such converters are also presented. In order to emphasize the principal characteristics of these new converters, a study, including experimental results, is carried out in detail for the buck and zeta converters.<<ETX>>

A new ZCS-ZVS-PWM boost converter with unity power factor operation

This paper introduces the self-resonance concept as a new way to obtain power converters without switching losses. Using this new approach, a self-resonant ZCS-ZVS-PWM boost power converter is presented. It is suitable for high switching frequency, high power operation and wide range of power. The converter control is done by using PWM technique, with constant frequency operation. The complete theoretical analysis and simulation results for the self-resonant PWM boost power converter, operating without power factor correction, are presented. Moreover, experimental results for this new boost converter, operating with unity power factor, support the validity of this new approach.<<ETX>>

A novel ZCS-ZVS-PWM DC-DC buck converter for high power and high switching frequency: analysis, simulation and experimental results

A DC-to-DC power converter using a zero current switching zero voltage switching PWM (ZCS-ZVS-PWM) cell for high switching frequency and high power operation is presented. The proposed cell consists of only one main switch, plus an auxilliary switch, with ZVS and ZCS switching characteristics, respectively. These switches, associated with a resonant inductor and capacitor, yield zero voltage and zero current switching, providing highly efficient operating conditions for a wide range of power at high switching frequency. Converter control is accomplished by using the PWM technique, with constant frequency operation. A complete analysis of the operating principles, including output characteristics, relevant equations, state space phase, simulation, and experimental results for the buck power converter, is presented.<<ETX>>

An optimum ZVS-PWM DC-to-DC converter family: analysis, simulation and experimental results

The authors consider a family of DC-to-DC power converters using the lossless commutation pulse-width-modulation (PWM) source feeding resonant disconnecting circuit cell with resonant cycle interruption (LC-PWM-SF-RDC) to overcome the problems present in quasi-resonant converters (QRCs) and QRCs-PWM. The most important property of this family of devices is the ability to regulate output power and voltage by PWM, with constant operating frequency, without load limitation, and without sacrificing the lossless commutation. The authors present the operating principle and design-oriented analysis, output characteristics, relevant equations, and simulation results. These procedures are validated by a prototype laboratory implementation.<<ETX>>

Programmable PFC based hybrid multipulse power rectifier for ultra clean power application

A novel hybrid three-phase rectifier is proposed. It is capable to achieve high input power factor (PF) and low total harmonic input currents distortion (THD/sub I/). The proposed hybrid high power rectifier is composed by a standard three-phase six-pulse diode rectifier (Graetz bridge) with a parallel connection of single-phase Sepic rectifiers in each three-phase rectifier leg. Such topology results in a structure capable of programming the input current waveform and providing conditions for obtaining high input power factor and low harmonic current distortion. In order to validate the proposed hybrid rectifier, this work describes its principles, with detailed operation, simulation, experimental results, and discussions on power rating of the required Sepic converters as related to the desired total harmonic current distortion. It is demonstrated that only a fraction of the output power is processed through the Sepic converters, making the proposed solution economically viable for very high power installations, with fast investment payback. Moreover, retrofitting to existing installations is also feasible since the parallel path can be easily controlled by integration with the existing dc-link. A prototype has been implemented in the laboratory and it was fully demonstrated to both operate with excellent performance and be feasibly implemented in higher power applications.

A buck quadratic PWM soft-switching converter using a single active switch

High-switching frequency associated with soft commutation techniques is a trend in switching converters. Following this trend, a buck pulsewidth modulation (PWM) converter is presented. The DC voltage conversion ratio of this converter has a quadratic dependence on duty cycle, providing a large stepdown. This new buck quadratic PWM soft-single-switched converter, having only a single active switch, provides a high efficient operating condition for a wide load range at high-switching frequency. In order to illustrate the operating principle of this new converter, a detailed study including theoretical analysis, relevant equations and simulation, and experimental results is carried out.

A boost converter associated with a new nondissipative snubber

This paper presents a boost converter with a nondissipative snubber which provides a soft switching converter operation. This approach allows the main switch to work in a ZVS way and the auxiliary switch to work in a ZCS way. The nondissipative snubber is composed by two capacitors (resonant capacitors), one inductor (resonant inductor), one switch (auxiliary switch) and two diodes, one in series with the main switch and the other in series with the auxiliary switch. The complete operating principle, relevant equations, simulation results and experimental results are presented.

An optimal lossless commutation quadratic PWM Boost converter

This paper presents a PWM boost power converter, where the DC voltage conversion ratio has a quadratic dependence on the duty cycle, providing a large voltage step up (from 24 V to 160 V). By introducing two resonant networks, soft switching is achieved, providing highly efficient operating conditions for a wide load range at high switching frequencies.

A quadratic buck converter with lossless commutation

High switching frequency associated to soft commutation techniques is a trend in switching power converters. Following this trend, a buck PWM power converter is presented, where the DC voltage conversion ratio has a quadratic dependence on duty-cycle, providing a large step-down. By introducing two resonant networks, soft switching is attained, providing high efficient operating condition for wide load range at high switching frequency. Contrarily to most of the power converters that apply soft switching techniques, the switches are not subjected to high switch voltage or current stresses and, consequently, present low conduction losses. This paper describes the principle of operation, theoretical analysis, relevant equations and simulation and experimental results for this type of power convertor.