L.C. Gomes de Freitas

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 novel programmable PFC based hybrid rectifier for ultra clean power application

A novel hybrid high power rectifier capable to achieve unity power factor is proposed in this paper. Single-phase SEPIC rectifiers are associated in parallel with each leg of three-phase 6-pulse diode rectifier resulting in a programmable input current waveform structure. In this paper it is described the principles of operation of the proposed converter with detailed simulation and experimental results. For a total harmonic distortion of the input line current (THD/sub I/) less than 2% the rated power of the SEPIC rectifiers is 33%. Therefore, power rating of the SEPIC parallel converters is a fraction of the output power, on the range of 20% to 33% of the nominal output power, making the proposed solution economically viable for high power installations, with fast pay back of the investment. Moreover, retrofits to existing installations are also possible with this proposed topology, since the parallel path can be easily controlled by integration with the already existing DC-link. Experimental results are presented for a 3 kW implemented prototype, in order to verify the developed analysis.

A single-stage PFC converter applied as an electronic ballast for fluorescent lamps

A new power factor correction converter in single stage is presented in this paper. The proposed topology was develop from the integration of the self-oscillating boost EIE converter operating in critical conduction mode (CCM) with the buck-boost power factor correction stage. This new power factor (PFC) in single stage has been applied as an electronic ballast for fluorescent lamps and has been shown itself as a great choice for specialized industry mainly because of its low cost and facility of implementation. Simulation and experimental results of an prototype built at laboratory for a 40 W fluorescent lamp, with a low THD (13%), power factor equal to 99.16%, and crest factor equal to 1.4 are presented.

A new proposal of switched power oscillator with soft-commutation applied as a HPF electronic ballast

A new switched power oscillator with reduced conduction losses, zero voltage and zero current turning on, and zero voltage turning off, is presented in this paper. The proposed topology consists on a buck plus boost converter operating in continuous conduction mode (CCM) associated to a self-oscillating LC series resonant circuit. This new power oscillator can be applied as an electronic ballast for fluorescent lamps as well as self-oscillating auxiliary medium open loop power supply. Circuit description and experimental results of the proposed HPF electronic ballast with low THD/sub I/ (7.3%), high PP (99.73%), and crest factor equal to 1.4 are presented. A high power factor electronic ballast prototype switching at 40 kHz for a 40 W fluorescent lamp has been built and analyzed experimentally and by simulation.

A new proposal of switched power oscillator applied as a self-oscillating auxiliary medium open loop power supply

A new proposal of switched power oscillator with reduced conduction losses, zero voltage and zero current turning on, and zero voltage turning off, is presented in this paper. The proposed topology consists of a boost EIE converter operating in continuous conduction mode (CCM) associated to a self-oscillating LC series resonant circuit. This new self-oscillating power oscillator can be applied as an inverter stage of electronic ballast for fluorescent lamps as well as medium open loop power supply. Circuit description and a simplified design guide line are presented. A power oscillator prototype applied as a self-oscillating auxiliary medium open loop power supply with an output power of 15.7 W has been built and analyzed by simulation and experimentally.

Multipulse power rectifier without using multiphase transformers

In this paper it is proposed a novel hybrid three-phase rectifier capable to achieve high input power factor (PF), and low total harmonic distortion in the input currents (THD/sub 1/). The proposed hybrid high power rectifier is composed by a standard three-phase 6-pulse diode rectifier (Graetz bridge) with a parallel connection of single-phase boost 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 paper describes its principles of operation, with detailed experimental results and discussions on power rating of the required boost 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 boost converters, making the proposed solution economically viable for very high power installations, with fast pay back of the investment. 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 rated at 6 kW has been implemented in laboratory and fully demonstrated its operation, performance and feasibility to high power applications.

Class-D amplifier for automotive and public audition applications

This paper proposal presents a new high power Class-D audio amplifier for woofer applications. A regulated DC voltage supply is not needed as well as a low pass output filter overcoming the disadvantages of ordinary audio amplifiers structures. A 1 kW laboratory prototype was implemented and it was found that a 94% efficiency and 1% of THD could be achieved. A detailed design guide line, principle of operation analysis, control strategy, is also included in this paper proposal.

A new proposal of soft-commutated power oscillator that can be applied as an electronic ballast for fluorescent lamps

A new switched power oscillator with reduced conduction losses, zero voltage and zero current turning on, and zero voltage turning off is presented in this paper. The proposed topology consists on a half-bridge converter associated to a self-oscillating LC series resonant circuit. This new power oscillator can be applied as an electronic ballast for fluorescent lamps as well as an auxiliary medium open loop power supply. Circuit description, a simplified design guide line, mathematical analysis and simulation results are presented in this paper. Experimental results from a 100 Watts, 150 Volts input voltage laboratory prototype switching at 13.5 kHz are included.