José Luiz de Freitas Vieira

High power factor electronic ballast based on a single power processing stage

A new low cost high power factor electronic ballast is introduced in this paper. The proposed topology is based on a single power processing stage to provide high frequency voltage to fluorescent lamps and high power factor to the utility line. The power processing stage is formed by a half-bridge converter operating above the resonant frequency to provide zero voltage switching. The self-oscillating technique is employed, which increases the converter reliability with great simplicity and low cost. High power factor is achieved by using a nonconventional AC/DC boost converter operating in discontinuous current mode. Theoretical analysis and experimental results have been obtained for two 40 W fluorescent lamps operating at 50 kHz switching frequency and 127 V line voltage.<<ETX>>

Improving the operation of ZVT DC-DC converters

This paper presents an improved ZVT DC-DC boost power converter using a regenerative snubber. The proposed snubber uses a magnetically coupled cell to reduce the turn-off switching loss of the auxiliary switch. The method has been employed to build a 500 W/100 kHz prototype. The experimental results show the ZVT DC-DC boost converter waveforms with and without the regenerative snubber. A high efficiency is achieved using the proposed improvement.

Single stage electronic ballast for HID lamps

This paper presents a single power processing stage electronic ballast for HID lamps. A DC-DC buck converter that controls the current and the power of the lamp, a power factor pre-regulator based on discontinuous conduction mode boost converter and the inverter are combined in a dual fed full bridge BIBRED converter. It operates with a low frequency current driving the lamp. All signals of the power stages are provided by a dedicated microcontroller. A 70 W prototype without acoustic resonance and no stroboscope effect was implemented.

A high performance ZVS full-bridge DC-DC 0-50 V/0-10 A power supply with 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 full-bridge phase-shift DC-DC converter, which incorporates commutation auxiliary inductors to provide zero voltage switching for the entire full 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 the regulated output current, whereas the external voltage loop keeps the regulated output voltage, independently of load changes and input voltage variations. To obtain a high reliability converter, the control circuit has been implemented using just two ICs. The phase-shift regulator UC3875 IC generates the gate drive signal to the MOSFETs. The control loop regulators are implemented using the TL074 IC. Theoretical analysis and experimental results have been obtained for a 0-50 V/0-10 A power supply operating at 100 kHz.

Microcontrolled electronic gear for low wattage metal halide (MH) and high-pressure sodium (HPS) lamps

This paper presents an electronic control gear for HID lamps that operates with a low frequency current inverter to drive the lamp, a DC-DC buck converter to control the current and the power of the lamp and a power factor pre-regulator based on discontinuous conduction mode boost converter. All signals of the power stages are provided by a dedicated microcontroller. An overview of the lamp operation phases and the strategies to avoid acoustic resonance are mentioned. A 70 W prototype without acoustic resonance and stroboscope effect was implemented. The approach can be easily extended for other rated power.

Single stage self-oscillating HPF electronic ballast

This paper presents a single-stage self-oscillating high-power-factor electronic ballast more suitable for both low power levels (because it operates in discontinuous conduction mode) and low ac mains applications (since it employs an input-doubler rectifier). The electronic ballast is based on a high-frequency dither signal, which shapes the input current in a sinusoidal waveform. In order to reduce the electronic ballast components the self-oscillation technique has been employed. An electronic ballast prototype operating at 25 kHz has been implemented to drive two 40-W straight-type fluorescent lamps from a 127-V utility line. High power factor is achieved even though the electronic ballast drives just one fluorescent lamp. The experimental results demonstrated the electronic ballast operation.

A magnetically coupled regenerative turn-on and turn-off snubber configuration

This paper presents a magnetically coupled regenerative turn-on and turn-off snubber configuration applied to a boost converter, which operates in continuous conduction mode (CCM). In addition to reducing the stresses in the switch, providing soft transitions in its turn-off voltage and turn-on current, it transfers the energy stored in the snubber capacitor to the load. This is achieved by using a coupled inductor mounted on the main inductor of the converter, which resets the capacitor voltage at each switching period. Design equations, as well as experimental results are presented, showing the high performance of the boost converter using the proposed snubber.

An isolated DC-DC boost converter using two cascade control loops

This paper presents an isolated DC-DC power converter designed to operate as the primary stage of an on-board DC-AC power supply for diesel-electric engines. The DC-AC power supply must provide a sinusoidal waveform of 127 V RMS from the 72 V DC bus of the engine. The DC-DC push-pull current-fed power converter has been used to obtain an isolated 200 V DC output voltage from the available 72 V DC bus engine. This power converter operates as a boost converter with constant frequency and duty cycle greater than 50%. Two control loops operating in cascade mode were used. A fast inner current loop regulates the boost inductor current, whereas an external control loop keeps a constant output voltage. Experimental results have been obtained for a 300 W laboratory prototype operating at 50 kHz. The power converter efficiency was 93% at full load, and the output voltage regulation was less than 1% for 10% to 100% load changes.

Power converter topologies for a high performance transformer rectifier unit in aircraft applications

This paper presents some power converter architectures and circuit topologies, which can be used to achieve the requirements of the high performance transformer rectifier unit in aircraft applications, mainly as: high power factor with low THD, high efficiency and high power density. The voltage and the power levels demanded for this application are: three-phase line-to-neutral input voltage of 115 or 115VAC rms (360-800Hz), output voltage of 28VDC or 270VDC (new grid value) and the output power up to tens of kilowatts.

A DCM three-phase SEPIC converter for low-power PMSG

A new three-phase controlled converter for low-power PMSG is presented in this digest. The converter is a SEPIC one, operating at DCM. The topology incorporates the PMSG inductance as its input inductor, and the generator currents are almost harmonics-free. Design equations are also presented, and results from simulations for both high and low wind speed show that this topology has a strong potential in the proposed application.