R.N. do Prado

Resonant filter applications in electronic ballast

In this paper an analysis is presented of the resonant filter used in an electronic ballast through the phase angle from the input resonant filter current to the input resonant filter voltage. The proposed analysis allows evaluation of the resonant filter characteristics. The main characteristics that are analyzed are: lamp starting, soft commutation, DC current in the lamp, resonant filter influence in the converters and lamp pre-heating. This work allows a choice of the best filter to employ in an electronic ballast for fluorescent lamps.

Fluorescent lamp model based on the equivalent resistance variation

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the equivalent resistance variation as function of power, constructed by experimental results for several power levels. Simulations and experimental results are presented to verify the feasibility of the model and, moreover, an electronic ballast example using the proposed model is presented to further demonstrate its applications.

Reducing storage capacitance in off-line LED power supplies by using integrated converters

In this paper a new technique to reduce the LED current ripple and storage capacitance in high power factor (PF) off-line LED power supplies is investigated. The proposed methodology is based on the use of integrated power converters (IPC) to implement the power supply. Thus, the first stage operates in discontinuous conduction mode (DCM) to provide high PF. The second stage can be operated in either continuous conduction mode (CCM) or DCM. A family of IPCs is proposed to be used as LED lamp power supplies. A generalized analysis is carried out in order to obtain the important design equations and conditions. Finally, an example of an IPC is given, along with some experimental results to demonstrate the effectiveness of the proposed technique.

Self-oscillating electronic ballast design based on the point of view of control system

This paper presents a design methodology, analysis, and practical considerations of self-oscillating drive circuit for electronic ballasts by considering the self-oscillating electronic ballast as a relay control system. The first section of the paper analyzes the design of resonant elements, the nonlinearity present in the circuit and consideration to apply the methodology proposed. The second section of the paper shows the design of self-oscillating electronic ballast using control tools such as: describing function, extended Nyquist criterion and block diagrams that allows an expression for designing the self-oscillating electronic ballast to be found.

A semiconductor lighting system controlled through a LIN network to automotive application

This paper proposes an intelligent lighting system for bus interior environment using LEDs (light emitting diodes) controlled through an automotive communication network. The system consists on a master central control and slaves lighting modules, using a LIN (local interconnect network) network to perform communication. This network is a low cost alternative to the proposed system requirements, due to its low bit rate and physical needs. The slaves are independent lighting modules that supply a group of LEDs and measure the environment lighting level. The master sets LEDs module parameters (slaves), such as the state (on/off), and desired lighting level The master makes the user interface, sets the lighting parameters, as timer and lighting level and, more over, it establishes communication with other bus systems through a CAN (controller area network) gateway. This paper presents a complete logical description, including block and state diagrams, a physical description and some relevant experimental results.

Simple valley-fill self-oscillating electronic ballast with low crest factor using pulse-frequency modulation

This paper presents an alternative to achieve fluorescent lamp current low crest factor, using the valley-fill filter as a passive power-factor-correction method. Pulse frequency modulation is used to reduce lamp current high crest factor. Self-oscillating electronic ballast is employed in order to avoid complex circuitry. The partial smoothing valley-fill DC-link bus voltage is used to control the switching frequency. Crest factor correction is achieved through a low power bipolar transistor, which connects a low power passive circuit parallel within the self-oscillating gate-driver circuit. The switching frequency changes in order to keep the lamp current crest factor lower than 1.7 and a modified valley-fill filter is used to meet IEC61000-3-2 requirements. Simulations and experimental results are presented to demonstrate the simplicity, and feasibility of the proposed system.

An analysis about valley fill filters applied to electronic ballasts

This paper presents a detailed analysis about valley fill filters applied to power factor (PF) correction of electronic ballasts. Comparative results about input current THD are done in this study, verifying if it meets the IEC 61000-3-2 standard requirements, that determines the maximum amplitude of each harmonic component from 2/sup nd/ up to 39/sup th/. Power factor (PF), total harmonic distortion (THD), crest factor (CF), auxiliary circuit losses, and operation principles are also presented.

A design method for electronic ballast for fluorescent lamps

This paper presents a new design methodology, analysis, and practical considerations about series parallel resonant filter, LCC, for electronic ballasts employing the self-oscillating driver circuit. Designs equations and graphic methods are presented, obtained by analysis of Fourier series, Tsypkins Locus and stability tests. The lamp high frequency supply is given by the half-bridge converter, and the verification of this approach is guaranteed by simulation and experimental results.

Low cost high-power-factor electronic ballast for compact fluorescent lamps

This paper presents the analysis, design and practical considerations of several low cost high-power-factor ballast for compact fluorescent lamps. The proposed topologies are a combination of a boost converter and a half-bridge parallel resonant converter. The high frequency supply to the lamp is made by a self oscillating half-bridge converter, using integrated circuits IR2151 and IR51HD420. The high-power-factor is guaranteed by using a boost converter operating in discontinuous conduction mode. These topologies have been developed for 20 W compact fluorescent lamps for 110 V, 60 Hz utility line.

Compact Lamp Using High-Brightness LEDs

This paper proposes a circuit for a compact lamp based on high-brightness LEDs. It aims energy savings, high luminous efficacy and high useful life when substituting incandescent or compact fluorescent bulbs for LEDs without any change in the electric system installation. In order to supply the LEDs by mains with a forward current, the Buck converter has been chosen. The load can be composed by 36 to 52 LEDs of 5 mm connected in series, resulting in a converter output voltage between 90 V and 187 V. The advantage of series connection is that all LEDs produce the same brightness since its luminous intensity is proportional to the supplied current. The disadvantage is that the damage of one LED could results in an open-circuit, turning off the entire group. To fix this problem, the proposed idea on this work is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns the breakdown voltage is reached, and the Diac in parallel with this group become a short- circuit guaranteeing the operating of the others groups. To verify the proposed idea, the compact lamp has been implemented and tested.