M. F. da Silva

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.

Analysis and Design of a Single-Stage High-Power-Factor Dimmable Electronic Ballast for Electrodeless Fluorescent Lamp

A methodological study of an electronic ballast for electrodeless fluorescent lamps (EFLs) including design and development issues is presented in this paper. The ballast is intended to feed a 100-W EFL at 250 kHz with dimming feature. The proposed topology is composed of a single-ended primary-inductance converter, used as power-factor (PF)-correction stage, integrated with a resonant half-bridge inverter, used as lamp-power control stage. The integration of both stages is proposed in this paper, in order to reduce the number of active switches, as well as to simplify the required driving and control circuitry for this application. Experimental results demonstrate the feasibility of the proposed solution that achieves 54% lamp-power dimming (46 W). The implemented topology attained very high PF (0.989) and low line-current total harmonic distortion (14.929%), without using electromagnetic interference filter, while the measured efficiency was 87% at nominal lamp power.

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.

Feedforward Regulation Method for Self-Oscillating Electronic Ballast for Fluorescent Lamps

This paper presents a feedforward fluorescent lamp power regulation method for self-oscillating electronic ballast for different line voltages. The proposed method consists in maintaining the lamp power regulated through the feedforward switching frequency variation using the output resonant filter feature and self-oscillating gate driver circuit. Experimental results demonstrate the feasibility of the proposed solution that allows regulating the lamp power in a wide input voltage range (110 to 220 Vrms ) with an error of up to 12%.

A Comparative Performance Investigation of Single-Stage Dimmable Electronic Ballasts for Electrodeless Fluorescent Lamp Applications

This paper presents a comparative investigation, design and development issues about six different single-stage topologies, applied as electronic ballasts, for electrodeless fluorescent lamps. The ballast is intended to feed a 100 W lamp at 250 kHz, with dimming feature. The proposed topologies use different converters for the power factor correction (PFC) stage: Buck-Boost, SEPIC, Zeta, Cúk, Flyback, and Boost. All of them operate in discontinuous conduction mode. A resonant half-bridge inverter is used as lamp power control (PC) stage. The integration of both stages (PFC and PC) is proposed in this paper. In this way, it is possible to reduce the number of active switches, as well as simplify the required driving and control circuitry. Experimental results demonstrate the feasibility of the proposed dimming technique that achieved around 56% lamp power dimming, from 100 W down to 44 W. The implemented topologies attained high average power factor (>0.98), and low line current average total harmonic distortion (<;15.3%). A comparison among all the proposed topologies in terms of power factor, harmonic distortion, efficiency and number of components is presented. Finally, a comparison between an integrated and a nonintegrated SEPIC half-bridge converter is also performed.

Single-stage SEPIC-Buck converter for LED lighting with reduced storage capacitor

This paper presents an analysis and design of a Light Emitting Diode (LED) driver aiming to eliminate/substitute the electrolytic capacitors. Considering the low lifetime of electrolytic capacitors compared to LEDs, this topology aims for reducing the storage capacitance and replaces it by a film capacitor, increasing the system lifetime. This reduction is based on designing of the control dynamic with a compromise between the input current distortion and the output current ripple. The power factor correction (PFC) stage is based on a Single Ended Primary Inductance Converter (SEPIC) because of its intrinsic low input current distortion characteristic making it possible to eliminate the electromagnetic interference (EMI) filter. The power control (PC) stage is performed by a Buck converter using its output current source behavior, suitable for LED application. A 100 W LED driver prototype is implemented resulting in a 6.9% total harmonic distortion (THD) and 30% current ripple on the LED.

Design procedure for a compact lamp using high-intensity LEDs

This paper proposes a circuit to a compact lamp based on light emitting diodes (LEDs). It aims energy savings, high luminous efficiency and high useful life with the replacement of incandescent or compact fluorescent lamps by LEDs without any change in the electrical system installation. In order to supply the LEDs by mains with a constant current, the Buck converter has been used because it provides an output voltage lower than the input one. The circuit has been designed to supply 36 to 52 high-brightness LEDs connected in series, resulting in a converter output voltage between 90 V and 187 V. The load can also be composed of power LEDs. The main disadvantage of series connection is that the damage of one LED can results in an open-circuit, disconnecting the entire group. The proposed idea to solve this problem is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns, the Diac in parallel with this group keeps the current path, guaranteeing the operation of the others groups. To verify the proposed idea, prototypes of the lamp have been implemented and tested.

Single-stage high-power-factor dimmable lighting system for electrodeless fluorescent lamp

The use of the electrodeless fluorescent lamps has been increasing, because of their features such as lifetime and lumen efficiency, when compared to conventional fluorescent and high pressure sodium lamps. The single-stage high-power-factor electronic ballast for electrodeless fluorescent lamp with dimming feature is presented on this paper. It is obtained by integrating a SEPIC converter with a Half-Bridge asymmetric LCC resonant inverter, which can effectively regulate the lamp power. Experimental results are shown, in order to validate the proposed idea. The implemented topology presented a power factor of about 0.995, a total current harmonic distortion of 9.61% and an efficiency of 86%.

Comparison of self-oscillating electronic ballasts dimming methods with power factor correction for fluorescent lamps

This paper presents a comparative analysis of dimmable self-oscillating electronic ballast for fluorescent lamps. A review of general dimming methods presented in the literature is performed. A general analysis of each dimming method is made, and the operation with power factor correction was considered in order to evaluate the characteristic of each topology and to define other circuits more adequate for this purpose. A comparison based on literature review and experimental results of the implemented prototypes is carried out in order to establish the main conclusion from this analysis.

High power factor dimmable lighting system for electrodeless fluorescent lamp

The use of the fluorescent lamps without electrodes (electrodeless) has been increasing, because of their features such as lifetime and lumen efficiency, when compared to conventional fluorescent and high pressure sodium (HPS) lamps. This paper presents a luminous flux variation strategy using a Single Ended Primary Inductance Converter (SEPIC), which also provides high power factor correction, to feed electrodeless fluorescent lamps. Since the load is variable a digital compensation is used to meet the control of the specified output voltage in the project, once the dimming characteristic is achieved by varying the SEPIC output voltage. A microcontroller is used in order to allow a suitable control for the converter since it presents features that make possible to obtain dimming capability. The lumens information can be done through wireless system.