T.-H. Yu

Single-stage electronic ballast with dimming feature and unity power factor

Analysis, design, and practical consideration of a single-stage electronic ballast with dimming feature and unity power factor are presented in this paper. The proposed single-stage ballast is the combination of a boost converter and a half-bridge series-resonant parallel-loaded inverter. The boost semistage working in the discontinuous conduction mode functions as a power factor corrector and the inverter semistage operated above resonance are employed to ballast the lamp. Replacing the lamp with the plasma model, analysis of the ballast is fulfilled. The dimming feature is carried out by pulse-width modulation (PWM) and variable-frequency controls simultaneously. The proposed single-stage ballast is suitable for applications with moderate power level and low-line voltage while requiring a high-output voltage. It can save a controller, an active switch and its driver, reduce size, and possibly increase system reliability while requiring two additional diodes over a conventional two-stage system. A prototype was implemented to verify the theoretical discussion. The hardware measurements have shown that the desired performance can be achieved feasibly.

Unified approach to developing single-stage power converters

A unified approach to developing single-stage power converters which can fulfil multiple functions is presented. Four synchronous switches corresponding to the four common node types of two active switches are introduced. The approach is then to replace the active switches in multistage converters (in cascade or cascode connection) with one or several of the synchronous switches and their degenerated versions to form a single-stage converter. Illustrations of using these switches to develop single-stage converters are presented. These are started with the development of the well-known single-stage switch-mode converters (SMCs), buck-boost, Cuk, sepic, and Zeta (also named dual sepic), from the basic converters, buck and boost. Then, synthesis and applications of other single-stage converters are addressed. Due to increased component stresses, the developed single-stage converters are primarily suitable for applications with moderate power levels.

Off-line applications with single-stage converters

Offline applications with single-stage power converters (SSCs) are presented in this paper. The approach used in synthesizing the SSCs is first described, and their applications are then introduced. In addition, viable control strategies for the SSCs are addressed. The developed SSCs can fulfill multifunctions, such as input power factor correction, fast output regulation and lamp ballasting, and possess the merits of compact size, simple driver design and high reliability. Prototypes of SSCs, applied to an electronic dimming ballast and a DC regulator, are built which show high feasibility in such moderate power applications.

A PSpice model for fluorescent lamps operated at high frequencies

A PSpice circuit model simulating the electrical characteristics of the fluorescent lamp operated at high frequency is proposed. The model is constructed from a two-parameter equation which is derived based on a set of two measurements. This is a readily constructed and a computer simulator oriented model which is suitable for a preliminary design of electronic ballasts. Simulated and experimental results are used to verify the analytical discussions, and, moreover, an electronic ballast design example using the proposed model is presented to further demonstrate its applications.

Comparisons among self-excited parallel resonant, series resonant and current-fed push-pull electronic ballasts

Comparisons and examinations among self-excited parallel resonant, series resonant and current-fed push-pull electronic ballasts for fluorescent lamps in the aspects of soft starting, component stress, suitability of multi-lamp connection, variation of lumen under the operational condition of partial lamps extinguishment and/or removal, effect of lamp lifetime, inherence of short-/open-circuited protection, future expansion, double hot spots, lamp current crest factor and cost are presented in this paper. The operational principles and limitations of the aforementioned electronic ballasts are described qualitatively on which the comparison and examination of these aspects are, consequently, addressed. This work provides physical insight of electronic ballasts and furnishes thorough background knowledge for designers in selecting an appropriate one. The theoretical discussions and analyses are verified by experimental measurements.<<ETX>>

A PSpice circuit model for low-pressure gaseous discharge lamps operating at high frequency

A simple, but accurate, PSpice circuit model simulating the electrical characteristics of low-pressure gaseous discharge lamp operating at high frequency is proposed. The model is constructed from a two-parameter equation and is suitable for computer simulation and analytic derivation in a preliminary design of electronic dimming ballasts. Simulated and measured results are used to verify the theoretical discussion.

Self excited half-bridge series resonant parallel loaded fluorescent lamp electronic ballasts

Time-domain analyses are given for the electronic ballasts adapted from a self excited half-bridge series resonant parallel loaded inverter operating in either high quality factor (>2.5) or low quality factor (/spl ap/1.0) conditions. The operational principles of the inverter applied as an electronic ballast are described in detail from which the voltage and current stresses imposed on switching devices can be determined analytically, and a systematic design procedure can be, therefore, outlined. In addition, practical considerations taking into account the storage time of the switching devices and the nonlinear characteristics of the saturable core are addressed. The computer simulations and experimental results from a laboratorial prototype are used to verify the theoretical predictions and discussions.<<ETX>>

Single-stage converters for photovoltaic powered lighting systems with MPPT and charging features

This paper proposes single-stage power converters (SSCs) for application in photovoltaic powered lighting systems. The synchronous switch technique is employed to synthesize the SSCs which can fulfill maximum power point tracking, battery charging, discharging and lamp ballasting features. Several typical SSCs are discussed in the paper. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed. Both pulse-width modulation and variable-frequency controls are used to govern the system. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has the merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems.

Analysis and design of a high power factor, single-stage electronic dimming ballast

This paper presents the analysis, design and practical consideration of a single-stage electronic dimming ballast with unity power factor. The power stage of the ballast is derived from combining a buck-boost power converter and a half-bridge series-resonant parallel-loaded inverter (SRPLI). With the plasma model of the lamp, the analysis of the ballast is carried out, from which the key equations used for dimming control are derived. Starting performance and dimming consideration are also addressed in the paper. In this dimming ballast, both pulsewidth modulation (PWM) and variable-frequency control strategies are employed. The discussed ballast with the controls can save a controller and a switch driver, reduce size and cost, and possibly increase system reliability over conventional two-stage systems in the applications with moderate power level. Simulated and experimental results of the ballast for an OSRAM T8 32-W lamp are used to verify the discussion.

An electronic dimming ballast with bifrequency and fuzzy logic control

This paper presents the analysis and design of a series-resonant parallel-loaded inverter applied to electronic dimming ballasts with bifrequency and fuzzy logic control. The analysis of the ballast is carried out in conjunction with the fluorescent lamp represented in a plasma model. The component values of the power stage, as well as two switching frequencies, according to the desired maximum and minimum power levels are, therefore, determined. The power levels in between are controlled by varying the ratio between two time intervals for which the two frequencies last, respectively. This mechanism is achieved by using a fuzzy logic controller (FLC). A ballast prototype with the FLC which is implemented on an 8-bit microprocessor with a reduced instruction set computer architecture has been built. Experimental measurements have shown the feasibility of the ballast with the proposed control strategy.