Half-bridge Series-resonant Parallel-loaded Inverter Research Articles

A Novel Single-Stage HPF Electronic Ballast With Coupled Inductors for Fluorescent Lamps

This paper proposes a novel single-stage electronic ballast with high power factor (HPF) for supplying fluorescent lamps. The presented electronic ballast integrates a dual boost converter with coupled inductors and a half-bridge series-resonant parallel-loaded inverter into a single-stage power conversion topology. The features of the ballast are cost-effectiveness, HPF (PF > 0.98), high circuit efficiency (>90%), low input current total harmonic distortion (THD <; 7%), low level of crest factor (CF <; 1.4), and zero-voltage switching obtained on both two power switches. Operational principles, design equations, and experimental results of one T5-type fluorescent lamp with a rated power of 21 W operating at 50 kHz switching frequency with 110 V-RMS line input voltage are presented. Satisfactory results demonstrate the feasibilities of the proposed ballast.

Design and Implementation of Dimmable Electronic Ballast for Fluorescent Lamps Based on Power-Dependent Lamp Model

A simple and easy-to-use electric-circuit model for fluorescent lamps is deduced from experimental tests. The lamp arc is modeled as a power-dependent resistance. By incorporating the lamp model with electronic ballast, design equations for dimmable electronic ballasts using half-bridge resonant inverter are derived, and then the dimming operation characteristics can be predicted analytically. Detailed analysis and design of a dimmable electronic-ballast fluorescent-lamp circuit with frequency control are presented. Accordingly, design guidelines for determining circuit parameters are provided. An electronic ballast with half-bridge series-resonant parallel-loaded inverter is used as an example for illustrating the design procedure. A prototype circuit for a T8-36W fluorescent lamp is built and tested to verify the validity of the proposed model.

Single-stage high-power-factor electronic ballast with complex frequency modulation for HID lamps

A single-stage, complex frequency-modulated (CFM), high-frequency-driven electronic ballast for high-intensity-discharging (HID) lamps is proposed. The presented ballast combines a power-factor-correction (PFC) converter with a half-bridge series-resonant parallel-loaded inverter as well as a CFM controller. The switching frequency of the integrated inverter is non-periodically modulated by the CFM signal that integrates DC-bus voltage ripples with an additional high-frequency sine-wave signal. Compared with constant-frequency and frequency-modulated (FM) control, the presented ballast offers a widely continuous power spectrum of lamp current with decreased amplitude in order to effectively expand the lamp power as well as reducing sideband frequencies and allowing for a much lower energy level of the eigen frequency that supplies the lamp. Because of its CFM operation, no acoustic resonance occurs; additionally, the obtained results include a 13 dBm reduction of power spectrum at the centre switching frequency compared with FM control, and a 22 dBm reduction compared with constant-frequency control. The ballast offers high power factor (0.99), high efficiency (90%), cost-effectiveness and a simple, easy-to-implement controller. A prototype ballast utilising the CFM control method with 110 V utility-line input voltage has been built, and experimental results were carried out on three different brands of 70 W metal-halide-type HID lamps

Design and implementation of frequency-modulated electronic ballast for metal-halide lamps

A two-stage, frequency-modulated (FM), high-frequency-driven electronic ballast for metal-halide (MH) lamps is proposed. The presented ballast consists of a power-factor-correction (PFC) converter as the first stage, a half-bridge series-resonant parallel-loaded (HB-SRPL) inverter as the second stage, and a frequency-modulation controller. The advantageous features of the high-frequency-operated ballast are its compact size and reduced weight. With constant-frequency control, the switching frequency of the ballast must be carefully designed within a frequency window that is free from acoustic resonance, and the envelope of the lamp current is large owing to the DC-bus voltage ripple that occurs on the PFC output. However, if the switching frequency of the inverter is operated outside of the stable operation window or if the energy of some eigenfrequency is sufficiently higher, then acoustic resonances will exist. An FM-controlled electronic ballast for MH lamps is proposed. The switching frequency of the HB-SRPL inverter, whose centre frequency is intentionally designed at a frequency at which acoustic resonances occur, is periodically modulated by the voltage ripples of the PFC output. The presented ballast offers a lower envelope of lamp current in order to expand the power spectrum of the lamp and to decrease the energy of the eigenfrequency that supplies the lamp. Owing to its FM operation that allows for an adequately modulated index, no acoustic resonance occurs. The ballast offers cost-effectiveness, a simple control circuit without an external modulation signal, and a low crest factor (&lt;1.45). Design guidelines and experimental results are presented for a 70 W MH lamp ballast that utilises the FM control method with universal-line input voltage.

TRIAC Dimmable Ballast With Power Equalization

A two-stage, two-wire TRIAC dimmable electronic ballast for fluorescent lamps is presented in this paper. It is constructed by using a flyback converter as the input power factor corrector to supply a half-bridge series-resonant parallel-loaded inverter to ballast the lamp. The flyback converter is operated in discontinuous conduction mode so that the filtered input current profile is the same as the TRIAC-controlled voltage waveform. The switches in the inverter are switched at a constant frequency slightly higher than the resonant frequency of the resonant tank. Based on the constant average input current characteristics of the inverter, the dimming operation is simply achieved by pulsewidth modulation control of the magnitude of the flyback converter output voltage. No synchronization network is required between the input and output stages. In addition, a linear power equalization scheme is developed so that the dc-link voltage (and hence the lamp power) is in a linear relationship with the firing angle of the TRIAC. The average output voltage of the dimmer controls the equalized flyback converter output voltage. Modeling, analysis, and design of the ballast will be described. A prototype was implemented to verify the experimental measurements with the theoretical predictions.

Use of Saturable Inductor to Improve the Dimming Characteristics of Frequency-Controlled Dimmable Electronic Ballasts

This work presents an investigation into the use of saturable inductor to improve the dimming characteristics of frequency-controlled dimmable electronic ballasts with a half-bridge series-resonant parallel-loaded inverter. The concept is based on the fact that the effective resonant frequency increases as the inductor current increases, if the unsaturable inductor in the resonant tank circuit is replaced with a saturable one. Susceptibility of the lamp power to the switching frequency variation at low luminous level can be reduced. This can lessen the problem of lamp flickers at dimmed level and result in a wider dimming range and improved controllability. The method gives a simple solution of improving the dimming characteristics without changing the circuit structure. A fundamental frequency model that includes the characteristics of the nonlinear lamp resistance and filament resistance is applied in the analysis. A PSIM simulation model for the saturable inductor is developed. Theoretical predictions are verified with the experimental results of a 36-W T8 prototype.

A novel single-stage high-power-factor electronic ballast with symmetrical topology

This paper proposes a novel single-stage high-power-factor high-efficiency electronic ballast with symmetrical topology for fluorescent lamps. The circuit topology originates from the integration of two half-wave rectifiers with buck-boost power-factor-correction converters and a half-bridge series-resonant parallel-loaded inverter. A high power factor at the input line is assured by operating the buck-boost converters in discontinuous conduction mode. With symmetrical operation and carefully designed circuit parameters, zero-voltage switching on the active power switches of the inverter can be retained to achieve high circuit efficiency. The design equations are derived from the analyzed results based on fundamental approximation, and then an easy-to-use design tool is provided accordingly under considerations of filament heating and ignition. A prototype circuit designed for two T9-40W rapid-start fluorescent lamps is built and tested to verify the analytical predictions. Satisfactory performance is obtained from the experimental results.

A comparative study on dimming control methods for electronic ballasts

This paper presents a comparative study on the performance characteristics between the variable switching frequency and variable DC link voltage control schemes for the dimming operation of electronic ballasts using a half-bridge series-resonant parallel-loaded inverter. Attributes under investigations include (1) average input current of the inverter; (2) dimming characteristics; (3) variations of the filament power and starting voltage throughout the dimming range; (4) dead time boundaries for ensuring zero-voltage-switching in the inverter. An approximated fundamental-frequency model that includes the characteristics of the nonlinear lamp resistance and filament resistance is used. Theoretical predictions are favorably verified with the experimental measurements in two 36 W Ballast-lamp systems.

High-efficiency low-stress electronic dimming ballast for multiple fluorescent lamps

An electronic dimming ballast with a lead-lag tank operation (LLTO) having the properties of high efficiency and low stress is introduced in this paper. The ballast is configured with a voltage-fed half-bridge series-resonant parallel-loaded inverter (SRPLI) acting as a lamp driver. It is loaded with resonant tanks which are designed and operated to be capacitive and inductive to theoretically achieve both zero-voltage switching (ZVS) and zero current switching (ZCS) and to eliminate the reactive current circulating through the switches, resulting in low switching and conduction losses. Moreover, the merit of a successive lamp ignition can be attained with the proposed operation scheme so that current stress imposed on the switches can be reduced. With the plasma model of fluorescent lamps, the analysis, operating principle, and dimming control strategy of the electronic ballast are described in detail. On the other hand, the limitations of the proposed scheme are pointed out. Computer simulation results and experimental measurements are used to verify the theoretical prediction and analytical discussion.

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.

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.