Fluorescent lamps are in general driven by ac ballasting currents. The cyclic variation in arc discharging power results in light fluctuation at twice the frequency of the ac current. Light fluctuation may be intolerable when a steady light output is required in some particular applications. To eliminate light fluctuation, an electronic ballast with dc current is proposed to operate the fluorescent lamp at a constant power. The main power conversion of the electronic ballast employs the single-stage high-power-factor inverter, which is originated from a combination of the half-bridge resonant inverter and the buck-boost converter. With such a circuit configuration, the output power can be regulated by asymmetrical pulse-width-modulation. The ac output of the inverter is then rectified and filtered to provide the dc ballasting current. Driven by dc current, however, the fluorescent lamp emits electrons unilaterally from one end leading to wearing out of emission material on the cathode filament. To solve this problem, an inverter is integrated for commutation of the lamp electrodes. Furthermore, a preheating control is included to start the fluorescent lamps with zero glow-current. A prototype is designed and built for the OSRAM T5-80W fluorescent lamp. The dc operating characteristics of starting transient, light fluctuation, lighting spectra, color temperature as well as the light fluctuation are investigated from experiments. Experimental results also show that the electronic ballast is capable of high-power-factor, dimming capability and zero glow-current preheating.

A flash lighting circuit with the fluorescent lamp is designed to produce lighting flicker by means of controlling the operating frequency and the duty-ratio of the lamp voltage and current. The intensity of the flash lighting is adjusted by the DC-link voltage of the electronic ballast circuit. The circuit structure is mainly composed of the class-D series-resonant inverter, the full-bridge rectifier, the LC filter and the commutation circuit. A control circuit with complex programmable logic device (CPLD) is used to accomplish the regulation of the operating frequency and the duty-ratio, which should be carefully controlled to ensure a stable lighting arc. In the meantime, a flash lighting detected circuit is designed to transform the flash lighting into a voltage signal. Experiment tests are conducted to human visual perception to demonstrate the applicability of the flash lighting circuit.

To minimize the size of the electronic ballast, a half-bridge load- resonant inverter with a cascading Rosen-type piezoelectric transformer (PT) is designed for cold cathode fluorescent lamps (CCFLs). The electrical characteristics of the PT are investigated to obtain a higher voltage gain by adapting the load impedance to the interposed network. The circuit parameters are selected under the considerations of (1) the minimum inductor size, (2) the higher circuit efficiency, (3) the rated current of the PT, and (4) the stable lamp operation. The electronic ballasts are designed for operating the lamp at the rated lamp power and with dimming control by asymmetrical pulse-width-modulation (APWM),respectively. Laboratory circuits are assembled and, experimental tests are carried out to validate the theoretical analyse

A single-stage high-power-factor electronic ballast with class E inverter is proposed for driving the fluorescent lamp. The circuit configuration is obtained from the integration of a buck-boost converter for power-factor- correction (PFC) and a class E resonant inverter for ballasting. The integrated ballast circuit requires only one active power switch and simple control. Operating the buck-boost converter in discontinuous conduction mode (DCM) at a fixed frequency, the electronic ballast can achieve nearly unity power factor. With pulse-width-modulation (PWM), the electronic ballast can provide an appropriate filament current for preheating, a high voltage for ignition, and then a desired lamp current for steady-state operation. An additional control circuit is included to eliminate the glow current during preheating stage. The operation of the ballast-lamp circuit is analyzed by fundamental approximation. Computer simulations are made and design equations are derived on basis of the power-dependent resistance model of the fluorescent lamp. With carefully designed circuit parameters, the active power switch can be switched on at zero current to reduce the switching losses leading to a higher efficiency. An experimental circuit designed for a PL-27W compact fluorescent lamp is built and tested to verify the computer simulations and analytical predictions. Experimental results show that satisfactory performances can be obtained on the proposed electronic ballast.

This thesis proposes a single-stage high-power-factor electronic ballast with series-resonant inverter for rapid-start fluorescent lamps with zero glow current during preheating period. A buck-boost converter is integrated into the ballast as the power-factor-corrector. Two auxiliary windings are wound on the same core of the buck-boost inductor for filament heating. During the preheating period, the buck-boost converter is initiated while the series-resonant inverter is disabled by controlling the corresponding active power switches. Due to zero voltage across the lamp, the glow current can be effectively eliminated. As the filaments reach appropriate emission temperature, the series-resonant inverter is activated. The lamp is then ignited and consequently operated at the rated lamp power. Circuit analyses and experimental tests of the proposed preheating control scheme are carried out on an electronic ballast for a T8-40W rapid-start fluorescent lamp.

Η εργασία αυτή εχεις ως αντικείμενο την μελέτη και την κατασκευή ενός μετατροπέα συντονισμού για την οδήγηση ενός πιεζοηλεκτρικού κινητήρα οδεύοντος κύματος τύπου Ultrasonic. Αρχικά γίνεται μια θεωρητική αναφορά στους πιεζοηλεκτικούς κινητήρες και τους ηλεκτρονικούς μετατροπείς ισχύος ενώ ακολουθεί η προσομοίωση του μετατροπέα στο Pspice. Ακολούθως αναλύεται η διαδικασία της κατασκευής και ακολουθούν τα πειραματικά αποτελέσματα καθώς και τα συμπεράσματα που λάβαμε. / In this thesis someone can find about designing and manufacturing a resonant inverter in order to control a piezoelectric traveling wave ultrasonic motor. In the first chapters someone can read about the piezoelectric phenomenon, piezoelectric motors and about electronic converters which control the velocity of motors. Next there is a presentation of the Pspice simulation model and results. Furthermore there is the manufacturing procedure of the inverter and at the end there are the results and conclusion of the thesis.

No description available.

Modern power systems require multiple conversions between DC and AC to deliver power from renewable energy sources. Recent growth in DC loads result in increased system costs and reduced efficiency, due to redundant conversions. Advances in DC microgrid systems demonstrate superior performance by reducing conversion stages. The literature reveals practical DC microgrid systems composed of wind and solar power to replace existing fossil fuel technologies for residential consumers. Although higher efficiencies are achieved, some household appliances require AC power; thus, the need for highly efficient DC to AC converters is imperative in establishing DC microgrid systems. Resonant inverter topologies exhibit zero current switching (ZCS); hence, eliminate switching losses leading to higher efficiencies in comparison to hard switched topologies. Resonant inverters suffer severe limitations mainly attributed to a load dependent resonant frequency. Recent advancements in power electronics propose an electronically tunable inductor suited for low frequency applications [24], [25]; as a consequence, frequency stability in resonant inverters is achievable within a limited load range. This thesis characterizes the operational characteristics of a low-frequency series loaded resonant inverter using a manually tunable inductor to achieve frequency stability and determine feasibility of utilization. Simulation and hardware results demonstrate elimination of switching losses via ZCS; however, significant losses are observed in the resonant inductor which compromises overall system efficiency. Additionally, harmonic distortion severely impacts output power quality and limits practical applications.

No description available.

This thesis proposes a high efficiency driving circuit for multiple light emitting diode (LED) lamps with dimming feature. The driving circuit consists of essentially a high-frequency half-bridge series resonant inverter with multiple output transformers, on which primary windings are connected in series, while secondary sides are loaded by LED lamps rated at different powers with different turn ratios. By controlling the frequency of the inverter, the resonant current as well as the lamp current can be regulated simultaneously. On the other hand, the LED lamps can be dimmed individually by the associated dimming switches with integral cycle control. The tactful circuit ensures a high circuit efficiency owing to less conducting losses and zero-voltage switching (ZVS) operation of the active power switches of the inverter and zero current switching (ZCS) operation of the dimming switches. Two prototype circuits designed for 60 W three RGB LED lamps and 50 W five white light LED lamps have been built and tested to verify the analytical predictions. Experimental results demonstrate that the driving circuit can operate the LED lamps at a high efficiency with a wide dimming range. The lamp power can be dimmed to 10% with frequency control, while whole dimming range can be achieved with integral cycle control. The circuit efficiency with integral cycle control is relatively higher than that with frequency control. The measured efficiencies for the two designed circuit are 93% and 90%, respectively, under the rated powers.