A high-frequency electronic ballast with auto-tracking control was proposed to operate the metal halide lamps at a specific frequency free from acoustic resonance. In case the acoustic resonance should happen, the operating frequency is changed step by step with the auto-tracking control, until the lamp is operated at a frequency with stable operation. The electrical characteristics of the lamps are first investigated. Based on the investigated results, a detection circuit is designed to identify the occurrence of acoustic resonance. With the auto-tracking control, the Class-D half-bridge series-resonant inverter can be adopted for the high-frequency electronic ballast to achieve high efficiency and high power density. The control strategy of auto-tracking is practically realized by a single-chip microprocessor. The proposed approach is implemented on a 70 W test lamp with an operating frequency range from 20 kHz to 30 kHz. To regulate the lamp power at its rated value, a buck-boost converter is used as a pre-regulator, which serves also as a power-factor-corrector to achieve a high power factor at the input line.

Design and realisation of electronic regulated ballast with USB interface. The ballast has three functions: constant I, constant U and constant R. This device is intended for example to measure discharge curves of accumulators.

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Small size, light weight, high efficacy, longer lifetime and controllable output are the main advantages of high-frequency electronic ballasts for gas discharge lamps. However, power line quality and electromagnetic interference (EMI) issues arise when a simple peak rectifying circuit is used. To suppress harmonic currents and improve power factor, input-current-shaping (ICS) or power-factor-correction (PFC) techniques are necessary. This dissertation addresses advanced high-frequency electronic ballasting techniques by using a single-stage PFC approach. The proposed techniques include single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends, single-stage PFC electronic ballasts with wide range dimming controls, single-stage charge-pump PFC electronic ballasts with lamp voltage feedback, and self-oscillating single-stage PFC electronic ballasts. Single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends are developed to solve the problem imposed by the high boost conversion ratio required by commonly used boost-derived PFC electronic ballast. Two circuit implementations are proposed, analyzed and verified by experimental results. Due to the interaction between the PFC stage and the inverter stage, extremely high bus-voltage stress may exist during dimming operation. To reduce the bus voltage and achieve a wide-range dimming control, a novel PFC electronic ballast with asymmetrical duty-ratio control is proposed. Experimental results show that wide stable dimming operation is achieved with constant switching frequency. Charge-pump (CP) PFC techniques utilize a high-frequency current source (CS) or voltage source (VS) or both to charge and discharge the so-called charge-pump capacitor in order to achieve PFC. The bulky DCM boost inductor is eliminated so that this family of PFC circuits has the potential for low cost and small size. A family of CPPFC electronic ballasts is investigated. A novel VSCS-CPPFC electronic ballast with lamp-voltage feedback is proposed to reduce the bus-voltage stress. This family of CPPFC electronic ballasts are implemented and evaluated, and verified by experimental results. To further reduce the cost and size, a self-oscillating technique is applied to the CPPFC electronic ballast. Novel winding voltage modulation and current injection concepts are proposed to modulate the switching frequency. Experimental results show that the self-oscillating CS-CPPFC electronic ballast with current injection offers a more cost-effective solution for non-dimming electronic ballast applications. / Ph. D.

The dissertation investigates the starting transient behaviors of metal halide lamps driven by constant currents and constant powers, respectively. Based on the investigation results, three starting scenarios are proposed for shortening the starting time, and an identification strategy is figured out for designing an electronic ballast being capable of driving three small-wattage lamps rated at different powers. A laboratory electronic ballast is designed to drive small-wattage metal halide lamps with a programmable low-frequency square-wave current. Experiments are conducted to examine the effects of the starting current on variations of the light output as well as the lamp voltage and power. From the effects of the applied current on the generated luminance, three starting scenarios are attempted to accelerate the starting transient stage. Experimental evidence shows that the starting time can be effectively shortened by increasing the lamp current during glow-to-arc and warm-up stages. A short interval of over-power operation during the warm-up stage enables the lamp to further enhance the producing of luminance quickly, and hence greatly reduce the starting transient period. According to the starting transient characteristics of metal halide lamps, an identification strategy is figured out to recognize three small-wattage metal halide lamps rated at powers of 20-W, 35-W and 70-W from three world-wide prominent brands, GE, OSRAM and PHILIPS. An electronic ballast is designed to drive the metal halide lamps with the multi-stage constant-power starting scenario. Experimental results evidence that the electronic ballast with the proposed identification strategy can recognize three lamps¡¦ rated powers correctly during the starting transition, and drive the lamp to its rated power before entering the steady-state.

According to the regulation announced by Bureau of Standard, Metrology & Inspection (BSMI) of Ministry of Economic Affairs (MOEA), lamp fixtures must follow safety and electromagnetic compatibility (EMC) standards. However, the self-ballasted fluorescent lamps in the fixture should only be approved by the safety test but not regulated by EMC standard. Obviously, fixtures without light bulbs do not generate any electromagnetic noise. Electromagnetic interference (EMI) comes from the fluorescent light bulb embedded with an electronic ballast which included an inverter with high-frequency switching. A variety of tests demonstrate evidently that a fixture with different self-ballasted compact fluorescent lamps may possibly violate the EMC standard, revealing the absurdity of the regulation. In fact, self-ballasted fluorescent lamps use mostly self-excited electronic ballasts. The operating frequencies for this kind of electronic ballasts can not be precisely controlled due to the influence of many factors. They are not operated at a specified frequency but in a frequency range. This means that the generated EMI spectrum is hardly predicted, especially when a fixture is fitted by light bulbs from several manufacturers. This research inducts the worst cases from numerous measurements on a fixture with 1 piece to 8 pieces of light bulbs, and then attempts to design an EMI filter for all cases. As a result, a lamp fixture with the filter at the line input terminal can suppress the EMI. As long as the consumer buys the lamp fixture which are installed with the EMI filter together with any bulb in use, EMI noise can comply with standard limits.

The operating characteristics of metal halide lamps are investigated, including acoustic resonance, spectral energy, and luminous efficacy. To operate metal halide lamps at intended conditions, two test sophisticated ballast circuits are built to drive the lamps with sine-wave current and square-wave current, respectively. One ballast employs the series resonant inverter to output sinusoidal lamp current over a high-frequency range from 20 kHz to 300 kHz. The other makes use of the full-bridge inverter to drive the lamps with square-wave current from 50 Hz up to 300 kHz. For both test circuits, the operating frequency and the magnitude of the lamp current can be controlled independently. On the other hand, the lamp power is adjusted by regulating the DC-link power. Several conclusions are drawn from experimental results: (1) Little difference is found between the lighting spectra of a lamp when driven by sinusoidal current and square-wave current. (2) Luminous efficiency deteriorates as the operating frequency increases. The deterioration is more significant at lower frequencies. (3) Luminous efficiency decreases considerably as the lamp power is reduced. (4) Arc instability from acoustic resonance is highly related to the waveform of the lamp current. The investigated results give better understanding on the steady state operation of metal halide lamps and provide useful information for the design of the electronic ballasts.

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.

A single-stage high-power-factor electronic ballast is designed for fluorescent lamps with dimming capability. The circuit configuration is originated from the integration of the half-bridge resonant inverter and the buck-boost converter. The buck-boost converter is designed to operate in discontinuous conduction mode (DCM) to provide nearly unit power factor at a fixed switching frequency. With asymmetrical pulse-width-modulation (APWM), the lamp power can be effectively regulated. The power switches of the inverter exhibit either zero-voltage-switching (ZVS) or zero-current-switching (ZCS) over the whole dimming range. Design equations are derived and computer analyses are performed based on a power-dependent lamp model and fundamental approximation. Design guidelines for determining circuit parameters are provided. A prototype circuit for a T8-36W fluorescent lamp is built and tested to verify the analytical predictions.