Moshe Shvartsas

Statics and dynamics of fluorescent lamps operating at high frequency: modeling and simulation

The static and dynamic response of a fluorescent lamp operating at high frequency was studied and modeled by a SPICE-compatible behavioral equivalent circuit. Good agreement was found between model simulations and experimental results. It was also found analytically that the proposed model predicts a zero at the right half-side of the complex plane as observed experimentally.

Analysis and modeling of a voltage doubler rectifier fed by a piezoelectric transformer

Piezoelectric transformers (PZT) can be used advantageously in high output voltage dc-dc converters. In such applications the output section includes a voltage doubling rectification scheme to help increase the output voltage. This topology was modeled and analyzed by considering the expected voltage and current waveforms under the first harmonics approximation. The results were then used to build a linear ac equivalent circuit that emulates the ac-dc stage. The proposed model was verified against simulation and experimental results.

A SPICE compatible model of high intensity discharge lamps

A SPICE compatible model of high intensity discharge (HID) lamps was developed and verified against experimental results. The model is based on fundamental physical-thermal principles and applies lamp parameters and universal constants. The model was found to faithfully emulate the static and dynamic electrical responses of a high pressure sodium (HPS) lamp under low frequency (50 Hz) and high frequency (30 kHz) excitation.

Analysis and modeling of a piezoelectric transformer in high output voltage applications

Piezoelectric transformers (PZT) can be used advantageously in high output voltage DC-DC converters. In such applications, the output section includes a voltage doubling rectification scheme to help increase the output voltage. This topology was modeled and analyzed by considering the expected voltage and current waveforms under first harmonics approximation. The results were then used to build a linear AC equivalent circuit that emulates the AC-DC stage. The proposed model was verified against experimental results.

A behavioral SPICE compatible model of an electrodeless fluorescent lamp

A behavioral, SPICE compatible, model was developed for an electrodeless fluorescent lamp (OSRAM SYLVANIA ICETRON/ENDURA 150W). The model emulates the static and dynamic behavior of the lamp when driven at high frequency. The model was tested under various experimental conditions: at steady state for different power levels, with an AM modulated drive, and under transient changes. Good agreement was found between the simulation runs and experimental results. However, the effect of temperature on the lamps behavior may require a tighter fit of the model to the temperature dependence in cases where large changes in operating condition need to be simulated.

An electronic ballast for fluorescent lamps with no series passive elements

This exploratory study examined the possibility of driving a fluorescent lamp at high frequency with no serially connected passive elements. The proposed driver is a full bridge stage controlled by the phase shifted PWM scheme. Current feedback was used to stabilize the average of the rectified lamp current to a set value. The experimental results of this research confirm the conjecture that an all-electronic fluorescent driver is feasible. Lamp V-I characteristics and lamp resistances were found to be comparable to those measured when the lamp is driven by a conventional HF electronic ballast. The measured light output of a lamp driven by proposed ballast was found to be slightly higher than the light output of same lamp when driven by a conventional HF ballast for the same input power. The paper covers the issue of feedback consideration for ensuring dynamic stability.

HF Multiresonant Electronic Ballast for Fluorescent Lamps With Constant Filament Preheat Voltage

A novel HF multiresonant ballast for fluorescent lamps is analyzed, simulated, and tested experimentally. The ballast includes two major resonant networks. The lamp is driven by a parallel resonance arrangement that acts as a current source. During warm-up the filaments are driven by a secondary winding of a series-resonant inductor. The series resonance branch, which is active during warm-up, feeds the filament and shorts out the voltage across the lamp. Simulation and experimental results suggest that the inherent features of the proposed ballast topology will prolong lamp life.

HF multiresonant electronic ballast for fluorescent lamps with constant filament preheat voltage

A novel HF multiresonant ballast for fluorescent lamps is analyzed, simulated, and tested experimentally. The ballast includes two major resonant networks. The lamp is driven by a parallel resonance arrangement that acts as a current source. During warm-up the filaments are driven by a secondary winding of a series-resonant inductor. The series resonance branch, which is active during warm-up, feeds the filament and shorts out the voltage across the lamp. Simulation and experimental results suggest that the inherent features of the proposed ballast topology will prolong lamp life.A novel HF multiresonant ballast for fluorescent lamps is analyzed, simulated, and tested experimentally. The ballast includes two major resonant networks. The lamp is driven by a parallel resonance arrangement that acts as a current source. During warm up the filaments are driven by a secondary winding of a series resonant inductor. The series resonance branch, which is active during warm up, feeds the filament and shorts out the voltage across the lamp. Simulation and experimental results suggest that the inherent features of the proposed ballast topology will prolong lamp life.

Stability of a levitation melting system fed by an ideal series resonant converter

Electromagnetic levitation melting process is occasionally employed in the metallurgical industry to melt metals in a sterile environment without the risk of specimen contamination by crucible materials. The stability of this process is affected by the system geometry, the construction materials and the power supply design. This paper presents a new analytical stability analysis model of a levitation-melting system fed by an ideal series resonant converter working with a constant switching frequency. It is found that a response delay, of the current envelope signal in the coil, to changes in specimen position has an impact on the system stability. Simulation results validate the developed analytical model.

High current short pulse generator for pulse magneto-oscillation (PMO) research

Pulse magneto-oscillation (PMO) is one of the new techniques, developed for solidification structure refinement of metals and alloys, as it is was found in experimental results from the last decade. When electromagnetic pulses are applied to a molten metal during its solidification, the Lorentz forces causes to pressure waves, which change the microstructure from columnar dendrites to globular grains. PMO has a great potential in precise controlling of the solidification microstructure. The current work presents the development and the construction of a high current short pulse generator, which was required for the PMO research. The sample configuration consists of the non conductive crucible with a molten metal, which is placed coaxially inside a solenoid coil. The pulse generator is able to introduce short pulses with current amplitude of kA order into the coil. The proposed generator is based on resonance LCL circuit structure using a high current SCR switch. The fundamental idea of the power system is to convert a low-power, long-time input into a high-power, short-time output. Using resonant LC topologies, the durable resonant capacitor charging process established firstly, drawing low current from the net. Afterward, high frequency, high amplitude capacitor discharging process provides the necessary current to the work coil. The calculations and simulations of the system parameters and operation are described and the results of the experimental system behavior are shown. The theoretical considerations and the test results were found to be closely resembled.