Shmuel Ben-Yaakov

H/sup /spl infin// control applied to boost power converters

The controller in a pulse-width-modulation (PWM) power converter has to stabilize the system and guarantee an almost constant output voltage in spite of the perturbations in the input voltage and output load over as large a bandwidth as possible. Boost and flyback power converters have a right-half-plane zero (RHPZ) in their transfer function from the duty cycle to the output voltage, which makes it difficult to achieve the aforementioned goals. Here, the authors propose to design a controller using H/sup /spl infin// control theory, via the solution of two algebraic Riccati equations. The almost optimal H/sup /spl infin// controller is of the same order as the converter and has a relatively low DC gain. The closed-loop characteristics of a typical low-power boost power converter with four different control schemes were compared by computer simulation. The H/sup /spl infin// control was found to be superior in a wide frequency range, while being outperformed by the others at extremely low frequencies. Good agreement was found between simulation results and experimental measurements.

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.

A comparison of piezoelectric transformer AC/DC converters with current doubler and voltage doubler rectifiers

The objective of this study was to develop recommendations for an optimal design of piezoelectric transformer (PT) AC/DC converters. The paper presents a comprehensive comparison of the two commonly used rectifier topologies in a PT based power converters: current doubler and voltage doubler rectifiers. The advantages and disadvantages of the two rectifiers were investigated and the range of their applications with respect to output current, voltage, power capability, load resistance etc.-was delineated. Generic parameters are proposed and used to derive normalized and closed form equations that can help choosing a PT for a given set of requirements. Simulation and experimental results were found to be in a good agreement with the derivation of the theoretical analysis.

Average-Current-Based Conduction Losses Model of Switched Capacitor Converters

A generic modeling methodology that analyzes the losses in switched capacitor converters (SCC) operating in open loop was developed and verified by simulation and experiments. The proposed analytical approach is unified, covering both hard- and soft-SCC topologies that include active switches and/or diodes. An important feature of the proposed model is that it expresses the losses as a function of the average currents passing through each flying capacitor during each switching phase. Since these currents are linearly proportional to the output current, the model is also applicable to SCC with multiple capacitors if it can be assumed that each of the subcircuits of the modeled SCC can be described or approximated by a first-order system. The proposed model can be used to assess the effect of the operational conditions of the SCC, such as switching frequency and duty cycle, on the expected losses. As such, the model can help in the optimization of SCC systems and their control to achieve high efficiency and the desired regulations.

On the Influence of Switch Resistances on Switched-Capacitor Converter Losses

The contribution of switch resistances to the losses in switched-capacitor converters (SCC) is reevaluated. The results reaffirm the crucial role that the switch resistances play in the design of open-loop and regulated SCC.

Envelope simulation by SPICE-compatible models of electric circuits driven by modulated signals

SPICE-compatible equivalent circuits were developed to facilitate the analysis and envelope simulation of electric circuits driven by modulated signals. The circuits are based on a novel complex phasor domain transformation. The proposed method facilitates fast simulation of any general linear circuit driven by a modulated signal, such as amplitude, frequency, or phase modulation.

Behavioral Average Modeling and Equivalent Circuit Simulation of Switched Capacitors Converters

A generic behavioral average circuit model of a switched capacitor converter (SCC) is proposed and demonstrated by a unity conversion SCC. The model is based on the average currents concept and can be used to calculate or simulate the average values of the SCC variables such as output voltage, capacitor voltages, and subcircuit currents. The model is valid for all operational ranges of an SCC (complete, partial, and no charge) and is compatible with any circuit simulator that includes dependent sources. Excellent agreement was found between full switched-circuit simulation, average simulation by proposed model, and experimental results.

Current-sourcing push-pull parallel-resonance inverter (CS-PPRI): theory and application as a discharge lamp driver

A novel topology, current-sourcing push-pull parallel-resonance inverter (CS-PPRI) was investigated theoretically and experimentally. The proposed power stage is built around a current fed push-pull inverter. The main features of the proposed inverter are: a load independent output current and zero voltage switching (ZVS). It is suggested that the proposed CS-PPRI is a viable alternative for realizing electronic ballasts for low and high-intensity discharge lamps. >

Dynamic interaction analysis of HF ballasts and fluorescent lamps based on envelope simulation

A SPICE-compatible simulation methodology for analyzing open- and closed-loop high-frequency electronic ballasts for a fluorescent lamp was developed. The proposed procedure applies envelope simulation and makes use of the SPICE-compatible model of a fluorescent lamp. Experimental results validate the reliability of proposed simulation method.

Self-Contained Resonant Rectifier for Piezoelectric Sources Under Variable Mechanical Excitation

A rectification scheme is proposed for increasing the available output power of electrical generators that have a high output capacitance. The proposed rectifier could be useful in increasing the output power of piezoelectric generators (PZG) that convert mechanical vibrations into electrical power. The improvement is achieved by a resonant circuit that self commutates the voltage across the output terminals of the PZG and thereby eliminates the shunting of the output current by the output capacitor. A low-consumption circuit synchronously controls the operation of the resonant rectifier by detecting voltage transitions across the generator. The presented resonant rectifier was experimentally verified by connecting it to a PZG as well as to a PZG emulator. The results show that, under constant harmonic excitation, the proposed circuit can significantly increase the extracted power by up to 230% as compared to a conventional bridge rectifier. The feasibility of using the proposed topology as a self-powered system driven by variable excitation was investigated experimentally as well. In particular, the system was driven by two types of excitation source: amplitude modulated and frequency modulated. It was found that the proposed circuit increases the extracted power by 160% and 172% for AM and FM excitations, respectively.