Sam Ben-Yaakov

The dynamics of a PWM boost converter with resistive input

This paper investigates the large- and small-signal response issues and, in particular, the inner loop gain and outer loop response of an indirect control method for active power-factor correction. The control scheme is based on sensing the average inductor current and generating a D/sub OFF/ (the complement of the switch duty cycle) which is proportional to the current. The method is demonstrated by considering the performance of a boost-type active power-factor corrector (APFC) that does not need to sense the input voltage. Theoretical and experimental results confirm the validity of the approach and demonstrate that the proposed method can be useful in the design of robust APFC with low total harmonic distortion. The indirect control method investigated in this paper is also compared to the classical direct APFC control method, pointing to the differences between the two.

Generic operational characteristics of piezoelectric transformers

The universal attributes of piezoelectric transformers (PT) were derived by an approximate analysis that yielded closed form equations relating the normalized load resistance to the voltage gain, output power per unit and efficiency. Based on the results of the study, a calculation procedure is developed for specifying a PT for any given application and is demonstrated by considering the design of a fluorescent lamp driver. It is suggested that the closed form formulae, developed in this study, could be invaluable when studying, specifying and designing practical PTs applications.

An RC load model of parallel and series-parallel resonant DC-DC converters with capacitive output filter

A novel analytical methodology is proposed and applied to investigate the steady-state processes in voltage-fed parallel and series-parallel resonant DC-DC power converters with a capacitive output filter. In this methodology, the rectifier, output capacitor and load are replaced by an equivalent circuit which includes a capacitor and resistor connected in parallel. Excellent agreement was obtained when comparing numerical values calculated by the proposed model to cycle-by-cycle SPICE simulation and to the numerical results of earlier studies.

Generic and unified model of Switched Capacitor Converters

A generic modeling methodology that analyzes the losses in Switched Capacitors Converters (SCC) was developed and verified by simulation and experiments. The proposed analytical approach is unified, covering both hard and soft switched SCC topologies. The major advantage of the proposed model is that it expresses the losses as a function of the currents passing through each flying capacitor. Since these currents are linearly proportional to the output current, the model is also applicable to SCC with multiple capacitors. The proposed model provides an insight into the expected losses in SCC and the effects of their operational conditions such as duty cycle. As such, the model can help in the optimization of SCC systems and their control to achieve desired regulations.

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

A novel topology, current-sourcing push-pull parallel-resonance inverter (CS-PPRI), is 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.<<ETX>>

Average simulation of PWM converters by direct implementation of behavioral relationships

Average modeling of PWM power converters is reexamined in the light of the behavioral dependent sources now included in modern versions of electronic circuit simulators. A topology independent behavioral model is developed to emulate the operation of PWM converters in voltage and current modes, for continuous and discontinuous inductor current cases. It is shown that, in general, the operation of the switching part involves three behavioral blocks, i.e., the generic switched inductor model (GSIM), the duty cycle generator (DCG), and the inductor current generator (ICG). Explicit expressions and equivalent circuits are developed for all possible modes of operation.<<ETX>>

A unified SPICE compatible average model of PWM converters

A simple, unified, and topology-independent model of basic pulse-width modulated (PWM) power converters is developed using the switched inductor approach presented by S. Ben-Yaakov (1989). The model is compatible with SPICE or other similar general-purpose electronic circuit simulators. It can be used to simulate DC, small signal, and transient behavior of PWM converters operating in both discontinuous conduction mode (DCM) and continuous conduction mode (CCM). During simulation, the model automatically follows the CCM and DCM operation, with fewer convergence problems compared to previous simulation models. An effective measurement technique using the HP3562A dynamic signal analyzer (DSA) is presented and applied to compare simulation runs with experimental data. The two were found to be in good agreement. >

The carbonate system in hypersaline solutions: dead sea brines

Abstract Various investigators reported a decrease in pH as seawater is concentrated. A similar phenomenon was reported for Dead Sea waters which are about ten times more saline than seawater. The reasons for the low pH values of Dead Sea waters (pH 5.9–6.5), which precipitate CaCO 3 , were investigated by determining the apparent dissociation constants of carbonic acid in these brines. A new method, based on alkalinity titration and least-squares fitting, was used to estimate the proton activity coefficient (γ H +) and the first and second dissociation constants of carbonic acid ( K 1 ′, K 2 ′) in natural and artificial Dead Sea waters. It was found that as the salt content increases, p K ′ 1 and p K ′ 2 values progressively decrease whereas γ H + sharply increase. At the highest salinity investigated (TDS = 330 gl −1 ) γ H + p K ′ 1 and p K ′ 2 values are 24.5, 5.09 and 6.23, respectively, as compared to about 0.8, 5.9, 9.1 respectively for normal seawater (19‰ chlorinity) at the same temperature (30°C). The implication of the results of this study regarding solubility of CaCO 3 and the general behavior of the carbonate system in hypersaline solutions is discussed.

A MHz electronic ballast for automotive-type HID lamps

The compatibility of the current sourcing push pull resonant inverter (CS-PPRI) with the driving requirements of HID lamps designated for automotive headlight applications was investigated theoretically, by simulation and experimentally. The study reveals that a based ballast (CS-PPRI) complies with the automotive requirement of very fast warm up. The experimental ballast was run under zero voltage switching (ZVS) at a nominal switching frequency of 1.29 MHz while the pre-ignition switching frequency was 124 kHz. Warm up time to 80% after cold ignition was about 10 seconds.

PWM converters with resistive input

An average modeling methodology is proposed for deriving pulsewidth modulation (PWM) programming rules that cause DC-DC converters to look resistive at the input terminals. The method can be useful in the design of active power factor correctors that do not need to sense the input voltage.