Search

In this work, the three-phase rectifier with a new connection is presented. The use of the Scott transformer makes a split dc-bus voltage possible and the rectifier operates with unity power factor. Using only two active switches, the rectifier is able to generate symmetrical currents in the line and a balanced split dc-bus output voltage, which is necessary in several applications. Pulse width modulation and instantaneous average current control are used. There are two voltage controls that regulate the output voltage and the split dc-bus voltage. Complete simulation results under closed loop operation are given, as well as results of an experimental setup. Index Terms--AC-DC converters, power factor corrector (PFC) converters, power supplies, pulse width modulated (PWM), split dc-bus voltage, three-phase rectifier.

In this paper, a novel four-level inverter will be presented and analyzed. The proposed inverter topology, which is composed of a conventional two-level and a three-level neutral-point clamped (NPC) inverter, is suitable for high-voltage and high-power applications. The proposed inverter, when it is compared with the conventional four-level NPC pulsewidth modulation inverter, exhibits the following advantages: a) ability of changing the power losses distribution profile among the devices by selecting a suitable switching strategy; b) reduction of total inverter power semiconductor device losses; c) ability of bidirectional operation for all power semiconductor switches; and d) easy implementation using existing power semiconductor modules. The effect of conduction and switching losses profiles of the proposed inverter for different switching strategies is examined under different loads, power factors, and modulation indices. The dc-link capacitors voltages are effectively balanced via a proposed self-voltage balancing topology, without the need of isolated dc voltage sources or additional voltage stabilizing circuits. Finally, the theoretical results are confirmed by simulation and experimental results. Index Terms--DC-Link capacitor voltage balance, multilevel voltage source inverter (VSI), semiconductor device power losses, sinusoidal pulsewidth modulation (SPWM).

Passive and active filters are reviewed to define technology requirements for maintaining the impedance seen by the microprocessor below 1 m[OMEGA] (100 mV transient excursion on top of a 0.8-V, 120-A bus) in the gigahertz frequency range. The designs of these filters need to be coordinated so that the active filter does not have to carry the bulk of the real power or a significant amount of reactive power. Parasitic inductances need to be kept below a picohenry and amplifiers need to have bandwidth approaching a gigahertz to keep the loss below 10% of the real power. Index Terms--Active clamp, hybrid filter, linear active filter (LAF), linear regulator, microprocessor power delivery, passive filter, switched capacitor active filter, transient absorber, transient suppressor, voltage regulator module (VRM).

A novel concept for wireless power transmission using inductive coupling is proposed to transmit power homogeneously over a large working area. This concept includes a specially designed winding group on the transmitting side to generate a traveling magnetic field, which causes an alternating magnetic flux through a receiving coil that is located in this field and, therefore, induces a voltage in the coil. The prototype system provides an effective working area of 180 x 220 mm for one or more power receivers that is 4.0 mm thick and 11.5 mm in diameter. Each receiver receives a constant power of about 330 mW at 3.1 [+ or -] 0.4 V dc operating voltage throughout the working area. A possible application of this concept is the powering of untethered microrobots. Index Terms--Magnetic field, mobile power supplies, mobile robots, power systems, power transmission.

This letter describes a digital pulsewidth modulator that enables the generation of a large, adjustable number of pulsewidth modulated (PWM) outputs of programmable duty cycle and dead time, yet requiring just a small, fixed architecture. The design achieves a resolution of 255 ps using a composite PWM strategy that also minimizes clock frequency and area. It provides a practical solution to the problem of efficiently generating multiple high-resolution gate-drive signals and is particularly suited to the next generation of synchronously switched multiphase voltage regulator modules. Index Terms--DC-DC power conversion, digital control, field-programmable gate arrays (FPGA), switched-mode power supplies.

This paper presents the analysis of open-loop power-stage dynamics relevant to current-mode control for a boost pulsewidth-modulated (PWM) dc-dc converter operating in continuous-conduction mode (CCM). The transfer functions from input voltage to inductor current, from duty cycle to inductor current, and from output current to inductor current are derived. The delay from the MOSFET gate drive to the duty cycle is modeled using a first-order Pade approximation. The derivations are performed using an averaged linear small-signal circuit model of the boost converter for CCM. The transfer functions can be used in modeling the complete boost PWM converter when current-mode control is used. The theory was in excellent agreement with the experimental results, enforcing the validity of the transfer functions derived. Index Terms--Boost converter, continuous-conduction mode (CCM), current-mode control, delay, pulsewidth-modulated (PWM) power converters, small-signal transfer functions, switchmode power supply.

The performance evaluation of C[F.sub.4] decomposition efficiency using 2- and 4-MHz power supplies was carried out as a function of the power, the pressure, the flow rate, and the quantity of [O.sub.2] addition. When the 2- and 4-MHz power supplies were used, almost complete C[F.sub.4] removal was achieved at 2.0 and 3.0 kW, respectively, when the C[F.sub.4] flow rate was 0.20 normal liters per minute. The optimum [O.sub.2]/C[F.sub.4] ratio should be in the range of 1.0 ~ 1.25 in order to decompose C[F.sub.4] efficiently. The C[F.sub.4] decomposition efficiency using the 2-MHz power supply was significantly higher than that of the 4-MHz power supply under the same power, pressure, and flow rate. Significant amounts of byproducts such as CO[F.sub.2] and CO were identified by the Fourier Transform Infrared Spectrophotometer analysis in addition to C[O.sub.2]. Index Terms--C[F.sub.4], decomposition, inductively coupled plasma (ICP), perfluorocompounds (PFCs), power frequency.

The harmonics of the propulsion power supply system on the Taipei Mass Rapid Transit System (TMRTS) are characterized. This study applies a new measurement method based on the railway magnetic field measurement technique, to record the dc current harmonics of the TMRT system under various operating conditions. Analysis of the data obtained through these field measurements reveals the presence of both typical and atypical harmonics while the trains are running. The monitored information from the TMRTS during dynamic operation helps engineers (planners) to identify how many orders and levels of harmonics may be present. Index Terms--Harmonics, mass rapid transit system (MRTS), railway magnetic field, traction power system.

A personal rapid transit (PRT) system is a computer-controlled and lightweight railway vehicle using linear motors. The speeds of vehicles are controlled to be constant, and the distance between vehicles is also strictly controlled to be only 12 m at 40 km/h. Thus, the vehicle density of the PRT system is much higher than that of the mass railway train (MRT) system. Moreover, the required power of a PRT vehicle is much smaller than that of an MRT vehicle. Therefore, the methodology to allocate the position of power supplies for an MRT system is thought to be improper for a PRT system. This paper proposes a practical method that locates power supplies optimally for a PRT system to achieve a load power balance and a total power loss minimization. This method uses an iterative approach based on a new virtual isolation concept among power supplies. The effectiveness and feasibility of the proposed method is confirmed by simulation results and example studies. Index Terms--Iterative technique, personal rapid transit (PRT), PRT power system, traction power system.

Investigations of the requirements for high-voltage (HV) power supplies for zones within an electrostatic precipitator (ESP) were conducted with regard to the properties of different technologies for HV generation. The zones of an ESP show different electrical behavior and efficiency. This is a result of: 1) the different dust loads of the zones; 2) the particle size and properties; and 3) the possibility of charging the particles in the entire zone using suitable technology. An overview of common and new topologies of HV supplies and their typical properties is given. It is shown how these properties can be used to match the requirements of the different zones of an ESP regarding the actual operating conditions. Large particles and high dust loads can be addressed effectively using high-frequency dc power supplies. Fine particles, however, can be separated even more efficiently by pulsed power supplies. Additionally, the power consumption of different HV sources has been investigated in relation to the separation efficiency. Experimental results were obtained on an industrial ESP containing 3 zones in a sinter plant and on a large scale precipitator in a fossil power plant, containing 30 zones. It was shown that a high frequency IGBT inverter combined with a microsecond-pulsed power supply significantly improved the overall performance of the precipitator. Index Terms--Back corona, high-frequency power supply, power supplies for electrostatic precipitators (ESPs), pulsed power supply, short pulse.

In this brief, a peak-current-mode control based on the closed-form loop compensator design is proposed to integrate with a current-sharing circuit to automatically and smoothly adjust the trim signal in conventional dc/dc power supplies. As a result, for single-wire autonomous current sharing of paralleled dc power supplies, not only the minor alarm of the current limit can be avoided, but also the imbalance in current distribution during the transient state can be reduced. To demonstrate the effectiveness of the proposed method, an example of three 150-W parallel modules is considered. Experimental results are also presented to illustrate the proposed method. Index Terms--Current share, multimodule, single wire.

In this paper, a novel evolutionary algorithm-based approach to optimal design of multimachine power-system stabilizers (PSSs) is proposed. The proposed approach employs a particle-swarm-optimization (PSO) technique to search for optimal settings of PSS parameters. Two eigenvalue-based objective functions to enhance system damping of electromechanical modes are considered. The robustness of the proposed approach to the initial guess is demonstrated. The performance of the proposed PSO-based PSS (PSOPSS) under different disturbances, loading conditions, and system configurations is tested and examined for different multimachine power systems. Eigenvalue analysis and nonlinear simulation results show the effectiveness of the proposed PSOPSSs to damp out the local and interarea modes of oscillations and work effectively over a wide range of loading conditions and system configurations. In addition, the potential and superiority of the proposed approach over the conventional approaches is demonstrated. Index Terms--Dynamic stability, particle swarm optimization, PSS design.

This is the second of a two-part series on communications over the European 240 V domestic powerline, in the frequencies identified by the CENELEC European mains signalling standard, suitable for low-cost equipment in applications requiring data rates of no more than hundreds of bits per second (b/s). To minimize costs, narrow-band modulation techniques are considered. The series of two papers identifies the key impairments introduced by the channel, proposes a novel model structure to simulate them, and describes modulation techniques. The first paper describes the principal linear impairments; cyclic noise power variation and linear signal attenuation. The present paper describes nonlinear multiplicative signal fading and shows how orthogonal frequency division modulation (OFDM) can be used to overcome these impairments. Index Terms--Mains communications, powerline carrier, powerline communications, remote meter reading.

Four new topologies of active input current shapers (AICSs) for converters with symmetrically driven transformers (such as half-bridge, full-bridge and push-pull) have recently been proposed. This paper analyzes the extension of the use of, these new AICSs topologies to converters with asymmetrically driven transformers. Using some of these topologies, the size of AICS inductors can be reduced and even integrated in a single magnetic core. As in the case of other converters with AICS circuit, the new topologies allow line current harmonics to be reduced and thereby to comply with the IEC 1000-3-2 specifications, whilst maintaining all the features of standard dc-to-dc converters (e.g., fast transient response). Finally, the proposed topologies have been experimentally tested. Index Terms--IEC 1000-3-2 regulations, power factor correction, switching mode power supplies.

Current-limiting fuses (CLFs) are commonly used for unit substation primary protection. Simultaneously, surge arresters are also provided on the primary side of the transformers, more so for the dry-type transformers. The arc voltages generated by CLFs will store energy in the inductive elements of a distribution system. This stored energy divides between the CLF and surge arrester, and the surge arrester may operate. This paper outlines a procedure to calculate the energy diverted to the surge arresters and shows that, in some cases, surge arresters may fail on operation of the CLFs. Guidelines are developed for selection and application of the surge arresters at 13.8-, 4.16-, and 2.4-kV voltage levels. Index Terms--Coordination, current-limiting fuses, surge arresters.

An AC/DC converter that relies on a parallel-connected power MOSFET (metal-oxide semiconductor field-effect transistor) as a switching element is being researched as part of an effort to develop a power supply for a nuclear fusion experimental machine.

This paper presents the first reported final results of a benchmarking project 'StatPEP' which investigated the Status of Power Electronic Packaging used in commercial dc/dc and ac/dc switch mode power supplies. The methodology of the project is first described. Some of the salient results of a comprehensive benchmarking of dc/dc converters (rated power of 100 W) and ac/dc converters (rated power up to 576 W) are presented. Examples for figures-of-merit are presented. The results of the investigation are presented in a generic form, which does not identify individual products. A comparison of the performance of the units shows that the measured power density of the ac/dc units is approximately 10% that of the dc/dc while the thermal density based on footprint is 50%. Also the switching frequency of the ac/dc is 50% that of the dc/dc's. Some of the reasons for these differences are discussed. Index Terms--Benchmarking, packaging, power conversion.

Design rules are discussed, for SiC Schottky diodes that rely on field-plate edge termination. Use of the most suitable field-plate edge termination can strengthen the reverse breakdown voltage of a SiC Schottky diode by a factor of two.

Design and fabrication of a high-Tc superconducting (HTSC) power supply with Bi-2223 pancake load is described. Experimental and theoretical results are compared.

This paper discusses the development of a simulation model to study the propagation of partial discharge (PD) pulses of transformers in a 500 kV substation. The results will be used to design an on-line PD monitoring system for transformers. The impedance matrix of a 500 kV, single-phase transformer is computed based on geometry data and its external coupling network (often referred to as coupling impedance) is calculated with electromagnetic transients program (EMTP). It was found that the frequency characteristic of the coupling network is complex and that the traditional lumped coupling capacitance representation is only feasible at

Adjustable - speed drive (ASD) ride-through issues have caused increased concerns due to the susceptibility of ASD's to power disturbances, and the costly results of process disruptions. These losses can be avoided for critical production processes by using ASD's with ride-through capabilities. This paper assesses industrial ride-through requirements through power quality surveys and the results of an ASD ride-through questionnaire conducted by the authors. ASD ride-through alternatives are evaluated based on design, implementation, and cost considerations, in order to determine the most suitable solutions for various kilovoltampere ratings and time duration requirements. Index Terms - Adjustable-speed drive, drives, energy storage, process disruptions, ride-through, tripping.

This paper reports on an experimental and theoretical work about simulation of high-frequency power transformers used in switched-mode power supplies (SMPS's). The primary scope of this activity is to characterize a comprehensive transformer model for use in the final stages of the design process of an SMPS when an accurate study of the switching waveforms is an important requisite. The model should allow the designer to compare different core and winding arrangements without needing massive breadbording. Comparison between simulations and experimental results allowed improvements to be made to a transformer model developed and presented in a previous paper. This paper also investigates the real benefits of using a complex model in place of a simpler one, weighting them up against the unavoidable increase in central processing unit (CPU) time. Then simulations using a simplified model are presented, and the pros and cons are analyzed. Index Terms - Modeling, simulation, SPICE, transformer.

Feedback control system was constructed, in which the intensity of the magnetic field applied to the laser medium varied automatically in response to the laser power fluctuation, and used to demonstrate the output power stabilization for a chemical oxygen-iodine laser. A theoretical analysis of the input/output characteristics of the feedback system was performed and was observed to be in agreement with experimental results. The response time of the system was also found to be as short as 1 ms limited by the applied voltage of the electromagnet.

A hierarchical power supply distribution model was developed for analyzing full-chip switching noise. The model integrates the on-chip power bus model and the macro-based switching circuit model to analyze the resistive IR drop, inductive delta-I noise and power supply noise for high-performance very large scale integration design. The method was found to be effective for identifying sensitive spots on the chip and for optimizing design variables to minimize noise.

This paper describes the circuit and operation of a photomultiplier high-voltage power supply incorporating a ceramic transformer instead of a conventional magnetic one. The ceramic transformer, being constructed from a ceramic bar, utilizes the piezoelectric effect to generate high voltage. As no magnetic material is present, no leakage of magnetic flux occurs such that the power supply can be operated under a strong magnetic field. The transformer shows a sharp resonance, after which voltage amplification is dependent on frequency. Transformer output is stabilized by feedback utilizing frequency dependence, i.e., after rectification, the output high voltage is fed back to a voltage-controlled oscillator that adjusts the oscillation frequency according to the output voltage of an error amplifier that compares the output high voltage with a reference voltage. This photomultiplier high-voltage power supply provides high voltage from 1500 to 2500 V at a 20-M[Omega] load, where the load is a breeder of the photomultiplier. The magnitude of voltage ripples is at a prescribed level when the load is 20 M[Omega]. Ripple magnitude is proportional to load current. Voltage ripples limit the load current to the photomultiplier.

Typical low drop-out (LDO) regulator architectures suffer from an inherent load regulation performance limitation. This limitation manifests itself through limited dc open-loop gain, and results from stringent closed-loop bandwidth requirements. The frequency response of the system is highly sensitive to the loading conditions, thereby making proper compensation a laborious endeavor. This paper discusses and addresses the limitation on regulating performance imposed by frequency compensation. Several LDO circuit topologies are subsequently developed to this end. They enhance load regulation performance by relaxing the dc open-loop gain restrictions. The circuit structures essentially alter the frequency response of the system via the error amplifier. A low drop-out regulator adopting an embodiment of the proposed technique was fabricated in the MOSIS 2-[[micro]meter] process technology. The system, designed for an output capacitor of 4.7[[micro]farad], was stable with an equivalent series resistance (ESR) ranging from 0 to 12 [ohms], bypass capacitors ranging from 0 to 2.2 [[micro]farad], and a load current ranging from 0 to 50 mA. Index Terms - Low drop-out, power IC, regulator, reference.

This work presents a novel dc-dc converter, whose significant advantages are the single power switch, single-input inductor, purely capacitive output filter, isolation, low current ripple through the output capacitor, and operation at constant frequency in a conventional pulse-width-modulation scheme. The new converter operates over a wide input-voltage range and can be employed in power factor correction and multiple-output power supplies. Theoretical analysis is presented along with experimental results taken from a laboratory prototype rated at 300 W/50 kHz. Index Terms - DC-DC converters, flyback converters, high frequency, power supplies.

The design and implementation of a robust, scalable, and modular optical power supply spot-array generator for a modulator-based free-space optical backplane demonstrator is presented. Four arrays of 8 x 4 spots with 6.47-[[micro]meter] radii (at 1/[e.sup.2] points) pitched at 125 [[micro]meter] in the vertical direction and 250 [[micro]meter] in the horizontal were required to provide the light for the optical interconnect. Tight system tolerances demanded careful optical design, robust optomechanics, and effective alignment techniques. Issues such as spot-array generation, polarization, power efficiency, and power uniformity are discussed. Characterization results are presented. Key words: Optical power supply, spot-array generator, modulators, self-electro-optic devices, optomechanics, optical design, alignment, module, characterization.

We present a new pass-transistor adiabatic logic (PAL) that operates from a single power-clock supply and outperforms the previously reported adiabatic logic techniques in terms of its energy use. PAL is a dual-rail logic with relatively low gate complexity: a PAL gate consists of true and complementary NMOS functional blocks, and a pair of cross-coupled PMOS devices. In simulation tests using a standard 1.2 [Mu] CMOS technology, the circuit has been found to operate up to 160 MHz clock frequency and down to 1.5 V peak-to-peak sinusoidal power-clock supply. Operation of a 1600-stage PAL shift register fabricated in the 1.2 [Mu] CMOS technology has been experimentally verified. Index Terms - Adiabatic computing, energy recovery, low power logic.

Sepic and Cuk converters working as power factor preregulators (PFP) in discontinuous conduction mode (DCM) present the following desirable characteristics for a PFP: 1) the converter works as a voltage follower (no current loop is needed); 2) theoretical power factor is unity; and 3) the input current ripple is defined at the design stage. Besides, input-output galvanic isolation is easily obtained. This paper analyzes the operation of both converters as DCM-PFP. Design equations are derived, as well as a small-signal model to aid the control loop design. Both simulation and experimental results are presented that are in agreement with the theoretical analysis and complement the work. Index Terms - AC-DC power conversion, filtering, power supplies.

Distributed power-supply systems are an attractive solution to meeting the requirements (redundancy, modularity, battery backup, etc.) for the next generation of power-supply systems. In addition, the normalization regarding power factor and total harmonic distortion (THD) makes it necessary to include the power-factor correction in the input stage in those architectures. This paper presents a novel approach of an integrated battery charger/discharger which offers power-factor correction and battery galvanic isolation in a simple structure. Placing the battery in the primary side overcomes the need of galvanic isolation integration in each one of the dc/dc on-board converters when this topology is used as part of a distributed power-supply system. Index Terms - AC-DC power conversion, batteries, communication system power supplies, dc power systems, reactive power correction, switched-mode power supplies, pulsewidth-modulated power converters.

Phase-controlled thyristor rectifiers are still the preferred choice in high-power ac/dc converters. This paper shows that their steady-state and dynamic performance can be greatly enhanced for applications requiring high-precision fast-response performance by means of a hybrid structure using a shunt pulse-width modulation (PWM) active filter. In this hybrid structure, the rectifier is designed to handle the bulk of the output power, whereas the PWM converter is only used for harmonic cancellation and current-error compensation under transient conditions. This results in a small power rating for the shunt-active filter. A suitable control scheme is proposed and implemented in this paper for the rectifier and PWM converter. Experimental results are provided to validate the proposed concept. Index Terms - Active filters, power supplies, pulse-width modulation.

This paper presents a technique to generate a complete family of two-switch pulsewidth-modulated (PWM) with active clamping dc/dc converters, featuring soft commutation of the semiconductors at zero-voltage (ZVS). The main purpose of this technique is to integrate these converters under a same theoretical principle to derive the topologies in a comprehensive form and generate new circuits. All the converters have the advantage of soft commutation (ZVS) with minimum switch voltage stress due to the clamping action. Besides operating at constant frequency and with reduced commutation losses, these converters have output characteristics similar to the PWM hard-switching counterpart, which means that there is no circulating reactive energy that would cause large conduction losses. Principle of operation, theoretical analysis, simulation and experimental results of one particular converter taken as an example, are provided in this paper. Index Terms - Active clamping, dc-to-dc converters, power supplies, soft commutation.

Reference/modulating waveform continuity is not a necessary condition for the implementation of switching patterns for three-phase pulse-width modulated (PWM) converters if the load or the source are Y-connected. This is based on the fact that the converter phase-voltages do not need to be sinusoidal and switching pattern discontinuities - 'dead-bands' - do not degrade the quality of output/input voltage/current waveforms by introducing low-order harmonics if certain parameters are optimized. This paper discusses general characteristics of various discontinuous switching patterns for PWM converters and shows that they can yield better performance than their continuous counterparts in some operating regions. Performance is defined as harmonic distortion normalized with respect to effective switching frequency and serves as a measure of comparison with continuous PWM techniques. The applications considered include general purpose and application specific solid-state power supplies using voltage source inverters and PWM rectifiers. Theoretical considerations are verified on an experimental unit.

This paper presents the analysis and design of a multiple feedback loop control scheme for single-phase voltage-source uninterruptible power supply (UPS) inverters with an L-C filter. The control scheme is based on sensing the current in the capacitor of the load filter and using it in an inner feedback loop. An outer voltage feedback loop is also incorporated to ensure that the load voltage is sinusoidal and well regulated. A general state-space averaged model of the UPS system is first derived and used to establish the steady-steady quiescent point. A linearized small signal dynamic model is then developed from the system general model using perturbation and small-signal approximation. The linearized system model is employed to examine the incremental dynamics of the power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS system. Experimental verification of a laboratory model of the UPS system under the proposed closed-loop operation is provided for both linear and nonlinear loads. It is shown that the control scheme offers improved performance measures over existing schemes. It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of filter parameters. Furthermore, the scheme has excellent dynamic response and high voltage utilization of the dc source.

When multiple dc/dc converters are operated from a dc bus with a nonzero source impedance, undesirable interactious can occur between an individual regulator and the input impedance of the other regulators on the bus. Consequently, criteria for input filter design in the presence of a significant source impedance are developed, which, when used in conjunction with already-known input filter criteria, permit the input filter to be designed so that each regulator operates reliably. Proper filter design tends to decouple the negative regulator impedances from the bus, leaving only the passive input filter impedances to affect the other converters. These filter impedances appear in parallel with the source impedance and reduce the overall source impedance. Hence the use of multiple modules on the same bus actually improves the performance of the individual regulators. An example, the buck current mode controlled converter, is examined in detail. Extensive experimental evidence is presented to verify the analytical results.

The reduction of the supply voltage forces to develop system and circuit solutions able to achieve the same performance previously obtained with higher supply voltage. In this paper, a second-order low-pass continuous-time filter operating at a 3 V power supply is presented. The prototype filter is implemented using a highly linear pseudo-differential transconductor. The input common-mode signal is canceled at the transconductor level using a feed-forward path. The output common mode voltage is controlled at the filter level using lossy integrators. A prototype cell has been realized in 1.2 [[micro]meter]V BiCMOS technology. The pole frequency can be tuned in the range 12-55 MHz. A THD of -40 dB is achieved for signals up to 1 [V.sub.pp] at 10 MHz. The dynamic range is approximately 60 dB.

A hydrogenated amorphous silicon (a-Si:H) solar cell array that is designed as an on-board power source for electrostatic microelectromechanical systems (MEMS) is presented. A single cell consists of a triple layer of p-i-n/p-i-n/p-i-n a-Si:H and produces an open circuit voltage ([V.sub.oc]) of 1.8[similar to]2.3 V, a short circuit current density ([J.sub.sc) of 2.8 mA/[cm.sup.2], and fill factor (FF) of 0.495. A series interconnected array of 100 single solar cells (total array area of 1 [cm.sup.2]) is fabricated in an integrated fashion and produces an array [V.sub.oc] of 150 V, and array short circuit current ([I.sub.sc]) of 2.8 [[micro]ampere] under Air Mass (AM) 1.5 illumination. To demonstrate the usefulness of this solar cell array as an on-board power source for electrostatically driven micromachined devices, it has been packaged with a movable micromachined silicon (Si) mirror in a hybrid manner. The movable Si mirror is directly driven by the cell array electrical output, and the motion of the mirror plate has been observed reproducibly. Variation of light intensity and/or number of illuminated cells produces different values of array [V.sub.oc], thus enabling control of the deflection of the Si mirror by variation of incident light intensity.

An assessment of the trade-offs between total electrical energy, the pulse shape which is delivered to the gun and the chemical energy is presented for a future medium/large calibre (circa 130 mm) ETC indirect fire gun system. In particular, this paper discusses the implications on total gun system volume i.e. including the electrical power supply and pulse conditioning system. The study considered electrical requirements of up to 25 MJ per shot. The potential performance improvements, compared with a similar sized chemical gun system, are also presented. The FNGUN finite difference based internal ballistics code has been used to simulate the likely trade-offs between electrical input energy, chemical energy and gun performance. This has shown that there is a dependence of the overall system performance on such parameters as: * the anticipated electrical behaviour of the plasma * the shape of the electrical pulse supplied to the gun * the internal ballistics of the gun. In particular it has been found that there is potentially a practical limit to the extent of pulse forming which is worth carrying out before parasitic losses in the pulse conditioning system become too great. Consequently, it is concluded that while some pulse shaping is necessary to meet the requirements of the internal ballistics, i.e. power increasing with time, there is little benefit from further optimisation of the pulse shape.

The stacked power system combines series and parallel connections of multimodule power supplies to produce several low voltage outputs at high current levels. The system could generate ultra low voltage outputs with higher efficiencies than conventional centralized or distributed approaches, using standard single-output converters. This paper presents the architecture of the stacked power system and establishes a design procedure for the system.

The effect of frequency modulation on power supply EMI noise is investigated. Significant reduction of emission is possible with this scheme.