Showing papers on "Filter capacitor published in 1994"

Hybrid metal/metal oxide electrodes for ferroelectric capacitors

Abstract: Ferroelectric capacitors with hybrid electrodes including both a conducting oxide and a noble metal may be used to achieve devices having improved performance over capacitors with either platinum or ruthenium oxide electrodes. These hybrid electrode structures can improve capacitor performance both in terms of fatigue and leakage current. Accordingly, these ferroelectric capacitors with hybrid electrodes can be used as elements of an integrated circuit such as a non-volatile memory or dynamic random access memory.

Multiple feedback loop control strategy for single-phase voltage-source UPS inverter

Abstract: This paper investigates the performance of multiple feedback loop control strategy for single-phase voltage-source UPS inverter with an L-C filter. In order to select appropriate feedback variables and assess the stability of the closed loop operation of the overall system, the power circuit (inverter and filter plus load) incremental dynamics is investigated using the state-space averaging technique and root locus method. The results of the stability analysis show that a control scheme which employs the filter capacitor current in an inner feedback loop and the load voltage in an outer voltage control loop results in successful operation of the UPS system. Computer simulation results of a single-phase voltage-source half-bridge UPS inverter with a second order filter and R-L load is presented to demonstrate the performance of the proposed control scheme. Experimental verification of a laboratory model of the UPS system is also provided for both linear and nonlinear loads so as to verify the predicted performance of the system. 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 fast dynamic response and high voltage utilization of the DC source. >

A built-in-input filter forward converter

Abstract: Employing the transformer leakage inductance and two cross-coupled capacitors, a built-in input filter forward converter (BIFFC) configuration is proposed to shape the input current waveform to a nonpulsating fashion. Consequently the ripple and harmonic component of the input current can be significantly reduced without adding a large input filter. In this paper, the circuit operation is analyzed by using the PSPICE software and an experimental circuit on a 300 kHz, 50 W converter was breadboarded for performance evaluation and comparison. >

Variable-capacitance power supply apparatus

Abstract: A variable-capacitance power supply apparatus has an inexpensive structure for variably supplying a desired high power to a load by selecting an appropriate total capacitance for storing charge. A number "n" (an arbitrary integer) of series-coupled capacitors each having capacitance C are independently charged to produce an appropriate output voltage. The total capacitance Cs of the series-coupled capacitors is obtained as Cs=C/n. The total charge Q stored in the series-coupled capacitors is proportional to the total capacitance Cs. The series-coupled capacitors are selectively charged to produce an appropriate output voltage and the desired high power to be supplied to the load.

Voltage multiplier using switched capacitance technique

Abstract: A voltage multiplier is constructed using a series combination of capacitors and an associated switching circuit which provides for charging each capacitor in the series by sequentially connecting each capacitor to a d.c. input voltage. The number of capacitors in the series combination is selectable by the user. The d.c. input voltage of N volts is converted to an a.c. output voltage of peak-to-peak N+1 times the input voltage developed off a tap in the series combination using the pattern of sequential switching. The choice of tap determines the relative offset voltage of the output waveform desired. The relative charging times of the capacitors are chosen so that the output waveform resembles a sine wave to minimize the production of harmonics.

Method for screening early failure of ceramic capacitor

Abstract: A method of screening ceramic capacitors. The method includes the steps of: charging the ceramic capacitors by applying a constant d.c. voltage which is larger than the rated voltage and smaller than the breakdown voltage; and leaving the charged ceramic capacitor in a temperature around the maximum working temperature for a specific period of time with both terminals of each ceramic capacitor opened electrically; and eliminating defective capacitors whose residual voltage values are smaller than a specific voltage value.

Tunable filter circuit and method therefor

Abstract: A tunable filter circuit (340) has a ceramic block forming a portion thereof. Transmission lines (352', 372', 392', 412') are formed of resonating cavities which extend through the ceramic block, and variable capacitors (364, 384, 404, 424) capacitively load the transmission lines (352', 372', 392', 412'). By varying the capacitance of the variable capacitors (364, 384, 404, 424), the filter characteristics of the filter circuit comprised of the ceramic block and the variable capacitors is varied. The tunable filter circuit (340) may, for example, comprise a portion of a cellular radiotelephone operative in a TDMA communication scheme.

Multilevel inverter having voltage dividing capacitors distributed across multiple arms

Abstract: The power converter of the invention relates to a small-sized highly efficient power converter for generating an a.c. voltage output of multiple levels with less harmonic content. In the power converter, a d.c. voltage source is separated into plural sections by series connected voltage dividing capacitors and multiple levels of a.c. output voltage are obtained from the divided d.c. voltage by on-off control of switching devices. The power converter has plural sets of the voltage dividing capacitors disposed separately adjacent to each switching devices, and series connection point of each set of the voltage dividing capacitors are connected to division points of the corresponding switching devices of each phase. The voltage dividing capacitors are connected with each other at their series connection points. Thereby, the arrangement makes wiring length short and equal between the switching devices and the voltage dividing capacitors for each phase and reduce a loss in the snubber circuit, resulting in an a.c. voltage output with less harmonic content.

Current clamped, PWM, quasi-resonant DC link series resonant converter

Abstract: This paper presents a new high frequency series resonant DC link topology derived by Y. Morai and T.A. Lipo (1988), wherein the resonant tank does not bring about peaky currents in any portion of the system. The characteristic overall-clamping mechanism permits lower-current-rating for the semiconductor devices, resonant capacitor and filter capacitors, easing the cost burden. Moreover, the values of the resonant inductor and the capacitor can be reduced substantially, limited only by the di/dt ratings of the devices, since the resonant current peaks, which would otherwise have risen to a higher value (tank storage energy burden) no longer appear in this configuration. In the paper, the converter is digitally simulated using "ACSL" and output performance is investigated. The voltage stresses across the auxiliary switches are estimated using the "SABER" simulator on a mono-phase model. PWM-capable other series resonant topologies are compared with the new topology for voltage stresses across the auxiliary switches using the SABER simulation code. >

Electronic ballast with high-frequency-aided power-factor-correction

Abstract: In a power-line-operated current-fed parallel-tuned electronic ballast, power-factor-correction and line current harmonics-reduction are attained by placing a high-frequency inductor as well as a high-frequency voltage source in series with the unfiltered DC output of a bridge rectifier connected with the power line voltage. The unfiltered DC output is then supplied to a filter capacitor through a phase-controlled field-effect transistor, thereby to provide a DC voltage of controllably constant magnitude to the ballast's inverter while at the same time drawing power from the power line with a power factor well over 90% and with a total harmonics content well under 20%. The AC voltage provided from the high-frequency voltage source, which has a peak-to-peak magnitude roughly equal to that of the power line voltage, is represented by a simple auxiliary winding on the ballast's main output transformer; which high-frequency voltage is used for pumping current from the power line, through the bridge rectifier, and to the filter capacitor. The inductance of the high-frequency inductor is determined by the frequency of the ballast's AC output voltage as well as by the maximum amount of power required from the power line.

Three-phase voltage-source UPS inverter with voltage-controlled current-regulated feedback control scheme

Abstract: This paper presents a novel control strategy for three-phase voltage-source UPS inverters with second order L-C filters. The control scheme is based on sensing the current in the filter capacitor and using it in an inner feedback loop. An outer capacitor voltage loop is also incorporated to ensure sinusoidal load voltage. A general model of the power circuit (inverter, filter, and load) is first established. Computer simulation results of the proposed three-phase voltage-source UPS system with an R-L load from "cold" start to full-load is then presented to demonstrate the suitability of the proposed control scheme for UPS applications. The dynamic response of the proposed scheme is investigated using rotating frame of reference and small signal approximation. A control loop regulator is then selected to enhance the dynamic response of the control scheme and achieve the desired performance of the UPS system. It is shown in the paper that the control scheme offers many advantages for UPS applications. 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. The scheme has fast dynamic response and provides high voltage utilization of the DC source. In addition, it provides peak current limiting capability and lends itself to both linear and nonlinear load applications. >

Capacitive transformer having a switch responsive to clock signals

Abstract: A transformer including two half capacitive transformers operating in antiphase. Each half capacitive transformer steps an input voltage down during one phase of a clock signal. Each half capacitive transformer uses a number of capacitors and switching circuitry controlled by a clock signal. According to whether the clock signal is active or inactive, the switching circuitry places the half capacitive transformer in one of two configurations. In a first embodiment, in one configuration the capacitors are coupled in parallel between the input voltage and the output port, while in the other configuration, the capacitors are coupled in series between the output port and ground. In an alternative embodiment of the half capacitive transformer, in one configuration the capacitors are coupled in series between the input voltage and the output port while in the other configuration the capacitors are coupled in parallel between the output port and ground. The step-down ratio of the transformer is related to the number of capacitors included in a half capacitive transformer and not to the values of the capacitors. The capacitive transformer may step up voltages by swapping the input and output ports.

Method and apparatus for power supply with gated charge filter

Abstract: A power supply circuit limits the voltage on a filter capacitor driven by rectified half-cycles of an input AC waveform. A FET switch in series with the current charging the filter capacitor is opened as soon as the charge on the filter capacitor is adequate. A voltage triggered latch circuit is responsive to the rectified AC input applied through a decoupling diode to the filter capacitor, and supplies a control signal to the FET switch. A further sensing circuit can monitor the current charging the filter capacitor, and can trigger the latch to open the FET switch as needed to limit initial in-rush current during the initial application of AC power. The decoupling diode decouples the rectified peaks provided by the rectifiers from the voltage on the filter capacitor. This allows the filter capacitor to charge whenever the rectified input has an instantaneous voltage greater than the capacitor's (and the FET switch is closed), but also allows the output waveform from the rectifier to fall to zero during the zero crossings of the input waveform. That in turn resets the latch, and the process of gating the charge to be accepted by the filter capacitor is then repeated during the next half-cycle of the input AC waveform.

Active discharge circuit for charged capacitors

Abstract: An active discharge circuit provides for the discharge of filter capacitors in a power supply in the absence of a.c. line power. A detector provides a signal responsive to the removal of the pulsating d.c. charging voltage from the capacitors and a switch responsive to the detector signal closes, coupling an energy dissipating element, in the form of a resistor or a transistor, across the filter capacitor to dissipate its stored energy.

Switching-mode, alternating current, wave replication system

Abstract: An inverter/converter power supply system that employs pulse-width modulation controlled by an absolute-value representation of a reference wave. A low-frequency wave, such as a 60 hertz sine wave, is precision-rectified which then is the reference input of a pulse-width modulation controller (PWM). The PWM then produces a high-frequency square-wave signal whose pulse width changes as the amplitude of the rectified reference wave changes. The high-frequency square-wave signal is further rectified at an inverter/converter transformer secondary, whose output is filtered through a low-pass filter that removes the high-frequency component while minimizing the stored charge in the filter capacitor(s) to an amount easily drained by a small constant-current load across it. Feedback from the constant-current load to the PWM further adjusts the pulse-width to compensate for load variations and circuit losses. A flip-flop matrix of transistors then converts the pulsating DC wave signal to an AC wave signal by inverting the polarity on every other half wave cycle.

Boost topology with two outputs for power factor correction application

Abstract: A split boost converter is disclosed herein, suitable for both single phase and three phase AC input applications. It provides two equal but unparallelable output voltages stored on two separate independent output capacitors. The implementation supports two modes of operation in which two power switches are operated simultaneously or alternately. Each mode maintains the advantage of a reduced boost inductor size. In the first mode the charging of the capacitors in parallel circuits and their discharge in a series connection substantially reduces ripple current in the inductor permitting the user of a smaller inductor. In the second mode the capacitors are charged and discharged in differing time intervals achieving a similar result. The circuit is operable with input voltages which must exceed the voltages of its two output capacitors.

Modelling and simulation of integral decoupling capacitors in single and multichip module electronics packaging

Abstract: In high-end packaging structures, switching currents of short pulse width and high clock rate generate significant Delta-I noise which can cause malfunctions of IC circuits. The trend of increasing packing density makes the integral decoupling capacitor preferable than the conventional discrete capacitor. Although integral decoupling capacitors have been proposed and already used in some packaging structures, their electrical performance has not been accurately modeled. This paper presents an efficient and accurate numerical technique for the simulation of Delta-I noise in multi-layer power and ground plane packaging structures containing integral decoupling capacitors. Various factors that determine the effectiveness of integral decoupling capacitors, such as their geometries and locations in packaging structures, are also studied. >

Charge stacking on-chip high-voltage generator and method

Abstract: A charge stacking, high voltage generating circuit is provided wherein a plurality of capacitors are charged in parallel and discharged in series through a single diode to an output terminal. A switching circuit is used to connect each of the capacitors in parallel between a first supply voltage and a second supply voltage during a first half clock cycle. This configuration allows the capacitors to charge during this first half clock cycle. During a second half clock cycle, the switching circuit connects the charged capacitors in series between the first supply voltage and the output terminal through a single diode. The series configuration of the capacitors is such that the voltage at the output terminal is approximately equal to the first supply voltage, plus the sum of the voltages of the charged capacitors, minus the threshold voltage drop across the series diode.

Electronic ballast with power-factor-correcting pre-converter

Abstract: In a power-line-operated current-fed parallel-tuned electronic ballast, power-factor-correction and harmonics-reduction are attained by placing a high-frequency inductor as well as a high-frequeny voltage source in series with the DC output of a bridge rectifier connected with the power line voltage. The DC output is then supplied to a filter capacitor through a high-speed diode, thereby to provide a DC voltage of substantially constant magnitude to the ballast's inverter while at the same time drawing power from the power line with a power factor well over 90% and with a total harmonics content well under 20%. The AC voltage provided from the high-frequency voltage source, which has a peak-to-peak magnitude essentially equal to that of the power line voltage, is represented by a simple auxiliary winding on the ballast's main output transformer. The inductance of the high-frequency inductor is determined by the frequency of the ballast's AC output voltage as well as by the amount of power drawn from the power line.

An on-line operated near unity power factor PWM rectifier with minimum control requirements

Abstract: Most PWM rectifiers use online PWM patterns which results in slow transient response. Damping resistors must be provided to avoid amplification of harmonics and current oscillations, especially during transient conditions. This results in reduced efficiency. In this paper, a current-source type PWM rectifier with online pattern generation and inherent pattern synchronization with the AC mains is proposed. The voltages across the input filter capacitors are chosen as the modulating signals. This results in a very fast starting and a much improved transient response. Also, the need of the damping resistors is eliminated due to the effective damping provided through the modulating of the capacitor voltages. Moreover, an additional phase-shifting circuit is added to the control scheme to achieve near unity power factor independent of the load variations. The paper includes analysis, design guidelines and experimental results on a 1 kVA laboratory prototype to confirm the theoretical considerations. >

The analyses of ZVS turn-off loss and the new snubber circuit for the ARCP inverter

Abstract: This paper indicates two problems with the auxiliary resonant commutated pole (ARCP) inverter and proposes solutions of these problems. One of the problems is the increase of the turn-off losses of the main switches due to a lead inductance. Each of the resonant capacitors are connected closely with the main switches in the ARCP inverter. However, as the wire that connects DC capacitors with the main switches acts as a reactive component, called the "lead inductance", this causes imbalance between the currents flowing through the capacitors. Consequently, the turn-off losses of the main switches increase. The other problem is the surge voltage induced in the diodes of the auxiliary commutation circuit. As these diodes are connected in series with the resonant inductor, high surge voltages are induced even though their recovery currents are small. This paper proposes analyses of these turn-off loss considering the effect of the lead inductance as well as a new snubber circuit for suppressing the surge voltages across the diodes in the auxiliary commutation circuit. The turn-off losses evaluated by the analytical equations agree well with experimental results, and the effects of the new snubber circuit are confirmed by these experiments. >

Dc-dc converter and computer using it

Abstract: PURPOSE:To reduce a switching loss by a method wherein, when a switching element is turned off, a snubber capacitor is connected in parallel with the switching element and a capacitor is connected in series with the snubber capacitor in such a way that individual electrodes are of an additive polarity. CONSTITUTION:Single-chip forward converters 34-1, 34-2 which supply electric power to a load 33 from a transformer are connected to capacitors 4-1, 4-2. Then, in the converters 34-1, 34-2, snubber capacitors 5-1,to 5-4 are connected in parallel with the switching elements 5-1 to 5-4 when the switching elements 5-1 to 5-4 are turned off, and the capacitors 4-1, 4-2 are connected in series with the snubber capacitors 7-1, 7-2 in such a way that individual electrodes are of an additive polarity. Thereby, it is possible to obtain the DC-DC converter whose switching loss is reduced, whose overlap period on the secondary side of the transformer is shortened, whose dead time for prevention of the short circuit of a power supply is reduced, whose high frequency is realized and which can be miniaturized.

Power converter having dc filter capacitor

Abstract: PURPOSE:To reduce the size and weight and to increase the safety by making a DC filter capacitor out of a metalized film having segment fuse mechanisms which specifies the width and potential gradient at the rated voltage of the capacitor. CONSTITUTION:Metal deposited on a film 14 constitutes a large number of segments 16 surrounded by a large number of slits 17, and constitutes fuse mechanisms 18 interposed by slits 17 between segments adjoining each other. And oil-impregneted film capacitors are manufactured using metalized films with segment mechanisms this occasion, the potential gradient of the films at the rated voltage of the capacitors is made to be 150V/mum or larger. Besides, the width W of the fuse mechanism 18 sections is in a range of 0.5-1.4mm. Consequently, it becomes possible to reduce the outside dimensions and the weight of capacitors sharply. Besides, it also becomes possible to increase the safety.

Controlling equipment of electric rolling stock

Abstract: PURPOSE:To operate an electric railcar even when an auxiliary power source for auxiliary machines fails, by driving a main motor by an AC obtained by passing a DC from a pantograph through a filter reactor and a filter capacitor and by converting it by an inverter, and also by driving a blower motor for cooling the filter reactor through the intermediary of a step-down transformer. CONSTITUTION:A DC from a pantograph PAN is passed through a filter reactor FL and a filter capacitor and converted into an AC by an inverter INV. While a main motor IM is driven by this AC, a contact BLK2 is closed and the voltage thereof is stepped down by a transformer BTR so that a blower motor BL can be driven. Normally, the power from PAN is converted into the AC of 220V or 440V by an auxiliary power source SIV and auxiliary machines such as an electric lamp, an air-conditioner, BL, etc., are operated thereby. When SIV fails, a contact BLK 1 is opened, BLK 2 is closed and BL is driven. According to this constitution, even when SIV fails, the operation of an electric railcar is continued.

Precision regulated low loss high-power power supply

Abstract: In an AC-powered power supply with a bipolar controller V controlling the instantaneous value of a control quantity measured by a sensor F1 to a predetermined setting within a deviation of less than 0.1% at 1 Hz via the output DC current Io, and with an adjustable rectifier EQ followed by a charging inductance L1 and a filter capacitor C1, whereby the output of controller V is electrically connected to the output line of the power supply, the output of controller V is AC-decoupled from filter capacitor C1 by a decoupling inductance L2, two potentials Vo +V1 and Vo -V2 are supplied to controller V, and a sensor F2 is provided for the output current I2 of controller V, which feeds an output signal to a control unit CTR which controls rectifier EQ in such a way that the mean value of output current I2 of controller V is regulated to a minimum value. In this way, a stable and high precision control over the full frequency bandwidth is possible with high efficiency.

Decrease of inductance and electromagnetic interference in power electronics capacitors

Abstract: Pierron and Glaize (1992) have demonstrated that it is possible to decrease drastically parasitic inductances of wiring in commutation cells. But the inductance of capacitors still remains. Furthermore, in power electronics, problems of capacitors' inductance are well known: peaks of voltage in snubber capacitors (L dI/dt); output voltage ripples; perturbations in DC power supplies; low self-resonant frequencies (beyond this frequency, capacitors behave like an inductance), reduction of the lifetime of the whole circuit; switching capacitor disruption of operation of adjustable-speed drives; and especially electromagnetic interference (EMI). Here, from the study of standard capacitors, the authors have looked for solutions to reduce both inductance and EMI.

Pulse measurements on ferroelectric capacitors simulating memory switching

Abstract: Pulse switching investigations of ferroelectric PbZr0.44Ti0.56O3 capacitors prepared by organometallic chemical vapor deposition were done to simulate a ferroelectric memory. The released charge from the ferroelectric capacitor was measured with a reference capacitor, representing the bitline capacitances in a memory. A large reference capacitor will result in complete switching at low voltages, but gives a small detection signal. For a small reference capacitor partial switching and substantial backswitching of the ferroelectric material occurs. Here, a higher detection signal and improved endurance (≳1012 cycles) are found. Scaling the results indicates the feasibility of 0.2 μm2 capacitors operating at 3 V.

Pwm inverter control method

Abstract: PURPOSE:To make it possible to highly accurately control an output voltage with high speed response without inducing problems such as safety by making a switching frequency of a three-phase PWM inverter constant irrespective of load variations or the like. CONSTITUTION:An inverter is constructed by connecting together switching elements 2-7 which respectively consist of controllable semiconductor elements S1-S6. A d.c. voltage Ed is fed to d.c. input terminals of the switching elements, and filter reactors 8, 9 and 10 are respectively connected to a.c. output terminals, each having its own phase. Filter capacitors 11, 12 and 13 are connected in series with the filter reactors, and a.c. outputs are fed to loads. In a system in which a three-phase voltage inverter is constructed by a.c. LC filters, an optimum non-zero voltage vector and an optimum zero voltage vector are selected from eight output voltage vectors of a PWM inverter in order to control voltages of the filter capacitors 11, 12 and 13 which are output voltages. This causes currents of the filter capacitors to follow an instruction value current within a determined time.

Effects of combined stressing on the electrical properties of film and ceramic capacitors

Abstract: Advanced power systems which generate, control and distribute electrical power to many large loads are a requirement for future space exploration missions. The development of high temperature insulating materials and power components constitute a key element in systems which are lightweight, efficient, and are capable of surviving the hostile space environment. In previous work, experiments were carried out to evaluate film and ceramic capacitors for potential use in high temperature applications. The effects of thermal stressing, in air and without electrical bias, on the electrical properties of the capacitors as a function of thermal aging up to 12 weeks were determined. In this work, the combined effects of thermal aging and electrical stresses on the properties of teflon film and ceramic power capacitors were examined. The ceramic capacitors were thermally aged for 35 weeks and the teflon capacitors for 15 weeks at 200/spl deg/C under full electrical bias and were characterized, on a weekly basis, in terms of their capacitance stability and electrical loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also obtained. The results obtained represent the influence that short-term thermal aging and electrical bias, have on the electrical properties of the power capacitors characterized. >

Overvoltage protective circuit for power converter

Abstract: PURPOSE:To reduce production cost and realize compactness and light weight by decreasing an external surge and making usable a power semiconductor element of a relatively low breakdown voltage. CONSTITUTION:A parallel circuit of both a GTO thyristor 9 and a resistor 10 is connected in series to an input filter reactor 5 provided in a prestage of a power converter 7, and a series circuit of a resistor 11 and a thyristor 12 is connected in parallel to an input filter capacitor 6; and if an overvoltage state occurs, the GTO thyristor 9 is turned off and the thyristor 12 is turned on, thereby dividing and reducing the voltage by the resistors 10 and 11 and suppressing the voltage rise at the input filter capacitor 6.