Showing papers on "Filter capacitor published in 1992"

Optimized modulation techniques for the generalized N-level converter

Abstract: A balancing control strategy that allows the voltage differences among the DC link capacitors of the generalized n-level power converter to be minimized is presented. The case n=3 is treated, but the technique can be generalized to larger n values. The balancing algorithm does not achieve correct voltage sharing of the capacitors under all operating conditions, but it provides a great improvement. This strategy appears to be very promising in single-phase applications, for which nonredundant switching configurations do not affect the capacitor voltage balance. >

Zero voltage switching pulse width modulated power converters

Abstract: The power converter of this invention accomplishes zero voltage switching at both turn on and turn off transitions of a primary switch (206). A transformer (218) serves as both energy storage device and isolation mechanism. Inductance (216) placed in series with transformer (218) provides energy to drive the turn on resonant switching transition of switch (206). Additional energy storage is provided by a required primary side filter capacitor (220) and an output filter capacitor (224). During a first operational state in which switch (206) conducts, energy is transferred from power source (202) to transformer (218) and capacitor (220). During the first state, capacitor (224) supports a load (226). During a second operational state, a second primary switch (212) and a secondary switch (234) conduct and energy is transferred from capacitor (220) and transformer (218) to series inductance (216), capacitor (224) and load (226). The resonant transition from the first state to the second state is driven by some combination of stored energy in transformer (218) and inductor (216). The AC magnetizing currents and AC magnetic fields of transformer (218) can be made smaller than the average magnetizing current and the average magnetic field, respectively, and the converter can accomplish zero voltage switching at all line and load conditions.

Dimmer with reduced filtering losses

Abstract: A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Harmonic distortion caused by capacitors implemented with MOSFET gates

Abstract: The capacitive gate structures available in digital-oriented CMOS processes are reviewed, with emphasis on their use as linear capacitors. It is shown that the voltage harmonic distortion in MOS gate capacitors biased in either accumulation or strong inversion is almost technology independent. Experimental and analytical results indicate that the total harmonic distortion in an adequately biased (2.5 V) gate capacitor can be kept low (THD >

High energy density double-layer capacitors for energy storage applications

Abstract: The feasibility of applying the double-layer capacitor to uninterruptible power systems and electric vehicles is addressed. The double-layer capacitor improves energy storage density by two orders of magnitude over the traditional electrolytic capacitors. Compared to batteries, the energy density of the double-layer capacitor is lower, but its charge/discharge rate is significantly higher. The application of double-layer capacitors can be tailored to auxiliary energy and burst mode storages which require fast charge/discharging and high energy density. A description is given of the double-layer capacitor technologies including its materials, structure, and characteristics; potential application areas of double-layer capacitors; and analytical and experimental results of double-layer capacitor applications. >

Frequency-domain analysis of series resonant converter for continuous conduction mode

Abstract: Most previous analyses of a series resonant DC-DC power converter (SRC) have been performed in the time domain. A comprehensive frequency-domain analysis of the SRC for steady-state operation, along with experimental results is presented. Simple analytical design equations are derived for the basic performance parameters of the converter operating in the continuous conduction mode (CCM) using Fourier series techniques and a high-Q/sub L/ assumption. Three types of class-D current-driven rectifiers are considered. The diode threshold voltage and forward resistance as well as the ESR of the output filter capacitor are taken into account. Experimental results were in good agreement with theoretical predictions. >

Stable capacitive pressure transducer system

Abstract: A stable pressure transducer system is disclosed. The transducer system includes a variable capacitor having conductive plates with one of the conductive plates being associated with a diaphragm variable under pressure changes to vary the capacitance of the variable capacitor. The system also includes a reference capacitor. Circuitry for applying signals to the pressure variable and the fixed reference capacitor is used to obtain outputs from each of the capacitors with the output from the variable capacitor varying in amplitude with its capacitance. Circuitry for differentially combining the outputs from the variable and fixed capacitors provides an output voltage indicating the pressure applied to the diaphragm. In order to stabilize the output of the transducer, an isolating capacitor having a capacitance value at least several times greater than the capacitance of the variable and reference capacitors is coupled in series with one or both of the variable and reference capacitors. Preferably two isolation capacitors are used, one in series with each of said variable and reference capacitors on either side thereof. However, in some cases a single isolating capacitor between a common output point of the variable and fixed capacitors and ground may be effective.

Circuit models of PWM DC-DC converters

Abstract: A systematic method is presented for including parasitic resistances and offset voltage sources of power switches into averaged dynamic large-signal, DC, and small-signal circuit models of PWM converters operating in continuous conduction mode. This method is based on the principle of energy conservation. It is shown that the equivalent circuits can be manipulated, using the reflection rule, to simplify the models. A procedure of modeling the buck converter is detailed. Models of all buck-derived converters have the same structure as that for the buck converter, but expressions for averaged components are different. These expressions are given. A design equation for selecting the value of the filter capacitance is derived, and it is shown that the ripple voltage can be made dependent only on the equivalent series resistance of the filter capacitor. >

Unity power factor control for dual active bridge converter

Abstract: A dual active bridge converter, including high-frequency transformer-coupled input and output bridge converters, receives a rectified ac line voltage via a rectifier acting in a resistive mode and a small, high-frequency filter capacitor. A phase angle controller controls a phase shift between the voltages across the transformer windings such that high-efficiency dc-to-dc conversion is achieved, while maintaining unity power factor at the ac input, using high-density circuitry with small filter components and without adding additional front-end power factor correction circuitry.

Detent switching of summing node capacitors of a delta-sigma modulator

Abstract: The thermal noise generated through the feedback capacitor of a delta-sigma modulator is attenuated by transferring a reference voltage through the capacitor in two separate steps during each sampling period. This permits a reduction in the size of the feedback capacitor, thereby reducing thermal noise, without increasing the voltage on the switching capacitors on the summing node side of the feedback capacitors which would induce degradation due to hot electron effects.

Power distribution circuit with power factor correction and independent harmonic current filter

Abstract: An electrical power distribution system of an industrial plant or a commercial building and having a capacity for delivering at least 500 KVA, includes a voltage step-down transformer connected between an AC source of electrical energy and a pair of power distribution line conductors across which there is connected a pulsed inductive load, such as a motor with a thyrister speed controller. The power factor of the system is corrected by a power factor correction capacitor connected directly across the system power distribution line conductors. Pulsed inductive loads tend to excite large harmonic currents in such systems having both a transformer and a power factor correction capacitor directly across the distribution line conductors. A filter, made up of a filter capacitor and a filter inductor tuned exactly to one harmonic, are connected in a series circuit branch that is connected directly across the system power distribution line conductors. The name plate KVAR rating of and capacitance of the filter capacitor is chosen to be much smaller than corresponding KVAR rating and capacitance of the power factor correction capacitor in order to make the function of the power factor correction capacitor and the function of the filter essentially independent of each other. This independence is attributable to the substantially no current flow of frequency of the AC power source through the filter capacitor and substantially no current at the harmonic frequency to which the filter is tuned flows through the power factor capacitor.

High resolution charge-redistribution a/d converter

Abstract: A circuit technique to achieve 14-bit resolution in a charge-redistribution CMOS analog-to-digital converter. The sign bit (B13) plus the six most significant bits (B12 - B7) are obtained using a 6-bit capacitor array, the next five bits (B6 - B2) are determined using a resistor array, and finally the last two bits (B1 - B0) are obtained by use of a second 2-bit capacitor array. The area of the resulting 14-bit A/D converter is not appreciably larger than a corresponding 12-bit A/D converter. The 6-bit capacitor array is realized by connecting unit capacitors (C) of a unit capacitor array. In the second capacitor array, at least one of the capacitors is realized by subdividing the unit capacitor. Since the accuracy of capacitors in the second capacitor array need not be as great as the accuracy of capacitors in the 6-bit capacitor array, subdividing the unit capacitor does not affect the accuracy of the converter.

Fourth order damped lowpass filter for obtaining high power factor and low total harmonic distortion

Abstract: An arrangement includes a network for connection between an AC power supply and the input of a DC power supply containing rectifiers and a filter capacitor. The network forms a fourth order, damped lowpass filter that waveshapes the AC input current so as to either reduce or remove the magnitude of harmonics which primarily cause distortion of the input current waveform. In one embodiment, the waveshaping network includes a tapped inductor connected in series with the input of the DC power supply. A series combination of a damping resistor and a first capacitor is connected in parallel with the series inductor. One end of a second capacitor is connected to the tap of the inductor. The waveshaping network increases the power factor and lowers the total harmonic distortion the input of the DC power supply presents to the AC power supply.

Induction motor drive with intelligent controller and parameter adaption

Abstract: A variable speed four-quadrant AC-motor drive using a robust and cost-effective induction machine with a current source inverter with gate turn-off thyristors (GTOs) was investigated. The essential advantage of this topology is the ability to produce currents and voltages in the machine with very low harmonic content in the whole operating range. Therefore, with this solution torque ripple, noise, and losses can be reduced considerably. However, the main problem of this topology results in the weakly damped resonant system consisting of the filter capacitors and the inductance of the machine. To stabilize this system and to attain a high dynamic and accurate behavior of the drive, a cascaded multi-input control system was designed. For robustness this control system is adapted to parameter changes of the mutual inductance (saturation) and the stator and rotor resistance (temperature), and an outline identification of the resistances is added. Furthermore, the influence of iron losses on the system is compensated. >

Design of precision capacitors for analog applications

Abstract: The authors describe and analyze two capacitors which are incorporated in a baseline BiCMOS technology without added process complexity. The first capacitor is formed between degenerated doped polysilicon and silicon. The second is formed between two degenerately doped polysilicon layers. In both structures, the insulator is a deposited or grown oxide. The sensitivity of the capacitor voltage coefficient to oxide thickness and surface dopant concentration is discussed theoretically and compared to measured data. The two capacitors are optimized to exhibit very low voltage coefficients. >

Input filter design considerations for boost-derived high power-factor converters

Abstract: The authors present an analysis which gives insight into the selection of the input inductor and the optional ripple current filter capacitor used in single phase boost-derived high power factor converters. The analysis uses circuit models to derive expressions which relate the filter inductor and capacitor to input current total harmonic distortion (THD). A simple model of a hysteresis-controlled high power factor converter is implemented in PSPICE to corroborate the analysis. A comparison is made between analytic and simulated results. The analytic model proves to be more conservative that the simulations, always predicting a slightly higher THD. >

Application of capacitors for power factor correction of industrial electrical distribution systems

Abstract: The author summarizes information for determining the proper circumstances for applying capacitors to improve the operating efficiency of an industrial electrical distribution system. The following topics are discussed; the function of capacitors in an electrical power system; calculations to select the appropriate value of capacitance; selection of the optimal location in the distribution system to connect the capacitors; automatic switching of capacitors to match changes in the power system load, including system variations when capacitor switching is used; economic factors involved to justify the addition of capacitors to an industrial power distribution system; system harmonics and resonance effects in capacitor installations; and requirements of the National Electrical Code (NEC) concerning the characteristics and installation of capacitors. >

Auxiliary power supply for vehicle

Abstract: PURPOSE:To realize quick restart after power interruption due to overvoltage by a constitution wherein a power supply interrupting means opens a disconnector when a voltage detector detects terminal voltage of a filter capacitor higher than a predetermined level thus discharging the filter capacitor through a resistor and then a power supply restarting means throws in the disconnector, CONSTITUTION:When an overvoltage detector 7 detects a voltage higher than a set level, an OFF signal is fed to a GTO thyristor 5 thus closing the contact 13a of an overvoltage detector 13. Since b contact 16b of a relay opens, discharging takes place gradually through a resistor 18 and a capacitor 19 and the exciting coil 10c of a discharge contactor 10A is deenergized slowly thus closing the discharge contactor 10A after opening of a disconnector 2A. Consequently, a filter capacitor 4 is discharged through a charging resistor 9, a filter reactor 3, the discharge contactor 10A and a discharge resistor 11. After the exciting coil 16c of a relay is deenergized, the b contact 16b of the realy closes to restart the auxiliary power supply for vehicle automatically.

Power converter for electric vehicle

Abstract: PURPOSE:To prolong the operation sustaining time of inverter through a capacitor having low withstand voltage upon contact loss of pantograph and to protect elements positively against short circuit fault of inverter by ON/OFF controlling the voltage across an external filter capacitor bank which is interruptible from the inverter. CONSTITUTION:Trolley voltage detected through a voltage detecting element 32 is compared with a reference value and a gate drive circuit 34 performs switching control of a GTO thyristor 16 to charge an external filter capacitor bank 14 with a constant voltage lower than the rated voltage of a trolley 1. When a voltage detected through the voltage detecting element 32 drops below a set level, a rectifying element 15 is turned ON to feed power to an inverter circuit 7. Upon occurrence of short circuit fault between upper and lower arms of the inverter circuit 7, an abnormal quick discharge detecting circuit 23 and a gate drive circuit 24 interrupt the operation of a GTO thyristor 20. Consequently, the external filter capacitor bank can be constituted of capacitors having low capacity and low withstand voltage.

Nonlinearities of capacitors realized by MOSFET gates

Abstract: The capacitive gate structures available in digital oriented CMOS processes are reviewed, with emphasis on their use as linear capacitors. Experimental and analytical results indicate that the total harmonic distortion (THD) in an adequately biased (2.5 V) gate capacitor can be kept low (THD >

High frequency design and performance of tabular capacitors

Abstract: The electrical design, analysis and performance of tabular capacitors are presented. Simple formulas for capacitances are derived for spiral and concentric type tabular capacitors. By numerical methods the regions of greatest electric stress in the dielectric are found. The influence of bumps on the capacitor plates is examined by the method of conformal transformation. It is shown that a small circular ridge running the length of the capacitor can reduce the voltage rating by 50%. The inductance of the capacitor sets an upper bound on the highest frequency at which the capacitor behaves ideally. It was previously shown that high frequency behavior is influenced by the particular connection used in a capacitor. For a spiral wound tabular capacitor one type of connection is considered, and its equivalent circuit is exhibited. For concentric cylindrical tubular capacitors the only type of connection possible is the one considered for the spiral-wound capacitors. For that configuration a closed form electrostatic induction coefficient and inductance coefficient matrices are presented and used for high frequency analyses. >

A new method of capacitance measurement

Abstract: Three circuits for measuring capacitors are presented. These circuits form a sequence in that each succeeding circuit is an improvement in comparison with the previous one. Each circuit employs a rectifier, and each circuit is excited by a square-wave voltage. Analyses are provided, and sensitivities and laboratory results are given. >

Miniaturized power supply for an electroactive actuator

Abstract: A circuit for providing from a low voltage input, a high voltage output to a segmented electroactive actuator, wherein each of the segments function as a filter capacitor and a load, comprising a transformer, an input switching means, input coupling means and voltage converter means. The transformer has a primary and a plurality of secondary windings, and the input coupling means couples the low voltage input to the primary winding. The input switching means is coupled to the primary winding for permitting current to flow through the primary winding. The voltage converter means is coupled to each of the secondary windings and comprises output coupling means for coupling to said filter capacitors and when so coupled, the voltage converter means provides a plurality of output voltages in series and wherein each output voltage is generated across each of the filter capacitors of the segments.

Bank assembly system for power capacitors

Abstract: not available for EP0527982Abstract of corresponding document: FR2671904A device for assembling a bank of high and medium frequency power capacitors is characterized by the use of two collector plates (1 and 2) spaced close together, cooled by circulation of a coolant, and connected to each of the capacitors (4) in the bank by means of connections (8 and 9) establishing an electrical and thermal contact. The main objective of a device of this type is to avoid any one of the capacitors in the bank being subjected to the magnetic field created by the neighboring capacitors. According to a further aspect of the invention, the unwanted series inductance of a bank arranged according to the invention is negligible.

Dual-purpose induced switch with timing delay function

Abstract: The utility model discloses two induced electrodes arranged on a switch panel, wherein, an induced conventional electrode is switched into an electrical integrated circuit, a monostable shaping circuit composed of a resistor and a capacitor, a bistable circuit composed of an integrated circuit for receiving shaping pulsed signals, a high level locked by the Q end of the integrated circuit in the bistable circuit and a switch circuit composed of a controllable silicon triggered after being filtered by the resistor and the capacitor through a filter capacitor and a voltage dividing resistor; a timing delay electrode is switched into a timing delay switch circuit composed of a transistor and a controllable silicon connected with and output a high-level NOT gate and an NOT gate inverted the high level; a base is connected with the inverted NOT gate and a collector is connected with the control gate of the controllable silicon. The two switching circuits respectively pass through a silicon bridge and a dual-purpose induced switch with timing delay functions; the controllable silicon controls the loop of a lighting lamp. The utility model has two operational modes of 'induced on / induced off' and 'induced on / automatic timing delay off'.

Process for the symmetrical subdivision of a DC voltage in series with a voltage divider consisting of n capacitors, and circuitry for carrying out the process.

Abstract: of EP0330055The invention relates to a process for the symmetrical subdivision of a DC voltage (UG1) applied to a voltage divider (4) consisting of n capacitors (2) to which there is connected electrically in parallel in each case a variable load (6) and an actuator (8), the actuators (8) being connected electrically in parallel on the input side. According to the invention, the voltages (Ud2 to Udn) applied to the capacitors (2) are in each case compared with a voltage drop (Ud1), used as a reference voltage, of a capacitor (2), and the difference voltages ( DELTA U1 to DELTA Un-1) are in each case converted by means of a voltage/phase-angle converter (20) into a phase-angle ( alpha ) which is in each case supplied to a control set (10) of an actuator (8), so that the controller AC voltages (uSt1 to uStn) are phase shifted with respect to the reference controller AC voltage (uSt1), as a result of which in each case a compensating current (i1 to in) is caused to flow between the n capacitors (2) via the actuators (8). A symmetrical voltage subdivision is thus produced of a DC voltage applied to a voltage divider (4) consisting of n capacitors (2), independently of the variable loads (6) of the capacitors (2).

Electric vehicle controller

Abstract: PURPOSE:To prevent trouble in a filter capacitor from spreading and to prevent higher harmonic components flowing from a power converter to a stringing from increasing at the time of trouble in the capacitor in an electric vehicle controller comprising a power converter constituted of switching elements wherein trouble in the filter capacitor constituted of s electrolytic capacitors is detected and the type thereof is decided. CONSTITUTION:A filter capacitor 4 comprising electrolytic capacitors 411-414, 421-424 is provided with a trouble detecting means 7 and a type of trouble deciding means 8.