Showing papers on "Rectifier published in 1990"

A novel soft-switching full-bridge DC/DC converter: Analysis, design considerations, and experimental results at 1.5 kW, 100 kHz

Abstract: The authors present an improved soft-switching full-bridge converter which is especially suitable for high-power application (e.g. more than 1 kW output) because of its inherently high efficiency. The addition of an external commutating inductor and two clamp diodes to the phase-shifted PWM (pulse width modulation) full-bridge DC-DC converter substantially reduced the switching losses of the transistors and the rectifier diodes, under all loading conditions. The authors analyze the conditions for lossless transitions, discuss the effect of the added components on the operation of the converter, and present practical considerations and test results for a 1.5 kW converter with 100 kHz clock frequency. The converter has an efficiency above 95% at 60 V output, is free from voltage overshoots, and exhibits well-controlled transitions for all switch and rectifier voltages and currents. >

Design of a simple high-power-factor rectifier based on the flyback converter

Abstract: An equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented. This simple model correctly describes the basic power processing properties of the converter, including input port resistor emulation, output port power source characteristics, and control characteristics. Based on this model, steady-state design equations are described and are used in a design example. Design of the slow output voltage feedback loop is also considered. A small-signal AC model is developed for both the resistive load and the DC-DC converter-voltage regulator load cases. In addition, a simple first-order approximation for the line current distortion and phase shift caused by 120 Hz duty cycle variations is derived. >

A new single phase to three phase converter with active input current shaping for low cost AC motor drives

Abstract: A single-phase-to-three-phase converter for a low-cost AC motor drive is proposed. The converter employs only six switches and incorporates a front-end half-bridge active rectifier structure that provides the DC link with an active input current shaping feature, which results in sinusoidal input current at close to unity power factor. The front-end rectifier in the converter permits bidirectional power flow and provides for excellent regulation against fluctuations in source voltage, facilitating regenerative braking of the AC motor drive. A control strategy that maintains a near-unity power factor over the full operating range and is easy to implement is described. Suitable design guides for the selection of filter components are presented. Simulation and experimental results that verify the developed theoretical models are also presented. >

A novel passive waveshaping method for single-phase diode rectifiers

Abstract: A novel passive waveshaping method for single-phase diode rectifiers is presented. It is shown that application of the proposed method maintains high-input power factor, lowers rectifier current stresses, and lowers the volt-ampere (VA) rating of the associated reactive components as compared to the standard diode rectifier. Relevant input and output current waveforms, component ratings, and power factor values are derived. Different modes of operation are discussed as a means of obtaining high performance. Key predictions, such as input/output waveforms and associated harmonic spectra, have been verified experimentally on a 1 kVA laboratory prototype unit. >

Analysis of class E zero-voltage-switching rectifier

Abstract: Analysis of Class E rectifiers offer a novel means of high-frequency high-efficiency rectification. An analysis and experimental results are presented for a class E zero-voltage-switching (lowdv/dt) rectifier. The circuit consists of a diode, a capacitor shunting the diode, and a second-order low-pass output filter. The shunt capacitor shapes the voltage across the diode so that the diode turns on and off at low dv/dt. Therefore, switching losses and switching noise are reduced significantly. An advantage of the rectifier is that the diode junction capacitance is absorbed into the shunt capacitor. The basic equations governing rectifier operation are derived. The following performance parameters are determined: current and voltage waveforms, device stresses, component values, and power-output capability. The measured performance shows excellent agreement with the design calculations. >

Analysis and design of class-E/sup 2/ DC/DC converter

Abstract: A family of class-E/sup 2/ DC/DC power converters is introduced. Their analysis and design are presented and experimentally verified. The converters are composed of class-E inverters and class-E rectifiers. Zero-voltage switching (with low dv/dt) of the transistor and zero-current switching (with low di/dt) of the rectifier diode reduce switching losses in both stages of the converters, making them especially suitable for high-frequency operation. Because of the high loaded quality factor of the resonant circuit, the range of frequency required for output-voltage regulation is as narrow as 5.46% for load resistances from a full load of 100 Omega to an open circuit. The full-load overall efficiency is 80.36% at 1 MHz. The converters can also operate at a fixed frequency if synchronous rectifiers are applied. The reduction of class-E/sup 2/ converters to lower order converters is presented. Many multiresonant converter topologies are created in this way. The class-E/sup 2/ converters can be utilized to build highly efficient high-power-density switching power supplies. >

Compressor drive system

Abstract: A compressor drive system that includes a thermostat producing a signal indicating the measured air temperature, a modulation control circuit connected to the thermostat to produce a motor drive signal from the temperature signal and which is output to a motor drive switching bridge circuit. The motor drive switching bridge circuit is connected to a rectifier that converts single phase alternating current to direct current. The switching bridge uses the motor drive signal from the modulation control circuit and the rectifier output to produce multiphase power including a speed control signal imposed on the power for regulating speed. A motor connected to drive a compressor is included. The motor is powered by the motor drive switching bridge circuit multiphase power output. The speed of the motor is controlled as a function of the temperature signal.

Sinusoidal line current rectification at unity power factor with boost quasi-resonant converters

Abstract: A sinusoidal line current rectifier is considered at unity power factor, where the conventional boost converter, usually utilized between the diode rectifier bridge and the DC bus capacitor, is replaced with a boost zero-current switching quasi-resonant converter (boost ZCS-QRC). The zero-current switching quasi-resonant rectifier (ZCS-QRR) is analyzed theoretically. Normalized curves are plotted, and equations that allow high flexibility in design are developed. A design example is proposed, and experimental results are presented to demonstrate the operating principle, the feasibility of the technique, and the validity of the theoretical analysis. >

A high switching frequency IGBT PWM rectifier/inverter system for AC motor drives operating from single phase supply

Abstract: A PWM (pulse width modulation) rectifier/inverter system using IGBTs (insulated-gate bipolar transistors), capable of switching at 20 kHz, is reported. The base drive circuit for the IGBT, incorporating short circuit protection, is presented. The inverter uses an Undeland snubber together with a simple energy recovery circuit, which ensures reliable and efficient operation even for 20 kHz switching. The front end for the system is a regenerative single-phase full-bridge IGBT inverter along with an AC reactor. The steady-state design considerations are explained, and control techniques for unity power factor operation and fast current control of the front end converter, in rotating as well as stationary reference frames, are discussed and compared. Results from computer simulations and experimental results for a 1.5 kW prototype system using GE type 6E20 IGBTs are presented. >

Uninterruptible power supplies

Abstract: Power supply apparatus is disclosed which can be configured as a power line filter or an uninterruptible power supply having a battery test on load capability. It comprises an input reversible rectifier connectable between an AC supply and a high voltage internal DC bus, a second reversible rectifier interconnecting storage batteries to the high voltage DC bus, and an output module supplying a desired DC output or an AC output. In use the voltage on the internal DC bus is maintained at a greater level than that of (a) the instantaneous repetitive peak of the incoming voltage, and (b) the peak battery storage voltage. Battery test means is provided by allowing the dumping of the charge stored within the storage batteries for a certain period at the maximum available rate into the internal bus and back into the AC supply through the said reversible rectifiers; meanwhile observing the extent of the battery voatage drop so caused.

Analysis of the dynamic and steady-state performance of Cockcroft-Walton cascade rectifiers

Abstract: A detailed analysis, based on digital simulation, of the Cockcroft-Walton rectifier, including transient and steady-state voltages and currents on any component, was performed. It is shown that the numerical solution of the system may be effectively implemented by coupling the modified nodal approach formulation of the circuit equations with companion models and piecewise linear approximations of nonlinear elements. Good agreement between simulated and experimental results confirmed the validity of the proposed model/program. In the transient analysis it was shown that the start-up time of a Cockcroft-Walton rectifier is directly related to the number of stages, increasing as the number of stages increases. The output voltage regulation characteristics are worse for a larger number of stages. A study of the influence of an inductance in series with the voltage source showed that it may be chosen in such a way as to increase the output average voltage and improve its regulation. The analysis of this rectifier fed by a square-wave voltage source showed that, in this case, the output voltage regulation is improved. However, the output voltage overshoots and input current peaks are increased. >

Class-E zero-voltage-switching and zero-current-switching rectifiers

Abstract: A number of class-E, half-wave and full-wave, zero-voltage-switching (low dv/dt), zero-current-switching (low di/dt), and mixed-mode rectifiers are introduced and verified experimentally. The rectifiers are derived from conventional rectifiers by adding reactive components. New conventional rectifiers are also introduced and presented in a systematic manner. The principle of class-E rectifier operation is explained using current and voltage waveforms. The class-E rectifiers offer a means of rectification suitable for high-frequency applications, e.g. in resonant DC/DC power converters. A general approach to the synthesis of resonant DC/DC converters is presented. >

A simple scheme for unity power-factor rectification for high frequency AC buses

Abstract: A simple scheme is proposed for offline unity power factor rectification for high-frequency AC buses (20 kHz). A bandpass filter of the series-resonant type, centered at the line frequency, is inserted between the line and the full-wave rectified load. The Q=Z/sub 0//R/sub L/ formed by the load and the characteristic impedance of the tank circuit determines the power factor, the boundary between continuous and discontinuous conduction modes, the peak stresses, and the transient response of the rectifier. It is shown that for Q>2/ pi the rectifier operates in continuous conduction mode and the output voltage is independent of the load. Also, it is shown that for Q>2 the line current is nearly sinusoidal with less than 5% third-harmonic distortion and the power factor is essentially unity. An increase in Q causes an increase in the peak voltages of the tank circuit and a slower transient response of the rectifier circuit. The DC, small-signal, and transient analyses of the rectifier circuit are carried out, and the results are in good agreement with simulation and experimental results. >

Alternator rectifier bridge assembly

Abstract: An alternator rectifier bridge is incorporated into an alternator housing by inserting half of the diodes of the bridge into apertures formed into an alternator housing end plate which then serves as one output for the alternator and also as a massive heat sink to dissipate heat generated in the diodes The other half of the diodes of the bridge are inserting into apertures formed in a radiator plate which is embedded into a plastic circuit member together with conductor members which interconnect electrodes of the diodes to stator windings of the alternator and also perform other electrical connections required for efficient manufacture and proper operation of the alternator The radiator plate serves as the other output for the alternator and also as a heat sink The plastic circuit member is coupled to the alternator housing end plate such that the electrodes of the diodes embedded therein pass through the plastic circuit member to engage corresponding ones of the conductor members resulting in a compact, highly efficient bridge which is readily assembled, preferably in an automated manner, using a limited number of component parts

Power factor improvement of a diode rectifier circuit by dither signals

Abstract: A power factor improvement to a diode rectifier having a high-frequency inverter on the load is described. The principle of the improvement is based on dither signal effects for linearization of the nonlinear system. A diode rectifier circuit, which can be regarded as a dead-zone element, is linearized based on this principle by adding a high-frequency dither signal to the input voltage. The output voltage of the high-frequency inverter is applied to the dither, which makes the input current of the rectifier sinusoidal. The dither rectifier circuit is composed of a diode voltage-doubler rectifier and a high frequency inverter that consists of only two switching elements. Its power factor is shown to be 99.2%, and the third and fifth harmonics are 10% and 0.4%, respectively. Uses of the high-frequency inverter in fluorescent lamp and switching power supply applications are discussed. >

Novel pseudo RMS current converter for sinusoidal signals using a CMOS precision current rectifier

Abstract: A very simple pseudo RMS-to-DC current converter for sinusoidal signals is described. The most salient feature of the circuit is that it uses a CMOS precision current rectifier consisting of only two transistors and thus operates throughout in the current domain. The full-wave rectifier was built using CD4007 devices and tested. It was observed that the transfer curve is sharp even at low nanoampere input levels. The converter is expected to work up to 100 kHz. >

An uninterrupted power supply system having improved power factor correction circuit

Abstract: An uninterrupted power supply (UPS) system (10) is provided with a power factor correction circuit (30). The UPS system includes a rectifier (D1, D2) having input terminals (12, 14) for connection to an AC utility power source (32) and ouput terminals (+DC, -DC). The power factor correction circuit is operatively connected to the input and output terminals of the rectifier to cause the UPS system to exhibit substantially unity power factor to the AC utility power source.

An induction motor drive using an improved high frequency resonant DC link inverter

Abstract: An induction motor drive using an improved high-frequency resonant DC link inverter is presented. The resonant circuit was systematically analyzed first to establish the criteria for initial current selection, and a new circuit was then proposed to establish the bidirectional initial current. The proposed current initialization scheme solves voltage overshoot and zero-crossing failure problems in the ordinary resonant DC link inverters. A three-phase 3 kW IGBT (insulated-gate bipolar transistor) based 60 kHz resonant link inverter has been constructed and successfully tested with an induction motor drive. The speed control system is implemented using two microprocessors: TMS320C25 for computation and INTEL 80386 for monitoring and user interface. Experimental results showing the superior operation of the proposed resonant DC link inverter drive are presented. >

Power converter for a switched reluctance motor

Abstract: Power conversion apparatus (10) for an n-winding switched reluctance motor (M). A rectifier circuit (12) rectifies line voltage supplied to the motor. A switching circuit (14) supplies, at any one time, electrical energy to the motor winding most capable of converting it to mechanical work. A storage capacitor (C1) stores any unconverted portion of the energy and returns it to the winding during subsequent cycles. The switching circuit provides a substantially long conduction period 2 (θ) for supplying electrical energy to the motor during each line voltage cycle. This permits use of a substantially smaller energy storage capacitor and results in a higher input power factor for circuit operation. Circuits for precharging the storage capacitor are eliminated. The switching circuit is capable of more modes of operation than previous circuits, while using fewer components, and therefore provides a lower cost design.

Uninterruptible power supply

Abstract: An uninterruptible power supply including a rectifier for receiving a first AC power signal and converting the first AC power signal into a first DC power signal to produce a DC power output of the uninterruptible power supply, a battery for supplying a second DC power signal, a controlled rectifier for receiving a second AC power signal and converting the second AC power signal into a controlled power output, and a switch connected to receive the second DC power signal from the battery for producing the second DC power signal as the DC power output power when the first AC power signal is interrupted. Output terminals of the rectifier are connected in series with output terminals of the controlled rectifier and the battery, whereby the first DC power signal and the controlled power output are added and applied to the battery for charging thereof.

Adjustable ac power supply equipment for air-conditioner system

Abstract: In an adjustable a.c. power supply for an air-conditioner system, comprising a first frequency converter for driving a compressor motor of a first air-conditioner, a second frequency converter for driving a compressor motor of a second air-conditioner, and a common a.c. power supply for delivering a.c. power to both frequency converters, a rectifier included in at least one frequency converter is constructed as a controllable rectifier and subjected to phase-control so that a synthetic higher harmonic current of the two frequency converters as viewed from the a.c. power supply is reduced. By conducting phase-control of plural controllable rectifiers in a manner that, e.g., one rectifier has a phase-control angle of zero degrees and the other rectifier has a phase-control angle of 30 degrees, load current from the a.c. power supply is permitted to have a waveform closer to a sine wave, i.e., a waveform in which higher harmonic components are further reduced.

Potential impact of emerging semiconductor technologies on advanced power electronic systems

Abstract: It is shown that a simple expression for k/sub D/=R/sub on/*C/sub in/ of a power semiconductor device can be used to evaluate the optimum performance feasible from a given material technology. A high-density, high-frequency microelectronic power supply based on synchronous rectifier switching topology is used to illustrate the potential impact of emerging semiconductor technologies on advanced power electronic systems. It is shown that optimum power devices based on wide-energy-bandgap semiconductors such as silicon carbide and diamond provide the basis for power conversion at very high frequencies. >

Vehicle ac generator control device for adjusting output voltage in accordance with vehicle conditions

Abstract: A vehicle AC generator control device, comprises: an AC generator with a field coil; a rectifier for rectifying an AC output of the AC generator; a battery connected to an output terminal of the rectifier; a voltage regulator with a switching element series-connected to the field coil, the voltage regulator detecting a terminal voltage of the rectifier or battery to operate the switching element to control a field current of the field coil to adjust an output voltage of the AC generator to a predetermined value; a field coil exciting power source for providing an output voltage which is higher than the output voltage of the AC generator; and a field current limiter for limiting a maximum conduction rate of the switching element according to a speed of rotation of the AC generator.

Analysis and design of class E zero-current-switching rectifier

Abstract: The analysis, design equations, and experimental results are presented for a class-E zero-current switching (low di/dt) rectifier. Equations governing circuit operation are derived, assuming an ideal sinusoidal input current source. The diode turns on at zero di/dt and low absolute value of dv/dt, and turns off at low absolute value of di/dt, reducing switching losses, switching noise, and reverse recovery effect. The diode junction capacitance is not included in the rectifier topology and causes ringing after turn-off. The experimental results of 0.5 MHz agreed with the design calculations. The rectifier can be used in high-frequency, high-power-density switching power supplies. >

Optoelectronic relay circuit having charging path formed by a switching transistor and a rectifying diode

Abstract: A semiconductor relay circuit includes an output FET connected to a diode array. The diode array generates a photovoltaic output in response to a light signal from a light emitting element. Across the drain and gate of the FET is a series circuit of a semiconductor device and a rectifier is connected, the switching transistor is being made conductive upon receipt at the diode array of the light signal and forms a charge current path for an accumulated charge across the gate and source of the FET. The rectifier restrains a photocurrent from reversely flowing between the drain and gate of the FET. Turning-on and turning-off operations of the relay circuit can be thereby made both achievable at a higher speed, and the reverse flow of the photocurrent upon the conduction of the output FET can be prevented from occurring.

Microprocessor-based voltage controller for wind-driven induction generators

Abstract: A microprocessor-based closed-loop system has been developed for wind-driven self-excited induction generators using a controlled rectifier to maintain a constant DC load voltage with varying rotor speeds. The configuration and implementation of the control scheme are described. Test results on a self-excited induction generator demonstrate the satisfactory performance of both the hardware and the software of the control scheme, and the utility of the set-up as a whole. The steady-state analysis of the generator is extended to include the controlled rectifier, and the performance characteristics are predicted. >

Laser ranging device - uses modulated semiconductor laser and phase sensitive rectifier

Abstract: The phase-sensitive rectifier comprises 2 synchronous rectifier stages (G1,G2). The transmission signal (10) provided by the laser (11) is interrupted after a given number of periods of the primary modulation frequency, for a defined number of periods, via a switch element (12). Two intergrating amplifiers (V3,V4) are coupled to the outputs of the synchronous rectifiers (G1,G2) via analogue circuits (S2,S3) during the interruption interval. ADVANTAGE - Increased measuring range.

Fault indicator having liquid crystal status display

Abstract: A fault indicator for indicating the occurrence of a fault current in a monitored electrical conductor of an AC power distribution system utilizes a liquid crystal display having independent "F" and "N" display elements. A rectifier circuit capacatively coupled to the conductor charges a first capacitor in the presence of voltage on the conductor. A second capacitor is connected to the first capacitor by a first reed switch in magnetic communication with the conductor. Upon occurrence of a fault current the reed switch closes and a portion of the charge on the first capacitor is transferred to the second capacitor, which is connected to the "F" display segment electrodes of the liquid crystal display to cause an "F" to be displayed. The fault indication can be reset either by the slow discharge of the second capacitor, or by discharging the second capacitor through a second reed switch manually actuated by a magnetic reset tool from outside the fault indicator housing. The "N" display segment electrodes are capacitively coupled to the monitored conductor and system ground to provide an "N" display indicating that voltage is present on the conductor.

Four-terminal unity power factor electronic rectifier

Abstract: A four-terminal, unity power factor, electronic rectifier module. The electronic rectifier module is self-contained and includes therein bridge diodes which form a full wave bridge rectifier, a control circuit, and a diode which components act together to draw a sinusoidal current from the line. The self-contained, four-terminal module is designed to permit a high-frequency input capacitor and a line inductor to be connected to its input terminals and a smoothing capacitor to its output terminal. The module avoids the need to provide a separate pair of power terminals for the standard filtering components, resulting in a more economical package and in an easier-to-use module.

Rotating rectifier assembly

Abstract: A rotating rectifier assembly which can be used in a brushless electrical generator comprises an arrangement for supporting diode semiconductor devices in an axially loaded assembly of components within a housing of the rectifier assembly without compressively loading the diode semiconductor devices themselves. Provision is made for flowing liquid coolant in direct contact with the diode semiconductor devices and for the escape of air which is centrifugally separated from the liquid coolant during high speed rotation of the rectifier assembly. The rectifier assembly is compact, light weight and highly reliable.