Showing papers on "Rectifier published in 1994"

Low loss synchronous rectifier for application to clamped-mode power converters

Abstract: A synchronous rectifier for use with a clamped-mode power converter uses in one embodiment a hybrid rectifier with a MOSFET rectifying device active in one first cyclic interval of the conduction/nonconduction sequence of the power switch and a second rectifying device embodied in one illustrative embodiment as a low voltage bipolar diode rectifying device active during an alternative interval to the first conduction/nonconduction interval. The gate drive to the MOSFET device is continuous at a constant level for substantially all of the second interval which enhances efficiency of the rectifier. The bipolar rectifier device may also be embodied as a MOSFET device. The subject rectifier may be used in both forward and flyback power converters.

Small-signal modeling and control of three-phase PWM converters

Abstract: The paper presents a systematic approach to small-signal modeling, and control design of three-phase PWM converters. The well established design procedures used in DC-DC converter control design, are adapted for the three-phase converter control based on the similarity in the small-signal dynamics of the three-phase converters and their DC-DC counterparts. The approach is especially beneficial in three-phase rectifier control, which is reduced to a single-input single-output system after closing the current loops. The modeling approach is verified on a 10 kW three-phase boost rectifier switching at 15.6 kHz with DSP control. A wide-bandwidth output voltage control loop is then designed based on the verified small-signal transfer functions. >

A new ZVS-PWM unity power factor rectifier with reduced conduction losses

Abstract: This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input AC voltage of 220 Vrms and an output voltage of 400 V/sub DC/ has been implemented in the laboratory. An efficiency of 97.8 % at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper. >

High frequency current conveyor precision full-wave rectifier

Abstract: The design of a precision full-wave rectifier using current conveyors is reported. The design uses a voltage reference circuit to clad the voltage excursions at the output of the rectifier during the zero crossings, which ensures that the usual large signal distortion associated with classical precision rectifiers is avoided. Measured rectifier performance using a 100 MHz current conveyor demonstrates good rectifier integrity at an operating frequency of 30 MHz.

Low voltage triggering semiconductor controlled rectifiers

Abstract: A new semiconductor controlled rectifier which may be used to provide on-chip protection against ESD stress applied at the input, output, power supply pins or between any arbitrary pair of pins of an integrated circuit is disclosed. The structure which has the lowest breakdown voltage for a given technology is incorporated into the SCR enabling a SCR trigger voltage determined by the lowest breakdown-structure.

A novel three-phase utility interface minimizing line current harmonics of high-power telecommunications rectifier modules

Abstract: Based on the combination of a three-phase diode bridge and DC/DC boost converter a new three-phase three-switch three-level PWM rectifier system is developed. It can be characterized by sinusoidal mains current consumption, controlled output voltage and low blocking voltage stress on the power transistors. The application could be, e.g., for feeding the DC link of a telecommunications power supply module. The stationary operational behavior, the control of the mains currents and of the output voltage are analyzed. Finally, the stresses on the system components are determined by digital simulation and compared to the stresses in a conventional PWM rectifier system. >

An analytical method for calculating harmonic currents of a three-phase diode-bridge rectifier with DC filter

Abstract: Commonly, three-phase diode bridge rectifiers with an LC filter at the DC side are often used to convert AC input into a DC voltage. It is well known that they generate large amounts of harmonic currents. This paper proposes an analytical method for calculating the harmonic currents for both the continuous and discontinuous current conductions. The equations for the harmonic currents are derived, taking into account the effects of the DC and AC side impedances. All the calculations are conducted only by algebraic calculation with high accuracy. The validity of the proposed method is demonstrated by comparison to the results of time simulation. >

A complete DC and AC analysis of three-phase controlled-current PWM rectifier using circuit D-Q transformation

Abstract: A recently proposed circuit P-Q transformation is used to analyze a three-phase controlled-current PWM rectifier. The DC operating point and AC transfer functions are completely determined. Most features of the power converter are clearly interpreted. They are: (1) the output voltage can be controlled from zero to maximum; (2) the system is equivalently an ideal current source in the steady state; (3) the system can be described as linear circuits; and (4) the input power factor can be arbitrarily controlled within a certain control range. >

Bio-operable power source

Abstract: A bio-operated implant system for implantation inside a human body. A piezoelectric generator in the form of a flexible sheet of poled polyvinylidene fluoride structurally that is attached in surface-to-surface contiguity with a skeletal number, which flexes with negligible elongation of its surface, is connected in circuit with a power consuming device such as a pacemaker, to a rectifier, and to a power storage device such as a condenser or battery. The generator generates in alternating voltage, which is rectified to direct current, which is supplied to the power consuming device on demand.

Synchronous rectifiers versus Schottky diodes: a comparison of the losses of a synchronous rectifier versus the losses of a Schottky diode rectifier

Abstract: A brief description of the differences in current flow through a MOSFET and a Schottky diode establishes the basis for a prediction of future device performance. Two different forward converter designs are used to illustrate the expected performance differences between the synchronous rectifier and Schottky diode designs. The current levels were selected to provide the designer with a more intuitive understanding of which applications benefit most from each type of design. >

Current source converter on-line pattern generator switching frequency minimization

Abstract: On-line PWM pattern generators for current source converters offer a number of control advantages over off-line optimized patterns. However, when implemented using the principles applying to voltage source inverter PWM pattern generators, the switching frequency is equal to: (a) the carrier frequency in standard carrier-based implementations and to (b) 2/3 the cycle frequency in space vector implementations. This paper shows that this frequency can be reduced to 1/2 of the respective frequencies. Two pattern generators are investigated: (a) a carrier based technique, namely the modified dead-band technique; (b) a space vector based technique, where the advantage is taken of the extra zero state available in current source converters. It is shown that a significant reduction of AC line current distortion is obtained with the modified dead-band technique for modulation indices greater than 0.4. Furthermore, with the two proposed pattern generators, there is no penalty on the distortion of the DC bus voltage. The principles of operation of the proposed schemes are explained. DSP implementation algorithms of the space vector scheme are given. Experimental results on a 5 kVA current rectifier and a 5 kVA current source inverter confirm the feasibility of the proposed pattern generators, and illustrate the input and output frequency spectra obtained. >

Control of front-end three-phase boost rectifier

Abstract: Modeling and control of a three-phase PWM boost rectifier is presented. A current controller in rotating coordinates assures unity input power factor and fast output voltage regulation. Sensitivity of stability margins to different loads is analyzed. Two typical loads, a DC-DC power converter and an inverter supplying an AC motor, are considered. Linear and nonlinear current controllers in the direct axis are compared. With the nonlinear controller, which employs load current feedforward, the rectifier sensitivity to load variations is greatly reduced and a single optimal output voltage compensator can be designed for all load conditions. Small-signal output impedance is significantly improved, and faster transient response is obtained. The results are illustrated with simulations of a practical 10 kW rectifier. >

Fast-response high-quality rectifier with sliding mode control

Abstract: A PWM rectifier including an uncontrolled rectifier and a Cuk converter stage driven by a sliding mode controller is described. Like other high-quality rectifiers, this solution allows low-distorted and in-phase line current. Moreover, due to the sliding mode control, fast and stable response is achieved, in spite of the large output filter. Control complexity is the same as that of standard current-mode controls. Converter analysis, design criteria, and experimental results are reported. >

Input Filter Design for PWM Current-Source Rectifiers

Abstract: Pulse-width modulated (PWM) rectifiers are increasingly used because they allow the elimination of low-order harmonics, and therefore a reduction in input filter components. Filtering requirements for PWM current-source rectifiers are usually satisfied through the use of low-pass LC input filters. This paper offers a systematic and user-friendly approach to choosing the filter components. Design of LC filters involves the positioning of the resonant frequency to meet the harmonic attenuation requirements (THD), and introducing damping at the resonant frequency to avoid amplification of residual harmonics. The problem is further complicated by considerations related to cost, power factor, voltage attenuation, system efficiency, and filter parameter variation. The systematic approach proposed in this paper focuses on PWM rectifiers, but can easily be extended to other classes of converters. Practical design considerations are detailed and design equations derived. Simulated results are presented to validate the design approach

Current control of a 3-level rectifier/inverter drive system

Abstract: The marriage of a three-level voltage source inverter with a force-commutated three-level rectifier is examined in this paper. Three-level inverters are capable of reducing the output current harmonics dramatically compared with typical two-level inverters whereas a three-level rectifier of this type allows nearly sinusoidal input currents at unity fundamental power factor on the utility side of the drive system. The dual capacitor split voltage bus can be regulated from either the inverter or rectifier side with neutral point balance maintained. This paper address the issues of neutral point voltage control and current regulation from both the rectifier and inverter perspectives. >

High-quality rectifier based on coupled-inductor Sepic topology

Abstract: A high-quality rectifier employing a coupled-inductor Sepic topology is described, featuring high-frequency insulation and low input current ripple. Moreover, sinusoidal and in-phase input current is obtained even with constant duty-cycle. The magnetic structure is simple and cheap, allowing considerable size and cost reduction. Converter analysis, design criteria of both power and control sections and experimental results are reported in the paper. >

Ac-dc converter

Abstract: The present invention provides an AC-DC converter in which an application range of an AC input voltage can be extended, keeping a voltage in a circuit from rising at a light load. In an AC-DC converter having a rectifier 3, a boost chopper 4 and a DC-DC converter 5, a PWM circuit 6, an one-shot multivibrator 7, a pulse synthesizer 8 and a comparator 9 are further arranged. The pulse synthesizer 8 generates a second pulse signal having a pulse width being narrower by a pulse width of the delay pulse VpD than that of the first pulse signal Vpa by means of the first pulse signal Vpa which the PWM circuit 6 output s and a delay pulse VpD generating in said one-shot multivibrator 7. The comparator 9 compares a voltage VC boosted up by the boost chopper 4 with a reference voltage VREF to stop generating the delay pulse when voltage VC drops below the reference voltage VREF .

A novel three-phase single-switch discontinuous-mode AC-DC buck-boost converter with high-quality input current waveforms and isolated output

Abstract: In this paper, a new three-phase single-switch AC-DC flyback converter system is presented. The system operates in the discontinuous mode. The simple structure of its power and control circuit, low mains current distortion, and resistive fundamental behavior, as well as the high-frequency isolation of the controlled output voltage, have to be pointed out. Besides the analysis of the stationary operating behavior, the dependencies of the peak values, average values, and rms values of the device currents, and of the maximum blocking voltages across the power electronic devices on the circuit parameters, are given as analytic approximations. The theoretical analysis is verified by digital simulation. >

Application of GTO voltage source inverter in a hybrid HVDC link

Abstract: This paper investigates the application of a GTO voltage source inverter in a two-terminal HVDC link, which is fed at the sending end by a line-commutated rectifier. This type of HVDC link may be applied when power transfer is predominantly unidirectional, especially to a weak AC system. The investigations are based on analytical studies and digital time-domain simulations with the Electromagnetic Transient program for DC systems (EMTDC). Control method and protection requirements are studied, together with dynamic behavior of the system following disturbances, e.g. DC fault, AC fault, start-up etc. The studies are aimed at exhibiting the technical feasibility of the proposed HVDC scheme. Need for further studies is pointed out when necessary. >

Temperature independent current conveyor precision rectifier

Abstract: A dual current conveyor based rectifier circuit with low temperature sensitivity is presented. The use of a DC current source to bias the rectifying diodes provides higher temperature stability than previously reported designs. In addition the output offset voltage is easily controlled and adjusted to a minimum low value. >

Piezoelectric transformer operating in thickness extensional vibration and its application to switching converter

Abstract: A new type of piezoelectric transformer (PT) power converter incorporating the ZVS technique is presented. A combination of the ZVS technique and the PT successfully achieves higher efficiency. For low output voltage, using half-bridge rectifier stage, the converter achieved 72% efficiency, at V/sub in/=80 V, V/sub o/=11.8 V, and P/sub o/=5 W. For medium output voltage, using full-bridge rectifier stage, the converter achieved 83% efficiency at V/sub in/=80 V, V/sub o/=40 V, and P/sub o/=10.7 W. >

Soft-switched single-switch three-phase rectifier with power factor correction

Abstract: Novel, zero-voltage-transition (ZVT) and zero-current-transition (ZCT) topologies of the single-switch three-phase boost power factor correction rectifier are proposed. The soft transition is achieved with a low-power auxiliary circuit employing an additional switch. The ZVT circuit is suitable for MOSFETs operating above 100 kHz, while the ZCT circuit can be used with IGBTs up to 50 kHz. Operation of the ZCT topologies is analyzed in detail and design guidelines are provided, The results are verified on a 4 kW, 50 kHz, experimental ZCT rectifier with IGBTs. Total harmonic distortion below 9% and efficiency above 95% were obtained. >

Regulated power supply having wide input AC/DC voltage range

Abstract: A regulated power supply automatically accommodates either a positive or negative polarity connection of a power source and without regard as to whether the source is an DC or an AC source, and accommodating a wide range of input voltage sources. The power supply circuit includes a source voltage conditioning unit which includes an input fuse section, a surge protection circuit, a power switch, and a filter rectifier section, coupled in circuit between a set of external power source connection terminals and a set of output terminals from which a rectified and filtered intermediate voltage is derived. An open fuse detector alerts servicing personnel to an open condition of a user-replaceable input fuse. A DC-DC converter section includes a start up supply circuit and a primary drive winding of a power transformer connected to receive the intermediate rectified voltage from the filter rectifier of the input section. The primary drive winding is coupled to power switch MOSFETs, which drive the primary winding drive current under the control of a pulse width modulator (PWM). The outputs of plural secondary windings are rectified, filtered, and regulated. The rectified output of a selected secondary winding is monitored by way of current limiting and voltage feedback circuits to control the operation of the PWM.

A three-phase regulated PWM rectifier with on-line feedforward input unbalance correction

Abstract: The analysis and design of a direct six-switch three-phase PWM rectifier, capable of correcting input unbalance, is presented. Based on the input source positive and negative sequence components, an unbalanced transfer matrix in terms of input phase voltages is derived. An online method is used to implement the transfer matrix function and generate the switch gating signals. As compared to other unbalance correction methods, the proposed approach is very simple to implement. It uses only a few discrete analog and digital components. The algorithm of the proposed approach is described in this paper, and results are verified from a 1 kVA breadboard set-up. >

Uninterruptible power supply with passing neutral, comprising a twin step-up chopper

Abstract: An uninterruptible power supply, with passing neutral, comprises a twin step-up chopper whose input is connected to a battery and to a rectifier circuit connected to the mains power system. The twin step-up chopper comprises a positive step-up chopper supplying a first output voltage between a positive DC output and neutral, and a negative step-up chopper supplying a second output voltage between a negative DC output and neutral. The control circuit of the twin step-up chopper comprises means for regulating imbalance between the output voltages of the positive and negative step-up choppers, suitable both for operation on the mains power system and for operation on the battery.

Pole-placement control of voltage-regulated PWM rectifiers through real-time multiprocessing

Abstract: The voltage-regulated pulsewidth-modulated (PWM) rectifier is prone to instability. The system can be stabilized by proportional-plus-integral feedback control, but its transient response is slow. This paper describes results of a study of digital control to improve the system dynamic response by pole placement through state feedback. The control algorithm is implemented for real-time operation by using a custom designed system of three high-speed microprocessors. Results from an experimental study with a 1 kW hardware laboratory model of the PWM rectifier shows that the dynamic response can be significantly improved even when the DC link capacitor is substantially reduced. >

Power factor correction circuitry

Abstract: A power factor correction circuit for use with a power supply. The power supply has an input for receiving an AC input signal, a rectifier for producing a rectified AC signal and an output stage for outputting a DC output signal for driving a load coupled to the output stage. The power factor correction circuit comprises an input port coupled to the rectifier for receiving the rectified AC signal; and an inductor coupled to the input port for storing energy in response to excitation by the rectified AC signal. The excitation of the inductor is controlled through the opening and closing of a switch by a controller. A capacitor is coupled to the inductor and charged by the energy stored in the inductor when the switch is opened to produce the DC output signal. The power factor correction circuit includes a diode for blocking the charge path between the input port and the capacitor and also allowing the controller to boost the charge level on the capacitor.

Motor drive circuit for pressure control of a pumping system

Abstract: This disclosure relates to a liquid supply system including a motor-pump unit designed for installation in a liquid supply such as a well or storage tank. The unit supplies the liquid to a supply pipe, and a pressure sensor connected to the pipe is operable to provide a control signal representative of the liquid pressure in the pipe. The motor is a variable-speed AC motor. A control for the motor is responsive to the control signal and actuates a power circuit to drive the motor at a speed adjusted to maintain the liquid pressure at a substantially constant value. The control circuit further includes means for turning off the power to the motor in the absence of flow through pipe, which does not require a flow sensor. The power circuit comprises a DC link including a rectifier and an inverter. The rectifier is located adjacent the pressure sensor; the inverter may be located adjacent the rectifier and the pressure sensor or in the casing of the motor-pump unit.

Technique for sensing inductor and DC output currents of PWM DC-DC converter

Abstract: The design, analysis and trade-offs of a novel method to sense the inductor and DC output currents of PWM converters are presented. By sensing and adding appropriately the currents in the transistor, rectifier and capacitors of a converter using current transformers, the waveforms of inductor and DC output currents can be reconstructed accurately while maintaining isolation. This method offers high bandwidth, clean waveform, practically zero power dissipation and simple circuit. The technique is applicable to all PWM converters in both continuous and discontinuous modes, and is most suitable for the implementation of current mode control schemes like hysteretic, PWM conductance control, and output current feedforward. This approach has been experimentally verified at a wide range of current levels, duty cycles, and switching frequencies up to 1.4 MHz. >

A unity power factor electronic ballast for metal halide lamps

Abstract: This paper proposes a unity power factor high-frequency electronic ballast for high-intensity discharge lamps. The ballast consists of an integrated, single stage power factor corrected rectifier, and a half-bridge high-frequency resonant inverter to interface the lamp with the DC bus. PWM control of the single stage rectifier produces sinusoidal input current at unity input power factor. The lamp is referenced to the supply neutral, without ohmic isolation, which is an important safety feature. To prevent acoustic resonance, a commonly encountered problem in high-frequency operation, the inverter is driven by a frequency modulated PWM strategy. The choices of the carrier frequency, the frequency modulation range, and the modulation sweep frequency are functions of selected lamp type. The proposed ballast is analyzed, simulated and experimentally verified with a 250 W metal halide lamp. >