Showing papers on "Precision rectifier published in 2000"

Modeling and control of a synchronous generator with an active DC load

Abstract: The design and analysis of a system consisting of a variable-speed synchronous generator that supplies an active DC load (inverter) through a three-phase diode rectifier requires adequate modeling in both time- and frequency-domains. As an example, the system's control-loops are difficult to design without an accurate small-signal model; at the same time, the system protection design requires large-signal transient modeling. A particularity of the described system is strong nonideal operation of the diode rectifier, a consequence of the large value of the generator's synchronous impedance. This nonideal behavior influences both steady-state and transient performance. This paper presents an average model of the system that accounts, in a detailed manner for the dynamics of the power source and the load, and for the effects of the nonideal operation of the diode rectifier. The model is nonlinear, but time-continuous, and can be used for large- and small-signal analysis. The developed model was verified on a 105 kW generator-set with inverter output, whose DC-link voltage control-loop design was successfully carried out based on the average model. It is shown that a high bandwidth is needed for this control-loop in order to achieve the proper impedance matching between the power source and the active electronic load.

Power reception circuits for a device receiving an AC power signal

Abstract: Power reception circuits employable in portable data devices (e.g., smart cards) to derive power and/or data from an input AC power signal (e.g., an ASK modulated carrier signal). In one embodiment, the power reception circuit comprises a power rectifier (120), a shunt rectifier (142) and a shunting element (132). The power rectifier (120) is adapted to rectify the input power signal, yielding a rectified output waveform. The shunt rectifier (142) is connected in parallel with the power rectifier (120). The shunting element (132) is connected to the shunt rectifier (142) and is operable to regulate an output voltage or current waveform produced at the output of the power rectifier (120). In another embodiment, the power reception circuit includes an analog circuit (610) for recovering data from a modulated carrier signal. A decoupling device (630) isolates the analog circuit (610) from impedance variations of a load. A shunt device (640) diverts undesired current from the load.

Method and control circuitry for a three-phase three-level boost-type rectifier

Abstract: A synchronized control method for a three-phase three-level boost-type rectifier with reduced input current ripple and balanced output voltages is disclosed. The proposed control allows simplifying the control circuit as much as possible without compromising the rectifier performance. In fact, besides simplicity, the control method featured synchronized command signals to de switching devices, minimized input current ripple, full controllability of the output voltage, dynamic balance of the output center point, constant switching frequency, simplified design of EMC filters, good transient and steady state performance, and low cost. The invention described first the most important configurations that the three-phase three-level boost-type rectifier may assume and studied the converter's operation. The concept involved for output voltage, input current, neutral point balance and control system design was presented.

Light emitting diode power supply

Abstract: A space efficient circuit arrangement for supplying power to an LED array, the power supply circuit ( 100 ) has a rectifier ( 105 ), a starting circuit coupled to the rectifier ( 105 ), a gate drive arrangement coupled to the starting circuit, and a resonant converter circuit ( 120, 125 ) coupled between the rectifier ( 105 ) and a resonant load circuit ( 135 ). The resonant load circuit includes a resonant inductance ( 150 ), a resonant capacitance ( 155 ) coupled to the resonant inductance ( 150 ), and a load connected in parallel to the resonant capacitance ( 155 ). A plurality of light emitting elements ( 170, 175 ) and a capacitor ( 160 ) define at least a portion of the load. All of the circuit components may be placed on the same circuit board as the light emitting elements ( 170, 175 ), thereby taking up less space in a traffic signal housing and making retrofitting a traditional incandescent lamp traffic signal easier.

A high-performance full-wave rectifier circuit

Abstract: A new circuit that enables basic operational amplifiers (op amps) such as the LM741 to produce precise full-wave rectification for frequencies up to and exceeding 100 kHz without waveform distortion is presented. The circuit is based on a standard op amp precise rectifier that is modified by the inclusion of a current conveyor to improve the rectifying process.

A comparative study of soft-switched CCM boost rectifiers and interleaved variable-frequency DCM boost rectifier

Abstract: In this paper, three single-phase, high-power-factor rectifier implementations were evaluated on a comparative basis. Specifically, a zero-voltage-switching continuous-conduction-mode boost rectifier, a zero-current-zero-voltage-switching continuous-conduction-mode boost rectifier, and an interleaved variable-frequency discontinuous-conduction-mode boost rectifier were compared with respect to their efficiencies, compliance with the EN61000-3-2 specifications, complexity, and costs. The comparisons were done for the single-phase input voltage of 90 V/sub RMS/-264 V/sub RMS/ and for 0-1.2 kW output-power range.

An efficient braking method for controlled AC drives with a diode rectifier front end

Abstract: Standard pulsewidth-modulated inverter-fed induction motor drives employ a diode rectifier bridge to supply AC power from the utility to the DC link. Although a diode rectifier is the most cost-effective solution, it does not permit reversing the power flow. This prohibits operating the machine in the regenerative braking mode for active deceleration. An innovative control method substitutes conventional hardware, such as an active front-end rectifier or a chopper controlled braking resistor in the DC-link circuit, by additional software that is implemented in the standard microprocessor control. The control algorithm maximizes the power losses in the machine and in the inverter. It enables regenerative braking operation of the induction motor at high torque. The algorithm conserves the high dynamic performance of a vector-controlled drive system.

New multilevel rectifier based on series connection of H-bridge cell

Abstract: A three-level pulse-width modulation (PWM) rectifier is proposed. The control scheme is based on general logic gates to generate a three-level voltage waveform. In comparison with the two-level PWM scheme, the three-level PWM scheme can reduce the electromagnetic interference, decrease voltage stress of power semiconductors, and increase the switching frequency. A capacitor voltage compensator is used to balance two DC bus voltages. Based on the proposed control algorithm, the current harmonics of the line meet the International Electrotechnical Commission 1000-3-2 limits. The power factor of the proposed rectifier is nearly unity. The control strategy of the proposed three-level rectifier illustrates its validity and effectiveness experimentally.

Synchronous rectifier flyback circuit for zero voltage switching

Abstract: The present invention relates a flyback circuit for zero voltage switching {ZVS} in continuous mode {CCM} and discontinuous mode {DCM}, which circuit minimized loss generated when electrifying parasitic diode of MOS transistor {MOSFET} that is secondary side switch of synchronous rectifier and which also enabled ZVS in whole range of discontinuous mode {DCM}. Particularly it contains a synchronous rectifier driver that delays the gate drive signal that is outputted from pulse width modulation part after which the driver compares it with reference voltage that is outputted from pulse width modulation part and then the driver amplifies result value so as to supply it as the drive signal for synchronous rectifier part, a level change device that drives the synchronous rectifier gate, changing the level of gate drive signal that is outputted from gate drive device, and an insulating transformer that transmits the drive signal that is outputted from synchronous rectifier driver, to the level change device side. Wherewith it inverts the output signal of the pulse width modulation part in driving the synchronous rectifier gate, resulting in minimization of loss occurred at time of electrification of parasitic diode of MOS transistor {MOSFET} that is secondary side switch so that it makes effect to enhance efficiency letting it perform zero voltage switching {ZVS} under fixed frequency condition in discontinuous mode {DCM}.

A three-phase voltage-type PWM rectifier with the function of an active power filter

Abstract: In recent years, harmonic pollution in electrical power systems due to nonlinear loads such as AC/DC power converters has become a serious problem. To eliminate or reduce harmonics in power systems, a number of methods have been developed and put into practice. Active power filters and PWM rectifiers are two typical examples of these methods. The active power filter and PWM rectifier have basically the same circuit configuration and can operate based on the same control principle. Therefore, one can design a power converter capable of both the active filter operation and PWM rectifier operation at the same time. Such a converter operates as a PWM rectifier to supply DC power to its own load and, at the same time, operates as an active filter to supply to the AC line a compensating current equal to the harmonic current produced by the nonlinear load connected to the same AC line. Here, a three-phase voltage-type PWM rectifier with the function of an active power filter is investigated.

Electromagnetic field receiving apparatus

Abstract: PROBLEM TO BE SOLVED: To expand operable region of an electromagnetic field receiving apparatus. SOLUTION: Antenna circuits 20, 21 receive electromagnetic waves transmitted from an electromagnetic field transmission apparatus 1. A rectifier circuit 22 acquires driving electric power for its own apparatus from the electromagnetic wave received at the antenna circuits 20, 21. A constant voltage circuit 23 converts the output voltage of the rectifier circuit 22 to a constant voltage. An impedance control circuit 31 repeats a control action which changes an impedance of its own apparatus so that the output voltage of the rectifier circuit 22 becomes equal to the desired voltage set value, thereby controls a quantity of received power from the electromagnetic field transmission apparatus 1.

Four-legged three-phase PFC rectifier with fault tolerant capability

Abstract: A four-legged three-phase PFC rectifier is proposed to handle unbalanced source voltage and to provide fault tolerant operation. The four-legged PFC rectifier is controlled by a three-dimensional space vector modulation (3D SVM) scheme, and runs in the overmodulation region when the source is unbalanced and/or a leg failure occurs. Modeling and control of the four-legged PFC rectifier are presented. Under unbalanced source, operation of the four-legged rectifier with three control strategies-equal current, equal resistance and constant power are analyzed. Two rectifier failure modes are studied: (1) entire leg fails; (2) active switches fail with the anti-parallel diodes still functional. It turns out that in both failure modes, the PFC rectifier can have an equal or higher than 2/3 of the rated output power level. The operation of the four-legged rectifier with 3D SVM is demonstrated by experimental results. The simulation results show that the proposed four-legged rectifier is advantageous over directly coupled three single-phase PFC rectifier and three-legged three-phase PFC rectifier.

A new concept for minimizing high-frequency common-mode EMI of three-phase PWM rectifier systems keeping high utilization of the output voltage

Abstract: Three-phase PWM rectifier systems in principle show a common-mode voltage with switching frequency between the mains neutral point and the center point of the output voltage. Without any counter-measures this leads to a high common-mode noise emission of the system and possibly to disturbances of the control unit of the converter being fed by the rectifier. In this paper a detailed discussion of the formation of the common-mode voltage for the VIENNA Rectifier I is given and a modified circuit topology which significantly reduces the switching frequency component of the common-mode voltage is given. The proposed circuit modification is applicable also to other three-phase PWM rectifier topologies. The filtering concept is analyzed by digital simulation and guidelines for the dimensioning of the filter components are given. The reduction of the common-mode noise is verified by EMI measurements taken from a 10 kW laboratory unit of a VIENNA Rectifier I. Finally, the advantages and drawbacks of the proposed filtering concept are compiled in the form of an overview.

General self-driven synchronous rectification scheme for synchronous rectifiers having a floating gate

Abstract: A self-driven synchronous rectifier circuit having synchronous rectifiers with floating gates for a power converter or signal transformer. The circuit comprises a transformer (49, 70) having a secondary winding with a first and second terminal, a first synchronous rectifier (SQ1) coupled to the first transformer secondary winding first terminal and having a control terminal floating relative to ground and a first device circuit coupled to the first synchronous rectifier floating control terminal and controlling the first synchronous rectifier. A first control signal is coupled to the first drive circuit, where the first control signal controls the first drive circuit as a function of a polarity reversal of a voltage across the first transformer (49, 70). A second synchronous rectifier (SQ2) is coupled to the first transformer secondary winding second terminal and has a control terminal floating relative to ground. A second drive circuit is coupled to the second synchronous rectifier floating control terminal and controls the second synchronous rectifier. A second control signal is coupled to the second drive circuit, where the second control signal controls the second drive circuit as a function of a polarity reversal of a voltage across the first transformer (49, 70).

Improving the operation of 3-phase diode rectifiers using an asymmetrical half-bridge DC-link active filter

Abstract: The PWM asymmetrical half-bridge is used to control the output current of a three-phase diode rectifier with a capacitor smoothed output voltage. The controlled-current function provided by the bridge improves the performance of the rectifier by lowering the low frequency ripple in the diode rectifier output current and by maintaining a balanced AC supply current when the AC supply voltage is unbalanced. The two-switch asymmetrical bridge can be designed with low per-unit voltage ratings, typically 15%, and can guarantee equal current sharing between parallel rectifiers. The higher conduction losses introduced by the bridge is offset by the improved diode rectifier performance, the low voltage devices used in the bridge, and the use of smaller L-C filter components. Balanced UPF sinusoidal supply currents can be obtained by using a three-phase bi-directional Y-switch and two asymmetrical half-bridges to separately control the output currents at both the diode rectifier output terminals. The asymmetrical bridge switches are exposed to only half the rectifier output voltage and the three-phase Y-switch has very low rms per-unit current ratings.

Full wave rectifier circuit using normally off JFETs

Abstract: A four terminal full wave rectifier circuit that can be used as a pin for pin replacement for the full wave diode rectifier circuit commonly used in DC power supply circuits. Two full wave rectifier circuits that can efficiently supply the DC currents required in both discrete and integrated circuits being operated at low DC supply voltages are disclosed. Both circuits utilize two n-channel, enhancement mode Junction Field Effect Transistors (JFET) and two p-channel, enhancement mode Junction Field Effect Transistors to replace the rectifier diodes used in a conventional full wave rectifier circuit. The forward voltage drop across each JFET is considerably smaller than the forward voltage drop of a conventional rectifier. In a first configuration, the JFETs are all symmetrical about the source and drain leads. Starter devices are connected between source and drain leads and current limiting devices are in series with the gate leads. The gate leads of the JFETs are connected to the input terminals of the circuit such that a full wave rectified version of the input signal is produced at the output of the circuit. In a second configuration, two asymmetrical n-channel and two asymmetrical p-channel JFETs are used to replace the four rectifier diodes found in a conventional full wave rectifier circuit. The gate of each JFET is connected to its source lead and a full wave rectified version of the input signal is then produced at the output of this circuit.

Clamping circuit and method for synchronous rectification

Abstract: A rectifier circuit having voltage clamping circuitry is disclosed. The rectifier circuit includes a transformer having a primary winding and a secondary winding and transistor switches each being connected to an end of the secondary winding of the transformer. The rectifier circuit further includes a first diode having an anode terminal connected to a first end of the secondary winding and a second diode having an anode terminal connected to a second end of the secondary winding. The cathode terminals of the first and second diodes are coupled to a capacitor. The energy stemming from voltage spikes and/or high frequency ringing appearing at the transistor switches due to parasitic effects is effectively absorbed by the first and second diodes and collected in the capacitor. The collected energy is recycled to control the operation of the transistor switches.

Design and implementation of a single phase three-arms rectifier inverter

Abstract: A high performance single phase three-arms PWM rectifier inverter is presented. A switching control approach for the common arm is proposed such that control of the rectifier arm and inverter arm can be designed independently. Variable structure control (VSC) executed with capacitor current control is developed to design the inverter. For the rectifier design, an instantaneous power feedback controller using filter theory is proposed to enhance the DC voltage regulator to reduce DC voltage fluctuation and minimise input current distortion. A 3 kVA system is implemented to confirm the effectiveness of the proposed approaches.

Externally-driven scheme for synchronous rectification

Abstract: A self-driven synchronous rectifier circuit (50) for a DC-DC power converter. The circuit comprises a primary transformer (16), a first synchronous rectifier (SQ1) coupled to the primary transformer (16), a second synchronous rectifier (SQ2) coupled to the primary transformer (16), an external drive circuit (18). The circuit (50) also comprises a plurality of switches (SQ3, SQ4) controllably coupled to second synchronous rectifier (SQ2). The external drive circuit (18) provides turn-off signaling for both synchronous rectifiers (SQ1, SQ2). Turn-on signaling provided for first synchronous rectifier (SQ1) by the primary transformer (16) turn-on signaling for second synchronous rectifier (SQ2) is provided by the external drive circuit (18).

Current-mode full-wave rectifier and vector summation circuit

Abstract: A current-mode full-wave rectifier and current-mode vector summation circuit are presented. They are implemented by utilising the square-law characteristics of MOS transistors in saturation. A two-input vector summation circuit using the proposed full-wave rectifier has been fabricated in a 0.8 /spl mu/m CMOS process. The experimental and simulation results confirm the feasibility of the proposed circuits.

Electronic power converter for triac based controller circuits

Abstract: A ballast circuit operable with a triac based controller circuit, the ballast circuit (100) includes a rectifier (115) configured for operative connection with an associated triac based circuit (110) for converting AC current to DC current, a capacitor assembly (137) coupled to the rectifier (115), a first connection (150) between the rectifier and the capacitor assembly (137), a converter (153) coupled to the rectifier (115) for converting the DC current to AC current, a gate drive arrangement coupled to the converter for controlling the converter (153), a resistance-inductance circuit (163) coupled to the converter (153), and a second connection (165) between the capacitor assembly (137) and the resistance-inductance circuit (163). The converter (153) induces AC current in the resistance-inductance circuit (163).

A frequency-domain analytical model of an uncontrolled single-phase voltage-source rectifier

Abstract: The harmonic currents generated by the single-phase rectifier are well known. As the levels of these currents become larger, the use of power conditioners, such as shunt active filters, to lower the levels is becoming more attractive. In order to analyze the interaction between the condition, AC system and rectifier, it is necessary to have an accurate model of the rectifier. This paper describes a frequency-domain analytical model of the single-phase rectifier. The model includes the dominant frequency transfer mechanisms. These are the direct transfer and that due to the modulation of the switching instants. A small-signal linearized analysis is presented and the behavior predicted is confirmed by perturbation analysis using time-domain simulation. Accurate results are obtained, and the importance of including the switching instant modulation is shown.

Unified constant-frequency integration control of three-phase standard bridge boost rectifier

Abstract: In this paper, a three-phase six-switch standard boost rectifier with unity-power-factor-correction is investigated. A general equation is derived that relates input phase voltage and duty ratios of switches in continuous conduction mode. Based on one of solutions and using one-cycle control, a unified constant-frequency integration (UCI) controller for power-factor-correction (PFC) is proposed. For the standard bridge boost rectifier, unity-power-factor and low total-harmonic distortion (THD) can be realized in all three phases with a simple circuit that is composed of one integrator with reset along with several flips-flops, comparators, and some logic and linear components. It does not require multipliers and three-phase voltage sensors, which are used in many other control approaches. In addition, it employs constant switching frequency modulation that is desirable for industrial applications. The proposed control approach is simple and reliable. Theoretical analysis is verified by simulation and experimental results.

Power source and arrangement for restricting the short-circuit current or rectifier

Abstract: A power source with an arrangement for restricting short-circuit current includes at least a primary-side switch block, a transformer unit and a rectifier. The rectifier includes switching transistors for rectifying the secondary side of the transformer. Operation of the rectifier depends on a control from a pulse-forming part of the primary-side switch block. Control for the switching transistors in the rectifier is interrupted when the output current of the rectifier exceeds a limit value. At least one other switch element is arranged parallel to each of the switching transistors in the rectifier to realize a secondary-side rectification in an overload situation.

Implementation of a three-level rectifier for power factor correction

Abstract: In this paper, a new single-phase switching mode rectifier (SMR) for three-level pulse width modulation (PWM) is proposed to achieve high input power factor, low current harmonics, low total harmonic distortion (THD) and simple control scheme. The mains circuit of the proposed SMR consists of six power switches, one boost inductor, and two DC capacitors. The control algorithm is based on a look-up table. There are five control signals in the input of the look-up table. These control signals are used to control the power flow of the adopted rectifier, compensate the capacitor voltages for the balance problem, draw a sinusoidal line current with nearly unity power factor, and generate a three-level PWM pattern on the AC side of adopted rectifier. The advantages of using three-level PWM scheme compared with two-level PWM scheme are using low voltage stress of power switches, decreasing input current harmonics, and reducing the conduction losses. The performances of the proposed multilevel SMR are measured and shown in this paper. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental results from a laboratory prototype.

Synchronous rectifier controller for power supply systems with high power switch and high efficiency

Abstract: The present invention discloses an AC-to-DC converter that includes a transformer having a primary side for inputting an input signal and a secondary side for outputting an output signal. The AC-to-DC converter further includes a synchronous rectifier controller connected to the secondary side for controlling a synchronous rectifier (SR) switch on the secondary side for generating the output signal. The SR switch is implemented as a MOSFET transistor with a gate connected to the synchronous rectifier controller. The synchronous rectifier controller further includes a plurality of circuit elements for turning off the SR switch before a main switch of the transformer is turned on. The synchronous rectifier controller further turns on the SR switch when the main switch of the transformer is turned off. The synchronous rectifier controller controls the SR switch and turns it off with a precisely controlled dead time before the main switch of the transformer is turned on.

New ZCS turn-on and ZVS turn-off unity power factor PWM rectifier with reduced conduction loss and no auxiliary switches

Abstract: A ZCS turn-on and ZVS turn-off unity power factor PWM rectifier, which features soft switching with no auxiliary switches and reduced conduction losses is presented. The ZVS and ZCS switching are achieved by using a simple commutation circuit with no auxiliary switches, and reduced conduction losses are achieved by employing a single converter instead of a typical front-end diode rectifier followed by a boost rectifier. Furthermore, thanks to features such as simple PWM control at constant frequency. Low switch stress and low VAr rating of commutation circuits, it is suitable for high-power applications. The principle of operation is explained and analysed, and the design considerations and experimental results of the new converter are included.

Frequency converter with an intermediate buck-boost converter for controlling an electric motor

Abstract: The frequency converter is provided for an electric motor and comprises a rectifier, an intermediate circuit and an inverse rectifier which are connected with respect to circuiting technology via a control and regulation circuit. In the inverse rectifier to each motor phase there are allocated at least two electronic switches, one for the side conducting the higher potential and one for the side conducting the low potential. The intermediate circuit is formed as an active intermediate circuit and contains a Buck-Booster converter. It is controlled such that the voltage at the output of the intermediate circuit with respect to magnitude is always smaller than that at the input. By way of this inexpensive components may be used in the inverse rectifier and in particular also in the control and regulation circuit.

Very low-voltage class AB CMOS precision voltage and current rectifiers

Abstract: Simple class-AB CMOS voltage and current precision rectifier circuits that operate from a single supply close to a transistor's threshold voltage are introduced. The current rectifier has output voltage swings comparable to the supply voltage and the voltage rectifier has wide input and output swings. Simulations of both rectifiers operating at 20 MHz are shown. Experimental results of a test chip are presented that verify the proposed circuits. A full wave precision rectifier based on the proposed rectifier cells is discussed.

Synchronous rectifier drive mechanism for resonant reset forward converters

Abstract: A resonant reset forward converter including a gate drive mechanism for controlling the conduction periods of a free-wheeling rectifier on the secondary side of the converter is disclosed. The gate drive mechanism is operative to turn on the free-wheeling rectifier at the beginning of the forward power cycle, maintain the free-wheeling rectifier in the on state during the transformer core reset and dead periods, and provide for rapid discharging of the freewheeling rectifier at the beginning of a subsequent forward power cycle.