Showing papers on "Rectifier published in 1997"

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 a DC/DC boost converter, a new three-phase three-switch three-level pulsewidth modulated (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 the control 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 six-switch two-level PWM rectifier system.

Power supply for light emitting diode array

Abstract: An apparatus (10) for supplying regulated voltage d.c. electrical power to an LED array (12) includes a rectifier (32) responsive to a.c power for generating rectified d.c. power and a power factor correcting and voltage regulating buck/boost switchmode converter (38) responsive to the rectified d.c. power for generating regulated voltage d.c. power to illuminate the LED array (12). A battery backup system (62) receives the a.c. power applied to the rectifier (32) for charging a rechargeable battery (66) and sensing an a.c. power failure. A switch-over relay (82) is connected between the battery backup system (62) and the rectifier. Upon sensing a failure of the a.c. power, the battery backup system (62) controls the switch-over relay (82) to connect the battery backup system (62) to the rectifier (32) to provide d.c. power to the switchmode converter (38) to illuminate the LED array (12). A half wave power detector (88) causes the apparatus (10) to reduce regulated d.c. power to dim the LED array (12).

A new control strategy for voltage type PWM rectifiers to realise zero steady-state control error in input current

Abstract: In this paper, a new simple control strategy for AC input current of voltage-type pulsewidth modulation (PWM) rectifiers which can eliminate the steady-state control error completely is proposed. This control method requires neither the instantaneous value of the supply voltage nor any accurate circuit parameters on the AC side of the rectifier. Thus, a robust operation against the variation of the circuit parameters can be achieved. In the proposed control system, a digital resonant element implemented by a digital signal processor (DSP) is introduced as a feedback controller. The digital resonant element exhibits a function similar to an integrator for the fundamental frequency components. Thus, it can eliminate the steady-state control error of the input current completely, The principle of the proposed control method is discussed, and its effectiveness is shown theoretically. The detailed method of the implementation of the lossless digital resonant element is explained. The effects of the harmonics in the supply voltage on the AC input current waveform are clarified. To confirm the effectiveness of the proposed control method, some experimental results from two laboratory test systems are shown.

Review of high-performance three-phase power-factor correction circuits

Abstract: This paper reviews progress in topology, control, and design aspects in three-phase power-factor correction (PFC) techniques. Different switching rectifier topologies are presented for various applications. Representative soft-switching schemes, including zero-voltage and zero-current switched pulsewidth modulated (PWM) techniques, are investigated. Merits and limitations of these techniques are discussed and illustrated by experimental results obtained on prototype converters. Control and input filter design issues are also discussed.

Low power rectifier circuit for implantable medical device

Abstract: A low power switched rectifier circuit is realized using P-MOS and N-MOS FET switches that are turned ON/OFF at just the right time by a detector and inverter circuit (which form an integral part of the rectifier circuit) to rectify an incoming ac signal in a highly efficient manner. Parasitic diodes and transistors that form an integral part of the FET circuitry respond to and rectify the incoming signal during start up, i.e., when no supply voltage is yet present, thereby providing sufficient operating voltage for the FET switches to begin to perform their intended rectifying function. In the absence of an incoming ac signal, i.e., during the time between biphasic pulses, the rectifier circuit is biased with an extremely small static bias current; but in the presence of an incoming ac signal, at a time when the positive and negative phases of the incoming signal are to be connected to positive and negative supply lines, a much larger dynamic bias current is automatically triggered.

A unity power factor PWM rectifier with DC ripple compensation

Abstract: This paper presents a new topology for a pulsewidth modulation (PWM) rectifier which achieves unity power factor on the AC supply side and ripple reduction on the DC output side. The main circuit of this rectifier consists of a conventional PWM rectifier and a pair of additional switches. The switches and PWM rectifier are controlled such that the ripple current on the DC line is reduced, and unity power factor is achieved on the AC line. As a result, this circuit does not require a large DC capacitor or a passive LC resonant circuit. Furthermore, control of the additional switches and PWM rectifier requires only a simple control circuit. The effectiveness of this circuit was confirmed by experiments and analysis. The rectifier is useful for uninterruptible power systems (UPSs) and DC power supplies, especially for cases in which batteries are connected to the DC line.

Simulation of SiC High Power Devices

Abstract: The impact of SiC on high power devices and their applications is analysed using simulations in a very wide range of design voltages. First, a detailed presentation of the anisotropic form of the basic equations and of the physical models for 4H-SiC used in the simulations is given. Following that the application ranges of unipolar and bipolar devices in the domains of voltage and frequency are predicted in the case of IGBTs versus MOSFETs and PiN versus Schottky rectifiers based on comparisons of the on-state voltage and of the total losses. The application limit of the MOSFETs compared to IGBTs and of the Schottky rectifiers compared to PiN rectifiers is predicted to be about 4.5 and 2.5 kV, respectively, in the case of the 4H-SiC polytype. The impact of technological limitations of SiC is illustrated by the case of low channel mobility. The merits of SiC as compared to Si are illustrated by the case of a SiC rectifier operating together with a Si IGBT. Dramatically reduced turn-on losses are demonstrated. The superiority of SiC from the point of view of dynamic avalanche is predicted and illlustrated. Finally, some novel SiC switch structures are introduced in response to the reliability problems encountered in ordinary trench MOSFETs.

Implementation of single-phase boost power-factor-correction circuits in three-phase applications

Abstract: A three-phase rectifier employing three single-phase boost power-factor-correction circuits is analyzed. Each converter operates in the continuous conduction mode (CCM), which allows a high power factor and a small EMI filter. Current sharing is ensured by a common voltage loop driving the individual current loops of the three converters. A suitable circuit arrangement is devised to limit phase interaction. The zero-voltage-transition technique (ZVT) is successfully applied to each converter, in order to obtain zero turn on losses and soft turnoff of the freewheeling diodes. Results of a 1800-W 100-kHz experimental prototype are reported, which confirm the theoretical forecasts.

A four level inverter based drive with a passive front end

Abstract: Multilevel inverters are suited for high power drive applications due to their increased voltage capability. A four level inverter is able to synthesize better waveforms and attain higher voltages while reducing the device ratings. While converter device count and kVA are high, a conventional diode bridge rectifier is a low cost multilevel drive solution for the input rectifier if suitable inverter side DC voltage balancing schemes can be devised. This paper investigates the operation of four level rectifier/inverter based drives under commonly used modulation schemes. Link voltage balancing and output voltage capability are analyzed for a four level inverter. Simulation results are presented to verify the link voltage balancing strategy in the absence of any balancing action from the rectifier.

Voltage sag ride-through for adjustable speed drives with active rectifiers

Abstract: Adjustable-speed drives (ASDs) trip due to voltage sags, interfering with production and resulting in financial losses. In this paper, a methodology for incorporating voltage sag ride-through in the design of ASDs with active rectifiers is presented. The magnitude of the voltage sag for which ride-through can be provided is determined by the current rating of the active rectifier and load condition of the ASD, but a sag of any duration can be compensated for.

Full-wave rectifier and method of operation for a recognition system

Abstract: A full-wave rectifier circuit (70) includes a first transistor (N1) and a second transistor (N2) in combination to form a first transistor pair (N1 and N2) for minimizing the voltage drop between ground (88) and the transponder substrates. A third transistor (P1) and a fourth transistor (P2) operate in combination to form a second transistor pair (P1 and P2) for minimizing the voltage drop between the alternating current peak voltage (118 and 120) and the output voltage (VDD) of the full-wave rectifier (70). The first transistor pair (N1 and N2) and second transistor pair (P1 and P2) are controlled by alternating current voltage input signals (118 and 120). A series regulator circuit (70) decouples the first transistor pair (N1 and N2) and the second transistor pair (P1 and P2) from capacitive loads (C1 and C2) of the full-duplex transponder circuitry (14).

Contactless communication system for exchanging data

Abstract: The terminal includes a coil co-operating with a data transmitter/receiver. The portable object includes a remotely powered electric circuit including: a coil for picking up the modulated magnetic field from the terminal or for responding by producing modulated disturbance of the magnetic field; a converter including a rectifier stage and a filter stage transforming the magnetic field picked up by the coil into a DC power supply voltage; and a data transmitter/receiver, the receiver including a demodulator for demodulating the amplitude of the signal picked up by the coil, the amplitude demodulator operating on the signal output by the rectifier and filter stages. Each of the coils forms a portion of a tuned resonant circuit radiating the field in free space. The amplitude modulation is a low depth modulation, with a modulation ratio that is typically less than or equal to 50%.

Induction motor drive system for low power applications

Abstract: This paper investigates the utilization of three different configurations of induction motor drives to implement low-cost systems for low-power applications The static power converter side is implemented by a single-phase rectifier cascaded with a four-switch inverter Three different types of induction machines are supplied with the static power converter In the first configuration, a standard three-phase induction machine is employed The second configuration also employs a standard three-phase induction machine, but only two of three windings are used In the third configuration, a standard two-phase induction machine is employed Simulation and experimental results are provided to illustrate the operation of the systems

Minimising rotor losses in high-speed high-power permanent magnet synchronous generators with rectifier load

Abstract: In an early stage of the design of a high-speed 1400 kW synchronous generator with permanent magnet excitation and loaded by a rectifier, it became apparent that rotor losses are a major problem. The stator currents cause asynchronous components in the air-gap field. Analysis shows that a modified polyphase system reduces the number of these components. An approximate solution for the rotor losses caused by the asynchronous field components has been derived. The formulae show the effects of machine dimensions and harmonics and the effect of a conducting shield in the rotor. The main purpose of the study is to have a tool for making an early choice among several stator winding configurations. A modified nine-phase system, combined with a shield around the permanent magnet rotor, is a prospective option.

Method and apparatus for damping ringing in self-driven synchronous rectifiers

Abstract: Apparatus and method for eliminating cross conduction of self-driven synchronous rectifiers in power converters caused by non-idealized ringing of parasitic capacitances and inductors. In an exemplary embodiment, the apparatus includes synchronous rectifiers or some hybrid topology having at least one synchronous rectifier coupled to a damping circuit having at least one switching device. The switching device is activated (ON) at a time when at least one of the synchronous rectifiers is supposed to remain inactive (OFF). Accordingly, when the switching device is ON, the device effectively dampens any ringing present at the synchronous rectifier that may cause the rectifier to inappropriately transition ON. The damping circuit of the present invention utilizes the same signals present to control the synchronous rectifier(s) and requires no additional control circuitry. Additionally, the damping circuit dramatically improves the efficiency of self synchronous power converters and is topology independent.

A technique for reducing rectifier reverse-recovery-related losses in high-voltage, high-power boost converters

Abstract: A circuit technique that reduces the boost power converter losses caused by the reverse-recovery characteristics of the rectifier is described. The losses are reduced by inserting an inductor in the series path of the boost switch and the rectifier to control the di/dt rate of the rectifier during its turn-off. The energy from the inductor after the boost switch turn-off is returned to the input or delivered to the output via an active snubber. The same technique can be extended to any member of the PWM power converter family.

Merits and limitations of full-bridge rectifier with LC filter in meeting IEC 1000-3-2 harmonic-limit specifications

Abstract: The feasibility of the single-phase, full-bridge rectifier with an LC filter to meet the IEC 1000-3-2, class-D specifications is assessed. It is found that this passive LC-filter approach can meet the required specifications if a proper inductance value of the filter choke is selected. Choke design considerations and performance evaluation results that include the power loss, volume, and weight estimates for applications with power levels between 75 and 600 W are presented.

Power factor correction of non-linear loads employing a single phase active power filter: control strategy, design methodology and experimentation

Abstract: This paper presents a technique for single phase power factor correction of nonlinear loads employing an active power filter. The current control strategy is the same used in the boost pre-regulator, which is the average current mode technique. The paper focuses on the design methodology and the analysis of the control strategy which allows the compensation of harmonics and phase displacement of the input current, for single and multiple nonlinear and linear loads. Simulation results of an active filter controlling a single load, which consists of a 1600 W rectifier with a capacitive filter, and a multiple load, which consists of a 800 W rectifier with a capacitive filter and a 800 W AC chopper, are provided. Experimental results of an active filter controlling a 400 W rectifier with a capacitive filter, a 800 W AC chopper and a 580 W multiple load, which consists of a rectifier with a capacitive filter and an AC chopper, are presented.

Electronic ballast circuit

Abstract: An electronic ballast circuit includes an input section which rectifies, power factor corrects and filters an AC input voltage to provide a rectified signal. The electronic ballast circuit also includes an inverter section which receives the rectified voltage and switches the rectified voltage to provide an AC signal to a resonant load circuit. The input section includes a resonant tank circuit which provides a high frequency current to the inverter to soft switch the switches within the inverter. In the input section, an inductor is placed on the AC side of a diode bridge rectifier advantageously allowing the removal of several prior art ballast circuit components since placing this portion of the power factor correction (PFC) circuit within the input circuit on the AC side of the diode bridge rectifier allows the bridge rectifier to perform both the rectification and current blocking functions. Advantageously, this reduces the cost of the electronic ballast circuit and increases its reliability since less components are required. In addition, the switching frequency of the switches is controlled to regulate the input current, while the switching duty cycle is independently controlled to regulate the output power.

Discharge lamp driving circuit having resonant circuit defining two resonance modes

Abstract: An improved discharge lamp driving circuit of a charge-pump type capable of suppressing a ripple in an envelop of a lamp current at the time of dimming the lamp or at a low environmental temperature. The circuit includes an inverter having switching elements Q1 and Q2 for converting a voltage across a smoothing capacitor Ce into a high frequency power which is applied through a resonant circuit to the discharge lamp Ld. A capacitor Cin is connected to one end of the resonant circuit to vary a DC voltage of the output of the rectifier in accordance with a varying instantaneous value of the high frequency current or voltage appearing in the resonant circuit. A control circuit is provided to give a control signal for alternately turning on and off the switching elements Q1 and Q2. A feedback circuit FB is provided to modulate the control signal within a permissible range given to the control circuit in such a manner as to adjust the timing of turning on and off the switching elements Q1 and Q2 in a feedback manner based upon a lamp current detected by a current sensor SI, for reducing the ripple in the lamp current. A mixer MX is included to compensate for the lamp current in consideration of a dimmer signal Dim of dimming the lamp in order to suppress the ripple which would otherwise increase due to the dimming of the lamp.

Power factor control for switched mode rectifiers with improved representing of currents in EMI capacitive elements

Abstract: A power factor correction system with an EMI line filter at the input includes circuitry to sense the capacitor current of the EMI filter to improve the accuracy of the power factor enhancement. The circuitry consists of a current sensing means connected after the EMI filter, and a voltage sensing capacitor which derives its input signal from a pair of diodes separate from the conventional 4-diode rectifier bridge, which are connected either before or after the EMI filter. The current-sensing means, which may be a resistor, and the voltage-sensing capacitor are tightly coupled to the current control loop of the power factor correction system to compensate for the current in the EMI filter capacitors.

A 0.5mW passive telemetry IC for biomedical applications

Abstract: The radiated power received by a small coil in implantable telemetry systems is less than a milliwatt. This requires a very efficient RF to DC converter, as well as the lowest possible power consumption for the biomedical sensor and data acquisition/transmisson system. This paper describes the design of a BiCMOS integrated circuit that includes a low noise amplifier, a lowpass notch filter, an A/D converter, voltage doubler/rectifier as well as a low power voltage regulator. The entire system, including the 1.7kΩ MR bridge sensor, consumes only 520µW average power @3V.

Power supply input circuit for field instrument

Abstract: A field instrument (10) includes an input circuit (26) having a transistor bridge rectifier (Q1, Q2, Q3, Q4) which is couplable to a power supply. The transistor bridge rectifier (Q1, Q2, Q3, Q4) is configured to provide power from the power supply to a remainder of the field instrument (10).

A novel RC model of capacitive-loaded parallel and series-parallel resonant DC-DC converters

Abstract: A novel analytical methodology is proposed and applied to investigate the steady-state processes in voltage-fed parallel and series-parallel resonant DC-DC power converters with a capacitive output filter. In this methodology, the rectifier, output capacitor and load are replaced by an equivalent circuit which includes a capacitor and resistor connected in parallel. Excellent agreement was obtained when comparing the numerical values calculated by the proposed model to cycle-by-cycle SPICE simulation and to the numerical results of earlier studies.

Internally programmable modular power supply and method

Abstract: An internally programmable power supply for use with an AC input voltage supplied to an input terminal for producing a DC output voltage. At least one power conversion module is providing having an input and an output. The input of the at least one power conversion module is adapted to be connected to the AC input. The at least one power conversion module includes rectifier means for converting the AC voltage to a DC voltage and a filter to provide the DC output voltage. A digital controller is connected to at least one power conversion module and includes a feedback network having a plurality of feedback components for forming a feedback loop. A microprocessor is provided and a keyboard accessible to the user is coupled to the microprocessor. A logic device is coupled to the microprocessor and is provided with a logic programming interface. Switches couple the logic device to the plurality of feedback components and are used for selecting feedback loops components at the request of the user to permit tailoring of the power supply phase and frequency response to a wide variety of user loads on the DC output.

Analysis of neural and fuzzy-power electronic control

Abstract: Current-controlled voltage-source inverters offer substantial advantages in improving motor-system dynamics for high-performance AC-drive systems. The controller switches follow a set of reference current waveforms. Fixed-band hysteresis and sinusoidal-band hysteresis controllers have been studied. Neural network and fuzzy-logic-based current-controlled voltage-source inverters are developed. The models and learning techniques have been investigated by simulation. The implementation of neural networks is described, and simulation results are presented. The new UPS (uninterruptible power supply) with a fuzzy-logic compensator is then proposed. The proposed fuzzy-logic compensator is used to prevent voltage drop from nonlinear loads. The total harmonic distortion (THD) of the proposed scheme is better than that of the conventional deadbeat control method for linear and nonlinear loads. Finally, the application of fuzzy control to DC-DC converters, operating at finite switching frequency, is studied. Several control methods currently used for buck, boost and buck/boost converters are compared to the fuzzy-converter control. The fuzzy-logic and neural-network controller for a unity power-factor rectifier are also discussed. The simulations presented show that the fuzzy-control method has better dynamic performance and less steady-state error.

Circuit for moderating a peak reverse recovery current of a rectifier and method of operation thereof

Abstract: In a power converter having a power train that includes a power switch and a rectifier for conducting forward currents from the power switch, a circuit for, and method of, moderating a peak reverse recovery current of the rectifier and a power converter employing the circuit or the method. The circuit includes: (1) a snubber circuit coupled to the rectifier and including a snubber inductor, a snubber capacitor and an auxiliary diode, the snubber inductor reducing the peak reverse recovery current of the rectifier and the snubber capacitor recovering energy stored in the snubber inductor and (2) an auxiliary switch, coupled in parallel with the power switch, that is activated when the power switch is transitioned from a conducting state to a non-conducting state to charge the snubber capacitor.

Operation of a motor vehicle alternator

Abstract: A conventional full wave diode bridge of an alternator is replaced with a full wave controlled rectifier bridge having controlled switches in place of diodes and the rectifier bridge is controlled in response to a third harmonic of the voltage generated by the alternator to synchronize the rectifier bridge with the alternator and to increase output power from the alternator The alternator includes a rotor having a field winding receiving a field current which is controlled up to a maximum field current for partial control of the output power produced by the alternator Power produced by the alternator is also controlled by introducing a phase angle between the phase voltages at the three output connections of the stator winding and the third harmonic up to a maximum or optimum phase angle To increase power output from the alternator, preferably the field current is increased up to a maximum before any phase angle is introduced between the phase voltages and the third harmonic Similarly, the phase angle is reduced to zero before the field current is reduced if power generated by the alternator is to be decreased

Low level, high efficiency DC/DC converter

Abstract: A DC-to-DC converter suitable for use in light-powered electronic systems. The DC electrical output from a solar cell is stepped-up in a chopper-type inverter that is driven by a gated oscillator. The output from the inverter is then rectified and is adapted to be applied to a load through a series connected switch whose on/off state is determined by the output from a voltage regulator. Connected between the rectifier and the series switch are energy storage capacitors which become charged when the series switch is open and which provide energy to the load when the series switch is closed. Feedback from the regulator circuitry controls the on/off state of the gated oscillator and, therefore, the energy delivered by the inverter. Further circuitry is provided for signaling a light transmitting device that the fiber-optic link delivering energy to the photo cell is intact.

PWM rectifier control with switching losses equally distributed among multiple switching devices

Abstract: Switching losses are distributed equally between multiple switching devices in a rectifier bridge (50) in which the rectifier bridge comprises at least a first pair of serially connected switching devices (56A, 56B) connected between positive and negative DC output buses (52, 54) and a second pair of serially connected switching devices (58A, 58B) connected in parallel with the first pair of switching devices. Only one of the switching devices in each pair of switching devices is pulse width modulated at any time at a frequency substantially higher than a frequency of the AC power applied to the rectifier bridge while another of the switching devices in each pair of switching devices is operated in synchronism with the waveform of the AC power applied to the bridge. Operation further involves periodically alternating the PWM operation of the switching devices between switching devices in each pair of switching devices so as to distribute the losses. Preferably, the process of alternating between PWM modulated switching devices occurs at zero crossings of the AC waveform so as to minimize transience generated in the switching process.