Showing papers on "Precision 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.

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.

New 24-pulse diode rectifier systems for utility interface of high-power AC motor drives

Abstract: This paper proposes two new passive 24-pulse diode rectifier systems for utility interface of pulsewidth modulated (PWM) AC motor drives. The first approach employs an extended delta transformer arrangement, which results in near equal leakage inductance in series with each diode rectifier bridge. This promotes equal current sharing and improved performance. A specially tapped interphase transformer is then introduced with two additional diodes to extend the conventional 12-pulse operation to 24-pulse operation from the input current point of view. The proposed system exhibits clean power characteristics with fifth, seventh, eleventh, thirteenth, seventeenth, and nineteenth harmonics eliminated from the utility line currents. The second scheme is a reduced voltampere approach employing autotransformers to obtain 24-pulse operation. The voltampere rating of the polyphase transformer in the second scheme is 0.23P/sub 0/ (PU). Detailed analysis and simulations verify the proposed concept, and experimental results from a 208-V 10-kVA rectifier system are provided.

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.

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.

A predictive instantaneous-current PWM controlled rectifier with AC-side harmonic current reduction

Abstract: A new single-phase bridge rectifier controlled by a predictive instantaneous-current PWM control scheme for reducing AC-side harmonic currents and improving power factor is proposed. The rectifier can operate at the unity displacement power factor and has fast response to an input signal as a current reference. The effect of the DC-side voltage ripples is taken into account. The paper describes three digital control schemes for such rectifiers and presents experimental and simulation studies on steady-state and dynamic performances of the rectifier. The effectiveness of the control schemes is confirmed by experiments and simulations. The proposed rectifier can be used for applications such as UPS systems and static VAr compensators.

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).

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.

Current mode control of a full bridge DC-to-DC converter with a two inductor rectifier

Abstract: In this paper, both peak current mode and average current mode control schemes are investigated as applied to a full bridge PWM converter with a two inductor rectifier. The two inductor rectifier circuit offers reduced secondary side current rating and is most suitable for high current applications. With current mode control, the two inductor rectifier is modeled as two parallel connected buck converters.

A simplified model of a variable speed synchronous generator loaded with diode rectifier

Abstract: This paper presents a new, time-continuous, nonlinear model of a synchronous generator loaded with diode rectifier. The developed model is used for study of a system consisting of two synchronous generators (exciter and main generator) connected in cascade, each loaded with a diode rectifier. Speed of the system is not constant, but varies as the load changes. Some particularities of this system are described and reasons for nonsinusoidal generator voltage and current waveforms are discussed. Simplified equations of the system are developed based on first harmonic assumption, generator space vector diagram and losslessness of a diode bridge. Model validity for large signal (transient) analysis is confirmed through comparison with the switching model simulation results and with measurements. Linearization of the model and application to control purposes through small signal analysis is considered.

Class-E rectifier using thinned-out method

Abstract: A new control method of a class-E rectifier is presented, which regulates the output voltage or power with elimination of the voltage pulse of the rectifier at a constant rate. When the class-E rectifier controlled by this method is used in a class-E DC/DC power converter, both the inverter and rectifier operate under zero-voltage-switching conditions. Since the rectifier is controlled by a synchronized switch, it achieves the following advantages: (1) power efficiency for low-output voltage is improved; (2) output voltage and power are controllable at a fixed operating frequency; and (3) switching noise can be reduced. Additionally, this method is suitable for applications in which the output voltage or power are changed immediately because the output voltage and power are controlled by means of replacements of pulse patterns. The output characteristics of the rectifier are analyzed under a condition that the amplitude of the input current is constant. Experimental results show good agreement with the theoretical results.

Low voltage MOS-transistor-only precision current peak detector with signal independent discharge time constant

Abstract: A low voltage precision peak detector for current signals is presented. It detects a positive peak current and holds accurately the detected current even in the presence of large negative current peaks. Peak detection of a 500 kHz signal within 3% is possible in a dynamic range of 40 dB with a 2 V supply voltage and over 60 dB with a 5 V supply voltage. Additional circuitry is also designed to achieve a signal independent and adjustable discharge time constant.

Excimer laser having power supply with fine digital regulation

Abstract: An excimer laser system having a laser chamber containing elongated electrodes and an excimer laser gas and a high voltage pulse power supply having fine digital regulation for supplying high voltage electrical pulses to the electrodes. The high voltage pulse power supply includes a power supply and a magnetic switch circuit for compressing and amplifying the output of the power supply. The power supply includes a silicon controlled rectifier which provides a direct current output to an inverter which converts the output of the silicon controlled rectifier to high frequency alternating current which is in turn amplified by a step up transformer. An output stage diode rectifier in combination with an inductor converts this high frequency high voltage current back to direct current. A control board comprising electronic circuits controls the power supply to provide high voltage pulses at a frequency of at least 1000 Hz. A voltage feedback circuit detects the voltage output of the output stage rectifier and provides a voltage output signal to the control board and a current feedback circuit detects charging current flowing in the output stage diode rectifier and provides a charging current signal to the control board. A digital command control for providing command control to said control board. A preferred embodiment of the present invention achieves very precise regulation with the use of differential instrumentation amplifiers in the feedback circuits and by reducing the charging current near the end of the charging cycle of each pulse.

Short circuit protected DC-DC converter using disconnect switching and method of protecting load against short circuits

Abstract: A four-terminal MOSFET, in which no combination of the source, drain, body and gate terminals are permanently connected together, is used as a synchronous rectifier capable of blocking an excessive current in a switching mode DC--DC converter resulting from a short-circuited load. In an N-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the inductor in the DC--DC converter and is grounded when an overcurrent condition is detected. In a P-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the converter output and is connected to the inductor when an overcurrent condition is detected. In addition, the voltage output by the inductor may be clamped using a zener diode or a snubber capacitor. A MOSFET body bias switching circuit is driven by overcurrent detection circuitry that may also be used to turn off the synchronous rectifier MOSFET gate.

Modelling and design of a reversible three-phase switching mode rectifier

Abstract: A reversible three-phase switching mode rectifier consisting of a four-active-switch and without current sensor is proposed. To achieve controllable power factor, clean sinusoidal input current, adjustable DC output voltage, and bidirectional power flow capability, a closed-form pulse width modulation (PWM) duty cycle function is derived. The popularly used state space averaging technique is extended for modelling the reversible three-phase four-active-switch rectifier. The space vector representation technique is then used to simplify the modelling process without sacrificing accuracy and valid frequency range. Both steady-state and small signal analyses are made. Results show that the proposed closed-form control law for the rectifier can indeed achieve the desired property. Moreover, the rectifier also possesses a bidirectional power flow capability, which is useful for many applications. Finally, a prototype hardware circuit was constructed and experimental results are presented for demonstration. Guidelines for determining the LC parameters and the PI controller gains are described briefly in the text.

Electronic ballast with lamp current valley-fill power factor correction

Abstract: An electronic ballast (10) for powering at least one gas discharge lamp (30) includes a rectifier circuit (100), a line blocking rectifier (220), a bulk capacitor (240), an inverter (300), an output circuit (400), and a charging circuit (500). Charging circuit (500) is coupled between the output circuit (400) and the bulk capacitor (240) and provides operating current to the bulk capacitor (240). Charging circuit (500) also protects lamp life by preventing excessive flow of DC current in the lamp (30) following application of AC power to the ballast (10). In a preferred embodiment, charging circuit (500) includes a DC blocking capacitor (510), a lamp current blocking rectifier (530), and a charging rectifier (540).

Improvement of Input Current Waveforms of a Single Phase Diode Rectifier by Passive Devices

Abstract: This paper proposes a high power facter rectifier composed of only passive devices. It consists of a single phase diode rectifier having a L-C resonant circuit in parallel with the diode output and a series reactor to pumping up the charge stored in the resonant circuit capacitor. It enables wide current conduction width and decreases its peak value. As a result, harmonics in the input current is decreased and the power factor is improved, which will be satisfied the harmonic regulation enforced in near future.The absence of switching devices as FETs makes high reliability, high efficiency, strength to over load, and no radio noise. In this paper, it is shown input harmonic current components, output voltage, and other characteristics by charts for circuit design. Input power factor of 98.4%, the total harmonic distortion of 17.4%, and the efficiency of 93.3% are confirmed by experiment with rated condition of 1.0kW, 100V system.

Phase-shift power supply

Abstract: Power supply apparatus according to the present invention may comprise a direct current source and a phase-shift converter circuit connected to the direct current source A rectifier is connected to the output of the phase-shift converter circuit and rectifies a modulated output signal produced by the phase-shift converter circuit An average current sensor connected to the rectifier senses the time average current in the rectifier and produces an average current feedback signal A control device connected to the average current sensor and to the phase-shift converter circuit is responsive to the average current feedback signal and operates the phase-shift converter circuit in accordance with the average current feedback signal

Analysis and design of single-controlled switch three-phase rectifier with unity power factor and sinusoidal input current

Abstract: This paper describes a new low-cost three-phase AC-DC high-power/low-harmonic-controlled rectifier and its analysis, design, and performance. The circuit consists of a three-phase diode-bridge rectifier, followed by a boost stage containing only one switch and one boost inductor. The proposed converter is used to automatically draw sinusoidal input-current waveforms with high efficiency. This is achieved with discontinuous-input voltage to the rectifier and with a discontinuous-inductor-current mode of operation of the boost converter. By using a simplified single-phase model and symbolic analysis method, analytical equations are obtained and used for design.

A new modulation technique for reducing the input current harmonics of a three-phase diode rectifier with capacitive load

Abstract: In this paper, a new technique for shaping the line current and reducing the total harmonic distortion in a three-phase bridge rectifier, feeding a capacitive load, is presented. Using the topology of a three-level three-switch pulsewidth modulated (PWM) rectifier, a new control technique has been implemented. The main objective here is to minimize the total harmonic distortion (THD) of the line current under different load conditions (20%-100% of full load). A review of the problems inherent in a bridge rectifier feeding a capacitive load and the possible solutions are first presented. Subsequently, the analysis of the new circuit and the control technique used are described, along with simulation results. Finally, the experimental results on a 1.6 kW prototype are presented.

Snubber circuit for a rectifier and method of operation thereof

Abstract: For use in a power converter having a rectifier coupled to an output thereof, a snubber circuit including an energy storage device coupled to the rectifier that moderates a voltage across the rectifier and a method of moderating the voltage. In one embodiment, the snubber circuit includes: (1) a first switch that regulates a voltage across the energy storage device, (2) an inductor, coupled to the first switch, that provides a discharge path for energy stored in the energy storage device when the first switch is conducting and (3) a second switch that recovers energy stored in the inductor to the output when the first switch is not conducting. The snubber circuit thereby reduces voltage stress across the rectifier during a current limit mode of operation.

AC/DC boost converter

Abstract: A voltage doubler rectifier circuit which can be switched to different mains voltages. The circuit includes two pairs of series-coupled diodes and respectfully arranged to form a full-wave rectifier. A first terminal of a coil is connected to the positive side of the full-wave rectifier, and a second terminal of the coil is connected to an anode of a fifth diode. The anode of a sixth diode is connected to a cathode of the fifth diode via two series-coupled capacitors, and a cathode of the sixth diode is connected to a further coil. A first terminal of a switching means is connected between the anode of the fifth diode and the second of the coil. A second terminal of the switching means is connected to a coil which is connected to the negative side of the full-wave rectifier. A switch is connected between the connecting line of the diodes in one of the diode-pairs in the full-wave rectifier and the line connecting the capacitors.

A 2.5 V temperature compensated CMOS logarithmic amplifier

Abstract: A new temperature compensated low voltage current-mode CMOS logarithmic amplifier is presented. The logarithmic amplifier uses seven cascaded limiting current amplifiers for piece-wise approximation of the logarithmic function and a current peak detector for detecting signal amplitude with a dynamic range of 60 dB. The circuit uses a current reference to stabilize the temperature dependencies down to /spl plusmn/1 dB. The designed amplifier is fabricated with a 1.2 /spl mu/m CMOS process. It operates with down to a 2.2 V single supply voltage and the power consumption is 3 mW with a 2.5 V supply.

Automatic gain control circuit and method

Abstract: An automatic gain control 20 is adapted to compensate to equalise the gain for signals of different characteristics (e.g. the preamble region and the main data region of a signal retrieved from a tape). The signals are amplified by a VGA 32 , the output of which is monitored by a peak detector 44 , whose output is compared at amplifier 48 with a respective target value for the particular signal region from a associated counter or register 60, 62, 65 , to control the gain control signal applied to the VGA 32 by a gain control 50 . The output of the comparator amplifier 48 is monitored before and after the transition between the first and second signal regions and the reference values in the appropriate register 60, 62 incremented or decremented in accordance with any step in the output of the amplifier 48 , substantially to equalise the gain before and after the transition.

A new harmonic reducing three-phase diode rectifier for high voltage and high power applications

Abstract: A new harmonic reducing diode rectifier for high voltage and high power applications is proposed. The new rectifier consists of the conventional double sequential (or series connected) three-phase bridge 12-pulse diode rectifier and a particularly designed auxiliary circuit. The double sequential topology is suitable for high voltage and high power applications because the output voltages of the two bridges are added and fed to the load. Harmonics of the utility line currents and ripples of the DC voltage of the proposed rectifier are reduced as low as those of the 24-pulse rectifier due to the operation of the auxiliary circuit. Since the new rectifier does not require any self turn-off device nor controller and the ratings of the components in the auxiliary circuit are also low, the proposed scheme gives an economical, efficient and reliable solution to obtain high voltage and high power DC from the utility without harmonic pollution. In this paper, operation of the new rectifier is introduced, and current and voltage synthesis is then discussed in detail. Experimental results are also shown to confirm the validity of the theory.

Designing passive LC filters with contour maps [for diode bridge rectifiers]

Abstract: The operating characteristics of a diode bridge rectifier incorporating a passive LC filter are analyzed by numerical calculations A computer program is developed to create the contour maps of the power factor, total harmonic distortion and the DC output voltage With the help of the contour maps, the circuit parameters of LC filters can be determined according to practical considerations as well as the desired performance of the rectifier circuit

Robust, harmonic-injection system for single-switch, three-phase, discontinuous-conduction-mode boost rectifiers

Abstract: In a single-switch, three-phase DCM boost rectifier, a voltage signal proportional to the inverted ac component of the rectified, three-phase, line-to-line input voltages is injected as a modulating signal into the control circuit to vary the duty cycle of the rectifier within one line cycle. As a result of its generation method, the injected signal is naturally synchronized with the three-phase, line-to-neutral input voltage. In addition, the injection method of this invention does not affect the closed-loop feedback control of the DCM boost rectifier since the injected signal is generated in an open-loop fashion. Three alternative methods to generate the injection signal are described. One method uses three low-frequency, step down transformers in generating the injection signal. The other two methods use operational amplifiers instead of the transformers.

Bridge rectifier configuration and mounting for supplying exciter current in an ac generator

Abstract: A rectifier module assembly for a conventional three phase AC generator is formed into two crescent shaped rectifier modules (12 and 14) so that the rectifier assembly can be mounted directly to the housing (45) of the exciter rotor. The positive and negative rectifier modules (12 and 14) are thermally conductive so that the exciter rotor itself can act as a heat sink for the rectifier module assembly. The rectifier module assembly occupies the space between and around the generator shaft (42) and the exciter rotor windings.

Apparatus and method for combining measurement of electrical properties and depth of a fluid

Abstract: An assembly of probes ( 1000 ) measures both the electrical properties and the depth of a fluid ( 1045 ). A first probe section ( 1040 ) is electrically energized, while a second probe section ( 1030 ) is de-energized. In a first measurement, the electrical properties of the fluid are measured. Low- and high-frequency, alternating potentials are used in measuring the conductivity and dielectric constant of the fluid. These potentials cause a current to flow in the fluid and also in a proximate conductor ( 1010 ), which is connected to the input of an operational amplifier ( 1080 ). The operational amplifier converts the current to a voltage whose amplitude and phase are measured using a precision rectifier ( 1092 ), a voltmeter ( 1096 ) and an oscilloscope ( 1094 ) (or alternatively with an analog-to-digital converter ( 1100 ), and a microprocessor ( 1150 )). A similar measurement is made with a second probe section ( 1030 ) also energized. The electrical properties of the fluid ( 1045 ) previously determined are then used in combination with a second current measurement and knowledge of the geometry of the second probe ( 1030 ) to determine the depth of immersion of both probes in the fluid.