Showing papers on "Precision rectifier published in 1992"

Harmonic current reduction in a three-phase diode bridge rectifier

Abstract: A novel method for reducing harmonic currents on the AC supply side of a three-phase bridge rectifier is presented. The principle of the method is to modify the current waveforms in the DC windings of the converter transformer by injecting a third harmonic current into the neutral point of the transformer. Passive LC filters connected between the rectifier output and the secondary neutral point act as third harmonic current sources. The effectiveness of the method is confirmed by laboratory recordings. >

A multilevel-voltage source rectifier with a three-phase diode bridge circuit as a main power circuit

Abstract: A novel system obtaining very low distorted waveforms of input AC currents of three-phase rectifier circuits are proposed. The proposed rectifier system consists of a three-phase diode bridge circuit as a main power circuit, AC reactors, and an additional circuit which serves as an active filter with low switching frequencies and a forced-commutation circuit for the diodes. This paper describes the operation principle, analysis of the waveforms of input voltage and current, multiple phase-shifted systems, and the experimental results. The proposed system gives excellent input current waveforms and has many advantages over conventional systems. >

Digital pulse processor using moving average technique

Abstract: A digital pulse processor with improved differential linearity and reduced dead time has been designed. The circuit uses an 8-b flash ADC (analog-to-digital converter) running at 36 MHz and continually sampling the signal from the preamplifier or shaping amplifier. The digitized signal is then processed by a digital moving averager. A digital peak detector is used for measuring the amplitude of the shaped pulses. A novel, threshold-free circuit has been designed that combines both the moving average and peak detection functions. The circuit also provides a timing signal with an uncertainty of one sampling period. The number of the averaged samples (equivalent to the shaping time constant) is digitally controlled. The resolution of the processor is limited by the finite ADC resolution and the finite sampling frequency. Increasing the sampling frequency should improve the resolution in pulse height analysis and the timing precision. >

Class E resonant low dv/dt rectifier

Abstract: A class-E resonant low dv/dt rectifier is analyzed and experimentally tested. All major parasitic reactive components are included in the rectifier topology. The diode capacitance and the leakage inductance of the isolation transformer and lead inductances are absorbed into the resonant inductance. Therefore, the rectifier is suitable for high-frequency applications such as resonant DC-to-DC converters. The rectifier is driven by a sinusoidal voltage source. Equations governing the circuit operation are derived using Fourier techniques. Experimental results are obtained at 1 MHz and an output voltage of 5 V. The design equations show good agreement with the measured circuit performance. >

Automatic volume leveler

Abstract: A circuit for controlling a reproduced volume level of an audio signal to a desired level includes a peak detector for detecting a peak amplitude level in the audio signal, a user operable control for generating a signal indicative of a desired amplitude level, a comparator for comparing the detected peak amplitude level in the audio signal with the desired amplitude level and for generating a comparison signal as a result of the comparison, and a voltage controlled amplifier coupled to the comparator for adjusting the peak amplitude level in the audio signal in dependence on the comparison signal. The output from the voltage controlled amplifier then has the desired level.

Integrable CMOS sinusoidal frequency doubler and full-wave rectifier

Abstract: A CMOS integrable circuit technique for the realization of both a sinusoidal frequency doubler and a full-wave rectifier is described in this paper. The realization method makes use of the characteristic of a simple CMOS class AB amplifier configuration. Simulation and experimental results demonstrating the circuit performance are also included.

Level independent automatic cable equalizer

Abstract: A multiple section cable equalizer with a signal level detector (700-800) produces a clipping control signal (4) for amplifiers in each equalizer section (200,220,240), so that a variable level input signal (5,6) is restored to an equalized output signal (87,88) that is free of distortion and attendant bit errors. A fixed reference clipping stage (300) after the last equalizing stage (240) produces a signal clipped to a final output level. A feedback path (500,600) restores DC and low frequencies lost due to AC coupling. A test output stage (400) permits monitoring (110,111) of the operation of the equalizer stages (200,220,240). The signal level detector contains (in series), a differential amplifier (700) with low pass filtering (R22,C1,R18), a balanced modulator detector (710), a voltage amplifier (720), a comparator and peak detector (730,CX4), a transconductance amplifier (740) and a plurality of current mirrots (750,760,770,800) operatively connected to determine a difference current (59) from the output (48,49) of the transconductance amplifier (740) and convert this to a clipping control signal (4) voltage level. A defeat comparator (790) monitors the output (37) of the comparator and peak detector (790) and replaces the variable difference current (59) with a fixed reference current (800) when an external capacitor (CX4) used by the peak detector (730) appears to be shorted.

Rectifier circuit including FETs of the same conductivity type

Abstract: A rectifier circuit is constructed entirely with field-effect transistors of the same conductivity type and which provides rectification with a small voltage drop and hence a high efficiency. A normally-off FET is coupled between an alternating voltage input and a direct voltage output. A bias circuit biases the gate of this FET so as to reduce the effective threshold voltage of the FET substantially to zero. Bridge rectifier circuits, based on this principle make it possible to obtain both half-wave and full-wave rectification with a very small voltage drop. Various circuits for generating the gate bias are disclosed.

Mains-isolated three=phase asynchronous rotary electrical machine speed monitor e.g. for door - has two=channel processing circuits for delivering bit signals to coupling circuit, which generates output signal when speed is above or below limits, if bit signal changes from rest to active within time window

Abstract: The monitor detects machine speed above or below a given limit value and uses a dual-channel evaluation circuit (11) coupled to the three machine winding phases (5,6,7). Each channel (12,13) of the evaluated circuit has two inputs (15,16;21,22) coupled to two different phases and a single digital output (17,23) providing a binary signal. The two binary signals are combined to provide an output signal which changes from a rest value to an active value when the limit value is exceeded. Pref. each channel of the evaluation circuit contains a voltage amplifier with a variable amplification and a precision rectifier. USE/ADVANTAGE - For asynchronous motor drive indicating abnormal speed to prevent overloading, without noise problems and without structural interference in or at machine.

Synchronous rectifier package for high-efficiency operation

Abstract: In a synchronous rectifier package, a Schottky diode is situated in parallel, i.e., with like polarity, with the body diode of a synchronous rectifier. The anode of the Schottky diode is connected directly to the source pad of the synchronous rectifier, and the cathode is directly connected to the drain pad. As a result, the synchronous rectifier package has minimal parasitic inductances and resistances, resulting in a highly efficient synchronous rectifier over a wide range of operating frequencies, even at high frequencies. More precise synchronization of gating signals to each individual cell of the synchronous rectifier is also achieved, further increasing rectification efficiency. The synchronous rectifier package is implemented in either a metallized ceramic structure, or a high-density interconnect structure.

Capacitor input type rectifier having a circuit for preventing inrush current

Abstract: A capacitor input type rectifier having a circuit for preventing an inrush current uses an AC phase detector for detecting the time that an AC voltage input has the smallest phase angle and provides an output signal indicative thereof to a phase control rectifier for initiating rectification of the AC voltage to provide a rectified output to a smoothing circuit for smoothing the rectified output of the phase control rectifier.

Indicating means in a double voltage motor vehicle electrical circuit

Abstract: A double voltage alternator circuit having two alternators, each associated with one of two batteries connected in series, and two alternator excitation current control circuits each of which receives a d.c. voltage from an auxiliary rectifier bridge associated with the corresponding alternator, also has a single warning lamp connected between that terminal of a first one of the batteries which is not directly connected in series to the other battery and (a) the auxiliary rectifier bridge associated with that other battery, through an avalanche diode which enables current to pass through the lamp when the voltage at its terminals is greater than a predetermined value, and (b) to the auxiliary rectifier bridge associated with the first battery, through a uni-directional circuit element such as a diode which prevents current from flowing between the two auxiliary rectifier bridges. The invention enables fault indication in a double voltage circuit to be given using a single lamp.

Analysis of a Class E rectifier with a series capacitor

Abstract: The analysis, design procedure, and experimental results are presented for a Class E rectifier. The circuit consists of a diode, a series capacitor, and a second-order lowpass filter. The diode ON duty cycle and the ripple voltage are decoupled, i.e. the two parameters are determined by different circuit elements. The diode turns on at low mod dv/dt mod and turns off at zero dv/dt and low mod di/dt mod , reducing both switching losses and noise. The circuit has a step-down AC-DC voltage transfer function and therefore is especially suitable for applications in low-output-voltage power supplies. The experimental and calculated results were in good agreement.

Ripple Compensation for a Single-Phase Rectifier by 2-Quadrant Chopper and Auxiliary Capacitor

Abstract: The single-phase converter or rectifier always has a voltage ripple in the output DC voltage, because the instantaneous power of the single-phase AC line varies on the double frequency of the line. In order to obtain a smooth DC voltage, an energy storing element is necessary. The smoothing capacitor is used to reduce the ripple voltage in the DC output. Usually, it has much larger capacitance than that needed to absorb the ripple energy. This paper discusses the required capacitance to absorb the ripple energy, and represents a ripple compensation circuit with a small auxiliary capacitor controlled by a 2-quadrant chopper connected in parallel to the smoothing capacitor. The appended capacitor works under large ripple voltage and efficiently absorbs the ripple energy. The ripple compensation curcuit works as an equivalent capacitor which has a large capacitance.

Synchronous rectifier using bipolar transistor driven by current transformer

Abstract: In the power supplies to obtain a low output voltage and a high current, it is difficult to obtain high efficiency due to the forward voltage of the diode for output rectification. A method has been reported for improving the efficiency of the power supply by using bipolar transistors (BJT) with a low saturation voltage as a rectifier so that the forward voltage is reduced. However, in general, a driving circuit for the BJT is required and the application of the latter to a power supply is not straightforward. This paper proposes a synchronous rectifier system which drives a BJT by a positive feedback by a current transformer. The operating principle of this circuit is described. The reset condition of the magnetization energy of the current transformer is clarified. The present method has a simple circuit configuration in which a part of the emitter current of the BJT is used as a base-driving current by means of a current transformer. No special BJT driver circuit is needed. The present synchronous rectifier was installed in an actual power supply. It was confirmed that the efficiency is improved over the circuit using Schottky diodes.

Self-regulated current rectifier with quasi=resonant d.c. voltage intermediate circuit - contains resonant circuit choke between constant voltage source and power switches forming triggering resonant circuit with capacitor

Abstract: The current rectifier contains a resonant circuit choke in the line from a constant voltage source to rectifier power semiconductor switches. The choke forms a resonant circuit with a capacitor between the switch ports on the d.c. side to switch the switches when the intermediate circuit voltage approaches null. The choke is bridged by a series circuit contg. a clamp capacitor and a clamp power switch and antiparallel clamp diode. The resonant circuit capacitor (Cr) is connected in series with a resonant circuit switch (Ts) bridged by a diode (Ds) conducting in the direction of the constant dc voltage (Ud). USE/ADVANTAGE - Cost of power switches is reduced, high losses in the semiconducting clamp switches avoided and full utilisation of the constant dc voltage ensured.

CMOS full-wave operational transconductance rectifier with improved DC transfer characteristic

Abstract: The proposed full-wave rectifier is based on a source-coupled pair associated with a new current-mode circuit that computes the absolute value of the difference of two currents. The DC transfer characteristic is well controlled through technology parameters because device mismatches and channel length modulation give rise to distinct imperfections. In addition, it reaches zero output current at the origin in every case. These properties make the circuit suitable for dense implementation of Manhattan distance computation in analogue VLSI neural networks.

Selectable dual rectifier power supply for musical amplifier

Abstract: A power supply for use with a musical amplifier includes two user-selectable rectifiers for variously enhancing sound generated by a musical instrument such as a guitar, or by recorded musical material which in either case consists of electrical signals applied to a vacuum tube amplifying apparatus. The first of two rectifiers comprises one or more thermionic vacuum tube devices, depending upon power needs, while the second rectifier is comprised of solid-state silicon diodes. A switch circuit enables the user to select which of the two rectifier devices is better suited to the contemporaneous use of the amplifier.

Ripple feedback for the resonant-filter unity-power-factor rectifier

Abstract: An unusual bucklike unity-power-factor rectifier with a resonant load-balancing network permits current-limited operation down to zero output voltage in a single-stage topology. However, this rectifier has been found to be sensitive to AC-line voltage distortion and is potentially unstable with realistic values of AC-line impedances. A new ripple feedback is proposed that solves both problems. A large-signal time-varying analysis is given along with incremental, quasi-static, and low-frequency approximations. Experimental verification is provided by a 500 W 500 kHz rectifier operating from the 120 V, 60 Hz distribution system. >

Video display terminal magnetic field detector

Abstract: A system for detecting the presence of a magnetic field emanating from a video display terminal (VDT) in which a current induced through a sensing element is first amplified by a high gain amplifier stage having a very broad low band frequency response curve then rectified by a precision rectifier to convert the AC signal induced through the sensing element to DC current The DC current is used as one input to a comparator, the other input being set by means of a potentiometer to provide flexibility in setting a threshold input voltage differential representative of a harmful magnetic field radiation level The output of the threshold comparator triggers a driver which is connected to a battery powered solenoid The solenoid actuates an indicator flag in the presence of a magnetic field which exceeds the threshold magnetic radiation level To conserve battery energy, the energized solenoid also functions as a relay to break electrical contact between itself and the batteries simultaneously with actuating the flag indicator An alternative embodiment of the invention replaces the pickup coil of the preferred embodiment with a Hall effect current sensor to sense the strength of the magnetic field

Two-stage ballast circuit for LV discharge lamp - has rectifier with control circuit where shunting main resistor with others gives dimming and electrode pre-heating functions

Abstract: A digital two stage ballast circuit for low voltage discharge lamps has a rectifier supplying the lamp via a parallel capacitor and series inductor. There is an electronic harmonic filter comprising a high setting inductance and a digital control circuit for the rectifier. For normal illumination, one resistor is used as input to the control circuit, but by shunting it with another by means of a switch, an extra current passes to the control circuit, giving a higher control frequency and thereby, a dimming of the lamp. Adding in an extra parallel resistor before the lamp is ignited gives electrode heating. ADVANTAGE- Energy-saving

Phase-sensitive rectifier arrangement with integration effect

Abstract: A circuit combining the functions of phase-sensitive rectifier and integrator uses an operational amplifier and capacitors. A control signal switches a capacitor in and out of a feedback loop containing a second feedback capacitor, resulting in a residual charge in the second feedback capacitor if there is a phase-difference between an input signal and the control signal. The invention may also incorporate an automatic offset compensation circuit by using additional switches and a second control signal. The capacitor that is switched in and out of the feedback loop is coupled to a compensation capacitor during periods when the capacitor is not being used for the phase-sensitive rectifier and integrator portions of the circuit. The circuit arrangement allows the use of long time constants in the integrator portion of the circuit.

Three=phase current generator with diode rectifier esp. for motor vehicle - has DC excitation winding and three=phase windings and rectifier contains three diode paths arranged as three=phase bridge rectifier

Abstract: The two diodes of each diode path (11, 16, 17) are arranged with polarity in the same direction, and lie in series respectively as a positive diode and a negative diode. Each diode path is connected between the two therein lying diodes with one of the three phase windings (15, 24, 25). The connections of the three positive diodes (26) in the three diode paths, are connected together to a positive pole (28). The corresp. connections of the negative diodes (27) are connected together to form a negative pole (8). The two diodes in a diode path are different types of diode. The same type of diode is used as a positive diode (20) or a negative diode (27). A silicon diode (12, 18, 19) is used as the first type of diode and as a second type of diode, a Schottky diode (13, 20, 21) is used. ADVANTAGE - Temp. loading of rectifier diodes reduced.

Rectification system for non-resonant voltage switched converters

Abstract: Applicable to non-resonant switched mode power supplies with voltage regulation by means of pulse width modulation. Its objective is to achieve a reduction in the amplification in the value of input capacitance (Miller effect) at the instants of switching of the MOSFET rectifier transistors, and to prevent the appearance of a shortcircuit in the main power supply unit at such instants. The first of these objectives is achieved by having the switching of the MOSFET rectifier transistors take place at a value of drain-source voltage equivalent to the cathode to anode voltage drop of a conducting diode (approximately zero volts). The second objective is achieved assuring that change of state from cutoff to conduction, or vice versa, of the MOSFET rectifier transistors never occurs simultaneously with the change of state of the other switches in the converter.

A simple continuous-time equalizer for use in magnetic storage read channels

Abstract: A four-pole continuous-time equalizer has been developed to minimize the error rate in rigid-disk magnetic storage channels employing peak detection at high recording densities. The design process consisted of two parts. A nominal model of the disk drive characteristics in the time and frequency domains was obtained from digitized waveforms at the output of a read-head amplifier in a disk drive system. The relative performance of candidate equalizers was studied by subjecting them to the measured data waveforms and then either estimating or measuring the resulting bit error rate in a simulated peak detector, operating on the equalized waveforms. The equalizer outperforms more complex structures proposed for this task and is well suited for implementation as an analog CMOS active filter with low power dissipation. Its constellation of four poles and a zero appears to be useful for several types of magnetic media. >

Apparatus for improving rise characteristics of direct current power supply

Abstract: If a rectifier having Walk-in characteristics is directly connected to a dc-dc converter, an output current of the rectifier violently fluctuates because of the Walk-in characteristics of the rectifier. The Walk-in characteristics have been improved by connecting an apparatus in parallel with the rectifier. The apparatus includes a storage battery and a switch. During the Walk-in period, the switch is closed and the storage battery supplements the capacity of the rectifier. After that, the switch is opened and the storage battery is charged by a current flowing through a diode and a resistor.

High-power GTO converter - uses thyristors connected in three=phase rectifier circuit

Abstract: The low-loss circuit arrangement is for e.g. GTO-thyristors (T1-T4) in a three-phase rectifier, in which each rectifier phase includes a series-arrangement of first-to-fourth anti-parallel circuits of one of the GTO-thyristors (T1-T4) and a free-wheeling diode (D1-D4). The GTO-thyristor (T,T4) of the first and fourth anti-parallel circuits is connected in parallel with a series-circuit of a switch-off discharge capacitor (C11,C41) and diode (D11,D4). The point of connection of the central anti-parallel connected circuits serves as phase output (A). The points of connection (B) and (C) are connected via a series-circuit of two additional capacitors (C31,C21) and a third ohmic resistor (R3), inserted between them. USE/ADVANTAGE - High power GTO converters. Reduced losses when switching the GTO switch.

Superconducting circuit having a rectifier for converting a bipolar signal to a unipolar signal

Abstract: A superconducting circuit system comprises a biasing circuit for producing a bias current that changes periodically, and a superconducting rectifier circuit driven by the bias current The superconducting rectifier circuit is supplied with a first pulse train including therein positive and negative pulses in synchronization with the bias current and produces a second pulse train of unipolar pulses in response to a transition of a Josephson junction caused by the pulses of the first pulse train