Showing papers on "Precision rectifier published in 1994"

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

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

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

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

High frequency current conveyor precision full-wave rectifier

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

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

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

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

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

Control of front-end three-phase boost rectifier

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

Fast-response high-quality rectifier with sliding mode control

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

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

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

Temperature independent current conveyor precision rectifier

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

Efficient switched mode power converter circuit and method

Abstract: A method and apparatus are disclosed for sustaining efficiency of switched mode power converters over wide load ranges. The method and apparatus can be used with any switched mode power converter having at least one synchronous rectifier (Q2) capable of being enabled or disabled and coupled, either by direct connection or otherwise, to an inductor (L1) and a diode rectifier (D1), to provide a current path for the inductor current when the synchronous rectifier (Q2) is disabled. The power converter is initialized by enabling the synchronous rectifier (Q2). Occasionally, the synchronous rectifier (Q2) is disabled, and the energy stored in the inductor (L1) is detected by sensing a voltage representative of the energy stored in the inductor (L1). A power level signal is then generated indicating whether the power converter is operating above a selected threshold. The power converter is configured in response to the power level signal by enabling the synchronous rectifier (Q2) if the power level is above the threshold or by disabling the synchronous rectifier (Q2) otherwise. The steps of disabling, detecting, generating, and configuring are repeated.

Automatic offset control circuit for digital receiver

Abstract: An automatic offset control circuit comprises a differential output preamplifier (102) having an offset adjustment function, further comprising an average detector (106), a peak detector (107), and a differential input amplifier (108). The average detector (106) generates a reference voltage representing an average value of a positive output (V+) and a negative output (V-) of the preamplifier (102). The peak detector (107) outputs a peak voltage representing a peak of the negative output (V-) of the preamplifier (102). The differential input amplifier (108) compares the peak voltage with the reference voltage to output an offset adjustment signal to the preamplifier (102). The offset adjustment signal is obtained based on a difference between the reference voltage and the peak voltage. A bottom detector (109) may be used instead of the peak detector (107), provided a bottom value is detected using the positive output of the preamplifier.

Cost effective high performance circuit for driving a gas discharge lamp load

Abstract: A circuit for driving a gas discharge lamp load and including an EMI and transient supply filter coupled to an input source, a rectifier coupled to the filter, a power inverter coupled to the rectifier, a load including a transformer coupled to the power inverter, and a control circuit coupled to the power inverter and the load. A feedback circuit couples the load transformer to the AC side of the rectifier to create a path for transferring a feedback voltage over the rectifier to cause the rectifier to conduct current over a substantive portion of each cycle of the AC input voltage.

A new method to improve THD and reduce harmonics generated by a three phase diode rectifier type utility interface

Abstract: In this paper, a new method to significantly improve the performance of a three phase diode rectifier type electric utility interface is proposed. The proposed method guarantees near sinusoidal input currents at unity power factor for varying load conditions. The method is effective in continuous as well as discontinuous operating modes of the diode rectifier. The scheme employs a zig-zag transformer along with a two switch PWM current controlled power converter to circulate a variable amplitude third harmonic current. The interconnecting zig-zag transformer virtually short circuits the zero sequence third harmonic current and also draws negligible 60 Hz currents from the input AC mains since there is no real power exchange. This method does not significantly alter the existing rectifier inverter hardware and the DC link voltage magnitude is unaltered. It is shown that the proposed approach is effective in discontinuous mode of the diode rectifier and in situations where the DC link inductor is absent such as in the front-end rectifier of an AC drive. Wide operating range and superior harmonic reduction ability are the main features of this scheme. Analysis, design, implementation, comparison and application aspects of this new active harmonic reduction scheme are discussed. Simulation and experimental results illustrate the effectiveness of the proposed method. >

Unity-power-factor PWM rectifier with DC ripple compensation

Abstract: This paper presents a new topology of PWM rectifier which can achieve unity-power-factor on the AC supply side and ripple-reduction on the DC output side. The main circuit of this rectifier is accomplished by adding only a pair of switches to a conventional PWM rectifier. And it does not need the large DC capacitor or passive L-C resonant circuit. These additional switches and PWM rectifier are controlled not only to make a unity power factor but also to reduce the ripple current. The effectiveness of this circuit is confirmed by the experiments and analysis. This rectifier is useful for UPS and DC power supply, especially in case that the batteries are connected to the DC line. >

Method and apparatus for enabling a step-up or step-down operation using a synchronous rectifier circuit

Abstract: A DC--DC converter capable of both step-up and step-down operations includes a synchronous rectifier coupled between a rectifier connection and an output node, an inductor coupled between an input node and the rectifier connection, a rectifier control circuit for controlling the synchronous rectifier, the rectifier control circuit coupled to the input node, to the synchronous rectifier, to the rectifier connection and to the output node, and a switch coupled between the rectifier connection and ground. After closing the switch to build up energy in the inductor, the synchronous rectifier turns on simultaneously with the opening of the switch when the voltage of the rectifier connection is greater than the voltage of the output node and the voltage of the input node. The synchronous rectifier turns off when a current through the inductor becomes zero or when the switch closes again. Also, the synchronous rectifier is off when the circuit is in a shut-down mode to conserve power or when the voltage of the rectifier connection does not exceed the voltage of the input or output node. A Miller capacitor is provided to maintain frequency stability.

Peak detection circuit for suppressing magnetoresistive thermal asperity transients in a data channel

Abstract: A peak detector for extracting pulses in a magnetoresistive sensor circuit while suppressing the recovery transients created by thermal asperities. The disclosed peak detector circuit is a simplified variation of the standard magnetoresistive sensor peak detector circuit. The signal differentiation is performed ahead of the usual amplification to remove transient pulse amplitudes before they can affect the AGC gain. The resulting differentiated signal is processed by a modified amplitude qualification circuit to extract data output pulses. The thermal asperity transient recovery period is eliminated without additional circuit complexity, leaving only the initial thermal asperity pulse effects to be corrected by any suitable relatively simple error correction code (ECC).

Device for supplying a voltage to an electronic circuit, in particular an electronic circuit associated with a current sensor disposed on an electrical line

Abstract: A device for supplying a power supply voltage to an electronic circuit, in particular to an electronic circuit associated with a current sensor for measuring the electrical current in a high-tension line, comprises a current transformer having a primary circuit and a secondary circuit, a rectifier bridge shunting the secondary circuit and output terminals of the rectifier bridge, a first capacitor in parallel with a first resistor across which said power supply voltage is obtained, and a first switch disposed between the output terminals of the rectifier bridge. It includes between the output terminals of the rectifier bridge a branch comprising in series a second capacitor, a second switch and a second resistor. The first switch is controlled by a first threshold detector shunting the second capacitor. The second switch is controlled by a second threshold detector shunting the first capacitor. The first and second threshold detectors respectively close the first and second switches when predetermined first and second thresholds are respectively reached.

Micro power R-C relaxation oscillator

Abstract: An R-C relaxation oscillator having two comparators and a silicon controlled rectifier dissipates very low average power without resulting in frequency instabilities due to circuit propagation delays. A timing capacitor CT is charged through a timing resistor RT. The first comparator compares the voltage across the timing capacitor with an upper threshold voltage VTH. When the voltage across the timing capacitor crosses the upper threshold voltage, the comparator turns on the silicon controlled rectifier, which causes the capacitor to discharge the voltage that it has stored. The second comparator turns off the silicon controlled rectifier when the voltage across the timing capacitor falls below a lower threshold voltage VTL. The silicon controlled rectifier also provides boosted comparator bias current during the discharge phase, enabling the second comparator to respond quickly to the lower threshold voltage crossing and allowing fast capacitor discharge (therefore narrow clock pulses) and increasing frequency stability.

Power factor correcting circuit

Abstract: An electronic circuit arrangement for operating a discharge lamp, having a full-wave rectifier, a storage capacitor charged to a voltage greater than the peak of the rectifier output, and an isolating diode between the rectifier and the diode. An inverter is connected to the energy storage capacitor, and has a high frequency inductive load circuit connected between the inverter output and a junction between the isolating diode and the storage capacitor. A capacitor, connected to the junction in parallel with a series circuit formed by the isolating diode and storage capacitor, forms a high frequency resonance circuit with the inductive load circuit. Current is drawn from the rectifier only as a series of pulses at the inverter frequency.

A quick response peak detector for variable frequency three-phase sinusoidal signals

Abstract: An instantaneous peak detector for three-phase variable frequency sinusoidal signals is proposed. The three-phase characteristic is fully used in the proposed detector to achieve instantaneous response and frequency independence characteristics. A very simple hardware implementation circuit is also presented for minimizing the number of analog computational components. Moreover, the proposed detector possesses excellent linearity and low sensitivity to small voltage unbalance and harmonic distortion. Because of its promising accuracy and transient response, it can be used in many systems such as the voltage regulator of an uninterruptible power supply (UPS), an automatic line voltage regulator, or electric generators, etc., to improve the system transient performance. Theoretical analysis, hardware implementation, and some experimental results are also detailed in this paper. >

Unity power factor three-phase dither rectifier using a single switching device

Abstract: Electronic equipment is now widely spread in all industrial, commercial and domestic fields, which has resulted in an increasing presence of rectifier loads in the power system. The usually used capacitor input rectifiers, however, inject a large amount of low-order harmonic currents to the power system, which causes the distortion of the system's voltage waveform The authors have proposed a family of converters with over 99% power factor using a unique switching device and simple control schemes, named a dither converter. However, previously presented circuits are effective only for small single-phase power sources, which limit their application to home electronics and office use equipment. In this paper, a new three-phase rectifier circuit with sinusoidal input current is proposed. This circuit is composed of three fly-back transformers, a diode bridge and a single switching device, which results in a very simple circuitry and control method. Computer simulation confirmed the validity of the circuit, showing sinusoidal and balanced input currents and a ripple-less output voltage. A 3 kW experimental circuit was also made to confirm the numerical results. The circuit obtained 99.0% power factor, 85% efficiency and small output ripple voltage. >

Advanced three-phase ZVS-PWM active power rectifier with new resonant DC link and its digital control scheme

Abstract: In this paper, a novel prototype of a zero voltage soft-switching PWM three-phase AC/DC active power converter with a new transformer-assisted quasi-resonant tank DC link (TQRDCL) is presented for power factor correction, sinewave line current shaping and constant output DC voltage regulation. The instantaneous space voltage modulated sinewave line current synthesizing scheme of this high-power factor active rectifier with an instantaneous output DC power feedback loop is implemented by digital signal processor-based software and its related hardware. The simulation results of this soft-switched active rectifier are illustrated and discussed as compared with the other resonant DC link rectifiers and hard-switched active rectifier.

Class D converter with half-wave regulated synchronous rectifier

Abstract: A Class D series resonant converter with a controllable PWM synchronous half-wave current-driven transformer rectifier is presented, including its analysis and experimental results. Replacing the diodes in a conventional current-driven half-wave rectifier with MOSFETs allows voltage regulation for line or load swings of greater than 70% at a minimum of 50% efficiency and a maximum above 80% for a 3.3 V supply producing 15 W of power. The operating frequency was held constant at 120 kHz. The rectifier is driven by a Class D ZVS series resonant inverter and a transformer, which provides a sinusoidal current source. >

Feedback control circuit for a synchronous rectifier having zero quiescent current

Abstract: The present invention is for an active rectifier for use in a DC to DC converter wherein a feedback control circuit activates and de-activates the current conduction between the input and the output. Preferably, the current conductor between the input and the output is a P-type MOSFET, wherein the feedback control circuitry provides the activation or de-activation signal to the gate of this transistor. The feedback control circuitry provides an activation signal to the transistor when the input voltage is greater than the output voltage, and provides a de-activation signal to the transistor when the input voltage is equal to or less than the output voltage. Because the P-MOS rectifier has a lower voltage drop than the Schottky diode, the forward drop is reduced. In addition, the feedback control circuit is designed to draw no current except when the P-MOS rectifier is conducting.

Method and equipment for reducing peak mean electric power inside multicarrier wave rf communication system

Abstract: PURPOSE: To improve the throughput of linear amplifier by inputting average power and peak power detected from the input of amplifier to a controller, outputting a control signal from its ratio, and changing the phase of multiplex signal channel. CONSTITUTION: Plural phase-locked radio transceivers 101-104 receive audio and data signals as information signals, perform frequency modulation, transmit these signals via leads 111-114 to a coupler circuit 106 at different carrier wave frequencies, and couple them into compound modulated signal. That compound signal is inputted through a preamplifier 107 to the linear amplifier and transmitted through an antenna 110. On the other hand, power inputted to an amplifier 109 is detected by a coupled device 151, its output is passed through an average power detector 152 and a peak detector 153 and the average power and peak power is inputted to a controller 161. The controller 161 inputs a control signal from the ratio of input signals to phase shifters 131-134. An output signal from a reference frequency generator 121 is inputted via a splitter 122 to the shifters 131-132, and the phase of multiplex signal is controlled.

Rectifier characteristics based on bipolar-mode SIT operation

Abstract: A novel rectifier concept based on bipolar-mode static induction transistor (BSIT) operation is proposed. A numerical simulation has revealed that the turn-on mechanism of this rectifier, owing to a combination of static induction effects and minority carrier injection, can make its forward-voltage drop and reverse recovery time smaller than those of the conventional p-i-n rectifier. As an example of the design methods, the simulation has clarified the effects of decreasing the doping concentration in the channel between p/sup +/ regions on improvement in the tradeoff between a forward voltage drop and leakage current. >

Glow-lamp and SMPS brightness control

Abstract: A procedure for controlling the brightness of lamps uses a semiconducting rectifier bridge circuit in series with the lamp. The rectifier is switched on at the zero-crossing point of the incoming voltage wave and remains conducting until the output voltage of an integrator exceeds a chosen threshold. The input voltage to the integrator comes from a squaring circuit which in turn is fed with a voltage proportional to the current flowing through the rectifier. The integrator is reset at every zero crossing. Instead of the rectifier circuit, two semiconducting switches (like FET's) can be connected in series opposition, with the voltage to the squarer still proportional to the current through them.

Electronic control of peak detector response time

Abstract: A peak detector circuit operates to charge a capacitor to a level proportional to the peak input signal level. The charging circuit includes an emitter follower driver. The response time of the charging circuit is enhanced by coupling a constant current to the emitter follower output. The constant current acts to lower the emitter follower source impedance which operates to increase the rate of capacitor charging.

A new three-phase unity power factor boost rectifier with capacitive-type input

Abstract: In this paper, a new low cost three-phase AC-DC high power/low harmonic controlled rectifier is presented. 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. Thus, the input diode rectifier operates in zero-voltage and zero-current switching conditions, avoiding reverse recovery problems. This paper describes the proposed circuit and its analysis, design and performance. This circuit is compared with two other schemes used for current harmonic reduction to satisfy the IEEE 519 standard in three-phase utility interface. The limitations of the proposed converter are discussed. >