scispace - formally typeset
Search or ask a question

Showing papers on "Precision rectifier published in 2009"


Journal ArticleDOI
03 Nov 2009
TL;DR: Experimental results show the existence of an optimum transistor size in accordance with the output loading conditions and the peak PCE increases with a decrease in operation frequency and with an increase in output load resistance.
Abstract: A high-efficiency CMOS rectifier circuit for UHF RFIDs was developed. The rectifier has a cross-coupled bridge configuration and is driven by a differential RF input. A differential-drive active gate bias mechanism simultaneously enables both low ON-resistance and small reverse leakage of diode-connected MOS transistors, resulting in large power conversion efficiency (PCE), especially under small RF input power conditions. A test circuit of the proposed differential-drive rectifier was fabricated with 0.18 mu m CMOS technology, and the measured performance was compared with those of other types of rectifiers. Dependence of the PCE on the input RF signal frequency, output loading conditions and transistor sizing was also evaluated. At the single-stage configuration, 67.5% of PCE was achieved under conditions of 953 MHz, - 12.5 dBm RF input and 10 KOmega output load. This is twice as large as that of the state-of-the-art rectifier circuit. The peak PCE increases with a decrease in operation frequency and with an increase in output load resistance. In addition, experimental results show the existence of an optimum transistor size in accordance with the output loading conditions. The multi-stage configuration for larger output DC voltage is also presented.

432 citations


Journal ArticleDOI
TL;DR: An efficiency-enhanced integrated full-wave CMOS rectifier for the transcutaneous power transmission in high-current biomedical implants is presented and the comparator-controlled switches are developed to minimize the voltage drop along the conducting path while achieving the unidirectional current flow.
Abstract: This paper presents an efficiency-enhanced integrated full-wave CMOS rectifier for the transcutaneous power transmission in high-current biomedical implants. The comparator-controlled switches are developed to minimize the voltage drop along the conducting path while achieving the unidirectional current flow. The proposed unbalanced-biasing scheme also minimizes the reverse leakage current of the rectifier under different input amplitudes, thereby optimizing the rectifier power efficiency. Moreover, the proposed rectifier is able to self start and operates at low input amplitudes. Implemented in a standard 0.35 mum CMOS process with maximum threshold voltages of |Vthp| = 0.82 V and Vthn = 0.69 V, the rectifier can source a maximum output current of 20 mA and operate properly with inputs of different amplitudes and frequencies. With a 1.5 MHz input of 1.2 V amplitude, the proposed rectifier can achieve the peak voltage conversion ratio of 95% and the power efficiency of at least 82%.

239 citations


Journal ArticleDOI
TL;DR: A new bridgeless single-phase AC-DC converter with an automatic power factor correction (PFC) is proposed, based on the single-ended primary inductance converter (SEPIC) topology and it utilizes a bidirectional switch and two fast diodes.
Abstract: In this paper, a new bridgeless single-phase AC-DC converter with an automatic power factor correction (PFC) is proposed. The proposed rectifier is based on the single-ended primary inductance converter (SEPIC) topology and it utilizes a bidirectional switch and two fast diodes. The absence of an input diode bridge and the presence of only one diode in the flowing-current path during each switching cycle result in less conduction loss and improved thermal management compared to existing PFC rectifiers. Other advantages include simple control circuitry, reduced switch voltage stress, and low electromagnetic-interference noise. Performance comparison between the proposed and the conventional SEPIC PFC rectifier is performed. Simulation and experimental results are presented to demonstrate the feasibility of the proposed technique.

236 citations


Journal ArticleDOI
TL;DR: A closed form equation relating the RF power available from the antenna to the DC output voltage produced by a multi-stage rectifier enables the optimization of rectifier parameters for impedance matching with a low-cost printed antenna and shunt tuning inductor, in order to improve the RF to DC conversion efficiency and the operational distance of UHF RFID transponders.
Abstract: This paper presents a RF to DC conversion model for multi-stage rectifiers in UHF RFID transponders. An equation relating the RF power available from the antenna to the DC output voltage produced by a multi-stage rectifier is presented. The proposed model includes effects of the nonlinear forward voltage drop in diodes and impedance matching conditions of the antenna to rectifier interface. Fundamental frequency impedance approximation is used to analyze the resistance of rectifying diodes; parasitic resistive loss components are also included in the analysis of rectifier input resistance. The closed form equation shows insights into design parameter tradeoffs, such as power available from the antenna, antenna radiation resistance, the number of diodes, DC load current, parasitic resistive loss components, diode and capacitor sizes, and frequency of operation. Therefore, it enables the optimization of rectifier parameters for impedance matching with a low-cost printed antenna and shunt tuning inductor, in order to improve the RF to DC conversion efficiency and the operational distance of UHF RFID transponders. Three diode doublers and three multistage rectifiers were fabricated in a 130 nm CMOS process with custom no-mask added Schottky diodes. Measurements of the test IC are in good agreement with the proposed model.

185 citations


Journal ArticleDOI
TL;DR: In this article, a simple single-input-single-output model is constructed by separating the d -axis and the q-axis dynamics through appropriate nonlinear feedforward decoupling while maintaining nearly unity power factor operation.
Abstract: The challenge in controlling a three-phase pulsewidth modulation (PWM) rectifier under balanced conditions arises from the fact that the state-space averaged model reported in literature has a multi-input-multi-output nonlinear structure and furthermore exhibits a nonminimum phase feature In this paper, a simple single-input-single-output model is constructed by separating the d -axis and the q-axis dynamics through appropriate nonlinear feedforward decoupling while maintaining nearly unity power factor operation With the proposed model, the nonminimum phase feature inherent in an AC-to-DC rectifier becomes a simple right-half-plane zero appearing in the small-signal control-to-output transfer function In addition, the model exhibits a close similarity to a DC-DC boost converter under both large-signal and small-signal operating conditions This makes it possible to extend the system analysis and control design techniques of DC-DC converters to the three-phase PWM rectifier also The validity of the proposed model has been verified experimentally in the frequency domain under open-loop operation of the PWM rectifier The usefulness of the model is further demonstrated through closed-loop operation of the rectifier with both voltage mode and inner-current-loop-based schemes

85 citations


Journal ArticleDOI
TL;DR: The proposed method is very useful when the PWM boost-type rectifier is subject to extreme imbalance due to severe fault conditions in the power system and can be operated from the single-phase supply in cases where three-phase source is not available.
Abstract: Under severe fault conditions in the distribution system, not only input voltages but also input impedances must be considered as unbalanced. This paper presents a new control method for input-output harmonic elimination of the pulsewidth-modulation (PWM) boost-type rectifier under conditions of both unbalanced input voltages and unbalanced input impedances. The range of imbalance in both input voltages and input impedances, for which the proposed method is valid, is analyzed in detail. An analytical approach for complete harmonic elimination shows that PWM boost-type rectifier can operate at unity power factor under extremely unbalanced operating conditions resulting in a smooth (constant) power flow from AC to DC side. Based on the analyses in open-loop configuration, a feedforward control method is proposed. Elimination of harmonics at AC and DC side of the converter affects the cost of DC link capacitor and AC side filter. The proposed method is very useful when the PWM boost-type rectifier is subject to extreme imbalance due to severe fault conditions in the power system. In addition, by using the proposed method, the PWM boost-type rectifier can be operated from the single-phase supply in cases where three-phase source is not available. Simulation results show excellent response and stable operation of the PWM boost-type rectifier under the proposed control algorithm. Experimental and simulation results are in excellent agreement.

64 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the conception and analysis of a unidirectional hybrid three-phase rectifier suitable for medium and high power applications, which is composed of a single-switch diode bridge boost-type rectifier in parallel with a pulsewidth modulation (PWM) 3-phase UFD rectifier, and the rectifier topology, principle of operation, control scheme, and simulation results of a 20kW laboratory prototype are also presented.
Abstract: This paper describes the conception and analysis of a unidirectional hybrid three-phase rectifier suitable for medium- and high-power applications. The rectifier is composed of a single-switch diode bridge boost-type rectifier in parallel with a pulsewidth modulation (PWM) three-phase unidirectional boost rectifier. The objective is to obtain a structure capable of providing sinusoidal input currents with low harmonic distortion and dc output voltage regulation. The diode rectifier operates at low frequency and has a higher output power rating. Therefore, the PWM unidirectional rectifier is designed to operate with a small power rating and at a high switching frequency. The total harmonic distortion of the proposed structure varies between 0% and 32%, depending only on the amount of power processed by the PWM three-phase unidirectional rectifier. The rectifier topology conception, principle of operation, control scheme, and simulation and experimental results of a 20-kW laboratory prototype are also presented in this paper.

57 citations


Journal ArticleDOI
TL;DR: In this paper, a new full-wave rectifier topology is presented, which uses MOS transistors as low-loss switches to achieve a significant increase in overall power efficiency and reduced voltage drop.

56 citations


Journal ArticleDOI
TL;DR: An active current injection network for a three-phase rectifier using three bidirectional switches operating at low frequency and a half-bridge inverter operating at high frequency offers high efficiency and the total harmonic distortion is reduced.
Abstract: An active current injection network for a three-phase rectifier is proposed. The proposed circuit uses three bidirectional switches operating at low frequency and a half-bridge inverter operating at high frequency. It also uses an inductor in order to make the current modulation. Because only 3.7% of the total power delivered to the load is processed by the injection network, the proposed converter offers high efficiency, and not only a high power factor is obtained but also the total harmonic distortion is reduced. Operation, analysis, simulation, and experimental results are shown in this paper.

55 citations


Patent
19 Aug 2009
TL;DR: In this paper, a zero-volt switching during a light load is performed in such a manner that through an ON/OFF control of switches provided for a full bridge circuit and the synchronous rectifier switches in a rectifier and smoothing circuit, a resonant peak voltage necessary for the zero voltage switching determined by the output current flowing to output terminals is ensured.
Abstract: Zero volt switching during a light load is performed in such a manner that through an ON/OFF control of switches provided for a full bridge circuit and the synchronous rectifier switches in a rectifier and smoothing circuit, a resonant peak voltage necessary for the zero voltage switching determined by the output current flowing to output terminals, a resonant inductor and a resonant capacitor capacitance is ensured so that an energy accumulated in the rectifier and smoothing circuit is returned to the full bridge circuit so as to act as equivalent as when the output current is increased and to increase the current flowing through the full bridge circuit.

46 citations


Proceedings ArticleDOI
11 Dec 2009
TL;DR: In this article, two types of CMOS rectifier circuits for UHF RFID have been proposed: Self-Vth-Cancellation (SVC) and differential-drive (DD) rectifiers.
Abstract: Two types of CMOS rectifier circuits for UHF RFIDs have been proposed. Large power conversion efficiency (PCE) has been achieved by Vth cancellation techniques. In the Self-Vth-Cancellation (SVC) CMOS rectifier, the threshold voltage of MOSFETs is cancelled by gate bias voltage generated from the output voltage of the rectifier itself, resulting in excellent PCE. The differential-drive CMOS rectifier has a cross-coupled bridge configuration and is driven by a differential RF input. A differential-drive scheme realizes an active gate bias mechanism and simultaneously enables both low ON-resistance and small reverse leakage of diode-connected MOS transistors, resulting in large PCE, especially under small RF input power conditions. Test circuits for both types of rectifiers were fabricated and the measured performances were compared with those of conventional rectifiers.

Journal ArticleDOI
TL;DR: In this article, the transient performance and stability of a recurrent discrete Fourier transform (DFT) based control method for a series active filter integrated with a 12-pulse diode rectifier were investigated.
Abstract: This paper considers the transient performance and stability of a recurrent discrete Fourier transform (DFT) based control method for a series active filter integrated with a 12-pulse diode rectifier. The control method targets specific harmonics and/or the negative sequence fundamental component of the supply current, and is intended for use with nonsinusoidal/unbalanced supply voltages. The proposed control method is based on DFTs instead of the dq-method, and a simple approach is used to account for small frequency variations found in practical power systems.

Journal ArticleDOI
TL;DR: A high-efficiency CMOS rectifier circuit for UHF RFID applications was developed that achieves 32% of PCE at the -10dBm RF input power condition, which is larger than rectifiers reported to date under this condition.
Abstract: A high-efficiency CMOS rectifier circuit for UHF RFID applications was developed. The rectifier utilizes a self-Vth-cancellation (SVC) scheme in which the threshold voltage of MOSFETs is cancelled by applying gate bias voltage generated from the output voltage of the rectifier itself. A very simple circuit configuration and zero power dissipation characteristics in biasing enable excellent power conversion efficiency (PCE), especially under small RF input power conditions. At higher RF input power conditions, the PCE of the rectifier automatically decreases. This is the built-in self-power-regulation function. The proposed SVC CMOS rectifier was fabricated with a 0.35-µm CMOS process and the measured performance was compared with those of conventional nMOS, pMOS, and CMOS rectifiers and other types of Vth cancellation rectifiers as well. The SVC CMOS rectifier achieves 32% of PCE at the -10dBm RF input power condition. This PCE is larger than rectifiers reported to date under this condition.

Patent
12 Jan 2009
TL;DR: In this article, a current source rectifier is provided at an output of an alternating current generator, and two arms having switching elements connected in inverse parallel to diodes are connected to the output of the rectifier, and one terminal of a direct current power source capable of a power supply and absorption is connected to a midpoint between the arms.
Abstract: A current source rectifier is provided at an output of an alternating current generator, an alternating current motor is connected to an output of the rectifier via a voltage source inverter, furthermore, two arms having switching elements connected in inverse parallel to diodes are connected to the output of the rectifier, and one terminal of a direct current power source capable of a power supply and absorption is connected to a midpoint between the arms, while the other terminal thereof is connected to a neutral point of motor coils or generator coils, thereby eliminating a need for a large volumetric reactor in a direct current chopper, achieving a downsizing of the circuit.

Journal ArticleDOI
TL;DR: In this paper, a high-efficiency active full-wave rectifier in standard CMOS technology is presented, taking advantage of the dynamic voltage control of its separated n-well regions, where the main rectifying PMOS elements have been implemented in order to eliminate latch-up and body effect.
Abstract: In this paper we present analysis, design, and implementation of a high-efficiency active full-wave rectifier in standard CMOS technology. The rectifier takes advantage of the dynamic voltage control of its separated n-well regions, where the main rectifying PMOS elements have been implemented in order to eliminate latch-up and body effect. To minimize rectifier dropout and improve AC---DC power conversion efficiency (PCE), all the MOSFET switching elements have been pushed into deep triode region to minimize their resistance along the main current path during conduction. A prototype rectifier was implemented in the AMI 0.5-μm 3M/2P n-well CMOS process. An input sinusoid of 5 V peak at 0.5 MHz produced 4.36 V DC output across a $$1\,\hbox{k}\Upomega\Vert 1\,\mu\hbox{F}$$ load, resulting in a measured PCE of 84.8%.

Proceedings Article
06 Oct 2009
TL;DR: In this article, an analytical state-space average-value model of the direct symmetric topology of an 18-pulse AC-DC rectifier is derived, and the dynamic characteristics of the rectifier are fully represented while the model is time invariant and computationally efficient.
Abstract: The paper derives an analytical state-space average-value model of the direct symmetric topology of an 18-pulse AC-DC rectifier. The dynamic characteristics of the rectifier are fully represented while the model is time invariant and computationally efficient. The developed model, validated with comparison of the resultant transient and steady state behaviors with those obtained from detailed simulations of a test system including synchronous generator and DC loads can, therefore, be used for stability assessment of electric power systems with diode rectifiers, multiple power electronic converter-controlled loads and electrical drives.

Patent
09 Dec 2009
TL;DR: In this article, an electrical circuit for use with a generator having an output port, the circuit to modify one of an electric current or voltage from the generator, is described, where the generator is a linear alternator positioned within an energy converting apparatus comprising a Stirling engine having a piston such that motion of the piston drives the linear alternators.
Abstract: In one aspect the invention relates to an electrical circuit for use with a generator having an output port, the circuit to modify one of an electric current or voltage from the generator. The circuit includes a rectifier to convert the alternating current from the generator to direct current, the rectifier having a first port and a second port, the rectifier first port in communication with the output port of the generator; and a direct current to alternating current inverter to convert the direct current from the rectifier to alternating current, the inverter having a first port and a second port, the first port of the inverter in communication with the second port of the rectifier. In one embodiment, the generator is a linear alternator positioned within an energy converting apparatus comprising a Stirling engine having a piston such that motion of the piston drives the linear alternator.

Proceedings ArticleDOI
Guoxing Zhang1, Junming Zhang1, Zhao Chen1, Xinke Wu1, Zhaoming Qian1 
06 Nov 2009
TL;DR: In this article, the authors proposed a current-driven synchronous rectifier with a voltage-doubler rectifier, which reduced the voltage stress across SRs to half of that in a center-tapped rectifier.
Abstract: This paper proposes a current driving scheme for synchronous rectifier (SR) in the LLC resonant converter with a voltage-doubler rectifier. The voltage-doubler rectifier has a simple-structure transformer which only needs one winding on the secondary side. The voltage stress across SRs is reduced to half of that in a center-tapped rectifier, which means SRs with smaller on resistance can be used. With one Current Transformer (CT), the proposed current-driven SR features simple and well performs. Most of the reflected current from the CT will be feed backed to the output so that the power loss is low. Due to the current balance in the two output capacitors of the voltage-doubler rectifier, the magnetic balance circuit for the CT is not required. A prototype with 300–400V input and 16V/5.6A output is built to verify the theoretical analysis, and efficiency of the converter is up to 93.5% at 350Vin and full load condition.

Journal ArticleDOI
TL;DR: This paper proposes and implements a new permanent-magnet brushless dc (BLDC) generator using 12-phase half-wave rectifier, and it is shown that the current stress of diodes in 12- Phase rectification system is less than half of that in double-star rectifier system, and the output voltage fluctuation between the two different rectification systems is similar.
Abstract: Six-phase double-star armature windings of a synchronous generator are essentially equivalent to 12-phase symmetrical windings displaced in turn by 30deg. This paper proposes and implements a new permanent-magnet brushless dc (BLDC) generator using 12-phase half-wave rectifier. Characteristic of output voltage is analyzed according to the star graph of slot potential, and the design constraints of armature windings are provided. Simulation models of 12-phase synchronous generator with half-wave rectifier and double-star synchronous generator with bridge rectifier are established separately. Field-circuit-coupled analysis is accomplished, and conducted modes of rectified diodes and output characteristic are obtained. It is shown that the current stress of diodes in 12-phase rectification system is less than half of that in double-star rectification system, and the output voltage fluctuation between the two different rectification systems is similar. Experimental results on prototype machine, which agree well with the simulation analysis, also verify the feature of the proposed BLDC generator system.

Proceedings ArticleDOI
21 Mar 2009
TL;DR: In this paper, a three-phase?-switch rectifier (comprising three?-connected bidirectional switches) is proposed for the PWM current controller, where all three phases are controlled simultaneously.
Abstract: In the course of the More Electric Aircraft program active three-phase rectifiers in the power range of 5 kW are required. A comparison with other rectifier topologies shows that the three-phase ?-switch rectifier (comprising three ?-connected bidirectional switches) is well suited for this application. The system is analyzed using space vector calculus and a novel PWM current controller concept is presented, where all three phases are controlled simultaneously; the analysis shows that the proposed concept yields optimized switching sequences. To facilitate the rectifier design, analytical relationships for calculating the power components average and rms current ratings are derived. Furthermore, a laboratory prototype with an output power of 5 kW is realized. Measurements taken from this prototype confirm the operation of the proposed current controller. Finally, initial EMI-measurements of the system are also presented.

Patent
06 Mar 2009
TL;DR: In this paper, a double-ended isolated DC-DC converter with a main transformer and first and second pulse transformers is considered, where a first power switch of a primary side circuit and a first synchronous rectifier of a secondary side circuit are driven with complementary timing.
Abstract: In a double-ended isolated DC-DC converter, by using a main transformer and first and second pulse transformers, a first power switch of a primary side circuit and a first synchronous rectifier of a secondary side circuit are driven with complementary timing, and a second power switch of the primary side circuit and a second synchronous rectifier of the secondary side circuit are driven with complementary timing. A first turn-off edge signal and a first turn-on edge signal generated in a primary side control circuit are transmitted to the secondary side via the first pulse transformer so as to generate a driving signal of the first synchronous rectifier. In addition, a second turn-off edge signal and a second turn-on edge signal generated in a primary side circuit are transmitted to the secondary side via the second pulse transformer so as to generate a driving signal of the second synchronous rectifier.

Proceedings ArticleDOI
01 Dec 2009
TL;DR: A 2.4 GHz band high-efficiency RF rectifier and high sensitive dc voltage sensing circuit is implemented, using native threshold voltage diode-connected NMOS transistors to avoid the power loss due to the threshold voltage.
Abstract: A 2.4 GHz band high-efficiency RF rectifier and high sensitive dc voltage sensing circuit is implemented. A passive RF to DC rectifier of multiplier voltage type has no current consumption. This rectifier is using native threshold voltage diode-connected NMOS transistors to avoid the power loss due to the threshold voltage. It consumes only 900nA with 1.5V supply voltage adopting ultra low power DC sensing circuit using subthreshold current reference. These block incorporates a digital demodulation logic blocks. It can recognize OOK digital information and existence of RF input signal above sensitivity level or not. A low power RF rectifier and DC sensing circuit was fabricated in 0.18um CMOS technology with native threshold voltage NMOS; This RF wake up receiver has -28dBm sensitivity at 2.4 GHz band.

Proceedings ArticleDOI
12 Jul 2009
TL;DR: In this article, a secondary diode charge pump is used to generate the DC bias for the threshold voltage compensation, and the circuit is implemented in a standard CMOS technology and operates at a minimum available power of −11.3 dBm for an output DC power of 7.5 µW.
Abstract: The operating range of passive UHF transponder systems is largely determined by the tag current consumption and the rectifier efficiency. Reading ranges of several meters have recently been reported for many state of the art RFID (Radio frequency IDentification) tags [1]. At this distance, the main issue for the rectifier design is the low amplitude of the high frequency antenna signal. Schottky diodes are often used for their low forward voltage drop and high switching speed. As an alternative to Schottky diodes, different circuit techniques for compensating the threshold voltage of standard transistor diodes have been utilized [4]. The transistor gates are biased near the threshold voltage, so that the devices effectively act as diodes with very low forward voltage drop. In the presented rectifier, a secondary diode charge pump is used to generate the DC bias for the threshold voltage compensation. The circuit is implemented in a standard CMOS technology and operates at a minimum available power of −11.3 dBm for an output DC power of 7.5 µW.

Proceedings ArticleDOI
01 Oct 2009
TL;DR: In this article, the use of a single-switch three-phase boost rectifier in the front end of the power electronic interface is discussed for low and medium power wind energy conversion systems (WECS).
Abstract: Low and medium power wind energy conversion systems (WECS) are expected to be simple, low cost and reliable. They are usually implemented with fixed pitch wind turbines. In such a case, operation with variable speed for increased capture of wind energy requires a power electronics converter capable of adjusting the shaft speed. This is done by controlling the active power drawn from the generator. Permanent magnet synchronous generators (PMSG) are a good option for low power variable speed WECS since they do not require external excitation nor reactive power to operate. Typically, an ac-dc converter composed of a diode rectifier and a capacitive filter, connected to a voltage source inverter is used as an interface to a grid or to a load. The highly distorted input currents of the diode rectifier with capacitive filters produce additional power losses in the generator that can reduce its lifetime. This paper discusses the use of a single-switch three-phase boost rectifier in the front end of the power electronic interface. It provides means for regulating the shaft speed by duty cycle variation while reducing the generator losses when compared to the standard diode and capacitive filter scheme. Simulation and experimental results show the effectiveness of the proposed scheme for reducing the generator copper and core losses and also the internal temperature.

Proceedings ArticleDOI
04 Dec 2009
TL;DR: A new topology of three-phase controlled rectifier feasible for high power wind energy conversion systems (WECS) is proposed, based on the bridgeless rectifier, which allows the operation with high power factor, increasing the generator efficiency.
Abstract: In this paper it is proposed a new topology of three-phase controlled rectifier feasible for high power wind energy conversion systems (WECS). This rectifier is based on the bridgeless rectifier, uses six wires of the generator, and allows the operation with high power factor, increasing the generator efficiency. One Cycle Control (OCC), which avoids the need of sinusoidal reference signals, was used in the rectifier control. This study is then concerned with the operation principle and experimental results obtained from a 5 kVA prototype.

Proceedings ArticleDOI
28 Sep 2009
TL;DR: This paper proposes a design of a power harvester for a semi-passive RFID Tag that can be achieved with the tunable impedance matching circuit and conventional 2-stage rectifier.
Abstract: This paper proposes a design of a power harvester for a semi-passive RFID Tag. A tunable impedance transformation circuit is inserted between the antenna and the rectifier unit to maximize the power delivered to the rectifier of a tag and minimize reflections from the antenna input port. A power harvester for the UHF band of 950 MHz has been designed based on a 0.35 µm CMOS technology. This impedance matching is designed to maximize efficiency by characterizing both the tunable impedance transformation circuit and the conventional rectifier circuit. The antenna is modeled as an RF source with series impedance Z S of 50Ω while the rectifier is modeled an impedance Z L , which is approximated from the process and design parameters of the NMOS transistors used in the conventional NMOS rectifier. These two impedances are used to find optimal matching parameters of the chosen lowpass LL matching circuit. The simulation results show that the required voltage for a 1.2V secondary battery can be achieved with the tunable impedance matching circuit and conventional 2-stage rectifier. The DC output of the rectifier yields the maximum DC voltage of 1.77V, the maximum average current of 4.72µA, and the power conversion efficiency of 15.85% for the input RF power of −14.47dBm at the battery voltage of 1.2V.

Patent
29 Dec 2009
TL;DR: In this article, a variable frequency drive (VFWD) is defined, where a diode rectifier receives multiphase AC power from a source and converts the AC power to DC power to drive a load.
Abstract: A variable frequency drive comprises a diode rectifier receiving multiphase AC power from a source and converting the AC power to DC power. An inverter receives DC power and converts the DC power to AC power to drive a load. A link circuit is connected between the diode rectifier and the inverter and comprises a DC bus to provide a relatively fixed DC voltage for the inverter. A bus capacitor is across the bus. A soft charge circuit limits inrush current to the bus capacitor. The soft charge circuit comprises an inductor connected between the source and the link circuit and a switch circuit in the link circuit for selectively providing a semiconverter configuration or a full bridge converter configuration to provide two stage charging of the bus capacitor.

Patent
23 Dec 2009
TL;DR: In this paper, a flyback converter utilizes a boost inductor coupled between a source of AC power and a bridge rectifier to provide power factor correction, and the primary winding of the flyback transformer is coupled in series with a storage capacitor across the output of the bridge rectifiers.
Abstract: A flyback converter utilizes a boost inductor coupled between a source of AC power and a bridge rectifier to provide power factor correction. A primary winding of the flyback transformer is coupled in series with a storage capacitor across the output of the bridge rectifier. A circuit, which includes a switching transistor, is also coupled across the output of the bridge rectifier to provide a low resistance path when the switch is closed. The cores of the boost inductor and the transformer are loaded with energy when the switch is closed. When the switch opens, the energy stored in the magnetic cores is transferred to the output via the transformer secondary winding and rectification circuitry.

Patent
04 Nov 2009
TL;DR: In this paper, an autotransformer with 15 inductors coupled in series, joined by 15 nodes interposed between pairs of the inductors, is represented as a hexagon in which alternating sides of the hexagon have two and three inductors.
Abstract: Embodiments of the present invention provide novel techniques for using multiple 18-pulse rectifier circuits in parallel. In particular, each rectifier circuit may include an autotransformer having 15 inductors coupled in series, joined by 15 nodes interposed between pairs of the inductors. The inductors may be represented as a hexagon in which alternating sides of the hexagon have two and three inductors, respectively. Each rectifier circuit may also include three inputs for three-phase AC power coupled to alternating vertices of the hexagonal representation and nine outputs for AC power coupled between each node that is not a vertex of the hexagonal representation and a respective diode bridge. Outputs of the diode bridges for the rectifier circuits may be coupled to a DC bus. In addition, a means for reducing circulating current between the parallel rectifier circuits and for promoting load sharing between the parallel rectifier circuits is also provided.

Patent
30 Oct 2009
TL;DR: In this article, a current-type rectifier circuit having a filter circuit and first bidirectional switches bridge-connected to the filter circuit is provided in an output of an AC power supply.
Abstract: In an AC motor driving circuit, a current-type rectifier circuit having a filter circuit and first bidirectional switches bridge-connected to the filter circuit is provided in an output of an AC power supply An AC motor is connected to an output of the rectifier circuit through a voltage-type inverter One terminal of each of second bidirectional switches is connected to corresponding one of output terminals of the current-type rectifier circuit The other terminals of the second bidirectional switches are collectively connected to one terminal of a series circuit having a DC power supply and a reactor The other terminal of the series circuit is connected to one output terminal of the current-type rectifier circuit With this configuration, a large capacitor for a DC link can be dispensed with, so that a reduction in circuit size and weight can be attained