Showing papers on "Buck converter published in 2006"

Design of a maximum power tracking system for wind-energy-conversion applications

Abstract: A wind-generator (WG) maximum-power-point-tracking (MPPT) system is presented, consisting of a high-efficiency buck-type dc/dc converter and a microcontroller-based control unit running the MPPT function. The advantages of the proposed MPPT method are that no knowledge of the WG optimal power characteristic or measurement of the wind speed is required and the WG operates at a variable speed. Thus, the system features higher reliability, lower complexity and cost, and less mechanical stress of the WG. Experimental results of the proposed system indicate near-optimal WG output power, increased by 11%-50% compared to a WG directly connected via a rectifier to the battery bank. Thus, better exploitation of the available wind energy is achieved, especially under low wind speeds.

A Novel Soft-Commutating Isolated Boost Full-Bridge ZVS-PWM DC–DC Converter for Bidirectional High Power Applications

Abstract: A soft-commutating method and control scheme for an isolated boost full bridge converter is proposed in this paper to implement dual operation of the well-known soft-switching full bridge dc/dc buck converter for bidirectional high power applications. It provides a unique commutation logic to minimize a mismatch between current in the current-fed inductor and current in the leakage inductance of the transformer when commutation takes place, significantly reducing the power rating for a voltage clamping snubber and enabling use of a simple passive clamped snubber. To minimize the mismatch, the method and control scheme utilizes the resonant tank and freewheeling path in the existing full bridge inverter at the voltage-fed side to preset the current in the leakage inductance of the transformer in a resonant manner. Zero-voltage-switching is also achieved for all the switches at the voltage-fed side inverter in boost mode operation. The proposed soft-commutating method is verified through boost mode operation of a 3-kW bidirectional isolated full bridge dc/dc converter developed for fuel cell electric vehicle applications. The tested result verified the isolated boost converter can operate at an input voltage of 8.5–15V and an output voltage of 250–420V with a peak efficiency of 93% and an average efficiency of 88% at 55-kHz switching frequency with 72 $^circ$ C automotive coolant.

A Digital Current-Mode Control Technique for DC–DC Converters

Abstract: The objective of this paper is to propose a simple digital current mode control technique for dc-dc converters. In the proposed current-mode control method, the inductor current is sampled only once in a switching period. A compensating ramp is used in the modulator to determine the switching instant. The slope of the compensating ramp is determined analytically from the steady-state stability condition. The proposed digital current-mode control is not predictive, therefore the trajectory of the inductor current during the switching period is not estimated in this method, and as a result the computational burden on the digital controller is significantly reduced. It therefore effectively increases the maximum switching frequency of the converter when a particular digital signal processor is used to implement the control algorithm. It is shown that the proposed digital method is versatile enough to implement any one of the average, peak, and valley current mode controls by adjustment of the sampling instant of the inductor current with respect to the turn-on instant of the switch. The proposed digital current-mode control algorithm is tested on a 12-V input and 1.5-V, 7-A output buck converter switched at 100kHz and experimental results are presented

Three-level buck converter for envelope tracking applications

Abstract: This letter proposes a three-level buck converter for tracking applications such as envelope-tracking in radio frequency power amplifiers (RFPAs). It is shown that the three-level buck converter can offer advantages in terms of switching ripples, losses, bandwidth, or the size of magnetic components compared to a standard buck or a two-phase buck converter. Experimental results illustrate improved efficiency and ripple rejection in an RFPA envelope-tracking application representative for low-power battery-operated systems.

Multi-voltage CMOS Circuit Design

Abstract: List of Tables. List of Figures. Preface. 1 Introduction. 1.1 Evolution of Integrated Circuits. 1.2 Outline of the Book. 2 Sources of Power Consumption in CMOS Integrated Circuits. 2.1 Dynamic Switching Power. 2.2 Leakage Power. 2.3 Short-Circuit Power. 2.4 Static DC Power. 3 Supply and Threshold Voltage Scaling Techniques. 3.1 Dynamic Supply Voltage Scaling. 3.2 Multiple Supply Voltage CMOS. 3.3 Threshold Voltage Scaling. 3.4 Multiple Supply and Threshold Voltage CMOS. 3.5 Dynamic Supply and Threshold Voltage Scaling. 3.6 Circuits with Multiple Voltage and Clock Domains. 3.7 Chapter Summary. 4 Low Voltage Power Supplies. 4.1 Linear DC-DC Converters. 4.2 Switched-Capacitor DC-DC Converters. 4.3 Switching DC-DC Converters. 4.4 Chapter Summary. 5 Analysis of Buck Converters for On-Chip Integration with a Dual Supply Voltage Microprocessor. 5.1 Circuit Model of a Buck Converter. 5.2 Efficiency Analysis of a Buck Converter. 5.3 Simulation Results. 5.4 Chapter Summary. 6 Low Voltage Swing Monolithic DC-DC Conversion. 6.1 Circuit Model of a Low Voltage Swing Buck Converter. 6.2 Low Voltage Swing Buck Converter Analysis. 6.3 Chapter Summary. 7 High Input Voltage Step-Down DC-DC Converters for Integration in a Low Voltage CMOS Process. 7.1 Cascode Bridge Circuits. 7.2 High Input Voltage Monolithic Switching DC-DC Converters. 7.3 Chapter Summary. 8 Signal Transfer in Integrated Circuits with Multiple Supply Voltages. 8.1 A High Speed and Low Power Voltage Interface Circuit. 8.2 Voltage Interface Circuit Simulation Results. 8.3 Experimental Results. 8.4 Chapter Summary. 9 Domino Logic with Variable Threshold Voltage Keeper. 9.1 Standard Domino Logic Circuits. 9.2 Domino Logic with Variable Threshold Voltage Keeper. 9.3 Simulation Results. 9.4 Domino Logic with Forward and Reverse Body Biased Keeper. 9.5 Chapter Summary. 10 Subthreshold Leakage Current Characteristics of Dynamic Circuits. 10.1 State Dependent Subthreshold Leakage Current Characteristics. 10.2 Noise Immunity. 10.3 Power and Delay Characteristics in the Active Mode. 10.4 Dual Threshold Voltage CMOS Technology. 10.5 Chapter Summary. 11Sleep Switch Dual Threshold Voltage Domino Logic with Reduced Standby Leakage Current. 11.1 Previously Published Sleep Mode Circuit Techniques. 11.2 Dual Threshold Voltage Domino Logic Employing Sleep Switches. 11.3 Simulation Results. 11.4 Noise Immunity Compensation. 11.5 Chapter Summary. 12 Conclusions. Bibliography. Index. About the Authors.

Sensorless optimization of dead times in dc–dc converters with synchronous rectifiers

Abstract: This paper introduces an approach to achieve optimum dead times in dc–dc converters with synchronous rectifiers without sensing any of the power-stage signals other than the output voltage. The dead times are adjusted adaptively to minimize the duty-cycle command, which results in maximization of the converter efficiency. The method is particularly well suited for digital controller implementation, requiring no additional analog components or modifications of standard gate-drive circuitry. Experimental results for a digitally controlled 5 V-to-1 V, 5-A synchronous buck converter demonstrate practical implementation of the sensorless dead-time optimization algorithm.

Adaptive feedforward and feedback control schemes for sliding mode controlled power converters

Abstract: A major disadvantage of applying sliding mode control to dc/dc converters is that the steady-state switching frequency is affected by line and load variations This is undesirable as it complicates the design of the input and output filters To reduce switching frequency deviation in the events of line and load variations, an adaptive feedforward control scheme that varies the hysteresis band according to the change of line input voltage and an adaptive feedback control scheme that varies the control parameter (ie, sliding coefficient) according to the change of the output load are proposed This paper presents a thorough investigation into the problem and the effectiveness of the proposed solutions In addition, methods of implementing the proposed adaptive control strategies are discussed Experimental results confirm that the adaptive control schemes are capable of reducing the switching frequency variations caused by both line and load variations

A high efficiency, soft switching DC-DC converter with adaptive current-ripple control for portable applications

Abstract: A novel control scheme for improving the power efficiency of low-voltage dc-dc converters for battery-powered, portable applications is presented. In such applications, light-load efficiency is crucial for extending battery life, since mobile devices operate in stand-by mode for most of the time. The proposed technique adaptively reduces the inductor current ripple with decreasing load current while soft switching the converter to also reduce switching losses, thereby significantly improving light-load efficiency and therefore extending the operation life of battery-powered devices. A load-dependent, mode-hopping strategy is employed to maintain high efficiency over a wide load range. Hysteretic (sliding-mode) control with user programmable hysteresis is implemented to adaptively regulate the current ripple and therefore optimize conduction and switching losses. Experimental results show that for a 1-A, 5- to 1.8-V buck regulator, the proposed technique achieved 5% power efficiency improvement (from 72% to 77%) at 100 mA of load current and a 1.5% improvement (from 84% to 85.5%) at 300 mA, which constitute light-load efficiency improvements, when compared to the best reported, state-of-the-art techniques. As a result, the battery life in a typical digital signal processing microprocessor application is improved by 7%, which demonstrates the effectiveness of the proposed solution.

Hybrid Full-Bridge Three-Level LLC Resonant Converter—A Novel DC–DC Converter Suitable for Fuel-Cell Power System

Abstract: This paper proposes a novel hybrid full-bridge (H-FB) three-level (TL) LLC resonant converter. It integrates the advantages of the H-FB TL converter and the LLC resonant converter. It can operate under both three-level mode and two-level mode, so it is very suitable for wide-input-voltage-range applications, such as fuel-cell power systems. Compared with the traditional full-bridge converter, the input current ripple and output filter can be reduced. In addition, all the switches can realize zero-voltage switching from nearly zero to full load, and the switches of the TL leg sustain only half of the input voltage. Moreover, the rectifier diodes can achieve zero-current switching, and the voltage stress across them can be minimized to the output voltage. A prototype of 200-400-V input and 360-V/4-A output is built in our laboratory to verify the operation principle of the proposed converter

Novel Solar-Cell Power Supply System Using a Multiple-Input DC–DC Converter

Abstract: Recently, the clean electric power generation systems have attracted a great deal of social attention to exploit the clean-energy resources such as solar arrays, wind generators, fuel cells, and so forth. In this case, a multiple-input dc–dc converter is useful to combine the several input power sources and to supply the regulated output voltage for the load from the power sources. The novel solar-cell power supply system using the buck–boost-type two-input dc–dc converter is proposed, in which a solar array and a commercial ac line are employed as power sources and are combined by two input windings of the energy-storage reactor. Also, its operation principle and performance characteristics are discussed. Furthermore, the solar-cell optimum-operating-point tracker is proposed and examined. It is confirmed by the experiment that the proposed solar-cell power supply system has excellent performance characteristics.

A neutral-point clamped converter system for direct-drive variable-speed wind power unit

Abstract: Recent and ongoing developments in wind turbine technology indicate a trend towards utilization of high capacity (e.g., up to 5 MW) wind power units in large wind farms. Higher capacity of the wind turbine necessitates operation of the corresponding electric machine and the static converter system at higher voltages. This paper presents a neutral point diode clamped (NPC) converter system that inherently accommodates higher voltage and power ratings of a high capacity wind power unit. The overall control strategy of an NPC-based wind power unit and the details of the ac side and the dc side controls of the NPC converter system are also described. The generator-side NPC converter provides torque-speed control of the turbine-generator unit. The network-side NPC converter controls real and reactive power flow to the network and thus regulates the dc bus voltage and the ac side power-factor (or voltage) respectively. The paper also presents a new control approach to balance the dc capacitor voltages. The NPC converter system is augmented with a dc chopper that controls the synchronous generator field current. The NPC-based converter system is used to interface a 3 MW, direct-drive (gearless), synchronous machine based wind power unit to the utility grid. Performance of the overall NPC-based wind power unit, under the proposed controls, is evaluated based on time domain simulations in the power systems computer aided design (PSCAD) electromagnetic transient for DC (EMTDC) environment.

High-Power Density Design of a Soft-Switching High-Power Bidirectional DC-DC Converter

Abstract: A typical non-isolated bi-directional dc-dc converter technology is to combine a buck converter and a boost converter in a half-bridge configuration. In order to have high-power density, the converter can be designed to operate in discontinuous conducting mode (DCM) such that the passive inductor can be minimized. The DCM associated current ripple can be alleviated by multiphase interleaved operation. However DCM operation tends to increase turn-off loss because of a high peak current and its associated parasitic ringing due to the oscillation between the inductor and the device output capacitance. Thus the efficiency is suffered with the conventional DCM operation. Although to reduce the turn-off loss, a lossless capacitor snubber can be added across the switch, the energy stored in the capacitor needs to be discharged before device is turned on in order to realize zero-voltage switching. This paper adopts a gate signal complimentary control scheme to turn on the non-active switch and divert the current into the anti-paralleled diode of the active switch so that the main switch can turn on under zero-voltage condition. Thus both soft switching turn-on and turn-off are achieved. This diverted current also eliminates the parasitic ringing in inductor current. For capacitor value selection, there is a trade-off between turn-on and turn-off losses. This paper suggests the optimization of capacitance selection through a series of hardware experiments to ensure the overall power loss minimization under complimentary DCM operating condition. A 100kW hardware prototype is constructed and tested. The experimental results are provided to verify the proposed design approach.

Characterization and performance comparison of ripple-based control for voltage regulator modules

Abstract: Three recently developed control methods for voltage regulator modules, namely, V/sup 2/ control, enhanced V/sup 2/ control, and enhanced V/sup 2/ control without output voltage dynamic feedback, are analyzed and compared in this paper. All three methods utilize the output voltage switching ripple for pulse-width modulation (PWM), hence, are collectively referred to as ripple-based control. A general modeling method based on the Krylov-Bogoliubov-Mitropolsky ripple estimation technique is applied to develop averaged models for single-channel as well as multichannel buck converters employing each of the control methods. Unlike existing models that are limited to small-signal operation, the proposed models are valid for large-signal operation and are capable of predicting subharmonic instability without including any sample-and-hold block as used in previous models. The paper also shows that adding parallel, high-quality ceramic capacitors at the output, which are ignored in previous models, can lead to pulse skipping and ripple instability, and a solution based on proper selection of the ceramic capacitors and/or ramp compensation at the PWM is presented. The models are further applied to analyze and compare the performance of the three control methods in terms of ripple stability, effective load current feedforward gain, and output impedance.

Method and apparatus for controlling power drawn from an energy converter

Abstract: Methods, apparatus, media and signals for controlling power drawn from an energy converter to supply a load, where the energy converter is operable to convert energy from a physical source into electrical energy. Power drawn from the energy converter is changed when a supply voltage of the energy converter meets a criterion. The criterion and the change in the amount of power drawn from the energy converter are dependent upon a present amount of power supplied to the load. The methods, apparatus, media and signals described herein may provide improvements to DC to AC maximum power point tracking in an energy conversion system such as a photovoltaic power generation system.

LMI-based Integral fuzzy control of DC-DC converters

Abstract: In this paper, we propose a T-S fuzzy controller which combines the merits of: i) the capability for dealing with nonlinear systems; ii) the powerful LMI approach to obtain control gains; iii) the high performance of integral controllers; iv) the workable rigorous proof for exponential convergence of error signals; and v) the flexibility on tuning decay rate. The output regulation problems of a basic buck converter and a zero-voltage-transition (ZVT) buck converter are used as application examples to illustrate the control performance of the proposed methodology. First, we consider a general nonlinear system which can represent the large-signal models of the converters. After introducing an added integral state of output regulation error and taking coordinate translation on an equilibrium point, the resulting augmented system is represented into a Takagi-Sugeno (T-S) fuzzy model. Then, the concept of parallel distributed compensation is applied to design the control law whereby the control gains are obtained by solving linear matrix inequalities (LMIs). An interesting result is that the obtained control law is formed only by the linear state feedback signals weighted by grade functions. In addition, the robustness analysis is carried out when uncertainty and disturbance are taken into consideration. The performance of numerical simulations and practical experiments results is satisfactory.

Digital control of a voltage-mode synchronous buck converter

Abstract: A digital control algorithm capable of separately specifying the desired output voltage and transient response for a synchronous buck converter operating in voltage mode was developed. This algorithm is based on superimposing a small control signal onto a voltage reference at each switching cycle to cancel out the perturbations. A zero steady-state error in the output voltage can be obtained with the aid of additional dynamics to allow the controller to track a load change and update the reference to a new load state. The specifications of the control algorithm are achieved by pole placement using complete state feedback. The control algorithm was implemented on a digital signal processor (DSP)-controlled synchronous buck converter.

Analysis and Design of a New High-Efficiency Bidirectional Integrated ZVT PWM Converter for DC-Bus and Battery-Bank Interface

Abstract: This paper proposes a high-efficiency bidirectional integrated zero-voltage transition (iZVT) pulsewidth-modulation (PWM) converter for dc-bus and battery-bank interface. The proposed converter can operate as battery charger when the utility is within its acceptable voltage range and can supply energy to critical loads when the utility fails. The converter practically eliminates both low- and high-frequency current ripple on the batteries, thus maximizing battery life without penalizing the volume of the converter. Moreover, soft switching of all switches is achieved using the proposed integrated auxiliary commutation circuit (iACC). Just one iACC is used to provide soft-switching conditions for the three converters that compose the system: the preregulator (boost), the battery charger (bidirectional converter operating as a buck), and the backup converter (bidirectional converter operating as a boost). This auxiliary circuit has few components and low reactive energy, increasing the system's overall efficiency. Experimental results based on a 580-W prototype are presented to validate the analysis and the proposed design procedure and to demonstrate the performance of the proposed approach

Efficiency improvement in multiphase converter by changing dynamically the number of phases

Abstract: In this paper a simple technique to improve the efficiency on multiphase converters is explored. The number of phases is dynamically changed in order to reduce power losses at light load. Theoretical considerations about the application field of this technique and the influence on the output capacitor are provided. Moreover, practical aspects such as influence of MOSFET driver and DC current sharing among phases should be taken into account. Experimental results show that this technique allows important improvements in the efficiency while maintaining satisfactory current sharing in the connection/disconnection of the phases.

Selection of a curved switching surface for buck converters

Abstract: A general procedure for the selection of a curved switching surface (SS) to control buck-type converters is presented in this letter. The analysis is based on the normalized representation of ideal SSs for different loading conditions. The normalization process leads to a unique representation of the SSs for any possible buck converter. A set of graphics in three dimensions is introduced to give a spatial sense of the behavior of the converter and its control requirements during transients. As a result of the investigation, a switching surface referred to in this letter as the natural unloaded SS is selected, providing excellent transient behavior and no overshoot during startup. For any buck converter with typical parameters, this control scheme produces, in one switching action, a minimum of 99% of the desired output voltage. The general concept of using second-order SS is also geometrically analyzed in this letter to clarify its characteristic features and disadvantages. Experimental results for a typical buck converter are presented to illustrate the transient behavior of the converter during startup and sudden load changes. The results confirm the virtues of the control scheme.

Digital Multimode Buck Converter Control With Loss-Minimizing Synchronous Rectifier Adaptation

Abstract: This paper develops a multimode control strategy which allows for efficient operation of the buck converter over a wide load range. A method for control of synchronous rectifiers as a direct function of the load current is introduced . The function relating the synchronous-rectifier timing to the load current is optimized on-line with a gradient power-loss-minimizing algorithm. Only low-bandwidth measurements of the load current and a power-loss-related quantity are required, making the technique suitable for digital controller implementations. Compared to alternative loss-minimizing approaches, this method has superior adjustment speed and robustness to disturbances, and can simultaneously optimize multiple parameters. The proposed synchronous-rectifier control also accomplishes an automatic, optimal transition to discontinuous-conduction mode at light load. Further, by imposing a minimum duty-ratio, the converter automatically enters pulse-skipping mode at very light load. Thus, the same controller structure can be used in both fixed-frequency pulsewidth modulation and variable-frequency pulse-skipping modes. These techniques are demonstrated on a digitally-controlled 100-W buck converter

Power Converter EMI Analysis Including IGBT Nonlinear Switching Transient Model

Abstract: It is well known that very high dv/dt and di/dt during the switching instant is the major high-frequency electromagnetic interference (EMI) source. This paper proposes an improved and simplified EMI-modeling method considering the insulated gate bipolar transistor switching-behavior model. The device turn-on and turn-off dynamics are investigated by dividing the nonlinear transition by several stages. The real device switching voltage and current are approximated by piecewise linear lines and expressed using multiple dv/dt and di/dt superposition. The derived EMI spectra suggest that the high-frequency noise is modeled with an acceptable accuracy. The proposed methodology is verified by experimental results using a dc-dc buck converter

Multifrequency Small-Signal Model for Buck and Multiphase Buck Converters

Abstract: To investigate the high-frequency behaviors of buck and multiphase buck converters, this paper develops a modeling method based on the harmonic-balance approach. Because the nonlinear pulse-width modulator generates sideband components, the sideband effect occurs in a closed-loop converter. Taking this effect into account, the multifrequency small-signal model is proposed, which is applicable beyond half of the switching frequency. In a voltage-mode-controlled buck converter, the introduced model predicts the measured phase delay of the loop gain, while the conventional average model fails to explain this phenomenon. Furthermore, this model is extended to the case of the multiphase buck converter. The influence from the interleaving technique is discussed and the frequency-domain characteristics are clearly explained. Simulation and experimental results are provided to verify the achievements of the proposed model

Multiphase buck converters with extended duty cycle

Abstract: A family of multiphase, pulse-width-modulated (PWM) step-down converters that exhibit high input-to-output voltage conversion ratios is introduced. The proposed converters operate with larger duty cycles and lower voltage stresses on the switches than their conventional converter counterparts making them suitable for applications in high-frequency, nonisolated point-of-load converters employed in powering today's microprocessors.

Apparatus and method for PFM buck-or-boost converter with smooth transition between modes

Abstract: A PWM buck-or-boost converter is provided. The converter includes an error amplifier, a rectifier/splitter, a first comparator, and a second comparator. The rectifier/splitter provides two signals proportional to the departure of the error voltage from a central value but increasing in value from zero. Only one of the two signals departs from zero depending on the error voltage. The first comparator compares one of the two signals to a modulating waveform (e.g. a sawtooth waveform), and the second comparator compares the other of the two signals to the modulating waveform. Only one of the two signals intersects the modulating waveform depending on the error voltage. During buck regulation, the first comparator controls the buck switches and the output of the second comparator remains high. During boost regulation, the second comparator controls the boost switches and the output of the first comparator remains high.

Method for operation of a converter system

Abstract: The present invention relates to a method for operating a converter system of a wind turbine, wherein the converter system includes converter modules capable of converting electric power produced by a generator to electric power applicable to a utility grid. The converter modules include generator inverters and grid inverters. The method determines the enabling/disabling of the converter modules in response to a parameter related to the variable amount of electric power being produced by the generator. Advantages of the present invention are optimisation of power efficiency of the converter modules and improved reliability of the converter modules. Another advantage is the capability of fast enabling and disabling of the converter modules.

Multiple output power supply that configures itself to multiple loads

Abstract: A two stage multiple output power supply device is capable of outputting programmable DC voltages onto multiple outputs. The first stage receives an AC supply voltage and outputs a DC supply voltage. The second stage includes a DC-ID controller and multiple DC-to-DC converters, each DC-to-DC converter receiving the DC supply voltage and capable of outputting a programmable DC voltage onto a conductor of a power cord to power an electrical device. For each DC-to-DC converter, the DC-ID controller receives information in an AC signal on the conductor, the information indicating the voltage and current requirements and the polarity of an electrical device connected to the power cord for that DC-to-DC converter. In response to the information, the DC-ID controller controls the DC-to-DC converter to set a magnitude, a polarity and a current limit for the programmable DC voltage that will be output by the DC-to-DC converter.

Implementation of a hybrid AC/AC direct power converter with unity voltage transfer ratio

Abstract: This paper presents a novel hybrid direct power converter (HDPC) which overcomes the two main disadvantages of matrix converters: limited voltage transfer ratio and low immunity to grid disturbance. The proposed converter is formed by integrating a reversible auxiliary boost converter in the dc link of the two-stage matrix converter. Therefore, the HDPC can provide unity voltage transfer ratio even in the case where the supply voltage is highly unbalanced. The proposed converter also preserves most of the inherent advantages of the conventional matrix converter such as: controllable input power factor, sinusoidal supply currents, and bidirectional power flow. A novel predictive current control technique for the HDPC is also proposed for minimum energy storage in the converter. Important aspects of design, control, and implementation of the new HDPC are presented including theoretical analysis and simulations. Experimental waveforms at unity voltage transfer using a laboratory prototype are presented to confirm the viability of the proposed idea.

A digitally controlled switch mode power supply based on matrix converter

Abstract: High power telecommunication power supply systems consist of a three-phase switch mode rectifier followed by a dc/dc converter to supply loads at -48 V dc. These rectifiers draw significant harmonic currents from the utility, resulting in poor input power factor with high total harmonic distortion (THD). In this paper, a digitally controlled three-phase switch mode power supply based on a matrix converter is proposed for telecommunication applications. In the proposed approach, the matrix converter directly converts the low frequency (50/60Hz, three-phase) input to a high frequency (10/20kHz, one-phase) ac output without a dc-link. The output of the matrix converter is then processed via a high frequency isolation transformer to produce -48V dc. Digital control of the system ensures that the output voltage is regulated and the input currents are of high quality under varying load conditions. Due to the absence of dc-link electrolytic capacitors, power density of the proposed rectifier is expected to be higher. Analysis, design example and experimental results are presented from a three-phase 208-V, 1.5-kW laboratory prototype converter.