Showing papers on "Buck converter published in 2008"

Pulse-width modulated DC-DC power converters

Abstract: Preface. About the Author. List of Symbols. 1 Introduction. 1.1 Classification of Power Supplies. 1.2 Basic Functions of Voltage Regulators. 1.3 Power Relationships in DC-DC Converters. 1.4 DC Transfer Functions of DC-DC Converters. 1.5 Static Characteristics of DC Voltage Regulators. 1.6 Dynamic Characteristics of DC Voltage Regulators. 1.7 Linear Voltage Regulators. 1.8 Topologies of PWM DC-DC Converters 1.9 Relationships among Current, Voltage, Energy, and Power. 1.10 Electromagnetic Compatibility. 1.11 Summary. 1.12 References. 1.13 Review Questions. 1.14 Problems. 2 BuckPWMDC-DCConverter. 2.1 Introduction. 2.2 DC Analysis of PWM Buck Converter for CCM. 2.3 DC Analysis of PWM Buck Converter for DCM. 2.4 Buck Converter with Input Filter. 2.5 Buck Converter with Synchronous Rectifier. 2.6 Buck Converter with Positive Common Rail. 2.7 Tapped-Inductor Buck Converters. 2.8 Multiphase Buck Converter. 2.9 Summary. 2.10 References. 2.11 Review Questions. 2.12 Problems. 3 Boost PWM DC-DC Converter. 3.1 Introduction. 3.2 DC Analysis of PWM Boost Converter for CCM. 3.3 DC Analysis of PWM Boost Converter for DCM. 3.4 Bidirectional Buck and Boost Converters. 3.5 Tapped-Inductor Boost Converters. 3.6 Duality. 3.7 Power Factor Correction. 3.8 Summary. 3.9 References. 3.10 Review Questions. 3.11 Problems. 4 Buck-Boost PWM DC-DC Converter. 4.1 Introduction. 4.2 DC Analysis of PWM Buck-Boost Converter for CCM. 4.3 DC Analysis of PWM Buck-Boost Converter for DCM. 4.4 Bidirectional Buck-Boost Converter. 4.5 Synthesis of Buck-Boost Converter. 4.6 Synthesis of Boost-Buck (Cuk) Converter. 4.7 Noninverting Buck-Boost Converters. 4.8 Tapped-Inductor Buck-Boost Converters. 4.9 Summary. 4.10 References. 4.11 Review Questions. 4.12 Problems. 5 Flyback PWM DC-DC Converter. 5.1 Introduction. 5.2 Transformers. 5.3 DC Analysis of PWM Flyback Converter for CCM. 5.4 DC Analysis of PWM Flyback Converter for DCM. 5.5 Multiple-Output Flyback Converter. 5.6 Bidirectional Flyback Converter. 5.7 Ringing in Flyback Converter. 5.8 Flyback Converter with Active Clamping. 5.9 Two-Transistor Flyback Converter. 5.10 Summary. 5.11 References. 5.12 Review Questions. 5.13 Problems. 6 Forward PWM DC-DC Converter. 6.1 Introduction. 6.2 DC Analysis of PWM Forward Converter for CCM. 6.3 DC Analysis of PWM Forward Converter for DCM. 6.4 Multiple-Output Forward Converter. 6.5 Forward Converter with Synchronous Rectifier. 6.6 Forward Converters with Active Clamping. 6.7 Two-Switch Forward Converter. 6.8 Summary. 6.9 References. 6.10 Review Questions. 6.11 Problems. 7 Half-Bridge PWM DC-DC Converter. 7.1 Introduction. 7.2 DC Analysis of PWM Half-Bridge Converter for CCM. 7.3 DC Analysis of PWM Half-Bridge Converter for DCM. 7.4 Summary. 7.5 References. 7.6 Review Questions. 7.7 Problems. 8 Full-Bridge PWM DC-DC Converter. 8.1 Introduction. 8.2 DC Analysis of PWM Full-Bridge Converter for CCM. 8.3 DC Analysis of PWM Full-Bridge Converter for DCM. 8.4 Phase-Controlled Full-Bridge Converter. 8.5 Summary. 8.6 References. 8.7 Review Questions. 8.8 Problems. 9 Push-Pull PWM DC-DC Converter. 9.1 Introduction. 9.2 DC Analysis of PWM Push-Pull Converter for CCM. 9.3 DC Analysis of PWM Push-Pull Converter for DCM. 9.4 Comparison of PWM DC-DC Converters. 9.5 Summary. 9.6 References. 9.7 Review Questions. 9.8 Problems. 10 Small-Signal Models of PWM Converters for CCM and DCM. 10.1 Introduction. 10.2 Assumptions. 10.3 Averaged Model of Ideal Switching Network for CCM. 10.4 Averaged Values of Switched Resistances. 10.5 Model Reduction. 10.6 Large-Signal Averaged Model for CCM. 10.7 DC and Small-Signal Circuit Linear Models of Switching Network for CCM. 10.8 Family of PWM Converter Models for CCM. 10.9 PWM Small-Signal Switch Model for CCM. 10.10 Modeling of the Ideal Switching Network for DCM. 10.11 Averaged Parasitic Resistances for DCM. 10.12 Small-Signal Models of PWM Converters for DCM. 10.13 Summary. 10.14 References. 10.15 Review Questions. 10.16 Problems. 11 Open-Loop Small-Signal Characteristics of Boost Converter for CCM. 11.1 Introduction. 11.2 DC Characteristics. 11.3 Open-Loop Control-to-Output Transfer Function. 11.4 Delay in Open-Loop Control-to-Output Transfer Function. 11.5 Open-Loop Audio Susceptibility. 11.6 Open-Loop Input Impedance. 11.7 Open-Loop Output Impedance. 11.8 Open-Loop Step Responses. 11.9 Summary. 11.10 References. 11.11 Review Questions. 11.12 Problems. 12 Voltage-Mode Control of Boost Converter. 12.1 Introduction. 12.2 Circuit of Boost Converter with Voltage-Mode Control. 12.3 Pulse-Width Modulator. 12.4 Transfer Function of Modulator, Boost Converter Power Stage, and Feedback Network. 12.5 Error Amplifier. 12.6 Integral-Single-Lead Controller. 12.7 Integral-Double-Lead Controller. 12.8 Loop Gain. 12.9 Closed-Loop Control-to-Output Voltage Transfer Function. 12.10 Closed-Loop Audio Susceptibility. 12.11 Closed-Loop Input Impedance. 12.12 Closed-Loop Output Impedance. 12.13 Closed-Loop Step Responses. 12.14 Closed-Loop DC Transfer Functions. 12.15 Summary. 12.16 References. 12.17 Review Questions. 12.18 Problems. 13 Current-Mode Control. 13.1 Introduction. 13.2 Principle of Operation of PWM Converters with Peak-Current-Mode Control. 13.3 Relationship between Duty Cycle and Inductor-Current Slopes. 13.4 Instability of Closed-Current Loop. 13.5 Slope Compensation. 13.6 Sample-and-Hold Effect on Current Loop. 13.7 Current Loop in s -Domain. 13.8 Voltage Loop of PWM Converters with Current-Mode Control. 13.9 Feedforward Gains in PWM Converters with Current-Mode Control without Slope Compensation. 13.10 Feedforward Gains in PWM Converters with Current-Mode Control and Slope Compensation. 13.11 Closed-Loop Transfer Functions with Feedforward Gains. 13.12 Slope Compensation by Adding a Ramp to Inductor Current. 13.13 Relationships for Constant-Frequency Current-Mode On-Time Control. 13.14 Summary. 13.15 References. 13.16 Review Questions. 13.17 Problems. 13.18 Appendix: Sample-and-Hold Modeling. 14 Current-Mode Control of Boost Converter. 14.1 Introduction. 14.2 Open-Loop Small-Signal Transfer Functions. 14.3 Open-Loop Step Responses of Inductor Current. 14.5 Closed-Voltage-Loop Transfer Functions. 14.6 Closed-Loop Step Responses. 14.7 Closed-Loop DC Transfer Functions. 14.8 Summary. 14.9 References. 14.10 Review Questions. 14.11 Problems. 15 Silicon and Silicon Carbide Power Diodes. 15.1 Introduction. 15.2 Electronic Power Switches. 15.3 Intrinsic Semiconductors. 15.4 Extrinsic Semiconductors. 15.5 Silicon and Silicon Carbide. 15.6 Physical Structure of Junction Diodes. 15.7 Static I - V Diode Characteristic. 15.8 Breakdown Voltage of Junction Diodes. 15.9 Capacitances of Junction Diodes. 15.10 Reverse Recovery of pn Junction Diodes. 15.11 Schottky Diodes. 15.12 SPICE Model of Diodes. 15.13 Summary. 15.14 References. 15.15 Review Questions. 15.16 Problems. 16 Silicon and Silicon Carbide Power MOSFETs. 16.1 Introduction. 16.2 Physical Structure of Power MOSFETs. 16.3 Principle of Operation of Power MOSFETs. 16.4 Derivation of Power MOSFET Characteristics. 16.5 Power MOSFET Characteristics. 16.6 Mobility of Charge Carriers. 16.7 Short-Channel Effects. 16.8 Aspect Ratio of Power MOSFETs. 16.9 Breakdown Voltage of Power MOSFETs. 16.10 Gate Oxide Breakdown Voltageof Power MOSFETs. 16.11 Resistance of Drift Region. 16.12 Figures-of-Merit. 16.13 On-Resistance of Power MOSFETs. 16.14 Capacitances of Power MOSFETs. 16.15 Switching Waveforms. 16.16 SPICE Model of Power MOSFETs. 16.17 Insulated Gate Bipolar Transistors. 16.18 Heat Sinks. 16.19 Summary. 16.20 References. 16.21 Review Questions. 16.22 Problems. 17 Soft-Switching DC-DC Converters. 17.1 Introduction. 17.2 Zero-Voltage-Switching DC-DC Converters. 17.3 Buck ZVS Quasi-Resonant DC-DC Converter. 17.4 Boost ZVS Quasi-Resonant DC-DC Converter. 17.5 Zero-Current-Switching DC-DC Converters. 17.6 Boost ZCS Quasi-Resonant DC-DC Converter. 17.7 Multiresonant Converters. 17.8 Summary. 17.9 References. 17.10 Review Questions. 17.11 Problems. Appendix A Introduction to SPICE. Appendix B Introduction to MATLAB. Answers to Problems. Index.

Piezoelectric multifrequency energy converter for power harvesting in autonomous microsystems

Abstract: A multifrequency mechanoelectrical piezoelectric converter intended for powering autonomous sensors from background vibrations is presented. The converter is composed of multiple bimorph cantilevers with different natural frequencies, whose rectified outputs are fed to a single storage capacitor. The structure of the converter, description of the operation, and measurement data on the performances are reported. Experimental results show the possibility of using the converter with input vibrations across a wideband frequency spectrum, improving the effectiveness of the overall energy conversion over the case of a single converter. The converter was used to supply power to a battery-less sensor module that intermittently reads the signal from a passive sensor and sends the measurement information via RF transmission, in this way forming an autonomous sensor system with improved measure-and-transmit rate.

Boost Converter With Coupled Inductors and Buck–Boost Type of Active Clamp

Abstract: This paper proposes a boost converter with coupled inductors and a buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate the voltage spike that is induced by the trapped energy in the leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio even under high step-up applications, reducing voltage and current stresses significantly. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching, switching loss can be reduced, and conversion efficiency therefore can be improved significantly. A 200 W prototype of the proposed boost converter was built, from which experiment results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively. It is relatively feasible for low-input-voltage applications, such as fuel cell and battery power conversion.

Design of a Wide Input Range DC–DC Converter With a Robust Power Control Scheme Suitable for Fuel Cell Power Conversion

Abstract: In this paper, an analysis and design of a wide input range dc-dc converter is proposed along with a robust power control scheme. The proposed converter and its control are designed to be compatible with a fuel cell power source, which exhibits 2 : 1 voltage variation as well as a slow transient response. The proposed approach consists of two stages: a three-level boost converter stage cascaded with a current-fed two-inductor boost converter topology, which has a higher voltage gain and provides galvanic isolation from the input source. The function of the front-end boost converter stage is to maintain a constant voltage at the input of the cascaded dc-dc converter to ensure optimal performance characteristics and high efficiency. At the output of the first boost converter, a battery or ultracapacitor energy storage is connected to handle slow transient response of the fuel cell (200 W/min). The robust features of the proposed control system ensure a constant output dc voltage for a variety of load fluctuations, thus limiting the power being delivered by the fuel cell during a load transient. Moreover, the proposed configuration simplifies power management and can interact with the fuel cell controller. Simulation and the experimental results confirm the feasibility of the proposed system.

Long-Lifetime Power Inverter for Photovoltaic AC Modules

Abstract: This paper presents a power inverter tailored for low-power photovoltaic (PV) systems. The inverter features high reliability, thanks to a circuit topology that obviates aluminum electrolytic capacitors from the circuit. Moreover, all components, including logic and control, have been designed to exhibit high reliability at high temperatures. Three conversion stages form the power topology. First, a full bridge connected to a high-frequency transformer and a full-bridge rectifier amplifies the voltage of the PV panel to approximately 475 V. This stage is controlled by using a phase-shift pulsewidth-modulation controller that permits zero-voltage switching, thereby minimizing losses. Second, a buck converter is connected in series with the rectifier and is controlled by using current mode in order to shape the current injection into a rectified sine wave. Last, a full bridge is operated at line frequency to unfold the current injection. The amplification stage has a proportional compensator that maintains the voltage at the PV terminals constant. The current injection stage has a proportional-derivative compensator that controls the amplitude of the grid current so that the dc-link average voltage is maintained constant. Experimental results show that the peak efficiency of the system is 89%, and the total current harmonic distortion is below 5%. Finally, analyses show a designed lifetime of approximately ten years.

A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

Abstract: Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 muH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9 % for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.

A New Design Method for High-Power High-Efficiency Switched-Capacitor DC–DC Converters

Abstract: Switched-capacitor technology is widely used in low power dc-dc converter, especially in power management of the integrated circuit. These circuits have a limitation: high pulse currents will occur at the switching transients, which will reduce the efficiency and cause electromagnetic interference problems. This makes it difficult to use this technology in high-power-level conversion. This paper presents a new design method for dc-dc converter with switched-capacitorldquo technology. The new method can reduce the high pulse current which usually causes serious problem in traditional converters. Therefore, the power level of this new designed converter can be extended to 1 kW or even higher. A 1-kW 42/14-V switched-capacitor converter was designed for 42-V automotive system. The proposed converter has no requirement for magnetic components and can achieve a peak efficiency of 98% and 96 % at full load. The main circuit of the dc-dc converter is analyzed and its control scheme is presented in the paper. The experimental results verified the analysis and demonstrate the advantages.

Master–Slave Current-Sharing Control of a Parallel DC–DC Converter System Over an RF Communication Interface

Abstract: Using analog wireless communication, we demonstrate a master-slave load-sharing control of a parallel dc-dc buck converter system, thereby eliminating the need for physical connection to distribute the control signal among the converter modules. The current reference for the slave modules is provided by the master module using radio-frequency (RF) transmission, thereby ensuring even sharing of the load current. The effect of delay due to RF transmission on system stability and performance is analyzed, and regions of operation for a stable as well as satisfactory performance are determined. We experimentally demonstrate a satisfactory performance of the master-slave converter at 20-kHz switching frequency under steady state as well as transient conditions in the presence of a transmission delay. The proposed control concept, which can potentially attain redundancy that is achievable using a droop method, may lead to more robust and reconfigurable control implementation of distributed converters and power systems. It may also be used as a (fault-tolerant) backup for wire-based control of parallel/distributed converters.

Apparatus, System and Method for Cascaded Power Conversion

Abstract: An apparatus, method, and system are provided for power conversion to supply power to a load such as a plurality of light emitting diodes. An exemplary apparatus comprises: a first power converter stage having a first power switch and a first inductive element; a second power converter stage having a second power switch and a second inductive element; a plurality of sensors; and a controller. The second power converter stage provides an output current to the load. The controller is adapted to use a sensed input voltage to determine a switching period, and is further adapted to turn the first and second power switches into an on-state at a frequency substantially corresponding to the switching period while maintaining a switching duty cycle within a predetermined range.

Proximate Time-Optimal Digital Control for Synchronous Buck DC–DC Converters

Abstract: This paper introduces an approach to near time-optimal control for synchronous buck dc-dc converters. The proposed proximate time-optimal digital (PTOD) controller is a combination of a constant-frequency pulsewidth modulation (PWM) controller employing a linear PID compensator close to a reference point, and a linear or nonlinear switching surface controller (SSC) away from the reference, together with smooth transitions between the two. A hybrid capacitor current estimator enables switching surface evaluation and eliminates the need for current sensing. The SSC, which is implemented as a small Verilog HDL module, can be easily added to an existing digital PWM controller to construct the PTOD controller. In steady state, the controller operates exactly the same as a standard constant-frequency PWM controller with a linear PID compensator. Simulation and experimental results are shown for a 6.5 V-to-1.3 V, 10A synchronous buck converter.

Stability Analysis of the Continuous-Conduction-Mode Buck Converter Via Filippov's Method

Abstract: To study the stability of a nominal cyclic steady state in power electronic converters, it is necessary to obtain a linearization around the periodic orbit. In many past studies, this was achieved by explicitly deriving the Poincare map that describes the evolution of the state from one clock instant to the next and then locally linearizing the map at the fixed point. However, in many converters, the map cannot be derived in closed form, and therefore this approach cannot directly be applied. Alternatively, the orbital stability can be worked out by studying the evolution of perturbations about a nominal periodic orbit, and some studies along this line have also been reported. In this paper, we show that Filippov's method - which has commonly been applied to mechanical switching systems - can be used fruitfully in power electronic circuits to achieve the same end by describing the behavior of the system during the switchings. By combining this and the Floquet theory, it is possible to describe the stability of power electronic converters. We demonstrate the method using the example of a voltage-mode-controlled buck converter operating in continuous conduction mode. We find that the stability of a converter is strongly dependent upon the so-called saltation matrix - the state transition matrix relating the state just after the switching to that just before. We show that the Filippov approach, especially the structure of the saltation matrix, offers some additional insights on issues related to the stability of the orbit, like the recent observation that coupling with spurious signals coming from the environment causes intermittent subharmonic windows. Based on this approach, we also propose a new controller that can significantly extend the parameter range for nominal period-1 operation.

A Systematic Topology Evaluation Methodology for High-Density Three-Phase PWM AC-AC Converters

Abstract: This paper presents a systematic evaluation approach of three-phase pulsewidth-modulated (PWM) AC-AC converter topologies for high-density applications. All major components and subsystems in a converter are considered and the interdependence of all the constraints and design parameters is systematically studied. The key design parameters, including switching frequency, modulation scheme, and passive values, are selected by considering their impacts on loss, harmonics, electromagnetic interference (EMI), control dynamics and stability, and protection. The component selection criteria as well as the physical design procedures are developed from the high-density standpoint. The concept of using the same inductor for harmonic suppression and EMI filtering is introduced in the design. With the proposed methodology, four converter topologies, a back-to-back voltage source converter (BTB-VSC), a nonregenerative three-level boost (Vienna-type) rectifier plus voltage source inverter (NTR-VSI), a back-to-back current source converter (BTB-CSC), and a 12-switch matrix converter, are analyzed and compared for high specific power using SiC devices. The evaluation results show that with the conditions specified in this paper, BTB-VSC and NTR-VSI have considerably lower loss, resulting in higher specific power than BTB-CSC and the matrix converter. The proposed methodology can be applied to other topologies with different comparison metrics and can be a useful tool for high-density topology selection.

Continuous-Time Digital Controller for High-Frequency DC-DC Converters

Abstract: This paper introduces a voltage mode digital controller for low-power high-frequency DC-DC switch-mode power supplies (SMPS) that has fast transient response, approaching physical limitations of a given power stage. In steady state, the controller operates as a conventional pulsewidth modulation regulator and during transients it utilizes a novel fast voltage recovery mechanism, based on real-time processing of the output voltage in digital domain. This continuous-time digital signal processing mechanism is implemented with a very simple processor consisting of a set of asynchronous comparators, delay cells, and combinatorial logic. To eliminate the need for current measurement and calculate the optimal switching sequence of the power stage transistors, the processor performs a capacitor charge balance algorithm, which is based on the detection of the output voltage peak/valley point. The effectiveness of the controller is demonstrated on an experimental 5 W, 5 V to 1.8 V, 400 kHz buck converter. The converter recovers from load transients through a single on-off action of the power switch, virtually reaching the shortest possible time, limited by the values of the power stage filter components only.

An Optimal Control Method for Buck ConvertersUsing a Practical Capacitor ChargeBalance Technique

Abstract: A novel control method is presented in this paper which utilizes the concept of capacitor charge balance to achieve optimal dynamic response for buck converters undergoing a rapid load change. The proposed charge balance method is implemented with analog components and is cheaper and more effective than its digital counterparts since complex arithmetic and sampling delay is eliminated. The proposed controller will consistently cause the buck converter to recover from an arbitrary load transient with the smallest possible voltage deviation in the shortest possible settling time. Since the controller is nonlinear during transient conditions, it is not limited by bandwidth/switching frequency. Unlike conventional linear controllers, the dynamic response (voltage deviation, settling time) of the proposed controller can be estimated using a set of equations. This greatly simplifies the design process of the output filter. Simulation and experimental results show the functionality of the controller and demonstrate the superior dynamic response over that of a conventional linear controller.

High power factor led-based lighting apparatus and methods

Abstract: Power control methods and apparatus in which a switching power supply provides power factor correction and an output voltage to a load via control of a single switch, without requiring any feedback information associated with the load. The single switch may be controlled without monitoring either the output voltage across the load or a current drawn by the load, and/or without regulating either the output voltage across the load or the current drawn by the load. The RMS value of an A.C. input voltage to the switching power supply may be varied via a conventional A.C. dimmer (e.g., using either a voltage amplitude or duty cycle control technique) to in turn control the output voltage. The switching power supply may comprise a flyback converter configuration, a buck converter configuration, or a boost converter configuration, and the load may comprise an LED-based light source.

A Single-Stage AC/DC Converter With High Power Factor, Regulated Bus Voltage, and Output Voltage

Abstract: Unlike existing single-stage AC/DC converters with uncontrolled intermediate bus voltage, a new single-stage AC/DC converter achieving power factor correction (PFC), intermediate bus voltage output regulation, and output voltage regulation is proposed. The converter is formed by integrating a boost PFC converter with a two-switch clamped flyback converter into a single power stage circuit. The current stress of the main power switch is reduced due to separated conduction period of the two source currents flowing through the power switch. A dual-loop current mode controller is proposed to achieve PFC, and ensure independent bus voltage and output voltage regulations. Experimental results on a 24-V/100-W hardware prototype are given to confirm the theoretical analysis and performance of the proposed converter.

Zero-Voltage-Switching DC–DC Converters With Synchronous Rectifiers

Abstract: Active resonant tank (ART) cells are proposed in this paper to achieve zero-voltage-switching (ZVS) and eliminate body-diode conduction in DC-DC converters with synchronous rectifiers (SRs). In low-output-voltage DC-DC converters, SRs are widely utilized to reduce rectifier conduction loss and improve converter efficiency. However, during switches' transition, SRs' parasitic body diodes unavoidably carry load current, which decreases conversion efficiency because voltage drop across body diodes is much higher than that across SRs. Moreover, body diodes' reverse recovery leads to increased switching losses and electromagnetic interference. With the proposed cells of an ART, the body diode conduction of the SR is eliminated during the switching transition from a SR to an active switch, and thus body diode reverse-recovery-related switching and ringing losses are saved. An ART cell consists of a LC resonant tank and an auxiliary switch. A resonant tank cell is charged in a resonant manner and energy is stored in the capacitor of the tank. Prior to a switching transition from a SR to an active switch, the energy stored in the tank capacitor is released and converted to inductor current, which forces the SR current changes direction to avoid conduction of the body diode and related reverse recovery when the SR turns off. Moreover, at the help of energy released from the ART, the active switch's junction capacitance is discharged, which allows the active switch turns on at ZVS. Since energy commutation occurs only during switching transition, conduction loss in the ART cell is limited. Moreover, the auxiliary switch turns off at ZVS and the SR operates at ZVS. The concept of ART cells is generally introduced and detailed analysis is presented based on a synchronous buck converter. Experimental results show the proposed ART cell improves conversion efficiency due to the reduced switching loss, body diodes' conduction, and reverse-recovery losses.

Power supply and controller circuits

Abstract: A power supply system includes multiple power converter phases. A controller (e.g., a processor device) monitors energy delivery for each of multiple power converter phases that supply energy to a load. The controller analyzes the energy delivery associated with each of the multiple power converter phases to identify an imbalance of energy delivered by the multiple power converter phases to the load. Based on the analyzing and detection of an imbalance condition, the controller modifies a future order of activating the multiple power converter phases for powering the load. Accordingly, a single phase of a multiphase switching power converter may be prevented from becoming overloaded while delivering energy to power the load.

A High-Efficiency DC-DC Converter Using 2 nH Integrated Inductors

Abstract: Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.

Ultra Fast Fixed-Frequency Hysteretic Buck Converter With Maximum Charging Current Control and Adaptive Delay Compensation for DVS Applications

Abstract: An integrated DC-DC hysteretic buck converter with ultrafast adaptive output transient response for reference tracking is presented. To achieve the fastest up-tracking speed, the maximum charging current control is introduced to charge up the output voltage with the maximum designed current. For down-tracking, the output is discharged by the load only to save energy. Although the converter works with hysteretic voltage mode control, an adaptive delay compensation scheme is employed to keep the switching frequency constant at 850 kHz to within plusmn2.5% across the whole operation range. The integrated buck converter was fabricated using a 0.35 mum CMOS process. With an input voltage of 3 V, the output voltage can be regulated between 0.5 and 2.5 V. With a load resistor of 10 Omega, the up-tracking speed of the maximum reference step (0.5 to 2.5 V) is 12.5 mus/V. All design features are verified by extensive measurements.

Single-Stage Single-Switch PFC Flyback Converter Using a Synchronous Rectifier

Abstract: A single-stage single-switch power factor correction (PFC) flyback converter with a synchronous rectifier (SR) is proposed for improving power factor and efficiency. Using a variable switching-frequency controller, this converter is continuously operated with a reduced turn-on switching loss at the boundary of the continuous conduction mode and discontinuous conduction mode (DCM). The proposed PFC circuit provides relatively low dc-link voltage in the universal line voltage, and also complies with Standard IEC 61000-3-2 Class D limits. In addition, a new driving circuit as the voltage driven-synchronous rectifier is proposed to achieve high efficiency. In particular, since a driving signal is generated according to the voltage polarity, the SR driving circuit can easily be used in DCM applications. The proposed PFC circuit and SR driving circuit in the flyback converter with the reduced switching loss are analyzed in detail and optimized for high performance. Experimental results for a 19 V/90 W adapter at the variable switching-frequency of 30~70 kHz were obtained to show the performance of the proposed converter.

High-Bandwidth Multisampled Digitally Controlled DC–DC Converters Using Ripple Compensation

Abstract: This paper investigates multi sampled digitally controlled switched-mode power supplies with switching ripple compensation. In digital controllers for power converters, the main bandwidth limitations come from A/D conversion time, computational delays, and small-signal delay of the digital pulsewidth modulator (DPWM). In hard-wired digital-controller technologies, such as in dedicated digital IC and/or in field-programmable gate arrays (FPGAs), the calculation delays can be made negligible with respect to the switching period; thus, when fast ADCs are used, the overall phase lag is dominated by the DPWM. The multi sampling approach can strongly reduce the DPWM delay, thus breaking the bandwidth limitations of conventional single-sampled solutions. In this paper, the additional aliasing effects, which would require a filtering action, are avoided, exploiting the periodic nature of the switching ripple under steady-state conditions using a repetitive-based filtering action. Simulation and experimental results on a 1.2-V-10-A 500-kHz synchronous buck converter, where the digital control has been implemented in the FPGA, confirm the properties of the proposed solution.

Integrated Buck-Flyback Converter as a High-Power-Factor Off-Line Power Supply

Abstract: This paper investigates the integrated buck-flyback converter (IBFC) as a good solution for implementing low-cost high-power-factor ac-dc converters with fast output regulation. It will be shown that, when both buck and flyback semistages are operated in discontinuous conduction mode, the voltage across the bulk capacitor, which is used to store energy at low frequency, is independent of the output power. This makes it possible to maintain the bulk capacitor voltage at a low value within the whole line voltage range. The off-line operating modes of the IBFC are also investigated to demonstrate that the control switch of the proposed converter handles lower root-mean-square currents than those in similar integrated converters. The off-line operation of the IBFC is analyzed to obtain the design characteristics of the bulk capacitor voltage. Finally, the design and experimental results of a universal input 48 V-output 100 W ac-dc converter operating at 100 kHz is presented. Experiments show that the IEC-61000-3-2 input current harmonic limits are well satisfied and efficiency can be as high as 82%.

A Full-Bridge DC–DC Converter WithZero-Voltage-Switching Overthe Entire Conversion Range

Abstract: A new topology of full-bridge dc-dc converter is proposed featuring zero-voltage-switching (ZVS) of active switches over the entire conversion range. In contrast to conventional techniques, the stored energy in the auxiliary inductor of the proposed converter is minimal under full-load condition and it progressively increases as the load current decreases. Therefore, the ZVS operation over the entire conversion range is achieved without significantly increasing full-load conduction loss making the converter particularly suitable in applications where the output is required to be adjustable over a wide range and load resistance is fixed (e.g., an electromagnet power supply). The principle of operation is described and the considerations in the design of converter are discussed. Performance of the proposed converter is verified with experimental results on a 500-W, 100-kHz prototype.

Study and Implementation of a Current-Fed Full-Bridge Boost DC–DC Converter With Zero-Current Switching for High-Voltage Applications

Abstract: This paper presents a comprehensive study of a current-fed full-bridge boost dc-dc converter with zero-current switching (ZCS), based on the constant on-time control for high-voltage applications. The current-fed full-bridge boost converter can achieve ZCS by utilizing the leakage inductance and parasitic capacitance as the resonant tank. In order to achieve ZCS under a wide load range and with various input voltages, the turn-on time of the boost converter is kept constant, and the output voltage is regulated via frequency modulation. The steady-state analysis and the ZCS operation conditions under various load and input-voltage conditions are discussed. Finally, a laboratory prototype converter with a 22-27-V input voltage and 1-kV/1-kW output is implemented to verify the performance. The experimental results show that the converter can achieve high output voltage gains, and the highest efficiency of the converter is 92% at full-load condition with an input voltage of 27 V.

Three-Level Converter Topologies With Switch Breakdown Fault-Tolerance Capability

Abstract: This paper presents some modified topologies of the neutral-point-clamped converter. In all of them, the main change consists of adding a fourth leg, which is based on the flying-capacitor converter structure. The aim of this additional leg is to provide the converter with fault tolerance. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low-frequency voltage oscillations that appear at the neutral point of the standard three-level topology in some operating conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be designed to either achieve optimal output voltage spectra or improve the efficiency of the converter. Simulation and experimental results are presented to show the viability of this approach both under normal operation mode and in the event of faults.

A 120-W Boost Converter Operation Using a High-Voltage GaN-HEMT

Abstract: A boost converter with a 940-V/4.4 A GaN-HEMT as the main switching device was demonstrated to show the possibility of using high-voltage GaN-HEMTs in power electronic applications. The demonstrated circuit achieved an output power of 122 W and a power efficiency of 94.2% under a drain peak voltage as high as 350 V and a switching frequency of 1 MHz. The dual field-plate structure realized high-voltage switching operation with high power efficiency as dynamic on-resistance was suppressed by an increase of the current collapse phenomena.

Novel DC-DC Multilevel Boost Converter

Abstract: This paper proposes a new DC-DC converter. The DC-DC multilevel boost converter, based on one inductor, one switch, 2N-1 diodes and 2N-1 capacitor, for N levels plus the reference (total N+1 levels), is a boost converter able to control and maintain the same voltage in all the Nx output levels, and able to control the input current. This converter is based on the multilevel converters principle, and it is proposed to be used as DC-link in applications where several controlled voltage levels are needed with self balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters. Used to feed a multilevel inverter, the proposed topology achieves a self voltage balancing; experimental results prove the principle of the proposition.

The essence of three-phase AC/AC converter systems

Abstract: In this paper the well-known voltage and current DC-link converter systems, used to implement an AC/AC converter, are initially presented. Using this knowledge and their space vector modulation methods we show their connection to the family of indirect matrix converters and then finally the connection to direct matrix converters. A brief discussion of extended matrix converter circuits is given and a new unidirectional three-level matrix converter topology is proposed. This clearly shows the topological connections of the converter circuits that directly lead to an adaptability of the modulation methods. These allow the reader who is familiar with space vector modulation of voltage and current DC-link converters to simply incorporate and identify new modulation methods. A comparison of the converter concepts, with respect to their fundamental, topology-related characteristics, complexity, control and efficiency, then follows. Furthermore, by taking the example of a converter that covers a typical operation region in the torque-speed plane (incl. holding torque at standstill), the necessary silicon area of the power semiconductors is calculated for a maximum junction temperature. This paper concludes with proposals for subjects of further research in the area of matrix converters.

Self-tuning digital current estimator for low-power switching converters

Abstract: An inductor current estimator suitable for low-power digitally controlled switch-mode power supplies (SMPS) is introduced. The estimation of the average current value over one switching cycle is based on the analog-to-digital conversion of the inductor voltage and consequent adaptive signal filtering. The adaptive filter is used to compensate for variations of the inductance and series equivalent resistance affecting accuracy of the estimation. Based on the response to an intentionally introduced and known current step, the filter tunes its own parameters such that a fast and accurate estimation is obtained. A practical realization of the estimator resulting in a modest increase in digital controller complexity is shown. Besides a simple digital IIR filter and a load step circuit, it only requires a slow analog-to-digital converter for the input voltage measurement. The estimator is tested on a 6.5 V to 1.5 V, 15 W, digitally-controlled buck converter prototype. The results show that between 20% and 100% of the maximum output load the estimator has accuracy better than 10% and one switching cycle response time.