Showing papers on "Buck converter published in 2003"

System and method for reducing external battery capacity requirement for a wireless card

Abstract: A system for providing power to a wireless card includes power interface that provides power to a compact flash card. A boost regulator boosts the power from the power interface. A battery provides power that is summed with the power from the power interface. Moreover, a buck regulator limits the voltage of the summed power. A compact flash card can be powered by the power interface while a wireless card can be powered by the summed power.

Optimized piezoelectric energy harvesting circuit using step-down converter in discontinuous conduction mode

Abstract: An optimized method of harvesting vibrational energy with a piezoelectric element using a step-down DC-DC converter is presented. In this configuration, the converter regulates the power flow from the piezoelectric element to the desired electronic load. Analysis of the converter in discontinuous current conduction mode results in an expression for the duty cycle-power relationship. Using parameters of the mechanical system, the piezoelectric element, and the converter; the "optimal" duty cycle can be determined where the harvested power is maximized for the level of mechanical excitation. It is shown that, as the magnitude of the mechanical excitation increases, the optimal duty cycle becomes essentially constant, greatly simplifying the control of the step-down converter. The expression is validated with experimental data showing that the optimal duty cycle can be accurately determined and maximum energy harvesting attained. A circuit is proposed which implements this relationship, and experimental results show that the converter increases the harvested power by approximately 325%.

Predictive digital current programmed control

Abstract: This paper explores predictive digital current programmed control for valley, peak or average current. The control laws are derived for the three basic converters: buck, boost, and buck-boost. It is found that for each variable of interest (valley, peak or average current) there is a choice of the appropriate pulse-width modulation method to achieve predictive digital current control without oscillation problems. The proposed digital control techniques can be used in a range of power conversion applications, including rectifiers with power factor correction (PFC). Very low current distortion meeting strict avionics requirements (400-800 Hz line frequency) is experimentally demonstrated on a digitally controlled boost PFC employing predictive average current programmed control.

Step-up switching-mode converter with high voltage gain using a switched-capacitor circuit

Abstract: A new circuit is proposed for a steep step-up of the line voltage. It integrates a switched-capacitor (SC) circuit within a boost converter. An SC circuit can achieve any voltage ratio, allowing for a boost of the input voltage to high values. It is unregulated to allow for a very high efficiency. The boost stage has a regulation purpose. It can operate at a relatively low duty cycle, thus avoiding diode-reverse recovery problems. The new circuit is not a cascade interconnection of the two power stages; their operation is integrated. The simplicity and robustness of the solution, the possibility of getting higher voltage ratios than cascading boost converters, without using transformers with all their problems, and the good overall efficiency are the benefits of the proposed converter.

Single-inductor multiple-output switching converters with time-multiplexing control in discontinuous conduction mode

Abstract: An integrated single-inductor dual-output boost converter is presented. This converter adopts time-multiplexing control in providing two independent supply voltages (3.0 and 3.6 V) using only one 1-/spl mu/H off-chip inductor and a single control loop. This converter is analyzed and compared with existing counterparts in the aspects of integration, architecture, control scheme, and system stability. Implementation of the power stage, the controller, and the peripheral functional blocks is discussed. The design was fabricated with a standard 0.5-/spl mu/m CMOS n-well process. At an oscillator frequency of 1 MHz, the power conversion efficiency reaches 88.4% at a total output power of 350 mW. This topology can be extended to have multiple outputs and can be applied to buck, flyback, and other kinds of converters.

Multi-mode renewable power converter system

Abstract: A multi-mode renewable power converter system is disclosed. The system includes a control unit, a boost converter, an inverter and optional bi-directional charger, wherein the boost converter converts DC output of a solar cell or a renewable source to high DC bus voltage, and the inverter converts this DC bus voltage to an AC output. This power converter can be used to support standalone load or grid-connected system with a dynamic maximum power point tracking (MPPT) circuit. The MPPT circuit detects the current and voltage from the solar cell and indicates to the inverter to provide power to the load connected. When the optional bi-directional charger is installed, the MPPT signal is also fed to this charger to make the power efficiency maximized for the system.

An interleaved boost DC-DC converter with large conversion ratio

Abstract: A new PWM dc-dc converter is introduced in which large voltage step-up ratios can be achieved without high duty-cycle, with low voltage and current stress and without transformer. The proposed circuit is an extension of the boost interleaved converter, incorporating a multistage capacitor multiplier. A simple nondissipative snubber can be used reducing the reverse recovery current of the diodes and also obtaining low turn-on and turn-off losses. The modularity of the structure allows the increment of the current, voltage and power levels, using the same range of components and maintaining high efficiency, only increasing the number of series and parallel stages. The paper gives a theoretical analysis, and experimental data on a 400 W example that was built and tested: 24 Vdc input, 200 Vdc output, and 40 kHz switching frequency. The measured performance agreed well with the theoretical predictions and the measured efficiency obtained is equal to 95% at full load.

Simple topologies of PWM AC-AC converters

Abstract: This letter proposes a new family of simple topologies of PWM AC-AC converters with minimal switches. With extension from the basic DC-DC converters, a series of AC-AC converters such as buck, boost, buck-boost, Cuk, and isolated converters are obtained. By PWM duty ratio control, they become a "solid-state transformer" with a continuously variable turns ratio. All the proposed AC-AC converters in this paper employ only two switches. Compared to the existing circuits that use six switches or more, they can reduce cost and improve reliability. The operating principle and control method of the proposed topologies are presented. Analysis and simulation results are given using the Cuk AC-AC converter as an example. The analysis can be easily extended to other converters of the proposed family.

Power converter system

Abstract: A power converter system advantageously employs a modular, bi-directionally symmetrical power converter assembly in a readily customizable configuration to interconnect a direct current power source to a three-phase alternating power grid. Connections external to the power converter assembly are selected to optimize the power converter system for a specific application, such as interconnecting a photovoltaic array to the three-phase electrical power grid. The electrical interconnections of various elements including isolation transformers, voltage sensors, and control switches are optimized to improve efficiency and reliability.

Using reverse blocking IGBTs in power converters for adjustable speed drives

Abstract: A new semiconductor power device that is urgently needed particularly in power converter topologies, the reverse blocking insulated gate bipolar transistor (RB-IGBT), has been realized by adding minor changes to the structure of a standard IGBT to make it capable of withstanding reverse voltage. However, the switching behavior of the device's intrinsic diode during reverse recovery is not as good as a discrete IGBT and series diode implementation. This paper analyzes the use of this device in three power converter topologies that may benefit from it, namely: 1) the matrix converter, 2) the two-stage direct power converter (DPC), and 3) the three-level voltage source rectifier. A commutation method to override the poor reverse-recovery characteristic of the RB-IGBT intrinsic diode in a two-stage DPC is proposed. A loss analysis shows that by using RB-IGBTs the efficiency of the two-stage DPC becomes similar to a two-level voltage source converter.

Methods and circuits for programmable automatic burst mode control using average output current

Abstract: The present invention comprises a user-programmable control circuit for use in a power converter to automatically transition the converter into BURST mode when load current demand is low. The control circuit senses load current demand by monitoring the output current of the converter, and generating a signal representative of the monitored output current. The control circuit may automatically transition the converter into BURST mode when the signal indicative of the average monitored output current decreases below a user-programmable threshold. BURST mode may increase overall converter efficiency by turning OFF a plurality of electronic components, and maintaining the converter's output voltage at a regulated level by energy stored in an output capacitor.

Multiphase coupled-buck converter-a novel high efficient 12 V voltage regulator module

Abstract: The most popular VRM topology-multiphase buck converter operates at a very small duty cycle due to a high input voltage and a low output voltage. The performance of the multiphase buck converter suffers from the very small duty cycle. Alternative topologies with an extended duty cycle are explored in order to improve the efficiency without compromising the transient response. A novel topology named multiphase coupled-buck converter is proposed, which enables the use of a large duty cycle with recovered leakage energy and clamped MOSFET voltage. The input filter is further integrated in the proposed circuit to reduce the number of components. A 12 V-to-1.5 V/50 A VRM prototype demonstrates that the multiphase coupled buck converter can have a much better efficiency than the multiphase buck converter with the same transient response.

Generalized structure of bi-directional switched-capacitor DC/DC converters

Abstract: This paper presents a generalized circuit structure of bi-directional switched-capacitor dc/dc converters that feature voltage step-down, voltage step-up, and bi-directional power flow. The starting point is the derivation of two structures of single-capacitor bi-directional converter cells. Current control scheme is applied in the capacitor-charging phase, resulting in a near-constant capacitor charging current and low electromagnetic interference. A converter string is then formulated by cascading a number of converter cells, in order to meet the input and output voltage requirements and conversion efficiency. By paralleling two similar strings and operating them in the anti phase, the overall converter input current becomes continuous. A reduced-order modeling and state-space averaging technique are used to study the static and dynamic behavior of the converter. The theoretical conversion efficiency in the step-down and step-up mode, respectively, is investigated for different voltage-conversion ratios and numbers of stages. The performance of the proposed structure is experimentally verified on a 5-V/12-V prototype.

Hybrid variable speed generator/uninterruptible power supply power converter

Abstract: The invention in the simplest form is an improved hybrid power converter with uninterruptible power supply (UPS) and power quality capabilities as well as an integrated variable speed power source and control method that is used to generate high quality, uninterruptible AC power utilizing fewer batteries and operating at optimum fuel efficiency and with reduced emissions. The variable speed generator control scheme allows for load adaptive speed control of a power source such as an engine (20) and generator (10). The transformerless hybrid power converter topology and control method provides the necessary output frequency, voltage and/or current waveform regulation, harmonic distortion rejection, and provides for single-phase or unbalanced loading. The transformerless hybrid power converter also provides inline or offline UPS capability, line voltage and/or frequency sag and surge compensation, peak shaving capability, VAR compensation and active harmonic filtering.

Single inductor dual output buck converter with frequency and time varying offset control

Abstract: A single-inductor dual-output buck converter and control method that facilitates power conversion by converting a single DC power source/supply into two separate DC outputs, each of which can be configured to provide a selected/desired voltage by selection of respective duty cycles. The topology of the inverter includes a pair of diodes or switches that can selectively re-circulate inductor current. The converter is generally operated at a fixed frequency with four stages of operation. A first and third stage of operation provide power to a first and second output, respectively. A second and fourth stage of operation re-circulate inductor current and can partially recharge a battery type power source. The power output for each stage (voltage and current) can be selectively obtained by computing and employing appropriate time periods for the stages of operation that correspond to appropriate duty cycles.

Maximum power point tracking of coupled inductor interleaved boost converter supplied PV system

Abstract: A photovoltaic generator exhibits nonlinear voltage-current characteristics and its maximum power point varies with solar radiation. A two-cell interleaved boost converter with coupled inductors is used to match the photovoltaic system to the load and to operate the solar cell array at maximum power point. A maximum power point tracking algorithm is developed using only load voltage information, eliminating the array current detection. The present converter system has the advantages of low ripple content, both on the load and source side, improved efficiency and reduced switch stress, as compared to noncoupled two-cell interleaved converters. As a result, a lower value of array capacitance is sufficient for smoothing the array voltage and current. Analytical expressions for the photovoltaic source and interleaved boost converter, corresponding to maximum power point operation of the SCA, are derived. Experimental results are presented to demonstrate the suitability of this converter system. Few experimental observations are also presented for partial shading conditions. Further, a comparative study of coupled and noncoupled interleaved boost converters for photovoltaic applications is made. These studies reveal that, by introducing coupling among the parallel branch inductors, it is possible to improve steady-state performance while maintaining the dynamic performance of the photovoltaic system.

Analysis of buck converters for on-chip integration with a dual supply voltage microprocessor

Abstract: An analysis of an on-chip buck converter is presented in this paper. A high switching frequency is the key design parameter that simultaneously permits monolithic integration and high efficiency. A model of the parasitic impedances of a buck converter is developed. With this model, a design space is determined that allows integration of active and passive devices on the same die for a target technology. An efficiency of 88.4% at a switching frequency of 477 MHz is demonstrated for a voltage conversion from 1.2-0.9 volts while supplying 9.5 A average current. The area occupied by the buck converter is 12.6 mm/sup 2/ assuming an 80-nm CMOS technology. An estimate of the efficiency is shown to be within 2.4% of simulation at the target design point. Full integration of a high-efficiency buck converter on the same die with a dual-V/sub DD/ microprocessor is demonstrated to be feasible.

Multi-phase buck converter

Abstract: A buck converter for providing an output voltage to a load, including a plurality of output switch arrangements having respective output inductors coupled to an output capacitor, the switch arrangements being controllable to provide phase output currents to the output capacitor; a plurality of phase output arrangements respectively coupled to the output switch arrangements, the phase output arrangements being controllable to set the respective phase output currents supplied by the output switch arrangements; a phase control bus communicatively coupled to each of the phase output arrangements; and a phase control arrangement communicatively coupled to the phase control bus, the phase control arrangement being configured to control the phase output arrangements to set the respective phase output currents so that the output voltage approximates the desired voltage; wherein the phase control arrangement and the phase output arrangements are provided as respective integrated circuits.

Power converter controller having event generator for detection of events and generation of digital error

Abstract: A power converter comprises an event detection module detecting various events of the power converter in real time at the switching frequency of a switch in the power converter according to predetermined criteria. A pulse generator generates control signals for controlling the on-times and off-times of the switch based on the various detected events. The events detected by the event detection module include a detection of a “knee” in the reflected secondary voltage on the auxiliary windings of the transformer in a primary side sensing flyback power converter, and detection of a digital error quantifying the difference between the reference voltage and the reflected secondary voltage on the auxiliary windings of the transformer in time domain.

Programmable multiple output DC-DC isolated power supply

Abstract: A multi-output DC-DC power supply has programmable operating characteristics, such as voltage levels, turn-on and off sequences, mono-phase and multi-phase operation, voltage ramp-up and ramp-offs, tracking and protection mode thresholds and action-if-fault strategies. The power supply has a DC-DC converter having an output coupled to a plurality of buck converters. Each buck converter has an output and a control input where the voltage at the output of the buck converter is determined by a duty cycle of at least one pulse width modulated signal provided at the control input of that buck converter. A programmable device has outputs coupled to the control inputs of the buck converters. The programmable device generates the pulse width modulated signals at its outputs for controlling the buck converters to provide voltages corresponding to voltages programmed in the programmable device. The programmable device is programmable and reprogrammable to control the programmable operating characteristics of the power supply.

Optimization arrangement for direct electrical energy converters

Abstract: An arrangement is provided for supplying electrical energy to a load from a direct electrical energy converter that optimizes converter power generation efficiency. The arrangement for optimizing converter power generation efficiency includes an impedance transformation circuit coupled between the energy converter and load for regulating current delivered by the energy converter so as to maximize power delivered to the load.

AC / DC flyback converter

Abstract: A single-stage input-current-shaping (S2ICS) flyback converter achieves substantially reduced conduction losses in the primary side of the S2ICS flyback converter by connecting a bypass diode between the positive terminal of a full-bridge rectifier and the positive terminal of an energy-storage capacitor. An effective current interleaving between an energy-storage inductor and the bypass diode is thus obtained in the S2ICS flyback converter around the peak of the rectified line voltage, resulting in a significantly reduced input-current ripple and reduced current stress on the switch. Further, by rearranging the rectifiers in the ICS part of the S2ICS flyback converter in such a way that the energy-storage capacitor and the ICS inductor are connected to the ac line voltage through only two rectifiers, one diode forward-voltage drop is eliminated, which results in a substantially reduced conduction loss in the primary-side rectifiers.

PCB integrated inductors for low power DC/DC converter

Abstract: This paper discusses the use of printed circuit board (PCB) integrated inductors for low power DC/DC buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 /spl times/ 10 mm/sup 2/. The magnetic layers consist of electroplated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional magnetic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 /spl mu/H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 /spl times/ 10 mm/sup 2/ and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and compact converter solutions.

Flyback power converter having a constant voltage and a constant current output under primary-side PWM control

Abstract: A primary-side flyback power converter supplies a constant voltage and a constant current output. To generate a well-regulated output voltage under varying load conditions, the power converter includes a PWM controller. The PWM controller generates a PWM signal to control a switching transistor in response to a flyback voltage detected from the first primary winding of the power supply transformer. To reduce power consumption, the flyback energy of the first primary winding is used as a DC power source for the PWM controller. The flyback voltage is sampled following a delay time to reduce interference from the inductance leakage of the transformer. To generate a more accurate DC output voltage, a bias current is pulled from the detection input to form a voltage drop across a detection resistor for compensating for the voltage drop of the output rectifying diode.

Series interleaved boost converter power factor correcting power supply

Abstract: A power factor correcting power supply includes an input stage power converter and an output stage power converter. The input stage power converter includes a plurality of series connected boost switches and a power factor correction controller. The power factor correction controller may direct the operation of the boost switches with series interleave phasing to perform power factor correction and voltage regulation. The boost switches are supplied input voltage and input current from a power source. The input voltage is converted to a DC boost voltage by high frequency series interleaved switching of the boost switches. The DC boost voltage is converted to a DC output voltage by the output stage power converter. The DC output voltage is provided on a DC rail for a load of the power factor correcting power supply.

A three-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems

Abstract: This paper describes a newly developed three-level dc-dc converter with wide-input voltage operations for ship-electric-power-distribution systems. The proposed converter is designed with zero-voltage-switching (ZVS) techniques. The operational principles, design details and performances of the converter are discussed along with soft-switching characteristics through experimental results. Furthermore, design criteria on the dc-dc converter are focused on the minimization of the circulation current between main switches and a transformer under soft switching. The converter has achieved about 95% efficiency over wide 7-kW load conditions.

Analysis of the buck converter for scaling the supply voltage of digital circuits

Abstract: The energy consumption in mobile systems has become a big challenge that limits high performance and autonomy in mobile systems. The dynamic voltage scaling (DVS) is a recent technique that reduces energy consumption varying dynamically the supply voltage of the system accordingly to the clock frequency. The buck topology is a good candidate to supply step variations of the output voltage meeting the DVS requirements. In this paper, it is analyzed which is the fastest output voltage evolution that can provide the Buck topology. The minimum time state transition in the buck converter and its corresponding control law are obtained applying the maximum principle or Pontryagin's principle. Design criteria for the buck topology are derived from this result. The analysis is extended to a multiphase buck converter. The minimum time control law is validated in a prototype. The measurements are in good agreement with the theoretical results.

Comparison of state-of-the-art voltage source converter topologies for medium voltage applications

Abstract: This paper compares a two level voltage source converter (2L-VSC), a three-level neutral point clamped voltage source converter (3L-NPC VSC), a three-level flying capacitor voltage source converter (3L-FLC VSC) and a four-level flying capacitor voltage source converter (4L-FLC VSC) on the basis of state-of-the-art 65 kV, 33 kV and 25 kV IGBTs for a 23 kV medium voltage converter The design of the power semiconductors, the installed switch power, converter losses, the semiconductor loss distribution, modulation strategies and the harmonic spectra are compared in detail

Digital controller design for buck and boost converters using root locus techniques

Abstract: Root locus techniques to design digital controllers for buck and boost converters are discussed in this paper. The small signal models of both converters are first transformed into discrete-time models using the matched pole-zero mapping method. Digital controllers are designed based on the discrete-time model using the root locus method. By selecting the poles, zeros and gain of the digital controllers, the closed-loop poles are placed at desired locations in the z-plane. The digital controllers are then implemented on a TI DSP. The root locus design method is compared with the frequency response design method. Experimental results from the buck converter indicate that the results obtained using the root locus method are comparable to the results obtained using the frequency response method, while results from the boost converter indicate the nonlinear nature of the boost converter small signal model may degrade the performance of the design using the root locus method.