Showing papers on "Buck–boost converter published in 2004"

Novel high-efficiency step-up converter

Abstract: As a result of the equivalent series resistor of the boost inductor, conventional boost converters are not able to provide high voltage gain. A high-efficiency high step-up converter is proposed, with low voltage stress on power switch, power diodes and output capacitors. The circuit topology of the proposed converter consists of an energy clamp circuit and a voltage boost cell. The boost converter functions as an active clamp circuit to suppress the voltage spike on power switch during the turn-off transient period. The boost converter output terminal and flyback converter output terminal are serially connected to increase the output voltage gain with the coupled inductor. By serially connecting the secondary windings of the boost inductor, a high voltage gain is achieved with less voltage stress on the power devices, such as power MOSFET and power diodes. The operational principle and steady-state analysis are described. A 35 W converter with simulation and experimental results is presented to demonstrate the performance. It shows that the efficiency of the proposed converter is very high (nearly 93%) with four times the voltage output.

A low voltage, dynamic, noninverting, synchronous buck-boost converter for portable applications

Abstract: With the increasing use of low voltage portable devices and growing requirements of functionalities embedded into such devices, efficient power management techniques are needed for longer battery life. Given the highly variable nature of batteries (e.g., 2.7-4.2 V for Li-ion), systems often require supply voltages to be both higher and lower than the battery voltage (e.g., power amplifier for CDMA applications), while supplying significant current, which is most efficiently generated by a noninverting buck-boost switching converter. In this paper, the design and experimental results of a new dynamic, noninverting, synchronous buck-boost converter for low voltage, portable applications is reported. The converter's output voltage is dynamically adjustable (on-the-fly) from 0.4 to 4.0 V, while capable of supplying a maximum load current of 0.65 A from an input supply of 2.4-3.4 V. The worst-case response time of the converter for a 0.4 to 4 V step change in its output voltage (corresponding to a 0.2 to 2 V step at its reference input) is less than 300 /spl mu/sec and to a load-current step of 0 to 0.5 A is within 200 /spl mu/sec, yielding only a transient error of 40 mV in the output voltage. This paper also presents a nonmathematical, intuitive analysis of the time-averaged, small-signal model of a noninverting buck-boost converter.

Buck-boost DC-DC switching power conversion

Abstract: Apparatus operates at a power level within a range of power levels that includes a rated maximum power level of the apparatus. The apparatus includes circuit elements to deliver power at an output voltage to a load from a source at an input voltage using an inductor selectively connected between the source and the load during a power conversion cycle. The inductor conducts a current having an average positive value during the power conversion cycle. A first switching device is interposed between the source and a first terminal of the inductor. A second switching device is interposed between a second terminal of the inductor and the load. A switch controller turns ON the first switching device during a time interval within the power conversion cycle during which the current is negative.

A PWM plus phase-shift control bidirectional DC-DC converter

Abstract: A pulse-width modulation (PWM) plus phase-shift control bidirectional dc-dc converter is proposed. In this converter, PWM control and phase-shift control are combined to reduce current stress and conduction losses, and to expand ZVS range. The operation principle and analysis of the converter are explained, and ZVS condition is derived. A prototype of PWM plus phase-shift bidirectional dc-dc converter is built to verify the analysis.

Low cost fuel cell converter system for residential power generation

Abstract: The high installation cost is the major obstacle of the commercialization of the solid oxide fuel cell for distributed power generation. This paper presents a new low cost 10-kW converter system to overcome this obstacle. The proposed system consists of an isolated dc-dc converter to boost the fuel cell voltage to 400 V dc and a pulse-width modulated inverter with filter to convert the dc voltage to two split-phase 120-V ac. The dc-dc converter uses phase shifting to control power flow through a transformer with a metal oxide semiconductor field effect transistor full bridge on the low voltage side and a voltage doubler on the high voltage side. One IPM is used to realize the voltage doubler and the dc-ac inverter. Compared to the existing fuel cell converter systems, the proposed circuit has low cost, less component count, smaller size, and reduced dc-dc converter peak current. Simulation and experimental results are demonstrated.

Switching power converter and method of controlling output voltage thereof using predictive sensing of magnetic flux

Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.

Analysis and control of a buck DC-DC converter operating with constant power load in sea and undersea vehicles

Abstract: Power-electronics-based zonal direct current (dc) power distribution systems are being considered for sea and undersea vehicles. The stability of the dc power-electronics-based power distribution systems is a significant design consideration because of the potential for negative-impedance-induced instabilities. In this paper, the dynamic properties and control of a buck converter feeding a downstream dc-dc converter are studied. The controller in this system combines an instantaneous current feedback loop using hysteresis with a proportional-integral (PI) algorithm to regulate the output voltage of the converter. Based on a large-signal-averaged model of the converter, the stability-in-large around the operation point is presented. The complete analysis is carried out considering a buck dc-dc converter operating with a constant power load (CPL). Simulations and experimental results are provided to verify the analysis.

Matrix converters

Abstract: This paper deals with the vector-controlled MCT matrix converter induction motor drive with minimized commutation time and enchanced waveform quality. It also deals with the design, construction, and testing of a 10-kVA three-phase to three-phase matrix converter induction motor drive. The converter has been built using discrete 65 A metal-oxide-semiconductor (MOS) controlled thyristors (MCTs). The commutation time has been minimized to avoid any unnecessary waveform distortion, particularly at low demanded output voltages. This minimization gives the matrix converter superior waveform quality in comparison to a conventional inverter and maximizes the available converter output voltage before over modulation is required. The converter is vector controlled and has been tested using a 12-hp induction motor. Full results of these tests are presented.

New two-inductor boost converter with auxiliary transformer

Abstract: A new, two-inductor, two-switch boost converter topology and its variations suitable for applications with a large difference between the input and output voltage are described. The output voltage regulation of the proposed converters is achieved in a wide load and input-voltage range with constant-frequency control by employing an auxiliary transformer that couples the current paths of the two boost inductors.

A new ZVT-ZCT-PWM DC-DC converter

Abstract: In this paper, a new active snubber cell is proposed to contrive a new family of pulse width modulated (PWM) converters. This snubber cell provides zero voltage transition (ZVT) turn on and zero current transition (ZCT) turn off together for the main switch of a converter. Also, the snubber cell is implemented by using only one quasi resonant circuit without an important increase in the cost and complexity of the converter. New ZVT-ZCT-PWM converter equipped with the proposed snubber cell provides most the desirable features of both ZVT and ZCT converters presented previously, and overcomes most the drawbacks of these converters. Subsequently, the new converter can operate with soft switching successfully at very wide line and load ranges and at considerably high frequencies. Moreover, all semiconductor devices operate under soft switching, the main devices do not have any additional voltage and current stresses, and the stresses on the auxiliary devices are at low levels. Also, the new converter has a simple structure, low cost and ease of control. In this study, a detailed steady state analysis of the new converter is presented, and this theoretical analysis is verified exactly by a prototype of a 1-kW and 100-kHz boost converter.

Three level LLC series resonant DC/DC converter

Abstract: Paper presents a three level soft switching LLC series resonant DC/DC converter. ZVS is achieved for each main switch without any auxiliary circuit. Voltage stress of each main switch is half of input voltage. ZCS is achieved for rectifier diodes. Wide input/output range can be achieved under low frequency range because of two-stage resonance. Only one magnetic component is needed in this converter. Efficiency is higher in high line input, so this converter is fit for power products with hold up time requirement. The principle of operation and the characteristics of the new converter are analyzed and verified on a 500 V/spl sim/700 V input 54 V/10 A output experimental prototype, whose efficiency is 94.1% at rating condition.

A high efficiency, noninverting, buck-boost DC-DC converter

Abstract: Portable electronics applications often require a system voltage that is within the range of fully-charged to semidischarged batteries, for example 3.3 V output from a 2.8 V to 4.2 V lithium-ion battery input. The optimal solution to this requirement is a high-efficiency, noninverting buck-boost, DC-DC converter, providing a programmable constant output voltage, typically from single cell Li-ion, multicell NiMH, or alkaline power sources. This solution uses a control scheme which provides automatic and smooth transition through boost, buck-boost and buck modes.

Dc-dc converter with reduced electromagnetic interference

Abstract: A DC-DC converter includes a variable frequency oscillator (36), a control system and a power train. The DC-DC converter is well suited for use in a cell phone. The control system uses the output of the oscillator to control the power train. The oscillator varies its frequency as a function of a pseudo random number generator (60), thereby reducing electromagnetic interference caused by ripple in the output of the DC-DC converter.

A circuit for maintaining hold-up time while reducing bulk capacitor size and improving efficiency in a power supply

Abstract: A circuit that utilizes most of the energy stored in the bulk capacitor of an AC to DC or DC to DC converter power supply by providing an intermediate converter between a first stage boost converter and a DC-DC converter. When the bulk voltage starts to fall during the hold-up time, the intermediate converter boosts the falling voltage to maintain the regulated DC input to the DC to DC converter while reducing the operating range and increasing the operating duty cycle, so as to increase efficiency, reduce peak current and voltage stresses, reduce the size of output filter components and reduce the size of the bulk capacitance by up to half.

Low-voltage-swing monolithic dc-dc conversion

Abstract: A low-voltage-swing MOSFET gate drive technique is proposed in this paper for enhancing the efficiency characteristics of high-frequency-switching dc-dc converters. The parasitic power dissipation of a dc-dc converter is reduced by lowering the voltage swing of the power transistor gate drivers. A comprehensive circuit model of the parasitic impedances of a monolithic buck converter is presented. Closed-form expressions for the total power dissipation of a low-swing buck converter are proposed. The effect of reducing the MOSFET gate voltage swings is explored with the proposed circuit model. A range of design parameters is evaluated, permitting the development of a design space for full integration of active and passive devices of a low-swing buck converter on the same die, for a target CMOS technology. The optimum gate voltage swing of a power MOSFET that maximizes efficiency is lower than a standard full voltage swing. An efficiency of 88% at a switching frequency of 102 MHz is achieved for a voltage conversion from 1.8 to 0.9 V with a low-swing dc-dc converter based on a 0.18-/spl mu/m CMOS technology. The power dissipation of a low-swing dc-dc converter is reduced by 27.9% as compared to a standard full-swing dc-dc converter.

A novel single-stage full-bridge buck-boost inverter

Abstract: A novel single-stage full-bridge series-resonant buck-boost inverter (FB-SRBBI) is proposed in this paper. The proposed inverter only includes a full-bridge topology and a LC resonant tank without auxiliary switches. The output voltage of the proposed inverter can be larger or lower than the dc input voltage, depending on the instantaneous duty-cycle. This property is not found in the classical voltage source inverter, which produces an ac output instantaneous voltage always lower than the dc input voltage. The proposed inverter circuit topology provides the main switch for turn-on at ZCS by a resonant tank. The nonlinear control strategy is designed against the input dc perturbation and achieves well dynamic regulation. An average approach is employed to analyze the system. A design example of 500 W dc/ac inverter is examined to assess the inverter performance and it provides high power efficiency above 90% under the rated power.

Buck or boost tracking power converter

Abstract: A cascade of buck and boost converter is presented here. The control operates in a manner that the converter is either in buck or boost (BOB) mode on a cycle by cycle basis. It transitions between the modes seamlessly to provide a tracking power conversion function for modulating the power supply of a variable envelope radio frequency (RF) power amplifier. The control algorithm and its implementation using switched capacitor circuits is described. Simulation and measured experimental results including converter efficiency, tracking accuracy, and spectrum at the output of the RF power amplifier are provided. This control technique allows seamless transition between the buck and boost modes while tracking RF envelopes with bandwidth greater than 100 kHz, and maintaining extreme accuracy and extremely low ripple. The efficiency of this converter operating at 1.68 MHz is close to 90% over a wide range of conversion ratios. The area of the power converter is extremely small allowing this to be integrated into a cellular telephone. The controller was integrated as part of a larger power management IC as well as a discrete IC.

Modeling of a new ZVS bi-directional dc-dc converter

Abstract: A dual half-bridge (DHB) bidirectional dc-dc converter is a new proposed topology that has the advantages of decreased number of devices, soft-switching implementation, low cost, and high efficiency. Typical applications of this converter are the auxiliary power supply in fuel cell vehicles and battery charging and discharging systems where the power density, cost, weight, and reliability are critical factors. A switching-frequency-dependent state-space averaged model of the converter is developed here for either direction of power flow. This averaged model can be used to derive the steady-state characteristics and small signal dynamics of the proposed topology. It also provides a fast simulation tool to investigate the transient response of the converter. The simulated waveforms of the mathematical model are compared with the detailed circuit simulation to verify the accuracy of the modeling.

Analysis and design of phase shift full bridge converter with series-connected two transformers

Abstract: A new phase shift full bridge (PSFB) converter with series-connected two transformers is proposed. The proposed converter shows wide zero voltage switching (ZVS) ranges and no output inductor is needed since each transformer individually acts as an inductor or a transformer during different times of the switching cycle. The operational principle, large signal modeling, and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a significant improvement in the efficiency for a 100W (5 V, 20 A) telecommunication on-board power supply.

Sliding-mode control design of a boost-buck switching converter for AC signal generation

Abstract: This paper presents a sliding-mode control design of a boost-buck switching converter for a voltage step-up dc-ac conversion without the use of any transformer. This approach combines the step-up/step-down conversion ratio capability of the converter with the robustness properties of sliding-mode control. The proposed control strategy is based on the design of two sliding-control laws, one ensuring the control of a full-bridge buck converter for proper dc-ac conversion, and the other one the control a boost converter for guaranteeing a global dc-to-ac voltage step-up ratio. A set of design criteria and a complete design procedure of the sliding-control laws are derived from small-signal analysis and large-signal considerations. The experimental results presented in the paper evidence both the achievement of step-up dc-ac conversion with good accuracy and robustness in front of input voltage and load perturbations, thus validating the proposed approach.

A soft-switching active-clamp scheme for isolated full-bridge boost converter

Abstract: In this paper, the isolated full-bridge boost converter with active clamp is described and a new active-clamping algorithm to improve the efficiency is suggested. In the proposed method, the resonance between the clamp capacitor and the leakage inductor is utilized to reduce switching losses. The loss analysis is performed by simulation and the improved performance is confirmed by experimental results.

An Improved PSFB PWM DC–DC Converter for High-Power and Frequency Applications

Abstract: In the phase shifted full bridge (PSFB) pulse width modulation (PWM) converter, external snubber capacitors are connected in parallel to insulated gate bipolar transistors (IGBTs) in order to decrease turn-off losses. The zero voltage transition (ZVT) condition is not provided at light loads, thus the parallel capacitors discharge through IGBTs at turn on which causes switching losses and failure risk of the IGBTs. Capacitor discharge through IGBT restricts the use of high-value snubber capacitors, and turn-off loss of the IGBT increases at high currents. This problematic condition occurs especially at the lagging leg. In this study, a new technique enabling the use of high-value snubber capacitors with the lagging leg of the PSFB PWM converter is proposed. As advantages of the proposed technique, high-capacitive discharge current through IGBT is prevented at light loads, the turn-off switching losses of the IGBTs are decreased, and the performance of the converter is improved at high currents. The proposed PSFB PWM converter includes an auxiliary circuit, and it has a simple structure, low cost, and ease of control as well. The operation principle and detailed design procedure of the converter are presented. The theoretical analysis is verified exactly by a prototype of 75 kHz and 10 kW converter.

Control and implementation of a new modular matrix converter

Abstract: Implementation of a new modular AC-AC matrix converter and its control system are described. The converter consists of a matrix connection of capacitor-clamped H-bridge switch cells. The AC output of each switch cell can assume three voltage levels during conduction. Input and output three-phase AC waveforms are synthesized from pulse-width modulation of the DC clamp capacitor voltages. The space-vector modulation approach can be adapted to control this converter. A control algorithm is described that can be reduced to an equivalent DC-link converter. This controller is implemented using programmable logic devices and a flash-memory look-up table. Operational waveforms are presented.

A ZCS bidirectional flyback DC/DC converter

Abstract: This paper addresses the design and analysis of a zero-current-switched (ZCS) bidirectional flyback dc/dc converter. The converter is based on extending a previously developed unidirectional ZCS flyback converter and replacing the output diode with a controlled switch, which acts as either a rectifier or a power control switch in the corresponding power flow direction. By adding an auxiliary winding in the coupled inductor, a switch, and a capacitor, the hard-switching design is converted into a soft-switching one. The technique utilizes the leakage inductance of the flyback coupled inductor to create zero-current-switching conditions for all switches in both power flow directions, leading to reduced switching losses, stresses, and electromagnetic interference. The operating principles of the converter and experimental results have been presented.

Transformerless dc–dc converters with a very high dc line-to-load voltage ratio

Abstract: By splitting the output capacitor of a basic boost converter, and combining the resulting capacitors with the main switch in the form of a switched-capacitor circuit, a new step-up structure is realized. Without using a transformer, a high line-to-load DC voltage ratio is obtained. An output filter is added, as usual, in boost converters for getting a free-ripple output. The circuit compares favorably with a quadratic boost converter regarding the count of devices and efficiency, even if it presents a lower DC gain. A DC analysis of the novel converter is presented. Experimental and simulation results confirm the theoretical expectations. By increasing the number of capacitors in the switched-capacitor circuit, higher gains can be obtained. Versatility, high voltage gain and good transient response are the features of the proposed converter.

Method for operating a frequency converter of a generator and wind energy turbine having a generator operated according to the method

Abstract: The method for operating a frequency converter (26) of a generator (14) in particular of a wind energy turbine (10), in the event of a substantial grid voltage drop, wherein the frequency converter (26) comprises a generator-side power converter (32), to be connected to the generator (14), a grid-side power converter (28) to be connected to the voltage grid (18), and a DC link circuit (30) for connecting the generator-side power converter (32) to the grid-side power converter (28), comprises the step of generating the amount of reactive current to be supplied to the grid (18) by controlling the frequency converter (26).

An active clamping current-fed half-bridge converter for fuel-cell generation systems

Abstract: In this paper, a new active clamping current-fed half-bridge converter has been proposed, which is suitable for fuel cell based power generation systems. The proposed converter has outstanding advantages over the conventional dc-dc converters with respect to high efficiency, high power density, and high component utilization. In special, the proposed converter has predominant high boosting output voltage and high efficiency characteristics under the inherently severe low output voltage of the fuel cell through the overall load conditions. Moreover, the developed converter has been experimentally tested with the help of a fuel cell simulator, which is developed by Sungkyunkwan Univ. and can generate the V-I characteristics of polymer electrolyte membrane fuel cell (PEMFC), so that the performance of the proposed converter could be effectively examined and the validity of the converter could be verified.

DC-DC converter having magnetic feedback

Abstract: A DC-DC converter suitable for multiple converter circuit topologies is disclosed. The DC-DC converter utilizes magnetic feedback of the output load current to provide broad inductance control of a magnetic element, while inhibiting saturation of the switched winding or windings of the magnetic element.

Pulse Train control technique for flyback converter

Abstract: Pulse Train/spl trade/ control technique is introduced and applied to flyback converter operating in discontinuous conduction mode (DCM). In contrast to the conventional pulse width modulation (PWM) control scheme, the principal idea of Pulse Train is to achieve output voltage regulation using high and low power pulses. The proposed technique is applicable to any converter operating in DCM. However, this work mainly focuses on flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

Power converter circuits

Abstract: This text reveals all key components of rectification, inversion, cycloconversion, and conversion circuits. It authoritatively describes switching, voltage and current relationships, and converter properties, operation, control, and performance as utilized in most practical applications. Authored jointly by a veteran scholar and an accomplished res