Showing papers on "Buck–boost converter published in 1997"

Single-phase matrix converter

Abstract: A topology of a single-phase AC/AC direct power converter is presented. The circuit, composed from four ideal power switches, is used as a frequency step-up converter. The equations of the proposed converter are developed, its switching angle pattern is calculated and the dynamic behaviour of the system is simulated. Using a power MOSFET and four Schottky diodes, the basic power switch is assembled and a power converter fed from 50 V (RMS), 50 Hz, supplying a passive R, L load operated at 100 Hz, was constructed. Satisfactory agreement between simulated and laboratory results was observed.

Optimised input filter design and low-loss switching techniques for a practical matrix converter

Abstract: The matrix converter permits frequency conversion in a single-stage process. The perceived disadvantage of the matrix converter is that conduction losses are high. However, semisoft current commutation and optimal sequence switching can be used to minimise commutation losses so that at high switching frequencies the total losses in the matrix converter can be less than those in a conventional rectifier–inverter combination. The viability of the matrix converter depends to a large extent on the size and cost of the input filter components required to meet international power quality standards. In the paper filter designs are examined and guidelines established. Practical tests have been carried out on a 3.5 kW converter to validate computer models. It is concluded that the matrix converter is viable if the right combination of semiconductor switching techniques and input filter design are employed.

A single-switch AC/DC converter with power factor correction

Abstract: A new single-stage, single-switch power factor correction converter with output electrical isolation is proposed in this paper. The topology of this converter is derived by combining a boost circuit and a forward circuit in one power stage. To improve the performance of the AC-DC converter (i.e., good power factor correction, low total harmonic distortion (THD) and low DC bus voltage), two bulk storage capacitors are adopted. Its excellent line regulation capability makes the converter suitable for universal input application. Due to its simplified power stage and control circuit, this converter presents a better efficiency, lower cost and higher reliability. Detailed steady state analysis and design procedure are presented. To verify the performance of the proposed converter, a design example along with P-simulation program with integrated circuit emphasis (PSPICE) simulation and experimental implementation are given. The measured power factor and efficiency are 99% and 87% at low line (i.e. 110 VAC) operation, and 95% and 81% at high line (i.e. 220 VAC) operation, respectively.

Portable power system using DC to DC converter

Abstract: A portable power system for a hand tool employs a high-voltage transmission of power from a battery pack over a cord to a DC to DC converter, which steps the transmission voltage down to rated tool voltage. The system uses a switching transistor to transmit power according to a duty cycle which varies automatically according to tool current draw and voltage. The DC to DC converter employs synchronous rectification with an inductor-capacitor network to transform a duty cycle square wave into DC power. The startup voltage sense feature permits powering up the converter circuitry only when needed. The converter will shut down if no current has been drawn by the tool for a predetermined period of time or if the converter unit is in danger of overheating, as determined by a stored algorithm. The portable power system has safeguards to prevent fouling or shorting in wet environments, is adaptable to left or right handed users, and is physically configurable into a variety of carrying modes.

Feedforward control of DC-DC PWM boost converter

Abstract: A new feedforward control circuit suitable for applications in the dc-dc pulsewidth modulated (PWM) boost converter operated in the continuous conduction mode (CCM) is proposed. Its principle of operation is described, analyzed for steady state, and experimentally verified. The peak value of the sawtooth voltage at the noninverting input of a PWM modulator is held constant and the voltage at the inverting input of the PWM modulator varies in proportion to the converter dc input voltage. As a result, the complement of the on-duty cycle (1-D) is proportional to the dc converter input voltage, yielding the converter output voltage theoretically independent of the converter input voltage. The circuit is very simple and significantly improves line regulation of the output voltage. The measured open-loop line regulation at fixed loads was less than 5% for the converter dc input voltage change by 400%. The load regulation was also good even without a negative feedback loop.

Novel aspects of an application of 'zero'-ripple techniques to basic converter topologies

Abstract: Based on a short summary of the theoretical basics of the zero-ripple current phenomenon a special zero input current ripple boost converter topology as presented in the literature is investigated. It is shown that the complete suppression of the input current ripple of the system is only given in a theoretical extreme case. For a practical realization only such a ripple reduction of the input current of the basic converter structure is obtained as corresponds to a simple low-pass input filter. This is proven by a detailed analysis also for a zero-ripple Cuk and for a zero-ripple SEPIC converter structure. Furthermore, it is shown that the realization of a zero-ripple Cuk or zero-ripple SEPIC converter is not linked to a magnetic coupling of the input and output inductors, but can also be achieved by a simple rearrangement of the elements of the basic converter structures. There one can see that the operating behavior of a zero input current ripple SEPIC converter is equivalent to the operating behavior of a buck-boost converter stage with LC input filter. Finally, the advantages and disadvantages of the different realization approaches of zero-ripple topologies are compared. Also, an outlook towards the planned further treatment of the topic is given.

Interleaved continuous flyback power converter system

Abstract: An interleaved flyback electrical power converter system having a plurality of flyback power converters operated in continuous mode, each converter utilizing a power switch operated under zero voltage switching conditions. The interleaved flyback power converter system is highly efficient and compact, and is suitable for use in high power, high frequency applications.

Analysis of a ripple-free input-current boost converter with discontinuous conduction characteristics

Abstract: Coupled inductor techniques supply a method to reduce the power converter size and weight and achieve ripple-free current. The boost power converter is a very popular topology in industry. However, the input-current ripple hinders efforts to meet electromagnetic interference (EMI) requirements. In particular, the input current becomes discontinuous and pulsating when the conventional boost power converter operates in the discontinuous inductor-current mode. This paper describes a boost power converter which has the same discontinuous properties as the conventional boost power converter. However, the proposed boost topology has continuous or ripple-free input current when it operates with discontinuous inductor-current. The proposed topology is compared with traditional converter topologies, such as the Sepic and Cuk power converters. Simulation results are presented. The prototype is built to demonstrate the theoretical prediction. The proposed boost topology is simple, with straightforward control ~the same as pulse-width modulation (PWM)\.

Multiple output voltages from a cascaded buck converter topology

Abstract: A buck converter in accordance with the present invention provides multiple, well regulated, low voltage outputs. A cascaded buck converter comprises a main buck converter that is coupled to a subordinate buck converter through a cascade transistor in series with the free wheeling diode or transistor. The main buck converter is coupled to the free wheeling diode through the cascade transistor. Additional voltage outputs are possible by placing additional subordinate buck converters in series with the cascade transistor. An isolated forward converter with multiple output voltages in accordance with the present invention may be derived using the cascaded buck converter topology. The cascading configuration permits multiple voltage outputs using a minimum number of switching devices while avoiding undesirable cross regulation.

Anomalous bifurcations in DC-DC converters: borderline collisions in piecewise smooth maps

Abstract: Nonstandard bifurcations have been reported in power electronic DC-DC converters. We show that sampled data models with stroboscopic sampling yield piecewise smooth maps and that most of the observed "anomalous" bifurcations fall into a class called "border collision bifurcations". We offer analytical explanation of the dynamics of three converter topologies (current mode controlled first order buck converter, current mode controlled boost converter, duty cycle controlled buck converter).

Step-up/down DC-to-DC converter

Abstract: A converter for converting a DC voltage not stabilized, such as the terminal voltage of a battery, into a stable DC voltage, comprising a voltage comparison unit (2 in FIG. 1) and an operation changeover control unit (3). The voltage comparison unit (2) compares an input voltage and an output voltage. The operation changeover control unit (3) controls the changeover of the operations of the DC/DC converter (1) so that the DC/DC converter (1) may perform a step-down operation as the operation of a step-down type converter when the input voltage is higher than the output voltage as the result of the comparison, and that it may perform a step-up operation as the operation of a step-up type converter when the output voltage is higher than the input voltage. Thus, losses in the smoothing reactor and smoothing capacitor of the step-up/down converter are suppressed to enhance the efficiency thereof.

Half-bridge zero-voltage-switched PWM flyback DC/DC converter

Abstract: A DC-DC ZVS PWM converter circuit which utilizes the leakage inductance of an output transformer and a three-step operation cycle so as to reduce the voltage stress on the converter power switching transistors and to reduce the EMI noise emissions of the circuit.

High efficiency DC step-up voltage converter

Abstract: A DC power converter is disclosed for converting an input voltage to a final output voltage that is higher than the input voltage. The power converter includes an input terminal for receiving the input voltage and a final output terminal. A boost converter generates an intermediate voltage that is higher than the input voltage and lower than the final output voltage. The boost converter includes an inductor having a primary winding that has a first end connected to the input terminal, a switch for selectively connecting the second end of the first winding to ground, a first diode connected between the second end of the first winding and an intermediate node, and a first output capacitor connected between the intermediate node and ground. The boost converter produces at the first output capacitor an intermediate voltage higher than the input voltage. The step up converter described further includes a second winding on the inductor, a first end of which is connected to receive the intermediate voltage. A diode is connected between the second end of the second winding and the converter output terminal. A second output capacitor is connected between the converter output terminal and ground.

Modeling, analysis, and application of buck converters in discontinuous-input-voltage mode operation

Abstract: By adding a suitable LC filter to the input of a buck power converter, it is possible to force the converter into discontinuous-input-voltage mode operation A buck power converter in this mode of operation has useful properties such as power factor correction and soft turn-off switching The operation, modeling, low-frequency behavior, and application of the power converter are studied Experimental results verifying the theoretical predictions are also presented

Analysis and design of a fixed-frequency LCL-type series-resonant converter with capacitive output filter

Abstract: A fixed-frequency modified (LCL-type) series-resonant converter which uses a capacitive output filter is analysed using the Fourier series approach. Based on the analysis a simple design procedure is given. Detailed SPICE simulation results are presented for the designed converter to evaluate its performance for varying input supply voltage and for load variation. Experimental results obtained from a MOSFET based 500 W, 115 V output converter are presented to verify the analysis. The converter operates in lagging power factor mode for a very wide variation in the load and the supply voltage and is suitable for high voltage output applications.

Power switched-capacitor DC-DC converter: analysis and design

Abstract: This paper shows that a switched-capacitor DC-DC converter (SCDDC) can be designed to process up to several tens of watts of output power at an efficiency exceeding 80%. Converter operation is analyzed by "modified state-space-averaging", (MSSA) which is generally suitable for analysis of converters with nonlinear ripple. A design procedure is presented along with experimental verification.

Control architecture for interleaved converters

Abstract: A control system for an converter circuit using two interleaved boost circuits is described which uses a single PWM controller to control the switches in both of the interleaved boost circuits. A voltage feedback control circuit monitors the output voltage of the converter circuit and sends that information to the PWM controller. A current sensing circuit is provided that senses the current in each of the boost converters. The current sensed in the current sensing circuit is converted to a voltage and used in conjunction with the voltage information from voltage feedback control circuit by the single PWM controller to regulate both of the boost converter switches. By regulating the boost converter switches, the single PWM controller is able to ensure proper synchronization and current sharing while tightly regulating the output voltage and improving the input power factor of the converter circuit.

Re-lift circuit: a new DC-DC step-up (BOOST) converter

Abstract: A re-lift circuit, which is a new DC-DC step-up (boost) converter, is proposed. This converter performs positive to positive DC-DC voltage increasing conversion with high output voltage.

System and method for controlling power factor and power converter employing the same

Abstract: A power factor controller, a method of controlling power factor and a power converter employing either the controller or the method. The controller includes: (1) a ramp circuit that senses an output voltage of a converter being controlled and generates an intermediate waveform that rises as a function of a magnitude of the output voltage and (2) a drive circuit, coupled to the ramp circuit, that senses a current in the converter and causes the intermediate waveform to fall at a time that is a function of a magnitude of the current, the drive circuit generating a drive signal for the converter from the intermediate waveform.

Cascode single-ended to differential converter

Abstract: A cascode single-ended to differential converter has particular applications for use in communication, e.g. RF circuits. The converter provides higher gain, reduced noise figure and improved output level and linearity over the prior art differential pair converter. The present converter is a transconductor, converting an input voltage to a differential current output signal, i.e., two output signals of different currents, with the difference being linear to the level of voltage. The cascode amplifier output signal is used to produce a signal equal in the amplitude but 180 degrees out of phase with the signal produced by the cascode amplifier.

Soft switched PWM AC to DC converter with gate array logic control

Abstract: A soft switched PWM AC to DC power converter for a DC power supply is disclosed. The power supply includes a power factor corrector (PFC) converter with a power boost topology, a DC/DC converter with a forward topology and a fly-back converter which serves as an auxiliary power supply for the controller components. The three converters are synchronized by a gate array logic (GAL) IC to minimize EMI noise. The GAL also conditions the PWM for the PFC and the DC/DC converter to provide very precise switching control. Synchronizing and PWM timing signals are derived by the GAL using a high-speed clock signal that is input to the GAL as a data input. The clock signal is repeatedly divided using synchronous division to yield a digital monostable timing signal that enables very precise control of converter switches.

D/A converter with a Gamma correction circuit

Abstract: A D/A converter with a Gamma correction circuit according to the invention is designed for C-DAC which utilizes multiplexers to obtain reference voltages. This D/A converter takes up much less space and has more simple structure than the conventional R-DAC and 2-divided C-DAC. Therefore, this D/A converter has advantages of simple design and low cost. Furthermore, users can freely define the shape of a Gamma correction conversion curve to thereby widen application areas by adjusting terminal voltages.

System with open-loop DC-DC converter stage

Abstract: Innovative systems and methods for advantageous use of a new isolated power converter topology, in which transformer isolation is provided by a very simple DC-DC converter operated in open-loop mode (with each switch running at a constant duty cycle of approximately 50%, to achieve an effective duty cycle of approximately 100%), and feedback or modulation is instead applied to a preconverter stage which also does power factor corrections. Since the isolation stage is operated at a constant duty cycle, distortion can be minimized and its efficiency can be fully optimized, with a simple circuit and small component count. Unlike a flyback converter, only a very small inductance is required. A simple control architecture is used with current control loop. The disclosed circuit tightly clamps the voltages on the switch and on the transformer, with no ringing nor overshoot.

Power converter stabilization loop

Abstract: The invention provides a stabilized power converter having an input voltage and an output voltage, where the stabilized converter operates similar to a conventional converter under normal conditions, and operates continuously at the maximum power transfer point during overload conditions. The stabilized converter comprises a voltage control loop for regulating output voltage, and a stabilization loop for regulating input voltage. In a preferred embodiment, the stabilization loop senses the input voltage to the stabilized converter and compares it to a reference voltage. Whenever converter input voltage is above the maximum power transfer voltage, no action is taken by the stabilization loop, and the converter operates in the conventional manner. As converter input voltage approaches the maximum power transfer voltage, converter output voltage and corresponding converter input and output power are reduced to compensate.

Current-source resonant converter in power factor correction

Abstract: A 3 kW AC/DC converter is studied to comply the following conditions: power factor correction, output voltage regulation, electrical insulation, high efficiency. In this study we are interested in current-source resonant converter topologies with two energy storage elements and electrical insulation which allow the leakage inductance of a transformer to be included in order to achieve smaller size and lighter weight.

Pulse width modulated DC/DC converters

Abstract: Part I: The fundamentals: Capacitor, inductor, and transformer. Topology_basics of DC/DC converters. Passive filter and frequency content of waveforms. Part II: Forward converter: Steady-state duty cycle equation. Output voltage regulation. Small signal stability analysis. Series-pass regulator. Time-domain studies and filter design. High stress parts and power dissipation. Part III: Flyback converter and boost converters: Flyback converter in discontinuous conduction mode. Boost converter in continuous conduction mode. Part IV: Current-mode and simulation: current-mode control. Simulation of PWM forward converter. Simulation of flyback converter with current-mode control. Appendix. References. Index.

Switched capacitor digital-analog converter with a decreased harmonic distortion

Abstract: In a D/A converter employed in audio systems and various communicating equipment, particularly for using a digital 1-bit data stream as an input and an analog signal as an output, a switched capacitor digital-analog converter having a decreased harmonic distortion utilizes a charge subtraction method in a low-pass filter instead of employing a bypass filter to prevent an operational amplifier from deviating from a linear range due to a switching noise. The bypass capacitor heretofore used in the D/A converter is not employed to shrink the chip designing area.

Analysis of a bi-directional DC-DC converter topology for low power application

Abstract: This paper describes a bidirectional DC-DC converter for use in low power applications. The converter is based on a half-bridge in the primary side and on a current fed push-pull in the secondary of a high frequency isolation transformer. In the presence of the DC mains (provided by the AC mains), the converter essentially operates in the buck mode charging the battery. On failure of DC mains the converter operates in the boost mode and thereby the battery supplies the load power. The simple, low part count, galvanically isolated proposed topology provides an attractive solution for use in battery charge/discharge circuits in a DC UPS. Small signal and steady state analysis of both modes of converter operation is shown. Design guidelines are also presented. The concept is evaluated by an experimental setup and key results are presented.

DC-to-DC converter with soft-start error amplifier and associated method

Abstract: A DC-to-DC converter includes an error amplifier; a ramp generator for generating a ramp signal at the first input of the error amplifier independent of the output of the error amplifier and so that the output of the error amplifier ramps up at a relatively slow rate to avoid overshoot of the desired output voltage of the converter during the start-up phase of the converter; and a ramp disable circuit for disabling the ramp signal upon reaching a value corresponding to the normal operating phase of the converter. The DC-to-DC converter preferably includes at least one power switch and pulse width modulation (PWM) control circuit cooperating with the power switch to provide a desired output voltage of the converter. The ramp generator in one embodiment comprises a current source and an external capacitor connected thereto. In yet another embodiment, the ramp generator may be provided by a staircase ramp generator comprising an amplifier and an integrating capacitor connected thereto. A power-on-reset (POR) circuit is also preferably provided for discharging the integrating capacitor until the start-up phase of the converter.

Resonance type power converter unit, lighting apparatus for illumination using the same and method for control of the converter unit and lighting apparatus

Abstract: A resonance type power converter unit has, in an inverter circuit in which voltage driven type semiconductor devices each having the function not to prevent a backward current are connected in series, the respective voltage driven devices are associated with capacitors which are charged or discharged with currents flowing through the devices and voltage detectors for detecting voltages of the capacitors, and drive circuits for turning on and off the voltage driven devices in accordance with outputs of the voltage detectors. With the resonance type power converter unit, stable resonance operation synchronous with a high-frequency load current can be warranted.