Showing papers on "Buck converter published in 1997"

A bi-directional DC-DC converter topology for low power application

Abstract: This paper presents a bidirectional DC-DC converter for use in low power applications. The proposed topology is based on a half-bridge on the primary and a current-fed push-pull on the secondary side of a high frequency isolation transformer. Achieving bidirectional flow of power using the same power components provides a simple, efficient and galvanically isolated topology that is specially attractive for use in battery charge/discharge circuits in DC UPS. The DC mains (provided by the AC mains), when presented, powers the down stream load converters and the bidirectional converter which essentially operates in the buck mode to charge the battery to a nominal value of 48 V. On failure of the DC mains (derived from the AC mains), the converter operation is comparable to that of a boost and the battery regulates the bus voltage and thereby provides power to the downstream converters. Small signal and steady state analyses are presented for this specific application. The design of a laboratory prototype is included. Experimental results from the prototype, under different operating conditions, validate and evaluate the proposed topology. An efficiency of 86.6% is achieved in the battery charging mode and 90% when the battery provides load power. The converter exhibits good transient response under load variations and switchover from one mode of operation to another.

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.

Optimizing design for low voltage DC-DC converters

Abstract: Emerging portable battery-operated systems demand compact, high efficiency, low-voltage and low-power DC-DC converters to maximize system run-time. A hybrid control strategy is used to achieve high efficiency and to select reasonable passive elements over a wide load range. The purpose of this paper is to study design optimization for LV DC-DC power converters. In the paper, a hybrid-controlled buck converter is used to demonstrate the optimization.

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.

System and method for reducing power losses by gating an active power factor conversion process

Abstract: A power supply includes a power factor correction converter and a controller that disables a power factor correction converter when the power supply is operating in a low power mode, when the power factor correction converter is not needed. The controller of the power factor correction converter performs control operations as directed by a control program executing in a computer or processor in some embodiments. In other embodiments, the control operations are directed by an automatic sequence self-directed by a state machine or other sequencer according to a self-analysis.

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.

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).

Analysis of buck converters used as power factor preregulators

Abstract: Buck-type converters are analyzed for application as power factor preregulators. In particular, the maximum power for which the IEC 10003-2 standards are met is calculated for different conversion ratios and modulation techniques. Two step-down converters are proposed, which comply with EMC standards thanks to an auxiliary flyback stage which uses the same switches of the main converter plus a small power switch commutated at the line frequency. With proper design, the voltage stress of the main switch remains the same as for a conventional buck topology. Simulations and experimental results are reported to validate the theoretical analysis.

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.

Development and testing of prototype models for a high-performance 300 MW self-commutated AC/DC converter

Abstract: A technical project is under way in Japan to develop a high-performance self-commutated power converter for future HVDC transmission and DC interconnection applications. In the first stage of the project, prototype power converter models for a 300 MW self-commutated converter were developed. The models were subjected to factory testing to verify the technology for series connection of a large number of gate turn-off thyristors (GTOs), a gate power supply from the high voltage main circuit and energy regeneration using snubber circuits. Satisfactory results were obtained.

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.

Power-factor correction using Cuk converters in discontinuous-capacitor-voltage mode operation

Abstract: The characteristics of Cuk power converters in discontinuous-capacitor-voltage mode operation are studied. A Cuk power converter in this mode of operation is an inherent power-factor corrector and features soft turn-off switching. Simulation and experimental results are reported to verify the theoretical analysis. In addition, the advantages and disadvantages of power factor correction circuits using Cuk power converters in discontinuous-inductor-current mode operation and Cuk power converters in discontinuous-capacitor-voltage mode operation are discussed.

An integrated controller for a high frequency buck converter

Abstract: This paper reports on the design, fabrication, and test of a controller IC for a buck converter, designed to operate with synchronous rectification in a constant off-time, variable frequency mode This mode is advantageous to support soft-switching over a wide input voltage range Operation up to 5 MHz allows potential use with a microfabricated inductor Considerable attention is paid to the control of deadtimes Specifically, the adaptive deadtime control scheme proposed in our earlier work was successfully implemented and tested

Dual-output dc-dc power supply

Abstract: A multi-output power supply having half-brick dimensions includes a forward converter circuit which receives a DC input voltage and in response to a first control signal generates a first DC output voltage at a first level; and a buck regulator circuit which receives the first DC output voltage from the forward converter circuit. In response to a second control signal, the buck regulator generates a second DC output voltage at a second level.

Identification and control of power converters by means of neural networks

Abstract: This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications.

Universal linear power supply

Abstract: A universal linear power supply capable of automatically supplying a regulated DC current output from a range of AC input In one preferred embodiment, interchangeable modular electrical plugs configured to mate with standard AC supplies releasably connect with the power supply The power supply circuitry comprises a two-winding step-down transformer, a rectifier and a DC/DC step-down buck converter A projection on selected electrical plugs mechanically engages a switch on the power supply, connecting the primary coils of the transformer either in series or in parallel to accommodate 110 VAC or 220 VAC input In another preferred embodiment, the invention comprises an electrical plug for accessing VAC input connected, releasably or permanently, to a power supply comprising a linear transformer, a full-wave rectifier and a DC/DC step-down forward converter which is capable of accommodating the full range of standard AC voltage The interchangeable plugs may further comprise a releasable locking means mechanically connected to the casing and designed to engage the electrical plug to maintain the plug in an operative position

Low cost high efficiency power converter

Abstract: A switch mode power converter achieving high efficiency through zero voltage switching (ZVS) by using an auxiliary switch, a capacitor, an auxiliary winding and an inductor. The technique can be applied to a boost, buck-boost, buck, isolated forward or isolated flyback converter. The auxiliary switch is turned on before the main power switch turns on, and the capacitor provides voltage to energize the inductor and force current to flow into the auxiliary winding. The current is transformed by the main winding and discharges the capacitance across main power switch to zero volts before the main switch turns on. Hence ZVS is obtained and can greatly reduce the switching loss of the main power switch.

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.

Simulation and modeling of a DC-DC converter controlled by an 8-bit microcontroller

Abstract: Traditionally, analog control technologies have been employed to regulate the output voltage of DC-DC converters. The utilization of digital control techniques for this regulation function is currently under consideration. Critical issues in a digital control implementation include analog-to-digital conversion range, resolution and delay, calculation time, and numerical precision. Results from an investigation into the modeling and simulation of DC-DC converters controlled by an 8-bit microcontroller are described in this paper. Many of these critical issues have been modeled using Matlab/sup TM/ and Simulink/sup TM/ from The Mathworks Inc. Simulation results from this model are compared to experimental waveforms obtained from a buck converter controlled by a Microchip PIC16C74 8-bit microcontroller. Experimental results agree well with the simulation model. The buck converter is represented by its state-space averaged model in the simulation.

High power laser diode driver based on power converter technology

Abstract: This paper describes the design of a high speed semiconductor laser diode driver designed for driving 500 mW to 1.5 W diodes at full optical power modulation up to frequencies of 10 MHz. The duty cycle of the modulation may be varied. A switching power-converter based current source allows a higher power delivery efficiency to the diode than in previous designs, allowing for a more modest power supply and dissipation requirements. A dynamic ripple cancellation circuit reduces the power converter output current ripple to less than 1% of full-scale current. The circuit is capable of delivering up to 2.5 A to a laser load, with a 10-90% switching risetime from laser threshold to full on of less than 20 ns.

Secondary bifurcations and high periodic orbits in voltage controlled buck converter

Abstract: Period doubling route to chaos has been shown to occur in the voltage controlled DC/DC buck converter, both experimentally and numerically. A chaotic attractor was found at the end of the sequence, suddenly followed by an increase of its size. In this paper new secondary bifurcations and high periodic phenomena, coexisting with the main sequence are detected and analyzed over the same range of parameters. A(synchronous)-switching and stroboscopic maps, unstable orbits, bifurcation diagrams, invariant manifolds and basins of attraction are outlined. These tools are put together to reveal the dynamical richness of this nonsmooth system.

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.