Showing papers on "Buck converter published in 1989"

Instability, subharmonics and chaos in power electronic systems

Abstract: The concept of chaos is applied to a variety of nonlinear power electronic circuits. With the onset of instability, the phenomena of subharmonics, quasi-periodicity, and chaos are predicted and observed. The following examples are dealt with: diodes with charge storage (with application to resonant converters); a ferroresonant circuit; a controlled thyristor rectifier circuit; and a Buck converter controlled by pulse-width modulation (PWM). The examples were chosen to model aspects of real power electronic systems. Analytical and experimental results demonstrate the complex nonlinear phenomena such as subharmonics, quasi-periodicity and chaos can arise in even the simplest systems. >

Modeling current-programmed buck and boost regulators

Abstract: A general small-signal model for current-programmed switching power stages is used for design-oriented analysis of a 150 W buck regulator and a 280 W boost regulator. The model, into which the current-programming minor feedback loop is absorbed, exposes the desired tendency towards 'constant' output current. The regulator voltage loop remains the only explicit feedback loop, allowing the regulator closed-loop properties to be easily obtained from those of the open-loop current-programmed power stage. The design-oriented analytic results allow easy inference of the effects of element changes on the regulator performance functions. Results are obtained for the regulator line-to-output transfer function (audio susceptibility) and output impedance. >

Buck quasi-resonant converter operating at constant frequency: analysis, design and experimentation

Abstract: A buck pulsewidth modulated zero-current switching quasi-resonant converter (buck PWM ZCS QRC) operating at constant frequency is discussed. Operating principle and design-oriented analysis are presented with normalized design curves, design procedure, design example, simulations, and experimental results. The new topology, which can be considered as a particular one, is compared with the well-established buck frequency-modulated zero-current switching quasi-resonant converter (buck FM ZCS QRC) proposed by Fred C. Lee (1988). >

Design of feedback loop in unity power factor AC to DC converter

Abstract: In certain applications it is desirable to convert the utility AC voltage to a DC voltage in such a way as to present a unity power factor load A common means of doing this is a circuit consisting of a bridge rectifier followed by a boost converter Various control schemes for this boost converter are discussed, including their tradeoffs as to power factor, output voltage transient regulation, and cost of implementation A nonlinear regulation-band circuit that has a favorable combination of properties is presented >

New control strategy for matrix converter

Abstract: The authors propose a control strategy for the matrix converter which allows output voltage of 0.866 times the supply voltage to be generated. They discuss how to eliminate voltage and current spikes in the commutation. The system operation is examined and confirmed by experiments using a matrix converter with anti-parallel-connected SITs (static induction thyristors). >

Zero-voltage-switched quasi-resonant buck and flyback converters-experimental results at 10 MHz

Abstract: Experimental results are presented for buck and flyback zero-voltage-switched (ZVS) quasi-resonant converters (QRCs) operating above 5 MHz. A design procedure for a buck ZVS QRC is proposed that minimizes voltage stress to the power MOSFET transistor while maintaining zero voltage switching for specified ranges of input voltage and load resistance. A quasi-resonant gate drive scheme is also proposed and implemented in a buck converter. The drive is simple and provides high switching speed. Power dissipation in the gate drive is substantially reduced due to the quasi-resonant operation. The ZVS QRC technique described is suitable for very-high-frequency operation due to its ability to reduce dynamic turn-on losses, Miller effect, dv/dt, and di//dt and can be applied in distributed onboard power supplies. >

Dual sepic PWM switching-mode DC/DC power converter

Abstract: A steady-state analysis and experimental results for a dual sepic pulse-width-modulated (PWM) DC/DC power converter for both continuous and discontinuous modes of operation are presented. The converter is dual to a sepic converter, but it can also be derived from a forward converter by replacing one of its rectifier diodes with a coupling capacitor. The circuit acts as a step-down or step-up converter, depending on the value of the ON switch duty cycle. The transformerless version of the converter has a positive DC/DC voltage transfer function. Therefore, the circuit is suitable for distributed power systems. Design equations for all circuit components are derived. Experimental results measured at 100 kHz were in good agreement with theoretical predictions. >

Strobed DC-DC converter with current regulation

Abstract: A DC-DC converter regulates the maximum current through an inductor. The DC-DC converter operates within a paging receiver and boosts a voltage from a single cell battery to substantially 3.1 VDC in order to operate circuits which require more voltage than that produced by the single cell battery. Such circuits include CMOS microcomputers and code plug. The DC-DC converter is current regulated thus providing for improved power conversion efficiency. The DC-DC converter is active when the voltage is below a minimum voltage and inactive when above a maximum voltage. The DC-DC converter provides for a wide range of load currents from the converted voltage without being controlled by a microcomputer and while delivering the power to the loads with an improved efficiency.

System for regulating the operating point of a direct current power supply

Abstract: A system for regulating the operating point of a direct current power supply comprising a current generator system connected to a pulse width modulation converter includes a circuit for sampling and measuring the voltage and the current supplied by the current generator. A threshold detector circuit responding to stalling of the converter supplies a logic signal representing the stalled or non-stalled state of the converter relative to threshold values. A regulation loop includes a switching device for inverting the sign of the error signal so that the operating point can be moved towards the maximum power point on the output current-voltage characteristic of the current generator. The system is applicable to regulation of the electrical power supply circuits of spacecraft, space probes, satellites and the like.

Random-switching control in DC-to-DC converters

Abstract: The authors discuss the properties of switching noise in power converters from the viewpoint of the frequency domain. They also discuss the concept of random-switching control, by which the switching-noise spectrum is smoothed and its level is reduced. Two types of control circuits realizing the random switching are introduced for a buck converter, and their basic operations are explained and experimentally examined. Finally, the authors report experimental switching-noise spectra for two kinds of control, namely, random-switching control and conventional PWM (pulse-width-modulated) control. A comparison of these control schemes confirms that random-switching control is effective for suppressing the peak level of the switching-noise spectrum. >

Chaos: a real phenomenon in power electronics

Abstract: An introductory tutorial on chaotic behavior in DC-DC convertors is presented. Chaos is characterized by an emipirical spectrum which has a continuous component, and may even have no discrete components. Chaotic behavior frequently occurs when a power converter operates in a protective mode such as in a short-circuit or overload condition. Chaotic behavior in power converters is described in terms of phase-plane (state-space) trajectories. A description is given of a particular form of buck regulator circuit without PWM (pulse-width modulation) drive and without current sensing, i.e. a form of ripple-regulator. Simulation and experimental data for the circuit are presented and discussed. Two other similar circuits exhibiting chaotic behavior are also considered. >

Cascaded buck converter circuit with reduced power loss

Abstract: Two or more buck converter circuits are cascaded in such a manner that the output of one serves as the input to the next, with the input voltage to each succeeding buck converter stage being reduced in magnitude. The total circuit losses are substantially reduced as compared to the losses generated in a single buck converter having the same input voltage range and the same output voltage and output current. Both positive and negative output terminals may be provided for an output stage.

Pulse width modulation power transmission system

Abstract: A converter for interconnecting two electric networks to transmit electric power from one network to the other, each network being coupled to a respective power generator station. The converter, having an AC side and a DC side, includes a bridge of semiconductor switches with gate turn-off capability coupled to a control system to produce a bridge voltage waveform having a fundamental Fourier component at the frequency of the electric network coupled to the AC side of the converter. The control system includes three inputs for receiving reference signals allowing to control the frequency, the amplitude and the phase angle of the fundamental Fourier component with respect to the alternating voltage of the network coupled to the AC side of the converter. Through appropriate feedback loops, the converter may be used to maintain at a predetermined level the power flowing therethrough or to keep at a preset value the voltage across the DC terminals of the converter and, in both cases, to maintain the frequency synchronism between the fundamental Fourier component and the alternating voltage of the network coupled to the DC side of the converter.

Method and apparatus for controlling a power converter.

Abstract: The invention controls a power converter (34) for interchanging power between first and second electric sources (30, 32). In the preferred embodiment, one of the power sources is a high power DC source (32), such as storage batteries, and the second source is a standard utility bus (30). A static power converter (34) controls power interchanges between the two power sources (30, 32) and a controller responsive to the utility voltage, a command specifying the required power interchange, a feedback responsive to the actual power interchange, a command specifying the reactive power interchange, and a feedback specifying the reactive power interchange to generate signals which control the static converter to assure the required power interchange.

Dual switched mode power converter

Abstract: A dual power converter is introduced which addresses the problem of output ripple and switching losses in a switched power converter. One stage of the power converter is a conventional PWM (pulse-width modulated) converter, and the other stage is a linear source. The linear source controls the voltage directly, and the output current of the linear stage is used to generate the control signal for the switching stage. This scheme is modeled as a two-stage control system, and the overall response is obtained in terms of the individual transfer functions. The PWM converter supplies most of the current, while the linear source supplies the reverse of the ripple current. Two DC-to-DC buck converters have been designed and implemented, giving excellent ripple suppression and high efficiency at very low switching frequencies. >

Three-phase AC-to-AC series resonant power converter with reduced number of switches

Abstract: An apparatus and method is disclosed for an improved AC--AC series-resonant converters incorporating power pulse modulation with internal frequencies of tens of kHz is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and low distortion. The high pulse frequency allows the application of the principle of modulation and demodulation for fast system response. Switches are required which have bidirectional current conduction and voltage blocking ability. The conventional series-resonant AC--AC converter applies a total of 24 anti-parallel thyristors. The circuit configuration of the present invention is a series-resonant AC--AC converter with only 12 thyristors. Use of the converter results in a higher efficiency and lower costs. The alternative power circuit has three neutrals, related to the polyphase source, the load and the converter, which may be interconnected and the high-frequency component of the source and load currents will flow through the connection between the neutrals.

A novel single- to three-phase static converter

Abstract: A comprehensive analysis of a phase converter structure capable of providing three-phase AC power from existing single-phase AC mains by using the principle of cycloconversion is presented. The proposed converter provides balanced three-phase output power and generates a low-distortion input current. However, output voltages contain low-order harmonics which can be easily filtered. The simple control logic circuit and the six-switch converter configuration required make the proposed phase conversion scheme attractive economically as well as practically. Experimental results obtained on a laboratory prototype have been used to prove the validity of respective predicted results. >

Shunt circuit for reducing audible noise at low loading conditions of a power supply employing a high frequency resonant converter

Abstract: A power supply including a resonant converter is provided with current shunt. The current shunt automatically shunts a portion of current flowing in the resonant converter at light loading of the power supply such that output current flowing in an output circuit connected to the power supply would be reduced toward zero as the operating frequency of the converter moves to a predetermined frequency.

Power source for emergency lighting systems

Abstract: A buck/boost converter is driven by a high frequency dc-to-dc flyback converter to provide substantially constant output power, independent of the output voltage, to an inductor to provide current to a load having a v-i characteristic that is suitable for use with a current power source, such as a plurality of parallely-connected LEDs. The flyback converter repetitively generates a battery-simulated output voltage that is current-limited and which may be used to charge a battery as well as to provide power to the buck/boost converter. The buck/boost converter includes a switching circuit for repetitively transferring current to the load and a current sensor circuit operating in conjunction with the switching circuit to change the state of the buck/boost converter to repetitively open the switching means and initiate release of the current to the load.

Sliding-mode controlled Cuk switching regulator with fast response and first-order dynamic characteristic

Abstract: SMC (sliding-mode control) is successfully applied to the Cuk power converter. It results in a high-performance switching regulator with fast response and first-order dynamic characteristic and with an extremely strong ability to suppress the line-voltage and the load-current disturbances of both small and large signals, even with nonpulsating input and output currents. The performance of the SMC Cuk regulator is determined by its feedback gains. Other high-order power stages, such as the augmented boost and augmented buck converters and the buck converter with input filter, could also be handled by SMC to obtain a high-performance, closed-loop system. >

A new computer-aided approach to the analysis of CuK converter by using the alternator equations

Abstract: A novel approach to the computation of the transient and steady-state response of power electronic switching converters is presented. The solution exhibits precision and reflects the continuous character of the converter waveforms. The key to the approach is the extraction of the switching elements (transistors, or transistor and diode, operated as synchronous switches) in a time-varying two-port called an alternator. The remaining part of the converter is linear and time-invariant; it can be described, in the complex frequency domain, by a system of modified nodal equations. The constitutive equations of the alternator are added, providing a global model of the cyclically switching circuit in the s-domain. The converter is analyzed using the Laplace transform. The modified nodal equations of the converter are solved, and the inverse Laplace transform of their solutions is found. The time-domain solutions together with boundary conditions for cyclical operation of the converter are used for the computer-aided calculation of the transient and steady-state response. The method is applied to a coupled-inductor Cuk converter operating in a continuous conduction mode in which the transient state is due to a step-in-line input voltage. >

Synchronous switching power supply comprising buck converter

Abstract: The synchronous switching power supply can be employed in multiple output power supply systems requiring extremely high efficiency and low number of components. The input signal may be AC or pulsating DC. A single switch is switched at zero voltage and current. The short circuit protection is inherent. A switching power supply with buck converter includes a switch for selectively applying the input signal of one polarity to a node, an inductor coupled to the node for attaining a current, a rectifier coupled between the node and ground for conducting the current, a capacitor coupled between the inductor and ground for providing the output signal, a first comparator for comparing the input signal against a first signal, a second comparator for comparing the output signal against a second signal, and a control circuit responsive to the first and second comparators for controlling the switch.

Protection of power converters from voltage spikes

Abstract: In a power converter circuit directly or indirectly connected to the power distribution network, the protection from voltage spikes which may occur on the power supply rail is implemented in a manner as to consent the utilization of at least a portion of the energy associated with the spike by storing portion of said energy in the reactive components of the converter circuit itself instead of dissipating completely the energy through a dissipating elements as in prior art arrangements. The novel circuit arrangement utilizes one or two spike sensors the output signal or signals of which are fed to logic gates which determine a certain configuration of the analog switches of the converter circuit. A protection voltage limiting element (zener diode, avalanche diode, voltage-dependent resistor, etc.) is functionally connected across the analog switch connected between the reactive element of the converter circuit and the power supply rail and limits to its intrinsic breakdown voltage the maximum voltage across the switch.

VSS approach to a full bridge buck converter used for AC sine voltage generation

Abstract: The authors present an application of variable structure systems (VSS) theory, and the associated sliding mode, to a full bridge buck converter used to produce an AC sine voltage. To design a sliding mode controller, the pole assignment method is used. The equivalent control method makes it possible to determine the existence of the sliding regime in the state space. A pulse-width-modulated (PWM) control technique method makes possible AC sine voltage generation. Under high-frequency control switchings, there is an ideal equivalence among sliding mode control and PWM. Experimental results for both of these methods show that under a fixed high switching frequency, the equivalent control corresponding to a sliding motion coincides with the duty ratio of the PWM technique. >

Unified power converter models for continuous and discontinuous conduction mode

Abstract: Computer-aided design of a switching power converter is benefited by the use of a model which runs on SPICE, and which simulates the DC, small-signal AC, and transient response of both the continuous-conduction mode and the discontinuous-conduction mode. This study presents such modes for the three basic types of converters (buck, boost, and buck-boost) in both the duty-cycle-programmed and the current-programmed variety. A set of formulas is presented which describe the small-signal response of current-programmed power converters in the discontinuous-conduction mode. >

Time-averaging equivalent circuit analysis of a resonant switching converter

Abstract: The sophisticated resonant switching converter is investigated by use of a new time-averaging equivalent circuit analysis method presented recently by the authors. The parameters of the time-averaging equivalent circuit model can easily be determined by the new approach without a prior knowledge of the d.c. solution for the converter. The d.c. analysis and a.c, small-signal analysis can then be performed based on the time-averaging equivalent circuit model. Design formulae for the buck resonant converter together with a numerical approximation example are also given.

A novel unipolar converter for switched reluctance motor

Abstract: A configuration of a unipolar power converter with improved switching performance suitable for switched-reluctance motor supply is presented. The switched-reluctance motor operation principle is presented and its ideal characteristics are considered. The proposed converter is described and its operation is analyzed. The converter characteristics are studied with the aid of computer simulation. Current control of the proposed converter is considered. A prototype converter has been built to verify the analysis results and to validate the simulation. The design procedure is presented and experimental results which confirm the analysis are given and discussed. >

Start-up circuit for a high voltage DC to AC converter

Abstract: A four-quadrant buck converter is described having a common leg of an inductor in series with an output capacitor, one power supply for providing a positive voltage output signal and negative voltage output signal to two solid-state switches joined at a common node, an output transformer whose primary is connected across the output capacitor and a pulse width modulator control circuit for operating the switches to produce a predetermined voltage across said output capacitor and for regulating the current out of the transformer. The control circuitry operates in response to a voltage signal from the output of the power supply, a voltage representative of the voltage at the output of the converter, a high frequency ramp voltage, an internal oscillator voltage, a voltage representative of the RMS current flowing on the secondary side of the output transformer, an under-voltage lockout voltage, and a start-up voltage for slowly starting the converter and protecting against overshoot.

State-plane analysis of zero-current-switching resonant DC/DC power converters

Abstract: The state-plane analysis for the buck, boost, buck/boost, and Cuk zero-current-switching resonant DC/DC power converters is presented. Simple visual criteria are introduced to determine whether the converter is operating in a mode producing voltage conversion. It is shown that the voltage conversion takes place within the converters if and only if both horizontal and vertical straight-line segments are present in the state-plane graph. The boundary of energy conversion is identified from the state plane by the evaporation of one or both straight-line segments. Formulas are found for the normalized switching frequency at this boundary that depend on the value of normalized switching voltage. >

Device for utilizing low voltage electric current sources

Abstract: A DC to DC step-up converter is provided which employs high efficiency switching components such as MOSFET switching components in a main converter and provides a low power auxiliary converter to obtain the start up voltage required for operating the low resistance component of the main converter. A control circuit is provided which utilizes either the start up voltage from the auxiliary converter or a feedback voltage from the main converter output to provide control input to the low resistance switching devices which inputs are operative to maintain the output voltage at a desired level.