Pulse Width Modulation DC-DC Converter Research Articles

On the Stability of the Pulsewidth-Modulated Ćuk Converter

It has been observed that a stabilizing controller for the state-space-average model of a pulsewidth-modulated (PWM) DC-DC converter does not automatically imply a stabilizing controller for the DC-DC converter itself, especially in the case of the C/spl acute/uk converter. By applying multifrequency averaging as a generalization of the state-space averaging technique, the stationary periodic signals of the C/spl acute/uk converter can be obtained by solving a set of linear equations. Using these equations, we are able to analyze stability aspects of the open-loop and closed-loop PWM C/spl acute/uk converter. Simulations are included in open- and closed-loop situations.

A PWM Plus Phase-Shift Control Bidirectional DC–DC Converter

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.

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

In this paper, an improved active resonant snubber cell that overcomes most of the drawbacks of the normal zero-current transition (ZCT) pulsewidth-modulation (PWM) dc-dc converter is proposed. This snubber cell is especially suitable for an insulated gate bipolar transistor (IGBT) PWM converter at high power and frequency levels. The converter with the proposed snubber cell can operate successfully with soft switching under light-load conditions and at considerably high frequencies. The operation principles, a detailed steady-state analysis, and a snubber design procedure of a ZCT-PWM buck converter implemented with the proposed snubber cell are presented. Theoretical analysis is verified with a prototype of a 5-kW and 50-kHz IGBT-PWM buck converter. Additionally, at 90% output power, the overall efficiency of the proposed soft switching converter increases to about 98% from the value of 91% in the hard-switching case.

Double Two Switch Forward Soft Switching PWM DC-DC Converter.

A novel prototype of a double two-switch forward transformer linked zero-voltage and zero-current mode soft-switching (ZVZCS) pulse width modulation (PWM) DC-DC power converter using IGBTs for high power applications is presented. Based on a conventional two-switch forward transformer linked PWM DC-DC converter topology, this converter circuit configuration doesn't include any complex auxiliary resonant circuit. Combining two identical two-switch forward type DC-DC power conversion circuits with a tapped-inductor type DC smoothing filter into a power DC-DC conversion system makes it possible to achieve soft-switching conditions for the active power switches with aid of lossless snubber capacitors and transformer parasitic inductors. Lowered peak voltage across the power switching devices and their related peak current stresses, no transformer saturation effect, reducing of idle and circulating currents through circuit components are practically attained for this converter. This soft-switching PWM DC-DC power converter has some unique advantages such as better power conversion efficiency, lowered output DC ripple current, high power density, constant frequency PWM control scheme, cost effective and wide soft-switching operation range under load variations and PWM regulation settings for high power utilizations. The basic operating principle of the new soft switching power converter treated here is illustrated with approximate periodic steady-state circuit analysis for each mode equivalent circuit. The practical effectiveness of the proposed soft-switching DC-DC power converter is confirmed by the simulation results and is experimentally evaluated on basis of 500W-100kHz breadboard setup using the fast switching IGBTs.

Double two-switch forward transformer linked soft-switching PWM DC–DC power converter using IGBTs

A double two-switch forward type high-frequency transformer linked zero-voltage and zero-current mode soft-switching (ZVZCS) pulse width modulation (PWM) DC-DC power converter using IGBTs is presented. A new circuit configuration of the isolated type PWM softly switching converter is proposed to reduce idling and circulating currents in the main circuit without using complex additional active auxiliary resonant snubber circuits and power semiconductor devices, and to decrease the peak voltage across power devices, and their peak current stresses. This soft-switching PWM DC-DC power converter has the unique advantages of less power circuit components and power semiconductor devices, high power conversion efficiency, constant frequency duty cycle control scheme, cost-effective and stable soft-switching operating range under wide load variations for high power applications. The basic operating principle of the soft-switching power converter treated here is illustrated using periodic steady-state circuit analysis for each mode equivalent circuit. The effectiveness of the proposed soft-switching DC-DC power converter built and tested as a 500 W-100 kHz breadboard setup using IGBTs is verified and evaluated on the basis of simulation and theoretical circuit analysis.

Small-signal model of PWM converters for discontinuous conduction mode and its application for boost converter

A small-signal circuit model for pulsewidth-modulated DC-DC converters operated in discontinuous conduction mode is presented. The model is composed of controlled current sources, an independent voltage source and resistances. The principle of energy conservation approach is used to take into account parasitic resistances of the transistor and diode and the diode threshold voltage. The proposed model is suitable for small-signal, frequency-domain representation of the converters. This model is used to derive the expressions for a boost converter control-to-output transfer function, input-to-output voltage transfer function, input impedance and the output impedance. Bode plots are also given for these transfer functions. The predicted and experimental results were in excellent agreement.

Alternate forms of the PWM switch model in discontinuous conduction mode [DC-DC converters

A pulsewidth-modulated (PWM) DC-DC converter enters discontinuous conduction mode (DCM) as its inductor current attempts to reverse direction, but cannot do so because of switch implementation, and remains at zero in the last interval of each switching period. Three equivalent three-terminal nonlinear transformers are described as the models for the PWM switch in a DCM converter, each having one of the three terminals serving as the common terminal. Each model facilitates the analysis of those corresponding converters in which the PWM switch terminal corresponds to the common transformer terminal is DC-grounded. Examples are given to demonstrate how the models are used to derive the DCM criteria, and the ideal and nonideal voltage gains for the buck-boost, buck, and boost DC-DC converters. The results predicted by the models agree with those reported and verified in the literature.

Robust average current-mode control of multimodule parallel DC-DC PWM converter systems with improved dynamic response

This paper presents a novel average current-mode control (ACC) strategy for the control of multimodule parallel pulsewidth modulation DC-DC converters, which represents a drastic improvement over conventional ACC. This new method consists of the addition of an auxiliary controller into the control loop, besides the current and voltage regulators. The reference-model-based auxiliary controller improves the robustness of the ACC dynamics in buck-derived distributed power systems, preserving loop gain crossover frequency and stability margins over significant changes of the number of connected modules, the load and the line voltage. Moreover, this control scheme shows much better disturbance rejection properties, i.e., closed-loop output impedance and audiosusceptibility, than conventional ACC. From a control theory point of view robust performance is achieved, preserving stability. A multimodule buck prototype has been experimentally tested with different numbers of modules on stream, line, and load conditions, including discontinuous conduction mode. Measurements of the small-signal frequency response of the converter have been carried out, showing the improvement achieved by the proposed control scheme. The empirical large-signal response of the converter under load steps is also shown in order to validate the concept.

Open-loop peak voltage feedforward control of PWM buck converter

DC and small-signal analyses are given for an open-loop buck pulse-width modulated (PWM) DC-DC converter with peak-voltage-modulation (PVM) feedforward control. A DC model is used to derive the DC input-to-output voltage transfer function taking into account parasitic components, such as the MOSFET on-resistance, diode forward resistance, and diode offset voltage. A small-signal model is used to derive the audio susceptibility and the input impedance. It is shown that ideally the audio susceptibility is zero and the input impedance is frequency independent and negative for the buck converter with PVM feedforward control.

Alternate forms of the PWM switch models

Vorperian's pulsewidth modulation (PWM) switch model consists of a PWM transformer and a nonlinear resistor. The recognition that any of the three transformer terminals can serve as the common terminal leads to two alternate PWM transformer models and the corresponding two alternate PWM switch models. For a given PWM dc-dc converter, one of the three PWM switch models is more natural for graphic-oriented analysis/design, e.g., it allows the idealized converter to be analyzed by inspection. Furthermore, all three PWM transformers may be used to graphically manipulate the converter circuit to a form that can be analyzed by inspection. The alternate forms of the PWM transformers and the PWM switch models are effective as graphic-oriented teaching and learning tools for PWM converters. This is demonstrated using examples based on the boost converter and the Cuk converter.

Multifrequency averaging of DC/DC converters

This paper presents some of the issues involved in applying frequency-selective averaging to modeling the dynamic behavior of pulsewidth-modulated (PWM) DC-DC converters. We use the boost converter as an example to show the details involved in deriving some novel extended averaged models, and we use simulations to highlight the accuracy of the models even when traditional small-ripple conditions are not satisfied.

Zero-voltage transition converter with high efficiency operating at constant switching frequency

A new type of zero-voltage-transition pulsewidth modulation (PWM) dc-dc converter is developed by adding two active switches and three diodes to the structure of a quasiresonant converter. The resonant capacitors are not discrete elements, their role is played by the parasitic capacitances of the MOSFETs. By adjusting the interval between the operation of the active switches, a duty-cycle control is obtained. Soft-switching is ensured for all switches for a wide line range and load range. One of the additional diodes is connected in the input circuit and the energy flow in the resonant stage is transferred from a path defined by the two additional transistors to a path given by the two additional diodes in the resonant tank; as a result, the resonant capacitor voltage is prevented from surpassing the input voltage; it drops to zero before the main switch is turned on. All switches are subjected to voltage and current stresses like those in their PWM classical counterparts, implying small conduction losses. The new converter exhibits a high efficiency and good regulation capability.

Battery charger design for the Columbus MTFF power system

A novel pulsewidth-modulated (PWM) dc-dc converter topology is proposed for the battery charge regulator (BCR) of the Columbus Man-Tended Free-Flyer (MTFF) power system. The system is a regulated bus system. Bus voltage control is implemented at the input of the BCR. The use of a conventional buck topology with PWM conductance control at the input results in a second-order behavior. A study of new PWM dc-dc converter topologies has been made to attain a suitable topology. The proposed converter topology is designed and a breadboard including the control loop has been built and tested. The experimental results show that the converter operates according to the design constraints.

Energy-conservation approach to modeling PWM DC-DC converters

A systematic method is presented for including parasitic resistances and offset voltage sources of power switches in averaged dynamic large-signal, DC, and small-signal circuit models of pulse-width modulated (PWM) converters operating in continuous conduction mode (CCM). This method is based on the principle of energy conservation. The approach takes into account the inductor current ripple. For zero-ripple current, the method gives the same results as the state-space averaging method. Reflection rules are introduced and used to simplify the models. As an example, a modeling procedure for the PWM buck converter is detailed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>