Citation
Maksimovic, Dragan (1989) Synthesis of PWM and quasiresonant DCtoDC power converters. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd02132007105916
Abstract
Synthesis of DCtoDC converter topologies in the two largest families  PWM and QuasiResonant (QR)  is completed in this thesis
In a PWM converter, two linear timeinvariant networks, consisting of only capacitors and inductors, source and load, are switched at constant frequency with duty ratio D. From defining assumptions, several general properties of PWM converter networks are derived. The established general properties interrelate the number of elements, attainable DC conversion ratio M(D), and features such as continuous terminal currents or possible coupling of inductors.
Based on matrix representation of the converter topology, the systematic synthesis procedure for generation of PWM converters with a given number of reactive elements is constructed. A prescribed set of requirements is the input for the procedure. The requirements may include desired DC conversion ratio, continuous terminal currents, possible coupling of inductors and a given number of switches. In particular, the number of switches implemented as transistors can be specified. Outputs of the procedure are complete classes of PWM converters that satisfy the input requirements. A number of useful PWM topologies, which have not been identified before, are uncovered. A comparison of members of the classes is included.
Several extensions of PWM converters are considered, including insertion of the isolation transformer and two discontinuous operating modes for which unified DC analyses are completed.
QuasiResonant converters are defined as twoswitch PWM converter networks to which resonant elements are added. Synthesis of QR, converters is based on the recognition that there are only a finite number of topologically distinct positions for resonant elements within a twoswitch PWM parent converter. If a single resonant inductor and a single resonant capacitor are added to a twoswitch PWM topology, examination of all possible positions yields a total of six QR classes, which come in dual pairs. Two pairs are identified as known QR classes, namely, ZeroCurrent/ZeroVoltage (ZV/ZC) and ZeroCurrent/ZeroVoltage QuasiSquareWave (ZCQSW/ZVQSW). The remaining two classes, named OffResonant and OnResonant QuasiPWM (Q[f]PWM/Q[n]PWM), have not been recognized so far. The names originate from the fact that QPWM converters can be regarded as PWM converters operating in both discontinuous modes simultaneously. The synthesis procedure can be generalized to encompass additional resonant elements. As an example, classes of ZeroCurrent and ZeroVoltage MultiResonant (ZCMR/ZVMR) converters are formally defined.
In contrast to squarewave switch waveforms in PWM converters, all QR topologies exhibit smooth quasisinusoidal waveforms and therefore reduced switching losses. Of particular interest are operating modes in which all switching transitions are at zero current or at zero voltage.
A study of operating modes and a DC analysis unified with respect to all PWM parents and all topological variations are carried out for four selected classes of QR Converters  Q[n]PWM, ZV, ZVQSW, and ZVMR. It is emphasized that for a QR converter, topology alone is not sufficient to derive DC conversion properties. Subject to different switch implementations and control timing, the emerging operating modes can result in vastly different behavior of the same converter topology.
Two switch implementations are considered  conventional, with one controllable switch and one diode, and the one that resembles the technique of synchronous rectification  with two controllable switches. In the first case, with the exception of converters in two QPWM classes, only variablefrequency control is applicable. However, if both switches are controllable, constantfrequency control is restored in all QR classes, and several novel operating modes of practical interest are uncovered.
Various QR classes and operating modes are compared with respect to sets of switching transitions, sensitivity to parasitic elements, available operating region, frequency range and stresses on switching devices. The role of free parameters in various design tradeoffs is exposed, thus allowing a designer to select and realize the topology best suited for a particular application.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Subject Keywords:  converter synthesis; DCDC converter; pulsewidth modulation; PWM; resonant switching; soft switching; switchedmode power 
Degree Grantor:  California Institute of Technology 
Division:  Engineering and Applied Science 
Major Option:  Electrical Engineering 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Thesis Committee: 

Defense Date:  12 January 1989 
Record Number:  CaltechETD:etd02132007105916 
Persistent URL:  http://resolver.caltech.edu/CaltechETD:etd02132007105916 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  626 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  12 Mar 2007 
Last Modified:  26 Dec 2012 02:31 
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