The thesis investigates the modelling, analysis, design and control of 4th -order LCLC resonant
power converters. Both voltage-output and current-output variants, are considered. Key research
outcomes are the derivation of new frequency- and time-domain models of the converters, based on
normalised component ratios, and including the effects that parasitic elements have on circuit
behaviour, and a detailed account of multi-resonant characteristics; extensions to the use of cyclicmode
modelling methods for application to LCLC converters, to provide rapid steady-state analysis,
thereby facilitating the use of the derived methodologies as part of an interactive design tool; the
formulation of analytical methods to predict the electrical stresses on tank components-an important
consideration when designing resonant converters, as they are often higher than for hard-switched
converter counterparts; the characterisation of both continuous and discontinuous modes of operation
and the boundary conditions that separate them; and a substantial treatment of the modelling, analysis
and design of LCLC converters that can provide multiple regulated outputs by the integrated control of
both excitation frequency and pulse-width-modulation.
The proposed methodologies are employed, for validation purposes, in the realisation of two proof-of concept
demonstrator converters. The first, to satisfy the requirements for delivering 65V (rms) to an
electrode-less, SW, fluorescent lamp, to improve energy efficiency and lifetime, and operating at a
nominal frequency of 2.65 MHz, is used to demonstrate capacitively-coupled operation through the
lamp tube, thereby mitigating the normally detrimental effects of excitation via the electrodes. The
second prototype considers the realization of an LCLC resonant power supply that can provide
multiple regulated outputs without the need for post-regulation circuitry. The two outputs of the
supply are independently, closed-loop regulated, to provide asymmetrical output voltage distributions,
using a combination of frequency- and duty-control. Although, an analysis of the supply shows that
the behaviour is extremely complex, due, in particular, to the highly non-linear interaction between the
mUltiple outputs and parasitic inductances, and rectifier, an analysis to provide optimum performance
characteristics, is proposed. Moreover, a PICIFPGA-based digital controller is developed that allows
control of the transient performance of both outputs under start-up and steady-state conditions.