D.Ing. / This study describes the technology of the Nonlinear Resonant Pole Converter. The NLRP is a soft switching topology that has different advantages.over other power electronic converters. This study describes the evolution, analysis, application and design of the NLRP. An introduction and background section with operating principles are provided. Detail analysis with operational limits is given ...

The Light-emitting diodes (LEDs) are rapidly emerging as the dominant light source given their high luminous efficacy, long lift span, and thanks to the newly enacted efficiency standards in favor of the more environmentally-friendly LED technology. The LED lighting market is expected to reach USD 105.66 billion by 2025. As such, the lighting industry requires LED drivers, which essentially are power converters, with high efficiency, wide input/output range, low cost, small form factor, and great performance in power factor, and luminance flicker. These requirements raise new challenges beyond the traditional power converter topologies. On the other hand, the development and improvement of new device technologies such as printed thin-film capacitors and integrated high voltage/power devices opens up many new opportunities for mitigating such challenges using innovative circuit design techniques and solutions. Almost all electric products needs certain power delivery, regulation or conversion circuits to meet the optimized operation conditions. Designing a high performance power converter is a real challenge given the market’s increasing requirements on energy efficiency, size, cost, form factor, EMI performance, human health impact, and so on. The design of a LED driver system covers from high voltage AC/DC and DC/DC power converters, to high frequency low voltage digital controllers, to power factor correction (PFC) and EMI filtering techniques, and to safety solutions such as galvanic isolation. In this thesis, we study design challenges and present corresponding solutions to realize highly integrated and high performance LED drivers combining switched-capacitor and resonant converters, applying re-configurable multi-level circuit topology, utilizing sigma delta modulation, and exploring capacitive galvanic isolation. A hybrid switched-capacitor-resonant (HSCR) LED driver based on a stackable switched-capacitor (SC) converter IC rated for 15 to 20 W applications. Bulky transformers have been replaced with a SC ladder to perform high-efficiency voltage step-down conversion; an L-C resonant output network provides almost lossless current regulation and demonstrates the potential of capacitive galvanic isolation. The integrated SC modules can be stacked in the voltage domain to handle a large range of input voltage ranges that largely exceed the voltage limitation of the medium-voltage-rated 120 V silicon technology. The LED driver demonstrates > 91% efficiency over a rectified input DC voltage range from 160 VDC to 180 VDC with two stacked ICs; using a stack of four ICs > 89.6% efficiency is demonstrated over an input range from 320 VDC to 360 VDC . The LED driver can dim its output power to around 10% of the rated power while maintaining >70% efficiency with a PWM controlled clock gating circuit. Next, the design of AC main rectifier and inverter front end with sigma delta modulation is described. The proposed circuits features a pair of sigma delta controlled multilevel converters. The first is a multilevel rectifier responsible for PFC and dimming. The second is a bidirectional multilevel inverter used to cancel AC power ripple from the DC bus. The system also contains an output stage that powers the LEDs with DC and provides for galvanic isolation. Its functional performance indicates that integrated multilevel converters are a viable topology for lighting and other similar applications.

The problems associated with IGT/COMFET devices in PWM converters, such as turn off current tailing and latching are largely avoided in a resonant converter. Dynamic saturation loss is identified as the predominant power loss in IGT/COMFET devices for very high frequency resonant operation. Device design change is suggested for very high frequency resonant operation applications. / M.S.

This work presents the modeling and analyses of multiple-output forward converters with weighted voltage control. Based upon the analyses, the systematic design methodologies and design tools are provided. A power stage de model including all the major parasitics, which are detrimental to the output voltages, is derived. A nonlinear programming based design tool is developed to search for the weighting factors. Five methods of stacking secondaries to improve cross-regulation are presented, and the improvement of cross-regulation is quantified. A small-signal model of the multiple-output converters with coupled output filter inductors and weighted voltage control is established. The small-signal characteristics are studied, and the model shows that the system behavior is very sensitive to the coupling coefficient, which has been reported, but never been quantified. The pole-zero interlaced condition is derived. A current-mode control small-signal model is also presented, which can predict all the observed phenomena of current-mode control. Compensator design is discussed for different types of power stage transfer functions for both voltage-mode and current-mode control. / Ph. D.

This dissertation addresses several key issues related to high-frequency soft-switching PWM three-phase power converters. These are: 1. Analysis, synthesis, and design of three-phase soft-switching PWM power converter topologies 2. Design of input EMI filters for three-phase converters 3. Design of microprocessor controllers for three-phase converters. An analysis of existing soft-switching PWM techniques is performed, and two generalized soft-switching PWM converter circuit representations are derived. Based on these representations and common topological properties of three-phase and dc-dc PWM converters, two new procedures for synthesis of three-phase soft-switching PWM converters are derived. The two procedures are used to synthesize five new three-phase soft-switching PWM converter topologies suitable for wide range of applications. A digital signal processor-based controller implementation example is presented. It demonstrates the feasibility of producing versatile, high performance, reliable, low-cost digital controllers for soft-switching PWM three-phase power converters operating at high switching frequencies. A new approach to the design of input filters for ac power electronic circuits is presented here. This approach is based on the application of a vast body of knowledge about passive L-C filters that has existed for many years, but has not been used in power electronics. New passive and active filter pole damping schemes are applied to high-order elliptic filters, resulting in significant filter size reduction compared to the standard filter designs. / Ph. D.

A software program was developed to facilitate the design and analysis of a series resonant converter. Using the program, the values of the inductor and capacitor of the resonant tank can be easily determined to meet design specifications. Following the design, a dc analysis is performed to determine such salient parameters as peak inductor current and peak capacitor voltage. The program is user-friendly with graphic capabilities and is written for the IBM-PC. / Master of Science

The specific circuit effects in the phase-shifted, zero-voltage switched, pulse width modulated (PS-ZVS-PWM) converter and their impact on the converter dynamics are analyzed. The small-signal model is derived incorporating the effects of phase-shift control and the utilization of transformer leakage inductance and power FETs junction capacitances to achieve zero-voltage resonant switching. The thesis explains the differences in the dynamic characteristics of the PS-ZVS-PWM converter and its PWM counterpart. Model predictions are confirmed by experimental measurements. / Master of Science

Two issues pertinent to magamp post regulator are treated in this thesis. One of the issues considered is the operation of a magamp under extreme loading conditions. Practical design equations are derived to allow magamp operation under extreme load conditions such as shutdown of output, foldback of output current and very light load (discontinuous operation). The other issue considered concerns with magamp post regulation for a quasi-resonant converter. A magamp circuit is proposed, designed and tested for a zero current switching quasi-resonant forward converter. It demonstrates that output regulation in a quasi-resonant converter can be achieved with a fixed switching frequency operation. It also demonstrates the feasibility of multiple regulated output application of a quasi-resonant converter. / Master of Science

The performance of the clamped-mode series resonant converter operating at a fixed frequency is studied for off line applications. A new set of characteristics for the converter operating above and below resonant frequency has been developed by including the effect of losses in the analysis. Based on the analytical results, design guidelines are established and two prototypes were built to operate below and above resonant frequency respectively. The advantages and limitations of the two breadboards are assessed and their major sources of loss identified. / Master of Science

State-plane technique was adopted for analysis of a class of resonant de to de power converters. A comprehensive method was developed to understand the complex operation of a resonant converter, identify its operating modes along with their regions of occurrence and determine the de characteristics of the converter in each mode. The method was shown by application to a series resonant converter (SRC), a parallel resonant converter (PRC) and the family of quasi resonant converters (QRCs). Several major conclusions were experimentally verified. By suitably modifying the method, the effect of parasitic losses on the performance of a SRC was also studied. The operating regions where significant deviations in de characteristics occurred due to losses were also identified. In addition, from the mode and de analysis of a PRC, a novel resonant buck converter with de gain almost insensitive to load variations was proposed. Generalized mode and de analysis applicable to all QRC topological variations were performed using state-plane diagrams. Four sets of mode and de analyses were shown to be adequate to characterize the steady-state operation of nearly a hundred QRC variations. This simplified the understanding and analysis of these converters. Also, two simple circuit rules were introduced using which several QRC topological variations were generated and evaluated based on relative component stresses. The state-plane technique was also used to understand and evaluate different control methods of a SRC. The occurrence of large, undesirable tank energy surges with analog-signal-to-discrete-time-interval-converter (ASDTIC) control was investigated and explained using state-plane trajectories. A new control method called #optimal trajectory control*, which attempts to achieve the fastest response possible was proposed. By exploiting the structure of SRC state portrait, the tank energy is always kept within bounds with this control. Experimental implementation was discussed in detail along with experimental oscillograms which confirm the predicted fast response. / Ph. D.