Im Mittelpunkt der vorliegenden Dissertation stand die Herstellung von organischen Leuchtdioden und Passiv-Matrix-Displays an einer neuartigen Durchlauf-Depositionsanlage. Die Abscheidung von "small molecule" Materialien im Hochvakuum wurde dabei mittels organischer Molekularstrahldeposition (OMBD) durchgeführt. Um effiziente Leuchtdioden zu erzielen, sind die Bauelemente als Mehrschichtsystem aufgebracht worden. Als Grundstruktur kam eine Schichtenfolge zur Anwendung, die als Löchertransporter aus dem Starburst-Derivat 2-TNATA, daran anschließend einem tertiären Arylamin, dem elektronenblockierenden a-NPB sowie dem Oxinat-Komplex Alq3 besteht. Dabei diente das Aluminium-Oxinat als Elektronenleiter und Emissionsmaterial. Mit dem Quinacridon-Derivat QAD als Dotierstoff wurde außerdem eine OLED-Struktur mit Gast-Wirtsystem realisiert Eine kontrollierte und reproduzierbare Deposition der organischen Materialien ist eine unabdingbare Voraussetzung, um organische Leuchtdioden kommerziell als Mehrschichtbauelemente herstellen zu können. Dazu wurde ein Hochvakuumsystem der Firma Applied Films installiert und in Betrieb genommen. Die VES 400/13-Entwicklungsanlage ist als Vertical Evaporation and Sputtering Durchlaufsystem für bis zu 400 mm hohe Substrate mit 11 individuellen Prozesskammern sowie zwei daran anschließenden Stickstoffboxen konzipiert. Diese Technologie ermöglicht das Aufdampfen einer oder nacheinander mehrerer Schichten auf beliebiges Substratmaterial. Entsprechend den Erfordernissen sind wichtige Prozessparameter wie Depositionsrate, Transportgeschwindigkeit des Substrates sowie Filmdicke der funktionellen Schichten in einem weiten Bereich frei einstellbar. Neben einer ausgeglichenen Löcher- und Elektroneninjektion werden die Eigenschaften der hergestellten Leuchtdioden durch die Dicken der einzelnen Schichten, der Beweglichkeit der Ladungsträger in den verwendeten organischen Materialien sowie der energetischen Lage der höchsten besetzten und niedrigsten unbesetzten Molekülorbitale der Halbleiter bestimmt. Als undotierte OLED-Struktur wurde eine Schichtenfolge aus ITO / 2-TNATA / NPB / Alq3 / Mg verwendet. Die Stärke der elektrischen Kontakte betrug jeweils etwa 150 nm für ITO bzw. Magnesium. Die organischen Halbleiterfilme verfügten über Lagendicken von 60 / 10 / 60 nm. Eine derart aufgebaute Leuchtdiode zeigte ein grünes Emissionsspektrum, dessen Mittenwellenlänge bei etwa 537 nm lag und eine Halbwertsbreite von circa 112 nm aufwies. Für die Betriebsspannung, die Leuchtdichte, die Strom- sowie die Leistungseffizienz ergaben sich für die beiden Stromdichten von 3 mA/cm² und 30 mA/cm² optimierte Werte zu 5,3 V bzw. 9,4 V, 100 cd/m² bzw. 1317 cd/m², 3,3 cd/A bzw. 4,4 cd/A sowie 2 lm/W bzw. 1,5 lm/W. Das Sperr- oder Gleichrichtungsverhältnis Gv wurde für die beiden gemessenen Maximal-spannungen von ±10 Volt zu <5 x 107 bestimmt. Durch die Dotierung der Alq3-Emissionsschicht mit etwa 1 mol% des Quinacridon-Derivats QAD und Hinzufügen einer separaten Elektronentransportschicht konnte eine Steigerung der Elektrolumines-zenz erreicht werden. Der OLED-Aufbau des Gast-Wirt-Systems verfügt über einen Schichtenstapel mit den Lagen ITO / 2-TNATA / NPB / Alq3 + QAD / Alq3 / Mg. Die Filmdicken der organischen Schichten der OLED mit den besten Eigenschaften betragen 60 / 10 / 35 / 25 nm. Die anorganischen elektrischen Kontakte waren jeweils etwa 150 nm dick. Die dotierten Bauelemente zeigen ein bei einer Mittenwellenlänge von 527 nm emittierendes, grünes Spektrum. Mit einer geringen Halbwertsbreite von 28 nm ist die Bedingung einer schmalen Emissionsbreite für die Anwendung in OLED-Displays erfüllt. Die Betriebsspannung, die Leuchtdichte, die Strom- und die Leistungseffizienz ergeben für die beiden Stromdichten von 6,2 mA/cm² und 45,6 mA/cm² optimierte Werte zu 10,8 V bzw. 17,0 V, 445,4 cd/m² bzw. 3816,7 cd/m², 7,2 cd/A bzw. 8,4 cd/A sowie 2,1 lm/W bzw. 1,6 lm/W.

Master of Science / Department of Architectural Engineering and Construction Science / Raphael A. Yunk / Sustainable design and green engineering practices have become a priority in the architectural design industry over the past few years. Energy codes and standards have become more stringent as energy costs rise and buildings become larger, consuming more energy and having a larger impact on the environment. One major area for improvement to meet these new requirements is in the lighting area. Kansas State University (KSU) in Manhattan, KS has had the same campus walkway lighting system for over 50 years and it does not meet the current energy codes and standards. This paper will perform a case study of the current walkway lighting system on the KSU campus, specifically focusing on the Quad area and applying the same principles to the entire campus. The illumination and fixture distribution characteristics will first be established and analyzed to determine an accurate baseline for later comparison. Issues regarding the illumination, efficiency, aesthetics, maintenance, and landscaping will be addressed once the current conditions are established. Lighting technology has changed dramatically in the past year with the development of high efficiency fluorescent, induction, and light emitting diode (LED) lighting. New LED technology has proven to be the most efficient and has been adapted to create outdoor LED fixtures that could help KSU surpass the current energy standards and improve the overall quality of light to correct some of the current issues the existing lighting creates. A full analysis of the illumination, efficiency, aesthetics, and economic feasibility will be performed. The economic analysis will compare existing maintenance and energy costs to that of the first-cost with maintenance, and energy costs to determine an estimated payback. Once the analysis is complete, future options for KSU to implement new lighting technology will be discussed. By creating a more environmentally conscious campus, using high efficiency lighting, KSU could set an example for other universities to pursue sustainable technology and design.

This thesis describes investigations into the optical and device design of organic light-emitting diodes (OLEDs) with the aim of exploring the factors controlling the spatial emission pattern of OLEDs and developing novel OLEDs with directional emission by applying wavelength-scale photonic microstructure. The development of directional OLEDs was broken down into two steps: the development of efficient narrow linewidth OLEDs and the integration of wavelength-scale photonic microstructures into narrow linewidth OLEDs. The narrow linewidth OLEDs were developed using europium (Eu) complexes. The electrical optimisation of solution-processed Eu-based OLEDs using commercially available materials was investigated. The optimised Eu-based OLEDs gave an external quantum efficiency of 4.3% at a display brightness of 100 cd/m². To our knowledge, this is the highest efficiency reported for solution-processed Eu-based OLED devices, and the efficiency roll-off has been reduced compared with other reported references. Photonic microstructures were applied to develop directional OLEDs using the efficient Eu-based OLEDs. Two contrasting strategies were used. One was to embed photonic microstructures into Eu-based OLEDs, the other was to couple photonic microstructures externally onto the devices. The microstructured devices developed by the former strategy boosted the emitted power in desired angles in both s- and p-polarisations and doubled the fraction of emission in an angle range of 4⁰. The devices developed by the external coupling strategy achieved even higher directionality and the out-coupled emission was a confined beam with easy control of beam steering. Around 90% of the emitted power was confined in an angular range of 20⁰ in the detection plane. The optical properties can be optimised independently without compromising the electrical properties of devices, which gives major advantages in terms of effectiveness and versatility. Optical models were also developed to investigate the out-coupling mechanism of various trapped modes and develop OLEDs with stronger directionality.

Gallium nitride (GaN)-based light-emitting diodes (LEDs) with cylindrical nanostructures have been the subject of significant research interest in the past decade, due to the potential of such structures to increase light extraction efficiency and deliver highly directional light emission. Nanorod LEDs, where the light emission is within the nanocylinder, have the additional potential to increase internal quantum efficiency and emit in colours previously thought impractical with GaN-based LEDs. Optical modelling of nanostructured LEDs is usually carried out using finite-difference time-domain methods, which are computationally intensive and do not always provide sufficient insight into the physics underlying the simulation results. This thesis proposes an intuitive, quasi-analytic method based on modal expansion. It is found that it is possible to calculate the far field diffraction patterns of all guided modes supported by a single nanorod, with full consideration of Fabry-Perot effects, in minutes using a standard office desktop computer. Focus is placed on the case of a nanorod of radius 140 nm, for which angular photoluminescence measurements were available to provide a means of validating the model. Consideration of the guided modes alone provides a compelling explanation for gross features in the measured data where none previously existed. It is shown that, using a standard equation from a textbook, it is possible to calculate how much each of the guided and radiation modes of a single nanorod is excited by a Hertzian dipole of known position and orientation with respect to the nanorod geometry. When interference between these modes is considered, it is possible to calculate the total far field angular emission pattern due to that dipole. Comparing these patterns with photoluminescence measurements allows one to infer the locations and orientations of dipole current sources; the results are found to be consistent with those of cathodoluminescence studies.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-25T20:32:22Z No. of bitstreams: 3 Dissertacao_JLFB_VFinal.pdf: 18601269 bytes, checksum: ec6c9955a2f1d95120cab2f797232e97 (MD5) Capa Dissertacao_JLFB_VFinal.pdf: 4769532 bytes, checksum: 3d15c52d57be870999449e2a7b78fbb3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-26T11:57:17Z (GMT) No. of bitstreams: 3 Dissertacao_JLFB_VFinal.pdf: 18601269 bytes, checksum: ec6c9955a2f1d95120cab2f797232e97 (MD5) Capa Dissertacao_JLFB_VFinal.pdf: 4769532 bytes, checksum: 3d15c52d57be870999449e2a7b78fbb3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-26T11:57:17Z (GMT). No. of bitstreams: 3 Dissertacao_JLFB_VFinal.pdf: 18601269 bytes, checksum: ec6c9955a2f1d95120cab2f797232e97 (MD5) Capa Dissertacao_JLFB_VFinal.pdf: 4769532 bytes, checksum: 3d15c52d57be870999449e2a7b78fbb3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-06-14 / The purpose of this work is to present a methodology for optimizing the geometry of the Light Emitting Diode (LED) secondary lens, in non-imaging applications, which focuses on the distribution of illuminance on a target plane. The simulation of Ray Tracing is produced by stochastic method and the optimization process based on heuristic search interacts with Ray Tracing to nd the optimized parameters of the LED secondary lens geometry. / O propósito deste trabalho e apresentar uma metodologia para otimiza ção da geometria da lente secund ária de Light Emitting Diode (LED) para aplica ção em iluminação, tendo como enfoque a distribuição da iluminância sobre um plano alvo. A simulação do Ray Tracing e produzida através do m etodo estoc astico e o processo de otimização interage com o Ray Tracing através de um m étodo heur ístico na busca dos parâmetros otimizados da geometria da lente secundária do LED.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-05-24T17:46:47Z No. of bitstreams: 1 BeneditaCosta.pdf: 3463817 bytes, checksum: f105e5bbf653ecaa37f7e7f59c1026ce (MD5) / Made available in DSpace on 2017-05-24T17:46:47Z (GMT). No. of bitstreams: 1 BeneditaCosta.pdf: 3463817 bytes, checksum: f105e5bbf653ecaa37f7e7f59c1026ce (MD5) Previous issue date: 2017-03-29 / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / The use of LEDs was evaluated as attractants for insect vectors and there are several advantages over the standard incandescent lamp favoring the use of LED technology as alternative light source for sampling medically important mosquitoes. Therefore, other studies were conducted in order to evaluate the response to the different wavelengths; however data on the use of LEDs and light intensity to attract anopheline mosquitoes are scarce. This study main purpose was to evaluate the efficiency of LEDs and the influence of the light intensity in the captures of malaria vectors upon the lunar phases, in a peridomiciliary area in northeastern Maranhão, Brazil. In the first essay, incandescent lamps routinely used in CDC-type light traps were replaced for 5 mm LEDs (green – 520 nm; blue – 470 nm) to evaluate the response of anopheline mosquitoes to those alternative light sources. However, the incandescent lamp was used as control. To test the influence of moonlight, the collections were undertaken under the four lunar phases during the study period. In the second essay, it was analyzed the influence of light intensity on the captures of mosquitoes, six light traps with LEDs of different light intensities were used: green (10,000 mCD, 15,000 mCD and 20,000 mCD) and blue (4,000 mCD, 12,000 mCD and 15,000 mCD). As a result in the first essay, 1,845 specimens and eight species foi was sampled. The most frequent species were Anopheles evansae, accounting for 35.2%, followed by An. triannulatus s.l.(21,9%), An. goeldii (12,9%) and An. argyritarsis (11,5%). The green LED was the most efficient light source, it had attracted 43.3% of the individuals, followed by the blue LED (31.8%) and the control (24.9%). The LED traps were more attractive than the control, regardless the lunar phase. In all tests, the captures were more efficient when LEDs were used to attract the anopheline mosquitoes than when the control was used. As a result in the second essay, a total of 1,650 specimens and five species of anopheline mosquitoes were sampled. The blue LED attracted more individuals (953) than the green one (697). According to the light intensity, the green LED 20.000mCD had a greater attractiveness showing 39.2% increase related to the others intensities. While the blue LED 15.000mCD has attracted 50.2% of the specimens captured. The efficiency of LEDs improves light trapping results and it is suggested that the use of LEDs as an attractant for anopheline mosquitoes should be taken into consideration when monitoring mosquito populations. Thus, the light intensity was a very important factor in enhancing the light trap performance in attracting the mosquitoes; more intense the light, more insects attracted. However, the light intensity is an important attribute for sampling more efficiently insect vectors. / O uso diodo emissor de luz (LED) foi avaliado como atrativo para insetos vetores e tem apresentado varias vantagens sobre a lâmpada incandescente convencional, favorecendo o uso da tecnologia LED como uma fonte de luz alternativa para a amostragem de mosquitos de importância médica. Além disso, outros estudos foram realizados a fim de examinar a resposta a diferentes comprimentos de onda, entretanto dados sobre o uso de LED e sua intensidade luminosa para atrair mosquitos anofelinos são escassos. Esse estudo teve como propósito avaliar a eficácia de LEDs e a influência da intensidade da luz nas capturas de mosquitos anofelinos, diante das fases lunares, em área peridomiciliar no Nordeste do Maranhão. No primeiro ensaio as lâmpadas incandescentes convencionais utilizadas em armadilhas luminosas do tipo CDC foram substituídas por LEDs de 5 mm (verde: 520 nm; azul: 470 nm) para avaliar a resposta de mosquitos anofelinos às fontes de luz alternativas, a lâmpada incandescente foi utilizada como controle. Para testar a influência da fase lunar, as coletas foram realizadas sob as quatro fases lunares durante o período de estudo. No segundo ensaio foi analisado a influência da intensidade luminosa nas capturas de mosquitos, foram utilizadas seis armadilhas luminosas com diferentes intensidades de luz: verde (10.000mCD, 15.000mCD, 20.000mCD) e azul (4.000mCD, 12.000mCD, 15.000mCD). Como resultado do primeiro ensaio, um total de 1.845 espécimes e oito espécies foram coletados. As espécies mais frequentes foram Anopheles evansae, representando 35,2%, seguido por An. triannulatus s.l. (21,9%), An. goeldii (12,9%) e An. argyritarsis (11,5%). O LED verde foi à fonte de luz mais eficaz, tendo atraído 43,3% dos indivíduos, seguido do LED azul (31,8%) e o controle (24,9%). As armadilhas com LED foram mais atrativas do que o controle, independentemente da fase lunar. Em todos os testes, as capturas foram mais eficientes quando os LEDs foram usados para atrair os mosquitos anofelinos do que quando utilizou-se o controle. Como resultado do segundo ensaio, um total de 1.650 espécimes e cinco espécies de mosquitos anofelinos foram capturados. A armadilha com LED azul atraiu mais indivíduos (953) do que o verde (697). Quanto às intensidades de luz, o LED verde de 20.000mCD obteve maior atratividade com 39,2% em relação às demais intensidades. Enquanto o LED azul de 15.000mCD atraiu 50,2% dos individuos capturados. A eficiência dos LEDs melhora os resultados de captura com luz, sugere-se o uso de LEDs como atrativo para mosquitos anofelinos e deve ser levado em consideração nas atividades de monitoramento de populações de mosquitos. Além disso, a intensidade luminosa é um fator importante para aumentar o desempenho da armadilha luminosa na atração dos mosquitos, quanto mais intensa a luz, mais insetos são atraídos. Portanto, a intensidade luminosa dos LEDs é um importante atributo para amostragem de insetos vetores.

Observando o atual interesse em polímeros organometálicos para diversas aplicações, foi feita a síntese de uma série de polímeros conjugados contendo ferroceno na cadeia principal visando à investigação de suas propriedades, em especial fenômenos magnetorresistivos, magneto-ópticos e de óxido-redução. Os polímeros preparados pelo método de McMurry foram os seguintes: PFV: poli(1,1\'-ferrocenilenovinileno) e PFV-DOPPV-M: poli[1,1\'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno]. Outros dois polímeros foram preparados utilizando o método de polimerização de Wittig, o PFV-DOPPV-W: poli[1,1\'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno] e o PFV-DMPPV: poli[1,1\'-ferrocenileno-vinileno-alt-(2,5-dimetóxi)-1,4-fenilenovinileno]. A síntese de polímeros contendo segmentos π-conjugados equenos e bem definidos separados por segmentos não-conjugados é uma das melhores stratégias para a obtenção de polímeros emissores de luz azul. Com base nesse argumento foi feita a síntese de uma série de polímeros contendo um derivado metoxilado de bisfenol-A (BPA) na cadeia principal, alternando-se com unidades de PPV ou PFV que apresentam segmentos conjugados bem definidos. Os polímeros preparados foram os seguintes: BPA-DOPPV:poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-(di-n-octilóxi)-1,4-divinilbenzeno]; BPA-PPV: poli[2,2-bis(4-metoxifenil)-propano-alt-1,4-ivinilbenzeno]; BPA-DMPPV: poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-dimetóxi-1,4-ivinilbenzeno]; BPA-DBPPV: poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-dibromo-1,4-divinilbenzeno] e BPA-PFV: poli[2,2-bis(4-metoxifenil)-propano-alt-1,1\'-divinil-ferroceno]. Todos os polímeros obtidos foram caracterizados por métodos espectroscópicos (UV-VIS, IR, RMN), análises térmicas, SEC, entre outras. Algumas aplicações foram estudadas para esses polímeros, tais como a construção de um eletrodo de ORP modificado, a produção de diodos orgânicos emissores de luz (OLEDs) e a determinação da resposta \"olfativa\" de sensores de gases. / Owing to the current interest in organometallic polymers and their applications, a group of conducting polymers containing ferrocene in the main chain was synthesized aiming the study of their magnetoresistive, magneto-optic and redox properties. The following polymers were prepared via McMurry method: poly(1,1\'-ferrocenylenevinylene) (PFV) and poly[1,1\'-ferrocenylenevinylene-alt-(2,5-di-n-octiloxy)-1,4-phenylenevinylene] (PFV-DOPPV-M). Two other polymers were synthesized via Wittig method: poly[1,1\'-ferrocenylenevinylene-alt-(2,5-di-n-octiloxy)-1,4-phenylenevinylene] (PFV-DOPPV-W) and poly[1,1\'-ferrocenylene-vinylene-alt-(2,5-dimethoxy)-1,4-phenylenevinylene] (PFV-DMPPV). The synthesis of polymers with well-defined small π-conjugated segments separated by non-conjugated segments is one of the best strategies to obtain blue light emitting polymers. Based on this statement the synthesis of several polymers formed by methoxylated bisphenol-A (BPA) alternated with PPV or PFV units was performed. The prepared polymers were the following: poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-(di-n-octiloxy)-1,4-divinylbenzene] (BPA-DOPPV), poly [2,2-bis(4-methoxyphenyl)-propane-alt-1,4-divinylbenzene] (BPA-PPV), poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-dimethoxy-1,4-divinylbenzene] (BPA-DMPPV), poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-dibromo-1,4-divinylbenzene] (BPA-DBPPV) and poly[2,2-bis(4-methoxyphenyl)-propane-alt-1,1\'-divinylferrocene] (BPA-PFV). All the synthesized polymers were characterized by spectroscopic methods (UV/VIS, IR, NMR), thermal analysis, SEC, among others. Some applications to these polymers were studied: a modified ORP electrode, organic light emitting devices (OLEDs) and gas sensors.

We aim to develop an implantable, optical neural imaging device by fabricating lasers and photodiodes onto a gallium arsenide substrate. Some studies suggest that lasers exhibit higher noise than light emitting diodes (LEDs) due to coherence effects – my studies aim to quantify this noise and to guide device development. To this end, I developed a model of a fluorescent imaging device which agreed with experiment. Noise analysis performed in phantom showed that laser sources exhibit temporal and spatial noise up to 10x higher than LED sources, and in vivo noise analysis also demonstrated this trend. I studied a neural injury model called cortical spreading depression in vitro in mouse brain slices and in vivo in the rat brain using laser and LED sources. Signal magnitudes in vitro are on the order of 10% and in vivo results are inconclusive. Future work will aim to reduce coherence related noise.

We aim to develop an implantable, optical neural imaging device by fabricating lasers and photodiodes onto a gallium arsenide substrate. Some studies suggest that lasers exhibit higher noise than light emitting diodes (LEDs) due to coherence effects – my studies aim to quantify this noise and to guide device development. To this end, I developed a model of a fluorescent imaging device which agreed with experiment. Noise analysis performed in phantom showed that laser sources exhibit temporal and spatial noise up to 10x higher than LED sources, and in vivo noise analysis also demonstrated this trend. I studied a neural injury model called cortical spreading depression in vitro in mouse brain slices and in vivo in the rat brain using laser and LED sources. Signal magnitudes in vitro are on the order of 10% and in vivo results are inconclusive. Future work will aim to reduce coherence related noise.

This thesis proposes a high efficiency driving circuit for multiple light emitting diode (LED) lamps with dimming feature. The driving circuit consists of essentially a high-frequency half-bridge series resonant inverter with multiple output transformers, on which primary windings are connected in series, while secondary sides are loaded by LED lamps rated at different powers with different turn ratios. By controlling the frequency of the inverter, the resonant current as well as the lamp current can be regulated simultaneously. On the other hand, the LED lamps can be dimmed individually by the associated dimming switches with integral cycle control. The tactful circuit ensures a high circuit efficiency owing to less conducting losses and zero-voltage switching (ZVS) operation of the active power switches of the inverter and zero current switching (ZCS) operation of the dimming switches. Two prototype circuits designed for 60 W three RGB LED lamps and 50 W five white light LED lamps have been built and tested to verify the analytical predictions. Experimental results demonstrate that the driving circuit can operate the LED lamps at a high efficiency with a wide dimming range. The lamp power can be dimmed to 10% with frequency control, while whole dimming range can be achieved with integral cycle control. The circuit efficiency with integral cycle control is relatively higher than that with frequency control. The measured efficiencies for the two designed circuit are 93% and 90%, respectively, under the rated powers.