High frequency power supply design

Abstract

Portability, power density, and energy e ciency are among the hottest topics of today. Therefore, the need for higher power-capacity, smaller size, and higher e ciency power supply is increasing day by day. At this point, the switching frequency has the most noticeable e ect on the size of switching power converters. Utilizing high switching frequency, the converter size and weight can be reduced signi cantly; in other words, the power density can be increased. In addition, the high switching frequency decreases capacitor value and therefore electrolytic capacitors can be eliminated. As a result, reliable ceramic type capacitor can be employed. The Switch Mode Power Supply (SMPS) converters utilize switching frequency as a basic feature of these converters and they have gained signi cant attraction recently due to their low weight, volume, and cost advantages. There are conventional SMPS topologies in the literature such as buck, boost, buck-boost, yback, etc., which are hard switched topologies and their switching frequency can reach only 100 kHz levels. Increasing the switching frequency of these type of converters raises the losses inevitably. Hence, the switching frequency has to be chosen low for limiting the loss. As a result, these conventional topologies require a large capacitor and inductor values. In order to solve this problem, resonant converters which have soft switching behavior are proposed in the literature, and the switching frequency can reach up to MHz level. Among these converters, class E type resonant converter has a single switch which source (for MOSFET) has a ground connection hence it is easy to drive. Additionally, this converter has an easy design advantage because it uses a low number of components. Hence, in this thesis, class E resonant converter is chosen for these advantages. In this study, a class E DC/DC converter is analyzed, simulated and implemented for in order to obtain 24 V/60 W output power from a 48 V input voltage. Additionally, 0.5 MHz and 1.2 MHz switching frequencies were selected for this particular research. On the other hand, the analyses were proven by PSIM simulations and experiments. From the experimental studies, it was seen that electrolytic capacitors can be eliminated by high switching frequency and ceramic type capacitors can be used instead of electrolytic counterparts.

Ta s nabilirlik, gu c yo gunlu gu ve enerji verimlili gi bugunlerde en onemli konular aras nda yer almaktad r. Dolay s yla, yuksek gu c yo gunlu guna, ku cuk boyuta ve yuksek verimlili ge sahip gu c kaynaklar na ihtiya c gunden gune artmaktad r. Bu noktada, yuksek anahtarlama frekans en onemli etkiye sahiptir. Yuksek anahtarlama frekans yard m yla donu sturucu boyutu ve a g rl g du surulebilir, ba ska bir deyi sle gu c yo gunlu- gu artt r labilir. Ek olarak, yuksek anahtarlama frekans n n kapasitor boyutunu azaltmas yla elektrolitik kapasitorler elimine edilebilir. Bunun sonucunda ise guvenirli gi ve omru yuksek seramik tipi kapasitorler kullan labilir hale gelmektedir. Anahtarlamal Gu c Kaynaklar (AGK), anahtarlama frekans n devrenin temel ozelli gi olarak kullan r ve bu donu sturuculer du suk a g l k, hacim ve maliyet avantaj ndan dolay onemli bir ilgi kazanm st r. Literaturde; buck, boost, buck-boost, yback gibi sert anahtarlama yapan ve anahtarlama frekans sadece 100 kHz seviyelerine kadar c kabilen geleneksel topolojiler bulunmaktad r. Bu topolojilerde anahtarlama frekans n artt rmak istenmeyen bir sekilde kay plar artt rmaktad r. Dolay s ile kay plar limitlemek amac yla anahtarlama frekans n n ku cuk se cilmesi gerekmektedir. Anahtarlama frekans n n ku cuk se cilmesinden dolay bu donu sturuculer yuksek kapasitor ve enduktans de gerlerine ihtiya c duyar. Bu problemi cozmek i cin literaturde yumu sak anahtarlama yapabilen ve anahtarlama frekans MHz seviyelerine c kabilen rezonant donu sturucu topolojileri onerilmi stir. Bu donu sturuculer i cerisinde, E s n f topoloji tek bir anahtarlama eleman kullanmas ve bu anahtarlama eleman n n sors terminalinin topra ga ba glanmas ndan dolay surme avantaj sunar. Ayr ca, E s n f donu sturucu kolay tasar ma ve du suk say da komponente sahiptir. Bundan dolay bu tezde E s n f DC/DC donu sturucunun 48 V giri s kayna g ndan 24 V/60 W c k s olu sturdu gu durum i cin analiz, simulasyon ve deneysel cal smalar yap lm st r. Ek olarak anahtarlama frekans i cin 1.2 MHz ve 0.5 MHz se cilmi s olup cal smalar bu anahtarlama frekanslar nda ger cekle stirilmi stir. Di ger taraftan, analizler PSIM simulasyonlar ve deneysel cal smalarla ispatlanm st r. Deneysel cal smalarda, yuksek anahtarlama frekans nda cal sman n bir sonucu olarak elektrolitik kapasitor yerine seramik kapasit orlerin kullan labilece gi ve elektrolitik kapasitorlerin elimine edilebilece gi gorulmu st ur.