Application of Integrated Magnetics in Resonant Converters

Abs t rac t -The phys ica l s ize of inductors in resonant converters was examined i n terms o f inductor t o transformer s i z e rat io . F o l l o w i n g the general d i scuss ion o f the i s s u e , the inductor s i z e i n ser i e s resonant DC-DC converter i s examined i n deta i l . It i s shown that the inductor t o transformer s i z e rat io i s a funct ion of the peak v o l t a g e o f the inductor t o the rms v o l t a g e o f the transformer and i s independent of the inductance. The p h y s i c a l s i z e o f the inductor could be much larger than the transformer when the converter operates near resonance . Away from resonance , the inductor s i z e becomes c l o s e t o , and e v e n smal ler , than the transformer. Leakage inductance o f the transformer can be used as the resonant inductance but i f the leakage i s assoc iated with the secondary windings of the transformer, i t wi l l increase the peak reverse vol tage of the rect i f i er diodes when a center-tapped rectif ier t o p o l o g y i s used. To s o l v e t h i s problem, an integrated transformer-inductor e lement wi th high primary leakage inductance and l o w secondary leakage i s proposed and tes ted . The experimental unit was bui l t for a power l e v e l o f 1KVA and switching frequency range 30 60 kHz.