Fully integrated isolated dc-dc converter using micro-transformers

We demonstrated a fully integrated isolated dc-dc converter using coreless micro-transformers. The transformers are switched resonantly at 170 MHz to achieve efficient energy transfer while the energy regulation is realized through a 500 KHz PWM feedback signal which controls the duty cycle that this 170 MHz resonant action is left on. Both the transformer switches and Schottky diodes used for rectification are implemented on chip. 5 kV isolation is achieved through 20 mum thick polyimide layers sandwiched in between the primary coils and the secondary coils. The feedback PWM signal is transmitted across isolation barrier with on-chip transformers also through appropriate encoding and decoding. The converter packaged in a 16L small-outline integrated circuit (SOIC) is measured to deliver 0.5 W isolated power at 33 % efficiency.