Ikko HARADA Fumio UENO Takahiro INOUE Ichirou OOTA
For a realization of a DC-DC converter using no magnetic devices, a new switched capacitor (SC) transformer is introduced, which gives voltage ratios by Fibonacci series corresponding to the stages. This transformer is connected in cascade by each basic block which is assembled by a capacitor and three MOSFET switches. This operates on a simple two-phase clock and has a large step-up or step-down voltage ratio in spite of its simple configuration. The characteristics of this transformer with n stages of basic block are derived and calculated by means of a 4 4 cascade matrix. The optimal arrangement of each stage's capacitances is shown to reduce the SC resistance by about 20%. The simulation results are compared with the characteristics of a prototype transformer with four stages (8 times step-up ratio). Its power efficiency achieves 88% in case of 97 V output voltage, 0.2 A output current, and 100 kHz switching frequency. Lastly, the proposed SC transformer is compared and discussed with other typical SC transformers.