Design of a High Efficiency Boost DC-DC Converter

An accurate circuit of PWM/PFM mode converting and a circuit of auto-adaptively adjusting dimension of power transistor are described.The duty cycle of the signal when the control mode converts can be gained accurately by using ratios of currents and capacitances,and an optimal dimension of power transistor is derived with different loads.The converter is designed by 0.35μm standard CMOS technology.Simulation results indicate that the converter starts work at 0.8 V input voltage.Combined with synchronized rectification,the transfer efficiency is higher than 90%with full load range,and achieves 97.5%at rating output.