The design of a compact size switching converter under high switching operation causes a drastically decreasing in power conversion efficiency. This paper presents a dual modulation technique to improve the power conversion efficiency with a little increase in output ripple. Especially, the trade-off between the output ripple and the efficiency can meet the requirement of the portable devices. Simulation results show that the converter can operate at 5 MHz with a supply voltage from 3V to 4.5V. The output voltage ripple can be kept smaller than 30mV when load current varies from 20mA to 800mA. Besides, the power efficiency is higher than 85% over a wide load current range.