Abstract: A buck DC-DC control method based on peak current mode is proposed in this paper with improved light-load efficiency.This method use peak current switch and sample hold circuits to achieve high efficiency within wide load current range.According to load current conditions,the peak current switch determines light-load or heavy load.Under the light-load conditions,through controlling the variation of error signal,the sample hold circuits turn on or turn off the converter cyclically to obtain switching frequency modulation.Based on 0.5 μm BCD process,the simulation results shows that under the condition of 12 V input and 3.3 V output,the maximum efficiency can be up to 96% and it can keep 80.3% at 10 mA of load current.