An adaptive frequency control (AFC) technique is proposed for minimizing transient dropout voltage and response time of switching DC-DC converters. As we know, nonlinear fast-transient techniques with fixed switching frequency can effectively regulate the unstable output voltage back to steady-state within a short time. However, they suffer from oscillation problem because of large sourcing or sinking recovery current at output of error amplifier by fast transient circuit. Therefore, linear operation provided by AFC technique can dynamically and smoothly adjust the switching frequency, which is proportional to the output voltage variation, to regulate output voltage back to its steady-state value. In other words, AFC technique eliminates system and sub-harmonic oscillation scenarios. Experimental results demonstrate the transient dropout voltage is improved 37.8% when load current changes from 100 mA to 500 mA.