SummaryThe quadratic DC‐DC converter can broaden the voltage conversion ratio, which meets the requirements of wide input voltage. However, large‐scale variation of input voltage puts forward harsh requirements on ability to resist input disturbance of control strategy. Quadratic buck converter (QBC) is pulsed nonlinear dynamic systems, so the one‐cycle control strategy based on robustness principle may provide better rejection of power source than the linear feedback control. But the traditional one‐cycle controlled QBC (TOCCQBC) suffers from poor ability against load disturbance and steady‐state error. To overcome aforementioned shortages, an improved OCCQBC is proposed by adding inductor current to diode voltage as integral variable and introducing feedback of output voltage. The paper first introduces the working principle of the QBC, and second, the OCCQBC is presented. Then, a mathematical model using small signal analysis of the OCCQBC is established, and an experimental prototype with a power of 6 W is set up. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the strategy.