Abstract: In this paper digital cycle-borrowing current control method for buck DC-DC converters with front-edge modulation is proposed to solve the contradiction between the processing speed of hardware and loop bandwidth in the current control mode.The corresponding control laws for the valley,average and peak current control methods have been established.The sub-harmonic oscillation possibly existed has been analyzed,and the corresponding solutions are provided.The robustness of buck DC-DC converters with digital cycle-borrowing current control is also given.The simulation results show that the digital cycle-borrowing current control for buck DC-DC converters with front-edge modulation achieved the same transient response performances as the no beat current control,and also it matched the hardware processing speed better.