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The input current ripple problem of DC/DC converters receives more and more attention recently. To meet the increasingly demanding requirements, the fundamental components of the current ripple are researched and the corresponding current ripple reduction methods are proposed in this paper. On the one hand, due to the imbalance between the input and output power of the whole system when connected to the grid, the 100-Hz bus voltage ripple is induced. If the bus voltage ripple cannot be regulated effectively, the 100-Hz ripple will be reflected in the DC input side. On the other hand, with low pulse-width modulation (PWM) resolution, the quantized error of digital control is accumulated, which causes the quantized input current ripple. The 100-Hz ripple and the quantized ripple are the main input current ripple components. To solve the problems, a small-signal model of the DC/DC converter is built to calculate the input current ripple mathematically. Based on the theoretical analysis, the proportional–integral–differential-resonant (PIDR) control is proposed and high-resolution pulse-width modulation (HRPWM) technology is applied. Finally, a 2-kW bidirectional DC/DC converter prototype is built. According to the experiments, the current ripple is reduced dramatically by 81.5% at full load with the proposed current ripple reduction methods.