An isolated hybrid buck converter for 48 V-1 V system is proposed, utilizing the flying capacitor and transformer to achieve high conversion efficiency in high conversion ratio applications. The hybrid converter combines the switched capacitor converter and the switched inductor converter, in which the flying capacitor is charged with part of the voltage drop to reduce the voltage stress of the power MOS. Since the voltage swing at the switch node is smaller, the switching loss is reduced accordingly. By using lower voltage power MOS, the conduction loss is reduced. Moreover, the isolated hybrid buck converter can achieve soft-switching through timing control, thereby reducing the switching loss of the power MOS, and making the overall efficiency higher. In the isolated hybrid buck converter, the flying capacitor has the function of the DC-blocking capacitor, which can prevent the magnetic bias of transformer. In the typical application, namely input voltage of 48 V, output voltage of 1 V, and switching frequency of 500 kHz, the peak efficiency is 94.84%.