In order to meet the requirements of wide voltage amplitude, wide frequency input, high power density, high efficiency and frequency measurement of three-phase AC generator back-end DC regulated power supply, a high power density power supply converter based on LTC3789 is studied. The high performance boost-buck switching regulator LTC3789 is used as the main control circuit to design circuit. Use voltage zero crossing detection circuit to detect generator frequency, and carry out test for power supply. The results show that the output voltage of the power supply circuit is stable, the power density and efficiency are high, and the power supply meets the requirements of operation.