High-voltage DC–DC converter based on adaptive frequency conversion modulation

With the development of electric vehicles, the demand for the high-voltage low-current DC-DC chips used in vehicle on-board equipment continues to grow. To improve the efficiency of the switching power supply, an asynchronous buck high-voltage DC-DC converter with adaptive variable frequency modulation (AVFM) technology is designed in this paper. This work focuses on the efficiency optimization of the buck converter, and the relationship between power consumption and operating frequency under different loads. The optimal frequency range is selected during light and heavy loads, and adaptive transition of the frequency is realized during a medium load. Using a threshold voltage ( V th_cs ) circuit with an adjustable current inside the chip, the on-time of the switch is changed to realize frequency conversion. The whole chip design is based on 0.35 μm BCD process, in which the integrated LDMOS can withstand 200 V. System simulations are completed in Cadence. The results show that when the input voltage is 30–60 V and the output specification is 5 V/0.5 A, the system realizes adaptive frequency conversion in the entire load range, and the efficiency reaches 88.9%. The actual performance of the chip meets the design requirements and has good EMI characteristics.