This paper presents a two-stage DC-DC converter for electric vehicles that controlled by using a digital MCU with a lag algorithm. Because the fuel vehicle causes many environmental issues, the electric vehicle becomes a new tendency in vehicle fields. The voltage of power battery is very high and can’t charge for lead-acid battery directly, so DC-DC converter is an essential device. In order to absorb the advantage of digital converter and meet the requirement of widely range input voltage, a digital DC-DC converters for electric vehicle is proposed. The BUCK and half bridge topology was analysis in detail and chosen for the DC-DC converter. A digital DC-DC converter system which includes the hardware and software was designed. The sample circuit, driven circuit and how to make the power transformer is described in detail in hardware design. The software mainly consist the voltage regulate program and CAN communication program. A lag compensator was designed for the voltage regulate. A prototype was made and test in the charge of the lead-acid battery. The result shows the correctness of the topology selection and circuit design. It proved that the DC-DC converter can charge the lead-acid battery within working voltage of power battery and meet the specification basically.
