A direct current voltage conversion device includes a buck converter receiving a direct current input voltage and outputting a direct current first voltage according to a first control signal, a series resonant converter outputting an alternating current second voltage according to a second control signal and a third control signal, a transformer that receives the alternating current second voltage, a rectifier, and an output capacitor electrically coupled with the rectifier. The rectifier generates a direct current output voltage according to a fourth control signal and a fifth control signal, which is outputted across the output capacitor.