A DC voltage conversion device comprising: first conversion means, transformation means connected to the first conversion means, and superposition and rectifying means connected to the first conversion means and to the transformation means, and supplying an output voltage comprising pulses having equal amplitudes to the sum of the amplitudes of the pulses of the primary and the secondary pulsed voltage. A converter for converting a DC voltage into AC voltage comprising the DC voltage conversion device, filtering means being connected on output of the superposition and rectifying means of said conversion device.An uninterruptible electric power supply comprising a converter for converting a DC voltage into AC voltage connected to storing means, said converter comprising the DC voltage conversion device to convert the DC voltage of said storing means.