A Very Wide Input Range DC-DC Converter

This paper describes a new forward DC-DC converter that regulates the output voltage for a very wide range of input voltages. In a forward converter, the voltage across the transistor switch (Tr) is the sun of the input voltage and transformer clamp voltage, and the voltage across the rectifier diode (Dr) is proportional to the transformer clamp voltage. In a conventional converter, the transformer is clamped by the input or output voltage, thus it is difficult to operate across a very wide input range, because the voltage across Tr and Dr may exceed their rated voltages. In order to reduce these voltage on the switching elements, a transformer clamp voltage control method is used. In this converter, the voltage accross Tr is constant and that across Dr is inversely proportional to the input voltage.