Low voltage DC-to-DC converter with wide input to output voltage ratio

DC-to-DC converters with very low input respectively output voltage ratings have, due to the high current ratings, a relatively low efficiency. Therefore, it is necessary to operate several converter stages in parallel to achieve an acceptable total efficiency. Here, a possible solution for such a converter is presented. The input voltage of a (e.g. a solar buffered) battery (12V or 24V) has to be converted into a DC-voltage of 350V, e.g. for a power transmitter. The total power to be managed is 1kW. In case of a single stage inverter, this leads to about 100A input current (causing peak values in the power switches of up to 200A!). The resulting component stress is very hard and the design is also difficult to handle. To overcome this problem a topology was chosen, which uses several converter stages operating in parallel. All these stages operate at the same transformer leading to an optimal flux exploitation of the core. Figure I depicts the realization principle for a two-converter solution. In the case of the 1kW converter described here, four stages are used.