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 (12 V or 24 V) has to be converted into a DC-voltage of 350 V, e.g. for a power transmitter. The total power to be managed is 1 kW. In the case of a single stage inverter, this leads to about 100 A input current (causing peak values in the power switches of up to 200 A). 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. In the case of the 1 kW converter described here, four stages are used.