Parallel connected converters apparatus and methods using switching cycle with energy holding state

A power converter apparatus, comprising:

• an input port;
• an output port;
• a first transformer having a primary winding and a secondary winding;
• a first switching circuit coupled to the input port and the primary winding of the first transformer, the first switching circuit operative to repetitively perform a cycle comprising a first state in which the first switching circuit couples the input port to first and second terminals of the primary winding of the first transformer, a second state in which the first switching circuit couples the first terminal of the primary winding of the first transformer to the second terminal of the primary winding of the first transformer, and a third state in which the first switching circuit decouples at least one of the first and second terminals of the primary winding of the first transformer from the input port while decoupling the first and second terminals of the primary winding of the first transformer from one another;
• a second transformer having a primary winding and a second winding;
• a second switching circuit coupled to the input port and the primary winding of the second transformer, the second switching circuit operative to cyclically transition through a first state in which the second switching circuit couples the input port to first and second terminals of the primary winding of the second transformer, a second state in which the second switching circuit couples the first terminal of the primary winding of the second transformer to the second terminal of the primary winding of the second transformer, and a third state in which the switching circuit decouples at least one of the first and second terminals of the primary winding of the second transformer from the input port while decoupling the first and second terminals of the primary winding of the second transformer from one another;
• and
• an output circuit coupled to the secondary windings of the first and second transformers and operative to transfer energy to the output port from the secondary windings of the first and second transformers as the first and second switching circuits cyclically operate.

A method of operating a power converter, the method comprising:

• repeatedly performing a first power conversion cycle comprising:
• applying a voltage across first and second terminals of a primary winding of a first transformer;
• coupling the first and second terminals of the primary winding of the first transformer to one another;
• and
• decoupling the first and second terminals of the primary winding of the first transformer to induce a current pulse in a secondary winding of the first transformer;
• and
• repeatedly performing a second power conversion cycle comprising:
• applying a voltage across first and second terminals of a primary winding of a second transformer;
• coupling the first and second terminals of the primary winding of the second transformer to one another;
• and
• decoupling the first and second terminals of the primary winding of the second transformer to induce a current pulse in a secondary winding of the second transformer.