Power conversion apparatus and methods with reduced current and voltage switching

A power conversion apparatus, comprising:

• a transformer having primary and secondary windings;
• first and second half-bridges configured to be coupled across a DC power source and coupled to respective first and second terminals of the primary winding of the transformer;
• an output circuit coupled to the secondary winding of the transformer and including first and second capacitors and at least one inductor configured to be coupled to a load, the output circuit operative to transfer energy to the load from the secondary winding via the first capacitor responsive to application of a first polarity voltage to the primary winding of the transfer and to transfer energy to the load from the secondary winding via the second capacitor responsive to application of a second polarity voltage to the primary winding of the transformer;
• and
• a switch control circuit, operatively associated with the first and second half-bridges, that varies a frequency at which the first and second half-bridges operate responsive to an output voltage produced by the output circuit.

A power conversion apparatus, comprising:

• a transformer having primary and secondary windings;
• a switching circuit coupled to the primary winding of the transformer and configured to be coupled to a DC power source, the switching circuit operative to couple the DC power source to the primary winding of the transformer with a first polarity in a first state and to couple the DC power source to the primary winding of the transformer with a second polarity in a second state;
• and
• an output circuit coupled to the secondary winding of the transformer and including first and second capacitors and at least one inductor configured to be coupled to a load, the output circuit operative to transfer energy to the load from the secondary winding via the first capacitor responsive to the first state of the switching circuit and to transfer energy to the load from the secondary winding via the second capacitor responsive to the second state of the switching circuit.

A power supply, comprising:

• a rectifier circuit configured to receive and AC input voltage and operative to generate a DC voltage therefrom;
• a transformer having primary and secondary windings;
• a first switching circuit coupled to the rectifier circuit and having an output port coupled to the primary winding of the transformer,
• a switch control circuit, operatively associated with the first switching circuit, that causes the first switching circuit to alternately apply the DC voltage with first and second polarities to the primary winding;
• first and second capacitors;
• an output inductor configured to be coupled to a load;
• and
• a second switching circuit coupled to secondary winding, the first and second capacitors and the output inductor and operative to transfer energy to the load from the secondary winding via the first capacitor responsive to application of the DC voltage with the first polarity voltage to the primary winding and to transfer energy to the load from the secondary winding via the second capacitor responsive to application of the DC voltage with the second polarity to the primary winding.

A method of converting power, the method comprising:

• alternately applying first and second polarity voltages to a primary winding of a transformer;
• transferring energy to a load from a secondary winding of the transformer via a first capacitor responsive to application of the first polarity voltage to the primary winding;
• and
• transferring energy to the load from the secondary winding via a second capacitor responsive to application of the second polarity voltage to the primary winding.