Commutation current steering method in a zero volt switching power converter using a synchronous rectifier

A zero volt switching (ZVS) power converter comprising:

• a plurality of switches configured to operate under ZVS conditions;
• a plurality of switches configured to operate as a synchronous rectifier;
• an isolation transformer;
• and
• control circuitry defining a controller that is configured to generate control signals to operate each of the switches, whereby the controller is functional to
• operate the synchronous rectifier switches wherein a commutation current is shared between the switches operating under ZVS conditions and the synchronous rectifier switches, and
• induce a boosting resonance during ZVS transition by controlling each of the synchronous rectifier switches to turn off at a time prior to a turn-off time for a corresponding one of the switches operating under ZVS conditions.

A zero volt switching (ZVS) power converter for converting power from an input DC voltage source to a variable load, the ZVS power converter comprising:

• an isolation transformer;
• a plurality of switches positioned on a primary side of the isolation transformer and configured to operate under ZVS conditions, the power converter comprising a defined minimum value for a current through the primary side switches;
• a plurality of switches positioned on a secondary side of the isolation transformer and configured to operate as a synchronous rectifier;
• a boosting resonant circuit comprising
• a total leakage inductance of the isolation transformer, and
• a Coss capacitance of the switches configured to operate as a synchronous rectifier;
• and
• switching control circuitry configured to
• operate the synchronous rectifier switches wherein a commutation current is shared between the switches operating under ZVS conditions and the synchronous rectifier switches,
• induce a boosting resonance in the boosting resonant circuit during ZVS transition by controlling each of the synchronous rectifier switches to turn off at a time prior to a turn-off time for a corresponding one of the switches operating under ZVS conditions, and
• wherein at light or zero load conditions an amplitude of the primary current greater than the defined minimum value is generated during ZVS commutation periods and an amplitude of the primary current less than the defined minimum value is generated outside of ZVS commutation periods.