Energy Injection In A Resonant Circuit With Initial Conditions

A power conversion apparatus, comprising:

• a transformer including a primary winding, a secondary winding, and an auxiliary winding, and including a magnetizing inductance;
• an output;
• a first switch connected to the primary winding to control a current through the primary winding, wherein the first switch has a parasitic capacitance across the first switch;
• at least one secondary switch connected to the secondary winding;
• a unidirectional switch connected to the auxiliary winding;
• a voltage injection voltage source connected in series to the unidirectional switch and further connected to the auxiliary winding;
• and
• a controller coupled to the first and secondary switch and to the unidirectional switch, the controller configured to:
• switch the first switch on, so as to store energy in the magnetizing inductance of the transformer;
• switch the first switch off, so that the energy stored in the magnetizing inductance flows through the secondary winding and the secondary switch toward the output;
• switch the unidirectional switch on at a predetermined time interval during a conduction time of the secondary switch, so as to control a flow of a magnetizing current of the transformer through the voltage injection voltage source, so as to inject energy from the voltage injection voltage source into the magnetizing current;
• switch off the unidirectional switch at a predetermined time prior to the turn on of the primary switch, wherein the magnetizing current discharges the parasitic capacitance;
• and
• switch the first switch on at a predetermined voltage across the first switch.

A power conversion apparatus, comprising:

• a transformer including a primary winding, a secondary winding, and an auxiliary winding;
• a first switch connected to the primary winding to control a current through the primary winding, wherein the first switch has a parasitic capacitance across the first switch;
• an output;
• at least one secondary switch connected to the secondary winding;
• a unidirectional switch formed by a third switch in series with a diode;
• a voltage injection voltage source connected in series with the unidirectional switch and further connected to the auxiliary winding;
• a current source producing a pulse of current connected to the auxiliary winding and reflected into the primary winding with a polarity which discharges the parasitic capacitance across the first switch;
• and
• a controller coupled to the first switch, the secondary switch, the current source and to the unidirectional switch, wherein the controller is configured to:
• switch the first switch on, so as to store energy in a magnetizing inductance of the transformer;
• switch the first switch off, so that the energy stored in the magnetizing inductance flows through the secondary winding and the secondary switch toward the output;
• switch the unidirectional switch on at a predetermined time interval during a conduction time of the secondary switch, so as to control a flow of a magnetizing current of the transformer through the voltage injection voltage source, so as to inject energy from the voltage injection voltage source into the magnetizing current;
• switch off the unidirectional switch at a first predetermined time prior to the turn on of the primary switch and turn on the current source after a second predetermined time after the turn off of the unidirectional switch, further discharging the parasitic capacitance across the first switch;
• and
• switch the first switch on at a predetermined voltage across the first switch.