Dual active clamp, zero voltage switching power converter

A dual active clamp forward converter comprising:

• an input port for receiving a source of power and an output port for providing power to a load;
• a first converter and a second converter, each said converter having a power transformer including a primary winding coupled to said input port and a secondary winding coupled to said output port, a primary switch means coupled in series between said primary winding of said power transformer and said input port, a series combination of a first switch means and a first capacitor, said series combination of said first switch means and said first capacitor coupled in parallel with one of said primary winding, said secondary winding, and said primary switch means, and a second switch means coupled in series with said secondary winding of said power transformer, said primary switch means when closed causing a first portion of energy from the source of power at said input port to be coupled through said power transformer to the load by means of said secondary winding and causing a second portion of said energy to be stored in said power transformer;
• means for generating a first duty-cycle signal and a second duty-cycle signal, each of said first and second duty-cycle signals having a first state and a second state and operative to alternate in time between said first and second states, said second duty-cycle signal being phase-shifted in time by substantially 180 degrees from said first duty-cycle signal;
• a first control means responsive to said first duty-cycle signal for operating the primary switch means, the first switch means, and the second switch means of said first converter, said first control means causing the primary switch means of said first converter to close substantially when said first duty-cycle signal enters its respective first state and to open substantially when said first duty-cycle signal enters its respective second state, said first control means causing the first switch means of said first converter to open substantially when said first duty-cycle signal enters its respective first state and to close substantially when said first duty-cycle signal enters its respective second state, said first control means opening the first switch means of said first converter prior to when the primary switch means of said first converter closes to create a zero-voltage switching condition on said primary switch means when said primary switch means next is caused to close, said first control means opening the second switch means of said first converter substantially when the primary switch means of said first converter opens and closing said second switch means substantially when said primary switch means closes, said second switch means being operated such that substantially no current is conducted by said secondary winding of said first converter during the interval after said first switch means is opened and before said primary switch means is closed;
• and
• a second control means responsive to said second duty-cycle signal for operating the primary switch means, the first switch means, and the second switch means of said second converter, said second control means causing the primary switch means of said second converter to close substantially when said second duty-cycle signal enters its respective first state and to open substantially when said second duty-cycle signal enters its respective second state, said second control means causing the first switch means of said second converter to open substantially when said second duty-cycle signal enters its respective first state and to close substantially when said second duty-cycle signal enters its respective second state, said second control means opening the first switch means of said second converter prior to when the primary switch means of said second converter closes to create a zero-voltage switching condition on said primary switch means when said primary switch means next is caused to close, said second control means opening the second switch means of said second converter substantially when the primary switch means of said second converter opens and closing said second switch means substantially when said primary switch means, said second switch means being operated such that substantially no current is conducted by the secondary winding of said second converter during the interval after said first switch means is opened and before said primary switch means is closed.