Patent ID: 6388896
Filing Date: 2002-05-14
Classification: H02M,Y02B

Abstract:
A converter for providing power from a DC voltage source connected between an input terminal and a common input terminal to a DC load connected between an output terminal and a common output terminal, said converter comprising:an input inductor winding, a middle inductor winding, and an output inductor winding placed on a common magnetic core to form a DC Transformer, and each winding having one dot-marked end and an other unmarked end whereby AC voltage applied to said middle inductor winding induces AC voltages in said input and output inductor windings so that said applied AC voltage and said induced AC voltages are in phase at dot-marked ends of said input, output and middle inductor windings; said input inductor winding connected at said dot-marked end thereof to said input terminal to form an input winding of said DC Transformer; said output inductor winding connected at said dot-marked end thereof to said output terminal to form an output winding of said DC Transformer; said middle inductor winding connected at said dot-marked end thereof to said common input terminal and said common output terminal to form a middle winding of said DC Transformer; an input capacitor, having one end connected to said unmarked end of said input inductor winding an other end of said input capacitor connected to said unmarked end of said middle inductor winding; an input switch with one end connected to said common input terminal and an other end connected to said unmarked end of said input inductor winding; an output switch with one end connected to said common output terminal and an other end connected to said unmarked end of said output inductor winding; a complementary output switch, having one end connected to said unmarked end of said output inductor winding and an other end of said complementary output switch connected to said unmarked end of said middle inductor winding; a branch comprising a complementary input switch and an auxiliary capacitor, having one end of said complementary input switch connected to one end of said auxiliary capacitor, while an other end of said complementary input switch and an other end of said auxiliary capacitor comprise ends of said branch; switching time control means for providing a precise sequence and timing of turning ON and turning OFF signals for said input switch, said complementary input switch, said output switch and said complementary output switch; means for connecting said ends of said branch to said converter whereby during a State-2 interval current through said branch is equal to the sum of input inductor current flowing into said dot-marked end of said input inductor winding and middle inductor current flowing into said dot-marked end of said middle inductor winding reduced by output inductor current flowing out of said dot-marked end of said output inductor winding; wherein said input switch, said output switch, and said complementary output switch are semiconductor switching devices, capable of conducting the current in at least one direction while turned ON, and sustaining voltage in at least one direction while turned OFF; wherein said complementary input switch is a semiconductor current bidirectional switching device, capable of conducting the current in both directions while turned ON, and sustaining voltage in at least one direction, while turned OFF; wherein said semiconductor switching devices and said semiconductor current bidirectional switching device turn ON and OFF at high switching frequency; wherein a DC-to-DC voltage conversion ratio of said converter depends linearly on a duty ratio D; wherein for said duty ratio D in a range from 0 to 1, both a DC current in said input inductor winding and a DC current in said middle inductor winding flow into said dot-marked ends of said input and middle inductor windings, whereas a DC current in said output inductor winding flows out of said dot-marked end of said output inductor winding; wherein for said duty ratio D in a range from 0 to 1, the sum of said DC currents of said input inductor winding and said middle inductor windings is equal to the magnitude of said DC current of said output inductor winding; wherein said DC Transformer includes an equal number of turns for said input, output, and middle inductor windings and, at said duty ratio D, DC ampere-turns of said input inductor winding and said middle ineductor winding are positive and generate positive DC fluxes which add together, while DC ampere-turns of said output inductor winding are negative and generate negative DC flux to result in net zero DC flux in said common magnetic core; wherein said common magnetic core has no air-gap; whereby said net zero DC flux in said common magnetic core enables increased inductances of said input, middle, and output inductor windings and said converter has increased overload capability, and whereby said DC Transformer combines said input inductor winding, said output inductor winding, and said middle inductor winding to obtain efficient DC-to-DC power transfer from said input inductor winding to said output inductor winding with reduced energy storage within said common magnetic core of said DC Transformer, thereby reducing size and weight of said converter by reducing said common magnetic core size and weight while simultaneously increasing efficiency and overload capability of said converter, and providing reduction of electromagnetic interference.