Patent ID: 7352600

Claim:
An electric power unit, comprising: a first switching element having one end to which one level of a direct current voltage is applied; a second switching element having one end connected to the other end of the first switching element and having the other end to which the other level of the direct current voltage is applied; a third switching element having one end to which one level of the direct current voltage is applied; a fourth switching element having one end connected to the other end of the third switching element and having the other end connected to the other end of the second switching element, the other level of the direct current being applied to the other end; a first capacitor connected to any one of the first and second switching elements in parallel; a second capacitor connected to any one of the third and fourth switching elements in parallel in accordance with the first capacitor; a first coil having one end connected to a connection point of the first and second switching elements; a transformer having a primary coil connected between the other end of the first coil and the connection point of the third and fourth switching elements; fifth and sixth switching elements connected in series between the both ends of a secondary coil of the transformer; a third capacitor connected between a middle tap point of the secondary coil of the transformer and the connection point of the fifth and sixth switching elements; and a control section which controls the first to sixth switching elements on the basis of the output voltage between the both ends of the third capacitor, wherein there is no period of time when any of the first and second switching elements and the third and fourth switching elements is turned on in a certain switching frequency, any one switching element is turned on in a period of time except for a dead time period for a zero voltage switching, the first and third switching elements and the second and fourth switching elements are turned on and off while shifting phases by 180 degrees, and the fifth and sixth switching elements are turned on during a period of time when currents in a positive direction and an inverse direction are flowing to the output, respectively, and to be operated in a discontinuous current mode, and satisfying Vout=Ton 2 •( n •Vin) 2 /{2•Iout•( L•n 2 )• Ts +( n •Vin)•Ton 2 } wherein Vout is output voltage of the electric power unit, Ton is an on-period of the first and third switching elements, n is a turn ratio 1:n between the primary coil and the secondary coil, Vin is the direct current voltage, Iout is output current of the electric power unit, L is an inductance of the first coil, and Ts is a switching period of a circuit of the first, second, third, fourth, fifth, and sixth switching elements, the first, second, and third capacitors, the first coil, and the transformer.