Ferrite core

Claim 1

A ferrite core half for use in a power supply circuit comprising: (a) a circular center boss (6), (b) a pair of outer walls (7, 8) positioned at both the sides of said boss for mounting a coil, (c) a pair of base plates (9, 10) coupling a portion of said boss with said outer walls, said base plates extending from the periphery of said boss to the side surface of said walls wherein said boss, walls and base plates form an E-shaped structure and wherein the end portion of said boss, end portions of said walls and said base plates are all aligned in a single plane, (d) each of the outer walls is substantially rectangular with an external linear wall and an inner curved wall which is substantially coaxial with said circular boss and the width of said external linear wall is larger than the diameter (2a 1 ) of the circular boss, (e) each of said base plates being substantially in an arc shape, and the portions of said boss which are coupled to said base plates being less than the whole of the periphery of said boss such that a space is formed between said base plates along the periphery of said boss, (f) the area (S 6 , S 7 ) coupling said base plates with said outer walls being equal to or larger than the half of the cross-sectional area (S 1 =πa 1 2 ) of said boss, (g) the area (S 2 , S 3 ) coupling said boss with the base plates being substantially the same as half of the cross-sectional area (S 1 =πa 1 2 ) of said boss, (h) the area (S 4 , S 5 ) of the cross-section of each of said outer walls being equal to or larger than the half of the cross-sectional area (πa 1 2 ) of said boss, (i) the core half being symmetrical with regard to a first plane including a center axis of said boss and being parallel with the external linear walls of said outer walls, (j) a concaved opening (R) being provided between said base plates in a first side of the core half with regard to a reference plane which includes a center axis of said boss and is perpendicular to said first plane, and said opening (R) extending to the surface of the center boss, (k) the length (B 1 ) between said reference plane to the end of the first side of the core half in the first side which includes said concaved opening being longer than the length (B 2 ) between said reference plane to the end of a second side of the core half, and (l) said length (B 2 ) being the same as the radius a 1 of the center boss.