A coil device 10 comprises a first bobbin 40 having a first bobbin plate 42 provided with a first hollow cylinder 44 on which a primary coil 20 is wound at the outer periphery, and a second bobbin 50 mounted on the first bobbin 40 and having a second bobbin plate 52 provided with a second hollow cylinder 54 on which a secondary coil 30 is wound at the outer periphery. A winding center C 1 of the primary coil 20 and a winding center C 2 of the secondary coil 30 displace with a predetermined displacement (Lx) along a predetermined reference direction X.
1. A coil device comprising;
a first bobbin provided with a first hollow cylinder on which a primary coil is wound at the outer periphery, and
a second bobbin mounted on said first bobbin and provided with a second hollow cylinder on which a secondary coil is wound at the outer periphery, wherein; a winding center of said primary coil and a winding center of said secondary coil displace with a predetermined displacement along a predetermined reference direction;
said first bobbin and said second bobbin are assembled so that a first through hole of said first hollow cylinder is connected with a second through hole of said second hollow cylinder,
a middle leg of a ferrite core is inserted into these first through hole and second through hole, and
a proportion of said predetermined displacement with respect to a predetermined reference length of the middle leg of said ferrite core along said predetermined reference direction is 0.05 to 0.30.
2. The coil device as set forth in claim 1 , wherein;
said ferrite core is composed of a first core and a second core which are divisible,
a first middle leg of said first core fits into a first through hole of said first hollow cylinder,
a second middle leg of said second core fits into a second through hole of said second hollow cylinder, and
a combination of said first bobbin and said second bobbin is covered from the outside by base portions and side legs of said first core and second core.
3. The coil device as set forth in claim 1 , wherein;
a cross-section of middle legs of said ferrite core has an elliptical shape, and
a major axis direction of this elliptical shape corresponds to said reference direction.
4. The coil device as set forth in claim 2 , wherein;
a cross-section of middle legs of said ferrite core has an elliptical shape, and
a major axis direction of this elliptical shape corresponds to said reference direction.
5. The coil device as set forth in claim 1 , wherein;
the winding center of said primary coil and the winding center of said secondary coil respectively displace along said reference direction with respect to a core center of middle legs of said ferrite core along said reference direction.
6. The coil device as set forth in claim 2 , wherein;
the winding center of said primary coil and the winding center of said secondary coil respectively displace along said reference direction with respect to a core center of middle legs of said ferrite core along said reference direction.
7. The coil device as set forth in claim 3 , wherein;
the winding center of said primary coil and the winding center of said secondary coil respectively displace along said reference direction with respect to a core center of middle legs of said ferrite core along said reference direction.
8. The coil device as set forth in claim 5 , wherein;
the winding center of said primary coil and the winding center of said secondary coil respectively displace along said reference direction with respect to a core center of middle legs of said ferrite core along said reference direction.
9. The coil device as set forth in claim 1 , wherein;
said first bobbin and second bobbin are assembled so that a first through hole of said first hollow cylinder is connected with a second through hole of said second hollow cylinder, and so that a top of said first hollow cylinder fits into a concave which is formed at the bottom of said second bobbin.