fig1 shows an electronic device 60 of an exemplary embodiment of the present invention . the electronic device 60 , such as an inverter , a converter , and the like , comprises a circuit part like a circuit board 20 and an electronic component like a transformer 10 coupled to the circuit board 20 . the transformer 10 comprises a base 110 mounted on the circuit board 20 , a bobbin assembly 120 , a core module 130 , and two positioning means like two positioning posts 140 . the base 110 comprises a first end portion 110 a and a second end portion 110 b opposite to the first end portion 110 a . both of them are able to electrically connectable to the circuit board 20 . the bobbin assembly 120 is disposed between the first end portion 110 a and the second end portion 110 b . the bobbin assembly 120 comprises a first bobbin 121 having a primary winding wound thereon , and a second bobbin 122 having a secondary winding wound thereon . the second bobbin 122 is connected to the first bobbin 121 . the first bobbin 121 is adjacent to the first end portion 110 a , while the second bobbin 122 is adjacent to the second end portion 110 b . the positioning posts 140 are disposed on opposite ends of the first end portion 110 a . the first bobbin 121 is disposed collinear with the second bobbin 122 . the bobbin assembly 120 defines a hollow portion 123 extending therethrough . the core module 130 has a first core portion 130 a and an opposite second core portion 130 b , both of which are inserted in the hollow portion 123 from opposite ends of the bobbin assembly 120 to form a closed magnetic loop . each of the core portions 130 a and 130 b has an e - shaped cross - section . the circuit board 20 comprises two receiving holes 210 corresponding to the positioning posts 140 . when the transformer 10 is coupled to the circuit board 20 , the positioning posts 140 are received in the receiving holes 210 . thereby the transformer 10 is accurately positioned on the circuit board 20 , facilitating soldering in a reflow oven . in another exemplary embodiment of the invention , referring to fig2 , the positioning posts 140 are disposed on the second end portion 110 b of the base 110 . in a further exemplary embodiment of the invention , referring to fig3 , one of the positioning posts 140 is disposed on the first end portion 110 a of the base 110 , while the other is disposed on the second end portion 110 b of the base 110 . in a still further exemplary embodiment of the invention , referring to fig4 , a transformer 30 is shown . the transformer 30 comprises a base 310 having a first end portion 310 a and a second end portion 310 b opposite to the first end portion 310 a , a bobbin assembly 320 having a first bobbin 321 and a second bobbin 322 parallel to the first bobbin 321 , and two positioning posts 340 . the bobbin assembly 320 is disposed between the first end portion 310 a and the second end portion 310 b . the first bobbin 321 defines a first hollow portion 324 , while the second bobbin 322 defines a second hollow portion 323 . the transformer 30 further comprises a core module 330 having a first core portion 330 a and a second core portion 330 b received in the hollow portions 324 and 323 respectively . each of the core portions 330 a and 330 b has a u - shaped cross - section . the positioning posts 340 have a similar positioning means to that of the aforementioned exemplary embodiments of the present invention . when the transformer 30 is coupled to the circuit board 20 of fig1 , the positioning posts 340 are received in the receiving holes 210 . as a result , the transformer 30 is accurately positioned on the circuit board 20 , facilitating soldering in the reflow oven . while exemplary embodiments have been described above , it should be understood that they have been presented by way of example only and not by way of limitation . thus the breadth and scope of the present invention should not be limited by the above - described exemplary embodiments , but should be defined only in accordance with the following claims and their equivalents .