Low-power transformer for printed circuit boards

A planar transformer for printed circuit boards, comprising:

• a) a primary bobbin structure;
• b) a secondary bobbin structure;
• and
• c) a core extendable through a central opening in each of said bobbin structures;
• d) said primary bobbin structure having a body surrounding said opening, a recess formed in said body around said opening, a primary bobbin supported by said body, primary and secondary connection pins for mounting said primary bobbin structure on a circuit board, and a slot;
• e) said secondary bobbin structure having a secondary bobbin surrounding said opening of said secondary bobbin structure and being shaped such that said secondary bobbin structure may be lockingly inserted into said recess so as to be, contained therein, and a hooked flange;
• wherein said secondary bobbin, when said secondary bobbin structure is inserted into said recess, is substantially coextensive with, and substantially parallel and adjacent to, said primary bobbin;
• and
• f) one or more primary and one or more secondary windings respectively wound about said primary and secondary bobbins;
• wherein said hooked flange lockingly engages said primary bobbin structure through said slot when said secondary bobbin structure is fully inserted into said recess.