Drive circuit for switching power supply

摘要

A drive circuit for a switching power supply includes a driving element (11, 12) for generating a drive signal (SD), and a transformer (15) for outputting the drive signal input via a capacitive element to a primary winding (15a) thereof (14), to a main switching element (21) from a secondary winding (15b) thereof. The drive circuit (3) is constructed such that breakage of the main switching element (21) can be prevented while permitting an increase in the range of switching control. The drive circuit (3) is characterized by comprising an inductive element (16) having an inductance value smaller than at least a value of an excitation inductance of the primary winding (15a) and allowing series resonance to be produced between the capacitive element (14) and the inductive element (16).