Transformer for switching power supply and switching power supply provided with the same

摘要

PROBLEM TO BE SOLVED: To provide a transformer capable of reducing a fluctuation of a control circuit voltage Variable capacitance circuit relative to an output load current Iout, to a degree at least equivalent to the case of providing a resistor or higher, without the provision of a resistor between an auxiliary coil D and a rectifier diode 5.SOLUTION: A transformer structure has a primary coil layer composed of a primary coil at least near an auxiliary coil layer composed of an auxiliary coil, and disposed in a coil winding radius direction wound around the outer circumference of a bobbin, in a manner not to be overlapped with the auxiliary coil layer, so as to reduce magnetic coupling between the auxiliary coil and the primary coil.