Power supply device, composite electronic component, and board having composite electronic component mounted thereon

A power supplying device may include: a constant-voltage supplying unit rectifying and smoothing input voltage to supply constant voltage; a transformer connected to an output stage of the constant-voltage supplying unit; a control unit connected to a primary winding of the transformer so as to control current flowing through the primary winding of the transformer; a first terminal connected to one terminal of the primary winding of the transformer; a snubber composite having a first end surface in contact with the first terminal to reduce surge voltages occurring in the primary winding of the transformer; and a second terminal connected to the other terminal of the primary winding of the transformer and being in contact with a second end surface of the snubber composite.