Abstract: Provided is a transformer having resonant inductance, the transformer including a core that includes a first leg formed in one side thereof, a second leg which is formed in the other side thereof so as to be electromagnetically coupled to the first leg, and a third leg which is formed between the first and second legs so as to be electromagnetically coupled to the first and second legs; a primary winding that is wound around one side of the third leg; a secondary winding that is wound around the other side of the third leg so as to induce power through electromagnetic induction with the primary winding; and a resonant inductance winding that is wound around the outside of the core so as not to be magnetically induced by magnetic fluxes generated from the primary and secondary windings.

Abstract: There is provided a variable switching frequency type power supply that can achieve high efficiency by fixing a switching duty cycle to 50% and varying switching frequency. A variable switching frequency type power supply according to an aspect of the invention may include: a switching unit switching input power; a transformation unit converting a voltage level of the power switched by the switching unit into a predetermined voltage level; a rectification unit rectifying the power converted by the transformation unit; and a control unit fixing a switching duty cycle of the switching unit to a predetermined switching duty cycle, and varying switching frequency of the switching unit according to a voltage level of output power.

Abstract: A phase shift full bridge converter with a reduced current stress includes: a switching unit that switches an input voltage; a transformer that includes a first capacitor serially connected to, and having a primary side and a secondary side; an auxiliary circuit unit that includes a first switch, a second switch, and a second capacitor, which are connected in parallel to the secondary side of the transformer; and a rectification unit that is connected to the auxiliary circuit unit, with an output inductor being removed.

Abstract: In accordance with the present invention, the switching power supply device using a current sharing transformer includes an inverter switching unit for switching an input voltage; a share inductor for classification connected to the inverter switching unit for distributing a current applied by the inverter switching unit; first and second transformers of which each primary side connected to the share inductor for classification is connected in parallel to each other; and a rectifying unit connected to secondary sides of the first and second transformers.

Abstract: There is provided a bridgeless power factor correction circuit that corrects a power factor by complementarily switching two switches according to phase of input power without using rectifier bridge diodes. A bridgeless power factor correction circuit according to an aspect of the invention may include: a switching unit having a plurality of switches and alternately switching input AC power; a stabilizing unit rectifying and smoothing the power switched by the switching unit; and a control unit controlling an alternate switching operation between the plurality of switches according to phases of the input power.

Abstract: There is provided a transformer improved in leakage inductance including: a core having first, second and third legs electromagnetically coupled to one another; a primary winding formed of a conductor having one end and another end receiving power from the outside and dividedly wound around the first, second and third legs; and a secondary winding wound around at least one of the first, second and third legs and receiving induced power by electromagnetic induction with the primary winding.