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.

Abstract: In the DC/DC converter, a switching part has first and second switches serially connected from a power supply to a ground. The first and second switches switch on/off in response to first and second switching signals having a fixed frequency. The first switching signal has a phase level that does not overlap a corresponding phase level of the second switching signal. A transformer transforms a voltage applied to a first winding into a second winding in response to switching operation of the switching part, and resonates by an inductor and a capacitor of the first winding. Also, a rectifier includes a rectifying diode for rectifying the voltage from the transformer into a direct voltage. A feedback circuit detects the voltage outputted via the rectifier. Additionally, a controller controls pulse width of the first and second switching signals in a PWM mode according to the voltage detected by the feedback circuit.