Patent attributes
A synchronized rectification circuit and a switching power supply device having little power loss with respect to a wide range of input voltages and having a high efficiency, comprising first and second switch elements, first and second capacitors connected with each other capable to equalize held voltages thereof in response to sift of an input AC voltage to intermediate voltage (for example 0V), a first driving circuit for turning on a switch element according to the held voltage changed in response to shift the input AC voltage to 0V from a negative polarity voltage and turning off the switch element earlier than a time where the input voltage shifts to the negative polarity voltage from 0V, and a second driving circuit to drive a switch element in the same way but in reverse phase.
