| 摘要 |
PROBLEM TO BE SOLVED: To improve the efficiency of a synchronized rectification DC/DC converter, by making nearly zero the drive loss in its synchronized rectification circuit in the case of its lightly loaded state, its unloaded state or the like. SOLUTION: In a synchronized rectification DC/DC converter, when it is lightly loaded or unloaded by a load 16 as making resultly a sensed voltage VA of a current sensing resistor 22 smaller than a reference voltage VR2 of a reference power supply 23, bringing a MOSFET 4 for synchronized rectifications into OFF-state by the output signal of a comparison circuit 26, a rectifying operation is performed by a parasitic diode 4a in the MOSFET 4 for synchronized rectifications. When the load 16 becomes its ordinary state to make the sensed voltage VA of the current sensing resistor 22 not smaller than the reference voltage VR2 of the reference power supply 23, performing the ON/OFF control of the MOSFET 4 for synchronized rectifications by the output signal of the comparison circuit 26, a rectifying operation is performed. Thereby, since the MOSFET 4 for synchronized rectifications is unoperated in the case of the lightly loaded state of the DC/DC converter, its unloaded state, or the like, the driving loss in its synchronized rectification circuit is made nearly zero to make improvable its efficiency.
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