Insulating type DC / DC converter, primary side controller, synchronous rectifier controller, power supply device using the same, power adapter and electronic equipment

摘要

PROBLEM TO BE SOLVED: To achieve high efficiency while ensuring the stability of a system.SOLUTION: A synchronous rectification controller 300 switching a synchronous rectification transistor M2 is provided. To a VCC terminal, a DC voltage Vobtained from an output voltage Vof a DC-DC converter 200 is supplied. A driver 306 switches the synchronous rectification transistor M2 according to a pulse signal S1 generated by a pulse generator 304. A voltage source 320 includes a first transistor M31 of an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) provided between a VCC terminal and a power supply line 308; a gate voltage generation circuit 322 supplying a lower gate voltage Vthan a predetermined voltage to a gate of the first transistor M31. A second transistor M32 of a P-channel MOSFET is provided between the VCC terminal and the power supply line 308 and is ON-OFF controlled by a controller 330.SELECTED DRAWING: Figure 3