INSULATED SYNCHRONOUS RECTIFICATION DC/DC CONVERTER AND ITS FEEDBACK CIRCUIT, ITS SYNCHRONOUS RECTIFICATION CONTROLLER, A POWER SUPPLY DEVICE USING THE SAME, POWER SUPPLY ADAPTER AND ELECTRONIC APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a DC/DC converter in which secondary side abnormality can be detected, and the circuitry can be protected upon occurrence of an abnormality.SOLUTION: A feedback IC400 is arranged on the secondary side of a DC/DC converter 200, and connected with the input side of a photocoupler 204. An error amplifier 410 amplifies the error of a voltage detection signal Vdepending on the output voltage Vof the DC/DC converter 200 and its target voltage V, and draws a current Idepending on the error from the input side of the photocoupler 204 via a PC terminal. When detecting an abnormality on the secondary side of the DC/DC converter 200, an abnormality detection circuit 420 asserts an abnormality detection signal S4. A protection circuit 420 is connected with the PC terminal, and when the abnormality detection signal S4 is asserted, feedback by the error amplifier 410 is invalidated, the protection circuit 420 acts on the photocoupler 204 for feedback via the PC terminal, so as to reduce the on time of a switching transistor M1.SELECTED DRAWING: Figure 2