Switching power supply apparatus

摘要

A switching power supply apparatus comprises a transformer having a primary winding, a secondary winding, and a feedback winding; a switching element connected in series with the primary winding, a controlling circuit provided between a control terminal of the switching element and the feedback winding; a rectifying circuit connected to the secondary winding; and a protecting circuit adapted to stop the switching operation of the switching element in correspondence to an abnormality in voltage produced in the feedback winding and having the opposite polarity to the voltage produced in the feedback winding.