Constant voltage output control method and constant voltage output control device for switching power supply circuit

摘要

The present invention provides a constant voltage output control method and a constant voltage output control device for a switching power supply circuit that allow accurate execution of a constant voltage control of an output voltage, even if there is variation in a utilized circuit element or an integrated circuit. A set voltage V_2aset is obtained based on equation (1),V_2ASET=NP÷NS×V_2BSET  (1);where, V_2bset represents an output voltage of a secondary output winding that is subject to the constant voltage control, Np represents a number of turns of a primary winding, and Ns represents a number of turns of the secondary output winding; and the set voltage V_2aset is compared with a flyback voltage V_2a of the primary winding.