DC voltage converting circuit

摘要

Control is carried out in such a manner that a transformer 10 constituting a DC voltage converting circuit 15 stores energy while a switching element 11 provided on the primary side of the transformer 10 is set in an ON state, and the transformer 10 outputs the energy while the switching element 11 is set in an OFF state, and furthermore, the switching element 11 is turned ON when the energy is completely output from a secondary winding 10s. For this purpose, a duration from a time that a secondary current I2 of the transformer 10 reaches zero to a time that a primary current Ip of the transformer 10 is started to flow is detected, and a switching frequency is changed by control means 16 in order to shorten the duration.