Patent ID: 6262897
Filing Date: 2001-07-17
Classification: H02M,Y02B

Abstract:
A switching power supply circuit comprising:switching means including a switching element operable at a switching frequency for intermittently outputting an inputted DC input voltage;an insulating converter transformer for transmitting the output of the switching means to a secondary side;a primary side voltage resonant circuit coupled to the switching means to operate the switching means as a voltage resonant type;a secondary side resonant circuit constituted by a combination of a secondary side parallel resonant circuit formed of a secondary side parallel resonant capacitor connected in parallel with a secondary winding of the insulating converter transformer, and a secondary side series resonant circuit formed of a secondary side series resonant capacitor connected in series with the secondary winding of the insulating converter transformer;DC output voltage generation means for rectifying an AC voltage obtained from the secondary winding of the insulating converter transformer to produce a secondary side DC output voltage; andconstant voltage control means for changing the switching frequency of the switching element in accordance with the secondary side DC output voltage.