An alternative method for controlling two-output DC-to-DC converters using saturable core inductor

An alternative to the use of a conventional magnetic amplifier in the control of a second output in buck derived DC-to-DC converters is presented. Power semiconductors in the active region are avoided and the second output does not present additional phase shift due to the rest of the core system. These two advantages increase converter efficiency and transient response. The method is based on a double modulation of the switching frequency and duty cycle in the power switch. The switching frequency modulation is, however, relatively small. Keeping the switching frequency almost constant versus input voltage variations and changing slightly versus load variations.<>