Pulsewidth modulation derived through control of flux distribution in dual-core transformer

A novel method of achieving pulsewidth regulation through control of the distribution of flux variations in a dual-core transformer is described. Transfer of drive power or load power is accomplished by utilizing a principal core during a portion of each half-cycle of applied ac voltage. The flux excursion necessary to generate the required counter EMF during the remainder of each input half-cycle takes place in a second or "control core" by which means the duty cycle is varied. Applicability of the scheme to dc-to-dc converters is discussed. Although direct sensing of the output is employed, the negative feedback loop is closed by magnetic coupling to the transformer so that complete input-to-output isolation is obtained. Integrated circuitry provides the required variable time delay in the feedback network.