KY Converters and Their Improvements

KY converters are interesting DC/DC converter concepts. In this paper the basic posi-tive step-up converter with limited voltage transformation ratio, two types of the neg-ative output voltage step-up converter, the negative output step-up down converter, and two types of the positive output step-up-down converter based on the KY concept are treated. The disadvantage of all these converters is a recharging current peak at all switching periods leading to stress of the components and an additional elec-tro-magnetic compatibility problem. Two methods to improve the converters are pre-sented. First an included limiting resistor reduces the spike of the recharging pulse, and second a small inductor is placed in the recharging loop making a resonant charg-ing possible, that improves the efficiency. The function of the basic converters is ex-plained and the two improvements are included. The considerations are proved by simulations and measurements of a small converter laboratory design are shown.