Current mode control for DC converters operating over 50% duty cycle

摘要

In a capacitively coupled DC-to-DC converter employing a pair of switching elements alternately rendered conductive, instabilities arising from current mode control are compensated for by detecting and controlling the amount of charge transferred by each switching element to a respective output capacitor associated therewith rather than the conduction period of each switching element. Converter instabilities arising from switching element duty cycles in excess of 50% are compensated for by integrating the sensed inductor current which represents the average inductor output current rather than its instantaneous value. An integrating network is discharged to 0 at the end of each cycle in resetting the sensed inductor current to 0 to prevent converter runaway when the switching element duty cycle exceeds 50%. This invention is applicable for all types of DC converters operating with a duty cycle greater than 50%.