Low Power Multiple Output DC Supply - Part II: Crossover Voltage Control in Multiple Output DC Supply

The paper proposes a new topology for multiple outputs DC supplies allowing for implementation of commercial low power AC/DC converters. A special attention is paid to supplying mixed analogue/digital circuits that give rise to permissive voltage deviations when discontinuous load currents are applied. To avoid this problem, the paper is particularly concerned with the back-end requirements of the power supply stage generally generating two system voltages, i.e. the bipolar voltage (plusmn12 V) and the unipolar voltage (+5 V), the latter supplying digital circuits. Here, the main concern is to ensure efficient output voltages ranging within set tolerances of plusmn5 % and plusmn2 %. This requirement is to be satisfied even in the case of short cutouts of net voltage at no system functionality minimization. The described back-end power stage topology consisting of two buck converters generating three voltages controlled with only one secondary side PWM controller has proven to be appropriate for the achievement of this target. With an adequate crossover control of output voltages the component and manufacture costs are kept on the low level. Experimental results confirm the minimization of output voltages dependence on output currents discontinuity. Moreover, voltage ratings as well as the size of electrolytic capacitor providing back-up energy are reduced, too