The step-up converters are very similar to the dc-dc converters of series “C”, except that the step-up converters sense the voltage across the load which is the total of the battery voltage and the voltage added by the step-up converter. The step-up converter can not reduce the voltage being applied to its input. Therefore, the load should be specified for the maximum battery voltage.
For output voltage stabilization The output voltage of an e.g. battery charger with parallel connected battery varies substantially with the charging condition of the battery. For many applications, however, the load circuit requires a better stabilized voltage. Frequently used methods for reducing the voltage variation are e.g. “voltage dropping diodes”. A more economical solution is given by switch mode step-up converters. These are dc-dc converters supplied from the battery with the output connected in series to the battery. Due to the circuit configuration, the output of a step-up converter is not isolated from the input supply (battery).